Category Archives: High Energy Astrophysical Phenomena

Early-Time Ultraviolet and Optical Hubble Space Telescope Spectroscopy of the Type II Supernova 2022wsp [HEAP]

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http://arxiv.org/abs/2304.06147


We report early-time ultraviolet (UV) and optical spectroscopy of the young, nearby Type II supernova (SN) 2022wsp obtained by the Hubble Space Telescope (HST)/STIS at about 10 and 20 days after the explosion. The SN 2022wsp UV spectra are compared to those of other well-observed Type II/IIP SNe, including the recently studied Type IIP SN 2021yja. Both SNe exhibit rapid cooling and similar evolution during early phases, indicating a common behavior among SNe II. Radiative-transfer modeling of the spectra of SN 2022wsp with the TARDIS code indicates a steep radial density profile in the outer layer of the ejecta, a supersolar metallicity, and a relatively high total extinction of E(B-V) = 0.35 mag. The early-time evolution of the photospheric velocity and temperature derived from the modeling agree with the behavior observed from other previously studied cases. The strong suppression of hydrogen Balmer lines in the spectra suggests interaction with a pre-existing circumstellar environment could be occurring at early times. In the SN 2022wsp spectra, the absorption component of the Mg II P Cygni profile displays a double-trough feature on day +10 that disappears by day +20. The shape is well reproduced by the model without fine-tuning the parameters, suggesting that the secondary blueward dip is a metal transition that originates in the SN ejecta.

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S. Vasylyev, C. Vogl, Y. Yang, et. al.
Fri, 14 Apr 23
59/64

Comments: Submitted to ApJ Letters on 4/11/2023

CAvity DEtection Tool (CADET): Pipeline for automatic detection of X-ray cavities in hot galactic and cluster atmospheres [HEAP]

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http://arxiv.org/abs/2304.05457


The study of jet-inflated X-ray cavities provides a powerful insight into the energetics of hot galactic atmospheres and radio-mechanical AGN feedback. By estimating the volumes of X-ray cavities, the total energy and thus also the corresponding mechanical jet power required for their inflation can be derived. Properly estimating their total extent is, however, non-trivial, prone to biases, nearly impossible for poor-quality data, and so far has been done manually by scientists. We present a novel and automated machine-learning pipeline called Cavity Detection Tool (CADET), developed to detect and estimate the sizes of X-ray cavities from raw Chandra images. The pipeline consists of a convolutional neural network trained for producing pixel-wise cavity predictions and a DBSCAN clustering algorithm, which decomposes the predictions into individual cavities. The convolutional network was trained using mock observations of early-type galaxies simulated to resemble real noisy Chandra-like images. The network’s performance has been tested on simulated data obtaining an average cavity volume error of 14 % at an 89 % true-positive rate. For simulated images without any X-ray cavities inserted, we obtain a 5 % false-positive rate. When applied to real Chandra images, the pipeline recovered 91 out of 100 previously known X-ray cavities in nearby early-type galaxies and all 14 cavities in chosen galaxy clusters. Besides that, the CADET pipeline discovered 8 new cavity pairs in atmospheres of early-type galaxies and galaxy clusters (IC4765, NGC533, NGC2300, NGC3091, NGC4073, NGC4125, NGC4472, NGC5129) and a number of potential cavity candidates.

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T. Plšek, N. Werner, M. Topinka, et. al.
Thu, 13 Apr 23
2/59

Comments: N/A

General Physical Properties of Gamma-Ray-emitting Radio Galaxies [HEAP]

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http://arxiv.org/abs/2304.05551


We study the radio galaxies with known redshift detected by the Fermi satellite after 10 years of data (4FGL-DR2). We use a one-zone leptonic model to fit the quasi-simultaneous multiwavelength data of these radio galaxies and study the distributions of the derived physical parameter as a function of black hole mass and accretion disk luminosity. The main results are as follows. (1) We find that the jet kinetic power of most radio galaxies can be explained by the hybrid jet model based on ADAFs surrounding Kerr black holes. (2) After excluding the redshift, there is a significant correlation between the radiation jet power and the accretion disk luminosity, while the jet kinetic power is weakly correlated with the accretion disk luminosity. (3) We also find a significant correlation between inverse Compton luminosity and synchrotron luminosity. The slope of the correlation for radio galaxies is consistent with the synchrotron self-Compton (SSC) process. The result may suggest that the high-energy component of radio galaxies is dominated by the SSC process.

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Y. Chen, Q. Gu, J. Fan, et. al.
Thu, 13 Apr 23
3/59

Comments: 9 pages,7 figures, accept for publication in ApJS

Astrophysical cloaking of a naked singularity [HEAP]

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http://arxiv.org/abs/2304.05932


A massive naked singularity would be cloaked by accreted matter, and thus may appear to a distant observer as an opaque \mbox{(quasi-)}spherical surface of a fluid, not unlike that of a star or planet. We present here analytical solutions for levitating atmospheres around a wide class of spherically symmetric naked singularities. Such an atmosphere can be constructed in every spacetime which possesses a zero-gravity radius and which is a solution of a (modified-)gravity theory possessing the usual conservation laws for matter. Its density peaks at the zero-gravity radius and the atmospheric fluid is supported against infall onto the singularity by gravity alone. In an astrophysical context, an opaque atmosphere would be formed in a very short time by accretion of ambient matter onto the singularity — in a millisecond for an X-ray binary, in a thousand seconds for a singularity traversing interstellar space, and a thousand years for a singularity that is the central engine of an AGN.

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R. Vieira and W. Kluźniak
Thu, 13 Apr 23
13/59

Comments: 9 pages, 4 figures. Submitted to MNRAS

Vertical wind structure in an X-ray binary revealed by a precessing accretion disk [HEAP]

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http://arxiv.org/abs/2304.05490


The accretion of matter onto black holes and neutron stars often leads to the launching of outflows that can greatly affect the environments surrounding the compact object. In supermassive black holes, these outflows can even be powerful enough to dictate the evolution of the entire host galaxy, and yet, to date, we do not understand how these so-called accretion disk winds are launched – whether by radiation pressure, magnetic forces, thermal irradiation, or a combination thereof. An important means of studying disk winds produced near the central compact object is through X-ray absorption line spectroscopy, which allows us to probe outflow properties along a single line of sight, but usually provides little information about the global 3D disk wind structure that is vital for understanding the launching mechanism and total wind energy budget. Here, we study Hercules X-1, a unique, nearly edge-on X-ray binary with a warped accretion disk precessing with a period of about 35 days. This disk precession results in changing sightlines towards the neutron star, through the ionized outflow. We perform time-resolved X-ray spectroscopy over the precession phase and detect a strong decrease in the wind column density by three orders of magnitude as our sightline progressively samples the wind at greater heights above the accretion disk. The wind becomes clumpier as it rises upwards and expands away from the neutron star. Modelling the warped disk shape, we create a 2D map of wind properties. This unique measurement of the vertical structure of an accretion disk wind allows direct comparisons to 3D global simulations to reveal the outflow launching mechanism.

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P. Kosec, E. Kara, A. Fabian, et. al.
Thu, 13 Apr 23
15/59

Comments: Published in Nature Astronomy on April 10, available at this https URL

The neutron star to black hole mass gap in the frame of the jittering jets explosion mechanism (JJEM) [HEAP]

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http://arxiv.org/abs/2304.05705


I build a toy model in the frame of the jittering jets explosion mechanism (JJEM) of core collapse supernovae (CCSNe) that incorporates both the stochastically varying angular momentum component of the material that the newly born neutron star (NS) accretes and the constant angular momentum component and show that the JJEM can account for the ~2.5-5Mo mass gap between NSs and black holes (BHs). The random component of the angular momentum results from pre-collapse core convection fluctuations that are amplified by post-collapse instabilities. The fixed angular momentum component results from pre-collapse core rotation. For slowly rotating pre-collapse cores the stochastic angular momentum fluctuations form intermittent accretion disks (or belts) around the NS with varying angular momentum axes in all directions. The intermittent accretion disk/belt launches jets in all directions that expel the core material in all directions early on, hence leaving a NS remnant. Rapidly rotating pre-collapse cores form an accretion disk with angular momentum axis that is about the same as the pre-collapse core rotation. The NS launches jets along this axis and hence the jets avoid the equatorial plane region. In-flowing core material continues to feed the central object from the equatorial plane increasing the NS mass to form a BH. The narrow transition from slow to rapid pre-collapse core rotation, i.e., from an efficient to inefficient jet feedback mechanism, accounts for the sparsely populated mass gap.

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N. Soker
Thu, 13 Apr 23
21/59

Comments: Will be submitted in two days to allow for comments

Observing Supernova Neutrino Light Curves with Super-Kamiokande. IV. Development of SPECIAL BLEND: a New Public Analysis Code for Supernova Neutrinos [HEAP]

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http://arxiv.org/abs/2304.05437


Supernova neutrinos are invaluable signals that offer information about the interior of supernovae. Because a nearby supernova can occur at any time, preparing for future supernova neutrino observation is an urgent task. For the prompt analysis of supernova neutrinos, we have developed a new analysis code, “Supernova Parameter Estimation Code based on Insight on Analytic Late-time Burst Light curve at Earth Neutrino Detector (SPECIAL BLEND)”. This code estimates the parameters of supernova based on an analytic model of supernova neutrinos from the proto-neutron star cooling phase. For easy availability to the community, this code is public and easily runs on web environments. SPECIAL BLEND can estimate the parameters better than the analysis pipeline we developed in the previous paper. By using SPECIAL BLEND, we can estimate the supernova parameters within $10\%$ precision up to $\sim 20\,{\rm kpc}$ and $\sim 60\,{\rm kpc}$ (Large Magellanic Cloud contained) with Super Kamiokande and Hyper Kamiokande, respectively.

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A. Harada, Y. Suwa, M. Harada, et. al.
Thu, 13 Apr 23
34/59

Comments: 15 pages, 6 figures; submitted to ApJ; SPECIAL BLEND is available at this https URL

Diversity of early kilonova with the realistic opacities of highly ionized heavy elements [HEAP]

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http://arxiv.org/abs/2304.05810


We investigate the early (t < 1 day) kilonova from the neutron star merger by deriving atomic opacities for all the elements from La to Ra (Z = 57 – 88) ionized to the states V – XI. The opacities at high temperatures for the elements with open f-shells (e.g., lanthanides) are exceptionally high, reaching kappa_{exp} ~ 10^4 cm2/g at lambda < 1000 A at T ~ 70,000 K, whereas, the opacities at the same temperature and wavelengths for the elements with the open d-, p-, and s-shells reach kappa_{exp} ~ 1 cm2/g, 0.1 cm2/g, and 0.01 cm2/g, respectively. Using the new opacity dataset, we derive the early kilonovae for various compositions and density structures expected for neutron star merger ejecta. The bolometric luminosity for the lanthanide-rich ejecta shows distinct signatures and is fainter than that for the lanthanide-free ejecta. The early luminosity is suppressed by the presence of a thin outer layer, agreeing with the results of Kasen et al. (2017) and Banerjee et al. (2020). The early brightness in Swift UVOT filters and in the optical g-, r-, i-, z-filters for a source at 100 Mpc are ~ 22 – 20 mag and ~ 21 – 19 mag, respectively, at t ~ 0.1 days. Such kilonovae are ideal targets for the upcoming UV satellites, such as ULTRASAT, UVEX, and DORADO, and the upcoming surveys, e.g., Vera Rubin Observatory. We suggest the gray opacities to reproduce the bolometric light curves with and without lanthanides are ~ 1 – 20 cm2/g and ~ 0.8 – 1 cm2/g.

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S. Banerjee, M. Tanaka, D. Kato, et. al.
Thu, 13 Apr 23
37/59

Comments: 37 pages, 16 figures, submitted to ApJ, comments are welcome

The luminosity functions of kilonovae from binary neutron star mergers under different equation of states [HEAP]

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http://arxiv.org/abs/2304.05779


Kilonovae produced by mergers of binary neutron stars (BNSs) are important transient events to be detected by time domain surveys with the alerts from the ground-based gravitational wave detectors. The observational properties of these kilonovae depend on the physical processes involved in the merging processes and the equation of state (EOS) of neutron stars (NSs). In this paper, we investigate the dependence of kilonova luminosities on the parameters of BNS mergers, and estimate the distribution functions of kilonova peak luminosities (KLFs) at the u-, g-, r-, i-, y-, and z-bands as well as its dependence on the NS EOS, by adopting a comprehensive semi-analytical model for kilonovae (calibrated by the observations of GW170817), a population synthesis model for the cosmic BNSs, and the ejecta properties of BNS mergers predicted by numerical simulations. We find that the kilonova light curves depend on both the BNS properties and the NS EOS, and the KLFs at the considered bands are bimodal with the bright components mostly contributed by BNS mergers with total mass $\lesssim 3.2M_\odot$/$2.8M_\odot$ and fainter components mostly contributed by BNS mergers with total mass $\gtrsim 3.2M_\odot$/$2.8M_\odot$ by assuming a stiff/soft (DD2/SLy) EOS. The emission of the kilonovae in the KLF bright components are mostly due to the radiation from the wind ejecta by the remnant disks of BNS mergers, while the emission of the kilonovae in the KLF faint components are mostly due to the radiation from the dynamical ejecta by the BNS mergers.

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C. Zhao, Y. Lu, Q. Chu, et. al.
Thu, 13 Apr 23
46/59

Comments: 28 pages, 16 figures, MNRAS accepted

Modelling Neutron-Star Ocean Dynamics [HEAP]

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http://arxiv.org/abs/2304.05413


We re-visit the calculation of mode oscillations in the ocean of a rotating neutron star, which may be excited during thermonuclear X-ray bursts. Our present theoretical understanding of ocean modes relies heavily on the traditional approximation, commonly employed in geophysics. The approximation elegantly decouples the radial and angular sectors of the perturbation problem by neglecting the vertical contribution from the Coriolis force. However, as the implicit assumptions underlying it are not as well understood as they ought to be, we examine the traditional approximation and discuss the associated mode solutions. The results demonstrate that, while the approximation may be appropriate in certain contexts, it may not be accurate for rapidly rotating neutron stars. In addition, using the shallow-water approximation, we show analytically how the solutions that resemble r-modes change their nature in neutron-star oceans to behave like gravity waves. We also outline a simple prescription for lifting Newtonian results in a shallow ocean to general relativity, making the result more realistic.

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F. Gittins, T. Celora, A. Beri, et. al.
Thu, 13 Apr 23
47/59

Comments: 16 pages, 2 figures

High-Resolution Spectroscopy of X-ray Binaries [HEAP]

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http://arxiv.org/abs/2304.05412


X-ray binaries, as bright local sources with short variability timescales for a wide range of accretion processes, represent ideal targets for high-resolution X-ray spectroscopy. In this chapter, we present a high-resolution X-ray spectral perspective on X-ray binaries, focusing on black holes and neutron stars. The majority of the chapter is devoted to observational and theoretical signatures of mass ejection via accretion disk winds: we discuss their appearance (including an overview of photoionization and thermodynamic processes that determine their visibility in X-ray spectra) and their life cycles (including efforts to constrain their time-dependent mass loss rates), and we provide a broad overview of the primary accretion disk wind driving mechanisms that have been considered in the literature: (1) radiation pressure, where radiation accelerates a wind by scattering off electrons or atoms in the disk or its atmosphere; (2) thermal driving, where Compton heating of the outer accretion disk causes gas thermal velocities to exceed the local escape speed; and (3) magnetohydrodynamic processes, where gas may be ejected from the disk via magnetic pressure gradients or magnetocentrifugal effects. We then turn to spectroscopic constraints on the geometry of accreting systems, from relativistically blurred emission lines to dipping sources, clumpy, structured stellar winds, and baryonic jets. We conclude with discussions of measurements of the interstellar medium and the potential of next-generation high-resolution X-ray spectroscopy for X-ray binaries.

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J. Neilsen and N. Degenaar
Thu, 13 Apr 23
50/59

Comments: 58 pages, 12 figures. Invited review chapter for the book High-Resolution X-Ray Spectroscopy: Instrumentation, Data Analysis, and Science (Eds. C. Bambi and J. Jiang, Springer Singapore, expected in 2023)

The X-ray variation of M81* resolved by Chandra and NuSTAR [HEAP]

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http://arxiv.org/abs/2304.05577


Despite advances in our understanding of low luminosity active galactic nuclei (LLAGNs), the fundamental details about the mechanisms of radiation and flare/outburst in hot accretion flow are still largely missing. We have systematically analyzed the archival Chandra and NuSTAR X-ray data of the nearby LLAGN M81*, whose $L_{\rm bol}\sim 10^{-5} L_{\rm Edd}$. Through a detailed study of X-ray light curve and spectral properties, we find that the X-ray continuum emission of the power-law shape more likely originates from inverse Compton scattering within the hot accretion flow. In contrast to Sgr A*, flares are rare in M81*. Low-amplitude variation can only be observed in soft X-ray band (amplitude usually $\lesssim 2$). Several simple models are tested, including sinusoidal-like and quasi-periodical. Based on a comparison of the dramatic differences of flare properties among Sgr A*, M31* and M81*, we find that, when the differences in both the accretion rate and the black hole mass are considered, the flares in LLAGNs can be understood universally in a magneto-hydrodynamical model.

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S. Niu, F. Xie, Q. Wang, et. al.
Thu, 13 Apr 23
57/59

Comments: 11 pages, 8 figures, and 4 tables. Accepted to MNRAS

Future Constraints on Dark Matter with Gravitationally Lensed Fast Radio Bursts Detected by BURSTT [HEAP]

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http://arxiv.org/abs/2304.04990


Understanding dark matter is one of the most urgent questions in modern physics. A very interesting candidate is primordial black holes (PBHs; Carr2016). For the mass ranges of $< 10^{-16} M_{\odot}$ and $> 100 M_{\odot}$, PBHs have been ruled out. However, they are still poorly constrained in the mass ranges of $10^{-16} – 100 M_{\odot}$ (Belotsky et al. 2019). Fast radio bursts (FRBs) are millisecond flashes of radio light of unknown origin mostly from outside the Milky Way. Due to their short timescales, gravitationally lensed FRBs, which are yet to be detected, have been proposed as a useful probe for constraining the presence of PBHs in the mass window of $< 100M_{\odot}$ (Mu\~noz et al. 2016). Up to now, the most successful project in finding FRBs has been CHIME. Due to its large field of view (FoV), CHIME is detecting at least 600 FRBs since 2018. However, none of them is confirmed to be gravitationally lensed (Leung et al. 2022). Taiwan plans to build a new telescope, BURSTT dedicated to detecting FRBs. Its survey area will be 25 times greater than CHIME. BURSTT can localize all of these FRBs through very-long-baseline interferometry (VLBI). We estimate the probability to find gravitationally lensed FRBs, based on the scaled redshift distribution from the latest CHIME catalog and the lensing probability function from Mu\~noz et al. (2016). BURSTT-2048 can detect ~ 24 lensed FRBs out of ~ 1,700 FRBs per annum. With BURSTT’s ability to detect nanosecond FRBs, we can constrain PBHs to form a part of dark matter down to $10^{-4}M_{\odot}$.

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S. Ho, T. Hashimoto, T. Goto, et. al.
Wed, 12 Apr 23
9/45

Comments: Accepted for publication in ApJ. A summary video is available at this this https URL

Typical X-ray Outburst Light Curves of Aql X-1 [HEAP]

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http://arxiv.org/abs/2304.05280


We show that a typical X-ray outburst light curve of Aql X-1 can be reproduced by accretion onto the neutron star in the frame of the disc instability model without invoking partial accretion or propeller effect. The knee and the subsequent sharp decay in the X-ray light curve can be generated naturally by taking into account the weak dependence of the disc aspect ratio, $h/r$, on the disc mass-flow rate, $\dot{M}\mathrm{in}$, in the X-ray irradiation flux calculation. This $\dot{M}\mathrm{in}$ dependence of $h/r$ only slightly modifies the irradiation temperature profile along the hot disc in comparison to that obtained with constant $h/r$. Nevertheless, this small difference has a significant cumulative effect on the hot disc radius leading to a much faster decrease in the size of the hot disc, and thereby to a sharper decay in the X-ray outburst light curve. The same model also produces the long-term evolution of the source consistently with its observed outburst recurrence times and typical light curves of Aql X-1. Our results imply that the source accretes matter from the disc in the quiescent state as well. We also estimate that the dipole moment of the source $\mu \lesssim 2 \times 10^{26}$ G cm$^3$.

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&. Çoban and U. Ertan
Wed, 12 Apr 23
15/45

Comments: 5 pages, 3 figures, submitted to PASA

Applications of the gamma/hadron discriminator $LCm$ to realistic air shower array experiments [HEAP]

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http://arxiv.org/abs/2304.05348


In this article, it is shown that the $C_k$ and $LCm$ variables, recently introduced as an effective way to discriminate gamma and proton-induced showers in large wide-field gamma-ray observatories, can be generalised to be used in arrays of different detectors and variable fill factors. In particular, the $C_k$ profile discrimination capabilities are evaluated for scintillator and water Cherenkov detector arrays.

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R. Conceição, P. Costa, L. Gibilisco, et. al.
Wed, 12 Apr 23
23/45

Comments: N/A

Diffusive Shock Acceleration of Cosmic Rays — Quasi-thermal and Non-thermal Particle Distributions [HEAP]

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http://arxiv.org/abs/2304.05168


A well-known paradigm about the origin of Galactic cosmic rays (CRs) is that these high-energy particles are accelerated in the process of diffusive shock acceleration (DSA) at collisionless shocks (at least up to the so-called “knee”energy of $10^{15}$ eV). Knowing the details of injection of electrons, protons and heavier nuclei into the DSA, their initial and the resulting spectrum, is extremely important in many “practical” applications of the CR astrophysics, e.g. in modelling of the gamma or synchrotron radio emission of astrophysical sources. In this contribution I we will give an overview of the DSA theory and the results of observations and kinetic Particle-In-Cell (PIC) simulations that support the basic theoretical concepts. PIC simulations of quasi-parallel collisionless shocks show that thermal and supra-thermal proton distribution functions at the shock can be represented by a single quasi-thermal distribution – the $\kappa$-distribution that is commonly observed in out-of-equilibrium space plasmas. Farther downstream, index $\kappa$ increases and the low-energy spectrum tends to Maxwell distribution. On the other hand, higher-energy particles continue through the acceleration process and the non-thermal particle spectrum takes a characteristic power-law form predicted by the linear DSA theory. In the end, I will show what modification of the spectra is expected in the non-linear DSA, when CR back-reaction to the shock is taken into account.

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B. Arbutina
Wed, 12 Apr 23
29/45

Comments: 13 pages, 5 figures, 11th International Conference of the Balkan Physical Union (BPU11), 28 August – 1 September 2022, Belgrade, Serbia

Characterizing quasi-steady states of fast neutrino-flavor conversion by stability and conservation laws [HEAP]

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http://arxiv.org/abs/2304.05044


The question of what ingredients characterize the quasi-steady state of fast neutrino-flavor conversion (FFC) is one of the long-standing riddles in neutrino oscillation. Addressing this issue is necessary for accurate modeling of neutrino transport in core-collapse supernova and binary neutron star merger. Recent numerical simulations of FFC have shown, however, that the quasi-steady state is sensitively dependent on boundary conditions in space, and the physical reason for the dependence is not clear at present. In this study, we provide a physical interpretation of this issue based on arguments with stability and conservation laws. The stability can be determined by the disappearance of ELN(electron neutrino-lepton number)-XLN(heavy-leptonic one) angular crossings, and we also highlight two conserved quantities characterizing the quasi-steady state of FFC: (1) lepton number conservation along each neutrino trajectory and (2) conservation law associated with angular moments, depending on boundary conditions, for each flavor of neutrinos. We demonstrate that neutrino distributions in quasi-steady states can be determined in an analytic way regardless of boundary conditions, which are in good agreement with numerical simulations. This study represents a major step forward a unified picture determining asymptotic states of FFCs.

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M. Zaizen and H. Nagakura
Wed, 12 Apr 23
32/45

Comments: 10 pages, 5 figures, submitted to PRD

Catching a nova X-ray/UV flash in the visible? Early spectroscopy of the extremely slow Nova Velorum 2022 (Gaia22alz) [HEAP]

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http://arxiv.org/abs/2304.04306


We present early spectral observations of the very slow Galactic nova Gaia22alz, over its gradual rise to peak brightness that lasted 180 days. During the first 50 days, when the nova was only 3–4 magnitudes above its normal brightness, the spectra showed narrow (FWHM $\approx$ 400 km s$^{-1}$) emission lines of H Balmer, He I, He II, and C IV, but no P Cygni absorption. A few weeks later, the high-excitation He II and C IV lines disappeared, and P Cygni profiles of Balmer, He I, and eventually Fe II lines emerged, yielding a spectrum typical of classical novae before peak. We propose that the early spectra of Gaia22alz are produced in the white dwarf’s envelope or accretion disk, reprocessing X-ray and ultraviolet emission from the white dwarf after a dramatic increase in the rate of thermonuclear reactions, during a phase known as the “early X-ray/UV flash”. If true, this would be one of the rare times that the optical signature of the early X-ray/UV flash has been detected. While this phase might last only a few hours in other novae and thus be easily missed, it was possible to detect in Gaia22alz due to its very slow and gradual rise and thanks to the efficiency of new all-sky surveys in detecting transients on their rise. We also consider alternative scenarios that could explain the early spectral features of Gaia22alz and its unusually slow rise.

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E. Aydi, L. Chomiuk, J. Mikołajewska, et. al.
Tue, 11 Apr 23
6/63

Comments: 20 pages, 12 figures, 2 tables. Submitted to MNRAS

GRB 211211A: a Neutron Star$-$White Dwarf Merger? [HEAP]

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http://arxiv.org/abs/2304.04009


The gamma-ray burst GRB 211211A and its associated kilonova-like emission were reported recently. A significant difference between this association event and GRB 170817A/AT 2017gfo is that GRB 211211A has a very long duration. In this paper, we show that this association event may arise from a neutron star$-$white dwarf (NS$-$WD) merger if a magnetar leaves finally in the central engine. Within the NS$-$WD merger, the main burst of GRB 211211A could be produced by magnetic bubble eruptions from toroidal magnetic field amplification of the pre-merger NS. This toroidal field amplification can be induced by the runaway accretion from the WD debris disc if the disc is in low initial entropy and efficient wind. While the extended emission of GRB 211211A is likely involved with magnetic propelling. The observed energetics and duration of the prompt emission of GRB 211211A can be fulfilled in comparison with those of accretion in hydrodynamical thermonuclear simulation, as long as the WD has a mass $\gtrsim1M_{\odot}$. Moreover, if the X-ray plateau in GRB afterglows is due to the magnetar spin-down radiation, GRB optical afterglows and kilonova-like emission can be well jointly modeled combining the standard forward shock with the radioactive decay power of $^{56}{\rm Ni}$ adding a rotational power input from the post-merger magnetar.

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S. Zhong, L. Li and Z. Dai
Tue, 11 Apr 23
7/63

Comments: Accepted by ApJ Letters. The accretion rate can be &gt;0.01$M_{\odot}s^{-1}$ if the WD debris disc is in low initial entropy simulated by Kaltenborn et al. (2022). Main burst vs. extended emission: accretion vs. propelling. Kilonova-like emission: magnetar-fed $^{56}{\rm Ni}$ power

A Numerical Study of the Impact of Jet Magnetic Topology on Radio Galaxy Evolution [HEAP]

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http://arxiv.org/abs/2304.03863


The propagation of active galactic nucleus jets depends both on the environment into which they propagate and on their internal structure. To test the impact that different magnetic topologies have on the observable properties of radio galaxies on kpc scales, we conducted a series of magneto-hydrodynamic simulations of jets injected with different magnetic field configurations propagating into a gaseous atmosphere modeled on the Perseus cluster. The simulations show that the structure of the field affects the collimation and propagation of the jets on cluster scales and thus the morphology of the radio lobes inflated by the jets, due both to magnetic collimation and the development of dynamical instabilities in jets with different magnetic topologies. In all cases, the simulations show a distinct reversal of the sychrotron spectral age gradient in the radio lobes about a dynamical time after the jets turn off due to large scale circulation inside the radio lobe, driven primarily by buoyancy, which could provide a way to constrain the age of radio sources in cluster environments without the need for detailed spectral modeling and thus constrain the radio mode feedback efficiency. We suggest a robust diagnostic to search for such age gradients in multi-frequency radio data.

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Y. Chen, S. Heinz and E. Hooper
Tue, 11 Apr 23
9/63

Comments: Accepted for publication in the Monthly Notices of the Royal Astronomical Society

Research on electron and positron spectrum in the high-energy region based on the gluon condensation model [HEAP]

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http://arxiv.org/abs/2304.04226


Electron(positron), proton and nuclei can be accelerated to very high energy by local supernova remnants (SNR). The famous excesses of electron and proton (nuclei) potentially come from such kind of local sources. Recently, the DAMPE experiment measured the electron spectrum (including both electrons and positrons) of cosmic rays with high-accuracy. It provides an opportunity to further explore the excess of electrons. According to the gluon condensation (GC) theory, once GC occurs, huge number of gluons condense at a critical momentum, and the production spectrum of electron and proton showing typical GC characteristics. There are exact correlations between the electron and proton spectrum from a same GC process. It is possible to interpret the power-law break of cosmic rays in view of GC phenomenon, and predict one from another based on the relations between electron and proton spectrum. In this work, we point out the potential existence of a second excess in the electron spectrum, the characteristics of this excess is derived from experimental data of proton. We hope that the future DAMPE experiments will confirm the existence of this second excess and support the result of GC model.

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J. Wu, M. Feng and J. Ruan
Tue, 11 Apr 23
10/63

Comments: N/A

Effect of magnetic field correlation length on the gamma-ray pulsar halo morphology under anisotropic diffusion [HEAP]

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http://arxiv.org/abs/2304.04570


Anisotropic diffusion is one of the potential interpretations for the morphology of the Geminga pulsar halo. It interprets the observed slow-diffusion phenomenon through a geometric effect, assuming the mean magnetic field direction around Geminga is closely aligned with the line of sight toward it. However, this direction should not extend further than the correlation length of the turbulent magnetic field $L_c$, which could be $100$ pc or less. We first revisit the $L_c=\infty$ scenario and show that the halo asymmetry predicted by this scenario is mainly contributed by the electrons located beyond the “core” section around Geminga, which has a length of $100$ pc. Then, considering the directional variation of the magnetic field beyond the core section, we take one magnetic field configuration as an example to investigate the possible halo morphology. The predicted morphology has some different features compared to the $L_c=\infty$ scenario. The current experiments may already be able to test these features. In addition, we use a semi-analytical method to solve the anisotropic propagation equation, which offers significant convenience compared to numerical approaches.

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K. Fang, H. Hu, X. Bi, et. al.
Tue, 11 Apr 23
11/63

Comments: 15 pages, 7 figures

Intra-night optical flux and polarization variability of BL~Lacertae during its 2020 $-$ 2021 high state [HEAP]

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http://arxiv.org/abs/2304.03975


In this work, we report the presence of rapid intra-night optical variations in both — flux and polarization of the blazar BL Lacertae during its unprecedented 2020–2021 high state of brightness. The object showed significant flux variability and some color changes, but no firmly detectable time delays between the optical bands. The linear polarization was also highly variable in both — polarization degree and angle (EVPA). The object was observed from several observatories throughout the world, covering in a total of almost 300 hours during 66 nights. Based on our results, we suggest, that the changing Doppler factor of an ensemble of independent emitting regions, travelling along a curved jet that at some point happens to be closely aligned with the line of sight can successfully reproduce our observations during this outburst. This is one of the most extensive variability studies of the optical polarization of a blazar on intra-night timescales.

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R. Bachev, T. Tripathi, A. Gupta, et. al.
Tue, 11 Apr 23
12/63

Comments: 23 pages,7 figures, 5 Tables (2 as appendix). Accepted for publication in MNRAS

Prompt-to-afterglow transition of optical emission in a long gamma-ray burst consistent with a fireball [HEAP]

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http://arxiv.org/abs/2304.04669


Long gamma-ray bursts (GRBs), which signify the end-life collapsing of very massive stars, are produced by extremely relativistic jets colliding into circumstellar medium. Huge energy is released both in the first few seconds, namely the internal dissipation phase that powers prompt emissions, and in the subsequent self-similar jet-deceleration phase that produces afterglows observed in broad-band electromagnetic spectrum. However, prompt optical emissions of GRBs have been rarely detected, seriously limiting our understanding of the transition between the two phases. Here we report detection of prompt optical emissions from a gamma-ray burst (i.e. GRB 201223A) using a dedicated telescope array with a high temporal resolution and a wide time coverage. The early phase coincident with prompt {\gamma}-ray emissions show a luminosity in great excess with respect to the extrapolation of {\gamma}-rays, while the later luminosity bump is consistent with onset of the afterglow. The clearly detected transition allows us to differentiate physical processes contributing to early optical emissions and to diagnose the composition of the jet

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L. Xin, X. Han, H. Li, et. al.
Tue, 11 Apr 23
17/63

Comments: Authors’ version of article published in Nature Astronomy, see their website for official version

Antistars as possible sources of antihelium cosmic rays [HEAP]

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http://arxiv.org/abs/2304.04623


A minor population of antistars in galaxies has been predicted by some of non-standard models of baryogenesis and nucleosynthesis in the early Universe, and their presence is not yet excluded by the currently available observations. Detection of an unusually high abundance of antinuclei in cosmic rays can probe the baryogenesis scenarios in the early Universe. Recent report of the \textit{AMS-02} collaboration on the tentative detection of a few antihelium nuclei in GeV cosmic rays provided a great hope on the progress in this issue. We discuss possible sources of antinuclei in cosmic rays from antistars which are predicted in a modified Affleck-Dine baryogenesis scenario by Dolgov and Silk (1993). The model allows us to estimate the expected fluxes and isotopic content of antinuclei in the GeV cosmic rays produced in scenarios involving antistars. We show that the flux of antihelium CRs reported by the \textit{AMS-02} experiment can be explained by Galactic anti-nova outbursts, thermonuclear anti-SN Ia explosions, a collection of flaring antistars or an extragalactic source with abundances not violating existing gamma-ray and microlensing constraints on the antistar population.

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A. Bykov, K. Postnov, A. Bondar, et. al.
Tue, 11 Apr 23
21/63

Comments: 14 pages, to be submitted. Comments are welcome!

Mahakala: a Python-based Modular Ray-tracing and Radiative Transfer Algorithm for Curved Space-times [HEAP]

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http://arxiv.org/abs/2304.03804


We introduce Mahakala, a Python-based, modular, radiative ray-tracing code for curved space-times. We employ Google’s JAX framework for accelerated automatic differentiation, which can efficiently compute Christoffel symbols directly from the metric, allowing the user to easily and quickly simulate photon trajectories through non-Kerr metrics. JAX also enables Mahakala to run in parallel on both CPUs and GPUs and achieve speeds comparable to C-based codes. Mahakala natively uses the Cartesian Kerr-Schild coordinate system, which avoids numerical issues caused by the “pole” of spherical coordinates. We demonstrate Mahakala’s capabilities by simulating the 1.3 mm wavelength images (the wavelength of Event Horizon Telescope observations) of general relativistic magnetohydrodynamic simulations of low-accretion rate supermassive black holes. The modular nature of Mahakala allows us to easily quantify the relative contribution of different regions of the flow to image features. We show that most of the emission seen in 1.3 mm images originates close to the black hole. We also quantify the relative contribution of the disk, forward jet, and counter jet to 1.3 mm images.

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A. Sharma, L. Medeiros, C. Chan, et. al.
Tue, 11 Apr 23
33/63

Comments: 15 pages, 11 figures

Gamma-Ray Emission in the Seyfert Galaxy NGC 4151: Investigating the Role of Jet and Coronal Activities [HEAP]

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http://arxiv.org/abs/2304.04138


NGC 4151, a nearby Seyfert galaxy, has recently been reported to emit gamma rays in the GeV range, posing an intriguing astrophysical mystery. The star formation rate of NGC 4151 is too low to explain the observed GeV flux, but the galaxy is known for its coronal activity in X-ray and jet activity in radio. We propose that either the combination of these two activities or the jet activity alone can account for the gamma-ray spectrum. An energy-dependent variability search would allow us to distinguish between the two scenarios, as the coronal component can only contribute at energies of $\lesssim1$ GeV. Our analysis also indicates that the expected neutrino flux from the coronal component is likely to be undetectable by IceCube.

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Y. Inoue and D. Khangulyan
Tue, 11 Apr 23
39/63

Comments: 6 pages, 3 figures

Diagnosing The Ejecta Properties of Engine-Driven Supernovae from Observables in Their Initial Phase [HEAP]

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http://arxiv.org/abs/2304.04146


Engine-driven explosions with continuous energy input from the central system have been suggested for supernovae (SNe) associated with a Gamma-Ray Burst (GRB), super-luminous SNe (SLSNe), and at least a fraction of broad-lined SNe Ic (SNe Ic-BL) even without an associated GRB. In the present work, we investigate observational consequences in this scenario, focusing on the case where the energy injection is sufficiently brief, which has been suggested for GRB-SNe. We construct a simplified, spherical ejecta model sequence taking into account the major effects of the central engine; composition mixing, density structure, and the outermost ejecta velocity. Unlike most of the previous works for GRB-SNe, we solve the formation of the photosphere self-consistently, with which we can predict the photometric and spectroscopic observables. We find that these ejecta properties strongly affect their observational appearance in the initial phase (~ a week since the explosion), highlighted by blended lines suffering from higher-velocity absorptions for the flatter density distribution and/or higher outermost ejeca velocity. This behaviour also affects the multi-band light curves in a non-monotonic way. Prompt follow-up observations starting immediately after the explosion thus provides key diagnostics to unveil the nature of the central engine behind GRB-SNe and SNe Ic-BL. For SN 2017iuk associated with GRB 171205A these diagnosing observational data are available, and we show that the expected structure from the engine-driven explosion, i.e., a flat power-law density structure extending up to >~ 100,000 km/s, can explain the observed spectral evolution reasonably well.

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K. Maeda, A. Suzuki and L. Izzo
Tue, 11 Apr 23
40/63

Comments: 12 pages, 7 figures, 1 table. Accepted for publication in MNRAS

Time delays between radio and X-ray and between narrow radio bands of Sgr A* flares in the shock oscillation model [HEAP]

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http://arxiv.org/abs/2304.03925


We examine the time delay between radio and X-ray and between narrow radio frequency flares in Sagittarius A* (Sgr A), from analyses of the synchrotron, bremsstrahlung and monochromatic luminosity curves. Using the results of 2D relativistic radiation magnetohydrodynamic (MHD) simulations based on the shock oscillation model, we find three types of time delay between the synchrotron and bremsstrahlung emissions: Type A with a time delay of 2 — 3 h on the shock descending branch, Type B with no time delay and Type C with an inverse time delay of 0.5 — 1 h on the shock ascending branch. The time delays in Types A and C are interpreted as a transit time of Alfv\'{e}n and acoustic waves between both emission dominant regions, respectively. The delay times between 22 and 43 GHz flares and between 8 and 10 GHz flares are $\sim$ 13 — 26 min and 13 min, respectively, while the inverse delay also occurs dependently on the shock location branch. These time delays between the narrow radio bands are interpreted as the transit time of the acoustic wave between the frequency-dependent effective radii $R_{\tau_{\rm \nu=1}}$, at which the optical depth $\tau_{\rm \nu}$ at the accretion disc surface becomes $\sim$ unity. The shock oscillation model explains well the observed delay times of 0.5 — 5 h between radio and X-ray, 20 — 30 min between 22 and 43 GHz and $\sim$ 18 min between 8 and 10 GHz in Sgr A.

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T. Okuda, C. Singh and R. Aktar
Tue, 11 Apr 23
42/63

Comments: 14 pages, 14 figures, (accepted for publication in MNRAS)

Spectral and Temporal Studies of Swift\,J1658.2–4242 using {\it AstroSat} Observations with {\tt JeTCAF} Model [HEAP]

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http://arxiv.org/abs/2304.04422


We present the X-ray spectral and temporal analysis of the black hole X-ray transient Swift J1658.2–4242 observed by {\it AstroSat}. Three epochs of data have been analysed using the JeTCAF model to estimate the mass accretion rates and to understand the geometry of the flow. The best-fit disc mass accretion rate ($\dot m_d$) varies between $0.90^{+0.02}{-0.01}$ to $1.09^{+0.04}{-0.03}$ $\dot M_{\rm Edd}$ in these observations, while the halo mass accretion rate changes from $0.15^{+0.01}{-0.01}$ to $0.25^{+0.02}{-0.01}$ $\dot M_{\rm Edd}$. We estimate the size of the dynamic corona, that varies substantially from $64.9^{+3.9}{-3.1}$ to $34.5^{+2.0}{-1.5}$ $r_g$ and a moderately high jet/outflow collimation factor stipulates isotropic outflow. The inferred high disc mass accretion rate and bigger corona size indicate that the source might be in the intermediate to soft spectral state of black hole X-ray binaries. The mass of the black hole estimated from different model combinations is $\sim 14 M_\odot$. In addition, we compute the quasi-periodic oscillation (QPO) frequencies from the model-fitted parameters, which match the observed QPOs. We further calculate the binary parameters of the system from the decay profile of the light curve and the spectral parameters. The estimated orbital period of the system is $4.0\pm0.4$ hr by assuming the companion as a mid or late K-type star. Our analysis using the JeTCAF model sheds light on the physical origin of the spectro-temporal behaviour of the source, and the observed properties are mainly due to the change in both the mass accretion rates and absorbing column density.

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S. Mondal and V. Jithesh
Tue, 11 Apr 23
44/63

Comments: 10 pages, 5 figures, 3 tables, accepted (06/03/2023) for publication in MNRAS

Detecting Stochastic Wave Dark Matter with Fermi-LAT $γ$-ray Pulsar Timing Array [HEAP]

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http://arxiv.org/abs/2304.04735


Wave dark matter (DM) represents a class of the most representative DM candidates. Due to its periodic perturbation to spacetime, the wave DM can be detected with a galactic interferometer – pulsar timing array (PTA). We perform in this Letter a first analysis of applying the $\gamma$-ray PTA to detect the wave DM, with the data of Fermi Large Area Telescope (Fermi-LAT). Despite the limitation in statistics, the $\gamma$-PTA demonstrates a promising sensitivity potential for a mass $\sim 10^{-23}-10^{-22}$ eV. We show that the upper limits not far from those of the dedicated radio-PTA projects can be achieved. Particularly, we have fulfilled an analysis to cross-correlate the pulsar data, which has been essentially missing so far in real data analysis but is known to be crucial for identifying the nature of potential signals, with the Fermi-LAT data of two pulsars.

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H. Luu, T. Liu, J. Ren, et. al.
Tue, 11 Apr 23
47/63

Comments: 5 pages, 3 figures. Comments welcome!

The importance of live binary evolution in numerical simulations of binaries embedded in circumbinary discs [HEAP]

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http://arxiv.org/abs/2304.03790


The shrinking of a binary orbit driven by the interaction with a gaseous circumbinary disc, initially advocated as a potential way to catalyze the binary merger, has been recently debated in the case of geometrically thick (i.e. with $H/R\gtrsim 0.1$) discs. However, a clear consensus is still missing mainly owing to numerical limitations, such as fixed orbit binaries or lack of resolution inside the cavity carved by the binary in its circumbinary disc. In this work, we asses the importance of evolving the binary orbit by means of hydrodynamic simulations performed with the code {\sc gizmo} in meshless-finite-mass mode. In order to model the interaction between equal mass circular binaries and their locally isothermal circumbinary discs, we enforce hyper-Lagrangian resolution inside the cavity. We find that fixing the binary orbit ultimately leads to an overestimate of the gravitational torque that the gas exerts on the binary, and in an underestimate of the torque due to the accretion of material onto the binary components. Furthermore, we find that the modulation of the accretion rate on the binary orbital period is strongly suppressed in the fixed orbit simulation, while it is clearly present in the live binary simulations. This has potential implications for the prediction of the observable periodicities in massive black hole binary candidates.

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A. Franchini, A. Lupi, A. Sesana, et. al.
Tue, 11 Apr 23
48/63

Comments: 7 pages, 8 figures, accepted for publication in MNRAS

HOW-MHD: A High-Order WENO-Based Magnetohydrodynamic Code with a High-Order Constrained Transport Algorithm for Astrophysical Applications [HEAP]

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http://arxiv.org/abs/2304.04360


Due to the prevalence of magnetic fields in astrophysical environments, magnetohydrodynamic (MHD) simulation has become a basic tool for studying astrophysical fluid dynamics. To further advance the precision of MHD simulations, we have developed a new simulation code that solves ideal adiabatic or isothermal MHD equations with high-order accuracy. The code is based on the finite-difference weighted essentially non-oscillatory (WENO) scheme and the strong stability-preserving Runge-Kutta (SSPRK) method. Most of all, the code implements a newly developed, high-order constrained transport (CT) algorithm for the divergence-free constraint of magnetic fields, completing its high-order competence. In this paper, we present the version in Cartesian coordinates, which includes a fifth-order WENO and a fourth-order five-stage SSPRK, along with extensive tests. With the new CT algorithm, fifth-order accuracy is achieved in convergence tests involving the damping of MHD waves in three-dimensional space. And substantially improved results are obtained in magnetic loop advection and magnetic reconnection tests, indicating a reduction in numerical diffusivity. In addition, the reliability and robustness of the code, along with its high accuracy, are demonstrated through several tests involving shocks and complex flows. Furthermore, tests of turbulent flows reveal the advantages of high-order accuracy, and show the adiabatic and isothermal codes have similar accuracy. With its high-order accuracy, our new code would provide a valuable tool for studying a wide range of astrophysical phenomena that involve MHD processes.

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J. Seo and D. Ryu
Tue, 11 Apr 23
51/63

Comments: 22 pages, 17 figures, submitted to ApJ

Bright X-ray pulsars as sources of MeV neutrinos in the sky [HEAP]

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http://arxiv.org/abs/2304.04520


High mass accretion rate onto strongly magnetised neutron stars results in the appearance of accretion columns supported by the radiation pressure and confined by the strong magnetic field of a star. At mass accretion rates above $\sim 10^{19}\,{\rm g\,s^{-1}}$, accretion columns are expected to be advective. Under such conditions, a noticeable part of the total energy release can be carried away by neutrinos of a MeV energy range. Relying on a simple model of the neutrino luminosity of accreting strongly magnetised neutron stars, we estimate the neutrino energy fluxes expected from six ULX pulsars known up to date and three brightest Be X-ray transits hosting magnetised neutron stars. Despite the large neutrino luminosity expected in ULX pulsars, the neutrino energy flux from the Be X-ray transients of our Galaxy, SMC and LMC is dominant. However, the neutrino flux from the brightest X-ray transients is estimated to be below the isotropic background by two orders of magnitude at least, which makes impossible direct registration of neutrino emission from accreting strongly magnetised neutron stars nowadays.

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A. Asthana, A. Mushtukov, A. Dobrynina, et. al.
Tue, 11 Apr 23
55/63

Comments: 7 pages, 6 figures, submitted to MNRAS

Rotation in Event Horizon Telescope Movies [HEAP]

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http://arxiv.org/abs/2304.03826


The Event Horizon Telescope (EHT) has produced images of M87* and Sgr A*, and will soon produce time sequences of images, or movies. In anticipation of this, we describe a technique to measure a rotation rate, or pattern speed $\Omega_p$, from movies using an autocorrelation technique. We validate the technique on Gaussian random field models with a known rotation rate and apply it to a library of synthetic images of Sgr A* based on general relativistic magnetohydrodynamics (GRMHD) simulations. We predict that EHT movies will have $\Omega_p \approx 1$ degree per $\mathrm{GMc^{-3}}$, which is of order $15\%$ of the Keplerian orbital frequency in the emitting region. We can plausibly attribute the slow rotation seen in our models to the pattern speed of inward-propagating spiral shocks. We also find that $\Omega_p$ depends strongly on inclination. Application of this technique will enable us to compare future EHT movies with the clockwise rotation of Sgr A* seen in near-infrared flares by GRAVITY. Pattern speed analysis of future EHT observations of M87* and Sgr A* may also provide novel constraints on black hole inclination and spin, as well as an independent measurement of black hole mass.

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N. Conroy, M. Baubock, V. Dhruv, et. al.
Tue, 11 Apr 23
56/63

Comments: N/A

Kinetic Simulations of the Filamentation Instability in Pair Plasmas [HEAP]

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http://arxiv.org/abs/2304.03577


The nonlinear interaction between electromagnetic waves and plasmas attracts significant attention in astrophysics because it can affect the propagation of Fast Radio Bursts (FRBs) — luminous millisecond-duration pulses detected at radio frequency. The filamentation instability (FI) — a type of nonlinear wave-plasma interaction — is considered to be dominant near FRB sources, and its nonlinear development may also affect the inferred dispersion measure of FRBs. In this paper, we carry out fully kinetic particle-in-cell simulations of the FI in unmagnetized pair plasmas. Our simulations show that the FI generates transverse density filaments, and that the electromagnetic wave propagates in near vacuum between them, as in a waveguide. The density filaments keep merging until force balance between the wave ponderomotive force and the plasma pressure gradient is established. We estimate the merging timescale and discuss the implications of filament merging for FRB observations.

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M. Iwamoto, E. Sobacchi and L. Sironi
Mon, 10 Apr 23
1/36

Comments: Submitted to MNRAS

Back to the Starting Point: on the Simulation of Initial Magnetic Fields and Spin Periods of Non-accretion Pulsars [HEAP]

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http://arxiv.org/abs/2304.03530


Neutron stars (NSs) play essential roles in modern astrophysics. Magnetic fields and spin periods of newborn (zero age) NSs have large impact on the further evolution of NSs, which are however poorly explored in observation due to the difficulty of finding newborn NSs. In this work, we aim to infer the magnetic fields and spin periods (Bi and Pi) of zero-age NSs from the observed properties of NS population. We select non-accretion NSs (NANSs) whose evolution is solely determined by magnetic dipole radiation. We find that both Bi and Pi can be described by log-normal distribution and the fitting sensitively depends on our parameters.

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K. Xu, H. Yang, Y. Mao, et. al.
Mon, 10 Apr 23
3/36

Comments: 8 pages, 5 figures, accepted for publication in ApJ

The Landscape of Thermal Transients from Supernova Interacting with a Circumstellar Medium [HEAP]

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http://arxiv.org/abs/2304.03360


The interaction of supernova ejecta with a surrounding circumstellar medium (CSM) generates a strong shock which can convert the ejecta kinetic energy into observable radiation. Given the diversity of potential CSM structures (arising from diverse mass loss processes such as late-stage stellar outbursts, binary interaction, and winds), the resulting transients can display a wide range of light curve morphologies. We provide a framework for classifying the transients arising from interaction with a spherical CSM shell. The light curves are decomposed into five consecutive phases, starting from the onset of interaction and extending through shock breakout and subsequent shock cooling. The relative prominence of each phase in the light curve is determined by two dimensionless quantities representing the CSM-to-ejecta mass ratio $\eta$, and a breakout parameter $\xi$. These two parameters define four light curve morphology classes, where each class is characterized by the location of shock breakout and the degree of deceleration as the shock sweeps up the CSM. We compile analytic scaling relations connecting the luminosity and duration of each light curve phase to the physical parameters. We then run a grid of radiation hydrodynamics simulations for a wide range of ejecta and CSM parameters to numerically explore the landscape of interaction light curves, and to calibrate and confirm the analytic scalings. We connect our theoretical framework to several case studies of observed transients, highlighting the relevance in explaining slow-rising and superluminous supernovae, fast blue optical transients, and double-peaked light curves.

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D. Khatami and D. Kasen
Mon, 10 Apr 23
4/36

Comments: 30 pages, 18 figures, submitted to ApJ

What's in a binary black hole's mass parameter? [HEAP]

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http://arxiv.org/abs/2304.03498


The gravitational wave observations have revealed four emerging peaks in the binary black hole mass distribution suggesting an overproduction of binaries clustered around specific mass values. Although the presence of the first and the third peaks has been attributed to binary black hole formation in star clusters or due to the evolution of stellar binaries in isolation, the second peak, because it lacks significance in the primary mass distribution, has received relatively less attention. In this article, we report that confidence in the second peak depends on the mass parameter we choose to model the population on. Unlike primary mass, when modelled on the chirp mass this peak is significant. We discuss the disparity as a consequence of mass asymmetry in the observations that cluster at the second peak. Finally, we report this asymmetry to be part of a potential trend in the mass ratio distribution which is manifested as a function of the chirp mass, but not as a function of primary mass, when we include the observation GW190814 in our modelling. Chirp mass is not a parameter of astrophysical relevance. Features present in the chirp mass, but not in the primary mass, are relatively difficult to explain and expected to garner significant interest.

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V. Tiwari
Mon, 10 Apr 23
7/36

Comments: N/A

Flares from stars crossing active galactic nuclei disks on low-inclination orbits [HEAP]

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http://arxiv.org/abs/2304.03670


The origin of the recently discovered new class of transients, X-ray quasi-periodic eruptions (QPEs), remains a puzzle. Due to their periodicity and association with active galactic nuclei (AGN), it is natural to relate these eruptions to stars or compact objects in tight orbits around supermassive black holes (SMBHs). In this paper, we predict the properties of emission from bow shocks produced by stars crossing AGN disks, and compare them to the observed properties of QPEs. We find that when a star’s orbit is retrograde and has a low inclination ($\lesssim 20^\circ$) with respect to the AGN disk, the breakout emission from the bow shock can explain the observed duration ($\sim$ hours) and X-ray luminosity ($\sim$few$\times10^{42}~{\rm erg~s^{-1}}$) of QPEs. This model can further explain various observed features of QPEs, such as their complex luminosity evolution, the gradual decline of luminosity of the flares over several years, the evolution of the hardness ratio, the modulation of the luminosity during quiescent phases, and the preference of the central SMBHs to have low masses.

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H. Tagawa and Z. Haiman
Mon, 10 Apr 23
10/36

Comments: 11 pages, 7 figures

Ultraslow PSR J0901-4046 with an ultrahigh magnetic field of $3.2\times10^{16}$ G [HEAP]

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http://arxiv.org/abs/2304.03702


The recent discovery of a radio-emitting neutron star with an ultralong spin period of 76 s, PSR J0901-4046, raises a fundamental question on how such a slowly rotating magnetized object can be active in the radio band. A canonical magnetic field of $1.3\times10^{14}$ G estimated from the pulsar period and its time derivative is wholly insufficient for PSR J0901-4046 to operate. Consideration of a magnetic inclination angle of $10^\circ$ estimated from the pulse width gives a higher magnetic field of $1.5\times10^{15}$ G, which is still an order of magnitude lower than the necessary minimum of $2.5\times10^{16}$ G following from the death line for radio pulsars with magnetic fields exceeding the critical value $4.4\times10^{13}$ G. We show that if the observed microstructure of single pulses reflects relativistic beaming, the inferred surface magnetic field appears to be $3.2\times10^{16}$ G, and without this assumption it is no less than $2.7\times10^{16}$ G, which explains the existence of radio emission from PSR J0901-4046. This estimation makes PSR J0901-4046 a radio pulsar with the strongest magnetic field known and is a sign that PSR J0901-4046 slows down not by magnetic-dipole radiation, but rather by an electric current of 56 MA, when rotational energy is expended in accelerating charged particles over the polar cap.

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D. Sob’yanin
Mon, 10 Apr 23
12/36

Comments: 6 pages

Multi-band optical variability of a newly discovered twelve blazars sample from 2013-2019 [HEAP]

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http://arxiv.org/abs/2304.03664


Here we present the first optical photometric monitoring results of a sample of twelve newly discovered blazars from the ICRF – Gaia CRF astrometric link. The observations were performed from April 2013 until August 2019 using eight telescopes located in Europe. For a robust test for the brightness and colour variability, we use Abbe criterion and F-test. Moreover, linear fittings are performed to investigate the relation in the colour-magnitude variations of the blazars. Variability was confirmed in the case of 10 sources; two sources, 1429+249 and 1556+335 seem to be possibly variable. Three sources (1034+574, 1722+119, and 1741+597) have displayed large amplitude brightness change of more than one magnitude. We found that the seven sources displayed bluer-when-brighter variations, and one source showed redder-when-brighter variations. We briefly explain the various AGN emission models which can explain our results.

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M. Jovanovic, G. Damljanovic, F. Taris, et. al.
Mon, 10 Apr 23
18/36

Comments: 26 pages, 8 figures, 6 supplement figures, 11 tables, Accepted for publication in MNRAS

Two-temperature accretion flows around strongly magnetized stars and their spectral analysis [HEAP]

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http://arxiv.org/abs/2304.03329


We investigate two-temperature accretion flows onto strongly magnetized compact stars. Matter is accreted in the form of an accretion disc upto the disc radius ($r_{\rm d}$), where, the magnetic pressure exceeds both the gas and ram pressure and thereafter the matter is channelled along the field lines onto the poles. We solve the equations of motion self-consistently along the field lines, incorporating radiative processes like bremsstrahlung, synchrotron and inverse-Comptonization. For a given set of constants of motion, the equations of motion do not produce unique transonic solution. Following the second law of thermodynamics the solution with the highest entropy is selected and thereby eliminating the degeneracy in solution. We study the properties of these solutions and obtain corresponding spectra as a function of the magnetic field ($B_$), spin period ($P$) and accretion rate of the star ($\dot{M}$). A primary shock is always formed just near the surface. The enhanced radiative processes in this post-shock region slows down the matter and it finally settles on the surface of the star. This post-shock region contributes to $\gtrsim 99.99\%$ of the total luminosity obtained from the accretion flow. It is still important to study the full accretion flow because secondary shocks may be present for some combination of $B_$, $P$ and ${\dot{M}}$ in addition to primary shocks. We find that secondary shocks, if present, produce an extended emission at higher energies in the spectra.

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S. Sarkar, K. Singh, I. Chattopadhyay, et. al.
Mon, 10 Apr 23
20/36

Comments: 18 pages, 17 figures and accepted for publication in MNRAS

Principal Component Analysis of Ground Level Enhancement of Cosmic Ray Events [HEAP]

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http://arxiv.org/abs/2304.03695


We applied principal component analysis (PCA) to the study of five ground level enhancement (GLE) of cosmic ray (CR) events. The nature of the multivariate data involved makes PCA a useful tool for this study. A subroutine program written and implemented in R software environment generated interesting principal components. Analysis of the results shows that the method can distinguish between neutron monitors (NMs) that observed Forbush decrease (FD) from those that observed GLE at the same time. The PCA equally assigned NMs with identical signal counts with the same correlation factor (r) and those with close r values equally have a close resemblance in their CR counts. The results further indicate that while NMs that have the same time of peak may not have the same r, most NMs that had the same r also had the same time of peak. Analyzing the second principal components yielded information on the differences between NMs having opposite but the same or close values of r. NMs that had the same r equally had the tendency of being in close latitude.

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R. Ugwoke, A. Ubachukwu, J. Urama, et. al.
Mon, 10 Apr 23
29/36

Comments: N/A

Upper limits on transmitter rate of extragalactic civilizations placed by Breakthrough Listen observations [HEAP]

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http://arxiv.org/abs/2304.02756


The Search for Extra-Terrestrial Intelligence (SETI) has been conducted for over sixty years, yet no technosignatures have been identified. Previous studies have focused on stars in our galaxy, with few searches in the extragalactic Universe despite a larger volume being available. Civilizations capable of harvesting energy from a star or a galaxy are classified as KII or KIII on the Kardashev scale, respectively. Technosignatures from such advanced civilizations would be extremely luminous and detectable by current radio telescopes, even from distant galaxies. To explore the frontier of extragalactic SETI, we investigate the likely prevalence of extragalactic civilizations possessing a radio transmitter, known as the transmitter rate, based on observational results from the Breakthrough Listen (BL) observations. We calculated the transmitter rate by considering the background galaxies in the field of view of target stars in BL observations. We used a statistical method to derive the total mass of stars in those background galaxies from a galaxy stellar mass function. Our statistical method suggests that less than one in hundreds of trillions of extragalactic civilizations within 969 Mpc possess a radio transmitter above 7.7$\times$10$^{26}$ W of power, assuming one civilization per one-solar-mass stellar system. Additionally, we cross-matched the BL survey fields with the WISE$\times$SuperCOSMOS Photometric Redshift Catalogue and compared with the statistical method. Our result sets the strictest limits to date on the transmitter rate at such high power levels, emphasizing the high efficiency of searching for radio transmitters in galaxies and the rarity of technologically advanced civilizations in our Universe.

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Y. Uno, T. Hashimoto, T. Goto, et. al.
Fri, 7 Apr 23
1/50

Comments: 5 pages, 1 figure, accepted for publication in MNRAS

Déjà-vu et Déjà-entendu: Associating fast radio bursts with compact binary mergers via gravitational lensing [HEAP]

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http://arxiv.org/abs/2304.02879


The origin of fast radio bursts (FRBs) is currently an open question with several proposed sources and corresponding mechanisms for their production. Among them are compact binary coalescences (CBCs) that also generate gravitational waves (GWs). Spatial and temporal coincidences between GWs and FRBs have so far been used to search for potential FRB counterparts to GWs from CBCs. However, such methods suffer from relatively poor sky-localisation of the GW sources, and similarly poor luminosity distance estimates of both GW and FRB sources. The time delay between the GW and radio emission is also poorly understood. In this work, we propose an astrophysical scenario that could potentially provide an unambiguous association between CBCs and FRBs, if one exists, or unambiguously rule out FRB counterparts to a given CBC GW event. We demonstrate that, if a CBC that emitted both GWs and FRBs, is gravitationally lensed, we can make a $> 5\sigma$ association using time-delay estimates of the lensed GW and FRB images (in strong lensing), which are expected to be measured with mili-second (for GW) and nano-second (FRB) precisions. We also demonstrate that the CBC-FRB association can be made in the microlensing regime as well where wave-optics effects modulate the GW waveform. We further investigate the rate of such detected associations in future observing scenarios of both GW and radio detectors.

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M. Singh, S. Kapadia, S. Basak, et. al.
Fri, 7 Apr 23
3/50

Comments: 11 pages, 7 figures

Inferring the Astrophysical Population of Gravitational Wave Sources in the Presence of Noise Transients [HEAP]

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http://arxiv.org/abs/2304.02665


The global network of interferometric gravitational wave (GW) observatories (LIGO, Virgo, KAGRA) has detected and characterized nearly 100 mergers of binary compact objects. However, many more real GWs are lurking sub-threshold, which need to be sifted from terrestrial-origin noise triggers (known as glitches). Because glitches are not due to astrophysical phenomena, inference on the glitch under the assumption it has an astrophysical source (e.g. binary black hole coalescence) results in source parameters that are inconsistent with what is known about the astrophysical population. In this work, we show how one can extract unbiased population constraints from a catalog of both real GW events and glitch contaminants by performing Bayesian inference on their source populations simultaneously. In this paper, we assume glitches come from a specific class with a well-characterized effective population (blip glitches). We also calculate posteriors on the probability of each event in the catalog belonging to the astrophysical or glitch class, and obtain posteriors on the number of astrophysical events in the catalog, finding it to be consistent with the actual number of events included.

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J. Heinzel, C. Talbot, G. Ashton, et. al.
Fri, 7 Apr 23
12/50

Comments: 13 pages, 10 figures

Spectral Energy Distribution profiles from AGN accretion disc in multi-gap setup [HEAP]

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http://arxiv.org/abs/2304.03015


Spectral Energy Distribution (SED) of the broad-band continuum emission from black-hole accretion discs can serve as a tool to measure parameters of the central body and constrain the geometry of the inner accretion flow. We focus on the case of an active galactic nucleus (AGN), with an accretion disc dominating the UV/optical bands. We parameterize the changes in the thermal and power-law components, which can reveal the diminution of the emissivity. To this end we explore the effects of gaps in the accretion disc and the emerging SED that can be caused by the presence of either (i) the inner, optically thin, radiatively inefficient hot flow; (ii) a secondary black hole embedded within the accretion disc; or (iii) a combination of both components. We suggest that the resulting changes in the SED of the underlying continuum can help us to understand some departures from the standard-disc scenario. We estimate that the data required for such a project must be sampled in detail over the far-UV to soft X-ray bands during the interval of about a month corresponding to the characteristic variability timescale of an AGN. Detecting a gap at intermediate radii of a few 100 gravitational radii would require quality photometry with uncertainties up to $\sim$ 1%. The presence of the central cavity in the standard disc can be recovered in UV photometric data with an accuracy of 5% and better. We show the effect of the intrinsic reddening of the source and demonstrate when it can be disentangled.

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M. Štolc, M. Zajaček, B. Czerny, et. al.
Fri, 7 Apr 23
24/50

Comments: 17 pages, 10 figures and 5 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society

Two Transient Quasi-periodic Oscillations in $γ$-Ray Emission from the Blazar S4 0954+658 [HEAP]

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http://arxiv.org/abs/2304.03085


In this work, we report periodicity search analyses in the gamma-ray light curve of the blazar S4 0954+658 monitoring undertaken by the Fermi Large Area Telescope (LAT). Four analytical methods and a tool are adopted to detect any periodic flux modulation and corresponding significance level, revealing that (i) a 66 d quasi-periodic oscillation (QPO) with the significance level of $> 5\sigma$ spanning over 600 d from 2015 to 2016 (MJD 57145–57745), resulting in continuous observation of nine cycles, which is one of the highest cycles discerned in blazar gamma-ray light curve; (ii) a possible QPO of 210 d at a moderate significance of $\sim3.5\sigma$ lasted for over 880 d from 2020 to 2022 (MJD 59035–59915), which lasted for four cycles. In addition, we discuss several physical models to explain the origin of the two transient QPOs and conclude that a geometrical scenario involving a plasma blob moving helically inside the jet can explain the time scale of the QPO.

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Y. Gong, S. Tian, L. Zhou, et. al.
Fri, 7 Apr 23
26/50

Comments: 10 pages, 11 figures; accepted for publication in ApJ

Particle-in-cell simulations of electron-positron cyclotron maser forming pulsar radio zebras [HEAP]

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http://arxiv.org/abs/2304.03001


The microwave radio dynamic spectra of the Crab pulsar interpulse contain fine structures represented via narrow-band quasiharmonic stripes. This pattern significantly constrains any potential emission mechanism. Similarly to the zebra patterns observed in, for example, type IV solar radio bursts or decameter and kilometer Jupiter radio emission, the double plasma resonance (DPR) effect of the cyclotron maser instability may interpret observations. We present the first electromagnetic relativistic particle-in-cell (PIC) simulations of the electron-positron cyclotron maser for cyclotron frequency smaller than the plasma frequency. In four distinct simulation cycles, we focused on the effects of varying plasma parameters on the instability growth rate and saturation energy. In contrast to the results obtained from electron-proton plasma simulations, we found that the pulsar electron-positron maser instability does not generate distinguishable X and Z modes. On the contrary, a singular electromagnetic XZ mode is generated close to or above the plasma frequency. Highest instability growth rates were obtained for the simulations with integer plasma-to-cyclotron frequency ratios. The instability is most efficient for plasma with characteristic loss-cone velocity in the range $v_\mathrm{th}=$ 0.2 – 0.3$c$. For low density ratios, the highest peak of the XZ mode is at the double frequency of the highest peak of the Bernstein modes, indicating that the radio emission is produced by a coalescence of two Bernstein modes with the same frequency and opposite wave numbers. Our estimate of the radiative flux generated from the simulation is up to $\sim$ 30 mJy from an area of 100 km$^2$ for an observer at 1 kpc distance without the inclusion of relativistic beaming effects, which may account for multiple orders of magnitude.

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M. Labaj, J. Benáček and M. Karlický
Fri, 7 Apr 23
31/50

Comments: 12 pages, 9 figures, 1 table, submitted to A&A

Relativistic X-Ray Reflection and Photoionised Absorption in the Neutron-Star Low-Mass X-ray Binary GX 13+1 [HEAP]

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http://arxiv.org/abs/2304.03130


We analysed a dedicated NuSTAR observation of the neutron-star low-mass X-ray binary Z-source GX 13+1 to study the timing and spectral properties of the source. From the colour-colour diagram, we conclude that during that observation the source transitioned from the normal branch to the flaring branch. We fitted the spectra of the source in each branch with a model consisting of an accretion disc, a Comptonised blackbody, relativistic reflection (relxillNS), and photo-ionised absorption (warmabs). Thanks to the combination of the large effective area and good energy resolution of NuSTAR at high energies, we found evidence of relativistic reflection in both the Fe K line profile, and the Compton hump present in the 10–25 keV energy range. The inner disc radius is $R_{\rm in} \lesssim 9.6~r_g$, which allowed us to further constrain the magnetic field strength to $B \lesssim 1.8 \times 10^8$ G. We also found evidence for the presence of a hot wind leading to photo-ionised absorption of Fe and Ni, with a Ni overabundance of $\sim$6 times solar. From the spectral fits, we find that the distance between the ionising source and the slab of ionised absorbing material is $\sim 4-40 \times 10^5$ km. We also found that that the width of the boundary layer extends $\sim$3 km above the surface of a neutron star, which yielded a neutron-star radius $R_{\rm NS}\lesssim 16$ km. The scenario inferred from the spectral modelling becomes self-consistent only for high electron densities in the accretion disk, $n_e \sim 10^{22}-10^{23}$ cm$^{-3}$, as expected for a Shakura-Sunyaev disc, and significantly above the densities provided by relxillNS models. These results have implications for our understanding of the physical conditions in GX 13+1.

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E. Saavedra, F. García, F. Fogantini, et. al.
Fri, 7 Apr 23
32/50

Comments: Accepted for publication in MNRAS. 11 pages, 4 figures

Exploring the Observability of Surviving Companions of Stripped-Envelope Supernovae: A Case Study of Type Ic SN 2020oi [HEAP]

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http://arxiv.org/abs/2304.02662


Stripped-envelope supernovae (SE SNe) were considered as the explosions of single massive stars with strong stellar winds, while later observations favor binary origins. One direct evidence to support the binary origins is to find the surviving companions of SE SNe since previous numerical studies suggested that the binary companion should survive the supernova impact and could be detectable. Recently, Gagliano et al. (2022) reported that the nearby Type Ic SN 2020oi in M100 (~17.1 Mpc) resulted from a binary system based on the HST photometric and spectroscopic observation. Based on the suggested binary properties of SN 2020oi, we conduct two-dimensional hydrodynamics simulations of supernova-companion interactions and the subsequent post-impact evolution of the companion. Our results suggest that a surviving companion becomes brighter in two orders of magnitude and temporarily redder after the SN impact. The companion might be detectable with the JWST NIRCam short wavelength channel in a few years. Furthermore, the predicted magnitudes of surviving companions show a significant magnitude gradient around the peak. This could be another indicator to identify the surviving companion from a SE SN.

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H. Chen, S. Rau and K. Pan
Fri, 7 Apr 23
33/50

Comments: 14 pages, 9 figures, accepted by ApJ

Disappearing thermal X-ray emission as a tell-tale signature of merging massive black hole binaries [HEAP]

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http://arxiv.org/abs/2304.02575


The upcoming Laser Interferometer Space Antenna (LISA) is expected to detect gravitational waves (GWs) from massive black hole binaries (MBHB). Finding the electromagnetic (EM) counterparts for these GW events will be crucial for understanding how and where MBHBs merge, measuring their redshifts, constraining the Hubble constant and the graviton mass, and for other novel science applications. However, due to poor GW sky localisation, multi-wavelength, time-dependent electromagnetic (EM) models are needed to identify the right host galaxy among many candidates. We studied merging MBHBs embedded in a circumbinary disc using high-resolution two-dimensional simulations, with a $\Gamma$-law equation of state, incorporating viscous heating, shock heating, and radiative cooling. We simulate the binary from large separation until after merger, allowing us to model the decoupling of the binary from the circumbinary disc (CBD). We compute the EM signatures and identify distinct features before, during, and after the merger. Our main result is a multi-band EM signature: we find that the MBHB produces strong thermal X-ray emission until 1-2 days prior to the merger. However, as the binary decouples from the CBD, the X-ray-bright minidiscs rapidly shrink in size, become disrupted, and the accretion rate drops precipitously. As a result, the thermal X-ray luminosity drops by orders of magnitude, and the source remains X-ray dark for several days after the merger, regardless of any post-merger effects such as GW recoil or mass loss. Looking for the abrupt spectral change where the thermal X-ray disappears is a tell-tale EM signature of LISA mergers that does not require extensive pre-merger monitoring.

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L. Krauth, J. Davelaar, Z. Haiman, et. al.
Thu, 6 Apr 23
12/76

Comments: 14 pages, 16 figures, 1 table, submitted to journal

Measurements of the Crab Pulsar's Giant Radio Pulse Amplitude Power-Law Index Using Low-Frequency Arecibo and Green Bank Telescope Observations [HEAP]

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http://arxiv.org/abs/2304.02589


We report two low-frequency measurements of the power-law index for the amplitudes of giant radio pulses from the Crab pulsar. The two observations were taken with the Arecibo and Green Bank radio telescopes at center frequencies of 327 MHz and 350 MHz, respectively. We find best-fit values for the differential power-law index $\beta$ (where $dN/dS \propto S^\beta$ and $S$ is pulse amplitude) of $-2.63 \pm 0.05$ and $-3.6 \pm 0.5$ from the Arecibo and Green Bank data sets, respectively. Both values are broadly consistent with other values previously measured for the Crab pulsar at low radio frequencies. These reported values may be useful in future giant pulse studies of the Crab pulsar.

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F. Crawford, T. Lazio, A. McEwen, et. al.
Thu, 6 Apr 23
13/76

Comments: 7 pages with 1 table and 1 figure. Accepted by The Astrophysical Journal

Searching for ejected supernova companions in the era of precise proper motion and radial velocity measurements [HEAP]

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http://arxiv.org/abs/2304.02542


The majority of massive stars are born in binaries, and most unbind upon the first supernova. With precise proper motion surveys such as Gaia, it is possible to trace back the motion of stars in the vicinity of young remnants to search for ejected companions. Establishing the fraction of remnants with an ejected companion, and the photometric and kinematic properties of these stars, offers unique insight into supernova progenitor systems. In this paper, we employ binary population synthesis to produce kinematic and photometric predictions for ejected secondary stars. We demonstrate that the unbound neutron star velocity distribution from supernovae in binaries closely traces the input kicks. Therefore, the observed distribution of neutron star velocities should be representative of their natal kicks. We evaluate the probability for any given filter, magnitude limit, minimum measurable proper motion (as a function of magnitude), temporal baseline, distance and extinction that an unbound companion can be associated with a remnant. We compare our predictions with results from previous companion searches, and demonstrate that the current sample of stars ejected by the supernova of their companion can be increased by a factor of 5-10 with Gaia data release 3. Further progress in this area is achievable by leveraging the absolute astrometric precision of Gaia, and by obtaining multiple epochs of deep, high resolution near-infrared imaging with the Hubble Space Telescope, JWST and next-generation wide-field near-infrared observatories such as Euclid or the Nancy Grace Roman Space Telescope.

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A. Chrimes, A. Levan, J. Eldridge, et. al.
Thu, 6 Apr 23
14/76

Comments: Accepted for publication in MNRAS. 19 pages, 17 figures

Cherenkov Detectors in Astroparticle Physics [HEAP]

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http://arxiv.org/abs/2304.02340


Cherenkov techniques are widely used in astroparticle experiments. This article reviews the various detection principles and the corresponding experiments, including some of the physics breakthroughs. In particular, it traces the development since the mid of the 1990s, a period when the field took a particularly dynamic development.

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C. Spiering
Thu, 6 Apr 23
33/76

Comments: Talk given at the XI International Workshop on Ring Imaging Cherenkov Detectors, Edinburgh Sept. 2022

Seven reflares, a mini-outburst and an outburst : High amplitude optical variations in the black hole X-ray binary Swift J1910.2-0546 [HEAP]

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http://arxiv.org/abs/2304.02046


We present long-term (2012-2022) optical monitoring of the candidate black hole X-ray binary Swift J1910.2-0546 with the Faulkes Telescopes and Las Cumbres Observatory (LCO) network. Following its initial bright 2012 outburst, we find that the source displayed a series of at least 7 quasi-periodic, high amplitude (~3 mags) optical reflares in 2013, with a recurrence time increasing from ~42 days to ~49 days. In 2014, the source experienced a mini-outburst with two peaks in the optical. We also study the recent 2022 outburst of the source at optical wavelengths, and perform a comparative analysis with the earlier rebrightenings. A single X-ray detection and only two radio detections were obtained during the 2013 reflaring period, and only optical detections were acquired in 2014. During the reflaring in both 2013 and 2014, the source showed bluer-when-brighter behavior, having optical colors consistent with a blackbody heating and cooling between 4500 and 9500 K, i.e. the temperature range in which hydrogen starts to ionize. Finally, we compare the flaring behavior of the source to re-brightening events in other X-ray binaries. We show that the repeated reflarings of Swift J1910.2-0546 are highly unusual, and propose that they arise from a sequence of repetitive heating and cooling front reflections travelling through the accretion disk.

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P. Saikia, D. Russell, S. Pirbhoy, et. al.
Thu, 6 Apr 23
37/76

Comments: Accepted for publication in ApJ, appendix will appear at the published version of the paper

Superheavy Elements in Kilonovae [HEAP]

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http://arxiv.org/abs/2304.02125


As LIGO-Virgo-KAGRA enters its fourth observing run, a new opportunity to search for electromagnetic counterparts of compact object mergers will also begin. The light curves and spectra from the first “kilonova” associated with a binary neutron star binary (NSM) suggests that these sites are hosts of the rapid neutron capture (“$r$”) process. However, it is unknown just how robust elemental production can be in mergers. Identifying signposts of the production of particular nuclei is critical for fully understanding merger-driven heavy-element synthesis. In this study, we investigate the properties of very neutron rich nuclei for which superheavy elements ($Z\geq 104$) can be produced in NSMs and whether they can similarly imprint a unique signature on kilonova light-curve evolution. A superheavy-element signature in kilonovae represents a route to establishing a lower limit on heavy-element production in NSMs as well as possibly being the first evidence of superheavy element synthesis in nature. Favorable NSMs conditions yield a mass fraction of superheavy elements is $X_{Z\geq 104}\approx 3\times 10^{-2}$ at 7.5 hours post-merger. With this mass fraction of superheavy elements, we find that kilonova light curves may appear similar to those arising from lanthanide-poor ejecta. Therefore, photometric characterizations of superheavy-element rich kilonova may possibly misidentify them as lanthanide-poor events.

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E. Holmbeck, J. Barnes, K. Lund, et. al.
Thu, 6 Apr 23
50/76

Comments: 9 pages, 5 figures

Proposed host galaxies of repeating fast radio burst sources detected by CHIME/FRB [HEAP]

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http://arxiv.org/abs/2304.02638


We present a search for host galaxy associations for the third set of repeating fast radio burst (FRB) sources discovered by the CHIME/FRB Collaboration. Using the ~1 arcmin CHIME/FRB baseband localizations and probabilistic methods. We identify potential host galaxies of two FRBs, 20200223B and 20190110C at redshifts of 0.06024(2) and 0.12244(6), respectively. We also discuss the properties of a third marginal candidate host galaxy association for FRB 20191106C with a host redshift of 0.10775(1). The three putative host galaxies are all relatively massive, fall on the standard mass-metallicity relationship for nearby galaxies, and show evidence of ongoing star formation. They also all show signatures of being in a transitional regime, falling in the “green valley” which is between the bulk of star-forming and quiescent galaxies. The plausible host galaxies identified by our analysis are consistent with the overall population of repeating and non-repeating FRB hosts while increasing the fraction of massive and bright galaxies. Coupled with these previous host associations, we identify a possible excess of FRB repeaters whose host galaxies have M_u – M_r colors redder than the bulk of star-forming galaxies. Additional precise localizations are required to confirm this trend.

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A. Ibik, M. Drout, B. Gaensler, et. al.
Thu, 6 Apr 23
57/76

Comments: 11 pages, submitted to AAS journals

Detection of extended gamma-ray emission around the Geminga pulsar with H.E.S.S [HEAP]

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http://arxiv.org/abs/2304.02631


Geminga is an enigmatic radio-quiet gamma-ray pulsar located at a mere 250 pc distance from Earth. Extended very-high-energy gamma-ray emission around the pulsar was discovered by Milagro and later confirmed by HAWC, which are both water Cherenkov detector-based experiments. However, evidence for the Geminga pulsar wind nebula in gamma rays has long evaded detection by imaging atmospheric Cherenkov telescopes (IACTs) despite targeted observations. The detection of gamma-ray emission on angular scales > 2 deg poses a considerable challenge for the background estimation in IACT data analysis. With recent developments in understanding the complementary background estimation techniques of water Cherenkov and atmospheric Cherenkov instruments, the H.E.S.S. IACT array can now confirm the detection of highly extended gamma-ray emission around the Geminga pulsar with a radius of at least 3 deg in the energy range 0.5-40 TeV. We find no indications for statistically significant asymmetries or energy-dependent morphology. A flux normalisation of $(2.8\pm0.7)\times10^{-12}$ cm$^{-2}$s$^{-1}$TeV$^{-1}$ at 1 TeV is obtained within a 1 deg radius region around the pulsar. To investigate the particle transport within the halo of energetic leptons around the pulsar, we fitted an electron diffusion model to the data. The normalisation of the diffusion coefficient obtained of $D_0 = 7.6^{+1.5}_{-1.2} \times 10^{27}$ cm$^2$s$^{-1}$, at an electron energy of 100 TeV, is compatible with values previously reported for the pulsar halo around Geminga, which is considerably below the Galactic average.

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H. Collaboration, F. Aharonian, F. Benkhali, et. al.
Thu, 6 Apr 23
65/76

Comments: 16 pages, 15 figures, 7 tables. Accepted for publication in Astronomy & Astrophysics

Secrets behind the RXTE/ASM light curve of Cyg X-3 [HEAP]

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http://arxiv.org/abs/2304.02422


In wind-fed X-ray binaries, the radiatively driven wind of the primary star can be suppressed by the EUV irradiation of the compact secondary star, leading to an increased accretion rate. This causes feedback between the released accretion power and the luminosity of the compact star. We investigate the feedback process between the released accretion power and the X-ray luminosity of the compact star in the unique high-mass X-ray binary Cygnus X-3. We assume that a part of the wind-fed power experiences a small amplitude variability around the source luminosity. We propose a simple heuristic model to couple the influence of EUV irradiation on the stellar wind (from the Wolf-Rayet companion star) with the X-ray source itself. The resulting time profile of luminosity mimics that of the input variability, albeit with a larger amplitude. The most important property of the input variability are turnover times when it changes its sign and starts to have either positive or negative feedback. The bolometric luminosity derived by spectral modeling is the time average of the resulting feedback luminosity. We demonstrate that the erratic behavior of the X-ray light curve of Cygnus X-3 may have its origin in the small amplitude variability of the X-ray source and feedback with the companion wind. This variability could arise in the accretion flow and/or due to the loss of kinetic energy in a jet or an accretion disk wind. In order to produce similar properties of the simulated light curve as observed, we have to restrict the largest accretion radius to a changing level, and assume variable timescales for the rise and decline phases of the light curve.

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O. Vilhu, K. Koljonen and D. Hannikainen
Thu, 6 Apr 23
74/76

Comments: Accepted for publication in Astronomy and Astrophysics 31.3.2023

Axion-photon conversion of GRB221009A [HEAP]

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http://arxiv.org/abs/2304.01819


The newly observed gamma ray burst GRB221009A exhibits the existence of 10~TeV-scale photons, and the axion-photon conversion has been suggested as a candidate to explain such energetic features of GRB221009A. In this work we adopt a model to calculate the conversion probability of the energetic photons from GRB221009A to the Earth. The result shows that the penetration probability of photons with energy above $10^1$~TeV can be up to $10^{-2}-10^{-4}$ depending on the coupling constant $g_{a\gamma}$ and the axion mass $m_a$, together with the magnetic field parameters of the host galaxy of GRB221009A. By comparing the results in this article with the data from LHAASO, we can obtain more precise constraints on the ranges of these parameters.

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L. Wang and B. Ma
Wed, 5 Apr 23
3/62

Comments: 7 latex pages, 5 figures

Gravitational Bose-Einstein Condensation of Vector/Hidden Photon Dark Matter [HEAP]

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http://arxiv.org/abs/2304.01965


We study the gravitational Bose-Einstein condensation of a massive vector field in the kinetic regime and the non-relativistic limit using non-linear dynamical numerical methods. Gravitational condensation leads to the spontaneous formation of solitons. We measure the condensation time and growth rate, and compare to analytical models in analogy to the scalar case. We find that the condensation time of the vector field depends on the correlation between its different components. For fully correlated configurations, the condensation time is the same as that for a scalar field. On the other hand, uncorrelated or partially correlated configurations condense slower than the scalar case. As the vector soliton grows, it acquires a net spin angular momentum even if the total spin angular momentum of the initial conditions is zero.

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J. Chen, X. Du, M. Zhou, et. al.
Wed, 5 Apr 23
10/62

Comments: 10 pages, 7 figures

Estimating Black Hole Spin from AGN SED Fitting: The Impact of General-Relativistic Ray Tracing [HEAP]

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http://arxiv.org/abs/2304.01253


Accretion disc model fitting to optical/UV quasar spectra requires that the highest mass black holes have the highest spin, with implications on the hierarchical growth of supermassive black holes and their host galaxies over cosmic time. However, these accretion disc models did not include the effects of relativistic ray tracing. Here we show that gravitational redshift cancels out most of the increase in temperature and luminosity from the smaller radii characteristic of high spin. These self consistent accretion disc models do not fit the UV spectra of the most massive quasars ($\log M/M_{\odot} \geq 9.5$), most likely showing that the disc structure is very different to that assumed. We extend the relativistic ray tracing on more complex disc models, where the emission is not limited to (colour temperature corrected) black body radiation but can instead be emitted as warm and hot Comptonisation. We demonstrate this on the broadband (UV/X-ray) spectrum of Fairall 9, a local intensively monitored ‘bare’ AGN (no significant intrinsic cold or warm absorption). We show that including relativistic corrections does make a difference even to these more complex models, but caution that the inferred black hole spin depends on the assumed nature and geometry of the accretion flow. Additionally, we make our model code publicly available, and name it RELAGN.

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S. Hagen and C. Done
Wed, 5 Apr 23
15/62

Comments: 8 Pages, 5 Figures, 4 Appendices. Submitted to MNRAS. Comments Welcome

Exploring thermal effects of the hadron-quark matter transition in neutron star mergers [HEAP]

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http://arxiv.org/abs/2304.01971


We study the importance of the thermal behavior of the hadron-quark phase transition in neutron star (NS) mergers. To this end, we devise a new scheme approximating thermal effects to supplement any cold, barotropic hybrid equation of state (EoS) model, i.e. two-phase EoS constructions with a hadronic regime and a phase of deconfined quark matter. The consideration of temperature-dependent phase boundaries turns out to be critical for a quantitative description of quark matter effects in NS mergers, since the coexistence phase can introduce a strong softening of the EoS at finite temperature, which is even more significant than the change of the EoS by the phase transition at T=0. We validate our approach by comparing to existing fully temperature-dependent EoS models and find a very good quantitative agreement of postmerger gravitational-wave (GW) features. Simulations with the commonly-used thermal ideal-gas approach exhibit sizable differences compared to full hybrid models implying that its use in NS merger simulations with quark matter is problematic. Our new scheme provides the means to isolate thermal effects of quark matter from the properties of the cold hybrid EoS and thus allows an assessment of the thermal behavior alone. We show that different shapes of the phase boundaries at finite temperature can have a large impact on the postmerger dynamics and GW signal for the same cold hybrid model. This finding demonstrates that postmerger GW emission contains important complementary information compared to properties extracted from cold stars. We also show by concrete examples that it is even possible for quark matter to only occur and thus be detectable in finite-temperature systems like merger remnants but not in cold NSs.

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S. Blacker, A. Bauswein and S. Typel
Wed, 5 Apr 23
16/62

Comments: 28 pages, 16 figures, submitted to Phys. Rev. D

Self-gravitating collapsing star and black hole spin-up in long gamma ray bursts [HEAP]

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http://arxiv.org/abs/2304.01342


Long Gamma Ray Bursts (GRBs) originate from the collapse of massive, rotating stars. We aim to model the process of stellar collapse in the scenario of a self-gravitating collapsing star. We account for the changes in Kerr metric induced by the growth of the black hole, accretion of angular momentum, as well as the self-gravity effect due to a large mass of the collapsing stellar core falling onto black hole in a very short time. We also investigate the existence of accretion shocks in the collapsar, and role of magnetic field in their propagation. We compute the time-dependent axially-symmetric General Relativistic magnetohydrodynamic model of a collapsing stellar core in the dynamical Kerr metric. We explore the influence of self-gravity in such star, where the newly formed black hole is increasing the mass, and changing its spin. The Kerr metric evolves according to the mass and angular momentum changes during the collapse. We parameterize the rotation inside the star, and account for the presence of large-scale poloidal magnetic field. For the set of the global parameters, such as the initial black hole spin, and initial content of specific angular momentum in the stellar envelope, we determine the evolution of black hole parameters (mass and spin) and we quantify the strength of the gravitational instability, variability timescales and amplitudes. We find that the role of the gravitational instability measured by the value of the Toomre parameter is relatively important in the innermost regions of the collapsing star. The character of accretion rate variability strongly depends on the assumption of self-gravity in the model, and is also affected by the magnetic field. Additional factors are initial spin and rotation of the stellar core.

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A. Janiuk, N. Dehsorkh and D. Krol
Wed, 5 Apr 23
21/62

Comments: 23 pages, 19 figures; submitted to A\&A

Reconstructing star formation rate for compact binary populations with Einstein telescope [HEAP]

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http://arxiv.org/abs/2304.01341


Einstein Telescope (ET) is a proposed third generation, wide-band gravitational wave (GW) detector. Given its improved detection sensitivity in comparison to the second generation detectors, it will be capable of exploring the universe with GWs up to very high redshifts. In this paper we present the algorithm to answer three main questions regarding the star formation rate density (SFR) (i) when did the formation terminate?, (ii) at what redshift does the SFR peak?, and finally (iii) what is the functional form of SFR at high redshift? for a given population. We present an algorithm to infer the functional form of SFR for different populations of compact binaries originating in stars from Population (Pop) I+II and Pop III, using ET as a single instrument. We show that the reconstruction of SFR is essentially independent of the time delay distributions up to $z \sim 14$ and the accuracy of the reconstruction strongly depends on the time delay distribution only at high redshifts of $z\gtrsim 14$. We define the termination redshift as the redshift where the SFR drops to 1\% of its peak value. In this analysis we constrain the peak of the SFR as a function of redshift and show that ET as a single instrument can distinguish the termination redshifts of different SFRs. The accurate estimate of the termination redshift depends on correctly modelling the tail of the time delay distribution representing delay time $\gtrsim 8$ Gyr.

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N. Singh, T. Bulik, K. Belczynski, et. al.
Wed, 5 Apr 23
22/62

Comments: 16 pages, 5+3 figures

An optimal envelope ejection efficiency for merging neutron stars [HEAP]

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http://arxiv.org/abs/2304.01949


We use the rapid binary stellar evolution code $\texttt{binary_c}$ to estimate the rate of merging neutron stars with numerous combinations of envelope ejection efficiency and natal kick dispersion. We find a peak in the local rate of merging neutron stars around $\alpha \approx 0.3$$-$$0.4$, depending on the metallicity, where $\alpha$ is the efficiency of utilising orbital energy to unbind the envelope. The peak height decreases with increasing electron-capture supernova kick dispersion $\sigma_\mathrm{ECSN}$. We explain the peak as a competition between the total number of systems that survive the common-envelope phase increasing with $\alpha$ and their separation, which increases with $\alpha$ as well. Increasing $\alpha$ reduces the fraction of systems that merge within a time shorter than the age of the Universe and results in different mass distributions for merging and non-merging double neutron stars. This offers a possible explanation for the discrepancy between the Galactic double neutron star mass distribution and the observed massive merging neutron star event GW190425. Within the $\alpha$$-$$\sigma_\mathrm{ECSN}$ parameter space that we investigate, the rate of merging neutron stars spans several orders of magnitude up to more than $1\times 10^{3} \, \mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$ and can be higher than the observed upper limit or lower than the observed lower limit inferred thus far from merging neutron stars detected by gravitational waves. Our results stress the importance of common-envelope physics for the quantitative prediction and interpretation of merging binary neutron star events in this new age of gravitational wave astronomy.

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A. Tanaka, A. Gilkis, R. Izzard, et. al.
Wed, 5 Apr 23
26/62

Comments: 16 pages, 10 figures, this is a pre-copyedited, author-produced version of an article accepted for publication in MNRAS

A novel prediction for secondary positrons and electrons in the Galaxy [HEAP]

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http://arxiv.org/abs/2304.01261


The Galactic flux of cosmic-ray (CR) positrons in the GeV to TeV energy range is very likely due to different Galactic components. One of these is the inelastic scattering of CR nuclei with the atoms of the interstellar medium. The precise amount of this component determines the eventual contribution from other sources. We present here a new estimation of the secondary CR positron flux by incorporating the latest results for the production cross sections of $e^\pm$ from hadronic scatterings calibrated on collider data. All the reactions for CR nuclei up to silicon scattering on both hydrogen and helium are included. The propagation models are derived consistently by fits on primary and secondary CR nuclei data. Models with a small halo size ($\leq 2$ kpc) are disfavored by the nuclei data although the current uncertainties on the beryllium nuclear cross sections may impact this result. The resulting positron flux shows a strong dependence on the Galactic halo. Within the most reliable propagation models, the positron flux matches the data for energies below 1 GeV. We verify that secondary positrons contribute less than $70\%$ of the data already above a few GeV, demonstrating that an excess of positrons is already present at very low energies. At larger energies, our predictions are below the data with the discrepancy becoming more pronounced. Our predictions are provided together with uncertainties due to propagation and hadronic cross sections. In addition to the predictions of positrons, we provide new predictions also for the secondary CR electron flux.

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M. Mauro, F. Donato, M. Korsmeier, et. al.
Wed, 5 Apr 23
33/62

Comments: 14 pages, 8 figures. Appendix adds 7 pages, 4 figures and 2 tables

The proto-neutron star inner crust in the liquid phase [HEAP]

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http://arxiv.org/abs/2304.01584


The crust of a neutron star is known to melt at a temperature that increases with increasing matter density, up to about $10^{10}$ K. At such high temperatures and beyond, the crustal ions are put into collective motion and the associated entropy contribution can affect both the thermodynamic properties and the composition of matter. We studied the importance of this effect in different thermodynamic conditions relevant to the inner crust of the proto-neutron star, both at beta equilibrium and in the fixed-proton-fraction regime. To this aim, we solved the hydrodynamic equations for an ion moving in an incompressible, irrotational, and non-viscous fluid, with different boundary conditions, thus leading to different prescriptions for the ion effective mass. We then employed a compressible liquid-drop approach in the one-component plasma approximation, including the renormalisation of the ion mass to account for the influence of the surrounding medium. We show that the cluster size is determined by the competition between the ion centre-of-mass motion and the interface properties, namely the Coulomb, surface, and curvature energies. In particular, including the translational free energy in the minimisation procedure can significantly reduce the optimal number of nucleons in the clusters and lead to an early dissolution of clusters in dense beta-equilibrated matter. On the other hand, we find that the impact of translational motion is reduced in scenarios where the proton fraction is assumed constant and is almost negligible on the inner-crust equation of state. Our results show that the translational degrees of freedom affect the equilibrium composition of beta-equilibrated matter and the density and pressure of the crust-core transition in a non-negligible way, highlighting the importance of its inclusion when modelling the finite-temperature inner crust of the (proto-)neutron star.

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H. Thi, A. Fantina and F. Gulminelli
Wed, 5 Apr 23
36/62

Comments: 14 pages, 13 figures, accepted for publication in Astronomy and Astrophysics

Close encounters of black hole – star binaries with stellar-mass black holes [HEAP]

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http://arxiv.org/abs/2304.01792


Dynamical interactions involving binaries play a crucial role in the evolution of star clusters and galaxies. We continue our investigation of the hydrodynamics of three-body encounters, focusing on binary black hole (BBH) formation, stellar disruption, and electromagnetic (EM) emission in dynamical interactions between a BH-star binary and a stellar-mass BH, using the moving-mesh hydrodynamics code {\small AREPO}. This type of encounters can be divided into two classes depending on whether the final outcome includes BBHs. This outcome is primarily determined by which two objects meet at the first closest approach. BBHs are more likely to form when the star and the incoming BH encounter first with an impact parameter smaller than the binary’s semimajor axis. In this case, the star is frequently disrupted. On the other hand, when the two BHs encounter first, frequent consequences are an orbit perturbation of the original binary or a binary member exchange. For the parameters chosen in this study, BBH formation, accompanied by stellar disruption, happens in roughly 1 out of 4 encounters. The close correlation between BBH formation and stellar disruption has possible implications for EM counterparts at the binary’s merger. The BH that disrupts the star is promptly surrounded by an optically and geometrically thick disk with accretion rates exceeding the Eddington limit. If the debris disk cools fast enough to become long-lived, EM counterparts can be produced at the time of the BBH merger.

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T. Ryu, R. Valli, R. Pakmor, et. al.
Wed, 5 Apr 23
37/62

Comments: 16 pages, 11 figures, 2 table. Submitted to MNRAS, comments welcome!

Pulse Profile Modeling of Thermonuclear Burst Oscillations I: The Effect of Neglecting Variability [HEAP]

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http://arxiv.org/abs/2304.01770


We study the effects of the time-variable properties of thermonuclear X-ray bursts on modeling their millisecond-period burst oscillations. We apply the pulse profile modeling technique that is being used in the analysis of rotation-powered millisecond pulsars by the Neutron Star Interior Composition Explorer (NICER) to infer masses, radii, and geometric parameters of neutron stars. By simulating and analyzing a large set of models, we show that overlooking burst time-scale variability in temperatures and sizes of the hot emitting regions can result in substantial bias in the inferred mass and radius. To adequately infer neutron star properties, it is essential to develop a model for the time variable properties or invest a substantial amount of computational time in segmenting the data into non-varying pieces. We discuss prospects for constraints from proposed future X-ray telescopes.

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Y. Kini, T. Salmi, A. Watts, et. al.
Wed, 5 Apr 23
42/62

Comments: Accepted for publication in MNRAS

Spectro-Polarimetric variability in the repeating fast radio burst source FRB 20180301A [HEAP]

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http://arxiv.org/abs/2304.01763


As the sample size of repeating fast radio bursts (FRBs) has grown, an increasing diversity of phenomenology has emerged. Through long-term multi-epoch studies of repeating FRBs, it is possible to assess which phenomena are common to the population and which are unique to individual sources. We present a multi-epoch monitoring campaign of the repeating FRB source 20180301A using the ultra-wideband low (UWL) receiver observations with Murriyang, the Parkes 64-m radio telescope. The observations covered a wide frequency band spanning approximately 0.7–4 GHz, and yielded the detection of 46 bursts. None of the repeat bursts displayed radio emission in the range of 1.8–4 GHz, while the burst emission peaked at 1.1 GHz. We discover evidence for secular trends in the burst dispersion measure, indicating a rate of $-2.7\pm0.2\,{\rm pc\,cm^{-3}\,yr^{-1}}$. We also found significant variation in the Faraday rotation measure of the bursts across the follow-up period, including evidence of a sign reversal. While a majority of bursts did not exhibit any polarization, those that did show a decrease in the linear polarization fraction as a function of frequency, consistent with spectral depolarization due to scattering observed in other repeating FRB sources. Surprisingly, no significant variation in the polarization position angles was found, which is in contrast with earlier measurements reported for the FRB source. We measure the burst rate and sub-pulse drift rate variation and compare them with the previous results. These novel observations, along with the extreme polarization properties observed in other repeating FRBs, suggest that a sub-sample of FRB progenitors possess highly dynamic magneto-ionic environments.

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P. Kumar, R. Luo, D. Price, et. al.
Wed, 5 Apr 23
56/62

Comments: 21 pages, 14 figures; submitted to MNRAS

Cosmic Cousins: Identification of a Subpopulation of Binary Black Holes Consistent with Isolated Binary Evolution [HEAP]

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http://arxiv.org/abs/2304.01288


Observations of gravitational waves (GWs) from merging compact binaries have become a regular occurrence. The continued advancement of the LIGO-Virgo-KAGRA (LVK) Collaboration detectors have now produced a catalog of over 90 such mergers, from which we can begin to uncover the formation history of merging compact binaries. In this work, we search for subpopulations in the LVK’s third gravitational wave transient catalog (GWTC-3) by incorporating discrete latent variables in the hierarchical Bayesian inference framework to probabilistically assign each BBH observation into separate categories associated with distinctly different population distributions. By incorporating formation channel knowledge within the mass and spin correlations found in each category, we find an over density of mergers with a primary mass of $\sim10 M_\odot$, consistent with isolated binary formation. This low-mass subpopulation has a spin magnitude distribution peaking at $a_\mathrm{peak}=0.16^{0.19}{-0.16}$, exhibits spins preferentially aligned with the binary’s orbital angular momentum, is constrained by $15^{+0.0}{-1.0}$ of our observations, and contributes $82\%^{+8.0\%}{-16\%}$ to the overall population of BBHs. Additionally, we find that the component of the mass distribution containing the previously identified $35M\odot$ peak has spins consistent with the $10M_\odot$ events, with $99\%$ of primary masses less than $m_{1,99\%} = 49^{+25}{-8.1} M\odot$, providing an estimate of the lower edge of the theorized pair instability mass gap. This work is a first step in gaining a deeper understanding of compact binary formation and evolution, and will provide more robust conclusions as the catalog of observations becomes larger.

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J. Godfrey, B. Edelman and B. Farr
Wed, 5 Apr 23
57/62

Comments: 14 pages, 6 figures, comments welcome

The High-Altitude Water Cherenkov (HAWC) Observatory in México: The Primary Detector [HEAP]

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http://arxiv.org/abs/2304.00730


The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analysis techniques build on experience of the Milagro experiment in using ground-based water Cherenkov detectors for gamma-ray astronomy. HAWC is located on the Sierra Negra volcano in M\’exico at an elevation of 4100 meters above sea level. The completed HAWC observatory principal detector (HAWC) consists of 300 closely spaced water Cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. The HAWC observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred GeV to several hundred TeV. However, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. This paper describes the characteristics of the HAWC main array and its hardware.

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H. Collaboration
Tue, 4 Apr 23
6/111

Comments: 39 pages, 14 Figures

Constraints on the localization volume of High Energy Neutrinos for galaxy-targetted electromagnetic followups [HEAP]

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http://arxiv.org/abs/2304.00831


High Energy Neutrino telescopes such as IceCube or KM3NeT issue public alerts describing the characteristics of possible astrophysical high energy neutrino events. This information, in particular the arrival direction and the associated uncertainty of the neutrino candidates, is used by observatories to search for possible electromagnetic counterparts. Such searches are complicated by the localization areas as high as tens of squared degrees or more and the absence of constraints on the distance or nature of the source, contrarily to gravitational wave alerts issued by instruments such as LIGO/Virgo. A method to derive a probable distance for the astrophysical source possibly associated to a HEN event is described, which can be used in a cross-match with galaxy catalogues to search for possible electromagnetic counterparts. This is intended as a guide for high energy neutrino followup campaigns.

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T. Pradier
Tue, 4 Apr 23
7/111

Comments: N/A

Flux-resolved spectro-polarimetric evolution of the X-ray pulsar Her~X-1 using IXPE [HEAP]

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http://arxiv.org/abs/2304.00889


We conduct a spectro-polarimetric study of the accreting X-ray pulsar Hercules X-1 using observations with the Imaging X-ray Polarimetry Explorer (IXPE). IXPE monitored the source in three different Epochs, sampling two Main-on and one Short-on state of the well-known super-orbital period of the source. We find that the 2-7 keV polarization fraction increases significantly from ~ 7-9 % in the Main-on state to ~ 15-19 % in the Short-on state, while the polarization angle remains more or less constant or changes slightly, ~ 47-59 degrees, in all three Epochs. The polarization degree and polarization angle are consistent with being energy-independent for all three Epochs. We propose that in the Short-on state, when the neutron star is partially blocked by the disk warp, the increase in the polarization fraction can be explained as a result of the preferential obstruction of one of the magnetic poles of the neutron star.

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A. Garg, D. Rawat, Y. Bhargava, et. al.
Tue, 4 Apr 23
21/111

Comments: 9 pages, 4 Figures, 1 Table, submitted in ApJL

A polarimetric-oriented X-ray stare at the accreting pulsar EXO 2030+375 [HEAP]

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http://arxiv.org/abs/2304.00925


Accreting X-ray pulsars (XRPs) are presumably ideal targets for polarization measurements, as their high magnetic field strength is expected to polarize the emission up to a polarization degree of ~80%. However, such expectations are being challenged by recent observations of XRPs with the Imaging X-ray Polarimeter Explorer (IXPE). Here we report on the results of yet another XRP, EXO 2030+375, observed with IXPE and contemporarily monitored with Insight-HXMT and SRG/ART-XC. In line with recent results obtained with IXPE for similar sources, analysis of the EXO 2030+375 data returns a low polarization degree of 0%-3% in the phase-averaged study and variation in the range 2%-7% in the phase-resolved study. Using the rotating vector model we constrain the geometry of the system and obtain a value for the magnetic obliquity of ~$60^{\circ}$. Considering also the estimated pulsar inclination of ~$130^{\circ}$, this indicates that the magnetic axis swings close to the observer line of sight. Our joint polarimetric, spectral and timing analysis hint to a complex accreting geometry where magnetic multipoles with asymmetric topology and gravitational light bending significantly affect the observed source behavior.

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C. Malacaria, J. Heyl, V. Doroshenko, et. al.
Tue, 4 Apr 23
22/111

Comments: Submitted to A&A

Three approaches for the classification of protoneutron star oscillation modes [HEAP]

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http://arxiv.org/abs/2304.00033


The future detection of gravitational waves (GWs) from a galactic core-collapse supernova will provide information on the physics inside protoneutron stars (PNS). In this work, we apply three different classification methods for the PNS non-radial oscillation modes: Cowling classification, Generalized Cowling Nomenclature (GCN), and a Classification Based on Modal Properties (CBMP). Using PNS models from $3$D simulations of core-collapse supernovae, we find that in the early stages of the PNS evolution, typically before $0.4$ seconds after the bounce, the Cowling classification is inconsistent, but the GCN and the CBMP provide complementary information that helps to understand the evolution of the modes. In the GCN, we note several avoided crossings as the mode frequencies evolve at early times, while the CBMP tracks the modes across the avoided crossings. We verify that the strongest emission of GWs by the PNS corresponds to the $f$-mode in the GCN, indicating that the mode trapping region alternates between the core and the envelope at each avoided crossing. At later times, approximately $0.4$ seconds after the bounce, the three classification methods present a similar description of the mode spectrum. We use our results to test universal relations for the PNS modes according to their classification and find that the behaviour of the universal relations for $f$- and $p$-modes is remarkably simple in the CBMP.

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M. Rodriguez, I. Ranea-Sandoval, C. Chirenti, et. al.
Tue, 4 Apr 23
24/111

Comments: 11 pages, 8 figures

Optical/UV Emission in the Tidal Disruption Event ASASSN-14li: Implications of Disc Modeling [HEAP]

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http://arxiv.org/abs/2304.00428


We predict late-time optical/UV emission from tidal disruption events (TDEs) from our slim accretion disc model \citep{Wen20} and explore the impact of the black hole mass $M_\bullet$, black hole spin $a_\bullet$, and accretion disc size. We use these synthetic spectra to successfully fit the multi-band \emph{Swift} observations of ASASSN-14li at >350 days, setting only the host galaxy extinction and outer disc radius as free parameters and employing the $M_\bullet$, $a_\bullet$, disc inclination, and disc accretion rates derived from fitting 10 epochs of ASASSN-14li’s X-ray spectra with the slim disc. To address the nature of the \emph{early}-time optical/UV emission, we consider two models: shock dissipation and reprocessing. We find that (1) the predicted late-time optical/UV colour (e.g., $u-w2$) is insensitive to black hole and disc parameters unless the disc spreads quickly; (2) a starburst galaxy extinction model is required to fit the data, consistent with ASASSN-14li’s post-starburst host; (3) surprisingly, the outer disc radius is $\approx$2$\times$ the tidal radius and $\sim$constant at late times, showing that viscous spreading is slow or non-existent; (4) the shock model can be self-consistent if $M_\bullet \lesssim 10^{6.75}$M$\odot$, i.e., on the low end of ASASSN-14li’s $M\bullet$ range ($10^{6.5-7.1}$M$\odot$; 1$\sigma$ CL); larger black hole masses require disruption of an unrealistically massive progenitor star; (5) the gas mass needed for reprocessing, whether by a quasi-static or an outflowing layer, can be $<0.5$M$\odot$, consistent with a (plausible) disruption of a solar-mass star.

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W. Sixiang, J. Peter, S. Nicholas, et. al.
Tue, 4 Apr 23
25/111

Comments: 15 pages, 10 figures. Accepted for publication in MNRAS

Searching for dark matter subhalos in the Fermi-LAT catalog with Bayesian neural networks [HEAP]

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http://arxiv.org/abs/2304.00032


About a third of the $\gamma$-ray sources detected by the Fermi Large Area Telescope (Fermi-LAT) remain unidentified, and some of these could be exotic objects such as dark matter subhalos. We present a search for these sources using Bayesian neural network classification methods applied to the latest 4FGL-DR3 Fermi-LAT catalog. We first simulate the gamma-ray properties of dark matter subhalos using models from N-body simulations and semi-analytical approaches to the subhalo distribution. We then assess the detectability of this sample in the 4FGL-DR3 catalog using the Fermi-LAT analysis tools. We train our Bayesian neural network to identify candidate dark matter subhalos among the unidentified sources in the 4FGL-DR3 catalog. Our results allow us to derive conservative bounds on the dark matter annihilation cross section by excluding unidentified sources classified as astrophysical-like by our networks. We estimate the number of candidate dark matter subhalos for different dark matter masses and provide a publicly available list for further investigation. Our bounds on the dark matter annihilation cross section are comparable to previous results and become particularly competitive at high dark matter masses.

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A. Butter, M. Krämer, S. Manconi, et. al.
Tue, 4 Apr 23
27/111

Comments: 31 pages, 14 figures

Measurement of the cosmic p+He energy spectrum from 46 GeV to 316 TeV with the DAMPE space mission [HEAP]

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http://arxiv.org/abs/2304.00137


Recent observations of the light component of the cosmic-ray spectrum have revealed unexpected features that motivate further and more precise measurements up to the highest energies. The Dark Matter Particle Explorer (DAMPE) is a satellite-based cosmic-ray experiment that is operational since December 2015, continuously collecting data on high-energy cosmic particles with very good statistics, energy resolution, and particle identification capabilities. In this work, the latest measurements of the energy spectrum of proton+helium in the energy range from 46 GeV to 316 TeV are presented. Among the most distinctive features of the spectrum, a spectral hardening at $\sim$600 GeV has been observed, along with a softening at $\sim$29 TeV measured with a 6.6$\sigma$ significance. Moreover, by measuring the energy spectrum up to 316 TeV, a strong link is established between space- and ground-based experiments, also suggesting the presence of a second hardening at $\sim$150 TeV.

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D. Collaboration
Tue, 4 Apr 23
30/111

Comments: submitted to PRL

TeV bayesian study of the extragalactic background light [HEAP]

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http://arxiv.org/abs/2304.00808


The extragalactic background light (EBL) is the aggregate of all optical and infrared emissions from thermal processes since the cosmic dark ages. While the integrated light of galaxies is expected to be the main contribution to the EBL, recent measurements beyond Pluto’s orbit from the New Horizon probe show a 4$\sigma$ excess in the optical band. This tension can be studied within observational gamma-ray cosmology, by reconstructing EBL-induced absorption features in the gamma-ray spectra of extragalactic sources at very-high energies (VHE, $E>100$ GeV). Gamma-ray studies of the EBL remain limited by the size of the spectral corpora and by the uncertainties on the shape of the spectra emitted at the sources. We developed a new analysis method that aims to tackle these limitations. Unlike existing studies, we employ a fully Bayesian framework, which allows us to remove arbitrary criteria for selecting intrinsic spectral models. Such an approach further enables marginalization over systematics of instrumental origin, such as the uncertainty on the energy scale of current-generation VHE observatories. In this contribution, we apply our method to the most extensive catalog of extragalactic VHE spectra to date, STeVECat. We present preliminary constraints on the energy density of the EBL at redshift $z=0$, obtained with 259 archival VHE spectra from 56 extragalactic sources with known redshift.

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L. Gréaux and J. Biteau
Tue, 4 Apr 23
32/111

Comments: N/A

Hydrogen-triggered X-ray Bursts from SAX J1808.4-3658? The Onset of Nuclear Burning [HEAP]

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http://arxiv.org/abs/2304.00104


We present a study of weak, thermonuclear X-ray bursts from the accreting millisecond X-ray pulsar SAX J1808.4-3658. We focus on a burst observed with the Neutron Star Interior Composition Explorer on 2019 August 9, and describe a similar burst observed with the Rossi X-ray Timing Explorer in 2005 June. These bursts occurred soon after outburst onset, $2.9$ and $1.1$ days, after the first indications of fresh accretion. We measure peak burst bolometric fluxes of $6.98 \pm 0.50 \times 10^{-9}$ and $1.54 \pm 0.10 \times 10^{-8}$ erg cm$^{-2}$ s$^{-1}$, respectively, which are factors of $\approx 30$ and $15$ less than the peak flux of the brightest, helium-powered bursts observed from this source. From spectral modeling we estimate accretion rates and accreted columns at the time of each burst. For the 2019 burst we estimate an accretion rate of $\dot M \approx 1.4-1.6 \times 10^{-10}$ $M_{\odot}$ yr$^{-1}$, and a column in the range $3.9-5.1 \times 10^7$ g cm$^{-2}$. For the 2005 event the accretion rate was similar, but the accreted column was half of that estimated for the 2019 burst. The low accretion rates, modest columns, and evidence for a cool neutron star in quiescence, suggest these bursts are triggered by thermally unstable CNO cycle hydrogen-burning. The post-burst flux level in the 2019 event appears offset from the pre-burst level by an amount consistent with quasi-stable hydrogen-burning due to the temperature-insensitive, hot-CNO cycle, further suggesting hydrogen-burning as the primary fuel source. This provides strong observational evidence for hydrogen-triggered bursts. We discuss our results in the context of previous theoretical modeling.

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S. Casten, T. Strohmayer and P. Bult
Tue, 4 Apr 23
37/111

Comments: 14 pages, 6 figures, 2 tables

On The Theory of Ring Afterglows [HEAP]

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http://arxiv.org/abs/2304.00044


Synchrotron and inverse Compton emission successfully explain the observed spectra of gamma-ray burst (GRB) afterglows. It is thought that most GRBs are products of extremely relativistic outflows and the afterglow marks the interaction of that ejecta with the surrounding matter. Faster decay of afterglow light curves at late times is indicative of non-spherical geometries, and are usually interpreted as evidence for jet geometry. Recent numerical simulations have shown that ring-like geometries are also permissible for relativistic outflows. We therefore extend the standard theory of afterglow evolution to ring geometries. An analytic prescription for the light curves and spectra produced by relativistic toroidal blast waves is presented. We compare these to their spherical and jet-like counterparts, and show that ring afterglows decay faster than spherical outflows but not as fast as jets.

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M. DuPont, A. MacFadyen and R. Sari
Tue, 4 Apr 23
38/111

Comments: N/A

Wave Mechanics, Interference, and Decoherence in Strong Gravitational Lensing [HEAP]

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http://arxiv.org/abs/2304.01202


Wave-mechanical effects in gravitational lensing have long been predicted, and with the discovery of populations of compact transients such as gravitational wave events and fast radio bursts, may soon be observed. We present an observer’s review of the relevant theory underlying wave-mechanical effects in gravitational lensing. Starting from the curved-spacetime scalar wave equation, we derive the Fresnel-Kirchoff diffraction integral, and analyze it in the eikonal and wave optics regimes. We answer the question of what makes interference effects observable in some systems but not in others, and how interference effects allow for complementary information to be extracted from lensing systems as compared to traditional measurements. We end by discussing how diffraction effects affect optical depth forecasts and lensing near caustics, and how compact, low-frequency transients like gravitational waves and fast radio bursts provide promising paths to open up the frontier of interferometric gravitational lensing.

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C. Leung, D. Jow, P. Saha, et. al.
Tue, 4 Apr 23
43/111

Comments: Comments and suggestions for additional references welcome

Origin of high-velocity ejecta and early red excess emission in the infant Type Ia supernova 2021aefx [HEAP]

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http://arxiv.org/abs/2304.00625


\object{SN 2021aefx} is a normal Type Ia Supernova (SN) with red excess emission over the first $\sim$ 2 days. We present detailed analysis of this SN using our high-cadence KMTNet multi-band photometry, spectroscopy, and publicly available data. We provide the first measurements of its epochs of explosion (MJD 59529.32 $\pm$ 0.16) as well as first light'' (MJD 59529.85 $\pm$ 0.55) associated with the main ejecta ${\rm{^{56}Ni}}$ distribution. This places our first detection of SN 2021aefx at $\sim -$0.5 hours sincefirst light”, indicating the presence of additional power sources. Our peak-spectrum confirms its Type Ia sub-classification as intermediate between Core-Normal and Broad-Line, and we estimate the ejecta mass to be $\sim$ 1.34 $M_{\odot}$. The pre-peak spectral evolution identifies fast-expanding material reaching $>$ 40,000 km s$^{-1}$ (the fastest ever observed in Type Ia SNe) and at least two distinct homologously-expanding ejecta components: (1) a normal-velocity (12,400 km s$^{-1}$) component consistent with the typical photospheric evolution of Chandrasekhar-mass ejecta; and (2) a high-velocity (23,500 km s$^{-1}$) component visible during the first $\sim$ 3.6 days post-explosion, which locates the component within the outer $<$ 16\% of the ejecta mass. Asymmetric, subsonic explosion processes producing a non-spherical photosphere provide an explanation for the simultaneous presence of the two components, as well as the red excess emission via a slight ${\rm{^{56}Ni}}$ enrichment in the outer $\sim$ 0.5\% of the ejecta mass. Our spectrum from 300 days post-peak advances the constraint against non-degenerate companions and further supports a near-Chandrasekhar-mass explosion origin. Off-center ignited delayed-detonations of Chandrasekhar-mass white dwarfs may be responsible for the observed features of SN 2021aefx in some normal Type Ia SNe.

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Y. Ni, D. Moon, M. Drout, et. al.
Tue, 4 Apr 23
47/111

Comments: Submitted for publication in ApJ. 29 pages, 14 figures, 4 tables

Identifying the Gamma-ray Emission of the Nearby Galaxy M83 [HEAP]

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http://arxiv.org/abs/2304.00229


We report on the detection of a gamma-ray source at the position of the nearby star-forming galaxy (SFG) M83, which is found from our analysis of 14 years of the data obtained with the Large Area Telescope (LAT) on-board {\it Fermi Gamma-ray Space Telescope (Fermi)}. The source is weakly detected, with a significance of $\sim 5\sigma$, and its emission can be described with an exponentially cutoff power law. At a distance of 4.61\,Mpc, the source’s gamma-ray luminosity is $\sim 1.4\times 10^{39}$\,erg\,s$^{-1}$, roughly along the correlation line between the \gr\ and IR luminosities determined for nearby SFGs. Because of the weak detection, the source spectrum can not be used for checking its similarity with those of other SFGs. Given the positional matches and the empirical expectation for gamma-ray emission from M83 due to the galaxy’s star-forming activity, we conclude that the gamma-ray source is the likely counterpart to m83. The detection thus adds another member to the group of approximately a dozen SFGs, whose \gr\ emissions mostly have a cosmic-ray origin.

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Y. Xing and Z. Wang
Tue, 4 Apr 23
48/111

Comments: 6 pages, 4 figures, 2 tables, submitted to ApJ

Reproducing the results for NICER observation of PSR J0030+0451 [HEAP]

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http://arxiv.org/abs/2304.01035


NASA’s Neutron Star Interior Composition Explorer (NICER) observed X-ray emission from the pulsar PSR J0030+0451 in 2018. Riley \textit{et al.} reported Bayesian parameter measurements of the mass and the radius of the star using pulse-profile modeling of the X-ray data. In this paper, we reproduce their result using the open-source software \textit{X-PSI} and the publicly available data. We reproduce the main result within the expected statistical error. We note the challenges we faced in reproducing the results. We demonstrate that not only that the analysis can be reproduced, it can also be reused in future works by changing the prior distribution for the radius, and by changing the sampler configuration. We find no significant change in the measurement of the mass and radius, demonstrating that the original result is robust to these changes. Finally, we provide a containerized working environment that facilitates third-party reproduction of the measurements of mass and radius of PSR J0030+0451 using the NICER observations.

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C. Afle, P. Miles, S. Caino-Lores, et. al.
Tue, 4 Apr 23
49/111

Comments: 12 pages, 4 figures, 2 tables

Significant cocoon emission and photosphere duration stretching in GRB 211211A: a burst from a neutron star – black hole merger [HEAP]

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http://arxiv.org/abs/2304.00893


The radiation mechanism (thermal photosphere or magnetic synchrotron) and the progenitor of gamma-ray burst (GRB) are under hot debate. Recently discovered, the prompt long-duration ($\sim$ 10 s, normally from the collapse of massive stars) property of GRB 211211A strongly conflicts with its association with a kilonova (normally from the merger of two compact objects, NS-NS, NS-BH, or NS-WD, duration $\lesssim$ 2 s). In this paper, we find the probability photosphere model with a structured jet can satisfactorily explain this peculiar long duration, through the duration stretching effect ($\sim$ 3 times) on the intrinsic longer ($\sim$ 3 s) duration of NS-BH (neutron star and black hole) merger, the observed empirical 2SBPL spectrum (with soft low-energy index $\alpha$ of $\sim$ -1) and its evolution. Also, much evidence of the NS-BH merger origin is found, especially the well fit of the afterglow-subtracted optical-NIR light curves by the significant thermal cocoon emission and the sole thermal red kilonova component. Finally, a convincing new explanation for the X-ray afterglow plateau is revealed.

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Y. Meng, X. Wang and Z. Liu
Tue, 4 Apr 23
52/111

Comments: 38 pages, 17 figures, 2 tables. A previous version was rejected after a peer review by Nature Astronomy (in September 2022). Resubmitted recently (adding new results on the NS-BH-merger evidence, the cocoon emission and the X-ray afterglow plateau)

IceCat-1: the IceCube Event Catalog of Alert Tracks [HEAP]

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http://arxiv.org/abs/2304.01174


We present a catalog of likely astrophysical neutrino track-like events from the IceCube Neutrino Observatory. IceCube began reporting likely astrophysical neutrinos in 2016 and this system was updated in 2019. IceCube began reporting likely astrophysical neutrinos in 2016 and this system was updated in 2019. The catalog presented here includes events that were reported in real-time since 2019, as well as events identified in archival data samples starting from 2011. We report 275 neutrino events from two selection channels as the first entries in the catalog, the IceCube Event Catalog of Alert Tracks, which will see ongoing extensions with additional alerts. The gold and bronze alert channels respectively provide neutrino candidates with 50\% and 30\% probability of being astrophysical, on average assuming an astrophysical neutrino power law energy spectral index of 2.19. For each neutrino alert, we provide the reconstructed energy, direction, false alarm rate, probability of being astrophysical in origin, and likelihood contours describing the spatial uncertainty in the alert’s reconstructed location. We also investigate a directional correlation of these neutrino events with gamma-ray and X-ray catalogs including 4FGL, 3HWC, TeVCat and Swift-BAT.

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R. Abbasi, M. Ackermann, J. Adams, et. al.
Tue, 4 Apr 23
56/111

Comments: 3 tables, 5 figures. See online version of the catalog on dataverse at this https URL

Investigating starburst-driven neutrino emission from galaxies in the Great Observatories All-Sky LIRG Survey [HEAP]

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http://arxiv.org/abs/2304.01020


We present a phenomenological framework for starburst-driven neutrino production via proton-proton collisions and apply it to (ultra-)luminous infrared galaxies (U/LIRGs) in the Great Observatories All-Sky LIRG Survey (GOALS). The framework relates the infrared luminosity of a GOALS galaxy, derived from consistently available Herschel Space Observatory data, to the expected starburst-driven neutrino flux. The model parameters that define this relation can be estimated from multi-wavelength data. We apply the framework in a case study to the LIRG NGC 3690 (Arp 299, Mrk 171) and compare the obtained neutrino fluxes to the current sensitivity of the IceCube Neutrino Observatory. Using our framework, we also conclude that the neutrino emission in the LIRG NGC 1068, recently presented as the first steady IceCube neutrino point source, cannot be explained by a starburst-driven scenario and is therefore likely dominated by the active galactic nucleus in this galaxy. In addition to the single-source investigations, we also estimate the diffuse starburst-driven neutrino flux from GOALS galaxies and the total LIRG population over cosmic history.

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Y. Merckx, P. Correa, K. Vries, et. al.
Tue, 4 Apr 23
58/111

Comments: 26 pages, 11 figures

Reanalysis of the Systematic Uncertainties in Cosmic-Ray Antiproton Flux [HEAP]

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http://arxiv.org/abs/2304.00760


Recent studies on cosmic rays (CRs) have reported the possibility of an excess in the antiproton flux around $10-20$ GeV. However, the associated systematic uncertainties have impeded the interpretation of these findings. In this study, we conduct a global Bayesian analysis to constrain the propagation parameters and evaluate the CR antiproton spectrum, while comprehensively accounting for uncertainties associated with interstellar CR propagation, production cross sections for antiprotons and other secondaries, and the charge and energy dependent effects of solar modulation. We establish that the most recent AMS-02 $\bar{p}$ spectrum is in agreement with a pure secondary origin. Based on this, we establish upper limits on dark matter (DM) annihilation. We also determine that the AMS-02 data favors the empirical hadronic interaction models over phenomenological ones. Finally, we find that the latest AMS-02 antiproton data from 2011 to 2018 disfavors the antiproton excess at $\mathcal{O}$(10) GeV and the corresponding DM interpretation that can simultaneously account for the Galactic Center excess in the gamma-ray observation.

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X. Lv, X. Bi, K. Fang, et. al.
Tue, 4 Apr 23
74/111

Comments: 11 pages, 7 figures

Distinguishing X-ray Stars vs. AGN through ML [HEAP]

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http://arxiv.org/abs/2304.00158


Modern X-ray telescopes have detected hundreds of thousands of X-ray sources in the universe. However, current methods to classify these sources using the X-ray data themselves suffer problems – detailed X-ray spectroscopy of individual sources is too time-consuming, while hardness ratios often lack accuracy, and can be difficult to use effectively. These methods fail to use the power of X-ray CCD detectors to identify X-ray emission lines and distinguish line-dominated spectra (from chromospherically active stars, supernova remnants, etc.) from continuum-dominated ones (e.g., compact objects or active galactic nuclei [AGN]). In this paper, we probe the use of artificial neural networks (ANN) in differentiating Chandra spectra of young stars in the Chandra Orion Ultradeep Project (COUP) survey from AGN in the Chandra Deep Field South (CDFS) survey. We use these surveys to generate 100,000 artificial spectra of stars and AGN and train our ANN models to separate the two kinds of spectra. We find that our methods reach an accuracy of approx. 92% in classifying simulated spectra of moderate-brightness objects in typical exposures, but their performance slightly decreases on the observed COUP and CDFS spectra (approx. 91%), due in large part to the relatively high background of these long-exposure datasets. We also investigate the performance of our methods with changing properties of the spectra such as the net source counts, the relative contribution of background, the absorption column of the sources, etc. We conclude that these methods have substantial promise for application to large X-ray surveys.

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P. Hebbar and C. Heinke
Tue, 4 Apr 23
78/111

Comments: 21 pages, 21 figures, accepted for publication in ApJ

QPEs from impacts between the secondary and a rigidly precessing accretion disc in an EMRI system [HEAP]

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http://arxiv.org/abs/2304.00775


X-ray quasi-periodic eruptions (QPEs) represent a recently discovered example of extreme X-ray variability associated with supermassive black holes. Those are high amplitude bursts recurring every few hours and detected in the soft X-ray band from the nuclei of nearby galaxies whose optical spectra lack the broad emission lines typically observed in unobscured active galaxies. The physical origin of this new X-ray variability phenomenon is still unknown, and several theoretical models have been presented. However, no attempt has been made so far to account for the varying QPE recurrence time and luminosity in individual sources, nor for the diversity of the QPE phenomenology in the different known erupters. We present a semi-analytical model based on an Extreme Mass Ratio Inspiral (EMRI) system where the secondary intersects, along its orbit, a rigidly precessing accretion disc surrounding the primary. We assume QPEs to be due to emission from an adiabatically expanding, initially optically thick gas cloud expelled from the disc plane at each impact. We produce synthetic X-ray light curves that are compared with X-ray data from four QPE sources: GSN 069, eRO-QPE1, eRO-QPE2 and RX J1301.9+2747. Our model reproduces the diversity of QPE properties between the considered objects well, and is also able to account naturally for the varying QPE amplitudes and recurrence times in individual sources. Future implementations will enable us to refine the match with the data, and to estimate precisely the system parameters making also use of multi-epoch QPE data. We briefly discuss the nature of the secondary object as well as possible implications of our findings for the EMRI population at large.

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A. Franchini, M. Bonetti, A. Lupi, et. al.
Tue, 4 Apr 23
82/111

Comments: 10 pages, 7 figures, submitted to A&A

Investigating the gamma-ray burst from decaying MeV-scale axion-like particles produced in supernova explosions [HEAP]

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http://arxiv.org/abs/2304.01060


We investigate the characteristics of the gamma-ray signal following the decay of MeV-scale Axion-Like Particles (ALPs) coupled to photons which are produced in a Supernova (SN) explosion. This analysis is the first to include the production of heavier ALPs through the photon coalescence process, enlarging the mass range of ALPs that could be observed in this way and giving a stronger bound from the observation of SN 1987A. Furthermore, we present a new analytical method for calculating the predicted gamma-ray signal from ALP decays. With this method we can rigorously prove the validity of an approximation that has been used in some of the previous literature, which we show here to be valid only if all gamma rays arrive under extremely small observation angles (i.e. very close to the line of sight to the SN). However, it also shows where the approximation is not valid, and offers an efficient alternative to calculate the ALP-induced gamma-ray flux in a general setting when the observation angles are not guaranteed to be small. We also estimate the sensitivity of the Fermi Large Area Telescope (Fermi-LAT) to this gamma-ray signal from a future nearby SN and show that in the case of a non-observation the current bounds on the ALP-photon coupling $ g_{a\gamma} $ are strengthened by about an order of magnitude. In the case of an observation, we show that it may be possible to reconstruct the product $ g_{a\gamma}^2 m_a $, with $ m_a $ the mass of the ALP.

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E. Müller, F. Calore, P. Carenza, et. al.
Tue, 4 Apr 23
83/111

Comments: 28 pages, 9 figures

Unravelling optical and X-ray properties of the disc-dominated intermediate polar IGR J15094-6649 [HEAP]

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http://arxiv.org/abs/2304.00099


We present analyses of an Intermediate Polar, IGR J15094-6649, based on the archival optical data obtained from the Transiting Exoplanet Survey Satellite (TESS) and X-ray data obtained from the Suzaku, NuSTAR, and Neil Gehrels Swift Observatory (Swift). Present analysis confirms and refines the previously reported spin period of IGR J15094-6649 as 809.49584$\pm$0.00075 s. Clear evidence of a beat period of 841.67376$\pm$0.00082 s is found during the long-term TESS optical observations, which was not evident in the earlier studies. The dominance of X-ray and optical spin pulse unveils the disc-fed dominance accretion, however, the presence of an additional beat frequency indicates that part of the accreting material also flows along the magnetic field lines. The energy-dependent spin pulsations in the low (< 10 keV) energy band are due to the photoelectric absorption in the accretion flow. However, the complex absorbers may be responsible to produce low amplitude spin modulations via Compton scattering in the hard ( > 10 keV) energy band and indicate that the height of the X-ray emitting region may be negligible. The observed double-humped X-ray profiles with a pronounced dip are indicative of the photoelectric absorption in the intervening accretion stream. Analysis of the X-ray spectra reveals the complexity of the X-ray emission, being composed of multi-temperature plasma components with a soft excess, reflection, and suffers from strong absorption.

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A. Joshi, N. Rawat, A. Schwope, et. al.
Tue, 4 Apr 23
104/111

Comments: 15 pages, 10 figures, and 5 Tables, Accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:2112.06270

STeVECat, the Spectral TeV Extragalactic Catalog [HEAP]

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http://arxiv.org/abs/2304.00835


The three main collaborations operating the current generation of imaging atmospheric Cherenkov telescopes (IACTs: H.E.S.S., MAGIC, VERITAS) publish their gamma-ray data in different formats and repositories. Extragalactic sources are highly variable at very-high energies (VHE, $E>100\,$GeV), and a unified repository would enable joint analyses of collections of extragalactic VHE spectra. To this aim, we have developed the Spectral TeV Extragalactic Catalog, STeVECat, which gathers high-level products of IACT observations from 1992 to 2021. We selected all publications in journals referenced in TeVCat that presented archival spectra with at least two points. We compiled the corresponding spectral data and formatted them following the convention adopted in available public repositories (GammaCat and VTSCat). In addition to spectral points with associated physical units, we provide meta-data featuring observation periods, livetime, excess counts over background and significance, as well as the coordinates, types and redshifts of the sources whenever available. STeVECat combines observations from 173 journal publications, compared to 72 in the previous reference compilation of extragalactic gamma-ray spectra (Biteau \& Williams, 2015). STeVECat is the most extensive set of VHE extragalactic spectra collected so far, with 403 spectra from 73 sources. The full catalog can readily be loaded with GammaPy, the Science Analysis Tool selected by the Cherenkov Telescope Array Observatory. Our compilation efforts enable population studies of extragalactic gamma-ray sources, studies of the GeV-TeV connection, and studies of absorption on the extragalactic background light.

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L. Gréaux, J. Biteau, T. Hassan, et. al.
Tue, 4 Apr 23
105/111

Comments: N/A

Polarization Formalism for ALP-induced X-ray Emission from Magnetars [HEAP]

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http://arxiv.org/abs/2303.17641


Missions like NASA’s Imaging X-ray Polarimetry Explorer (IXPE) are poised to provide an unprecedented view of the Universe in polarized X-rays. Polarization probes physical anisotropies, a fact exploited by particle physicists to look for the anisotropic $a\boldsymbol{E}\cdot\boldsymbol{B}$ operator in the axion-like-particle (ALP) Lagrangian. Such studies have typically focused on polarization in the radio and microwaves, through local or cosmic birefringence effects. To such polarization studies we add X-rays emanating from magnetars — a class of neutron stars with near-critical strength magnetic fields — that are important targets for IXPE. ALPs produced in the neutron star core convert to X-rays in the magnetosphere; such X-rays are polarized along the direction parallel to the dipolar magnetic field at the point of conversion. We develop the full theoretical formalism for ALP-induced polarization in the presence of dipolar magnetic fields. For uncorrelated photon and ALP production mechanisms, we completely disentangle the ALP contributions to the Stokes parameters in terms of the ALP intensity, the ALP-to-photon conversion probability, and the ALP-induced birefringence. In the proper limit, our results demonstrate that the inclusion of ALPs suppresses the observed degree of circular polarization compared to its pure astrophysical value. Our results can also be used to impose limits on ALP couplings with IXPE polarization data from magnetars 4U 0142+61 and 1RXS J170849.0-400910, the subject of upcoming work.

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J. Fortin and K. Sinha
Mon, 3 Apr 23
3/53

Comments: 1+22 pages, 2 figures

Could compact stars in globular clusters constrain dark matter? [HEAP]

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http://arxiv.org/abs/2303.18009


The dark matter content of globular clusters, highly compact gravity-bound stellar systems, is unknown. It is also generally unknowable, due to their mass-to-light ratios typically ranging between 1$-$3 in solar units, accommodating a dynamical mass of dark matter at best comparable to the stellar mass. That said, recent claims in the literature assume densities of dark matter around 1000 GeV/cm$^3$ to set constraints on its capture and annihilation in white dwarfs residing in the globular cluster M4, and to study a number of other effects of dark matter on compact stars. Motivated by these studies, we use measurements of stellar kinematics and luminosities in M4 to look for a dark matter component via a spherical Jeans analysis; we find no evidence for it, and set the first empirical limits on M4’s dark matter distribution. Our density upper limits, a few $\times \ 10^4$ GeV/cm$^3$ at 1 parsec from the center of M4, do not negate the claims (nor confirm them), but do preclude the use of M4 for setting limits on non-annihilating dark matter kinetically heating white dwarfs, which require at least $10^5$ GeV/cm$^3$ densities. The non-robust nature of globular clusters as dynamical systems, combined with evidence showing that they may originate from molecular gas clouds in the absence of dark matter, make them unsuitable as laboratories to unveil dark matter’s microscopic nature in current or planned observations.

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R. Garani, N. Raj and J. Reynoso-Cordova
Mon, 3 Apr 23
6/53

Comments: 10 pages revtex4 + references, 3 figures, 1 table