Category Archives: High Energy Astrophysical Phenomena

On the nature of compact stars determined by gravitational waves, radio-astronomy, x-ray emission and nuclear physics [HEAP]

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http://arxiv.org/abs/2303.18133


We investigate the question of the nature of compact stars, considering they may be neutron stars or hybrid stars containing a quark core, within the present constraints given by gravitational waves, radio-astronomy, X-ray emissions from millisecond pulsars and nuclear physics. A Bayesian framework is used to combine together all these constraints and to predict tidal deformabilities and radii for a 1.4~M$\odot$ compact star. We find that present gravitation wave and radio-astronomy data favors asy-stiff EoS compatible with nuclear physics and that GW170817 waveform is best described for binary hybrid stars. In addition, this data favors stiff quark matter, independently of the nuclear EoS. Combining this result with constraints from X-ray observation supports the existence of canonical $1.4$~M$\odot$ mass hybrid star, with a radius predicted to be $R_{1.4}=12.02(8)$~km.

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H. Güven, J. Margueron, K. Bozkurt, et. al.
Mon, 3 Apr 23
20/53

Comments: 5 pages, 3 figures

Neutrino cooled disk in post-merger system studied via numerical GR MHD simulation with a composition-dependent equation of state [HEAP]

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http://arxiv.org/abs/2303.18129


The code HARM_COOL, a conservative scheme for relativistic magnetohydrodynamics, is being developed in our group and works with a tabulated equation of state of dense matter. This EOS can be chosen and used during dynamical simulation, instead of the simple ideal gas one. In this case, the inversion scheme between the conserved and primitive variables is not a trivial task. In principle, the code needs to solve numerically five coupled non-linear equations at every time-step. The 5-D recovery schemes were originally implemented in HARM and worked accurately for a simple polytropic EOS which has an analytic form. Our current simulations support the composition-dependent EOS, formulated in terms of rest-mass density, temperature and electron fraction. In this proceeding, I discuss and compare several recovery schemes that have been included in our code. I also present and discuss their convergence tests. Finally, I show set of preliminary results of a numerical simulation, addressed to the post-merger system formed after the binary neutron stars (BNS) coalescence.

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A. Janiuk
Mon, 3 Apr 23
30/53

Comments: 9 pages, 3 figures. To appear in the Proceedings of the 8th Conference of the Polish Society for Relativity, POTOR-8 (Warsaw, September 19-23, 2022)

ChatGPT scores a bad birdie in counting gravitational-wave chirps [HEAP]

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http://arxiv.org/abs/2303.17628


How many gravitational-wave observations from compact object mergers have we seen to date? This seemingly simple question has a surprisingly complex answer that even ChatGPT struggles to answer. To shed light on this, we present a database with the literature’s answers to this question. We find values spanning 67-100 for the number of detections from double compact object mergers to date, emphasizing that the exact number of detections is uncertain and depends on the chosen data analysis pipeline and underlying assumptions. We also review the number of gravitational-wave detections expected in the coming decades with future observing runs, finding values up to millions of detections per year in the era of Cosmic Explorer and Einstein Telescope. We present a publicly available code to visualize the detection numbers, highlighting the exponential growth in gravitational-wave observations in the coming decades and the exciting prospects of gravitational-wave astrophysics. See this http URL We plan to keep this database up-to-date and welcome comments and suggestions for additional references.

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F. Broekgaarden
Mon, 3 Apr 23
52/53

Comments: 1 April submission, with fun videos for visualizing the landscape of gravitational waves! (they are awesome!) See this http URL

Classifying a frequently repeating fast radio burst, FRB 20201124A, with unsupervised machine learning [HEAP]

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http://arxiv.org/abs/2303.17133


Fast radio bursts (FRBs) are astronomical transients with millisecond timescales. Although most of the FRBs are not observed to repeat, a few of them are detected to repeat more than hundreds of times. There exist a large variety of physical properties among these bursts, suggesting heterogeneous mechanisms of FRBs. In this paper, we conduct a categorisation on the extremely frequently repeating FRB 20201124A with the assistance of machine learning, as such techniques have the potential to use subtle differences and correlations that humans are unaware of to better classify bursts. The research is carried out by applying the unsupervised Uniform Manifold Approximation and Projection (UMAP) model on the FRB 20201124A data provided by Five-hundred-meter Aperture Spherical radio Telescope (FAST). The algorithm eventually categorises the bursts into three clusters. In addition to the two categories in previous work based on waiting time, a new way for categorisation has been found. The three clusters are either high energy, high frequency, or low frequency, reflecting the distribution of FRB energy and frequency. Importantly, a similar machine learning result is found in another frequently repeating FRB20121102A, implying a common mechanism among this kind of FRB. This work is one of the first steps towards the systematical categorisation of the extremely frequently repeating FRBs.

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B. Chen, T. Hashimoto, T. Goto, et. al.
Fri, 31 Mar 23
8/70

Comments: 8 pages, 9 figures, accepted for publication in MNRAS. For summary video, please see this https URL&list=PLOpYDs2PkYlYIiKDjDz6r6aKXcXdJZXYb&index=14&ab_channel=NCHUAstronomy

Constraining ultralight dark matter using the Fermi-LAT Pulsar Timing Array [HEAP]

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http://arxiv.org/abs/2303.17545


Ultralight dark matter (ULDM) is proposed as a theoretical candidate of dark matter particles with masses of approximately $10^{-22}$ eV. The interactions between ULDM particles and standard model particles would cause variations in pulse arrival times of the pulsars, which makes the pulsar timing array (PTA) can be used to indirectly detect ULDM. In this work, we use the gamma-ray PTA composed of 29 millisecond pulsars observed by the Fermi Large Area Telescope (Fermi-LAT) to test four ultralight dark matter effects, including gravitational effects for generalized ULDM with different Spin-0/1, the fifth-force coupling effect of Dark Photon and the modified gravitational effect of the Spin-2 ULDM. The gamma-ray pulsar timing is not affected by the ionized interstellar medium and suffers relatively simple noises, unlike that of the radio band. No significant signals of ULDM are found based on the Fermi-LAT PTA for all four kinds of ULDM models. Constraints on ULDM parameters are set with the 95% confidence level, which provides a complementary check of the non-detection of ULDM for radio PTAs and direct detection experiments.

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Z. Xia, T. Tang, X. Huang, et. al.
Fri, 31 Mar 23
12/70

Comments: 9 pages, 4 figures, 2 tables

Silicon K-edge Dust Properties of Neutron Star Low-mass X-ray Binaries [HEAP]

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http://arxiv.org/abs/2303.17465


The dust properties of the line-of-sight materials in neutron star low-mass X-ray binaries (LMXBs) can be probed by X-ray observations and laboratory experiments. We use a Markov chain Monte Carlo (MCMC) method to conduct a spectral analysis of Chandra ACIS-S/HETG archival data of a sample of LMXBs, including GX 5-1 and GX 13+1. Our MCMC-based analysis puts constraints on the Si K-edge dust properties of the outflowing disk winds in this sample. Further X-ray observations of other LMXBs will help us better understand the grain features of dense outflows and accretion flows in neutron star binary systems.

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A. Danehkar
Fri, 31 Mar 23
19/70

Comments: 3 pages, 2 figures, presented as a poster at the IAU Symposium 363 “Neutron Star Astrophysics at the Crossroads: Magnetars and the Multimessenger Revolution”, Virtual, Italy, November 2021

Comparing Early Evolution of Flames in X-ray Bursts in Two and Three Dimensions [HEAP]

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http://arxiv.org/abs/2303.17077


We explore the early evolution of flame ignition and spreading on the surface of a neutron star in three-dimensions, in the context of X-ray bursts. We look at the nucleosynthesis and morphology of the burning front and compare to two-dimensional axisymmetric simulations to gauge how important a full three-dimensional treatment of the flame is for the early dynamics. Finally, we discuss the progress toward full-star resolved flame simulations.

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M. Zingale, K. Eiden and M. Katz
Fri, 31 Mar 23
21/70

Comments: submitted to ApJ

Gravitational Wave Eigenfrequencies from Neutrino-Driven Core-Collapse Supernovae [HEAP]

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http://arxiv.org/abs/2303.16962


Core-collapse supernovae are predicted to produce gravitational waves (GWs) that may be detectable by Advanced LIGO/Virgo. These GW signals carry information from the heart of these catacylsmic events, where matter reaches nuclear densities. Recent studies have shown that it may be possible to infer properties of the proto-neutron star (PNS) via gravitational waves generated by hydrodynamic perturbations of the PNS. However, we lack a comprehensive understanding of how these relationships may change with the properties of core-collapse supernovae. In this work, we build a self-consistent suite of over 1000 exploding core-collapse supernovae from a grid of progenitor masses and metallicities combined with six different nuclear equations of state. Performing a linear perturbation analysis on each model, we compute the resonant gravitational-wave frequencies of the PNS, and we motivate a time-agnostic method for identifying characteristic frequencies of the dominant gravitational-wave emission. From this, we identify two characteristic frequencies, of the early- and late-time signal, that measure the surface gravity of the cold remnant neutron star, and simultaneously constrain the hot nuclear equation of state. However, we find that the details of the core-collapse supernova model, such as the treatment of gravity or the neutrino transport, and whether it explodes, noticeably change the magnitude and evolution of the PNS eigenfrequencies.

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N. Wolfe, C. Frohlich, J. Miller, et. al.
Fri, 31 Mar 23
23/70

Comments: 27 pages, 11 figures, submitted to ApJ

A Bright First Day for Tidal Disruption Event [HEAP]

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http://arxiv.org/abs/2303.17443


Stream-stream collision may be an important pre-peak energy dissipation mechanism in tidal disruption events (TDEs). We perform local three-dimensional radiation hydrodynamic simulations in a wedge geometry including the gravity to study stream self-crossing, with emphasis on resolving the collision and following the subsequent outflow. We find that the collision can contribute to pre-peak optical emissions by converting $\gtrsim5\%$ of stream kinetic energy to radiation, yielding prompt emission of $\sim10^{42-44}\rm erg~s^{-1}$. The radiative efficiency is sensitive to stream mass fallback rates, and strongly depends on the downstream gas optical depth. Even for a sub-Eddington ($10\%$) mass fallback rate, the strong radiation pressure produced in the collision can form a local super-Eddington region near the collision site, where a fast, aspherical outflow is launched. Higher mass fallback rate usually leads to more optically-thick outflow and lower net radiative efficiency. For $\dot{M}\gtrsim0.1\dot{M}_{\rm Edd}$, the estimated photosphere size of the outflow can expand by one to two orders of magnitudes reaching $\sim10^{14}\rm cm$. The average gas temperature at this photospheric surface is a few $\times10^{4}$K, roughly consistent with inferred pre-peak photosphere properties for some optical TDEs. We find that the dynamics is sensitive to collision angle and collision radius, but the radiative efficiency or outflow properties show more complex dependency than is often assumed in ballistic models.

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X. Huang, S. Davis and Y. Jiang
Fri, 31 Mar 23
26/70

Comments: 18 pages, 18 figures, Submitted to ApJ. Comments are welcomed and appreciated!

The FAST Galactic Plane Pulsar Snapshot Survey: II. Discovery of 76 Galactic rotating radio transients and their enigma [HEAP]

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http://arxiv.org/abs/2303.17279


We are carrying out the GPPS survey by using the FAST, the most sensitive systematic pulsar survey in the Galactic plane. In addition to about 500 pulsars already discovered through normal periodical search, we report here the discovery of 76 new transient radio sources with sporadic strong pulses, detected by using the newly developed module for a sensitive single pulse search. Their small DM values suggest that they all are the Galactic RRATs. More radio pulses have been detected from 26 transient radio sources but no periods can be found due to a limited small number of pulses from all FAST observations. The following-up observations show that 16 transient sources are newly identified as being the prototypes of RRATs with a period already determined from more detected sporadic pulses, 10 sources are extremely nulling pulsars, and 24 sources are weak pulsars with sparse strong pulses. On the other hand, 48 previously known RRATs have been detected by the FAST. Except for 1 RRAT with four pulses detected in a session of five minute observation and 4 RRATs with only one pulse detected in a session, sensitive FAST observations reveal that 43 RRATs are just generally weak pulsars with sporadic strong pulses or simply very nulling pulsars, so that the previously known RRATs always have an extreme emission state together with a normal hardly detectable weak emission state. This is echoed by the two normal pulsars J1938+2213 and J1946+1449 with occasional brightening pulses. Though strong pulses of RRATs are very outstanding in the energy distribution, their polarization angle variations follow the polarization angle curve of the averaged normal pulse profile, suggesting that the predominant sparse pulses of RRATs are emitted in the same region with the same geometry as normal weak pulsars.

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D. Zhou, J. Han, J. Xu, et. al.
Fri, 31 Mar 23
28/70

Comments: Accepted for publication in RAA

A hard look at the X-ray spectral variability of NGC 7582 [HEAP]

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http://arxiv.org/abs/2303.17473


NGC 7582 (z = 0.005264; D = 22.5 Mpc) is a highly variable, changing-look AGN. In this work, we explore the X-ray properties of this source using XMM-Newton and NuSTAR archival observations in the 3-40 keV range, from 2001 to 2016. NGC 7582 exhibits a long-term variability between observations but also a short-term variability in two observations that has not been studied before. To study the variability, we perform a time-resolved spectral analysis using a phenomenological model and a physically-motivated model (uxclumpy). The spectral fitting is achieved using a nested sampling Monte Carlo method. uxclumpy enables testing various geometries of the absorber that may fit AGN spectra. We find that the best model is composed of a fully covering clumpy absorber. From this geometry, we estimate the velocity, size and distance of the clumps. The column density of the absorber in the line of sight varies from Compton-thin to Compton-thick between observations. Variability over the timescale of a few tens of kilo-seconds is also observed within two observations. The obscuring clouds are consistent with being located at a distance not larger than 0.6 pc, moving with a transverse velocity exceeding $\sim 700$ km s$^{-1}$. We could put only a lower limit on the size of the obscuring cloud being larger than $10^{13}$ cm. Given the sparsity of the observations, and the limited exposure time per observation available, we cannot determine the exact structure of the obscuring clouds. The results are broadly consistent with comet-like obscuring clouds or spherical clouds with a non-uniform density profile.

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M. Lefkir, E. Kammoun, D. Barret, et. al.
Fri, 31 Mar 23
29/70

Comments: 14 pages, 12 figures, accepted for publication in MNRAS

The Morphology and Dynamics of Relativistic Jets with Relativistic Equation of State [HEAP]

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http://arxiv.org/abs/2303.17323


We study the effect of plasma composition on the dynamics and morphology of the relativistic astrophysical jets. Our work is based on a relativistic total variation diminishing (TVD) simulation code. We use a relativistic equation of state in the simulation code which accounts for the thermodynamics of a multispecies plasma which is a mixture of electrons, positrons, and protons. To study the effect of plasma composition we consider various jet models. These models are characterized by the same injection parameters, same jet kinetic luminosity, and the same Mach numbers. The evolution of these models shows that the plasma composition affects the jet head propagation speed, the structure of the jet head, and the morphology despite fixing the initial parameters. We conclude that the electron-proton jets are the slowest and show more pronounced turbulent structures in comparison to other plasma compositions. The area and locations of the hot-spots also depend on the composition of jet plasma. Our results also show that boosting mechanisms are also an important aspect of multi-dimensional simulations which are also influenced by the change in composition.

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R. Joshi and I. Chattopadhyay
Fri, 31 Mar 23
41/70

Comments: Accepted for publication in ApJ, 13 pages and 9 figures

Tests of Classical Gravity with Radio Pulsars [HEAP]

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http://arxiv.org/abs/2303.17185


Tests of gravity are important to the development of our understanding of gravitation and spacetime. Binary pulsars provide a superb playground for testing gravity theories. In this chapter we pedagogically review the basics behind pulsar observations and pulsar timing. We illustrate various recent strong-field tests of the general relativity (GR) from the Hulse-Taylor pulsar PSR~B1913+16, the double pulsar PSR~J0737$-$3039, and the triple pulsar PSR~J0337+1715. We also overview the inner structure of neutron stars (NSs) that may influence some gravity tests, and have used the scalar-tensor gravity and massive gravity theories as examples to demonstrate the usefulness of pulsar timing in constraining specific modified gravity theories. Outlooks to new radio telescopes for pulsar timing and synergies with other strong-field gravity tests are also presented.

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Z. Hu, X. Miao and L. Shao
Fri, 31 Mar 23
42/70

Comments: 39 pages, 8 figures; Invited chapter to the forthcoming book “Recent Progress on Gravity Tests”, Springer Singapore, (Eds) Cosimo Bambi and Alejandro Cardenas-Avendano

Soft Gamma-Ray Spectral and Time evolution of the GRB 221009A: prompt and afterglow emission with INTEGRAL/IBIS-PICsIT [HEAP]

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http://arxiv.org/abs/2303.16943


The gamma-ray burst (GRB) 221009A, with its extreme brightness, has provided the opportunity to explore GRB prompt and afterglow emission behavior on short time scales with high statistics. In conjunction with detection up to very high-energy gamma-rays, studies of this event shed light on the emission processes at work in the initial phases of GRBs emission. Using INTEGRAL/IBIS’s soft gamma-ray detector, PICsIT (200-2600 keV), we studied the temporal and spectral evolution during the prompt phase and the early afterglow period. We found a “flux-tracking” behavior with the source spectrum “softer” when brighter. However the relationship between the spectral index and the flux changes during the burst. The PICsIT light curve shows afterglow emission begins to dominate at ~ T0 + 630s and decays with a slope of 1.6 +/- 0.2, consistent with the slopes reported at soft X-rays.

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J. Rodi and P. Ubertini
Fri, 31 Mar 23
49/70

Comments: 6 pages, 4 figures, A&A Accepted

Constraining the dark matter contribution of $γ$ rays in Cluster of galaxies using Fermi-LAT data [HEAP]

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http://arxiv.org/abs/2303.16930


Clusters of galaxies are the largest gravitationally-bound systems in the Universe. Their dynamics are dominated by dark matter (DM), which makes them among the best targets for indirect DM searches. We analyze 12 years of data collected by the Fermi Large Area Telescope (Fermi-LAT) in the direction of 49 clusters of galaxies selected for their proximity to the Earth and their high X-ray flux, which makes them the most promising targets. We first create physically motivated models for the DM density around each cluster considering different assumptions for the substructure distribution. Then we perform a combined search for a $\gamma$-ray signal in the {\it Fermi}-LAT data between 500 MeV and 1 TeV. We find a signal of $\gamma$ rays potentially associated with DM that is at a statistical significance of $2.5\sigma-3.0\sigma$ when considering a slope for the subhalo mass distribution $\alpha=1.9$ and minimum mass of $M_{\rm{min}}=10^{-6}$ $M_{\odot}$. The best-fit DM mass and annihilation cross-sections for a $b\bar{b}$ annihilation channel are $m_{\chi}=40-60$ GeV and $\langle \sigma v \rangle = (2-4) \times 10^{-25}$ cm$^3$/s. When we consider $\alpha=2.0$ and $M_{\rm{min}}=10^{-9}$ $M_{\odot}$, the best-fit of the cross section reduces to $\langle \sigma v \rangle = (4-10) \times 10^{-26}$ cm$^3$/s. For both DM substructure models there is a tension between the values of $\langle \sigma v \rangle$ that we find and the upper limits obtained with the non-detection of a $\gamma$-ray flux from Milky Way dwarf spheroidal galaxies. This signal is thus more likely associated with $\gamma$ rays produced in the intracluster region by cosmic rays colliding with gas and photon fields.

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M. Mauro, J. Pérez-Romero, M. Sánchez-Conde, et. al.
Fri, 31 Mar 23
56/70

Comments: 27 Pages, 13 Figures. Accepted for publication in the PRD journal

I Murdered Conan O'Brien and Nobody Will Ever Know — an exercise in inference sabotage [HEAP]

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http://arxiv.org/abs/2303.17400


I employ an optimization-based inference methodology together with an Ising model, in an intentionally ineffectual manner, to get away with murdering an obstreperous scientific collaborator. The antics of this collaborator, hereafter “Conan O’Brien,” were impeding the publication of an important manuscript. With my tenure date looming, I found myself desperate. Luckily, I study inference, a computational means to find a solution to a physical problem, based on available measurements (say, a dead body) and a dynamical model assumed to give rise to those measurements (a murderer). If the measurements are insufficient and/or the model is incomplete, one obtains multiple “degenerate” solutions to the problem. Degenerate solutions are all equally valid given the information available, and thus render meaningless the notion of one “correct” solution. Typically in scientific research, degeneracy is undesirable. Here I describe the opposite situation: a quest to create degenerate solutions in which to cloak myself. Or even better: to render measurements incompatible with a solution in which I am the murderer. Moreover, I show how one may sabotage an inference procedure to commit an untraceable crime. I sit here now, typing victoriously, a free woman. Because you won’t believe me anyway. And even if you do, you’ll never prove a thing.

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E. Armstrong
Fri, 31 Mar 23
57/70

Comments: 10 pages, 3 figures, 2 tables

Chaotic Gas Accretion by Black Holes Embedded in AGN Discs as Cause of Low-spin Signatures in Gravitational Wave Events [HEAP]

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http://arxiv.org/abs/2303.17097


Accretion discs around super-massive black holes (SMBH) not only power active galactic nuclei (AGNs), but also host single and binary embedded stellar-mass black holes (EBHs) that grow rapidly from gas accretion. The merger of these EBHs provides a promising mechanism for the excitation of some gravitational wave events observed by LIGO-Virgo, especially those with source masses considerably larger than isolated stellar-mass black hole binaries. In addition to their mass and mass-ratio distribution, their hitherto enigmatic small spin-parameters chi_effective carry important clues and stringent constraints on their formation channels and evolutionary pathways. Here we show that, between each coalescence, the typical rapid spin of the merged EBHs is suppressed by their subsequent accretion of gas from a turbulent environment, due to its ability to randomize the flow’s spin orientation with respect to that of the EBHs on an eddy-turnover timescale. This theory provides supporting evidence for the prolificacy of EBH mergers and suggests that their mass growth may be dominated by gas accretion rather than their coalescence in AGN discs.

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Y. Chen and D. Lin
Fri, 31 Mar 23
58/70

Comments: accepted by MNRAS, 11 pages, 8 figures

GRB-SN Association within the Binary-Driven Hypernova Model [HEAP]

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http://arxiv.org/abs/2303.16902


The observations of Ic supernovae (Ic/SNe) occurring after the prompt emission of long gamma-ray bursts (GRBs) are addressed within the binary-driven hypernova (BdHN) model. The GRBs originate from a binary composed of a $\sim 10~M_\odot$ carbon-oxygen (CO) star and a companion neutron star (NS). We assume these same progenitors originate the Ic/SN. The binary evolution depends strongly on the binary period, $P_{\rm bin}$. The trigger, given by the CO core collapse, for $P_{\rm bin}$ of up to a few hours leads to an Ic/SN with a fast-spinning NS ($\nu$NS) at its center. For $P_{\rm bin} \sim 4$–$5$ min, BdHN I occur with energies $10^{52}$–$10^{54}$ erg, a contribution by the black hole (BH) created by the NS companion collapse, originates the Mev/GeV radiations. The $\sim$~1 millisecond $\nu$NS originates, by synchrotron radiation, the X-ray afterglow. For $P_{\rm bin} \sim 10$~min, BdHN II occurs with energies of $10^{50}$–$10^{52}$~erg. For $P_{\rm bin} \sim$ hours, BdHN III occurs with energies below $10^{50}$~erg. The $1$–$1000$ ms $\nu$NS, in all BdHNe, originates the X-ray afterglow by synchrotron emission. The SN Ic follows an independent evolution, becoming observable by the nickel decay after the GRB prompt emission. We report $24$ Ic/SNe associated with BdHNe; their optical peak luminosity and their time of occurrence are similar and independent of the associated GRBs. We give four examples of BdHNe and their associated hypernovae. For the first time, we approach new physical processes in BdHNe, identifying seven episodes and their signatures in their spectra.

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Y. Aimuratov, L. Becerra, C. Bianco, et. al.
Fri, 31 Mar 23
59/70

Comments: Submitted on January 17, 2023

Constraining fundamental nuclear physics parameters using neutron star mass-radius measurements I: Nucleonic models [HEAP]

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http://arxiv.org/abs/2303.17518


Measurements of neutron star mass and radius or tidal deformability deliver unique insight into the equation of state (EOS) of cold dense matter. EOS inference is very often done using generalized parametric or non-parametric models which deliver no information on composition. In this paper we consider a microscopic nuclear EOS model based on a field theoretical approach. We show that current measurements from NICER and gravitational wave observations constrain primarily the symmetric nuclear matter EOS. We then explore what could be delivered by measurements of mass and radius at the level anticipated for future large-area X-ray timing telescopes. These should be able to place very strong limits on the symmetric nuclear matter EOS, in addition to constraining the nuclear symmetry energy that determines the proton fraction inside the neutron star.

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C. Huang, G. Raaijmakers, A. Watts, et. al.
Fri, 31 Mar 23
60/70

Comments: submitted to MNRAS

X-ray polarimetry of X-ray pulsar X Persei: another orthogonal rotator? [HEAP]

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http://arxiv.org/abs/2303.17325


X Persei is a persistent low-luminosity X-ray pulsar of period of $\sim$835 s in a Be binary system. The field strength at the neutron star surface is not known precisely, but indirect signs indicate a magnetic field above $10^{13}$ G, which makes the object one of the most magnetized known X-ray pulsars. Here we present the results of observations X Persei performed with the Imaging X-ray Polarimetry Explorer (IXPE). The X-ray polarization signal was found to be strongly dependent on the spin phase of the pulsar. The energy-averaged polarization degree in 3-8 keV band varied from several to $\sim$20 per cent over the pulse with a positive correlation with the pulsed X-ray flux. The polarization angle shows significant variation and makes two complete revolutions during the pulse period resulting in nearly nil pulse-phase averaged polarization. Applying the rotating vector model to the IXPE data we obtain the estimates for the rotation axis inclination and its position angle on the sky as well as for the magnetic obliquity. The derived inclination is close to the orbital inclination reported earlier for X Persei. The polarimetric data imply a large angle between the rotation and magnetic dipole axes, which is similar to the result reported recently for the X-ray pulsar GRO J1008$-$57. After eliminating the effect of polarization angle rotation over the pulsar phase using the best-fitting rotating vector model, the strong dependence of the polarization degree with energy was discovered with its value increasing from 0% at $\sim$2 keV to 30% at 8 keV.

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A. Mushtukov, S. S.Tsygankov, J. Poutanen, et. al.
Fri, 31 Mar 23
64/70

Comments: 11 pages, 7 figures, submitted to MNRAS

Thermal instability as a constraint for warm X-ray corona in AGN [HEAP]

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http://arxiv.org/abs/2303.17384


Context. Warm corona is a possible explanation for Soft X-ray Excess in Active Galactic Nuclei (AGN). This paper contains self consistent modeling of both: accretion disk with optically thick corona, where the gas is heated by magneto-rotational instability dynamo (MRI), and cooled by radiation which undergoes free-free absorption and Compton scattering. Aims. We determine the parameters of warm corona in AGN using disk-corona structure model that takes into account magnetic and radiation pressure. We aim to show the role of thermal instability (TI) as a constraint for warm, optically thick X-ray corona in AGN. Methods. With the use of relaxation code, the vertical solution of the disk driven by MRI together with radiative transfer in hydrostatic and radiative equilibrium is calculated, which allows us to point out how TI affects the corona for wide range of global parameters. Results. We show that magnetic heating is strong enough to heat upper layers of the accretion disk atmosphere, which form the warm corona covering the disk. Magnetic pressure does not remove TI caused by radiative processes operating in X-ray emitting plasma. TI disappears only in case of accretion rates higher than 0.2 of Eddington, and high magnetic field parameter $\alpha_{\rm B}$ > 0.1. Conclusions. TI plays the major role in the formation of the warm corona above magnetically driven accretion disk in AGN. The warm, Compton cooled corona, responsible for soft X-ray excess, resulted from our model has typical temperature in the range of 0.01 – 2 keV and optical depth even up to 50, which agrees with recent observations.

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D. Gronkiewicz, A. Różańska, P. Petrucci, et. al.
Fri, 31 Mar 23
70/70

Comments: N/A

A bright megaelectronvolt emission line in $γ$-ray burst GRB 221009A [HEAP]

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http://arxiv.org/abs/2303.16223


The highly variable and energetic pulsed emission of a long gamma-ray burst (GRB) is thought to originate from local, rapid dissipation of kinetic or magnetic energy within an ultra-relativistic jet launched by a newborn compact object, formed during the collapse of a massive star. The spectra of GRB pulses are best modelled by power-law segments, indicating the dominance of non-thermal radiation processes. Spectral lines in the X-ray and soft $\gamma$-ray regime for the afterglow have been searched for intensively, but never confirmed. No line features ever been identified in the high energy prompt emission. Here we report the discovery of a highly significant ($> 6 \sigma$) narrow emission feature at around $10$ MeV in the brightest ever GRB 221009A. By modelling its profile with a Gaussian, we find a roughly constant width $\sigma \sim 1$ MeV and temporal evolution both in energy ($\sim 12$ MeV to $\sim 6$ MeV) and luminosity ($\sim 10^{50}$ erg/s to $\sim 2 \times 10^{49}$ erg/s) over 80 seconds. We interpret this feature as a blue-shifted annihilation line of relatively cold ($k_\mathrm{B}T\ll m_\mathrm{e}c^2$) electron-positron pairs, which could have formed within the jet region where the brightest pulses of the GRB were produced. A detailed understanding of the conditions that can give rise to such a feature could shed light on the so far poorly understood GRB jet properties and energy dissipation mechanism.

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M. Ravasio, O. Salafia, G. Oganesyan, et. al.
Thu, 30 Mar 23
8/66

Comments: Submitted

Fluxes and spectral indices of rare and abundant cosmic ray nuclei according to the NUCLEON space experiment [HEAP]

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http://arxiv.org/abs/2303.16539


In this paper the dependence of the spectra of cosmic ray nuclei on the charges of nuclei was studied, according to the data of the NUCLEON space experiment. First, we studied the dependence of the spectral index of magnetic rigidity spectra on the charge for abundant nuclei. Secondly, for the charge range $Z=9\div20$, the differences in the total spectra of rare odd and abundant even nuclei were studied. Using the GALPROP package, the inverse problem of CR propagation from a source (near supernova) to an observer was solved, a component-by-component spectrum in the source was reconstructed, and it was shown that a systematic change in the spectral index in the source exist. It is supposed that this change may be interpreted as incomplete ionization of cosmic rays at the stage of acceleration in the supernova remnant shock. The ratio of the total spectra of magnetic rigidity for low-abundance odd and abundant even nuclei from the charge range $Z=9\div20$ is obtained, and it was shown that the spectra of odd rare nuclei are harder than the stpectra of abundat even nuclei in the rigidity range 300–10000~GV.

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I. Kudryashov, A. Turundaevskiy, D. Karmanov, et. al.
Thu, 30 Mar 23
23/66

Comments: 7 pages 4 figures, accepted in Bulletin of the Russian Academy of Sciences: Physics V.87(7), 2023

Expectations for Fast Radio Bursts in Neutron Star-Massive Star binaries [HEAP]

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http://arxiv.org/abs/2303.16770


Recent observations of a small sample of repeating Fast Radio Bursts (FRBs) have revealed a periodicity in their bursting activity that may be suggestive of a binary origin for the modulation. We set out to explore the scenario where a subset of repeating FRBs originates in binary systems hosting a highly energetic neutron star and a massive companion star, akin to $\gamma$-ray binaries and young High-Mass X-ray Binaries. Firstly, we specifically focus on the host galaxy properties and binary formation rates. Subsequently, we investigate the expected evolution of the rotation and dispersion measure in this scenario, the predicted birth-site offsets, and the origin of the persistent radio emission observed in a subset of these systems. The host galaxies for repeating FRBs favour the formation of neutron star-massive star binary systems but any conclusive evidence will require future discoveries and localizations of FRBs. The birth rate of high-mass X-ray binaries, used as a proxy for all considered binaries, significantly exceeds the estimated rate of FRBs, which can be explained if only a small subset of these systems produce FRBs. We show that under simple assumptions, we can reproduce the DM and RM evolution that is seen in a subset of repeating FRBs. We also discuss the possibility of detecting a persistent radio source associated with the FRB due to an intra-binary shock between companion star wind and either the pulsar wind or giant magnetar flares. The observed long-term luminosity stability of the Persistent Radio Sources is most consistent with a giant flare-powered scenario. However, this explanation is highly dependent on the magnetic field properties of the neutron star. With these explorations, we have aimed to provide a framework to discuss future FRB observations in the context of neutron star-massive star binary scenarios.

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K. Rajwade and J. Eijnden
Thu, 30 Mar 23
24/66

Comments: 15 pages, 7 figures, 2 appendices, accepted for publication in A&A. Abstract truncated to fit the word limit on arXiv

Convolutional neural network search for long-duration transient gravitational waves from glitching pulsars [HEAP]

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http://arxiv.org/abs/2303.16720


Machine learning can be a powerful tool to discover new signal types in astronomical data. We here apply it to search for long-duration transient gravitational waves triggered by pulsar glitches, which could yield physical insight into the mostly unknown depths of the pulsar. Current methods to search for such signals rely on matched filtering and a brute-force grid search over possible signal durations, which is sensitive but can become very computationally expensive. We develop a method to search for post-glitch signals on combining matched filtering with convolutional neural networks, which reaches similar sensitivities to the standard method at false-alarm probabilities relevant for practical searches, while being significantly faster. We specialize to the Vela glitch during the LIGO-Virgo O2 run, and set upper limits on the gravitational-wave strain amplitude from the data of the two LIGO detectors for both constant-amplitude and exponentially decaying signals.

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L. Modafferi, R. Tenorio and D. Keitel
Thu, 30 Mar 23
28/66

Comments: 19 pages, 9 figures. Comments welcome

Study of the X-ray Pulsar IGR J21343+4738 based on NuSTAR, Swift, and SRG data [HEAP]

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http://arxiv.org/abs/2303.16645


We present the results of our study of the X-ray pulsar IGR J21343+4738 based on NuSTAR, Swift, and SRG observations in the wide energy range 0.3 – 79 keV. The absence of absorption features in the energy spectra of the source, both averaged and phase-resolved ones, has allowed us to estimate the upper and lower limits on the magnetic field of the neutron star in the binary system, $B<2.5\times10^{11}$G and $B>3.4 \times 10^{12}$G, respectively. The spectral and timing analyses have shown that IGR J21343+4738 has all properties of a quasi-persistent X-ray pulsar with a pulsation period of $322.71\pm{0.04}$s and a luminosity $L_{x} \simeq3.3$ $\times10^{35}$erg s$^{-1}$. The analysis of the long-term variability of the object in X-rays has confirmed the possible orbital period of the binary system $\sim 34.3$ days previously detected in the optical range.

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A. Gorban, S. Molkov, A. Lutovinov, et. al.
Thu, 30 Mar 23
30/66

Comments: 8 pages, 4 figures, 1 table

Spin-induced offset stream self-crossing shocks in tidal disruption events [HEAP]

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http://arxiv.org/abs/2303.16230


Tidal disruption events occur when a star is disrupted by a supermassive black hole, resulting in an elongated stream of gas that partly falls back to pericenter. Due to apsidal precession, the returning stream may collide with itself, leading to a self-crossing shock that launches an outflow. If the black hole spins, this collision may additionally be affected by Lense-Thirring precession that can cause an offset between the two stream components. We study the impact of this effect on the outflow properties by carrying out local simulations of collisions between offset streams. As the offset increases, we find that the geometry of the outflow becomes less spherical and more collimated along the directions of the incoming streams, with less gas getting unbound by the interaction. However, even the most grazing collisions we consider significantly affect the trajectories of the colliding gas, likely promoting subsequent strong interactions near the black hole and rapid disc formation. We analytically compute the dependence of the offset to stream width ratio, finding that even slowly spinning black holes can cause both strong and grazing collisions. We propose that the deviation from outflow sphericity may enhance the self-crossing shock luminosity due to a reduction of adiabatic losses, and cause significant variations of the efficiency at which X-ray radiation from the disc is reprocessed to the optical band depending on the viewing angle. These potentially observable features hold the promise of constraining the black hole spin from tidal disruption events.

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T. Jankovič, C. Bonnerot and A. Gomboc
Thu, 30 Mar 23
33/66

Comments: 14 pages, 11 figures, submitted to MNRAS. Movies from the simulations are available at this https URL Comments welcome!”

Flavor conversions with energy-dependent neutrino emission and absorption [HEAP]

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http://arxiv.org/abs/2303.16453


Fast neutrino flavor conversions (FFCs) and collisional flavor instabilities (CFIs) potentially affect the dynamics of core-collapse supernovae (CCSNe) and binary neutron star mergers (BNSMs). Under the assumption of homogeneous neutrinos, we investigate effects of neutrino emission and absorption (EA) by matters through both single and multi-energy numerical simulations with physically motivated setup. In our models, FFCs dominate over CFIs in the early phase, while EA secularly and significantly give impacts on flavor conversions. They facilitate angular swaps, or the full exchange between electron neutrinos ($\nu_e$) and heavy-leptonic neutrinos ($\nu_x$). As a result, the number density of $\nu_x$ becomes more abundant than the case without EA, despite the fact that the isotropization by EA terminates the FFCs earlier. In the later phase, the system approaches new asymptotic states characterized by EA and CFIs, in which rich energy-dependent structures also emerge. Multi-energy effects sustain FFCs and the time evolution of the flavor conversion becomes energy dependent, which are essentially in line with effects of the isoenergetic scattering studied in our previous paper. We also find that $\nu_x$ in the high-energy region convert into $\nu_e$ via flavor conversions and then they are absorbed through charged current reactions, exhibiting the possibility of new path of heating matters.

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C. Kato, H. Nagakura and M. Zaizen
Thu, 30 Mar 23
35/66

Comments: 18 pages, 17 figures, submitted to PRD

The jet apparent motion and central engine study of Fermi blazars [HEAP]

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http://arxiv.org/abs/2303.16383


The study of blazar jet has been performed for several decades via the VLBI technique, while its generation and propagation stay unclear. In the present work, we compiled a sample of 407 VLBI detected \textit{Fermi} blazars (VFBs) and studied the correlations between apparent velocity (${\rm log}\,\beta_{\rm app}$) and jet/accretion disk properties. We found a positive correlation between $\gamma$-ray luminosity (${\rm log}\,L_{\rm \gamma}$) and ${\rm log}\,\beta_{\rm app}$, the correlation suggests that the apparent motion of jet knot is related to the jet power.

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H. Xiao, J. Zhu, J. Fan, et. al.
Thu, 30 Mar 23
37/66

Comments: 11 pages, 7 figures, 3 tables

Update on the indication of a mass-dependent anisotropy above $10^{18.7}\,$eV in the hybrid data of the Pierre Auger Observatory [HEAP]

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http://arxiv.org/abs/2303.16336


We test for an anisotropy in the mass of arriving cosmic-ray primaries associated with the galactic plane. The sensitivity to primary mass is obtained through the depth of shower maximum, $X_{\rm max}$, extracted from hybrid events measured over a 14-year period at the Pierre Auger Observatory. The sky is split into distinct on- and off-plane regions using the galactic latitude of each arriving cosmic ray to form two distributions of $X_{\rm max}$, which are compared using an Anderson-Darling 2-samples test. A scan over roughly half of the data is used to select a lower threshold energy of $10^{18.7}\,$eV and a galactic latitude splitting at $|b| = 30^\circ$, which are set as a prescription for the remaining data. With these thresholds, the distribution of $X_{\rm max}$ from the on-plane region is found to have a $9.1 \pm 1.6^{+2.1}{-2.2}\,$g$\,$cm$^-2$ shallower mean and a $5.9\pm2.1^{+3.5}{-2.5}\,$g$\,$cm$^-2$ narrower width than that of the off-plane region and is observed in all telescope sites independently. These differences indicate that the mean mass of primary particles arriving from the on-plane region is greater than that of those from the off-plane region. Monte Carlo studies yield a $5.9\times10^{-6}$ random chance probability for the result in the independent data, lowering to a $6.0\times10^{-7}$ post-penalization random chance probability when the scanned data is included. Accounting for systematic uncertainties leads to an indication for anisotropy in mass composition above $10^{18.7}\,$eV with a $3.3\,\sigma$ significance. Furthermore, the result has been newly tested using additional FD data recovered from the selection process. This test independently disfavors the on- and off-plane regions being uniform in composition at the $2.2\,\sigma$ level, which is in good agreement with the expected sensitivity of the dataset used for this test.

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Eric Mayotte
Thu, 30 Mar 23
52/66

Comments: Proceedings of the 6th International Symposium on Ultra High Energy Cosmic Rays (UHECR 2022), Oct 3-7, 2022, Gran Sasso Science Institute, L’Aquila, Italy. Accepted for publications in EPJ Web of Conferences series

Determining electron column density fluctuations in a dominant scattering region using pulsar scintillation [HEAP]

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http://arxiv.org/abs/2303.16338


Density fluctuations in the ionised interstellar medium have a profound effect on radio pulsar observations, through angular scattering, intensity scintillations, and small changes in time delays from dispersion. Here we show that it is possible to recover the variations in dispersive delays that originate from a dominant scattering region using measurements of the dynamic spectrum of intensity scintillations, provided that the pulsar velocity and scattering region location are known. We provide a theoretical framework for the technique, which involves estimating the phase gradient from the dynamic spectra and integrating that gradient to obtain phase variations. It can be used to search for “extreme scattering events” (ESEs) in pulsars for which precision dispersion delay measurements are not otherwise possible, or to separate true dispersion variations from apparent variability caused by frequency-dependent pulse shape changes. We demonstrate that it works in practice by recovering an ESE in PSR J1603$-$7202, which is known from precision dispersion delay measurements from pulsar timing. For this pulsar, we find that the phase gradients also track the long-term variations in electron column density observed by pulsar timing, indicating that the column density variations and the scattering are dominated by the same thin scattering screen. We identify a sudden increase in the scintillation strength and magnitude of phase gradients over $\sim$days in 2010, indicating a compact structure. A decrease in the electron density in 2012 was associated with persistent phase gradients and preceded a period of decreased scintillation strength and an absence of scintillation arcs.

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D. Reardon and W. Coles
Thu, 30 Mar 23
54/66

Comments: 9 pages, 7 figures, Accepted for publication in MNRAS

High-energy synchrotron flares powered by strongly radiative relativistic magnetic reconnection: 2D and 3D PIC simulations [HEAP]

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http://arxiv.org/abs/2303.16643


The time evolution of high-energy synchrotron radiation generated in a relativistic pair plasma energized by reconnection of strong magnetic fields is investigated with two- and three-dimensional (2D and 3D) particle-in-cell (PIC) simulations. The simulations in this 2D/3D comparison study are conducted with the radiative PIC code OSIRIS, which self-consistently accounts for the synchrotron radiation reaction on the emitting particles, and enables us to explore the effects of synchrotron cooling. Magnetic reconnection causes compression of the plasma and magnetic field deep inside magnetic islands (plasmoids), leading to an enhancement of the flaring emission, which may help explain some astrophysical gamma-ray flare observations. Although radiative cooling weakens the emission from plasmoid cores, it facilitates additional compression there, further amplifying the magnetic field $B$ and plasma density~$n$, and thus partially mitigating this effect. Novel simulation diagnostics utilizing 2D histograms in the $n\mbox{-}B$ space are developed and used to visualize and quantify the effects of compression. The $n\mbox{-}B$ histograms are observed to be bounded by relatively sharp power-law boundaries marking clear limits on compression. Theoretical explanations for some of these compression limits are developed, rooted in radiative resistivity or 3D kinking instabilities. Systematic parameter-space studies with respect to guide magnetic field, system size, and upstream magnetization are conducted and suggest that stronger compression, brighter high-energy radiation, and perhaps significant quantum electrodynamic (QED) effects such as pair production, may occur in environments with larger reconnection-region sizes and higher magnetization, particularly when magnetic field strengths approach the critical (Schwinger) field, as found in magnetar magnetospheres.

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K. Schoeffler, T. Grismayer, D. Uzdensky, et. al.
Thu, 30 Mar 23
55/66

Comments: 31 pages, 23 figures

EMRI + TDE = QPE: Periodic X-ray Flares from Star-Disk Collisions in Galactic Nuclei [HEAP]

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http://arxiv.org/abs/2303.16231


Roughly half of the quasi-periodic eruption (QPE) sources in galactic nuclei exhibit a remarkably regular alternating “long-short” pattern of recurrence times between consecutive flares. In support of previous suggestions, we show that a main-sequence star (brought into the nucleus as an extreme mass-ratio inspiral; EMRI) which passes twice per orbit through the accretion disk of the supermassive black hole (SMBH) on a mildly eccentric inclined orbit, each time shocking and ejecting optically-thick gas clouds above and below the midplane (akin to dual “supernovae”), naturally reproduces the luminosities, durations, and spectral temperatures of observed QPE flares. Similar to supernova shock break-out from a compact star, inefficient photon production in the collision debris renders the QPE emission much harder than the blackbody temperature, enabling the Comptonized spectrum to stick out from the softer quiescent disk spectrum. Destruction of the star via mass ablation typically limits the lifetime of QPE emission to decades, precluding a long-lived AGN as the source of the gaseous disk. By contrast, a tidal disruption event (TDE) naturally provides a transient gaseous disk on the requisite radial scale, with a rate sufficiently high relative to the EMRI inward migration rate, that a significant fraction of TDEs should host a QPE. This picture is consistent with the X-ray TDE observed several years prior to the QPE emission from GSN 069. Remarkably, a second TDE-like flare was observed from this event, starting immediately after detectable QPE activity ceased; this accretion event could plausibly result from the (partial or complete) destruction of the QPE-generating star triggered by runaway mass-loss. Our model can also be applied to black hole-disk collisions, such as those proposed to generate quasi-periodic flares in the candidate SMBH binary OJ 287.

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I. Linial and B. Metzger
Thu, 30 Mar 23
57/66

Comments: 21 pages, 4 figures, 2 tables

General-relativistic simulations of the formation of a magnetized hybrid star [HEAP]

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http://arxiv.org/abs/2303.16820


Strongly magnetized neutron stars are popular candidates for producing detectable electromagnetic and gravitational-wave signals. A rapid density increase in a neutron star core could also trigger the phase transition from hadrons to deconfined quarks and form a hybrid star. This formation process could release a considerable amount of energy in the form of gravitational waves and neutrinos. Hence, the formation of a magnetized hybrid star is an interesting scenario for detecting all these signals. These detections may provide essential probes for the magnetic field and composition of such stars. Thus far, a dynamical study of the formation of a magnetized hybrid star has yet to be realized. Here, we investigate the formation dynamics and the properties of a magnetized hybrid star through dynamical simulations. We find that the maximum values of rest-mass density and magnetic field strength increase slightly and these two quantities are coupled in phase during the formation. We then demonstrate that all microscopic and macroscopic quantities of the resulting hybrid star vary dramatically when the maximum magnetic field strength goes beyond a threshold of $\sim 5 \times 10^{17}$ G but they are insensitive to the magnetic field below this threshold. Specifically, the magnetic deformation makes the rest-mass density drop significantly, suppressing the matter fraction in the mixed phase. Therefore, this work provides a solid support for the magnetic effects on a hybrid star, so it is possible to link observational signals from the star to its magnetic field configuration.

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A. Yip, P. Cheong and T. Li
Thu, 30 Mar 23
61/66

Comments: 8 pages, 3 figures

The Greisen Function and its Ability to Describe Air-Shower Profiles [HEAP]

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http://arxiv.org/abs/2303.16670


Ultrahigh-energy cosmic rays are almost exclusively detected through extensive air showers, which they initiate upon interaction with the atmosphere. The longitudinal development of these air showers can be directly observed using fluorescence detector telescopes, such as those employed at the Pierre Auger Observatory or the Telescope Array. In this article, we discuss the properties of the Greisen function, which was initially derived as an approximate solution to the electromagnetic cascade equations, and its ability to describe the longitudinal shower profiles. We demonstrate that the Greisen function can be used to describe longitudinal air-shower profiles, even for hadronic air showers. Furthermore we discuss the possibility to discriminate between hadrons and photons from the shape of air-shower profiles using the Greisen function.

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M. Stadelmaier, J. Vícha and V. Novotný
Thu, 30 Mar 23
62/66

Comments: N/A

Spontaneous Scalarization in Proto-neutron Stars [HEAP]

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http://arxiv.org/abs/2303.16630


Proto-neutron stars are born when a highly evolved and massive star collapses under gravity. In this paper, we investigate the spontaneous scalarization in proto-neutron stars. Based on the scalar tensor theory of gravity as well as the physical conditions in proto-neutron star, we examine the structure of proto-neutron star. To describe the fluid in proto-neutron star, we utilize $SU(2)$ chiral sigma model and the finite temperature extension of the Brueckner-Bethe-Goldstone quantum many-body theory in the Brueckner-Hartree-Fock approximation. Here, we apply the equation of state of proto-neutron stars considering different cases i.e. hot pure neutron matter and hot $\beta$-stable neutron star matter without neutrino trapping as well as with neutrino trapping. The effects of temperature and entropy of proto-neutron stars on the star structure are also studied. Our results confirm that the spontaneous scalarization is affected by different physical conditions in proto-neutron stars.

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F. Rahimi and Z. Rezaei
Thu, 30 Mar 23
63/66

Comments: 16 pages, 9 figures. Accepted for publication in European Physical Journal C

Fast radio burst energy function in the presence of $\rm DM_{host}$ variation [HEAP]

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http://arxiv.org/abs/2303.16775


Fast radio bursts (FRBs) have been found in great numbers but the physical mechanism of these sources is still a mystery. The redshift evolutions of the FRB energy distribution function and the volumetric rate shed light on revealing the origin of the FRBs. However, such estimations rely on the dispersion measurement (DM)-redshift ($z$) relationship. A few of FRBs detected recently show large excess DM beyond the expectation from the cosmological and Milky Way contributions, which indicates large spread of DM from their host galaxies. In this work, we adopt the lognormal distributed $\rm DM_{host}$ model and estimate the energy function using the non-repeating FRBs selected from the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB Catalog 1. By comparing the lognormal distributed $\rm DM_{host}$ model to the constant $\rm DM_{host}$ model, the FRB energy function results are consistent within the measurement uncertainty. We also estimate the volumetric rate of the non-repeating FRBs in three different redshift bins. The volumetric rate shows that the trend is consistent with the stellar-mass density redshift evolution. Since the lognormal distributed $\rm DM_{host}$ model increases the measurement errors, the inference of FRBs tracking the stellar-mass density is nonetheless undermined.

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Y. Li, J. Zou, J. Zhang, et. al.
Thu, 30 Mar 23
65/66

Comments: 8 pages, 5 figures

A Study of Modified Characteristics of Hadronic Interactions [HEAP]

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http://arxiv.org/abs/2303.15911


We have implemented ad-hoc modifications to the CORSIKA Monte-Carlo generator which allow us to simultaneously adjust the multiplicity, elasticity and cross-section of hadronic interactions with respect to the predictions of the Sibyll 2.3d interaction model, in order to assess whether a reasonable combination of changes (that is not excluded by current experimental data) could alleviate the observed tension between the model predictions and observed features of extensive air showers induced by ultra-high energy cosmic rays (UHECR). Previously, we have studied the effects of such changes on proton-initiated showers. Because a multitude of experimental data suggest that the primary composition of the UHECR is mixed, we have expanded the modification procedure to include nuclear projectiles in a consistent way based on the superposition model, in a similar manner as was used in the previous studies carried out using one-dimensional simulation methods. As we are using a fully three-dimensional approach, we can quantify the effects of the changes on both longitudinal and lateral features of the showers. With the inclusion of nuclear projectiles, we can study the impact of the changes on observable quantities for realistic primary beams as well as on the determination of the primary composition from data under the assumption of the modified hadronic interactions.

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J. Blazek, J. Ebr, J. Vicha, et. al.
Wed, 29 Mar 23
3/73

Comments: 6 pages, 9 figures, a conference proceeding for UHECR2022

A Search for IceCube sub-TeV Neutrinos Correlated with Gravitational-Wave Events Detected By LIGO/Virgo [HEAP]

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http://arxiv.org/abs/2303.15970


The LIGO/Virgo collaboration published the catalogs GWTC-1, GWTC-2.1 and GWTC-3 containing candidate gravitational-wave (GW) events detected during its runs O1, O2 and O3. These GW events can be possible sites of neutrino emission. In this paper, we present a search for neutrino counterparts of 90 GW candidates using IceCube DeepCore, the low-energy infill array of the IceCube Neutrino Observatory. The search is conducted using an unbinned maximum likelihood method, within a time window of 1000 s and uses the spatial and timing information from the GW events. The neutrinos used for the search have energies ranging from a few GeV to several tens of TeV. We do not find any significant emission of neutrinos, and place upper limits on the flux and the isotropic-equivalent energy emitted in low-energy neutrinos. We also conduct a binomial test to search for source populations potentially contributing to neutrino emission. We report a non-detection of a significant neutrino-source population with this test.

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R. Abbasi, M. Ackermann, J. Adams, et. al.
Wed, 29 Mar 23
11/73

Comments: Submitted to ApJ

The peculiar variable X-ray spectrum of the active galactic nucleus PKS 2005-489 [HEAP]

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http://arxiv.org/abs/2303.15589


PKS 2005-489 is a well-known, bright southern BL Lac object that has been detected up to TeV energies. In a low-flux state it exhibits the expected multiwavelength double-peaked spectrum in the radio — $\gamma$-ray band. The high-flux state shows extreme flux variations in the X-ray band with a hardening as well as a peculiar curved feature in the spectrum. Thus far, PKS 2005-489 is the only source to exhibit such a feature. To study the X-ray variability further, we obtained the first hard X-ray spectrum of the source with NuSTAR. We compare quasi-simultaneous radio, optical, UV, soft and hard X-ray, and $\gamma$-ray data of PKS 2005-489 to archival data in order to study its broadband behavior. We find a very consistent quiet state in the SED, with little variation in spectral shape or flux between the 2012 and 2020 data. A possible explanation for the peculiar X-ray spectrum in the flaring state is an additional component in the jet, possibly accelerated via magnetic reconnection, that is not co-spatial to the low-flux state emission region.

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O. Chase, F. McBride, A. Gokus, et. al.
Wed, 29 Mar 23
13/73

Comments: N/A

The Positron Puzzle [HEAP]

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http://arxiv.org/abs/2303.15582


The Positron Puzzle is a half-century old conundrum about the origin of the Galactic $\gamma$-ray emission line at photon energies of 511 keV, and the shape of its morphology, showing a bulge-to-disk luminosity ratio of $\sim 1$ – unlike any astrophysical source distribution. Positrons that have been cooled to the eV scale capture electrons and form the intermediate bound state of Positronium (Ps) which decays on a nano-second timescale into two or three photons. Assuming the emission to originate from the Galactic bulge, centre, and disk, a visible annihilation rate in the Milky Way of $\sim 5 \times 10^{43}\,\mathrm{e^+\,s^{-1}}$ has to be explained, either by a quasi-steady state of production and annihilation, or by possibly multiple burst-like events that flood the Galaxy with positrons, then fading away on a Myr timescale. In this paper, I will review what the real Positron Puzzle is, where data and simulations have been used inadequately which resulted in false claims and an apparent quandary, what we really know and absolutely not know about the topic, and how this epistemic problem might be advancing.

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T. Siegert
Wed, 29 Mar 23
14/73

Comments: Invited contribution, 27 pages, 8 figures, 2 tables, accepted in Astrophysics and Space Sciences

Wind-Fed GRMHD Simulations of Sagittarius A*: Tilt and Alignment of Jets and Accretion Discs, Electron Thermodynamics, and Multi-Scale Modeling of the Rotation Measure [HEAP]

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http://arxiv.org/abs/2303.15503


Wind-fed models offer a unique way to form predictive models of the accretion flow surrounding Sagittarius A*. We present 3D, wind-fed MHD and GRMHD simulations spanning the entire dynamic range of accretion from parsec scales to the event horizon. We expand on previous work by including nonzero black hole spin and dynamically evolved electron thermodynamics. Initial conditions for these simulations are generated from simulations of the observed Wolf-Rayet stellar winds in the Galactic Centre. The resulting flow tends to be highly magnetized ($\beta \approx 2$) with an $\sim$ $r^{-1}$ density profile independent of the strength of magnetic fields in the winds. Our simulations reach the MAD state for some, but not all cases. In tilted flows, SANE jets tend to align with the angular momentum of the gas at large scales, even if that direction is perpendicular to the black hole spin axis. Conversely, MAD jets tend to align with the black hole spin axis. The gas angular momentum shows similar behavior: SANE flows tend to only partially align while MAD flows tend to fully align. With a limited number of dynamical free parameters, our models can produce accretion rates, 230 GHz flux, and unresolved linear polarization fractions roughly consistent with observations for several choices of electron heating fraction. Absent another source of large-scale magnetic field, winds with a higher degree of magnetization (e.g., where the magnetic pressure is 1/100 of the ram pressure in the winds) may be required to get a sufficiently large RM with consistent sign.

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S. Ressler, C. White and E. Quataert
Wed, 29 Mar 23
17/73

Comments: Accepted by MNRAS. Animations for several figures in the paper are available at this https URL

The Decoupling of Binaries from Their Circumbinary Disks [HEAP]

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http://arxiv.org/abs/2303.16204


We have investigated, both analytically and numerically, accreting supermassive black hole binaries as they inspiral due to gravitational radiation to elucidate the decoupling of binaries from their disks and inform future multi-messenger observations of these systems. Our numerical studies evolve equal-mass binaries from initial separations of $100 GM/c^2$ until merger, resolving scales as small as $\sim0.04 GM/c^2$, where $M$ is the total binary mass. Our simulations accurately capture the point at which the orbital evolution of each binary decouples from that of their circumbinary disk, and precisely resolve the flow of gas throughout the inspiral. We demonstrate analytically and numerically that timescale-based predictions overestimate the binary separations at which decoupling occurs by factors of $\sim3$, and illustrate the utility of a velocity-based decoupling criterion. High-viscosity ($\nu\gtrsim0.03 GM/c$) circumbinary systems decouple late ($a_b\lesssim 15 GM/c^2$) and have qualitatively similar morphologies near merger to circumbinary systems with constant binary separations. Lower-viscosity circumbinary disks decouple earlier and exhibit qualitatively different accretion flows, which lead to precipitously decreasing accretion onto the binary. If detected, such a decrease may unambiguously identify the host galaxy of an ongoing event within a LISA error volume. We illustrate how accretion amplitude and variability evolve as binaries gradually decouple from their circumbinary disks, and where decoupling occurs over the course of binary inspirals in the LISA band. We show that, even when dynamically negligible, gas may leave a detectable imprint on the phase of gravitational waves.

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A. Dittmann, G. Ryan and M. Miller
Wed, 29 Mar 23
20/73

Comments: 10 pages, 5 figures. Submitted to ApJL, comments welcome

The largest bright ULX population in a galaxy: X-ray variability and Luminosity Function in the Cartwheel ring Galaxy [HEAP]

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http://arxiv.org/abs/2303.15502


We analyse all the available Chandra observations of the Cartwheel Galaxy and its compact group, taken between 2001 and 2008, with the main aim of addressing the variability in the X-ray band for this spectacular collisional ring galaxy. We focus on the study of point-like sources, in particular we are interested in Ultraluminous X-ray sources (ULXs, Lx >= 10^39 erg/s), that we treat as a class. We exploit archival XMM-Newton data to enrich the study of the long-term variability, on timescales of months to years. We find a total of 44 sources in the group area, of which 37 in total are ULXs positionally linked with the galaxies and of which we can study variability. They are 29 in the Cartwheel itself, 7 in G1 and 1 in G3. About one third of these 37 sources show long-term variability, while no variability is detected within the single observations. Of those, 5 ULXs have a transient behaviour with a maximum range of variability (Lmax/Lmin) of about one order of magnitude and are the best candidate neutron stars. The X-ray Luminosity Function (XLF) of the point-like sources remains consistent in shape between the Chandra observations both for the Cartwheel galaxy itself and for G1, suggesting that flux variability does not strongly influence the average properties of the population on the observation timescales.

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C. Salvaggio, A. Wolter, A. Belfiore, et. al.
Wed, 29 Mar 23
34/73

Comments: 17 pages, 5 figures, Accepted for publication in MNRAS

XRBcats: Galactic Low Mass X-ray Binary Catalogue [HEAP]

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http://arxiv.org/abs/2303.16168


We present a new catalogue of low-mass X-ray binaries (LMXBs) in the Galaxy. The catalogue contains source names, coordinates, source types, fluxes, distances, system parameters, and other characteristic properties of 348 LMXBs, including LMXBs that were newly discovered or re-classified since the latest releases of the catalogues by Liu et al. (2007) and Ritter and Kolb (2003). The aim of this catalogue is to provide a list of all currently known Galactic objects identified as LMXBs with some basic information on each system (including X-ray and optical/IR properties where possible). Literature published before March 2023 has, as far as possible, been taken into account when compiling this information. References for all reported properties as well as object finding charts in several energy bands are provided as part of the catalogue. We plan to update the catalogue regularly, in particular to reflect new objects discovered in the ongoing large scale surveys such as Gaia and eROSITA.

Read this paper on arXiv…

A. Avakyan, M. Neumann, A. Zainab, et. al.
Wed, 29 Mar 23
35/73

Comments: 13 pages, 2 figures, submitted to A&A. For auxillary files, see this http URL

Gamma rays from Nebulae around Recurrent Novae [HEAP]

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http://arxiv.org/abs/2303.15741


Novae were discovered to emit transient gamma rays during the period of several days to a few weeks after initial explosion, indicating presence of acceleration processes of particles in their expanding shells. In the case of recurrent novae, electrons can be in principle accelerated in the nova shells for the whole recurrence period of nova producing delayed $\gamma$ ray emission as considered in Bednarek (2022). Here we extend the ideas presented in this article by considering the fate of electrons which diffuse out of the shells of novae supplying fresh relativistic electrons to the recurrent nova super-remnants during the whole active period of nova ($\ge 10^4$ yrs). We develop a model for the acceleration of electrons and their escape from the nova shells. The electrons within the recurrent nova super-remnants produce $\gamma$ rays in the comptonization process of the radiation from the red giant companion and the Cosmic Microwave Background Radiation. As an example, the case of a symbiotic nova RS Oph (with the recurrence period estimated on $\sim$10-50 yrs) is considered in more detail. Predicted $\gamma$-ray emission from the nova super-remnant around RS Oph is discussed in the context of its observability by satellite experiments (i.e. Fermi-LAT) as well as current and future Cherenkov telescopes.

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W. Bednarek and J. Sitarek
Wed, 29 Mar 23
37/73

Comments: 17 pages, 9 figures, Journal of High Energy Astrophysics, accepted

Refining the 2022 OJ 287 impact flare arrival epoch [HEAP]

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http://arxiv.org/abs/2303.15886


The bright blazar OJ~287 routinely parades high brightness bremsstrahlung flares, which are explained as being a result of a secondary supermassive black hole (SMBH) impacting the accretion disc of a more massive primary SMBH in a binary system. The accretion disc is not rigid but rather bends in a calculable way due to the tidal influence of the secondary. Below we refer to this phenomenon as a variable disc level. We begin by showing that these flares occur at times predicted by a simple analytical formula, based on general relativity inspired modified Kepler equation, which explains impact flares since 1888.
The 2022 impact flare, namely flare number 26, is rather peculiar as it breaks the typical pattern of two impact flares per 12-year cycle. This is the third bremsstrahlung flare of the current cycle that follows the already observed 2015 and 2019 impact flares from OJ~287.
It turns out that the arrival epoch of flare number 26 is sensitive to the level of primary SMBH’s accretion disc relative to its mean level in our model. We incorporate these tidally induced changes in the level of the accretion disc to infer that the thermal flare should have occurred during July-August 2022, when it was not possible to observe it from the Earth. Thereafter, we explore possible observational evidence for certain pre-flare activity by employing spectral and polarimetric data from our campaigns in 2004/05 and 2021/22. We point out theoretical and observational implications of two observed mini-flares during January-February 2022.

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M. Valtonen, S. Zola, G. Gopakumar, et. al.
Wed, 29 Mar 23
39/73

Comments: 29 pages, 6 figures, 1 table. arXiv admin note: text overlap with arXiv:2209.08360

Magnetised tori with magnetic polarisation around Kerr black holes: variable angular momentum discs [HEAP]

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http://arxiv.org/abs/2303.15867


Analytical models of magnetised, geometrically thick discs are relevant to understand the physical conditions of plasma around compact objects and to explore its emitting properties. This has become increasingly important in recent years in the light of the Event Horizon Telescope observations of Sgr A* and M87. Models of thick discs around black holes usually consider constant angular momentum distributions and do not take into account the magnetic response of the fluid to applied magnetic fields. We present a generalisation of our previous work on stationary models of magnetised accretion discs with magnetic polarisation (Pimentel et al. 2018). This extension is achieved by accounting for non-constant specific angular momentum profiles, done through a two-parameter ansatz for those distributions. We build a large number of new equilibrium solutions of thick discs with magnetic polarisation around Kerr black holes, selecting suitable parameter values within the intrinsically substantial parameter space of the models. We study the morphology and the physical properties of those solutions, finding qualitative changes with respect to the constant angular momentum tori of (Pimentel et al. 2018). However, the dependences found on the angular momentum distribution or on the black hole spin do not seem to be strong. Some of the new solutions, however, exhibit a local maximum of the magnetisation function, absent in standard magnetised tori. Due to the enhanced development of the magneto-rotational instability as a result of magnetic susceptibility, those models might be particularly well-suited to investigate jet formation through general-relativistic MHD simulations. The new equilibrium solutions reported here can be used as initial data in numerical codes to assess the impact of magnetic susceptibility in the dynamics and observational properties of thick disc-black hole systems.

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S. Pimentel, F. Lora-Clavijo, A. Cruz-Osorio, et. al.
Wed, 29 Mar 23
49/73

Comments: 15 pages, 8 figures. Comments welcome

QPE or QPO? — Quasiperiodic Activity in Low-Mass Galaxy Nuclei [HEAP]

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http://arxiv.org/abs/2303.16185


Quasiperiodic eruptions (QPEs) from low-mass galaxy centres may result from accretion from a white dwarf in a very eccentric orbit about the central massive black hole. Evolution under gravitational radiation losses reduces the separation and eccentricity. I note that below a critical eccentricity $e_{\rm crit} \simeq 0.97$, the accretion disc’s viscous timescale at pericentre passage is probably longer than the orbital period $P$, and periodic eruptive behaviour is no longer possible. These QPE descendant systems (QPEDs) are then likely to produce quasiperiodic oscillations (QPOs) rather than eruptions, varying more smoothly over the orbital cycle, with duty cycles $\sim1$. I identify 2XMM J123103.2+110648 ($P \simeq 3.9$~hr) and (more tentatively) RE J1034+396 ($P \simeq 1$~hr) as candidate systems of this type, and find agreement with their deduced eccentricities $e < e_{\rm crit}$. The absence of eruptions and the lower accretion luminosities resulting from the smaller gravitational radiation losses may make QPED systems harder to discover. Ultimately they must evolve to have viscous times much longer than the orbital period, and either remain steady, or possibly have infrequent but large outbursts. The latter systems would be massive analogues of the soft X-ray transients produced by low stellar-mass X-ray binaries.

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A. King
Wed, 29 Mar 23
51/73

Comments: accepted for publication in MNRAS

Prospects for detection rate of very-high-energy γ-ray emissions from short γ-ray bursts with the HADAR experiment [HEAP]

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http://arxiv.org/abs/2303.15683


The observation of short gamma ray bursts (SGRBs) in the TeV energy range plays an important role in understanding the radiation mechanism and probing new areas of physics such as Lorentz invariance violation. However, no SGRB has been observed in this energy range due to the short duration of SGRBs and the weakness of current experiments. New experiments with new technology are required to detect sub-TeV SGRBs. In this work, we observe the very high energy (VHE) $\gamma$-ray emissions from SGRBs and calculate the annual detection rate with the High Altitude Detection of Astronomical Radiation HADAR (HADAR) experiment. First, a set of pseudo-SGRB samples is generated and checked using the observations of Fermi-GBM, Fermi-LAT, and SWIFT measurements. The annual detection rate is calculated from these SGRB samples based on the performance of the HADAR instrument. As a result, the HADAR experiment can detect 0.5 SGRB per year if the spectral break-off of $\gamma$-rays caused by the internal absorption is larger than 100 GeV. For a GRB09010-like GRB in HADAR’s view, it should be possible to detect approximately 2000 photons considering the internal absorption. With a time delay assumption due to the Lorentz invariance violation effects, a simulated light curve of GRB090510 has evident energy dependence. We hope that the HADAR experiment can perform the SGRB observations and test our calculations in the future.

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Q. Chen, P. Hu, J. Su, et. al.
Wed, 29 Mar 23
54/73

Comments: N/A

Ultrafast Variability in AGN Jets: Intermittency and Lighthouse Effect [HEAP]

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http://arxiv.org/abs/2303.15854


Gamma-ray flares from Active Galactic Nuclei (AGN) show substantial variability on ultrafast timescales (i.e. shorter than the light crossing time of the AGN’s supermassive black hole). We propose that ultrafast variability is a byproduct of the turbulent dissipation of the jet Poynting flux. Due to the intermittency of the turbulent cascade, the dissipation is concentrated in a set of reconnecting current sheets. Electrons energised by reconnection have a strong pitch angle anisotropy, i.e. their velocity is nearly aligned with the guide magnetic field. Then each current sheet produces a narrow radiation beam, which dominates the emission from the whole jet when it is directed towards the observer. The ultrafast variability is set by the light crossing time of a single current sheet, which is much shorter than the light crossing time of the whole emission region. The predictions of our model are: (i) The bolometric luminosity of ultrafast AGN flares is dominated by the inverse Compton (IC) emission, as the lower energy synchrotron emission is suppressed due to the pitch angle anisotropy. (ii) If the observed luminosity includes a non-flaring component, the variations of the synchrotron luminosity have a small amplitude. (iii) The synchrotron and IC emission are less variable at lower frequencies, as the cooling time of the radiating particles exceeds the light crossing time of the current sheet. Simultaneous multiwavelength observations of ultrafast AGN flares can test these predictions.

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E. Sobacchi, T. Piran and L. Comisso
Wed, 29 Mar 23
58/73

Comments: 9 pages, accepted for publication in ApJL

Searching for long faint astronomical high energy transients: a data driven approach [HEAP]

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http://arxiv.org/abs/2303.15936


HERMES (High Energy Rapid Modular Ensemble of Satellites) pathfinder is an in-orbit demonstration consisting of a constellation of six 3U nano-satellites hosting simple but innovative detectors for the monitoring of cosmic high-energy transients. The main objective of HERMES Pathfinder is to prove that accurate position of high-energy cosmic transients can be obtained using miniaturized hardware. The transient position is obtained by studying the delay time of arrival of the signal to different detectors hosted by nano-satellites on low Earth orbits. To this purpose, the goal is to achive an overall accuracy of a fraction of a micro-second. In this context, we need to develop novel tools to fully exploit the future scientific data output of HERMES Pathfinder. In this paper, we introduce a new framework to assess the background count rate of a space-born, high energy detector; a key step towards the identification of faint astrophysical transients. We employ a Neural Network (NN) to estimate the background lightcurves on different timescales. Subsequently, we employ a fast change-point and anomaly detection technique to isolate observation segments where statistically significant excesses in the observed count rate relative to the background estimate exist. We test the new software on archival data from the NASA Fermi Gamma-ray Burst Monitor (GBM), which has a collecting area and background level of the same order of magnitude to those of HERMES Pathfinder. The NN performances are discussed and analyzed over period of both high and low solar activity. We were able to confirm events in the Fermi/GBM catalog and found events, not present in Fermi/GBM database, that could be attributed to Solar Flares, Terrestrial Gamma-ray Flashes, Gamma-Ray Bursts, Galactic X-ray flash. Seven of these are selected and analyzed further, providing an estimate of localisation and a tentative classification.

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R. Crupi, G. Dilillo, E. Bissaldi, et. al.
Wed, 29 Mar 23
59/73

Comments: N/A

Universality of Cherenkov Light in EAS [HEAP]

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http://arxiv.org/abs/2303.15653


The reconstruction of cosmic-ray-induced extensive air showers with a non-imaging Cherenkov detector array requires knowledge of the Cherenkov yield of any given air shower for a given set of shower parameters. Although air showers develop in a stochastic cascade, certain characteristics of the particles in the shower have been shown to come from universal probability distributions, a property known as shower universality. Both the energy and the angular distributions of charged particles within a shower have been parameterized. One can use these distributions to calculate the Cherenkov photon yield as an angular distribution from the Cherenkov cones of charged particles at various stages of shower development. This Cherenkov photon yield can then be tabulated for use in the reconstruction of air showers. In this work, we develop the calculation of both the Cherenkov angular distribution and Cherenkov yield per shower particle, and show how a look-up table was constructed to capture the relevant features of these distributions for general use. We compare the results of our calculations with the results of full, particle-stack, Monte Carlo simulation of the Cherenkov light produced in extensive air showers using CORSIKA-IACT. We make comparisons of both the lateral distribution of the Cherenkov photon flux amongst several detectors and of the arrival-time distribution of the Cherenkov photons in a single detector.

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I. Buckland and D. Bergman
Wed, 29 Mar 23
60/73

Comments: N/A

Time-dependent visibility modelling of a relativistic jet in the X-ray binary MAXI J1803-298 [HEAP]

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http://arxiv.org/abs/2303.15648


Tracking the motions of transient jets launched by low-mass X-ray binaries (LMXBs) is critical for determining the moment of jet ejection, and identifying any corresponding signatures in the accretion flow. However, these jets are often highly variable and can travel across the resolution element of an image within a single observation, violating a fundamental assumption of aperture synthesis. We present a novel approach in which we directly fit a single time-dependent model to the full set of interferometer visibilities, where we explicitly parameterise the motion and flux density variability of the emission components, to minimise the number of free parameters in the fit, while leveraging information from the full observation. This technique allows us to detect and characterize faint, fast-moving sources, for which the standard time binning technique is inadequate. We validate our technique with synthetic observations, before applying it to three Very Long Baseline Array (VLBA) observations of the black hole candidate LMXB MAXI J1803-298 during its 2021 outburst. We measured the proper motion of a discrete jet component to be $1.37\pm0.14$ mas/hr, and thus we infer an ejection date of MJD $59348.08_{-0.06}^{+0.05}$, which occurs just after the peak of a radio flare observed by the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/Sub-Millimeter Array (ALMA), while MAXI J1803-298 was in the intermediate state. Further development of these new VLBI analysis techniques will lead to more precise measurements of jet ejection dates, which, combined with dense, simultaneous multi-wavelength monitoring, will allow for clearer identification of jet ejection signatures in the accretion flow.

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C. Wood, J. Miller-Jones, A. Bahramian, et. al.
Wed, 29 Mar 23
66/73

Comments: 15 pages, 9 figures, 4 tables; Accepted for publication in MNRAS

$κ$monty: a Monte Carlo Compton Scattering code including non-thermal electrons [HEAP]

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http://arxiv.org/abs/2303.15522


Low-luminosity active galactic nuclei are strong sources of X-ray emission produced by Compton scattering originating from the accretion flows surrounding their supermassive black holes. The shape and energy of the resulting spectrum depend on the shape of the underlying electron distribution function (DF). In this work, we present an extended version of the grmonty code, called $\kappa$monty. The grmonty code previously only included a thermal Maxwell J\”utner electron distribution function. We extend the gromty code with non-thermal electron DFs, namely the $\kappa$ and power-law DFs, implement Cartesian Kerr-Schild coordinates, accelerate the code with MPI, and couple the code to the non-uniform AMR grid data from the GRMHD code BHAC. For the Compton scattering process, we derive two sampling kernels for both distribution functions. Finally, we present a series of code tests to verify the accuracy of our schemes. The implementation of non-thermal DFs opens the possibility of studying the effect of non-thermal emission on previously developed black hole accretion models.

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J. Davelaar, B. Ryan, G. Wong, et. al.
Wed, 29 Mar 23
69/73

Comments: 12 pages, 9 figures, submitted to journal

XRBcats: Galactic High Mass X-ray Binary Catalogue [HEAP]

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http://arxiv.org/abs/2303.16137


We present a new catalogue of the high-mass X-ray binaries (HMXBs) in the Galaxy improving upon the most recent such catalogue. We include new HMXBs discovered since aforementioned publication and revise the classification for several objects previously considered HMXBs or candidates. The catalogue includes both basic information such as source names, coordinates, types, and more detailed data such as distance and X-ray luminosity estimates, binary system parameters and other characteristic properties of 169 HMXBs, together with appropriate references to the literature. Finding charts in several bands from infra-red to hard X-rays are also included for each object. The aim of this catalogue is to provide the reader a list of all currently known Galactic HMXBs with some basic information on both compact objects and non-degenerate counterpart properties (where available). We also include objects tentatively classified as HXMBs in the literature and give a brief motivation for the classifcation in each relevant case. The catalogue is compiled based on a search of known HMXBs and candidates in all commonly available databases and literature published before 31 October 2022. Relevant properties in the optical and other bands were collected for all objects either from the literature or using the data provided by large-scale surveys. In the later case, the counterparts in each individual survey were found by cross-correlating positions of identified HMXBs with relevant databases. An up-to date catalogue of Galactic HMXBs is presented to facilitate research in this area. An attempt was made to collect a larger set of relevant HMXB properties in a more uniform way compared to previously published works.

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M. Neumann, A. Avakyan, V. Doroshenko, et. al.
Wed, 29 Mar 23
71/73

Comments: 10 pages, 2 figures, submitted to A&A. For auxillary files, see this http URL

Testing Model Predictions of Depth of Air-Shower Maximum and Signals in Surface Detectors using Hybrid Data of the Pierre Auger Observatory [HEAP]

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http://arxiv.org/abs/2303.14788


We present a method for testing the predictions of hadronic interaction models and improving their consistency with observed two-dimensional distributions of the depth of shower maximum, $X_\text{max}$, and signal at the ground level as a function of zenith angle. The method relies on the assumption that the mass composition is the same at all zenith angles, while the atmospheric shower development and attenuation depend on composition in a correlated way. In the present work, for each of the three leading LHC-tuned hadronic interaction models, we allow a global shift $\Delta X_\text{max}$ of the predicted shower maximum, which is the same for every mass and energy, and a rescaling $R_\text{Had}$ of the hadronic component at the ground level which is constant with the zenith angle.
We apply the analysis to 2297 events reconstructed with both the fluorescence and surface detectors of the Pierre Auger Observatory with energies $10^{18.5-19.0}$ eV and zenith angles below 60$^\circ$. Given the modeling assumptions made in this analysis, the best fit reaches its optimum value when shifting the $X_\text{max}$ predictions of hadronic interaction models to deeper values and increasing the hadronic signal. This change in the predicted $X_\text{max}$ scale alleviates the previously identified model deficit in the hadronic signal (commonly called the muon puzzle) but does not fully remove it. Because of the size of the adjustments $\Delta X_\text{max}$ and $R_\text{Had}$ and the large number of events in the sample, the statistical significance of need for these adjustments is large, greater than 5$\sigma_\text{stat}$, even for the combination of the systematic experimental shifts within 1$\sigma_\text{sys}$ that are the most favorable for the models.

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Jakub Vícha
Tue, 28 Mar 23
5/81

Comments: Proceedings of the 6th International Symposium on Ultra High Energy Cosmic Rays (UHECR 2022), Oct 3-7, 2022, Gran Sasso Science Institute, L’Aquila, Italy. Accepted for publications in EPJ Web of Conferences series

Sensitivity of the Cherenkov Telescope Array to spectral signatures of hadronic PeVatrons with application to Galactic Supernova Remnants [HEAP]

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http://arxiv.org/abs/2303.15007


The local Cosmic Ray (CR) energy spectrum exhibits a spectral softening at energies around 3~PeV. Sources which are capable of accelerating hadrons to such energies are called hadronic PeVatrons. However, hadronic PeVatrons have not yet been firmly identified within the Galaxy. Several source classes, including Galactic Supernova Remnants (SNRs), have been proposed as PeVatron candidates. The potential to search for hadronic PeVatrons with the Cherenkov Telescope Array (CTA) is assessed. The focus is on the usage of very high energy $\gamma$-ray spectral signatures for the identification of PeVatrons. Assuming that SNRs can accelerate CRs up to knee energies, the number of Galactic SNRs which can be identified as PeVatrons with CTA is estimated within a model for the evolution of SNRs. Additionally, the potential of a follow-up observation strategy under moonlight conditions for PeVatron searches is investigated. Statistical methods for the identification of PeVatrons are introduced, and realistic Monte–Carlo simulations of the response of the CTA observatory to the emission spectra from hadronic PeVatrons are performed. Based on simulations of a simplified model for the evolution for SNRs, the detection of a $\gamma$-ray signal from in average 9 Galactic PeVatron SNRs is expected to result from the scan of the Galactic plane with CTA after 10 hours of exposure. CTA is also shown to have excellent potential to confirm these sources as PeVatrons in deep observations with $\mathcal{O}(100)$ hours of exposure per source.

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C. Consortium, F. Acero, A. Acharyya, et. al.
Tue, 28 Mar 23
6/81

Comments: 34 pages, 16 figures, Accepted for publication in Astroparticle Physics

Revisiting the Chandra Observation on the Region of PSR J1809-1917: Indication of an X-ray Halo and Implication for the Origin of HESS J1809-193 [HEAP]

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http://arxiv.org/abs/2303.14946


HESS J1809-193 is an extended TeV $\gamma$-ray source and the origin of its $\gamma$-ray emission remains ambiguous. Pulsar wind nebula (PWN) of PSR J1809-1917 laying inside the extended $\gamma$-ray emission is a possible candidate. Powered by the central pulsar, ultrarelativistic electrons in PWN can produce radio to X-ray emission through synchrotron and $\gamma$-ray emission by inverse Compton (IC) scattering. To check whether this PWN is the counterpart of HESS J1809-193, we analyzed Chandra X-ray radial intensity profile and the spectral index profile of this PWN. We then adopt a one-zone isotropic diffusion model to fit the keV and the TeV data. We find diffuse nonthermal X-ray emission extending beyond PWN, which is likely an X-ray halo radiated by escaping electron/positron pairs from the PWN. A relatively strong magnetic field of $21\,\mu$G is required to explain the spatial evolution of the X-ray spectrum (i.e., the significant softening of the spectrum with increasing distance from the pulsar), which, however, would suppress the IC radiation of pairs. Our result implies that a hadronic component may be needed to explain HESS J1809-193.

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C. Li, C. Ge and R. Liu
Tue, 28 Mar 23
16/81

Comments: 20 pages, 8 figures, comments are welcome!

The origin diversity of non-repeating fast radio bursts: Rotational radio transient sources and cosmological compact binary merger remnants? [HEAP]

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http://arxiv.org/abs/2303.14695


A large number of fast radio bursts (FRBs) detected with the CHIME telescope enable us to investigate their energy distributions in different redshift intervals, incorporating with the consideration of the selection effects of CHIME. As a result, we obtain a non-evolving energy function (EF), which is in a power law form with a low-energy exponential cutoff, for the high-energy FRBs (HEFRBs) of energies $E\gtrsim2\times0^{38}$ erg. On the contrary, the energy distribution of the low-energy FRBs (LEFRBs) obviously cannot be described by the same EF. Including the lowest dispersion measures (DMs) samples, the LEFRBs are concentrated towards the Galactic plane and their latitude distribution is similar to that of Galactic rotational radio transients (RRATs). These indications hint that LEFRBs might compose a special type of RRATs with relatively higher DMs and energies (i.e., $\sim10^{28-31}$ erg for a reference distance of $\sim10$ kpc if they belong to the Milky Way). Finally, we revisit the redshift-dependent event rate of HEFRBs and confirm that they could be produced by the remnants of cosmological compact binary mergers.

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Z. Zhang, Y. Yu and X. Cao
Tue, 28 Mar 23
26/81

Comments: 8 pages, 7 figures, submitted to A&A

Jitter Mechanism as a Kind of Coherent Radiation: Constrained by the GRB 221009A Emission at 18 TeV [HEAP]

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http://arxiv.org/abs/2303.14398


The emission of gamma-ray burst (GRB) 221009A at 18 TeV has been detected by the large high-altitude air shower observatory (LHAASO). We suggest jitter radiation as a possible explanation for the TeV emission for this energetic GRB. In our scenario, the radiation field is linked to the perturbation field, and the perturbation field is dominated by kinetic turbulence. Kinetic turbulence takes a vital role in both magnetic field generation and particle acceleration. The jitter radiation can reach the TeV energy band when we consider either electron cooling or Landau damping. We further suggest that the jitter radiation in the very high-energy band is coherent emission. Our modeling results can be constrained by the observational results of GRB 221009A in the TeV energy band. This radiation mechanism is expected to have wide applications in the high-energy astrophysical research field.

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J. Mao and J. Wang
Tue, 28 Mar 23
33/81

Comments: ApJ accepted

Radio Pulsar Emission-Beam Geometry at Low Frequency: LOFAR High Band Survey Sources Studied using Arecibo at 1.4 GHz and 327 MHz [HEAP]

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http://arxiv.org/abs/2303.15209


This paper continues our study of radio pulsar emission-beam configurations with the primary intent of extending study to the lowest possible frequencies. Here we focus on a group of 133 more recently discovered pulsars, most of which were included in the (100-200 MHz) LOFAR High Band Survey, observed with Arecibo at 1.4 GHz and 327 MHz, and some observed at decameter wavelengths. Our analysis framework is the core/double-cone beam model, and we took opportunity to apply it as widely as possible, both conceptually and quantitatively, while highlighting situations where modeling is difficult, or where its premises may be violated. In the great majority of pulsars, beam forms consistent with the core/double-cone model were identified. Moreover, we found that each pulsar’s beam structure remained largely constant over the frequency range available; where profile variations were observed, they were attributable to different component spectra and in some instances to varying conal beam sizes. As an Arecibo population, many or most of the objects tend to fall in the Galactic anticenter region and/or at high Galactic latitudes, so overall it includes a number of nearer, older pulsars. We found a number of interesting or unusual characteristics in some of the pulsars that would benefit from additional study. The scattering levels encountered for this group are low to moderate, apart from a few pulsars lying in directions more toward the inner Galaxy.

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H. Wahl, J. Rankin, A. Venkataraman, et. al.
Tue, 28 Mar 23
36/81

Comments: 73 pages with Appendix, many figures. arXiv admin note: text overlap with arXiv:2210.10896

Novel application to estimate the mass-loss and the dust-formation rates in O-type gamma-ray binaries using near-infrared photometry [HEAP]

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http://arxiv.org/abs/2303.14530


We have performed the near-infrared photometric monitoring observations of two TeV gamma-ray binaries with O-stars (LS 5039 and 1FGL J1018.6-5856), using IRSF/SIRIUS at SAAO, in order to study the stellar parameters and their perturbations caused by the binary interactions. The whole orbital phase was observed multiple times and no significant variabilities including orbital modulations are detected for both targets. Assuming that the two systems are colliding wind binaries, we estimate the amplitude of flux variation caused by the difference in the optical depth of O-star wind at inferior conjunction, where the star is seen through the cavity created by pulsar wind, and other orbital phases without pulsar-wind intervention. The derived amplitude is <0.001 mag, which is about two orders of magnitude smaller than the observed upper limit. Also using the upper limits of the near-infrared variability, we for the first time obtain the upper limit of the dust formation rate resulting from wind-wind collision in O-star gamma-ray binaries.

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Y. Moritani, A. Kawachi, A. Okazaki, et. al.
Tue, 28 Mar 23
46/81

Comments: 7 figures, 2 tables, Accepted to publications in PASJ

The Need For Speed: Rapid Refitting Techniques for Bayesian Spectral Characterization of the Gravitational Wave Background Using PTAs [HEAP]

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http://arxiv.org/abs/2303.15442


Current pulsar timing array (PTA) techniques for characterizing the spectrum of a nanohertz-frequency stochastic gravitational-wave background (SGWB) begin at the stage of timing data. This can be slow and memory intensive with computational scaling that will worsen PTA analysis times as more pulsars and observations are added. Given recent evidence for a common-spectrum process in PTA data sets and the need to understand present and future PTA capabilities to characterize the SGWB through large-scale simulations, we have developed efficient and rapid approaches that operate on intermediate SGWB analysis products. These methods refit SGWB spectral models to previously-computed Bayesian posterior estimations of the timing power spectra. We test our new methods on simulated PTA data sets and the NANOGrav $12.5$-year data set, where in the latter our refit posterior achieves a Hellinger distance from the current full production-level pipeline that is $\lesssim 0.1$. Our methods are $\sim10^2$–$10^4$ times faster than the production-level likelihood and scale sub-linearly as a PTA is expanded with new pulsars or observations. Our methods also demonstrate that SGWB spectral characterization in PTA data sets is driven by the longest-timed pulsars with the best-measured power spectral densities which is not necessarily the case for SGWB detection that is predicated on correlating many pulsars. Indeed, the common-process spectral properties found in the NANOGrav $12.5$-year data set are given by analyzing only the $\sim10$ longest-timed pulsars out of the full $45$ pulsar array, and we find that the “shallowing” of the common-process power-law model occurs when gravitational-wave frequencies higher than $\sim 50$~nanohertz are included. The implementation of our methods is openly available as a software suite to allow fast and flexible PTA SGWB spectral characterization and model selection.

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W. Lamb, S. Taylor and R. Haasteren
Tue, 28 Mar 23
50/81

Comments: 19 pages, 12 figures. Submitting to Physical Review D

Identifying gravitationally lensed supernovae within the Zwicky Transient Facility public survey [HEAP]

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http://arxiv.org/abs/2303.15439


Strong gravitational lensing of supernovae is exceedingly rare. To date, only a handful of lensed supernovae are known. Despite their rarity, lensed supernovae have emerged as one of the most promising methods for measuring the current expansion rate of the Universe and breaking the Hubble tension. We present an extensive search for gravitationally lensed supernovae within the Zwicky Transient Facility (ZTF) public survey, covering 12,524 transients with good light curves discovered during four years of observations. We crossmatch a catalogue of known and candidate lens galaxies with our transient sample and find only one coincident source, which was due to chance alignment. To search for supernovae magnified by unknown lens galaxies, we test multiple methods that have been suggested in the literature, for the first time on real data. This includes selecting objects with extremely red colours and those that appear inconsistent with the host galaxy redshift. In both cases, we find a few hundred candidates, most of which are due to contamination from activate galactic nuclei, bogus detections, or unlensed supernovae. The false positive rate from these methods presents significant challenges for future surveys. In total, 65 unique transients were identified across all of our selection methods that required detailed manual rejection, which would be infeasible for larger samples. Overall, we do not find any compelling candidates for lensed supernovae, which is broadly consistent with previous estimates for the rate of lensed supernovae in the ZTF public survey and the number expected to pass the selection cuts we apply.

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M. Magee, A. Murieta, T. Collett, et. al.
Tue, 28 Mar 23
51/81

Comments: Submitted

Impact of jets on kilonova photometric and polarimetric emission from binary neutron star mergers [HEAP]

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http://arxiv.org/abs/2303.14277


A merger of binary neutron stars creates heavy unstable elements whose radioactive decay produces a thermal emission known as a kilonova. In this paper, we predict the photometric and polarimetric behaviour of this emission by performing 3-D Monte Carlo radiative transfer simulations. In particular, we choose three hydrodynamical models for merger ejecta, two including jets with different luminosities and one without a jet structure, to help decipher the impact of jets on the light curve and polarimetric behaviour. In terms of photometry, we find distinct color evolutions across the three models. Models without a jet show the highest variation in light curves for different viewing angles. In contrast, to previous studies, we find models with a jet to produce fainter kilonovae when viewed from orientations close to the jet axis, compared to a model without a jet. In terms of polarimetry, we predict relatively low levels (<~0.3-0.4%) at all orientations that, however, remain non-negligible until a few days after the merger and longer than previously found. Despite the low levels, we find that the presence of a jet enhances the degree of polarization at wavelengths ranging from 0.25 to 2.5\micron, an effect that is found to increase with the jet luminosity. Thus, future photometric and polarimetric campaigns should observe kilonovae in blue and red filters for a few days after the merger to help constrain the properties of the ejecta (e.g. composition) and jet.

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M. Shrestha, M. Bulla, L. Nativi, et. al.
Tue, 28 Mar 23
80/81

Comments: 11 pages, 7 figures, submitted to MNRAS, comments welcome

Formation and Evolution of Coherent Structures in 3D Strongly Turbulent Magnetized Plasmas [HEAP]

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http://arxiv.org/abs/2303.15351


We review the current literature on the formation of Coherent Structures (CoSs) in strongly turbulent 3D magnetized plasmas. CoSs (Current Sheets (CS), magnetic filaments, large amplitude magnetic disturbances, vortices, and shocklets) appear intermittently inside a turbulent plasma and are collectively the locus of magnetic energy transfer (dissipation) into particle kinetic energy, leading to heating and/or acceleration of the latter. CoSs and especially CSs are also evolving and fragmenting, becoming locally the source of new clusters of CoSs. Strong turbulence can be generated by the nonlinear coupling of large amplitude unstable plasma modes, by the explosive reorganization of large scale magnetic fields, or by the fragmentation of CoSs. A small fraction of CSs inside a strongly turbulent plasma will end up reconnecting. Magnetic Reconnection (MR) is one of the potential forms of energy dissipation of a turbulent plasma. Analysing the evolution of CSs and MR in isolation from the surrounding CoSs and plasma flows may be convenient for 2D numerical studies, but it is far from a realistic modeling of 3D astrophysical, space and laboratory environments, where strong turbulence can be exited, as e.g. in the solar wind, the solar atmosphere, solar flares and Coronal Mass Ejections (CMEs), large scale space and astrophysical shocks, the magnetosheath, the magnetotail, astrophysical jets, Edge Localized Modes (ELMs) in confined laboratory plasmas (TOKAMAKS), etc.

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L. Vlahos and H. Isliker
Tue, 28 Mar 23
81/81

Comments: 27 pages, 31 figures; review; accepted for publication in Physics of Plasmas 2023

Correlation study of temporal and emission properties of quiescent magnetars [HEAP]

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http://arxiv.org/abs/2303.13765


We measured temporal and emission properties of quiescent magnetars using archival Chandra and XMM-Newton data, produced a list of the properties for 17 magnetars, and revisited previously suggested correlations between the properties. Our studies carried out with a larger sample, better spectral characterizations, and more thorough analyses not only confirmed previously-suggested correlations but also found new ones. The observed correlations differ from those seen in other neutron-star populations but generally accord with magnetar models. Specifically, the trends of the intriguing correlations of blackbody luminosity ($L_{\rm BB}$) with the spin-inferred dipole magnetic field strength ($B_{\rm S}$) and characteristic age ($\tau_{\rm c}$) were measured to be $L_{\rm BB}\propto B_{\rm S}^{1.5}$ and $L_{\rm BB}\propto \tau_{\rm c}^{-0.6}$, supporting the twisted magnetosphere and magnetothermal evolution models for magnetars. We report the analysis results and discuss our findings in the context of magnetar models.

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J. Seo, J. Lee and H. An
Mon, 27 Mar 23
1/59

Comments: 19 pages, 4 figures, accepted for publication in JKAS

A tight universal relation between the shape eccentricity and the moment of inertia for rotating neutron stars [HEAP]

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http://arxiv.org/abs/2303.14130


Universal relations that are insensitive to the equation of state (EoS) are useful in reducing the parameter space when measuring global quantities of neutron stars (NSs). In this paper, we reveal a new universal relation that connects the eccentricity to the radius and moment of inertia of rotating NSs. We demonstrate that the universality of this relation holds for both conventional NSs and bare quark stars (QSs) in the slow rotation approximation, albeit with different relations. The maximum relative deviation is approximately $1\%$ for conventional NSs and $0.1\%$ for QSs. Additionally, we show that the universality still exists for fast-rotating NSs if we use the dimensionless spin to characterize their rotation. The new universal relation will be a valuable tool to reduce the number of parameters used to describe the shape and multipoles of rotating NSs, and it may also be used to infer the eccentricity or moment of inertia of NSs in future X-ray observations.

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Y. Gao, L. Shao and J. Steinhoff
Mon, 27 Mar 23
2/59

Comments: 6 pages, 4 figures

Search for neutrino lines from dark matter annihilation and decay with IceCube [HEAP]

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http://arxiv.org/abs/2303.13663


Dark Matter particles in the Galactic Center and halo can annihilate or decay into a pair of neutrinos producing a monochromatic flux of neutrinos. The spectral feature of this signal is unique and it is not expected from any astrophysical production mechanism. Its observation would constitute a dark matter smoking gun signal. We performed the first dedicated search with a neutrino telescope for such signal, by looking at both the angular and energy information of the neutrino events. To this end, a total of five years of IceCube’s DeepCore data has been used to test dark matter masses ranging from 10~GeV to 40~TeV. No significant neutrino excess was found and upper limits on the annihilation cross section, as well as lower limits on the dark matter lifetime, were set. The limits reached are of the order of $10^{-24}$~cm$^3/s$ for an annihilation and up to $10^{27}$ seconds for decaying Dark Matter. Using the same data sample we also derive limits for dark matter annihilation or decay into a pair of Standard Model charged particles.

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I. Collaboration, R. Abbasi, M. Ackermann, et. al.
Mon, 27 Mar 23
3/59

Comments: N/A

The Astri Mini-Array of Cherenkov Telescopes [HEAP]

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http://arxiv.org/abs/2303.14079


We will describe the current status of the ASTRI Mini-Array, under construction at the Teide Astronomical Observatory in Tenerife, Spain. The final layout of the array will include nine small Cherenkov telescopes covering an area of about 650 x 270 square meters. The ASTRI telescopes adopt a dual-mirror Schwarzchild-Couder aplanatic optical design. In the focal plane, the ASTRI camera, based on silicon photo-multiplier detectors, will cover a large field-of-view ( > 10 deg in diameter). This system also provides good gamma-ray sensitivity at very high energies (VHE, above 10 TeV) combined with a good angular resolution. The scientific goals of the ASTRI Mini-Array include spectral and morphological characterization of the LHAASO sources and other Pevatron candidates, studies of PWNe and TeV halos, Blazar monitoring at VHE, fundamental physics and follow-up of transient events. The beginning of the scientific operations is planned for mid 2025. The first three years will be dedicated to the core science and the ASTRI Mini-Array will be run as an experiment. It will gradually move towards an observatory model in the following years, open to the community.

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A. Giuliani
Mon, 27 Mar 23
6/59

Comments: Accepted Proceeding of the “7th Heidelberg International Symposium on High-Energy Gamma-Ray Astronomy (Gamma2022)”, 4-8 July 2022, Barcelona, Spain

Analytic understanding of the resonant nature of Kozai Lidov Cycles with a precessing quadruple potential [HEAP]

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http://arxiv.org/abs/2303.13579


The very long-term evolution of the hierarchical restricted three-body problem with a precessing quadruple potential is studied analytically. This problem describes the evolution of a star and a planet which are perturbed either by a (circular and not too inclined) binary star system or by one other star and a second more distant star, as well as a perturbation by one distant star and the host galaxy or a compact-object binary system orbiting a massive black hole in non-spherical nuclear star clusters \citep{arXiv:1705.02334v2, arXiv:1705.05848v2}. Previous numerical experiments have shown that when the precession frequency is comparable to the Kozai-Lidov time scale, long term evolution emerges that involves extremely high eccentricities with potential applications for a broad scope of astrophysical phenomena including systems with merging black holes, neutron stars or white dwarfs. We show that a central ingredient of the dynamics is a resonance between the perturbation frequency and the precession frequency of the eccentricity vector in the regime where the eccentricity vector, the precession axis and the quadruple direction are closely aligned. By averaging the secular equations of motion over the Kozai-Lidov Cycles we solve the problem analytically in this regime.

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Y. Klein and B. Katz
Mon, 27 Mar 23
9/59

Comments: 5 pages, 2 figures

Borexino's search for low-energy neutrinos associated with gravitational wave events from GWTC-3 database [HEAP]

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http://arxiv.org/abs/2303.13876


The search for neutrino events in correlation with gravitational wave (GW) events for three observing runs (O1, O2 and O3) from 09/2015 to 03/2020 has been performed using the Borexino data-set of the same period. We have searched for signals of neutrino-electron scattering with visible energies above 250 keV within a time window of 1000 s centered at the detection moment of a particular GW event. Two types of incoming neutrino spectra were considered: the mono-energetic line and the spectrum expected from supernovae. The same spectra were considered for electron antineutrinos detected through inverse beta-decay (IBD) reaction. GW candidates originated by merging binaries of black holes (BHBH), neutron stars (NSNS) and neutron star and black hole (NSBH) were analysed separately. In total, follow-ups of 74 out of 93 gravitational waves reported in the GWTC-3 catalog were analyzed and no statistically significant excess over the background was observed. As a result, the strongest upper limits on GW-associated neutrino and antineutrino fluences for all flavors (\nu_e, \nu_\mu, \nu_\tau) have been obtained in the (0.5 – 5.0) MeV neutrino energy range.

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B. Basilico, G. Bellini, J. Benziger, et. al.
Mon, 27 Mar 23
12/59

Comments: 13 pages, 8 figures

Compton-Getting effect due to terrestrial orbital motion observed on cosmic ray flow from Mexico-city Neutron Monitor [HEAP]

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http://arxiv.org/abs/2303.14101


We look for a diurnal anisotropy in the cosmic ray flow, using the Mexico-City Neutron Monitor (NM) detector, due to the Earth’s orbital motion and predicted by Compton-Getting (C-G) in 1935, as a first-order relativistic effect. The Mexico-City NM’s geographic latitude is not very high ($19.33^{\circ}$N), and it has a high cutoff geomagnetic rigidity (8.2 GV) and mountain altitude (2274 m asl) favoring the observation of the C-G effect. Furthermore, during the solar cycle minima, the galactic cosmic ray flux is maxima, and the solar magnetic field gets weakened, with a dipolar pattern. Its influence on cosmic rays reaching Earth is the smallest. Analysis of the combined counting rate during two solar minima, 2008 and 2019, from Mexico-city NM’s data yields the C-G effect with an amplitude variation of (0.043$\pm$ 0.019)\%, and phase of (6.15$\pm$ 1.71) LT. The expected amplitude variation is 0.044\%, and the phase of 6.00 LT.

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C. Navia, M. Oliveira and A. Nepomuceno
Mon, 27 Mar 23
15/59

Comments: 8 pages, 6 figures

First ejection from the PSR B1259-63/LS 2883 high mass gamma-ray binary detected during the 2021-2024 binary cycle [HEAP]

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http://arxiv.org/abs/2303.13595


LS 2883/PSR B1259-63 is a high mass, eccentric gamma-ray binary that has previously been observed to eject X-ray emitting material. We report the results of recent Chandra observations near binary apastron in which a new X-ray emitting clump of matter was detected. The clump has a high projected velocity of $v_{\perp}\approx 0.07c$ and hard X-ray spectrum, which fits an absorbed power-law model with $\Gamma=1.1\pm0.3$. Although clumps with similar velocities and spectra were detected in some of the previous binary cycles, no resolved clumps were seen near apastron in the preceding cycle of 2017-2021.

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J. Hare, G. Pavlov, O. Kargaltsev, et. al.
Mon, 27 Mar 23
22/59

Comments: RNAAS

SKA sensitivity for possible radio emission from dark matter in Omega Centauri [HEAP]

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http://arxiv.org/abs/2303.14117


Omega Centauri, the largest known globular cluster in the Milky Way, is believed to be the remains of a dwarf galaxy’s core. Giving its potential abundance of dark matter (DM), it is an attractive target for investigating the nature of this elusive substance in our local environment. Our study demonstrates that by observing Omega Centauri with the SKA for 1000 hours, we can detect synchrotron radio or Inverse Compton (IC) emissions from the DM annihilation products. It enables us to constrain the cross-section of DM annihilation down to $\sim {\rm 10^{-30}~cm^3~s^{-1}}$ for DM mass from several $\rm{GeV}$ to $\rm{100~GeV}$, which is much stronger compared with other observations. Additionally, we explore the axion, another well-motivated DM candidate, and provide stimulated decay calculations. It turns out that the sensitivity can reach $g_{\rm{a\gamma\gamma}} \sim 10^{-10} ~\rm{GeV^{-1}}$ for $2\times 10^{-7} ~\rm{eV} < m_a < 2\times 10^{-4} ~\rm{eV}$.

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G. Wang, Z. Chen, L. Zu, et. al.
Mon, 27 Mar 23
24/59

Comments: 19 pages, 8 figures

Fast and Not-so-Furious: Case Study of the Fast and Faint Type IIb SN 2021bxu [HEAP]

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http://arxiv.org/abs/2303.13581


We present photometric and spectroscopic observations and analysis of SN~2021bxu (ATLAS21dov), a low-luminosity, fast-evolving Type IIb supernova (SN). SN~2021bxu is unique, showing a large initial decline in brightness followed by a short plateau phase. With $M_r = -15.93 \pm 0.16\, \mathrm{mag}$ during the plateau, it is at the lower end of the luminosity distribution of stripped-envelope supernovae (SE-SNe) and shows a distinct $\sim$10 day plateau not caused by H- or He-recombination. SN~2021bxu shows line velocities which are at least $\sim1500\,\mathrm{km\,s^{-1}}$ slower than typical SE-SNe. It is photometrically and spectroscopically similar to Type IIb SNe during the photospheric phases of evolution, with similarities to Ca-rich IIb SNe. We find that the bolometric light curve is best described by a composite model of shock interaction between the ejecta and an envelope of extended material, combined with a typical SN~IIb powered by the radioactive decay of $^{56}$Ni. The best-fit parameters for SN~2021bxu include a $^{56}$Ni mass of $M_{\mathrm{Ni}} = 0.029^{+0.004}{-0.005}\,\mathrm{M{\odot}}$, an ejecta mass of $M_{\mathrm{ej}} = 0.57^{+0.04}{-0.03}\,\mathrm{M{\odot}}$, and an ejecta kinetic energy of $K_{\mathrm{ej}} = 9.3^{+0.7}{-0.6} \times 10^{49}\, \mathrm{erg}$. From the fits to the properties of the extended material of Ca-rich IIb SNe we find a trend of decreasing envelope radius with increasing envelope mass. SN~2021bxu has $M{\mathrm{Ni}}$ on the low end compared to SE-SNe and Ca-rich SNe in the literature, demonstrating that SN~2021bxu-like events are rare explosions in extreme areas of parameter space. The progenitor of SN~2021bxu is likely a low mass He star with an extended envelope.

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D. Desai, C. Ashall, B. Shappee, et. al.
Mon, 27 Mar 23
32/59

Comments: 18 pages, 15 figures, submitted to MNRAS

A detailed analysis of X-ray emission line velocities of Capella from over 20 years of Chandra/HETG spectroscopy [HEAP]

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http://arxiv.org/abs/2303.13924


Capella is the brightest chromospherically active binary in the sky, hosting a cooler G8III giant (Aa) and an hotter G1III companion (Ab). The source has been extensively observed in the X-rays in the past decades not only for its astrophysical interest in the field of corona sources, but also for in-flight calibrations of space-based X-ray instruments. In 2006, it was demonstrated using Chandra/HETG observations that Aa is the main contributor to Capella’s X-ray emission, as the centroid energies of the emission lines are Doppler shifted along the orbit of the G8III giant (an aspect that has to be taken in consideration for calibration activities of X-ray instruments). In this paper, we extend the previous analysis performed in 2006 by re-analyzing in an homogeneous way all Chandra/HETG observations performed in the direction of Capella. By doubling the amount of data available, we strengthened the conclusion that Capella Aa is the dominant emitter in soft X-rays. We did not find any evidence of a statistically significant contribution to this emission by the Ab giant. Our findings are discussed also in light of the incoming launch of the XRISM mission (spring 2023).

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E. Bozzo, D. Huenemoerder, N. Produit, et. al.
Mon, 27 Mar 23
34/59

Comments: Accepted for publication on MNRAS letters

SN 2019odp: A Massive Oxygen-Rich Type Ib Supernova [HEAP]

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http://arxiv.org/abs/2303.14146


We present and analyze observations of the Type Ib supernova (SN) 2019odp (a.k.a ZTF19abqwtfu) covering epochs within days of the explosion to the nebular phase at 360 d post-explosion. We discuss them in the context of recombination cooling emission for the early excess emission and consider progenitor models based on the nebular phase spectra. Our observations include photometric observations mainly in the optical and low to medium-resolution spectroscopic observations covering the complete observable time-range. We expand on existing methods to derive oxygen mass estimates from nebular phase spectroscopy. Our spectroscopic observations confirm the presence of He in the SN ejecta and we thus (re)classify it as a Type Ib supernova. From the pseudo-bolometric lightcurve we estimate a high ejecta mass $M_\text{ej} \sim 4 – 7~M_\odot$. The high ejecta mass, large nebular [O I]/[Ca II] line flux ratio ($1.2 – 1.9$) and an oxygen mass above $\gtrapprox 0.5\, M_\odot$ point towards a progenitor with pre-explosion mass higher than $18\,M_\odot$. The compact nature of the progenitor ($\lesssim 10\,R_\odot$) suggests a Wolf-Rayet (WR) star as progenitor.

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T. Schweyer, J. Sollerman, A. Jerkstrand, et. al.
Mon, 27 Mar 23
35/59

Comments: Submitted to A&A

Spectroscopic Signature of a Re-established Accretion Disk in Symbiotic-like Recurrent Nova RS Ophiuchi [HEAP]

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http://arxiv.org/abs/2303.14135


A novel method is presented which can pin down the time the accretion disk re-established itself in the RS Oph system after it experienced a nova disruption. The method is based on the re-ionisation of the ejecta by photoionisation from the radiation released in the boundary layer from accretion.

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A. Azzollini, S. Shore and P. Kuin
Mon, 27 Mar 23
36/59

Comments: 3 pages, 1 figure

Absorption Line Observations of H$_3^+$ and CO in Sight Lines Toward the Vela and W28 Supernova Remnants [HEAP]

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http://arxiv.org/abs/2303.13689


Supernova remnants act as particle accelerators, providing the cosmic-ray protons that permeate the interstellar medium and initiate the ion-molecule reactions that drive interstellar chemistry. Enhanced fluxes of cosmic-ray protons in close proximity to supernova remnants have been inferred from observations tracing particle interactions with nearby molecular gas. Here I present observations of H$_3^+$ and CO absorption, molecules that serve as tracers of the cosmic-ray ionization rate and gas density, respectively, in sight lines toward the W28 and Vela supernova remnants. Cosmic-ray ionization rates inferred from these observations range from about 2–10 times the average value in Galactic diffuse clouds ($\sim 3\times10^{-16}$ s$^{-1}$), suggesting that the gas being probed is experiencing an elevated particle flux. While it is difficult to constrain the line-of-sight location of the absorbing gas with respect to the supernova remnants, these results are consistent with a scenario where cosmic rays are diffusing away from the acceleration site and producing enhanced ionization rates in the surrounding medium.

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N. Indriolo
Mon, 27 Mar 23
37/59

Comments: 26 pages, 6 figures, 4 tables; accepted for publication in ApJ

Precise Measurements of Self-absorbed Rising Reverse Shock Emission from Gamma-ray Burst 221009A [HEAP]

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http://arxiv.org/abs/2303.13583


The deaths of massive stars are sometimes accompanied by the launch of highly relativistic and collimated jets. If the jet is pointed towards Earth, we observe a “prompt” gamma-ray burst due to internal shocks or magnetic reconnection events within the jet, followed by a long-lived broadband synchrotron afterglow as the jet interacts with the circum-burst material. While there is solid observational evidence that emission from multiple shocks contributes to the afterglow signature, detailed studies of the reverse shock, which travels back into the explosion ejecta, are hampered by a lack of early-time observations, particularly in the radio band. We present rapid follow-up radio observations of the exceptionally bright gamma-ray burst GRB 221009A which reveal an optically thick rising component from the reverse shock in unprecedented detail both temporally and in frequency space. From this, we are able to constrain the size, Lorentz factor, and internal energy of the outflow while providing accurate predictions for the location of the peak frequency of the reverse shock in the first few hours after the burst.

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J. Bright, L. Rhodes, W. Farah, et. al.
Mon, 27 Mar 23
44/59

Comments: 11 figures, 4 tables

Classification of blazar candidates of unknown type in Fermi 4LAC by unanimous voting from multiple Machine Learning Algorithms [HEAP]

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http://arxiv.org/abs/2303.14137


The Fermi fourth catalog of active galactic nuclei (AGNs) data release 3 (4LAC-DR3) contains 3407 AGNs, out of which 755 are flat spectrum radio quasars (FSRQs), 1379 are BL Lacertae objects (BL Lacs), 1208 are blazars of unknown (BCUs) type, while 65 are non AGNs. Accurate categorization of many unassociated blazars still remains a challenge due to the lack of sufficient optical spectral information. The aim of this work is to use high-precision, optimized machine learning (ML) algorithms to classify BCUs into BL Lacs and FSRQs. To address this, we selected the 4LAC-DR3 Clean sample (i.e., sources with no analysis flags) containing 1115 BCUs. We employ five different supervised ML algorithms, namely, random forest, logistic regression, XGBoost, CatBoost, and neural network with seven features: Photon index, synchrotron-peak frequency, Pivot Energy, Photon index at Pivot_Energy, Fractional variability, $\nu F\nu$ at synchrotron-peak frequency, and Variability index. Combining results from all models leads to better accuracy and more robust predictions. These five methods together classified 610 BCUs as BL Lacs and 333 BCUs as FSRQs with a classification metric area under the curve $>$ 0.96. Our results are significantly compatible with recent studies as well. The output from this study provides a larger blazar sample with many new targets that could be used for forthcoming multi-wavelength surveys. This work can be further extended by adding features in X-rays, UV, visible, and radio wavelengths.

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A. Agarwal
Mon, 27 Mar 23
45/59

Comments: 22 pages, 10 figures, 3 tables, Accepted in ApJ

Reflection and timing study of the transient black hole X-ray binary MAXI J1803-298 with NuSTAR [HEAP]

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http://arxiv.org/abs/2303.13718


The transient black hole X-ray binary MAXI J1803-298 was discovered on 2021 May 1, as it went into outburst from a quiescent state. As the source rose in flux it showed periodic absorption dips and fit the timing and spectral characteristics of a hard state accreting black hole. We report on the results of a Target-of-Opportunity observation with NuSTAR obtained near the peak outburst flux beginning on 2021 May 13, after the source had transitioned into an intermediate state. MAXI J1803-298 is variable across the observation, which we investigate by extracting spectral and timing products separately for different levels of flux throughout the observation. Our timing analysis reveals two distinct potential QPOs which are not harmonically related at 5.4+/-0.2 Hz and 9.4+/-0.3 Hz, present only during periods of lower flux. With clear relativistic reflection signatures detected in the source spectrum, we applied several different reflection models to the spectra of MAXI J1803-298. Here we report our results, utilizing high density reflection models to constrain the disk geometry, and assess changes in the spectrum dependent on the source flux. With a standard broken power-law emissivity, we find a near-maximal spin for the black hole, and we are able to constrain the inclination of the accretion disk at 75+/-2 degrees, which is expected for a source that has shown periodic absorption dips. We also significantly detect a narrow absorption feature at 6.91+/-0.06 keV with an equivalent width between 4 and 9 eV, which we interpret as the signature of a disk wind.

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B. Coughenour, J. Tomsick, G. Mastroserio, et. al.
Mon, 27 Mar 23
46/59

Comments: 14 pages, 8 figures, accepted for publication (ApJ)

Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow [HEAP]

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http://arxiv.org/abs/2303.14172


We report the discovery of GRB 221009A, the highest flux gamma-ray burst ever observed by the Fermi Gamma-ray Burst Monitor (GBM). This GRB has continuous prompt emission lasting more than 600 seconds, afterglow visible in the \gbm energy range (8 keV–40 MeV), and total energetics higher than any other burst in the GBM sample. By using a variety of new and existing analysis techniques we probe the spectral and temporal evolution of GRB 221009A. We find no emission prior to the GBM trigger time (t0; 2022 October 9 at 13:16:59.99 UTC), indicating that this is the time of prompt emission onset. The triggering pulse exhibits distinct spectral and temporal properties suggestive of shock-breakout with significant emission up to $\sim$15\,MeV. We characterize the onset of external shock at \t0+600\,s and find evidence of a plateau region in the early-afterglow phase which transitions to a slope consistent with \swift-XRT afterglow measurements. We place the total energetics of GRB 221009A in context with the rest of the GBM sample and find that this GRB has the highest total isotropic-equivalent energy ($\textrm{E}{\gamma,\textrm{iso}}=1.0\times10^{55}$\,erg) and second highest isotropic-equivalent luminosity ($\textrm{L}{\gamma,\textrm{iso}}=9.9\times10^{53}$\,erg/s) based on redshift of z = 0.151. These extreme energetics are what allowed GBMto observe the continuously emitting central engine from the beginning of the prompt emission phase through the onset of early afterglow.

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S. Lesage, P. Veres, M. Briggs, et. al.
Mon, 27 Mar 23
53/59

Comments: 24 pages 7 figures

Constraints on the baryonic load of gamma-ray bursts using ultra-high energy cosmic rays [HEAP]

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http://arxiv.org/abs/2303.13781


Ultra-high energy cosmic rays are the most extreme energetic particles detected on Earth, however, their acceleration sites are still mysterious. We explore the contribution of low-luminosity gamma-ray bursts to the ultra-high energy cosmic ray flux, since they form the bulk of the nearby population. We analyse a representative sample of these bursts detected by BeppoSAX, INTEGRAL and Swift between 1998-2016, and find they can produce a theoretical cosmic ray flux on Earth of at least $R_\text{UHECR} = 1.2 \times 10^{15}$ particles km$^{-2}$ century$^{-1}$ mol$^{-1}$. No suppression mechanisms can reconcile this value with the flux observed on Earth. Instead, we propose that the jet of low-luminosity gamma-ray bursts propels only the circumburst medium – which is accelerated to relativistic speeds – not the stellar matter. This has implications for the baryonic load of the jet: it should be negligible compared to the leptonic content.

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E. Moore, B. Gendre, N. Orange, et. al.
Mon, 27 Mar 23
56/59

Comments: 5 pages, submitted to MNRAS

Gamma-rays and neutrinos from supernovae of Type Ib/c with late time emission [HEAP]

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http://arxiv.org/abs/2303.13576


Observations of some supernovae (SNe), such as SN 2014C, in the X-ray and radio wavebands revealed a rebrightening over a timescale of about a year since their detection. Such a discovery hints towards the evolution of a hydrogen-poor SN of Type Ib/c into a hydrogen-rich SN of Type IIn, the late time activity being attributed to the interaction of the SN ejecta with a dense hydrogen-rich circumstellar medium (CSM) far away from the stellar core. We compute the neutrino and gamma-ray emission from these SNe, considering interactions between the shock accelerated protons and the non-relativistic CSM protons. Assuming three CSM models inspired by recent electromagnetic observations, we explore the dependence of the expected multi-messenger signals on the CSM characteristics. We also investigate the detection prospects of current and upcoming gamma-ray (Fermi-LAT and Cerenkov Telescope Array) and neutrino (IceCube, IceCube-Gen2 and KM3NeT) telescopes. Our findings are in agreement with the non-detection of neutrinos and gamma-rays from past SNe exhibiting late time emission. Nevertheless, the detection prospects of SNe with late time emission in gamma-rays and neutrinos with the Cerenkov Telescope Array and IceCube-Gen2 (Fermi and IceCube) are promising and could potentially provide new insight into the CSM properties, if the SN burst should occur within $10$ Mpc ($4$ Mpc).

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P. Sarmah, S. Chakraborty, I. Tamborra, et. al.
Mon, 27 Mar 23
58/59

Comments: 9 pages, 4 figures

Redshift determination of blazars for the Cherenkov Telescope Array [HEAP]

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http://arxiv.org/abs/2303.12871


Blazars are the most numerous type of observed high-energy gamma-ray emitters. However, their emission mechanisms and population properties are still not well-understood. Crucial to this understanding are their cosmological redshifts, which are often not easy to obtain. This presents a great challenge to the next-generation ground-based observatory for very-high-energy gamma rays, the Cherenkov Telescope Array (CTA), which aims to detect a large number of distant blazars to study their intrinsic emission properties and to place tight constraints on the extragalactic background light density, amongst others. The successful investigation of these subjects needs a precise redshift determination. Motivated by these challenges, the CTA redshift task force initiated more than 3 years ago a spectroscopic observing program using some of the largest optical and infrared telescopes to measure the redshifts of a large fraction of blazars that are likely to be detected with CTA. In this proceedings, we give an overview of the CTA redshift task force, discuss some of the difficulties associated with measuring the redshifts of blazars and present our sample selection and observing strategies. We end the proceedings with reporting selected results from the program, the on-going collaborative efforts and our plans for the future.

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E. Kasai, P. Goldoni, S. Pita, et. al.
Fri, 24 Mar 23
11/56

Comments: 4 pages, 2 figures, IAU Symposium 375

AstroSat and NuSTAR observations of XTE J1739-285 during the 2019-2020 outburst [HEAP]

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http://arxiv.org/abs/2303.13085


We report results from a study of XTE J1739-285, a transient neutron star low mass X-ray binary observed with AstroSat and NuSTAR during its 2019-2020 outburst. We detected accretion-powered X-ray pulsations at 386 Hz during very short intervals (0.5–1 s) of X-ray flares. These flares were observed during the 2019 observation of XTE J1739-285. During this observation, we also observed a correlation between intensity and hardness ratios, suggesting an increase in hardness with the increase in intensity. Moreover, a thermonuclear X-ray burst detected in our AstroSat observation during the 2020 outburst revealed the presence of coherent burst oscillations at 383 Hz during its decay phase. The frequency drift of 3 Hz during X-ray burst can be explained with r modes. Thus, making XTE J1739-285 belong to a subset of NS-LMXBs which exhibit both nuclear- and accretion-powered pulsations. The power density spectrum created using the AstroSat-LAXPC observations in 2020 showed the presence of a quasi-periodic oscillation at ~ 0.83 Hz. Our X-ray spectroscopy revealed significant changes in the spectra during the 2019 and 2020 outburst. We found a broad iron line emission feature in the X-ray spectrum during the 2020 observation, while this feature was relatively narrow and has a lower equivalent width in 2019,~when the source was accreting at higher rates than 2020.

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A. Beri, R. Sharma, P. Roy, et. al.
Fri, 24 Mar 23
13/56

Comments: Accepted for publication in MNRAS, 13 pages

Tidal Peeling Events: low-eccentricity tidal disruption of a star by a stellar-mass black hole [HEAP]

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http://arxiv.org/abs/2303.12846


Close encounters between stellar-mass black holes (BHs) and stars occur frequently in dense star clusters and in the disks of active galactic nuclei (AGNs). Recent studies have shown that in highly eccentric close encounters, the star can be tidally disrupted by the BH (micro-tidal disruption event, or micro-TDE), resulting in rapid mass accretion and possibly bright electromagnetic signatures. Here we consider a scenario in which the star might approach the stellar-mass BH in a gradual, nearly circular inspiral, under the influence of dynamical friction on a circum-binary gas disk or three-body interactions in a star cluster. We perform hydro-dynamical simulations of this scenario using the smoothed particle hydrodynamics code PHANTOM. We find that the mass of the star is slowly stripped away by the BH. We call this gradual tidal disruption a “tidal-peeling event”, or a TPE. Depending on the initial distance and eccentricity of the encounter, TPEs might exhibit significant accretion rates and orbital evolution distinct from those of a typical (eccentric) micro-TDE.

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C. Xin, Z. Haiman, R. Perna, et. al.
Fri, 24 Mar 23
16/56

Comments: N/A

Search for the evaporation of primordial black holes with H.E.S.S [HEAP]

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http://arxiv.org/abs/2303.12855


Primordial Black Holes (PBHs) are hypothetical black holes predicted to have been formed from density fluctuations in the early Universe. PBHs with an initial mass around $10^{14}-10^{15}$g are expected to end their evaporation at present times in a burst of particles and very-high-energy (VHE) gamma rays. Those gamma rays may be detectable by the High Energy Stereoscopic System (H.E.S.S.), an array of imaging atmospheric Cherenkov telescopes. This paper reports on the search for evaporation bursts of VHE gamma rays with H.E.S.S., ranging from 10 to 120 seconds, as expected from the final stage of PBH evaporation and using a total of 4816 hours of observations. The most constraining upper limit on the burst rate of local PBHs is $2000$ pc$^{-3}$ yr$^{-1}$ for a burst interval of 120 seconds, at the 95\% confidence level. The implication of these measurements for PBH dark matter are also discussed.

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H. collaboration, F. Aharonian, F. Benkhali, et. al.
Fri, 24 Mar 23
20/56

Comments: Accepted for publication in JCAP, corresponding authors: F.Brun, J-F. Glicenstein, V. Marandon, T. Tavernier

A Sensitive Search for Supernova Emission Associated with the Extremely Energetic and Nearby GRB 221009A [HEAP]

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http://arxiv.org/abs/2303.12849


We report observations of the optical counterpart of the long gamma-ray burst (LGRB) GRB 221009A. Due to the extreme rarity of being both nearby ($z = 0.151$) and highly energetic ($E_{\gamma,\mathrm{iso}} \geq 10^{54}$ erg), GRB 221009A offers a unique opportunity to probe the connection between massive star core collapse and relativistic jet formation. Adopting a phenomenological power-law model for the afterglow and host galaxy estimates from high-resolution Hubble Space Telescope imaging, we use Bayesian model comparison techniques to determine the likelihood of an associated SN contributing excess flux to the optical light curve. Though not conclusive, we find moderate evidence ($K_{\rm{Bayes}}=10^{1.2}$) for the presence of an additional component arising from an associated supernova, SN 2022xiw, and find that it must be substantially fainter than SN 1998bw. Given the large and uncertain line-of-sight extinction, we attempt to constrain the supernova parameters ($M_{\mathrm{Ni}}$, $M_{\mathrm{ej}}$, and $E_{\mathrm{KE}}$) under several different assumptions with respect to the host galaxy’s extinction. We find properties that are broadly consistent with previous GRB-associated SNe: $M_{\rm{Ni}}=0.05$ – $0.25 \rm{M_\odot}$, $M_{\rm{ej}}=3.5$ – $11.1 \rm{M_\odot}$, and $E_{\rm{KE}} = (1.6$ – $5.2) \times 10^{52} \rm{erg}$. We note that these properties are weakly constrained due to the faintness of the supernova with respect to the afterglow and host emission, but we do find a robust upper limit on the Nickel mass of $M_{\rm{Ni}}<0.36$ $\rm{M_\odot}$. Given the tremendous range in isotropic gamma-ray energy release exhibited by GRBs (7 orders of magnitude), the SN emission appears to be decoupled from the central engine in these systems.

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G. Srinivasaragavan, B. Connor, S. Cenko, et. al.
Fri, 24 Mar 23
22/56

Comments: 18 pages, submitted to ApJL, 4 tables, 5 figures

High-Energy Neutrino Fluxes from Hard-TeV BL Lacs [HEAP]

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http://arxiv.org/abs/2303.13025


Blazars have been pointed out as promising high-energy (HE) neutrinos sources, although the mechanism is still under debate. The blazars with a hard-TeV spectrum, which leptonic models can hardly explain, can be successfully interpreted in the hadronic scenarios. Recently, Aguilar et al. proposed a lepto-hadronic two-zone model to explain the multi-wavelength observations of the six best-known extreme BL Lacs and showed that the hadronic component could mainly interpret very-high-energy (VHE) emission. In this work, we apply this hadronic model to describe the VHE gamma-ray fluxes of 14 extreme BL Lacs and estimate the respective HE neutrino flux from charge-pion decay products. Finally, we compare our result with the diffuse flux observed by the IceCube telescope, showing that the neutrino fluxes from these objects are negligible.

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E. Aguilar-Ruiz, N. Fraija and A. Galván-Gámez
Fri, 24 Mar 23
28/56

Comments: Accepted in Journal of High Energy Astrophysics

A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy [HEAP]

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http://arxiv.org/abs/2303.12912


The majority of long duration ($>2$ s) gamma-ray bursts (GRBs) are believed to arise from the collapse of massive stars \cite{Hjorth+03}, with a small proportion created from the merger of compact objects. Most of these systems are likely formed via standard stellar evolution pathways. However, it has long been thought that a fraction of GRBs may instead be an outcome of dynamical interactions in dense environments, channels which could also contribute significantly to the samples of compact object mergers detected as gravitational wave sources. Here we report the case of GRB 191019A, a long GRB (T_90 = 64.4 +/- 4.5 s) which we pinpoint close (<100 pc projected) to the nucleus of an ancient (>1~Gyr old) host galaxy at z=0.248. The lack of evidence for star formation and deep limits on any supernova emission make a massive star origin difficult to reconcile with observations, while the timescales of the emission rule out a direct interaction with the supermassive black hole in the nucleus of the galaxy, We suggest that the most likely route for progenitor formation is via dynamical interactions in the dense nucleus of the host, consistent with the centres of such galaxies exhibiting interaction rates up to two orders of magnitude larger than typical field galaxies. The burst properties could naturally be explained via compact object mergers involving white dwarfs (WD), neutron stars (NS) or black holes (BH). These may form dynamically in dense stellar clusters, or originate in a gaseous disc around the supermassive black hole. Future electromagnetic and gravitational-wave observations in tandem thus offer a route to probe the dynamical fraction and the details of dynamical interactions in galactic nuclei and other high density stellar systems.

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A. Levan, D. Malesani, B. Gompertz, et. al.
Fri, 24 Mar 23
31/56

Comments: Accepted to Nature Astronomy. This is the submitted version and will differ from the published version due to modifications in the refereeing process

GRB 191019A: a short gamma-ray burst in disguise from the disk of an active galactic nucleus [HEAP]

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http://arxiv.org/abs/2303.12935


Long and short gamma-ray bursts (GRBs), canonically separated at around 2 seconds duration, are associated with different progenitors: the collapse of a massive star and the merger of two compact objects, respectively. GRB 191019A was a long GRB ($T_{90}\sim64$ s). Despite the relatively small redshift z=0.248 and HST followup observations, an accompanying supernova was not detected. In addition, the host galaxy did not have significant star formation activity. Here we propose that GRB 191019A was produced by a binary compact merger, whose prompt emission was stretched in time by the interaction with a dense external medium. This would be expected if the burst progenitor was located in the disk of an active galactic nucleus, as supported by the burst localization close to the center of its host galaxy. We show that the light curve of GRB 191019A can be well modeled by a burst of intrinsic duration t=1.1 s and of energy $E_{\rm{iso}}=10^{51}$ erg seen moderately off-axis, exploding in a medium of density $10^7-10^8$ cm$^{-3}$. The double-peaked light curve carries the telltale features predicted for GRBs in high-density media, where the first peak is produced by the photosphere, and the second by the overlap of reverse shocks that take place before the internal shocks could happen. This would make GRB 191019A the first confirmed stellar explosion from within an accretion disk, with important implications for the formation and evolution of stars in accretion flows and for gravitational waves source populations.

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D. Lazzati, R. Perna, B. Gompertz, et. al.
Fri, 24 Mar 23
46/56

Comments: 6 pages, 2 figures. Submitted to ApJL

Prospective Dark Matter Annihilation Signals From the Sagittarius Dwarf Spheroidal [HEAP]

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http://arxiv.org/abs/2303.13180


The Sagittarius Dwarf Spheroidal galaxy (Sgr) is investigated as a target for DM annihilation searches utilizing J-factor distributions calculated directly from a high-resolution hydrodynamic simulation of the infall and tidal disruption of Sgr around the Milky Way. In contrast to past studies, the simulation incorporates DM, stellar and gaseous components for both the Milky Way and the Sgr progenitor galaxy. The simulated distributions account for significant tidal disruption affecting the DM density profile. Our estimate of the J-factor value for Sgr, $J_{\text{Sgr}}=1.48\times 10^{10}\ \text{M}^2_\odot\ \text{kpc}^{-5}$ ($6.46\times10^{16}\ \text{GeV}\ \text{cm}^{-5}$), is significantly lower than found in prior studies. This value, while formally a lower limit, is likely close to the true J-factor value for Sgr. It implies a DM cross-section incompatibly large in comparison with existing constraints would be required to attribute recently observed $\gamma$-ray emission from Sgr (Crocker, Macias et al. 2022; arXiv:2204.12054) to DM annihilation. We also calculate a J-factor value using an NFW profile fitted to the simulated DM density distribution to facilitate comparison with past studies. This NFW J-factor value supports the conclusion that most past studies have overestimated the dark matter density of Sgr on small scales. This, together with the fact that the Sgr has recently been shown to emit $\gamma$-rays of astrophysical origin, complicate the use of Sgr in indirect DM detection searches.

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T. Venville, A. Duffy, R. Crocker, et. al.
Fri, 24 Mar 23
50/56

Comments: 13 pages, 20 figures. Submitted to MNRAS. Comments welcome

A helium-burning white dwarf binary as a supersoft X-ray source [HEAP]

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http://arxiv.org/abs/2303.13338


Type Ia supernovae are cosmic distance indicators, and the main source of iron in the Universe, but their formation paths are still debated. Several dozen supersoft X-ray sources, in which a white dwarf accretes hydrogen-rich matter from a non-degenerate donor star, have been observed and suggested as Type Ia supernovae progenitors. However, observational evidence for hydrogen, which is expected to be stripped off the donor star during the supernova explosion, is lacking. Helium-accreting white dwarfs, which would circumvent this problem, have been predicted for more than 30 years, also including their appearance as supersoft X-ray sources, but have so far escaped detection. Here we report a supersoft X-ray source with an accretion disk whose optical spectrum is completely dominated by helium, suggesting that the donor star is hydrogen-free. We interpret the luminous and supersoft X-rays as due to helium burning near the surface of the accreting white dwarf. The properties of our system provides evidence for extended pathways towards Chandrasekhar mass explosions based on helium accretion, in particular for stable burning in white dwarfs at lower accretion rates than expected so far. This may allow to recover the population of the sub-energetic so-called Type Iax supernovae, up to 30% of all Type Ia supernovae, within this scenario.

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J. Greiner, C. Maitra, F. Haberl, et. al.
Fri, 24 Mar 23
51/56

Comments: N/A

Black Holes Up Close [HEAP]

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http://arxiv.org/abs/2303.13229


Recent developments have ushered in a new era in the field of black hole astrophysics, providing our first direct view of the remarkable environment near black hole event horizons. These observations have enabled astronomers to confirm long-standing ideas on the physics of gas flowing into black holes with temperatures that are hundreds of times greater than at the center of the Sun. At the same time, the observations have conclusively shown that light rays near a black hole experience large deflections which cause a dark shadow in the center of the image, an effect predicted by Einstein’s theory of General Relativity. With further investment, this field is poised to deliver decades of advances in our understanding of gravity and black holes through new and stringent tests of General Relativity, as well as new insights into the role of black holes as the central engines powering a wide range of astronomical phenomena.

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R. Narayan and E. Quataert
Fri, 24 Mar 23
53/56

Comments: 15 pages, 4 Figs; Nature Perspective

Extreme ion acceleration at extragalactic jet termination shocks [HEAP]

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http://arxiv.org/abs/2303.12636


Extragalactic plasma jets are some of the few astrophysical environments able to confine ultra-high energy cosmic rays, but whether they are capable of accelerating these particles is unknown. In this work, we revisit particle acceleration at relativistic magnetized shocks beyond the local uniform field approximation, by considering the global transverse structure of the jet. Using large two-dimensional particle-in-cell simulations of a relativistic electron-ion plasma jet, we show that the termination shock forming at the interface with the ambient medium accelerates particles up to the confinement limit. The radial structure of the jet magnetic field leads to a relativistic velocity shear that excites a von K\’arm\’an vortex street in the downstream medium trailing behind an over-pressured bubble filled with cosmic rays. Particles are efficiently accelerated at each crossing of the shear flow boundary layers. These findings support that extragalactic plasma jets may be capable of producing ultra-high energy cosmic rays. This extreme particle acceleration mechanism may also apply to microquasar jets.

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B. Cerutti and G. Giacinti
Thu, 23 Mar 23
2/67

Comments: 6 pages, 6 figures, submitted to Astronomy & Astrophysics

Hydrodynamical Evolution of Black-Hole Binaries Embedded in AGN Discs: III. The Effects of Viscosity [HEAP]

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http://arxiv.org/abs/2303.12207


Stellar-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN) discs offer a distinct dynamical channel to produce black hole mergers detected in gravitational waves by LIGO/Virgo. To understand their orbital evolution through interactions with the disc gas, we perform a suite of 2D high-resolution, local shearing box, viscous hydrodynamical simulations of equal-mass binaries. We find that viscosity not only smooths the flow structure around prograde circular binaries, but also greatly raises their accretion rates. The overwhelming positive torque associated with the accretion dominates over the gravitational torque, and drives binary orbital expansion. However, retrograde binaries still experience rapid orbital decay, and prograde eccentric binaries still experience eccentricity damping, despite undergoing outspiral. Our numerical experiments further show that prograde binaries may experience inspiral if the physical sizes of the accretors are sufficiently small, such that the net binary accretion is reduced. Such a dependence of the binary accretion rate on the accretor size can be weaken through boosted accretion either due to a high viscosity or a more isothermal-like equation of state (EOS). Our results widen the explored parameter space for the hydrodynamics of embedded BBHs and demonstrate that their orbital evolution in AGN discs is a complex, multifaceted problem.

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R. Li and D. Lai
Thu, 23 Mar 23
3/67

Comments: 10 pages, 6 figures, submitted to MNRAS. arXiv admin note: text overlap with arXiv:2207.01125