Tag Archives: High Energy Astrophysical Phenomena

Elasticity of neutron star mantle: improved compressible liquid drop model for cylindrical phases [HEAP]

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http://arxiv.org/abs/2305.03603


Neutron stars are the densest objects in the Universe. They have microscopically homogeneous core and heterogeneous crust. In particular, there may be a specific layer inside neutron stars, the mantle, which consists of substantially non-spherical nuclei immersed in a background of relativistic degenerate electrons and quasi-free neutrons. In this paper we reconsider transverse shear modulus for cylindrical phases of the mantle within the framework of compressible liquid drop model. We demonstrate that transverse shear affects the shape of nuclear clusters: their cross-section becomes elliptical. This effect reduces respective elastic constant. Using a simple model we perform all derivations analytically and obtain the expression for the transverse shear modulus, which can be useful for astrophysical applications.

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N. Zemlyakov and A. Chugunov
Mon, 8 May 23
24/63

Comments: 12 pages, 4 figures, published in Universe

Constraints on Undetected Long-Period Binaries in the Known Pulsar Population [HEAP]

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http://arxiv.org/abs/2305.03561


Although neutron star-black hole binaries have been identified through mergers detected in gravitational waves, a pulsar-black hole binary has yet to be detected. While short-period binaries are detectable due to a clear signal in the pulsar’s timing residuals, effects from a long-period binary could be masked by other timing effects, allowing them to go undetected. In particular, a long-period binary measured over a small subset of its orbital period could manifest via time derivatives of the spin-frequency incompatible with isolated pulsar properties. We assess the possibility of pulsars having unknown companions in long-period binaries and put constraints on the range of binary properties that may remain undetected in current data, but that may be detectable with further observations. We find that for 35% of canonical pulsars with published higher order derivatives, the precision of measurements is not enough to confidently reject binarity (period greater than ~2 kyr), and that a black-hole binary companion could not be ruled out for a sample of pulsars without published constraints if the period is greater than 1 kyr. While we find no convincing cases in the literature, we put more stringent limits on orbital period and longitude of periastron for the few pulsars with published higher-order frequency derivatives (n greater than 3). We discuss the detectability of candidates and find that a sample pulsar in a 100 yr orbit could be detectable within 5-10 yr.

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M. Jones, D. Kaplan, M. McLaughlin, et. al.
Mon, 8 May 23
31/63

Comments: 9 pages, 5 figures. Accepted to ApJ

The maximum mass and deformation of rotating strange quark stars with strong magnetic fields [HEAP]

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http://arxiv.org/abs/2305.03055


We study the structure and total energy of a strange quark star (SQS) endowed with a strong magnetic field with different rotational frequencies. The MIT bag model is used, with the density-dependent bag constant for the equation of state (EOS). The EOS is computed considering the Landau quantization effect regarding the strong magnetic fields (up to $5\times10^{17}$ G) in the interior of the strange quark star. Using the LORENE library, we calculate the structural parameters of SQS for different setups of magnetic field strengths and rotational frequencies. In each setup, we perform calculations for $51$ stellar configurations, with specified central enthalpy values. We investigate the configurations with the maximum gravitational mass of SQS in each setup. Our models of SQSs are compared in the maximum gravitational mass, binding energy, compactness, and deformation of the star. We show that the gravitational mass might exceed $2.3 M_\odot$ in some models, which is comparable with the mass of the recently detected “black widow” pulsar \emph{PSR J0952-0607} and the mass of \emph{GW190814} detected by the LIGO/Virgo collaboration. The deformation and maximum gravitational mass of SQS can be characterized by simple functions that have been fitted to account for variations in both magnetic field strength and frequency. Rapidly rotating strange stars have a minimum gravitational mass given by the equatorial mass-shedding limit.

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F. Kayanikhoo, M. Kapusta and M. Čemeljić
Mon, 8 May 23
35/63

Comments: 18 pages, 10 Figures, 2 tables, submitted to PhysRevD

The Early Light Curve of SN 2023bee: Constraining Type Ia Supernova Progenitors the Apian Way [HEAP]

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http://arxiv.org/abs/2305.03071


We present very early photometric and spectroscopic observations of the Type Ia supernova (SN) 2023bee, starting about 8 hours after the explosion, which reveal a strong excess in the optical and nearest UV (U and UVW1) bands during the first several days of explosion. This data set allows us to probe the nature of the binary companion of the exploding white dwarf and the conditions leading to its ignition. We find a good match to the Kasen model in which a main-sequence companion star stings the ejecta with a shock as they buzz past. Models of double detonations, shells of radioactive nickel near the surface, interaction with circumstellar material, and pulsational-delayed detonations do not provide good matches to our light curves. We also observe signatures of unburned material, in the form of carbon absorption, in our earliest spectra. Our radio non-detections place a limit on the mass-loss rate from the putative companion that rules out a red giant but allows a main-sequence star. We discuss our results in the context of other similar Type Ia SNe in the literature.

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G. Hosseinzadeh, D. Sand, S. Sarbadhicary, et. al.
Mon, 8 May 23
37/63

Comments: submitted to ApJL

Spectrogram correlated stacking: A novel time-frequency domain analysis of the Stochastic Gravitational Wave Background [CL]

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http://arxiv.org/abs/2305.03090


The astrophysical stochastic gravitational wave background (SGWB) originates from numerous faint sub-threshold gravitational wave (GW) signals arising from the coalescing binary compact objects. This background is expected to be discovered from the current (or next-generation) network of GW detectors by cross-correlating the signal between multiple pairs of GW detectors. However, detecting this signal is challenging and the correlation is only detectable at low frequencies due to the arrival time delay between different detectors. In this work, we propose a novel technique, \texttt{Spectrogram Correlated Stacking} (or \texttt{SpeCs}), which goes beyond the usual cross-correlation (and to higher frequencies) by exploiting the higher-order statistics in the time-frequency domain which accounts for the \textit{chirping} nature of the individual events that comprise SGWB. We show that \texttt{SpeCs} improves the signal-to-noise for the detection of SGWB by a factor close to $8$, compared to standard optimal cross-correlation methods which are tuned to measure only the power spectrum of the SGWB signal.\texttt{SpeCs} can probe beyond the power spectrum and its application to the GW data available from the current and next-generation GW detectors would speed up the SGWB discovery.

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R. Dey, L. Micchi, S. Mukherjee, et. al.
Mon, 8 May 23
44/63

Comments: N/A

A Chandra X-ray Study of Supernova Remnant N63A in the Large Magellanic Cloud [HEAP]

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http://arxiv.org/abs/2305.03084


We perform extensive spectroscopy of the supernova remnant N63A in the Large Magellanic Cloud, using $\sim 43$ ks {\it Chandra} archival data. By analysing the spectra of the entire remnant, we determine the abundance distributions for O, Ne, Mg, Si, and Fe. We detect evidence of enhanced O and possibly Ne and Mg in some of the central regions which might indicate an asymmetric distribution of the ejecta. The average O/Ne, O/Mg, and Ne/Mg abundance ratios of the ejecta are in plausible agreement with the nucleosynthesis products from the explosion of a $\sim40$ $M_{\odot}$ progenitor. We estimate an upper limit on the Sedov age of $\sim 5,400\pm200$ yr and explosion energy of $\sim 8.9\pm 1.6\times 10^{51}$ erg for N63A. We discuss the implications of our results for the morphological structure of the remnant, its circumstellar medium and the nature of the progenitor star.

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E. Karagoz, N. Alan, S. Bilir, et. al.
Mon, 8 May 23
46/63

Comments: 22 pages, including 9 figures and 4 tables, accepted for publication in Monthly Notices of the Royal Astronomical Society. arXiv admin note: substantial text overlap with arXiv:2201.09891

Present and future constraints on flavor-dependent long-range interactions of high-energy astrophysical neutrinos [CL]

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http://arxiv.org/abs/2305.03675


The discovery of new, flavor-dependent neutrino interactions would provide compelling evidence of physics beyond the Standard Model. We focus on interactions generated by the anomaly-free, gauged, abelian lepton-number symmetries, specifically $L_e-L_\mu$, $L_e-L_\tau$, and $L_\mu-L_\tau$, that introduce a new matter potential sourced by electrons and neutrons, potentially impacting neutrino flavor oscillations. We revisit, revamp, and improve the constraints on these interactions that can be placed via the flavor composition of the diffuse flux of high-energy astrophysical neutrinos, with TeV-PeV energies, i.e., the proportion of $\nu_e$, $\nu_\mu$, and $\nu_\tau$ in the flux. Because we consider mediators of these new interactions to be ultra-light, lighter than $10^{-10}$ eV, the interaction range is ultra-long, from km to Gpc, allowing vast numbers of electrons and neutrons in celestial bodies and the cosmological matter distribution to contribute to this new potential. We leverage the present-day and future sensitivity of high-energy neutrino telescopes and of oscillation experiments to estimate the constraints that could be placed on the coupling strength of these interactions. We find that, already today, the IceCube neutrino telescope demonstrates potential to constrain flavor-dependent long-range interactions significantly better than existing constraints, motivating further analysis. We also estimate the improvement in the sensitivity due to the next-generation neutrino telescopes such as IceCube-Gen2, Baikal-GVD, KM3NeT, P-ONE, and TAMBO.

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S. Agarwalla, M. Bustamante, S. Das, et. al.
Mon, 8 May 23
49/63

Comments: 46 pages, 17 figures, 2 tables, 6 appendices. Comments are welcome

Peering into the central region of a nano-quasar: XMM-Newton and Chandra views of the CH Cyg Symbiotic System [HEAP]

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http://arxiv.org/abs/2305.03679


We present the analysis of archival XMM-Newton and Chandra observations of CH Cyg, one of the most studied symbiotic stars (SySts). The combination of the high-resolution XMM-Newton RGS and Chandra HETG X-ray spectra allowed us to obtain reliable estimates of the chemical abundances and to corroborate the presence of multi-temperature X-ray-emitting gas. Spectral fitting of the medium-resolution XMM-Newton MOS (MOS1+MOS2) spectrum required the use of an additional component not seen in previous studies in order to fit the 2.0-4.0 keV energy range. Detailed spectral modelling of the XMM-Newton MOS data suggests the presence of a reflection component, very similar to that found in active galactic nuclei. The reflection component is very likely produced by an ionised disk (the accretion disk around the white dwarf) and naturally explains the presence of the fluorescent Fe emission line at 6.4 keV while also contributing to the soft and medium energy ranges. The variability of the global X-ray properties of CH Cyg are discussed as well as the variation of the three Fe lines around the 6-7 keV energy range. We conclude that reflection components are needed to model the hard X-ray emission and may be present in most $\beta/\delta$-type SySt.

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J. Toalá, O. González-Martín, M. Karovska, et. al.
Mon, 8 May 23
50/63

Comments: 12 pages, 7 figures, 5 tables; To appear in MNRAS

Detecting ALP wiggles at TeV energies [CL]

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http://arxiv.org/abs/2305.03604


Axions and axion-like-particles (ALPs) are characterised by their two-photon coupling, which entails so-called photon-ALP oscillations as photons propagate through a magnetic field. These oscillations lead to distinctive signatures in the energy spectrum of high-energy photons from astrophysical sources, allowing one to probe the existence of ALPs. In particular, photon-ALP oscillations will induce energy dependent oscillatory features, or “ALP wiggles”, in the photon spectra. We propose to use the discrete power spectrum to search for ALP wiggles and present a model-independent statistical test. By using PKS 2155-304 as an example, we show that the method has the potential to significantly improve the experimental sensitivities for ALP wiggles. Moreover, we discuss how these sensitivities depend on the modelling of the magnetic field. We find that the use of realistic magnetic field models, due to their larger cosmic variance, substantially enhances detection prospects compared to the use of simplified models.

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M. Kachelriess and J. Tjemsland
Mon, 8 May 23
52/63

Comments: 21 pages, 9 figures

X-ray Studies of Blazar 1ES 1959+650 Using SWIFT & XMM-NEWTON Satellite [HEAP]

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http://arxiv.org/abs/2305.03246


High synchrotron energy peaked blazar 1ES 1959+650 is studied with Swift and XMM-Newton satellite in total 127 observations during the period June 2018-December 2020. We extensively studied its flux and spectral variability on intra-day and long-term timescales. Discrete correlation function analysis between soft and hard X-ray bands indicates soft as well as hard lags. The results are used to constrain the magnetic field of the emitting region which is found to be 0.64 (0.05) Gauss. On long-term timescales, distribution of fluxes shows lognormality behaviour which could be attributed to minijets-in-a-jet model or might be due to the propagation of relativistic shocks down the jet. The spectral energy distribution around the synchrotron peak is well described by the log parabola model. Spectral parameters like peak energy E${p}$, curvature $\beta$ and the peak luminosity L${p}$ are derived from spectral analysis. Their correlations are studied to constrain the acceleration processes of the emitting particles. E${p}$ shows strong correlation with L${p}$ during the high state of the source which indicates spectral changes might be caused by the variations of the average electron energy. Low values of curvature parameter $\beta$ and a weak correlation between E$_{p}$ and ${\beta}$ indicates co-existence of stochastic/statistical acceleration of electrons in the emitting region. Implications of other results are also discussed.

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K. Wani, H. Gaur and M. Patil
Mon, 8 May 23
53/63

Comments: 14 pages, 6 figures, Accepted for publication in ApJ

Nonparametric model for the equations of state of neutron star from deep neural network [CL]

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http://arxiv.org/abs/2305.03323


It is of great interest to understand the equation of state (EOS) of the neutron star (NS), whose core includes highly dense matter. However, there are large uncertainties in the theoretical predictions for the EOS of NS. It is useful to develop a new framework, which is flexible enough to consider the systematic error in theoretical predictions and to use them as a best guess at the same time. We employ a deep neural network to perform a non-parametric fit of the EOS of NS using currently available data. In this framework, the Gaussian process is applied to represent the EOSs and the training set data required to close physical solutions. Our model is constructed under the assumption that the true EOS of NS is a perturbation of the relativistic mean-field model prediction. We fit the EOSs of NS using two different example datasets, which can satisfy the latest constraints from the massive neutron stars, NICER, and the gravitational wave of the binary neutron stars. Given our assumptions, we find that a maximum neutron star mass is $2.38^{+0.15}{-0.13} M\odot$ or $2.41^{+0.15}{-0.14}$ at $95\%$ confidence level from two different example datasets. It implies that the $1.4 M\odot$ radius is $12.31^{+0.29}{-0.31}$ km or $12.30^{+0.35}{-0.37}$ km. These results are consistent with results from previous studies using similar priors. It has demonstrated the recovery of the EOS of NS using a nonparametric model.

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W. Zhou, J. Hu, Y. Zhang, et. al.
Mon, 8 May 23
54/63

Comments: 12 pages, 9 figures, 2 tables, accepted by Astrophysical Journal

High-Energy Radiation and Ion Acceleration in Three-dimensional Relativistic Magnetic Reconnection with Strong Synchrotron Cooling [HEAP]

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http://arxiv.org/abs/2305.02348


We present the results of 3D particle-in-cell (PIC) simulations that explore relativistic magnetic reconnection in pair plasma with strong synchrotron cooling and a small mass fraction of non-radiating ions. Our results demonstrate that the structure of the current sheet is highly sensitive to the dynamic efficiency of radiative cooling. Specifically, stronger cooling leads to more significant compression of the plasma and magnetic field within the plasmoids. We demonstrate that ions can be efficiently accelerated to energies exceeding the plasma magnetization parameter, $\gg\sigma$, and form a hard power-law energy distribution, $f_i\propto \gamma^{-1}$. This conclusion implies a highly efficient proton acceleration in the magnetospheres of young pulsars. Conversely, the energies of pairs are limited to either $\sigma$ in the strong cooling regime or the radiation burnoff limit, $\gamma_{\rm syn}$, when cooling is weak. We find that the high-energy radiation from pairs above the synchrotron burnoff limit, $\varepsilon_c \approx 16$ MeV, is only efficiently produced in the strong cooling regime, $\gamma_{\rm syn} < \sigma$. In this regime, we find that the spectral cutoff scales as $\varepsilon_{\rm cut}\approx \varepsilon_c (\sigma/\gamma_{\rm syn})$, and the highest energy photons are beamed along the direction of the upstream magnetic field, consistent with the phenomenological models of gamma-ray emission from young pulsars. Furthermore, our results place constraints on the reconnection-driven models of gamma-ray flares in the Crab Nebula.

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A. Chernoglazov, H. Hakobyan and A. Philippov
Fri, 5 May 23
7/67

Comments: 24 pages, 18 figures, 1 table; Submitted to ApJ

Over-massive Central Black Holes in the Cosmological Simulations ASTRID and Illustris TNG50 [GA]

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http://arxiv.org/abs/2305.02335


Recent dynamical measurements indicate the presence of a central SMBH with mass $\sim 3\times 10^6 \, \rm M_\odot$ in the dwarf galaxy Leo I, placing the system $\sim50$ times above the standard, local $M_{BH} – M_\star$ relation. While a few over-massive central SMBHs are reported in nearby isolated galaxies, this is the first detected in a Milky Way satellite. We used the ASTRID and Illustris TNG50 LCDM cosmological simulations to investigate the assembly history of galaxies hosting over-massive SMBHs. We estimate that, at the stellar mass of Leo I, $\sim15\%$ of galaxies above the $M_{BH} – M_\star$ relation lie $>10$ times above it. Leo I-like systems are rare but exist in LCDM simulations: they occur in $\sim0.005\%$ of all over-massive systems. Examining the properties of simulated galaxies harboring over-massive central SMBHs, we find that: (i) stars assemble more slowly in galaxies above the $M_{BH} – M_\star$ relation; (ii) the gas fraction in these galaxies experiences a significantly steeper decline over time; and (iii) $>95\%$ of satellite host galaxies in over-dense regions are located above the $M_{BH} – M_\star$ relation. This suggests that massive satellite infall and consequent tidal stripping in a group/dense environment can drive systems away from the $M_{BH} – M_\star$ relation, causing them to become over-massive. As the merging histories of over-massive and under-massive systems do not differ, we conclude that additional environmental effects, such as being in overdense regions, must play a crucial role. In the high-$z$ Universe, central over-massive SMBHs are a signature of heavy black hole seeds; we demonstrate, in contrast, that low-$z$ over-massive systems result from complex environmental interactions.

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E. Weller, F. Pacucci, P. Natarajan, et. al.
Fri, 5 May 23
12/67

Comments: Accepted for publication in MNRAS. 9 pages, 8 figures

VERITAS discovery of very high energy gamma-ray emission from S3 1227+25 and multiwavelength observations [HEAP]

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http://arxiv.org/abs/2305.02860


We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on May 15, 2015 with the Fermi-Large Area Telescope (LAT). A combined five-hour VERITAS exposure on May 16th and May 18th resulted in a strong 13$\sigma$ detection with a differential photon spectral index, $\Gamma$ = 3.8 $\pm$ 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target of opportunity observations with Swift, optical photometry, polarimetry and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of $\tau_{obs}$ = 6.2 $\pm$ 0.9 hours, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cut-off. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.

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A. Acharyya, C. Adams, A. Archer, et. al.
Fri, 5 May 23
14/67

Comments: 18 pages, 6 figures. Accepted for publication in the Astrophysical Journal (ApJ)

Disk-wind-driven Expanding Radio-emitting Shell in Tidal Disruption Events [HEAP]

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http://arxiv.org/abs/2305.02619


We study the evolution of a non-relativistically expanding thin shell in radio-emitting tidal disruption events (TDEs) based on a one-dimensional spherically symmetric model considering the effect of both a time-dependent mass loss rate of the disk wind and the ambient mass distribution. The analytical solutions are derived in two extreme limits: one is the approximate solution near the origin in the form of the Taylor series, and the other is the asymptotic solution in which the ambient matter is dominant far away from the origin. Our numerical solutions are confirmed to agree with the respective analytical solutions. We find that no simple power-law of time solution exists in early to middle times because the mass loss rate varies over time, affecting the shell dynamics. We also discuss the application of our model to the observed radio-emitting TDE, AT2019dsg.

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K. Hayasaki and R. Yamazaki
Fri, 5 May 23
21/67

Comments: 26 pages, 6 figures

Galactic cosmic ray transport in the absence of resonant scattering [HEAP]

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http://arxiv.org/abs/2305.02890


Galactic cosmic ray transport relies on the existence of turbulence on scales comparable with the gyration radius of the particles and with wavenumber vector oriented along the local magnetic field. In the standard picture, in which turbulence is injected at large scales and cascades down to smaller scales, it is all but guaranteed that turbulence on the relevant scales may be present, either because of anisotropic cascading or because of the onset of damping processes. This raises questions on the nature of cosmic-ray scattering, especially at energies $\gtrsim 1$ TeV, where self-generation is hardly relevant. Here, by means of numerical simulations of charged test-particles in a prescribed magnetic field, we investigate particle diffusion in a situation in which turbulence is mainly present at large scales, with the possible presence of a smaller power on small scales, and discuss possible implications of this setup for cosmic-ray transport phenomenology.

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O. Pezzi and P. Blasi
Fri, 5 May 23
23/67

Comments: 5 pages, submitted to MNRAS Letters

Cool Cores in Clusters of Galaxies in the Dark Energy Survey [CEA]

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http://arxiv.org/abs/2305.02365


We search for the presence of cool cores in optically-selected galaxy clusters from the Dark Energy Survey (DES) and investigate their prevalence as a function of redshift and cluster richness. Clusters were selected from the redMaPPer analysis of three years of DES observations that have archival Chandra X-ray observations, giving a sample of 99 clusters with a redshift range of $0.11 < z < 0.87$ and a richness range of $25 < \lambda < 207$. Using the X-ray data, the core temperature was compared to the outer temperature to identify clusters where the core temperature is a factor of 0.7 or less than the outer temperature. We found a cool core fraction of approximately 20% with no significant trend in the cool core fraction with either redshift or richness.

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K. Graham, J. O’Donnell, M. Silverstein, et. al.
Fri, 5 May 23
26/67

Comments: shortened version accepted to RNAAS

HYPerluminous quasars at the Epoch of ReionizatION (HYPERION). A new regime for the X-ray nuclear properties of the first quasars [GA]

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http://arxiv.org/abs/2305.02347


The existence of luminous quasars (QSO) at the Epoch of Reionization (EoR; i.e. z>6) powered by supermassive black holes (SMBH) with masses $\gtrsim10^9~M_\odot$ challenges models of early SMBH formation. To shed light on the nature of these sources we started a multiwavelength programme based on a sample of 18 HYPerluminous quasars at the Epoch of ReionizatION (HYPERION). These are the luminous QSOs whose SMBH must have had the most rapid mass growth during the Universe first Gyr. In this paper we present the HYPERION sample and report on the first of the 3 years planned observations of the 2.4 Ms XMM-Newton Multi-Year Heritage programme on which HYPERION is based. The goal of this programme is to accurately characterise the X-ray nuclear properties of QSOs at the EoR. Through a joint X-ray spectral analysis of 10 sources, covering the rest-frame $\sim2-50$ keV range, we report a steep average photon index ($\Gamma\sim2.4\pm0.1$) which is inconsistent at $\geq4\sigma$ level with the value measured in QSO at z<6. This spectral slope is also significantly steeper than that reported in lower-z QSOs with similar luminosity or accretion rate, thus suggesting a genuine redshift evolution. Alternatively, we can interpret this result as the presence of an unusually low-energy cutoff $E_{cut}\sim20$ keV on a standard $\Gamma=1.9$ power-law. We also report on mild indications that HYPERION QSOs show higher soft X-ray emission at 2 keV compared to the UV one at 2500A than expected by lower-z luminous AGN. We speculate that a redshift-dependent coupling between the X-ray corona and accretion disc or intrinsically different coronal properties may account for the steep spectral slopes, especially in the presence of powerful winds. The reported slopes, if confirmed at lower luminosities, may have an important impact on the design of future X-ray facilities and surveys aimed at the early Universe.

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L. Zappacosta, E. Piconcelli, F. Fiore, et. al.
Fri, 5 May 23
28/67

Comments: 21 pages (including appendix), 12 figures, 4 tables. Submitted to A&A

The impact of effective matter mixing based on three-dimensional hydrodynamical models on the molecule formation in the ejecta of SN 1987A [HEAP]

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http://arxiv.org/abs/2305.02550


To investigate the impact of matter mixing on the formation of molecules in the ejecta of SN 1987A, time-dependent rate equations for chemical reactions are solved for one-zone and one-dimensional ejecta models of SN 1987A. The latter models are based on the one-dimensional profiles obtained by angle-averaging of the three-dimensional hydrodynamical models, which effectively reflect the 3D matter mixing; the impact is demonstrated, for the first time, based on three-dimensional hydrodynamical models. The distributions of initial seed atoms and radioactive $^{56}$Ni influenced by the mixing could affect the formation of molecules. By comparing the calculations for spherical cases and for several specified directions in the bipolar-like explosions in the three-dimensional hydrodynamical models, the impact is discussed. The decay of $^{56}$Ni, practically $^{56}$Co at later phases, could heat the gas and delay the molecule formation. Additionally, Compton electrons produced by the decay could ionize atoms and molecules and could destruct molecules. Several chemical reactions involved with ions such as H$^+$ and He$^+$ could also destruct molecules. The mixing of $^{56}$Ni plays a non-negligible role in both the formation and destruction of molecules through the processes above. The destructive processes of carbon monoxide and silicon monoxide due to the decay of $^{56}$Ni generally reduce the amounts. However, if the molecule formation is sufficiently delayed under a certain condition, the decay of $^{56}$Ni could increase the amounts through a sequence of passes instead compared with the case with lower efficiencies for the destructive processes above.

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M. Ono, T. Nozawa, S. Nagataki, et. al.
Fri, 5 May 23
29/67

Comments: 74 pages, 29 figures, 11 tables; submitted to ApJS

Rotating neutron stars in the first order post-Newtonian approximation [HEAP]

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http://arxiv.org/abs/2305.02413


We study models of uniformly and differentially rotating neutron stars in the framework of post-Newtonian approximation in general relativity as established by Chandrasechar. In particular, we adopt the polytropic equation of state in order to derive the appropriate hydrodynamic equations and a rotation law based on the generalized Clement’s model. To compute equilibrium configurations at the mass-shedding limit, i.e. at critical angular velocity (equivalently, Keplerian angular velocity), we develop an iterative numerical method, belonging to the category of the well-known self-consistent field methods'', with two perturbation parameters: therotation parameter” $\bar{\upsilon}$ and the “gravitation or relativity parameter” $\bar{\sigma}$. These two parameters represent the effects of rotation and gravity on the configuration. We investigate the validity and the limits of our method by comparing our results with respective results of other computational methods and public domain codes. As it turns out, our method can derive satisfactory results for general-relativistic polytropic configurations at critical rotation.

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A. Fotopoulos, V. Karageorgopoulos and V. Geroyannis
Fri, 5 May 23
30/67

Comments: 28 pages, 6 Figures, 5 Tables, Submitted April 2023 Astronomy and Computing

Bimodal black-hole mass distribution and chirp masses of binary black-hole mergers [HEAP]

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http://arxiv.org/abs/2305.02380


In binary black-hole mergers from isolated binary-star evolution, both black holes are from progenitor stars that have lost their hydrogen-rich envelopes by binary mass transfer. Envelope stripping is known to affect the pre-supernova core structures of such binary-stripped stars and thereby their final fates and compact remnant masses. In this paper, we show that binary-stripped stars give rise to a bimodal black-hole mass spectrum with characteristic black-hole masses of about $9\,\mathrm{M}\odot$ and $16\,\mathrm{M}\odot$ across a large range of metallicities. The bimodality is linked to carbon and neon burning becoming neutrino-dominated, which results in interior structures that are difficult to explode and likely lead to black hole formation. The characteristic black-hole masses from binary-stripped stars have corresponding features in the chirp-mass distribution of binary black-hole mergers: peaks at about $8$ and $14\,\mathrm{M}\odot$, and a dearth in between these masses. Current gravitational-wave observations of binary black-hole mergers show evidence for a gap at $10\text{–}12\,\mathrm{M}\odot$ and peaks at $8$ and $14\,\mathrm{M}_\odot$ in the chirp-mass distribution. These features are in agreement with our models of binary-stripped stars. In the future, they may be used to constrain the physics of late stellar evolution and supernova explosions, and may even help measure the cosmological expansion of the Universe.

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F. Schneider, P. Podsiadlowski and E. Laplace
Fri, 5 May 23
32/67

Comments: 20 pages (including appendix with tabulated data; main text: 8 pages), 6 figures; submitted to AAS journals

Comparison of Burst Properties between FRB 20190520B and FRB 20121102A [HEAP]

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http://arxiv.org/abs/2305.02595


A comparative analysis of the individual bursts between FRB 20190520B and FRB 20121102A is presented by compiling a sample of bursts in multiple wavelengths. It is found that the peak frequency ($\nu_p$) distribution of the bursts of FRB 20190520B illustrates four discrete peaks in $\sim1-6$ GHz and their spectral width distribution can be fitted with a log-normal function peaking at 0.35 GHz. The discrete $\nu_p$ distribution and the narrow-banded spectral feature are analogous to FRB 20121102A. The burst duration of FRB 20190520B in the rest frame averages 10.72 ms, longer than that of FRB 20121102A by a factor 3. The specific energy ($E_{\rm \mu_{\rm c}}$) at 1.25 GHz of FRB 20190520B observed with the FAST telescope narrowly ranges in $[0.4, 1]\times 10^{38}$ erg, different from the bimodal $E_{\rm \mu_{\rm c}}$ distribution of FRB 20121102A. Assuming a Gaussian spectral profile of the bursts, our Monte Carlo simulation analysis suggests that a power-law (PL) or a cutoff power-law (CPL) energy function can comparably reproduce the $E_{\rm \mu_{\rm c}}$ distribution of FRB 20190520B. The derived energy function index of the PL model is $4.46\pm 0.17$, much steeper than that of FRB 20121102A ($1.82^{+0.10}_{-0.30}$). For the CPL model, we obtain an index of $0.47$ and a cutoff energy of $7.4\times 10^{37}$ erg. Regarding the predicted $\nu_p$ distribution in 1-2 GHz, the CPL model is more preferred than the PL model. These results indicate that FRB 20190520B and FRB 20121102A shares similar spectral properties, but their energy functions are intrinsically different.

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F. Lyu and E. Liang
Fri, 5 May 23
37/67

Comments: 2023,MNRAS in press, 12 pages, 7 figures

Confining Burst Energy Function and Spectral Fringe Pattern of FRB 20121102A with Multifrequency Observations [HEAP]

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http://arxiv.org/abs/2305.02598


The observed spectral shapes variation and tentative bimodal burst energy distribution (E-distribution) of fast radio burst (FRB) 20121102A with the FAST telescope are great puzzles. Adopting the published multifrequency data observed with the FAST and Arecibo telescopes at $L$ band and the GBT telescope at $C$ band, we investigate these puzzles through Monte Carlo simulations. The intrinsic energy function (E-function) is modeled as $dp/dE\propto E^{-\alpha_{\rm E}}$, and the spectral profile is described as a Gaussian function. A fringe pattern of its spectral peak frequency ($\nu_{\rm p}$) in 0.5-8 GHz is inferred from the $\nu_{\rm p}$ distribution of the GBT sample. We estimate the likelihood of $\alpha_{\rm E}$ and the standard deviation of the spectral profile ($\sigma_{\rm s}$) by utilizing the Kolmogorov–Smirnov (K-S) test probability for the observed and simulated specific E-distributions. Our simulations yields $\alpha_{\rm E}=1.82^{+0.10}{-0.30}$ and $\sigma{\rm s}=0.18^{+0.28}{-0.06}$ ($3\sigma$ confidence level) with the FAST sample. These results suggest that a single power-law function is adequate to model the E-function of FRB 20121102A. The variations of its observed spectral indices and E-distributions with telescopes in different frequency ranges are due to both physical and observational reasons, i.e. narrow spectral width for a single burst and discrete $\nu{p}$ fringe pattern in a broad frequency range among bursts, and the selection effects of the telescope bandpass and sensitivity. The putative $\nu_{p}$ fringe pattern cannot be explained with the current radiation physics models of FRBs. Some caveats of possible artificial effects that may introduce such a feature are discussed.

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F. Lyu, J. Cheng, E. Liang, et. al.
Fri, 5 May 23
40/67

Comments: Published in ApJ,13 pages, 5 figures

Synchrotron intensity plots from a relativistic stratified jet [HEAP]

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http://arxiv.org/abs/2305.02929


We examine the effect of a jet transversal structure from magnetohydrodynamic semi-analytical modelling on the total intensity profiles of relativistic jets from active galactic nuclei. In order to determine the conditions for forming double- and triple-peaked transverse intensity profiles, we calculate the radiative transfer for synchrotron emission with self-absorption from the jets described by the models with a constant angular velocity and with a total electric current closed inside a jet. We show that double-peaked profiles appear either in the models with high maximal Lorentz factors or in optically thick conditions. We show that triple-peaked profiles in radio galaxies constrain the fraction of the emitting particles in a jet. We introduce the possible conditions for triple-peaked profiles under the assumptions that nonthermal electrons are preferably located at the jet edges or are distributed according to Ohmic heating.

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V. Frolova, E. Nokhrina and I. Pashchenko
Fri, 5 May 23
44/67

Comments: 22 pages, 11 figures, accepted by MNRAS

The FLUKA cross sections for cosmic-ray leptons and uncertainties on current positron predictions [HEAP]

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http://arxiv.org/abs/2305.02958


Cosmic-ray (CR) antiparticles have the potential to reveal signatures of unexpected astrophysical processes and even new physics beyond the Standard Model. Recent CR detectors have provided accurate measurements of the positron flux, revealing the so-called positron excess at high energies. However, the uncertainties related to the modelling of the local positron flux are still very high, significantly affecting our models of positron emission from pulsars and current dark matter searches.
In this work, we report a new set of cross sections for positron and electron production derived from the {\tt FLUKA} code. We compare them with the most extended cross-section data-sets and show the impact of neglecting the positron production from heavy CRs. Then, we review the most significant sources of uncertainties in our current estimations of the secondary positron flux at Earth and examine for the first time the impact of considering the spiral arm structure of the Galaxy in these estimations. Finally, we provide state-of-the-art predictions of the local positron flux and discuss the limitations of our dark matter searches with positrons and difficulties to determine the contribution from pulsars to the positron flux at low energies.

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P. Luque, M. Mazziotta and F. Loparco
Fri, 5 May 23
48/67

Comments: 30 pages, 15 figures and no tables

On the problems of detecting Fast Radio Bursts with the LPA LPI [HEAP]

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http://arxiv.org/abs/2305.02778


The paper presents the verification of previously published fast radio bursts (FRB) from the work of V.A. Fedorova and A.E. Rodin, detected in the monitoring data of the Large Phased Array (LPA) radio telescope using a search algorithm based on the convolution of data with a scattered pulse pattern. The same 6-channel data (channel width 415 kHz) were used for verification, in which FRBs were detected with dispersion measures of 247, 570 and 1767 pc/cm3. Additional verification of the published FRB was also carried out in 32-channel data (channel width 78 kHz). We have not been able to confirm any published FRB on the signal-to-noise ratios stated in the original paper. The main errors are caused by incorrect identification of the baseline and incorrect estimation of the standard deviations of noise.

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E. Brylyakova and S. Tyul’bashev
Fri, 5 May 23
51/67

Comments: published in Astronomy Reports, translated by Yandex translator with correction of scientific lexis, 7 pages, 3 figures, 1 table

Disk-corona modeling for spectral index and luminosity correlation of tidal disruption events [HEAP]

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http://arxiv.org/abs/2305.02639


We present a relativistic disk-corona model for a steady state advective accretion disk to explain the UV to X-ray spectral index $\alpha_{\text{OX}}$ evolution of \textbf{four} tidal disruption event (TDE) sources XMMSL2J1446, XMMSL1J1404, XMMSL1J0740, \textbf{and AT2018fyk}. The viscous stress in our model depends on gas ($P_g$) and total ($P_t$) pressures as $\tau_{r\phi} \propto P_g^{\mu} P_t^{1-\mu}$, where $\mu$ is a constant. We compare various steady and time-dependent sub-Eddington TDE accretion models along with our disk-corona model to the observed $\alpha_{\text{OX}}$ of TDE sources and find that the disk-corona model agrees with the observations better than the other models. We find that $\mu$ is much smaller than unity for TDE sources XMMSL2J1446, XMMSL1J1404, and XMMSL1J0740. We also compare the relativistic model with a non-relativistic disk-corona model. The relativistic accretion dynamics reduce the spectral index relative to the non-relativistic accretion by increasing the energy transport to the corona. We estimate the mass accretion rate for all the sources and find that the observed luminosity follows a nearly linear relation with the mass accretion rate. The ratio of X-ray luminosity from the disk to the corona increases with the mass accretion rate. The observed $\alpha_{\text{OX}}$ shows positive and negative correlations with luminosity. The disk-corona model explains the negative correlation seen in the TDE sources XMMSL1J0740, XMMSL2J1446, and XMMSL1J1404. However, TDE AT2018fyk shows a positive correlation at higher luminosity and shows a better fit when a simple spherical adiabatic outflow model is added to the relativistic disk-corona model. Even though the disk luminosity dominates at a higher mass accretion rate, we show that the accretion models without a corona are unable to explain the observations, and the presence of a corona is essential.

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T. Mageshwaran and S. Bhattacharyya
Fri, 5 May 23
59/67

Comments: 23 pages, 18 figures, 4 tables, accepted for publication in Physical Review D

SN 2022acko: the First Early Far-Ultraviolet Spectra of a Type IIP Supernova [HEAP]

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http://arxiv.org/abs/2305.01654


We present five far- and near-ultraviolet spectra of the Type II plateau supernova, SN 2022acko, obtained 5, 6, 7, 19, and 21 days after explosion, all observed with the Hubble Space Telescope/Space Telescope Imaging Spectrograph. The first three epochs are earlier than any Type II plateau supernova has been observed in the far-ultraviolet revealing unprecedented characteristics. These three spectra are dominated by strong lines, primarily from metals, which contrasts with the relatively featureless early optical spectra. The flux decreases over the initial time series as the ejecta cools and line-blanketing takes effect. We model this unique dataset with the non-local thermodynamic equilibrium radiation transport code CMFGEN, finding a good match to the explosion of a low mass red supergiant with energy Ekin = 6 x 10^50 erg. With these models we identify, for the first time, the ions that dominate the early UV spectra. We also present optical photometry and spectroscopy, showing that SN 2022acko has a peak absolute magnitude of V = -15.4 mag and plateau length of ~115d. The spectra closely resemble those of SN 2005cs and SN 2012A. Using the combined optical and UV spectra, we report the fraction of flux redwards of the uvw2, U, B, and V filters on days 5, 7, and 19. We also create a spectral time-series of Type II supernovae in the ultraviolet, demonstrating the rapid decline of UV flux over the first few weeks of evolution. Future observations of Type II supernovae will continue to explore the diversity seen in the limited set of high-quality UV spectra.

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K. Bostroem, L. Dessart, D. Hillier, et. al.
Thu, 4 May 23
2/60

Comments: Submitted to ApJL

Application of the disk instability model to all Quasi-Periodic Eruptions [HEAP]

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http://arxiv.org/abs/2305.02071


After the first quasi-periodic eruptions (QPEs, GSN069) was reported in 2019, four other sources have been identified as QPEs or its candidate. However, the physics behind QPEs is still unclear so far, though several models have been proposed. Pan et al. (2022) proposed an instability model for the accretion disk with magnetically driven outflows in the first QPEs GSN 069, which is able to reproduce both the light curve and the evolution of spectrum fairly well. In this work, we exploit this model to all the QPEs. We imporve the calculations of the spectrum of disk by introducing a hardening factor, which is caused by the deviation of opacity from the blackbody. We find that the light curves and evolution of the spectra of the four QPEs or candidate can all be well reproduced by our model calculations.

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X. Pan, S. Li and X. Cao
Thu, 4 May 23
5/60

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

A new sample of transient ultraluminous X-ray sources serendipitously discovered by Swift/XRT [HEAP]

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http://arxiv.org/abs/2305.01693


Ultraluminous X-ray sources (ULXs) are our best laboratories for studying extreme super-Eddington accretion. Most studies of these objects are of relatively persistent sources, however there is growing evidence to suggest a large fraction of these sources are transient. Here we present a sample of five newly reported transient ULXs in the galaxies NGC 4945, NGC 7793 and M81 serendipitously discovered in Swift/XRT observations. Swift monitoring of these sources have provided well sampled lightcurves, allowing for us to model the lightcurves with the disk instability model of Hameury & Lasota (2020) which implies durations of 60-400 days and that the mass accretion rate through the disk is close to or greater than the Eddington rate. Of the three source regions with prior HST imaging, color magnitude diagrams of the potential stellar counterparts show varying ages of the possible stellar counterparts. Our estimation of the rates of these sources in these three galaxies is 0.4-1.3 year$^{-1}$. We find that while persistent ULXs dominate the high end of galaxy luminosity functions, the number of systems that produce ULX luminosities are likely dominated by transient sources.

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M. Brightman, J. Hameury, J. Lasota, et. al.
Thu, 4 May 23
10/60

Comments: Accepted for publication in ApJ

AT 2021loi: A Bowen Fluorescence Flare with a Rebrightening Episode, Occurring in a Previously-Known AGN [GA]

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http://arxiv.org/abs/2305.01694


AT 2021loi is an optical-ultraviolet transient located at the center of its host galaxy. Its spectral features identify it as a member of the “Bowen Fluorescence Flare” (BFF) class. The first member of this class was considered to be related to a tidal disruption event, but enhanced accretion onto an already active supermassive black hole was suggested as an alternative explanation. AT 2021loi, having occurred in a previously-known unobscured AGN, strengthens the latter interpretation. Its light curve is similar to those of previous BFFs, showing a rebrightening approximately one year after the main peak (which was not explicitly identified, but might be the case, in all previous BFFs). An emission feature around 4680 A, seen in the pre-flare spectrum, strengthens by a factor of $\sim$2 around the optical peak of the flare, and is clearly seen as a double peaked feature then, suggesting a blend of NIII $\lambda 4640$ with HeII $\lambda4686$ as its origin. The appearance of OIII $\lambda$3133 and possible NIII $\lambda\lambda4097,4103$ (blended with H$\delta$) during the flare further support a Bowen Fluorescence classification. Here, we present ZTF, ATLAS, Keck, Las Cumbres Observatory, NEOWISE-R, $Swift$, AMI and VLA observations of AT 2021loi, making it one of the best observed BFFs to date. AT 2021loi thus provides some clarity on the nature of BFFs but also further demonstrates the diversity of nuclear transients.

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L. Makrygianni, B. Trakhtenbrot, I. Arcavi, et. al.
Thu, 4 May 23
12/60

Comments: Submitted to ApJ. This version addresses comments from the referee

Asymptotic behavior of null geodesics near future null infinity IV: Null-access theorem for generic asymptotically flat spacetime [CL]

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http://arxiv.org/abs/2305.01767


In our previous papers [arXiv:2106.03150, arXiv:2110.10917, arXiv:2208.00822], we analyzed the asymptotic behavior of future directed null geodesics near future null infinity and then we showed a proposition on the accessibility of the null geodesics to future null infinity in a specific class of asymptotically flat spacetimes. In this paper, we adopt the retarded time of the Bondi coordinate as the parameter for the null geodesics and then see that one can relax the assumptions imposed in our previous studies. As a consequence, we obtain a new null-access theorem for generic asymptotically flat spacetimes.

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M. Amo, K. Izumi, Y. Tomikawa, et. al.
Thu, 4 May 23
17/60

Comments: 16 pages, no figures

The self-confinement of electrons and positrons from dark matter [HEAP]

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http://arxiv.org/abs/2305.01999


Radiative emissions from electrons and positrons generated by dark matter (DM) annihilation or decay are one of the most investigated signals in indirect searches of WIMPs. Ideal targets must have large ratio of DM to baryonic matter. However, such “dark” systems have a poorly known level of magnetic turbulence, which determines the residence time of the electrons and positrons and therefore also the strength of the expected signal. This typically leads to significant uncertainties in the derived DM bounds. In a novel approach, we compute the self-confinement of the DM-induced electrons and positrons. Indeed, they themselves generate irregularities in the magnetic field, thus setting a lower limit on the presence of the magnetic turbulence. We specifically apply this approach to dwarf spheroidal galaxies. Finally, by comparing the expected synchrotron emission with radio data from the direction of the Draco galaxy collected at the Giant Metre Radio Telescope, we show that the proposed approach can be used to set robust and competitive bounds on WIMP DM.

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M. Regis, M. Korsmeier, G. Bernardi, et. al.
Thu, 4 May 23
20/60

Comments: 18 pages, 9 figures

The Spatial Correlation of High Mass X-ray Binaries and Young Star Clusters in Nearby Star-Forming Galaxies [HEAP]

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http://arxiv.org/abs/2305.01802


We present an analysis of the two-point spatial correlation functions of high-mass X-ray binary (HMXB) and young star cluster (YSC) populations in M31 and M33. We find evidence that HMXBs are spatially correlated with YSCs to a higher degree than would be expected from random chance in both galaxies. When supplemented with similar studies in the Milky Way, Small Magellanic Cloud, and NGC 4449, we find that the peak value of the spatial correlation function correlates strongly with the specific star formation rate of the host galaxy. We additionally perform an X-ray stacking analysis of 211 non-X-ray detected YSCs in M31 and 463 YSCs in M33. We do not detect excess X-ray emission at the stacked cluster locations down to 3$\sigma$ upper limits of $\sim10^{33}$ erg s$^{-1}$ (0.35-8 keV) in both galaxies, which strongly suggests that dynamical formation within YSCs is not a major HMXB formation channel. We interpret our results in the context of (1) the recent star formation histories of the galaxies, which may produce differences in the demographics of compact objects powering the HMXBs, and (2) the differences in natal kicks experienced by compact objects during formation, which can eject newly-formed HMXB from their birth clusters.

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B. Binder, A. Anderson, K. Garofali, et. al.
Thu, 4 May 23
22/60

Comments: Accepted to MNRAS; 11 pages, 7 figures

Methods and prospects for gravitational wave searches targeting ultralight vector boson clouds around known black holes [CL]

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http://arxiv.org/abs/2305.00401


Ultralight bosons are predicted in many extensions to the Standard Model and are popular dark matter candidates. The black hole superradiance mechanism allows for these particles to be probed using only their gravitational interaction. In this scenario, an ultralight boson cloud may form spontaneously around a spinning black hole and extract a non-negligible fraction of the black hole’s mass. These oscillating clouds produce quasi-monochromatic, long-duration gravitational waves that may be detectable by ground-based or space-based gravitational wave detectors. We discuss the capability of a new long-duration signal tracking method, based on a hidden Markov model, to detect gravitational wave signals generated by ultralight vector boson clouds, including cases where the signal frequency evolution timescale is much shorter than that of a typical continuous wave signal. We quantify the detection horizon distances for vector boson clouds with current- and next-generation ground-based detectors. We demonstrate that vector clouds hosted by black holes with mass $\gtrsim 60 M_{\odot}$ and spin $\gtrsim 0.6$ are within the reach of current-generation detectors up to a luminosity distance of $\sim 1$ Gpc. This search method enables one to target vector boson clouds around remnant black holes from compact binary mergers detected by gravitational-wave detectors. We discuss the impact of the sky localization of the merger events and demonstrate that a typical remnant black hole reasonably well-localized by the current generation detector network is accessible in a follow-up search.

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D. Jones, L. Sun, N. Siemonsen, et. al.
Thu, 4 May 23
27/60

Comments: 20 pages, 12 figures

Testing the Blazar Sequence with Spectra of Recently Discovered Dim Blazars from the Fermi Unassociated Catalog [HEAP]

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http://arxiv.org/abs/2305.02087


Recent works have developed samples of blazars from among the Fermi-LAT unassociated sources via machine learning comparisons with known blazar samples. Continued analysis of these new blazars tests the predictions of the blazar sequence and enables more flux-complete samples of blazars as a population. Using Fermi, Swift, WISE, and archival radio data, we construct broadband spectral energy distributions for 106 recently identified blazars. Drawn from the unassociated 4FGL source sample, this new sample has a lower median flux than the overall sample of gamma-ray blazars. By measuring the synchrotron peak frequency, we compare our sample of new blazars with known blazars from the 4LAC catalog. We find that the bulk of the new blazars are similar to High-Synchrotron Peak (HSP) BL Lac objects, with a higher median synchrotron peak; the sample has a median $ log( {\nu}{syn} /Hz ) = 15.5 $ via BLaST peak estimation, compared to $ log( {\nu}{syn} /Hz ) = 14.2 $ for the 4LAC BL Lacs. Finally, we conduct synchrotron self-Compton (SSC) leptonic modeling, comparing fitted physical and phenomenological properties to brighter blazars. We find that the new blazars have smaller characteristic Lorentz factors ${\gamma}_{boost}$ and fitted magnetic fields $B$, in agreement with blazar sequence predictions. The new blazars have slightly higher Compton dominance ratios than expected, which may point to alternative emission models for these dim blazars. Our results extend the predictions of the blazar sequence to a sample of dimmer blazars, confirming the broad predictions of that theory.

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S. Kerby and A. Falcone
Thu, 4 May 23
31/60

Comments: 13 pages main body with 10 figures. 8 pages of data tables

Reconnection-driven flares in 3D black hole magnetospheres — A scenario for hot spots around Sagittarius A* [HEAP]

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http://arxiv.org/abs/2305.01689


Low-luminosity supermassive and stellar-mass black holes (BHs) may be embedded in a collisionless and highly magnetized plasma. They show non-thermal flares indicative of efficient dissipative processes in the vicinity of the BH. During NIR flares from the supermassive BH Sagittarius A* (Sgr A), GRAVITY detected circular motion and polarization evolution which suggest the presence of transient synchrotron-emitting hot spots moving around the BH. We study 3D reconnecting current layers in the magnetosphere of spinning BHs to determine whether plasma-loaded flux ropes formed near the event horizon could reproduce the hot spot observations and help constraining the BH spin. We perform global 3D particle-in-cell simulations in Kerr spacetime of a pair plasma embedded in a strong large-scale magnetic field originating in a disk in prograde Keplerian rotation. A cone-shaped current layer develops which surrounds the twisted open magnetic field lines threading the event horizon. Magnetic field lines coupling the disk to the BH inflate and reconnect a few gravitational radii above the disk. Particles accelerate and accumulate in a few rotating macroscopic flux ropes. Once flux ropes detach, they propagate in the current layer following what appears as a rapidly opening spiral when seen face-on. A single flux rope carries enough relativistic particles to emit synchrotron radiation at levels suitable to reproduce the flares’ peak-luminosity of Sgr A but it quickly fades away as it flows away. Our kinematic analysis of flux ropes’ motion favors a BH spin of 0.65 to 0.8 for Sgr A*. The flares’ duration require that the underlying magnetic loop seeded in the disk mid-plane has a finite lifetime and azimuthal extent. In this scenario, the hot spot corresponds to a spinning arc along which multiple reconnection sites power the net emission as flux ropes episodically detach.

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I. Mellah, B. Cerutti and B. Crinquand
Thu, 4 May 23
33/60

Comments: Submitted to A&A, comments welcome

Constraining the dark matter interpretation of the positron excess with $γ$-ray data [HEAP]

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http://arxiv.org/abs/2305.01992


The particle origin of dark matter (DM) is still one of the main puzzles in modern physics. One of the most promising search strategy to detect DM at laboratories is through the indirect search of cosmic particles that are produced from DM annihilation in space. In particular, the flux of cosmic positrons has been measured with high precision by the AMS-02 experiment demonstrating that an excess above 10 GeV, with respect to the secondary production, is present. We study in this paper the possible DM origin of the positron excess finding the values of the DM mass $M$ and annihilation cross section $\langle \sigma v \rangle$ that are needed to fit high-energy positron data. In particular, we find that for DM annihilating into $b\bar{b}$ it is required to have $M=43$ TeV and $\langle \sigma v \rangle = 10^{-21}$ cm$^3$/s while for $\tau^+\tau^-$ $M=2$ TeV and $\langle \sigma v \rangle = 3\times 10^{-23}$ cm$^3$/s. If DM produce positrons, they are expected to generate gamma rays from the center of the Milky Way and around dwarf galaxy satellites of the Galaxy. We thus combine the values for the DM mass and annihilation cross section obtained with the fit to AMS-02 positron data with the upper limits derived with the non-detection of $\gamma$ rays with HESS in the direction of the Galactic center and Fermi-LAT for the combined analysis of dwarf galaxies. The main result of the paper is that only DM annihilating into $\mu^+ \mu^-$ with a mass around 500 GeV and $\langle \sigma v \rangle = 4\times 10^{-24}$ cm$^3$/s can fit AMS-02 data and be compatible with the upper limits found with $\gamma$ rays. As for the $\tau^+ \tau^-$ ($b\bar{b}$) channel, DM can contribute at most at a few tens $\%$ (a few \%) level.

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H. Zhan
Thu, 4 May 23
37/60

Comments: 15 pages, 6 figures, 2 tables. Comments are welcome

Demonstrating repetitive non-destructive readout (RNDR) with SiSeRO devices [IMA]

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http://arxiv.org/abs/2305.01900


We demonstrate so-called repetitive non-destructive readout (RNDR) for the first time on a Single electron Sensitive Readout (SiSeRO) device. SiSeRO is a novel on-chip charge detector output stage for charge-coupled device (CCD) image sensors, developed at MIT Lincoln Laboratory. This technology uses a p-MOSFET transistor with a depleted internal gate beneath the transistor channel. The transistor source-drain current is modulated by the transfer of charge into the internal gate. RNDR was realized by transferring the signal charge non-destructively between the internal gate and the summing well (SW), which is the last serial register. The advantage of the non-destructive charge transfer is that the signal charge for each pixel can be measured at the end of each transfer cycle and by averaging for a large number of measurements ($\mathrm{N_{cycle}}$), the total noise can be reduced by a factor of 1/$\mathrm{\sqrt{N_{cycle}}}$. In our experiments with a prototype SiSeRO device, we implemented nine ($\mathrm{N_{cycle}}$ = 9) RNDR cycles, achieving around 2 electron readout noise (equivalent noise charge or ENC) with spectral resolution close to the fano limit for silicon at 5.9 keV. These first results are extremely encouraging, demonstrating successful implementation of the RNDR technique in SiSeROs. They also lay foundation for future experiments with more optimized test stands (better temperature control, larger number of RNDR cycles, RNDR-optimized SiSeRO devices) which should be capable of achieving sub-electron noise sensitivities. This new device class presents an exciting technology for next generation astronomical X-ray telescopes requiring very low-noise spectroscopic imagers. The sub-electron sensitivity also adds the capability to conduct in-situ absolute calibration, enabling unprecedented characterization of the low energy instrument response.

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T. Chattopadhyay, S. Herrmann, P. Orel, et. al.
Thu, 4 May 23
46/60

Comments: Under review in Journal of Astronomical Telescopes, Instruments, and Systems (JATIS). arXiv admin note: text overlap with arXiv:2208.01082

The dynamics of debris streams from tidal disruption events: exact solutions, critical stream density, and hydrogen recombination [HEAP]

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http://arxiv.org/abs/2305.01677


A star destroyed by a supermassive black hole (SMBH) in a tidal disruption event (TDE) is transformed into a filamentary structure known as a tidally disrupted stellar debris stream. We show that when ideal gas pressure dominates the thermodynamics of the stream, there is an exact solution to the hydrodynamics equations that describes the stream evolution and accounts for self-gravity, pressure, the dynamical expansion of the gas, and the transverse structure of the stream. We analyze the stability of this solution to cylindrically symmetric perturbations, and show that there is a critical stream density below which the stream is unstable and is not self-gravitating; this critical density is a factor of at least 40-50 smaller than the stream density in a TDE. Above this critical density the stream is overstable, self-gravity confines the stream, the oscillation period is exponentially long, and the growth rate of the overstability scales as $t^{1/6}$. The power-law growth and small power-law index of the overstability implies that the stream is effectively stable to cylindrically symmetric perturbations. We also use this solution to analyze the effects of hydrogen recombination, and suggest that even though recombination substantially increases the gas entropy, it is likely incapable of completely destroying the influence of self-gravity. We also show that the transient produced by recombination is far less luminous than previous estimates.

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E. Coughlin
Thu, 4 May 23
52/60

Comments: 17 pages, 15 figures, MNRAS accepted

Detecting High-Frequency Gravitational Waves in Planetary Magnetosphere [CL]

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http://arxiv.org/abs/2305.01832


High-frequency gravitational waves (HFGWs) carry a wealth of information on the early Universe with a tiny comoving Hubble horizon and astronomical objects of small scale but with dense energy. We demonstrate that the nearby planets, such as Earth and Jupiter, can be utilized as a laboratory for detecting the HFGWs. These GWs are then expected to convert to signal photons in the planetary magnetosphere, across the frequency band of astronomical observation. As a proof of concept, we present the first limits from the existing low-Earth-orbit satellite for specific frequency bands and project the sensitivities for the future more-dedicated detections. The first limits from Juno, the latest mission orbiting Jupiter, are also presented. Attributed to the long path of effective GW-photon conversion and the wide angular distribution of signal flux, we find that these limits are highly encouraging, for a broad range of frequencies including a large portion unexplored before.

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T. Liu, J. Ren and C. Zhang
Thu, 4 May 23
57/60

Comments: 11 pages, 8 figures

Impacts of dark matter interaction on nuclear and neutron star matter within the relativistic mean-field model [CL]

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http://arxiv.org/abs/2305.02065


This thesis explores the effects of dark matter (DM) on neutron stars (NSs) using the relativistic mean-field (RMF) model. The effects of DM on NS properties, including the mass-radius relation, the moment of inertia, and tidal deformability, are calculated by varying its fraction. The study found that the EOS becomes softer with increasing DM momentum, and the DM has marginal effects on nuclear matter properties, except for the EOSs and binding energy per particle. The study also calculated the properties of isolated, static, and rotating DM admixed NS and found that the DM has significant effects on both static and rotating NS. We have also observed that a tiny amount of DM can accumulate inside the NS, and more amount of it makes the NS unstable. The study also suggests that the secondary component might be a NS with DM content if the underlying nuclear EOS is sufficiently stiff. The $f$-mode oscillations of the DM admixed hyperon stars are calculated and found that there exist a correlation between canonical $f$-mode frequency and the dimensionless tidal deformability parameter ($\Lambda_{1.4}$) and we have put a constraint on $f$-mode frequency using GW170817 data. Finally, we have calculated the DM admixed binary NS properties and found that the binary system becomes less deformed and sustains more time in its inspiral phases with the addition of DM. Therefore, we suggest that one can take DM inside the compact objects while modeling the inspiral waveforms for the BNS systems.

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H. Das
Thu, 4 May 23
58/60

Comments: PhD Thesis

Test of the Second Postulate of Relativity from Gravitational Wave Observations [CL]

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http://arxiv.org/abs/2304.14820


The second postulate of special relativity states that the speed of light in vacuum is independent of the emitter’s motion. Though this claim has been verified in various experiments and observations involving electromagnetic radiation with very high accuracy, such a test for gravitational radiation still needs to be explored. We analyzed data from the LIGO and Virgo detectors to test this postulate for gravitational radiation within the ambit of \textit{emission models}, where the speed of gravitational waves emitted by a source moving with a velocity $v$ relative to a stationary observer is given by ${c’ = c + k\,v}$, where $k$ is a constant. We have estimated the upper bound on the 90\% credible interval over $k$ that parameterizes the deviation from the second postulate to be ${k \leq 8.3 \times {10}^{-18}}$ which is several orders of magnitude more stringent compared to previous bounds obtained from electromagnetic observations. The Bayes’ factor supports the second postulate, with very strong evidence that the data is consistent with the null hypothesis $k = 0$. This confirms that the speed of gravity is independent of the motion of the emitter, upholding the principle of relativity for gravitational interactions.

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R. Ghosh, S. Nair, L. Pathak, et. al.
Wed, 3 May 23
4/67

Comments: 7 pages, 3 figures

Spatial coincidence between ultra-high energy cosmic rays and TeV gamma rays in the direction of GRB 980425/SN 1998bw [HEAP]

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http://arxiv.org/abs/2305.01500


Gamma-ray bursts (GRBs) have long been suspected as possible ultra-high energy cosmic ray (UHECR) accelerators. In this brief note, I report that GRB 980425/SN 1998bw falls within the region of interest (ROI) with the highest significance in an all-sky blind search for magnetically-induced effects in the arrival directions of UHECRs conducted by the Pierre Auger Collaboration with events detected up to to 2018 August 31. There is also report in the literature of delayed TeV emission in archival Fermi-LAT observations from the direction of GRB 980425/SN 1998bw. The combined probability that two distinct cosmic ray acceleration signatures in two different multimessenger experiments may appear at the same spatial location by chance is estimated to be between $1.62 \times 10^{-3}$ and 0.0157.

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N. Mirabal
Wed, 3 May 23
5/67

Comments: 3 pages, 1 figure, Research Notes of the AAS

An XMM-Newton Study of Six Narrow-Line Seyfert 1 Galaxies at z = 0.35–0.92 [HEAP]

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http://arxiv.org/abs/2305.00991


We report a detailed analysis of the XMM-Newton spectra of six Narrow-Line Seyfert 1 (NLS1) galaxies at redshift z = 0.35–0.92. Compared with the NLS1s at lower redshift in the previously most-studied sample, these NLS1s have larger black hole (BH) masses ($\log\,M_\text{BH}>7.5$) with similar or even lower Eddington ratios. Our extended XMM-Newton sample of NLS1s shows strong soft X-ray excess emission below 2 keV. The quantified soft excess strength does not show an obvious discrepancy from previous studies of the lower-redshift NLS1s. The systematic effect in the measurement of the Eddington ratio mainly lies in the bolometric correction factor. We also tentatively fit the spectra assuming two more physical models for the soft excess: warm Comptonization and relativistic reflection from the inner accretion disk. In the first scenario, we confirm the ubiquity of a warm and optically thick corona. The behavior of a single source can be better explained by relativistic reflection, although we cannot distinguish which model is a more favorable explanation for the soft excess based on the best-fit statistics.

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Z. Yu, J. Jiang, C. Bambi, et. al.
Wed, 3 May 23
10/67

Comments: 13 pages, 10 figures

Quantum information and quantum simulation of neutrino physics [CL]

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http://arxiv.org/abs/2305.01150


In extreme astrophysical environments such as core-collapse supernovae and binary neutron star mergers, neutrinos play a major role in driving various dynamical and microphysical phenomena, such as baryonic matter outflows, the synthesis of heavy elements, and the supernova explosion mechanism itself. The interactions of neutrinos with matter in these environments are flavor-specific, which makes it of paramount importance to understand the flavor evolution of neutrinos. Flavor evolution in these environments can be a highly nontrivial problem thanks to a multitude of collective effects in flavor space, arising due to neutrino-neutrino ($\nu$-$\nu$) interactions in regions with high neutrino densities. A neutrino ensemble undergoing flavor oscillations under the influence of significant $\nu$-$\nu$ interactions is somewhat analogous to a system of coupled spins with long-range interactions among themselves and with an external field (‘long-range’ in momentum-space in the case of neutrinos). As a result, it becomes pertinent to consider whether these interactions can give rise to significant quantum correlations among the interacting neutrinos, and whether these correlations have any consequences for the flavor evolution of the ensemble. In particular, one may seek to utilize concepts and tools from quantum information science and quantum computing to deepen our understanding of these phenomena. In this article, we attempt to summarize recent work in this field. Furthermore, we also present some new results in a three-flavor setting, considering complex initial states.

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A. Balantekin, M. Cervia, A. Patwardhan, et. al.
Wed, 3 May 23
11/67

Comments: 13 pages, 3 figures. Invited review for the Eur. Phys. J. A special issue on “Quantum computing in low-energy nuclear theory”

Gravitational Redshift Detection from the Magnetic White Dwarf Harbored in RX J1712.6-2414 [HEAP]

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http://arxiv.org/abs/2305.01496


Gravitational redshift is a fundamental parameter that allows us to determine the mass-to-radius ratio of compact stellar objects, such as black holes, neutron stars, and white dwarfs (WDs). In the X-ray spectra of the close binary system, RX J1712.6$-$2414, obtained from the Chandra High-Energy Transmission Grating observation, we detected significant redshifts for characteristic X-rays emitted from hydrogen-like magnesium, silicon ($\Delta E/E_{\rm rest} \sim 7 \times 10^{-4}$), and sulfur ($\Delta E/E_{\rm rest} \sim 15 \times 10^{-4}$) ions, which are over the instrumental absolute energy accuracy (${\Delta E/E_{\rm rest} \sim 3.3} \times 10^{-4}$). Considering some possible factors, such as Doppler shifts associated with the plasma flow, systemic velocity, and optical depth, we concluded that the major contributor to the observed redshift is the gravitational redshift of the WD harbored in the binary system, which is the first gravitational redshift detection from a magnetic WD. Moreover, the gravitational redshift provides us with a new method of the WD mass measurement by invoking the plasma-flow theory with strong magnetic fields in close binaries. Regardless of large uncertainty, our new method estimated the WD mass to be $M_{\rm WD}> 0.9\,M_{\odot}$.

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T. Hayashi, H. Mori, K. Mukai, et. al.
Wed, 3 May 23
14/67

Comments: 13 pages, 5 figures. Accepted for publication in ApJ

Analytical and Numerical Analysis of Circumbinary Disk Dynamics – I: Coplanar Systems [SSA]

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http://arxiv.org/abs/2305.01533


We present an analytical and numerical study of a system composed of a stellar binary pair and a massless, locally isothermal viscous accretion disk that is coplanar to the binary orbital plane. Analytically, we study the effect of the binary’s gravitational potential over short timescales through the study of stability for epicyclic orbits, and over long timescales by revisiting the concept of resonant torques. Numerically, we perform two-dimensional Newtonian numerical simulations of the disk-binary system over a range of binary mass ratios. We find that the results of our simulations are consistent with previous numerical studies. We additionally show, by comparison of the analytical and numerical results, that the circumbinary gap is maintained on the orbital timescale through the driving of epicyclic instabilities, and does not depend on resonant torquing, contrary to standard lore. While our results are applicable to any disk-binary system, we highlight the importance of this result in the search for electromagnetic and gravitational-wave signatures from supermassive black-hole binaries.

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S. Mahesh, S. McWilliams and M. Pirog
Wed, 3 May 23
15/67

Comments: N/A

Counter-rotating black holes from FRII lifetimes [GA]

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http://arxiv.org/abs/2305.01042


Estimates suggest that while FRII jets appear to have lifetimes constrained to hundreds of millions of years, radio galaxies with FRI jets appear to be longer lived. We illustrate the nature of this time constraint from model perspectives, showing how compatibility between theory and data match in a way suggesting a key difference between active galaxies whose engines are characterized by accretion onto co-rotating versus counter-rotating black holes. We calculate a range of timescales for counter-rotating black holes for a range of accretion rates compatible with theory which we then compare to data. The validity of these timescales constitutes the most powerful recent piece of evidence for considering counter-rotation between black holes and accretion disks in high energy astrophysics.

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D. Garofalo
Wed, 3 May 23
30/67

Comments: N/A

Constraining the ellipticity and frequency of binary neutron star remnant via its gravitational-wave and electromagnetic radiations [HEAP]

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http://arxiv.org/abs/2305.01364


The nature of the merger remnant of binary neutron star (BNS) remains an open question. From the theoretical point of view, one possible outcome is a supra-massive neutron star (SMNS), which is supported by rigid rotation and through its survival of hundreds of seconds before collapsing into a black hole (BH). If this is the case, the SMNS can emit continuous gravitational waves (GW) and electromagnetic (EM) radiation, particularly in the X-ray band. In this work, the ellipticity and initial frequency of SMNS are constrained with a Bayesian framework using simulated X-ray and GW signals, which could be detected by The Transient High Energy Sky and Early Universe Surveyor (THESEUS) and Einstein Telescope (ET), respectively. We found that only considering the X-ray emission can not completely constrain the initial frequency and ellipticity of the SMNS, but it can reduce the ranges of the parameters. Afterwards, we can use the posterior distribution of the X-ray parameter estimates as a prior for the GW parameter estimates. It was found that the 95$\%$ credible region of the joint X-ray-GW analysis was about $10^5$ times smaller than that of the X-ray analysis alone.

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Y. Yuan, X. Fan and H. Lv
Wed, 3 May 23
32/67

Comments: Accepted by MNRAS

First Constraints on the Photon Coupling of Axion-like Particles from Multimessenger Studies of the Neutron Star Merger GW170817 [CL]

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http://arxiv.org/abs/2305.01002


We use multimessenger observations of the neutron star merger event GW170817 to derive new constraints on axion-like particles (ALPs) coupling to photons. ALPs are produced via Primakoff and photon coalescence processes in the merger, escape the remnant and decay back into two photons, giving rise to a photon signal approximately along the line-of-sight to the merger. We analyze the spectral and temporal information of the ALP-induced photon signal, and use the Fermi-LAT observations of GW170817 to derive our new ALP constraints. We also show the improved prospects with future MeV gamma-ray missions, taking the spectral and temporal coverage of AMEGO-X as an example.

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P. Dev, J. Fortin, S. Harris, et. al.
Wed, 3 May 23
47/67

Comments: 8+8 pages, 4+6 figures

Ameliorating the Courant-Friedrichs-Lewy condition in spherical coordinates: A double FFT filter method for general relativistic MHD in dynamical spacetimes [CL]

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http://arxiv.org/abs/2305.01537


Numerical simulations of merging compact objects and their remnants form the theoretical foundation for gravitational wave and multi-messenger astronomy. While Cartesian-coordinate-based adaptive mesh refinement is commonly used for simulations, spherical-like coordinates are more suitable for nearly spherical remnants and azimuthal flows due to lower numerical dissipation in the evolution of fluid angular momentum, as well as requiring fewer numbers of computational cells. However, the use of spherical coordinates to numerically solve hyperbolic partial differential equations can result in severe Courant-Friedrichs-Lewy (CFL) stability condition timestep limitations, which can make simulations prohibitively expensive. This paper addresses this issue for the numerical solution of coupled spacetime and general relativistic magnetohydrodynamics evolutions by introducing a double FFT filter and implementing it within the fully MPI-parallelized SphericalNR framework in the Einstein Toolkit. We demonstrate the effectiveness and robustness of the filtering algorithm by applying it to a number of challenging code tests, and show that it passes these tests effectively, demonstrating convergence while also increasing the
timestep significantly compared to unfiltered simulations.

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L. Ji, V. Mewes, Y. Zlochower, et. al.
Wed, 3 May 23
55/67

Comments: 15 pages, 13 figures, revtex4-1

Search for pulsars in an area with coordinates 3h < α< 4h and +21o < δ< +42o [HEAP]

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http://arxiv.org/abs/2305.01409


On the Large Phased Array (LPA) of Lebedev Physics Institute (LPI), a search for pulsars outside the Galaxy plane was carried out in a 300 sq. deg area. The search with a sensitivity 5-10 times better than that of previously conducted surveys was at a frequency of 111 MHz. The search was carried out in the summed power spectra. With an accumulation equivalent to 100 hours of continuous observations for each point of the area, 5 known pulsars were detected with a signal-to-noise ratio (S/N) from 20 to 1300 in the first harmonic of the spectrum. Average profiles were obtained for the detected pulsars. Estimates of the peak and integral flux densities of the found pulsars are given for individual sessions and for the power spectra summarized over 5.5 years, obtained using the developed method based on measurements of the height of harmonics in the power spectrum. No new pulsars have been detected in the area. Apparently, when searching for pulsars in the area, we have approached the lower limit of the luminosity of the second pulsars. The completeness of the survey is at the level of 0.5 mJy.

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S. Tyul’bashev and G. Tyul’basheva
Wed, 3 May 23
56/67

Comments: published in Astronomy Reports, translated by Yandex translator with correction of scientific lexis, 7 pages, 3 figures, 2 tables

Magnetar central engines in gamma-ray busts follow the universal relation of accreting magnetic stars [HEAP]

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http://arxiv.org/abs/2305.00029


Gamma-ray bursts (GRBs), both long and short, are explosive events whose inner engine is generally expected to be a black hole or a highly magnetic neutron star (magnetar) accreting high density matter. Recognizing the nature of GRB central engines, and in particular the formation of neutron stars (NSs), is of high astrophysical significance. A possible signature of NSs in GRBs is the presence of a plateau in the early X-ray afterglow. Here we carefully select a subset of long and short GRBs with a clear plateau, and look for an additional NS signature in their prompt emission, namely a transition between accretion and propeller in analogy with accreting, magnetic compact objects in other astrophysical sources. We estimate from the prompt emission the minimum accretion luminosity below which the propeller mechanism sets in, and the NS magnetic field and spin period from the plateau. We demonstrate that these three quantities obey the same universal relation in GRBs as in other accreting compact objects switching from accretion to propeller. This relation provides also an estimate of the radiative efficiency of GRBs, which we find to be several times lower than radiatively efficient accretion in X-ray binaries and in agreement with theoretical expectations. These results provide additional support to the idea that at least some GRBs are powered by magnetars surrounded by an accretion disc.

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S. Dall’Osso, G. Stratta, R. Perna, et. al.
Tue, 2 May 23
9/57

Comments: 15 pages, 5 figures, accepted for publication in The Astrophysical Journal Letters

GeV Gamma-ray Counterparts of New Candidate Radio Supernova Remnants Reported in the GLEAM Survey [HEAP]

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http://arxiv.org/abs/2305.00209


Recently the Galactic and Extra-galactic All-sky Murchison Widefield Array survey has published 27 new candidate radio supernova remnants (SNRs) which are located within the longitude ranges of 345{\deg} < l < 60{\deg} and 180{\deg} < l < 240{\deg}. To search for the gamma-ray counterparts of these candidate radio SNRs, we analyzed 14 years of {\it Fermi}-LAT data in the energy range of 1 – 300 GeV. There are three promising SNRs; G18.9$-$1.2, G23.1$+$0.1, and G28.3$+$0.2, which we detected at a significance level of $\sim$9$\sigma$, $\sim$13$\sigma$, and $\sim$12$\sigma$, respectively. Here we report the results of our morphological and spectral analyses of G18.9$-$1.2, G23.1$+$0.1, and G28.3$+$0.2. No extended gamma-ray emission is detected for any of these SNRs. Our analysis of the 3 SNRs’ {\it Fermi}-LAT gamma-ray emission showed that their best-fit positions (if assumed point-like) overlap with the locations of the corresponding GLEAM counterparts.

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B. Mese and T. Ergin
Tue, 2 May 23
10/57

Comments: Proceedings of Science; 7th Heidelberg International Symposium on High-Energy Gamma-Ray Astronomy (Gamma2022), 4-8 July 2022, Barcelona, Spain

Vacuum polarization alters the spectra of accreting X-ray pulsars [HEAP]

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http://arxiv.org/abs/2305.00475


It is a common belief that for magnetic fields typical for accreting neutron stars in High-Mass X-ray Binaries vacuum polarization only affects the propagation of polarized emission in the neutron star magnetosphere. We show that vacuum resonances can significantly alter the emission from the poles of accreting neutron stars. The effect is similar to vacuum polarization in the atmospheres of isolated neutron stars and can result in suppression of the continuum and the cyclotron lines. It is enhanced by magnetic Comptonization in the hot plasma and proximity to the electron cyclotron resonance. We present several models to illustrate the vacuum polarization effect for various optically thick media and discuss how the choice of polarization modes affects the properties of the emergent radiation by simulating polarized energy- and angle-dependent radiative transfer. Polarization effects, including vacuum polarization, crucially alter the emission properties. Together with strongly angle- and energy- dependent magnetic Comptonization, they result in a complex spectral shape, which can be described by dips and humps on top of a power-law-like continuum with high-energy cutoff. These effects provide a possible explanation for the common necessity of additional broad Gaussian components and two-component Comptonization models that are used to describe spectra of accreting X-ray pulsars. We also demonstrate the character of depolarization introduced by the radiation field’s propagation inside the inhomogeneous emission region.

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E. Sokolova-Lapa, J. Stierhof, T. Dauser, et. al.
Tue, 2 May 23
14/57

Comments: 4 pages, 6 figures

A Unified $p_\mathrm{astro}$ for Gravitational Waves: Consistently Combining Information from Multiple Search Pipelines [IMA]

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http://arxiv.org/abs/2305.00071


Recent gravitational-wave transient catalogs have used $p_\mathrm{astro}$, the probability that a gravitational-wave candidate is astrophysical, to select interesting candidates for further analysis. Unlike false alarm rates, which exclusively capture the statistics of the instrumental noise triggers, $p_\mathrm{astro}$ incorporates the rate at which triggers are generated by both astrophysical signals and instrumental noise in estimating the probability that a candidate is astrophysical. Multiple search pipelines can independently calculate $p_\mathrm{astro}$, each employing a specific data reduction. While the range of $p_\mathrm{astro}$ results can help indicate the range of uncertainties in its calculation, it complicates interpretation and subsequent analyses. We develop a statistical formalism to calculate a $\textit{unified } p_\mathrm{astro}$ for gravitational-wave candidates, consistently accounting for triggers from all pipelines, thereby incorporating extra information about a signal that is not available with any one single pipeline. We demonstrate the properties of this method using a toy model and by application to the publicly available list of gravitational-wave candidates from the first half of the third LIGO–Virgo–KAGRA observing run. Adopting a unified $p_\mathrm{astro}$ for future catalogs would provide a simple and easy-to-interpret selection criterion that incorporates a more complete understanding of the strengths of the different search pipelines

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S. Banagiri, C. Berry, G. Davies, et. al.
Tue, 2 May 23
23/57

Comments: 18 pages, 5 figures, 1 table

Very-High-Energy Gamma-Ray Afterglows of GRB 201015A and GRB 201216C [HEAP]

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http://arxiv.org/abs/2305.00847


Gamma-ray bursts (GRBs) 201015A and 201216C are valuable cases with detection of very high energy (VHE) gamma-ray afterglows. By analysing their prompt emission data, we find that GRB 201216C is an extremely energetic long GRB with a hard gamma-ray spectrum, while GRB 201015A is a relative sub-energetic, soft spectrum GRB. Attributing their radio-optical-X-ray afterglows to the synchrotron radiation of the relativistic electrons accelerated in their jets, we fit their afterglow lightcurves with the standard external shock model and infer their VHE afterglows from the synchrotron self-Compton scattering process of the electrons. It is found that the jet of GRB 201015A is mid-relativistic ($\Gamma_0=44$) surrounded by a very dense medium ($n=1202$ cm$^{-3}$) and the jet of GRB 201216C is ultra-relativistic ($\Gamma_0=331$) surrounded by a moderate dense medium ($n=5$ cm$^{-3}$). The inferred peak luminosity of the VHE gamma-ray afterglows of GRB 201216C is approximately $10^{-9}$ erg cm$^{-2}$ s$^{-1}$ at $57-600$ seconds after the GRB trigger, making it can be detectable with the MAGIC telescopes at a high confidence level, even the GRB is at a redshift of 1.1. Comparing their intrinsic VHE gamma-ray lightcurves and spectral energy distributions with GRBs~180720B, 190114C, and 190829A, we show that their intrinsic peak luminosity of VHE gamma-ray afterglows at $10^{4}$ seconds post the GRB trigger is variable from $10^{45}$ to $5\times 10^{48}$ erg s$^{-1}$, and their kinetic energy, initial Lorentz factor, and medium density are diverse among bursts.

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L. Zhang, J. Ren, Y. Wang, et. al.
Tue, 2 May 23
26/57

Comments: 18 pages, 9 figures, 1 table. ApJ accepted

Bayesian Inference of Supernova Neutrino Spectra with Multiple Detectors [CL]

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http://arxiv.org/abs/2305.00392


We implement the Bayesian inference to retrieve energy spectra of all neutrinos from a galactic core-collapse supernova (CCSN). To achieve high statistics and full sensitivity to all flavours of neutrinos, we adopt a combination of several reaction channels from different large-scale neutrino observatories, namely inverse beta decay on proton and elastic scattering on electron from Hyper-Kamiokande (Hyper-K), charged current absorption on Argon from Deep Underground Neutrino Experiment (DUNE) and coherent elastic scattering on Lead from RES-NOVA. Assuming no neutrino oscillation or specific oscillation models, we obtain mock data for each channel through Poisson processes with the predictions, for a typical source distance of 10 kpc in our Galaxy, and then evaluate the probability distributions for all spectral parameters of theoretical neutrino spectrum model with Bayes’ theorem. Although the results for either the electron-neutrinos or electron-antineutrinos reserve relatively large uncertainties (according to the neutrino mass hierarchy), a precision of a few percent (i.e., $\pm 1 \% \sim \pm 4 \%$ at a credible interval of $2 \sigma$) is achieved for primary spectral parameters (e.g., mean energy and total emitted energy) of other neutrino species. Moreover, the correlation coefficients between different parameters are computed as well and interesting patterns are found. Especially, the mixing-induced correlations are sensitive to the neutrino mass hierarchy, which potentially makes it a brand new probe to determine the neutrino mass hierarchy in the detection of galactic supernova neutrinos. Finally, we discuss the origin of such correlation patterns and perspectives for further improvement on our results.

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X. Huang, C. Sun, L. Chen, et. al.
Tue, 2 May 23
27/57

Comments: 24 pages, 7 figures, 4 tables

Recent Progress in Modelling the Macro- and Micro-Physics of Radio Jet Feedback in Galaxy Clusters [HEAP]

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http://arxiv.org/abs/2305.00019


Radio jets and the lobes they inflate are common in cool-core clusters and are expected to play a critical role in regulating the heating and cooling of the intracluster medium (ICM). This is an inherently multi-scale problem, and much effort has been made to understand the processes governing the inflation of lobes and their impact on the cluster, as well as the impact of the environment on the jet-ICM interaction, on both macro- and microphysical scales. Developments of new numerical techniques and improving computational resources have seen simulations of jet feedback in galaxy clusters become ever more sophisticated. This ranges from modelling ICM plasma physics processes such as the effects of magnetic fields, cosmic rays and viscosity to including jet feedback in cosmologically evolved cluster environments in which the ICM thermal and dynamic properties are shaped by large-scale structure formation. In this review, we discuss the progress made over the last ~decade in capturing both the macro- and microphysical processes in numerical simulations, highlighting both the current state of the field as well as open questions and potential ways in which these questions can be addressed in the future.

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M. Bourne and H. Yang
Tue, 2 May 23
30/57

Comments: 45 pages, 7 figures, Review Article submitted to Galaxies Special Issue “New Perspectives on Radio Galaxy Dynamics”. Feedback and comments welcome

Linear analysis of the Kelvin-Helmholtz instability in relativistic magnetized symmetric flows [HEAP]

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http://arxiv.org/abs/2305.00036


We study the linear stability of a planar interface separating two fluids in relative motion, focusing on the symmetric configuration where the two fluids have the same properties (density, temperature, magnetic field strength, and direction). We consider the most general case with arbitrary sound speed $c_{\rm s}$, Alfv\’en speed $v_{\rm A}$, and magnetic field orientation. For the instability associated with the fast mode, we find that the lower bound of unstable shear velocities is set by the requirement that the projection of the velocity onto the fluid-frame wavevector is larger than the projection of the Alfv\’en speed onto the same direction, i.e., shear should overcome the effect of magnetic tension. In the frame where the two fluids move in opposite directions with equal speed $v$, the upper bound of unstable velocities corresponds to an effective relativistic Mach number $M_{re} \equiv v/v_{\rm f\perp} \sqrt{(1-v_{\rm f\perp}^2)/(1-v^2)} \cos\theta=\sqrt{2}$, where $v_{rm f\perp}=[v_A^2+c_{\rm s}^2(1-v_A^2)]^{1/2}$ is the fast speed assuming a magnetic field perpendicular to the wavevector (here, all velocities are in units of the speed of light), and $\theta$ is the laboratory-frame angle between the flow velocity and the wavevector projection onto the shear interface. Our results have implications for shear flows in the magnetospheres of neutron stars and black holes — both for single objects and for merging binaries — where the Alfv\’en speed may approach the speed of light.

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A. Chow, M. Rowan, L. Sironi, et. al.
Tue, 2 May 23
43/57

Comments: 11 pages, 7 figures, 1 table, submitted to journal

The $EB$-correlation in Resolved Polarized Images: Connections to Astrophysics of Black Holes [GA]

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http://arxiv.org/abs/2305.00387


We present an in-depth analysis of a newly proposed correlation function in visibility space, between the $E$ and $B$ modes of the linear polarization, hereafter the $EB$-correlation, for a set of time-averaged GRMHD simulations compared with the phase map from different semi-analytic models as well as the Event Horizon Telescope (EHT) 2017 data for M87* source. We demonstrate that the phase map of the time-averaged $EB$-correlation contains novel information that might be linked to the BH spin, accretion state and the electron temperature. A detailed comparison with a semi-analytic approach with different azimuthal expansion modes shows that to recover the morphology of the real/imaginary part of the correlation function and its phase, we require higher orders of these azimuthal modes. To extract the phase features, we propose to use the Zernike polynomial reconstruction developing an empirical metric to break degeneracies between models with different BH spins that are qualitatively similar. We use a set of different geometrical ring models with various magnetic and velocity field morphologies and show that both the image space and visibility based $EB$-correlation morphologies in MAD simulations can be explained with simple fluid and magnetic field geometries as used in ring models. SANEs by contrast are harder to model, demonstrating that the simple fluid and magnetic field geometries of ring models are not sufficient to describe them owing to higher Faraday Rotation depths. A qualitative comparison with the EHT data demonstrates that some of the features in the phase of $EB$-correlation might be well explained by the current models for BH spins as well as electron temperatures, while others may require a larger theoretical surveys.

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R. Emami, S. Doeleman, M. Wielgus, et. al.
Tue, 2 May 23
46/57

Comments: 26 pages, 21 Figures

Determination of the neutron skin of $^{208}$Pb from ultrarelativistic nuclear collisions [CL]

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http://arxiv.org/abs/2305.00015


Emergent bulk properties of matter governed by the strong nuclear force give rise to physical phenomena across vastly different scales, ranging from the shape of atomic nuclei to the masses and radii of neutron stars. They can be accessed on Earth by measuring the spatial extent of the outer skin made of neutrons that characterises the surface of heavy nuclei. The isotope $^{208}$Pb, owing to its simple structure and neutron excess, has been in this context the target of many dedicated efforts. Here, we determine the neutron skin from measurements of particle distributions and their collective flow in $^{208}$Pb+$^{208}$Pb collisions at ultrarelativistic energy performed at the Large Hadron Collider, which are sensitive to the overall size of the colliding $^{208}$Pb ions. By means of state-of-the-art global analysis tools within the hydrodynamic model of heavy-ion collisions, we infer a neutron skin $\Delta r_{np}=0.217\pm0.058$ fm, consistent with nuclear theory predictions, and competitive in accuracy with a recent determination from parity-violating asymmetries in polarised electron scattering. We establish thus a new experimental method to systematically measure neutron distributions in the ground state of atomic nuclei.

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G. Giacalone, G. Nijs and W. Schee
Tue, 2 May 23
47/57

Comments: 8 pages, 6 figures. The Trajectum code can be found at this https URL Plotting routines can be found at this http URL

Hydrodynamic mixing of accretion disk outflows in collapsars: implications for r-process signatures [HEAP]

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http://arxiv.org/abs/2305.00056


The astrophysical environments capable of triggering heavy-element synthesis via rapid neutron capture (the r-process) remain uncertain. While binary neutron star mergers (NSMs) are known to forge r-process elements, certain rare supernovae (SNe) have been theorized to supplement, or even dominate, r-production by NSMs. However, the most direct evidence for such SNe, unusual reddening of the emission caused by the high opacities of r-process elements, has not been observed. Recent work identified the distribution of r-process material within the SN ejecta as a key predictor of the ease with which signals associated with r-process enrichment could be discerned. Though this distribution results from hydrodynamic processes at play during the SN explosion, thus far it has been treated only in a parameterized way. We use hydrodynamic simulations to model how disk winds, the alleged locus of r-production in rare SNe, mix with initially r-process-free ejecta. We study mixing as a function of the wind mass and duration and of the initial SN explosion energy, and find that it increases with the first two of these and decreases with the third. This suggests that SNe accompanying the longest long-duration gamma-ray bursts are promising places to search for signs of r-process enrichment. We use semianalytic radiation transport to connect hydrodynamics to electromagnetic observables, allowing us to assess the mixing level at which the presence of r-process material can be diagnosed from SN light curves. Analytic arguments constructed atop this foundation imply that a wind-driven r-process-enriched SN model is unlikely to explain standard energetic SNe.

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J. Barnes and P. Duffell
Tue, 2 May 23
49/57

Comments: Submitted to ApJ. Comments welcome

The rocket effect mechanism in neutron stars in supernova remnants [HEAP]

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http://arxiv.org/abs/2305.00025


While the dipole magnetic field axis of neutron stars is usually postulated to cross the star’s centre, it may be displaced from this location, as it has been recently indicated in the millisecond pulsar J0030+0451. Under these conditions, the electromagnetic rocket effect may be activated, where the magnetic field exerts a net force, accelerating the star. This post-natal kick mechanism relies on asymmetric electromagnetic radiation from an off-centre dipole may be relevant to the high spatial velocities of pulsars $\sim 10^{3}$ $\rm{km/s}$. Here, we explore its impact in young pulsars associated with supernova remnants and we compare the observational data on characteristic quantities, such as the braking index and proper motion, with results obtained from the rocket effect. Using a Markov Chain Monte Carlo analysis, we explore the required conditions, for the initial spin periods and the distance between the magnetic axis and the star’s center, so that the velocity kick due to the rocket effect approaches the present velocity. We find that the electromagnetic rocket effect can account for typical pulsar transverse velocities assuming an initial spin period of 3.8 $\rm{ms}$ and a dipole field whose distance from the centre of the star is approximately 7 $\rm{km}$. We also explore the influence of the rocket effect on the braking index of a neutron star, and we find that for the sample studied this impact is minimal. Finally, we apply the rocket effect model on the pulsars J0030+0451 and J0538+2817, which are likely candidates for this mechanism.

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V. Agalianou and K. Gourgouliatos
Tue, 2 May 23
54/57

Comments: N/A

FAST Observations of FRB 20220912A: Burst Properties and Polarization Characteristics [HEAP]

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http://arxiv.org/abs/2304.14665


We report the observations of FRB 20220912A using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We conducted 17 observations totaling 8.67 hours and detected a total of 1076 bursts with an event rate up to 390 hr$^{-1}$. The cumulative energy distribution can be well described using a broken power-law function with the lower and higher-energy slopes of $-0.38\pm0.02$ and $-2.07\pm0.07$, respectively. We also report the L band ($1-1.5$ GHz) spectral index of the synthetic spectrum of FRB~20220912A bursts, which is $-2.6\pm0.21$. The average rotation measure (RM) value of the bursts from FRB~20220912A is $-0.08\pm5.39\ \rm rad\,m^{-2}$, close to 0 $\rm rad\,m^{-2}$ and maintain relatively stable over two months. Most bursts have nearly 100\% linear polarization. About 45\% of the bursts have circular polarization with SNR $>$ 3, and the highest circular polarization degree can reach 70\%. Our observations suggest that FRB~20220912A is located in a relatively clean local environment with complex circular polarization characteristics. These various behaviors imply that the mechanism of circular polarization of FRBs likely originates from an intrinsic radiation mechanism, such as coherent curvature radiation or inverse Compton scattering inside the magnetosphere of the FRB engine source (e.g. a magnetar).

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Y. Zhang, D. Li, B. Zhang, et. al.
Mon, 1 May 23
1/51

Comments: 15 pages, 11 figures, 2 tables, submitted to ApJ, comments are welcome!

Revisiting constraints on the photon rest mass with cosmological fast radio bursts [HEAP]

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http://arxiv.org/abs/2304.14784


Fast radio bursts (FRBs) have been suggested as an excellent celestial laboratory for testing the zero-mass hypothesis of the photon. In this work, we use the dispersion measure (DM)–redshift measurements of 23 localized FRBs to revisit the photon rest mass $m_{\gamma}$. As an improvement over previous studies, here we take into account the more realistic probability distributions of DMs contributed by the FRB host galaxy and intergalactic medium (IGM) from the IllustrisTNG simulation. To better account for the systematic uncertainty induced by the choices of priors of cosmological parameters, we also combine the FRB data with the cosmic microwave background data, the baryon acoustic oscillation data, and type Ia supernova data to constrain the cosmological parameters and $m_{\gamma}$ simultaneously. We derive a new upper limit of $m_{\gamma}\le3.8\times 10^{-51}\;\rm{kg}$, or equivalently $m_{\gamma}\le2.1 \times 10^{-15} \, \rm{eV/c^2}$ ($m_{\gamma} \le 7.2 \times 10^{-51} \, \rm{kg}$, or equivalently $m_{\gamma}\le4.0 \times 10^{-15} \, \rm{eV/c^2}$) at $1\sigma$ ($2\sigma$) confidence level. Meanwhile, our analysis can also lead to a reasonable estimation for the IGM baryon fraction $f_{\rm IGM}=0.873^{+0.061}{-0.050}$. With the number increment of localized FRBs, the constraints on both $m{\gamma}$ and $f_{\rm IGM}$ will be further improved. A caveat of constraining $m_{\gamma}$ within the context of the standard $\Lambda$CDM cosmological model is also discussed.

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B. Wang, J. Wei, X. Wu, et. al.
Mon, 1 May 23
4/51

Comments: 14 pages, 2 figures, 3 tables

Finite temperature description of Fermi gases with in-medium effective mass [CL]

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http://arxiv.org/abs/2304.14715


We investigate Fermi gases at finite temperature for which the in-medium effective mass may not be constant as a function of the density, the temperature, or the chemical potential. We suggest a formalism that separates the terms for which the mass is constant from the terms which explicitly treat the correction due to the in-medium effective mass. We employ the ensemble equivalence in infinite matter in order to treat these different terms. Our formalism is applied in nuclear matter and we show its goodness by comparing it to an exact treatment based on the numerical calculation of the Fermi integrals.

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M. Dutra, O. Lourenço and J. Margueron
Mon, 1 May 23
5/51

Comments: 11 pages, 2 figures, 3 tables

Scintillation Arc from FRB 20220912A [HEAP]

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http://arxiv.org/abs/2304.14697


We present the interstellar scintillation analysis of fast radio burst (FRB) 20220912A during its extremely active episode in 2022 using data from the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). We detect a scintillation arc in the FRB’s secondary spectrum, which describes the power in terms of the scattered FRB signals’ time delay and Doppler shift. The arc indicates that the scintillation is caused by a highly localized region of the ionized interstellar medium (IISM). Our analysis favors a Milky Way origin for the localized scattering medium but cannot rule out a host galaxy origin. We present our method for detecting the scintillation arc, which can be applied generally to sources with irregularly spaced bursts or pulses. These methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy.

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Z. Wu, R. Main, W. Zhu, et. al.
Mon, 1 May 23
6/51

Comments: Submitted to SCPMA, 9 pages, 7 figures

Evidence of a lepto-hadronic two-zone emission in flare states [HEAP]

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http://arxiv.org/abs/2304.14534


The BL Lac Markarian 501 exhibited two flaring activities in the very-high-energy (VHE) band in May 2009. The lack of correlation between X-rays and TeV gamma-rays without increasing in other bands suggested that more than one emission zone could be involved. Moreover, fast variability in the flaring state was observed, indicating that the emission zones responsible must have small sizes. We use a lepto-hadronic model with two-zone emission to explain the spectral energy distribution during quiescent and these flaring states. In the proposed scenario, the photopion processes explain the VHE flaring activities successfully, and variability constraints place the activity in a zone located near the jet’s base or named inner blob, while synchrotron self-Compton emission describing the X-ray signature during that flaring state occurs in the zone situated far the central engine or named outer blob.

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E. Aguilar-Ruiz, N. Fraija and A. ámez
Mon, 1 May 23
11/51

Comments: Accepted in The European Physical Journal C

The luminosity function of TDEs from fallback-powered emission: implications for the black hole mass function [HEAP]

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http://arxiv.org/abs/2304.14429


Tidal disruption events (TDEs), in which a star is destroyed by the gravitational field of a supermassive black hole (SMBH), are being observed at a high rate owing to the advanced state of survey science. One of the properties of TDEs that is measured with increasing statistical reliability is the TDE luminosity function, $d\dot{N}{\rm TDE}/dL$, which is the TDE rate per luminosity (i.e., how many TDEs are within a given luminosity range). Here we show that if the luminous emission from a TDE is directly coupled to the rate of return of tidally destroyed debris to the SMBH, then the TDE luminosity function is in good agreement with observations and scales as $\propto L^{-2.5}$ for high luminosities, provided that the SMBH mass function $dN{\bullet}/dM_{\bullet}$ — the number of SMBHs ($N_{\bullet}$) per SMBH mass ($M_{\bullet}$) — is approximately flat in the mass range over which we observe TDEs. We also show that there is a cutoff in the luminosity function at low luminosities that is a result of direct captures, and this cutoff has been tentatively observed. If $dN_{\bullet}/dM_{\bullet}$ is flat, which is in agreement with some observational campaigns, these results suggest that the fallback rate feeds the accretion rate in TDEs. Contrarily, if $dN_{\bullet}/d\log M_{\bullet}$ is flat, which has been found theoretically and is suggested by other observational investigations, then the emission from TDEs is likely powered by another mechanism. Future observations and more TDE statistics, provided by the Rubin Observatory/LSST, will provide additional evidence as to the reality of this tension.

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E. Coughlin and M. Nicholl
Mon, 1 May 23
16/51

Comments: 7 pages, 1 figure, ApJL accepted

An extreme active repeating fast radio burst in a clean environment [HEAP]

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http://arxiv.org/abs/2304.14671


Fast radio bursts (FRBs) are bright millisecond radio bursts at cosmological distances. Only three FRBs have exhibited extreme activities, such as achieving a peak event rate $\gtrsim 100$ hr$^{-1}$ or being persistently active. Only these three among $\sim 50$ known repeating FRBs have circular polarization. We observed the FRB 20220912A with the Robert C. Byrd Green Bank Telescope (GBT) at L-band on 24 October 2022 and detected 128 bursts in 1.4 hours, corresponding to a burst rate of about 90 hr$^{-1}$, which is the highest yet for FRBs observed by the GBT and makes it the fourth extremely active FRB. The median energy of the bursts is $4.0\times10^{37}$ erg, close to the characteristic energy of FRB 20121102A. The average rotation measure (RM) was $-$0.4 rad m$^{-2}$ with unnoticeable intraday RM change, indicating a likely clean environment, in contrast to the other three extremely active repeating FRBs. Most bursts have nearly 100% linear polarization. Approximately 56% of the bright bursts have circular polarization, the highest such fraction among all FRBs. A downward drift in frequency and polarization angle swings were found in our sample. The discovery and characterization of FRB 20220912A support the view that the downward drift in frequency, polarization angle swings, and circular polarization are intrinsic to radiation physics, which may be shared by active repeaters regardless of the environments.

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Y. Feng, D. Li, Y. Zhang, et. al.
Mon, 1 May 23
19/51

Comments: N/A

Hydrodynamics and Nucleosynthesis of Jet-Driven Supernovae I: Parameter Study of the Dependence on Jet Energetics [HEAP]

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http://arxiv.org/abs/2304.14935


Rotating massive stars with initial progenitor masses $M_{\rm prog} \sim$ 25 $M_{\odot}$ — $\sim$140 $M_{\odot}$ can leave rapidly rotating black holes to become collapsars. The black holes and the surrounding accretion disks may develop powerful jets by magneto-hydrodynamics instabilities. The propagation of the jet in the stellar envelope provides the necessary shock heating for triggering nucleosynthesis unseen in canonical core-collapse supernovae. Yet, the energy budget of the jet and its effects on the final chemical abundance pattern are unclear. In this exploratory work, we present a survey on the parameter dependence of collapsar nucleosynthesis on jet energetics. We use the zero-metallicity star with $M_{\rm prog} \sim$ 40 $M_{\odot}$ as the progenitor. The parameters include the jet duration, its energy deposition rate, deposited energy, and the opening angle. We examine the correlations of following observables: (1) the ejecta and remnant masses, (2) the energy deposition efficiency, (3) the $^{56}$Ni production and its correlation with the ejecta velocity, deposited energy, and the ejected mass, (4) the Sc-Ti-V correlation as observed in metal-poor stars, and (5) the [Zn/Fe] ratio as observed in some metal-poor stars. We also provide the chemical abundance table of these explosion models for the use of the galactic chemical evolution and stellar archaeology.

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S. Leung, K. Nomoto and T. Suzuki
Mon, 1 May 23
21/51

Comments: 21 pages, 32 figures. Accepted for publication in the Astrophysical Journal

Systematics of planetary ephemeris reference frames inferred from pulsar timing astrometry [EPA]

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http://arxiv.org/abs/2304.14677


This study aims to investigate the systematics in planetary ephemeris reference frames through pulsar timing observations. We used the published data sets from several pulsar timing arrays and performed timing analyses for each pulsar using different planetary ephemerides retrieved from the Jet Propulsion Laboratory’s Development Ephemeris (DE), Ephemeris of Planets and the Moon (EPM), and INPOP (Int\’egration Num\’erique Plan\’etaire de l’Observatoire de Paris). Then, we compared the timing solutions and modeled the differences in position and proper motion by vector spherical harmonics of the first degree. The timing solutions were also compared with those determined by very long baseline interferometry (VLBI) astrometry. The orientation offsets between the latest editions of the DE, EPM, and INPOP series do not exceed 0.4 milliarcseconds (mas), while the relative spins between these ephemerides are less than 5 microarcseconds per year ($\mathrm{\mu as\,yr^{-1}}$). We do not detect significant glides in either position or proper motion between these ephemerides. The orientation of the pulsar timing frames deviates from that of the VLBI frame from zero by approximately $\mathrm{0.4\,mas}$ when considering the formal uncertainty and possible systematics. The orientation of current planetary ephemeris frames is as accurate as at least 0.4 mas, and the nonrotating is better than $\mathrm{5\,\mu as\,yr^{-1}}$.

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N. Liu, Z. Zhu, J. Antoniadis, et. al.
Mon, 1 May 23
22/51

Comments: 17 pages, 14 figures, 6 tables, to be accepted for publication at A&A

A dynamical model for IRAS 00500+6713: the remnant of a type Iax supernova SN 1181 hosting a double degenerate merger product WD J005311 [SSA]

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http://arxiv.org/abs/2304.14669


IRAS 00500+6713 is a hypothesized remnant of a type Iax supernova SN 1181. Multi-wavelength observations have revealed its complicated morphology; a dusty infrared ring is sandwiched by the inner and outer X-ray nebulae. We analyze the archival X-ray data taken by XMM-Newton and Chandra to constrain the angular size, mass, and metal abundance of the X-ray nebulae, and construct a theoretical model describing the dynamical evolution of IRAS 00500+6713, including the effects of the interaction between the SN ejecta and the intense wind enriched with carbon burning ashes from the central white dwarf (WD) J005311. We show that the inner X-ray nebula corresponds to the wind termination shock while the outer X-ray nebula to the shocked interface between the SN ejecta and the interstellar matter. The observed X-ray properties can be explained by our model with an SN explosion energy of $E_\mathrm{ej} = (0.77 \mbox{–} 1.1)\times 10^{48}$~erg, an SN ejecta mass of $M_\mathrm{ej} = 0.18\mbox{–}0.53~M_\odot$, if the currently observed wind from WD J005311 started to blow $t_\mathrm{w} \gtrsim 810$ yr after the explosion, i.e., approximately after A.D. 1990. The inferred SN properties are compatible with those of Type Iax SNe and the timing of the wind launch may correspond to the Kelvin-Helmholtz contraction of the oxygen-neon core of WD J005311 that triggered a surface carbon burning. Our analysis supports that IRAS 00500+6713 is the remnant of SN Iax 1181 produced by a double degenerate merger of oxygen-neon and carbon-oxygen WDs, and WD J005311 is the surviving merger product.

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T. Ko, H. Suzuki, K. Kashiyama, et. al.
Mon, 1 May 23
27/51

Comments: 21 pages, 12 figures, 4 tables

How negative feedback and the ambient environment limit the influence of recombination in common envelope evolution [SSA]

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http://arxiv.org/abs/2304.14840


We perform 3D hydrodynamical simulations to study recombination and ionization during the common envelope (CE) phase of binary evolution, and develop techniques to track the ionic transitions in time and space. We simulate the interaction of a $2\,M_\odot$ red giant branch primary and a $1\,M_\odot$ companion modeled as a particle. We compare a run employing a tabulated equation of state (EOS) that accounts for ionization and recombination, with a run employing an ideal gas EOS. During the first half of the simulations, $\sim15$ per cent more mass is unbound in the tabulated EOS run due to the release of recombination energy, but by simulation end the difference has become negligible. We explain this as being a consequence of (i) the tabulated EOS run experiences a shallower inspiral and hence smaller orbital energy release at late times because recombination energy release expands the envelope and reduces drag, and (ii) collision and mixing between expanding envelope gas, ejecta and circumstellar ambient gas assists in unbinding the envelope, but does so less efficiently in the tabulated EOS run where some of the energy transferred to bound envelope gas is used for ionization. The rate of mass unbinding is approximately constant in the last half of the simulations and the orbital separation steadily decreases at late times. A simple linear extrapolation predicts a CE phase duration of $\sim2\,\mathrm{yr}$, after which the envelope would be unbound.

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L. Chamandy, J. Carroll-Nellenback, E. Blackman, et. al.
Mon, 1 May 23
32/51

Comments: Submitted to MNRAS

RX J0440.9+4431: another supercritical X-ray pulsar [HEAP]

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http://arxiv.org/abs/2304.14881


In the beginning of 2023 the Be transient X-ray pulsar RX J0440.9+4431 underwent a fist-ever giant outburst observed from the source peaking in the beginning of February and reaching peak luminosity of $\sim 4.3\times10^{37}$ erg s$^{-1}$. Here we present the results of a detailed spectral and temporal study of the source based on NuSTAR, INTEGRAL, Swift, and NICER observations performed during this period and covering wide range of energies and luminosities. We find that both the pulse profile shape and spectral hardness change abruptly around $\sim2.8\times10^{37}$ erg s$^{-1}$, which we associate with a transition to super-critical accretion regime and erection of the accretion column. The observed pulsed fraction decreases gradually with energy up to 20 keV (with a local minimum around fluorescence iron line), which is unusual for an X-ray pulsar, and then rises rapidly at higher energies with the pulsations significantly detected up to $\sim120$ keV. The broadband energy spectra of RX J0440.9+4431 at different luminosity states can be approximated with a two-hump model with peaks at energies of about 10-20 and 50-70 keV previously suggested for other pulsars without additional features. In particular an absorption feature around 30 keV previously reported and interpreted as a cyclotron line in the literature appears to be absent when using this model, so the question regarding the magnetic field strength of the neutron star remains open. Instead, we attempted to estimate field using several indirect methods and conclude that all of them point to a relatively strong field of around $B\sim 10^{13}$ G.

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A. Salganik, S. Tsygankov, V. Doroshenko, et. al.
Mon, 1 May 23
35/51

Comments: 11 pages, 10 figures, 2 tables. Submitted to MNRAS

Joint machine learning and analytic track reconstruction for X-ray polarimetry with gas pixel detectors [IMA]

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http://arxiv.org/abs/2304.14425


We present our study on the reconstruction of photoelectron tracks in gas pixel detectors used for astrophysical X-ray polarimetry. Our work aims to maximize the performance of convolutional neural networks (CNNs) to predict the impact point of incoming X-rays from the image of the photoelectron track. A very high precision in the reconstruction of the impact point position is achieved thanks to the introduction of an artificial sharpening process of the images. We find that providing the CNN-predicted impact point as input to the state-of-the-art analytic analysis improves the modulation factor ($\sim 1 \%$ at 3 keV and $\sim 6 \%$ at 6 keV) and naturally mitigates a subtle effect appearing in polarization measurements of bright extended sources known as “polarization leakage”.

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N. Cibrario, M. Negro, N. Moriakov, et. al.
Mon, 1 May 23
37/51

Comments: N/A

Prometheus: An Open-Source Neutrino Telescope Simulation [CL]

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http://arxiv.org/abs/2304.14526


Neutrino telescopes are gigaton-scale neutrino detectors comprised of individual light-detection units. Though constructed from simple building blocks, they have opened a new window to the Universe and are able to probe center-of-mass energies that are comparable to those of collider experiments. \prometheus{} is a new, open-source simulation tailored for this kind of detector. Our package, which is written in a combination of \texttt{C++} and \texttt{Python} provides a balance of ease of use and performance and allows the user to simulate a neutrino telescope with arbitrary geometry deployed in ice or water. \prometheus{} simulates the neutrino interactions in the volume surrounding the detector, computes the light yield of the hadronic shower and the out-going lepton, propagates the photons in the medium, and records their arrival times and position in user-defined regions. Finally, \prometheus{} events are serialized into a \texttt{parquet} file, which is a compact and interoperational file format that allows prompt access to the events for further analysis.

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J. Lazar, S. Meighen-Berger, C. Haack, et. al.
Mon, 1 May 23
41/51

Comments: Code can be found here: this https URL 17 pages. 9 figures. Appendix with detailed examples

ULTRASAT: A wide-field time-domain UV space telescope [IMA]

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http://arxiv.org/abs/2304.14482


The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is scheduled to be launched to geostationary orbit in 2026. It will carry a telescope with an unprecedentedly large field of view (204 deg$^2$) and NUV (230-290nm) sensitivity (22.5 mag, 5$\sigma$, at 900s). ULTRASAT will conduct the first wide-field survey of transient and variable NUV sources and will revolutionize our ability to study the hot transient universe: It will explore a new parameter space in energy and time-scale (months long light-curves with minutes cadence), with an extra-Galactic volume accessible for the discovery of transient sources that is $>$300 times larger than that of GALEX and comparable to that of LSST. ULTRASAT data will be transmitted to the ground in real-time, and transient alerts will be distributed to the community in $<$15 min, enabling a vigorous ground-based follow-up of ULTRASAT sources. ULTRASAT will also provide an all-sky NUV image to $>$23.5 AB mag, over 10 times deeper than the GALEX map. Two key science goals of ULTRASAT are the study of mergers of binaries involving neutron stars, and supernovae: With a large fraction ($>$50%) of the sky instantaneously accessible, fast (minutes) slewing capability and a field-of-view that covers the error ellipses expected from GW detectors beyond 2025, ULTRASAT will rapidly detect the electromagnetic emission following BNS/NS-BH mergers identified by GW detectors, and will provide continuous NUV light-curves of the events; ULTRASAT will provide early (hour) detection and continuous high (minutes) cadence NUV light curves for hundreds of core-collapse supernovae, including for rarer supernova progenitor types.

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Y. Shvartzvald, E. Waxman, A. Gal-Yam, et. al.
Mon, 1 May 23
43/51

Comments: 40 pages, 16 figures, 3 tables. Submitted to the AAS journals

Direct Measurement of the Cosmic-Ray Helium Spectrum from 40 GeV to 250 TeV with the Calorimetric Electron Telescope on the International Space Station [HEAP]

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http://arxiv.org/abs/2304.14699


We present the results of a direct measurement of the cosmic-ray helium spectrum with the CALET instrument in operation on the International Space Station since 2015. The observation period covered by this analysis spans from October 13, 2015 to April 30, 2022 (2392 days). The very wide dynamic range of CALET allowed to collect helium data over a large energy interval, from ~40 GeV to ~250 TeV, for the first time with a single instrument in Low Earth Orbit. The measured spectrum shows evidence of a deviation of the flux from a single power-law by more than 8$\sigma$ with a progressive spectral hardening from a few hundred GeV to a few tens of TeV. This result is consistent with the data reported by space instruments including PAMELA, AMS-02, DAMPE and balloon instruments including CREAM. At higher energy we report the onset of a softening of the helium spectrum around 30 TeV (total kinetic energy). Though affected by large uncertainties in the highest energy bins, the observation of a flux reduction turns out to be consistent with the most recent results of DAMPE. A Double Broken Power Law (DBPL) is found to fit simultaneously both spectral features: the hardening (at lower energy) and the softening (at higher energy). A measurement of the proton to helium flux ratio in the energy range from 60 GeV/n to about 60 TeV/n is also presented, using the CALET proton flux recently updated with higher statistics.

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O. Adriani, Y. Akaike, K. Asano, et. al.
Mon, 1 May 23
50/51

Comments: N/A

Classifying FRB spectrograms using nonlinear dimensionality reduction techniques [HEAP]

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http://arxiv.org/abs/2304.13912


Fast radio bursts (FRBs) are mysterious astronomical phenomena, and it is still uncertain whether they consist of multiple types. In this study we use two nonlinear dimensionality reduction algorithms – Uniform Manifold Approximation and Projection (UMAP) and t-distributed stochastic neighbour embedding (t-SNE) – to differentiate repeaters from apparently non-repeaters in FRBs. Based on the first Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB catalogue, these two methods are applied to standardized parameter data and image data from a sample of 594 sub-bursts and 535 FRBs, respectively. Both methods are able to differentiate repeaters from apparently non-repeaters. The UMAP algorithm using image data produces more accurate results and is a more model-independent method. Our result shows that in general repeater clusters tend to be narrowband, which implies a difference in burst morphology between repeaters and apparently non-repeaters. We also compared our UMAP predictions with the CHIME/FRB discovery of 6 new repeaters, the performance was generally good except for one outlier. Finally, we highlight the need for a larger and more complete sample of FRBs.

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X. Yang, S. Zhang, J. Wang, et. al.
Fri, 28 Apr 23
1/68

Comments: 10 pages, 9 figures, 4 tables, accepted by MNRAS

X-ray Binaries in External Galaxies [HEAP]

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http://arxiv.org/abs/2304.14080


X-ray appearance of normal galaxies is mainly determined by X-ray binaries powered by accretion onto a neutron star or a stellar mass black hole. Their populations scale with the star-formation rate and stellar mass of the host galaxy and their X-ray luminosity distributions show a significant split between star-forming and passive galaxies, both facts being consequences of the dichotomy between high- and low-mass X-ray binaries. Metallicity, IMF and stellar age dependencies, and dynamical formation channels add complexity to this picture. The numbers of high-mass X-ray binaries observed in star-forming galaxies indicate quite high probability for a massive star to become an accretion powered X-ray source once upon its lifetime. This explains the unexpectedly high contribution of X-ray binaries to the Cosmic X-ray Background, of the order of $\sim 10\%$, mostly via X-ray emission of faint star-forming galaxies located at moderate redshifts which may account for the unresolved part of the CXB. Cosmological evolution of the $L_X-{\rm SFR}$ relation can make high-mass X-ray binaries a potentially significant factor in (pre)heating of intergalactic medium in the early Universe.

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M. Gilfanov, G. Fabbiano, B. Lehmer, et. al.
Fri, 28 Apr 23
4/68

Comments: Invited chapter for the Handbook of X-ray and Gamma-ray Astrophysics. Editors: Cosimo Bambi, Andrea Santangelo. Publisher: Springer Singapore, 2023

Cosmic ray density variations in nearby giant molecular clouds [HEAP]

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http://arxiv.org/abs/2304.14107


In this paper, we analyzed 12 years of Fermi LAT gamma-ray data towards three nearby giant molecular clouds (GMCs), i.e., R~CrA, Chamaeleon, and Lupus. We calibrated the gas column density of these regions by using the Planck dust opacity map as well as the Gaia extinction map. With both the gamma-ray observations and gas column density maps, we derived the cosmic ray densities in the three GMCs. We found the derived CR spectra have almost the same shape but significantly different normalizations, which may reflect that the distributions of CRs in the vicinity of solar systems are inhomogeneous.

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J. Liu, B. Liu and R. Yang
Fri, 28 Apr 23
5/68

Comments: 9 pages, 6 figures, to be submitted to JCAP

Revisiting the proton synchrotron radiation in blazar jets: Possible contributions from X-ray to $γ$-ray bands [HEAP]

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http://arxiv.org/abs/2304.13893


The proton synchrotron radiation is considered as the origin of high-energy emission of blazars at times. However, extreme physical parameters are often required. In this work, we propose an analytical method to study the parameter space when applying the proton synchrotron radiation to fit the keV, GeV, and very-high-energy emission of blazar jets. We find that proton synchrotron radiation can fit the high-energy hump when it peaks beyond tens GeV without violating basic observations and theories. For the high-energy hump peaked around GeV band, extreme parameters, such as a super-Eddington jet power and a very strong magnetic field, are required. For the high-energy hump peaked around keV band, if an acceptable parameter space can be found depends on the object’s keV luminosity.

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R. Xue, S. Huang, H. Xiao, et. al.
Fri, 28 Apr 23
7/68

Comments: Accepted for publication in Physical Review D (13 pages, 8 figures)

Detecting Fundamental Vector Fields with LISA [CL]

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http://arxiv.org/abs/2304.14129


The advent of gravitational wave astronomy has seen a huge influx of new predictions for potential discoveries of beyond the Standard Model fields. The coupling of all fundamental fields to gravity, together with its dominance on large scales, makes gravitational physics a rich laboratory to study fundamental physics. This holds especially true for the search for the elusive dark photon, a promising dark matter candidate. The dark photon is predicted to generate instabilities in a rotating black hole spacetime, birthing a macroscopic Bose-Einstein condensate. These condensates can especially form around super massive black holes, modifying the dynamical inspiralling process. This then opens another window to leverage future space-borne gravitational wave antennas to join the hunt for the elusive dark matter particle. This study builds a preliminary model for the gravitational waveform emitted by such a dressed extreme mass-ratio inspiral. Comparing these waveforms to the vacuum scenario allows projections to the potential constrainability on the dark photon mass by space-borne gravitational wave antennas. The superradiant instability of a massive vector field on a Kerr background is calculated and the modification to the dynamics of an inspiralling solar mass-scale compact object is determined with approximations on the backreaction effect of the cloud on the compact object. The end result is the projection that the LISA mission should be able to constrain the dark photon mass using extreme mass ratio inspirals in the range $[1.8 \times 10^{-17}, 4.47 \times 10^{-16}]$ eV.

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S. Fell, L. Heisenberg and D. Veske
Fri, 28 Apr 23
8/68

Comments: 21 Pages, 8 Figures

Extragalactic FXT Candidates Discovered by Chandra (2014-2022) [HEAP]

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http://arxiv.org/abs/2304.13795


Extragalactic fast X-ray transients (FXTs) are short flashes of X-ray photons of unknown origin that last a few minutes to hours. We extend the search for extragalactic FXTs from Quirola et al. 2022 (Paper I; based on sources in the Chandra Source Catalog 2.0, CSC2) to further Chandra archival data between 2014-2022. We extract X-ray data using a method similar to that employed by CSC2 and apply identical search criteria as in Paper I. We report the detection of eight FXT candidates, with peak 0.3-10 keV fluxes between 1$\times$10$^{-13}$ to 1$\times$10$^{-11}$ erg cm$^{-2}$ s$^{-1}$ and $T_{90}$ values from 0.3 to 12.1 ks. This sample of FXTs has likely redshifts between 0.7 to 1.8. Three FXT candidates exhibit light curves with a plateau (${\approx}$1-3 ks duration) followed by a power-law decay and X-ray spectral softening, similar to what was observed for a few previously reported FXTs in Paper I. In light of the new, expanded source lists (eight FXTs with known redshifts from Paper I and this work), we update the event sky rates derived in Paper I, finding 36.9$_{-8.3}^{+9.7}$ deg$^{-2}$ yr$^{-1}$ for the extragalactic samples for a limiting flux of ${\gtrsim}$1${\times}$10$^{-13}$ erg cm$^{-2}$ s$^{-1}$, calculate the first FXT X-ray luminosity function, and compare the volumetric density rate between FXTs and other transient classes. Our latest Chandra-detected extragalactic FXT candidates boost the total Chandra sample by $\sim$50 %, and appear to have a similar diversity of possible progenitors.

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J. Quirola-Vásquez, F. Bauer, P. Jonker, et. al.
Fri, 28 Apr 23
11/68

Comments: 37 pages, 19 figures, 11 tables, accepted for publication in A&A. arXiv admin note: text overlap with arXiv:2201.07773

IDEFIX: a versatile performance-portable Godunov code for astrophysical flows [IMA]

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http://arxiv.org/abs/2304.13746


Exascale super-computers now becoming available rely on hybrid energy-efficient architectures that involve an accelerator such as Graphics Processing Units (GPU). Leveraging the computational power of these machines often means a significant rewrite of the numerical tools each time a new architecture becomes available. To address these issues, we present Idefix, a new code for astrophysical flows that relies on the Kokkos meta-programming library to guarantee performance portability on a wide variety of architectures while keeping the code as simple as possible for the user. Idefix is based on a Godunov finite-volume method that solves the non-relativistic HD and MHD equations on various grid geometries. Idefix includes a wide choice of solvers and several additional modules (constrained transport, orbital advection, non-ideal MHD) allowing users to address complex astrophysical problems. Idefix has been successfully tested on Intel and AMD CPUs (up to 131 072 CPU cores on Irene-Rome at TGCC) as well as NVidia and AMD GPUs (up to 1024 GPUs on Adastra at CINES). Idefix achieves more than 1e8 cell/s in MHD on a single NVidia V100 GPU and 3e11 cell/s on 256 Adastra nodes (1024 GPUs) with 95% parallelization efficiency (compared to a single node). For the same problem, Idefix is up to 6 times more energy efficient on GPUs compared to Intel Cascade Lake CPUs. Idefix is now a mature exascale-ready open-source code that can be used on a large variety of astrophysical and fluid dynamics applications.

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G. Lesur, S. Baghdadi, G. Wafflard-Fernandez, et. al.
Fri, 28 Apr 23
20/68

Comments: 18 pages, 18 figures, 3 tables, accepted for publication in Astronomy & Astrophysics

GRB 221009A Afterglow from a Shallow Angular Structured Jet [HEAP]

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http://arxiv.org/abs/2304.14331


The afterglows of exceptionally bright gamma-ray bursts (GRBs) can reveal the angular structure of their ultra-relativistic jets after they emerge from the confining medium, e.g. the progenitor’s stellar envelope in long-soft GRBs. These jets appear to have a narrow core (of half-opening angle $\theta_c$), beyond which their kinetic energy drops as a power-law with the angle $\theta$ from the jet’s symmetry axis, $E_{k,\rm iso}(\theta)\propto[1+(\theta/\theta_c)^2]^{-a/2}$. The power-law index $a$ reflects the amount of mixing between the shocked jet and confining medium, which depends on the jet’s inital magnetization. Weakly magnetized jets undergo significant mixing, leading to shallow ($a\lesssim2$) angular profiles. Here we use the exquisite multi-waveband afterglow observations of GRB 221009A to constrain the jet angular structure using a dynamical model that accounts for both the forward and reverse shocks, for a power-law external density radial profile, $n_{\rm{}ext}\propto{}R^{-k}$. Both the forward shock emission, that dominates the optical and X-ray flux, and the reverse shock emission, that produces the radio afterglow, require a jet with a narrow core ($\theta_c\approx0.021$) and a shallow angular structure ($a\approx0.8$) expanding into a stellar wind ($k\approx2$). In addition, the fraction of shock-heated electrons forming a relativistic power-law energy distribution is limited to $\xi_e\approx10^{-2}$ in both shocks.

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R. Gill and J. Granot
Fri, 28 Apr 23
26/68

Comments: 5 pages, 3 figures. Submitted

Stellar wind variability in Cygnus X-1 from high-resolution excess variance spectroscopy with Chandra [HEAP]

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http://arxiv.org/abs/2304.14201


Stellar winds of massive stars are known to be driven by line absorption of UV photons, a mechanism which is prone to instabilities, causing the wind to be clumpy. The clumpy structure hampers wind mass-loss estimates, limiting our understanding of massive star evolution. The wind structure also impacts accretion in high-mass X-ray binary (HMXB) systems. We analyse the wavelength-dependent variability of X-ray absorption in the wind to study its structure. Such an approach is possible in HMXBs, where the compact object serves as an X-ray backlight. We probe different parts of the wind by analysing data taken at superior and inferior conjunction. We apply excess variance spectroscopy to study the wavelength-dependent soft X-ray variability of the HMXB Cygnus X-1 in the low/hard spectral state. Excess variance spectroscopy quantifies the variability of an object above the statistical noise as a function of wavelength, which allows us to study the variability of individual spectral lines. As one of the first studies, we apply this technique to high-resolution gratings spectra provided by Chandra, accounting for various systematic effects. The frequency dependence is investigated by changing the time binning. The strong orbital phase dependence we observe in the excess variance is consistent with column density variations predicted by a simple model for a clumpy wind. We identify spikes of increased variability with spectral features found by previous spectroscopic analyses of the same data set, most notably from silicon in over-dense clumps in the wind. In the silicon line region, the variability power is redistributed towards lower frequencies, hinting at increased line variability in large clumps. In prospect of the microcalorimetry missions that are scheduled to launch within the next decade, excess variance spectra present a promising approach to constrain the wind structure.

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L. Härer, M. Parker, I. Mellah, et. al.
Fri, 28 Apr 23
29/68

Comments: Submitted to A&A

Bursts from Space: MeerKAT – The first citizen science project dedicated to commensal radio transients [HEAP]

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http://arxiv.org/abs/2304.14157


The newest generation of radio telescopes are able to survey large areas with high sensitivity and cadence, producing data volumes that require new methods to better understand the transient sky. Here we describe the results from the first citizen science project dedicated to commensal radio transients, using data from the MeerKAT telescope with weekly cadence. Bursts from Space: MeerKAT was launched late in 2021 and received ~89000 classifications from over 1000 volunteers in 3 months. Our volunteers discovered 142 new variable sources which, along with the known transients in our fields, allowed us to estimate that at least 2.1 per cent of radio sources are varying at 1.28 GHz at the sampled cadence and sensitivity, in line with previous work. We provide the full catalogue of these sources, the largest of candidate radio variables to date. Transient sources found with archival counterparts include a pulsar (B1845-01) and an OH maser star (OH 30.1-0.7), in addition to the recovery of known stellar flares and X-ray binary jets in our observations. Data from the MeerLICHT optical telescope, along with estimates of long time-scale variability induced by scintillation, imply that the majority of the new variables are active galactic nuclei. This tells us that citizen scientists can discover phenomena varying on time-scales from weeks to several years. The success both in terms of volunteer engagement and scientific merit warrants the continued development of the project, whilst we use the classifications from volunteers to develop machine learning techniques for finding transients.

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A. Andersson, C. Lintott, R. Fender, et. al.
Fri, 28 Apr 23
31/68

Comments: Accepted to MNRAS, 14 pages + an appendix containing our main data table

Spiral wave driven accretion in quiescent dwarf novæ [HEAP]

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http://arxiv.org/abs/2304.13773


In dwarf nov{\ae} and low-mass X-ray binaries, the tidal potential excites spiral waves in the accretion disc. Spiral wave driven accretion may be important in quiescent discs, where the angular momentum transport mechanism has yet to be identified. Previous studies were limited to unrealistically high temperatures for numerical studies or to specific regimes for analytical studies. We perform the first numerical simulation of spiral wave driven accretion in the cold temperature regime appropriate to quiescent discs, which have Mach numbers > 100. We use the new GPU-accelerated finite volume code Idefix to produce global hydrodynamics 2D simulations of the accretion discs of dwarf nov{\ae} systems with a fine-enough spatial resolution to capture the short scale-height of cold, quiescent discs with Mach numbers ranging from 80 to 370. Running the simulations on timescales of tens of binary orbits shows transient angular momentum transport that decays as the disc relaxes from its initial conditions. We find the angular momentum parameter {\alpha} drops to values << 0.01 , too weak to drive accretion in quiescence.

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M. Bossche, G. Lesur and G. Dubus
Fri, 28 Apr 23
40/68

Comments: N/A

X-ray flares in long-term light curve of low luminosity AGN – M81* [HEAP]

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http://arxiv.org/abs/2304.14265


Most active galactic nuclei (AGNs) at the center of the nearby galaxies have super-massive black holes accreting at sub-Eddington rates through hot accretion flows or radiatively inefficient accretion flows, which efficiently produce jets. The association of radio and X-ray flares with the knot ejection from M81* inspires us to model its multi-wavelength spectral energy distribution during these flares to constrain the physical parameters of the jet. Moreover, we construct a long-term light curve in X-rays to identify the flares in the available data and constrain the jet parameters during those periods. The jet activity may vary on short and long time scales, which may produce flares in different frequency bands. The spectral energy distributions from radio to X-ray during the quiescent as well as flaring states are found to be satisfactorily explained by synchrotron emission of relativistic electrons from a single zone. The variation in the values of the jet parameters during the different states is shown and compared with high synchrotron peaked blazars.

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G. Tomar and N. Gupta
Fri, 28 Apr 23
41/68

Comments: 14 pages, 7 figures, 1 table; Under review at ApJ

Discovery of two promising isolated neutron star candidates in the SRG/eROSITA All-Sky Survey [HEAP]

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http://arxiv.org/abs/2304.14066


We report the discovery of the isolated neutron star (INS) candidates eRASSU J065715.3+260428 and eRASSU J131716.9-402647 from the Spectrum Roentgen Gamma (SRG) eROSITA All-Sky Survey. Selected for their soft X-ray emission and absence of catalogued counterparts, both objects were recently targeted with the Large Binocular Telescope and the Southern African Large Telescope. The absence of counterparts down to deep optical limits (25 mag, 5$\sigma$) and, as a result, large X-ray-to-optical flux ratios in both cases strongly suggest an INS nature. The X-ray spectra of both sources are well described by a simple absorbed blackbody, whereas other thermal and non-thermal models (e.g. a hot-plasma emission spectrum or power law) are disfavoured by the spectral analysis. Within the current observational limits, and as expected for cooling INSs, no significant variation ($>2\sigma$) has been identified over the first two-year time span of the survey. Upcoming dedicated follow-up observations will help us to confirm the candidates’ nature.

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J. Kurpas, A. Schwope, A. Pires, et. al.
Fri, 28 Apr 23
42/68

Comments: 11 pages, 8 figures, accepted for publication in A&A

Constraining mass-transfer and common-envelope physics with post-supernova companion monitoring [SSA]

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http://arxiv.org/abs/2304.13864


We present an analytical model that describes the response of companion stars after being impacted by a supernova in a close binary system. This model can be used to constrain the pre-supernova binary properties using photometry of the companion star several years after the explosion in a relatively simple manner. The derived binary parameters are useful in constraining the evolutionary scenario for the progenitors and the physics of binary interactions. We apply our model to the observed photometry of some known stripped-envelope supernova companions (SN1993J, SN2001ig, SN2006jc, SN2011dh, SN2013ge). Combined with other observational constraints such as the pre-supernova progenitor photometry, we find that SN1993J and SN2011dh likely had relatively massive companions on wide orbits, while SN2006jc may have had a relatively low-mass companion on a tight orbit. This trend suggests that type IIb supernova progenitors evolved from stable mass transfer channels and type Ibc progenitors may have formed from common-envelope channels. The constraints on orbital separation helps us probe the highly uncertain common-envelope physics for massive stars, especially with multiple epochs of companion observations.

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R. Hirai
Fri, 28 Apr 23
48/68

Comments: 7 pages, 8 figures. Submitted to MNRAS. Comments welcome

Periodic orbits and their gravitational wave radiations in a polymer black hole in loop quantum gravity [CL]

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http://arxiv.org/abs/2304.14160


This article provides a detailed investigation into the motion of the surrounding particles around a polymer black hole in loop quantum gravity (LQG). Using effective potential, the critical bound orbits and innermost stable circular orbits (ISCO) are analyzed. The study finds that the radii and angular momentum of the critical bound orbits decrease with an increase in the parameter $A_\lambda$ which labels the LQG effects, while the energy and angular momentum of the ISCO also decreases with an increase in $A_\lambda$. Based on these findings, we then explore the periodic orbits of the polymer black hole in LQG using rational numbers composed of three integers. Our results show that the rational numbers increase with the energy of particles and decrease with the increase of angular momentum based on a classification scheme. Moreover, compared to a Schwarzschild black hole, the periodic orbits in a polymer black hole in LQG consistently have lower energy, providing a potential method for distinguishing a polymer black hole in LQG from a Schwarzschild black hole. Finally, we also examine the gravitational wave radiations of the periodic orbits of a test object which orbits a supermassive polymer black hole in LQG, which generates intricate GW waveforms that can aid in exhibiting the gravitational structure of the system.

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Z. Tu, T. Zhu and A. Wang
Fri, 28 Apr 23
54/68

Comments: 14 pages, 10 figures, 2 tables

Probing AGN variability with the Cherenkov Telescope Array [HEAP]

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http://arxiv.org/abs/2304.14208


Relativistic jets launched by Active Galactic Nuclei are among the most powerful particle accelerators in the Universe. The emission over the entire electromagnetic spectrum of these relativistic jets can be extremely variable with scales of variability from less than few minutes up to several years. These variability patterns, which can be very complex, contain information about the acceleration processes of the particles and the area(s) of emission. Thanks to its sensitivity, five-to twenty-times better than the current generation of Imaging Atmospheric Cherenkov Telescopes depending on energy, the Cherenkov Telescope Array will be able to follow the emission from these objects with a very accurate time sampling and over a wide spectral coverage from 20 GeV to > 20 TeV and thus reveal the nature of the acceleration processes at work in these objects. We will show the first results of our lightcurve simulations and long-term behavior of AGN as will be observed by CTA, based on state-of-art particle acceleration models.

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F. Cangemi, T. Hovatta, E. Lindfors, et. al.
Fri, 28 Apr 23
57/68

Comments: Proceedings for Gamma 2022, 8 pages, 6 figures

Muon puzzle in ultra-high energy EASs according to Yakutsk array and Auger experiment data [HEAP]

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http://arxiv.org/abs/2304.13095


The lateral distribution of particles in extensive air showers from cosmic rays with energy above $10^{17}$ eV registered at the Yakutsk complex array was analyzed. Experimentally measured particle densities were compared to the predictions obtained within frameworks of three ultra-high energy hadron interaction models. The cosmic ray mass composition estimated by the readings of surface-based and underground detectors of the array is consistent with results based on the Cherenkov light lateral distribution data. A comparison was made with the results of direct measurement of the muon component performed at the Pierre Auger Observatory. It is demonstrated that the densities of muon flux measured at Yakutsk array are consistent with results of fluorescent light measurements and disagree with results on muons obtained at the Auger array.

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A. Glushkov, A. Sabourov, L. Ksenofontov, et. al.
Thu, 27 Apr 23
6/78

Comments: 14 pages, 6 figures, 2 tables. Accepted for publication in JETP Letters

Revisiting X-ray-Bright-Optically-Normal-Galaxies with the Chandra Source Catalog [GA]

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http://arxiv.org/abs/2304.13160


X-ray bright optically normal galaxies (XBONGs) are galaxies with X-ray luminosities consistent with those of active galactic nuclei (AGNs) but no evidence of AGN optical emission lines. Crossmatching the Chandra Source Catalog version 2 (CSC2) with the Sloan Digital Sky Survey (SDSS) sample of spectroscopically classified galaxies, we have identified 817 XBONG candidates with LX > 1042 erg s-1 and X-ray to optical flux ratio FXO > 0.1. Comparisons with WISE colors and NIR, optical, UV, and radio luminosities show that the loci of XBONGs are in-between those of control samples of normal galaxies and quasars and are consistent with low-luminosity quasars. We find that 43% of the XBONG sample have X-ray colors suggesting NH > 1022 cm-2, double the fraction in the QSO sample, suggesting that a large fraction of XBONG are highly obscured AGNs. However, ~50% of the XBONGs are not obscured and have X-ray colors harder than those of normal galaxies. Some of these XBONGs have spatially extended X-ray emission. These characteristics suggest that they may be unidentified galaxy groups and clusters. Using the X-ray luminosity functions of QSOs and galaxies/groups/clusters, we estimate the approximate fraction of extended XBONGs to be < 20%. We also assess the approximate fraction of XBONGs whose AGN signatures are diluted by stellar light of host galaxies to be ~30%, based on their redshift and deviation from the extrapolation of the QSO LX-Lr relation.

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D. Kim, A. Malnati, A. Cassity, et. al.
Thu, 27 Apr 23
11/78

Comments: Submitted ApJ. 29 pages, 17 figures

A moderate spin for the black hole in X-ray binary MAXI J1348-630 revealed by Insight-HXMT [HEAP]

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http://arxiv.org/abs/2304.13285


MAXI J1348-630 is a low-mass X-ray black hole binary located in the Galaxy and undergone the X-ray outburst in 2019. We analyzed the observation data in very soft state during the outburst between MJD 58588 and MJD 58596 based on the Insight-HXMT observations from 2 — 20 keV via the continuum fitting method to measure the spin of the stellar-mass black hole in MAXI J1348-630. The inner disk temperature and the apparent inner disk radius were found to be $0.47\pm 0.01 \rm keV$ and $5.33\pm 0.10 \ R_{g}$ from the observation data modeled by the multicolor disc blackbody model. Assuming the distance of the source $D\sim 3.4 \rm kpc$, the mass of the black hole $M\sim 11 \ M_{\odot}$, and the inclination of the system $i\sim 29.2^{\circ}$, the spin is determined to be $a_{\star}=0.41\pm 0.03$ for fixing hardening factor at 1.6 and $n_{H}=8.6\times 10^{21} \rm cm^{-2}$. Besides, considering the uncertainty of the parameters $D, M, i$ of this system, with the Monte Carlo analysis, we still confirm the moderate spin of the black hole as $a_{\star}=0.42^{+0.13}_{-0.50}$. Some spectral parameters (e.g., column density and hardening factor) which could affect the measurements of the BH spin are also briefly discussed.

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H. Wu, W. Wang, N. Sai, et. al.
Thu, 27 Apr 23
19/78

Comments: 10 pages, 14 figures, 5 tables, accept for publication in MNRAS