High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Detecting Lorentz-violation induced by a tensor field with S-star's motion around Sgr A*
Qi Qi, Yu Sang and Xiao-Mei Kuang
Testing Lorentz
symmetry in strong gravitational fields provides a unique probe of extensions to standard model. The orbiting motions of the S-
stars around the supermassive black hole Sgr~A* provide a natural laboratory for such tests. In this paper, we analyze the S2 orbital data focusing on a static and spherically symmetric black hole within Kalb–Ramond
gravity, where the deviations from general relativity are encoded in a single Lorentz-violating parameter $\ell$ introduced by the Kalb–Ramond tensor field. Using a full 14-dimensional Markov Chain Monte Carlo analysis under uniform and Gaussian priors, we obtain $\ell = {1.60 \times 10^{-5}}^{+1.38 \times 10^{-4}}_{-1.76 \times 10^{-4}} $ and $\ell = {-1.02 \times 10^{-5}}^{+1.26 \times 10^{-4}}_{-1.19 \times 10^{-4}} $ at $1\sigma$ confidence level, respectively. These constraints are about three orders of magnitude tighter than those from Event Horizon
Telescope imaging of Sgr~A*. We also perform MCMC simulation by fitting data of S38 and S55
stars, as well as their joint analysis. Our results show that the best fit values of $\ell$ in all simulations are always of $10^{-5}$ order, but S2
star provides the most stringent constraints on the parameters because S2
star has higher precision observational data comparing to the fewer public data for other two
stars.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
A fast, differentiable neural-network surrogate for precessing binary black-hole waveforms
Beka Modrekiladze
Gravitational-wave parameter estimation requires millions of waveform evaluations per event, a cost that constrains real-time inference and population studies. We present a fast, fully differentiable neural-network surrogate for the precessing numerical-relativity model \NRSur{}, spanning its full intrinsic parameter space $\lambda=(q,\,\boldsymbol{\chi}_1,\,\boldsymbol{\chi}_2)$ together with the reference orbital frequency $\omega_0$. Rather than a single polarization at a fixed orientation, the surrogate predicts the inertial-frame spherical-harmonic modes $h_{\ell m}$ ($\ell\leq 4$), so that both polarizations $h_+,h_\times$ at an arbitrary orientation $(\iota,\varphi,\psi)$ are reconstructed from one network evaluation through an analytic, differentiable mode-to-strain projection. Trained on $6\times10^5$ waveforms, it attains a fixed-orientation match of mean $0.975$ (median $0.988$) and an orientation-averaged match of mean $0.940$ (median $0.975$) for $q\in[1,4]$, $|\boldsymbol{\chi}_{1,2}|\leq 0.8$, while keeping the overall strain amplitude physical (median ratio $0.98$). It generates a waveform in $\SI{12}{ms}$ (single) and ${\sim}3.5\times10^4$ per second in batches on a single GPU. Because the mode-to-strain projection is analytic, the surrogate is differentiable in both intrinsic and extrinsic parameters, yielding a full 13-dimensional Fisher
matrix (validated against finite differences) and gradient-based (HMC/NUTS) parameter estimation.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.IM
Fast, low noise, megapixel detector and readout systems for future X-ray astronomy missions
Sven Herrmann, Peter Orel, Tanmoy Chattopadhyay et al. (+22 more)
Next-generation strategic X-ray astronomy missions will require the simultaneous achievement of high angular resolution, large effective collecting area, and wide-field imaging with large-format focal plane detectors. Realizing the associated science objectives–ranging from precision measurements of bright point sources to the detection and characterization of faint diffuse emission-places stringent and, in some cases, competing requirements on detector performance. In particular, high frame rates are necessary to mitigate
photon pile-up in observations of bright sources and to reduce contamination from particle-induced background in measurements of low surface brightness structures. At the same time, these instruments must preserve excellent soft X-ray response, which places tight constraints on read noise and on the fidelity of event characterization. State-of-the-art X-ray charge-coupled devices (CCDs) approach many of the key performance metrics required for these missions, but readout speed remains a primary limitation. Addressing this gap requires readout architectures that scale to high channel count, sustain high pixel throughput, and preserve the low-noise characteristics needed for soft X-ray sensitivity.
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All authors Sven Herrmann, Peter Orel, Tanmoy Chattopadhyay, Haley R. Stueber, Jill Juneau, Abigail Y. Pan, Kevan Donlon, Declan O'Neill, Gregory Prigozhin, Eric D. Miller, R. Glenn Morris, Tonya L. Peshel, Artem Poliszczuk, Beverly LaMarr, Catherine E. Grant, Christopher Leitz, Steven W. Allen, Sebastian Albrecht, Marshall W. Bautz, Michael Cooper, Ajay Dakshinamurthy, Matthew Heine, Anna Schweingruber, Keith Warner, Daniel Wilkins
High Energy Astrophysical Phenomena
Structural quasi-universality in highly magnetized differentially rotating neutron stars
Pratul Manna and Surajit Kalita
Universal relations among macroscopic properties of
neutron stars provide a powerful framework to probe their internal structures while minimizing uncertainties associated with the equation of state (EoS). Although such relations have been extensively studied for uniformly rotating
stars, their extension to differentially rotating and strongly magnetized configurations is relatively less explored. We systematically investigate
equilibrium configurations for a wide range of EoSs, rotation profiles, and
magnetic field strengths with XNS numerical simulation code. For sequences with fixed angular momentum, we analyze the dependence of normalized moment of inertia on compactness. We establish a generalized quasi-universal relation between the moment of inertia and compactness that remains remarkably insensitive to the underlying EoS across uniformly rotating, differentially rotating, and strongly magnetized toroidal configurations. For sequences with fixed angular momentum, the normalized moment of inertia exhibits a quasi-universal dependence on compactness, with deviations primarily due to
magnetic field strength and degree of differential rotation. We derive analytic expressions for these dependencies, enabling a unified phenomenological model applicable over a wide range of stellar configurations. As astrophysical applications, we quantify the systematic bias in magnetar luminosity estimates and the rotational kinetic energy of post-merger remnant of GW170817. These results extend quasi-universal relations beyond the standard assumptions of uniform rotation and weak magnetization, providing a robust framework for interpreting observations of highly magnetized and differentially rotating
neutron stars, and enabling more reliable constraints on their astrophysical properties.
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High Energy Astrophysical Phenomena
The Indian Pulsar Timing Array Data Release 2: III. Search for a Stochastic Gravitational Wave Background
Hemanga Tahbildar, Kunjal Vara, Mayuresh Surnis et al. (+28 more)
We present the first independent search for an isotropic
stochastic gravitational wave background in the second data release of the Indian
Pulsar Timing Array, comprising of 27 millisecond
pulsars monitored simultaneously in two frequency bands with the upgraded Giant Metrewave
Radio Telescope over a maximum 7.2 year baseline. Building on a comprehensive single
pulsar noise analysis, we search for a common uncorrelated red noise process within a
Bayesian inference framework and with the noise-marginalized optimal statistics, and we test the robustness of the result through per-
pulsar dropout analyses and solar-wind exclusion cuts. Leaving the spectral index free, we recover a broad amplitude posterior, $\log_{10} A_{\rm CURN} = -13.71^{+1.06}_{-3.28}$, with an unconstrained spectral index $\gamma_{\rm CURN} = 2.98^{+3.62}_{-2.70}$ and a Savage-Dickey Bayes factor of $2.5$ for a common red process over the no signal model. The optimal-statistic signal to noise ratios for the monopole, dipole, and Hellings-Downs correlations are all consistent with zero. Fixing the spectral index to $\gamma = 13/3$, the value predicted by an idealized toy model in which the background is sourced by a population of supermassive black hole binaries in circular orbits evolving purely under leading-order gravitational radiation reaction, we place a $95\%$ upper limit on the common-process amplitude of $A_{\rm GWB} < 3.4\times10^{-14}$, stable across solar elongation cuts of $10^\circ$, $20^\circ$, and $30^\circ$. This limit lies approximately an order of magnitude above the amplitudes reported by other, longer-running
pulsar timing array experiments. We also demonstrate through simulated
datasets with the addition of simple chromatic and achromatic noise components that it will take at least a 10 year baseline to start recovering the common red noise signal.
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All authors Hemanga Tahbildar, Kunjal Vara, Mayuresh Surnis, Churchil Dwivedi, Bhal Chandra Joshi, Sharika Dhakappa, Aman Srivastava, Shantanu Desai, Abhimanyu Susobhanan, Adya Shukla, Himanshu Grover, P. Arumugam, Manjari Bagchi, Neelam Dhanda Batra, Manoneeta Chakraborty, Shaswata Chowdhury, Debabrata Deb, A. Gopakumar, Sushovan Mondal, Kuldeep Meena, K Nobleson, Avinash Kumar Paladi, Arul Pandian B, Kaustubh Rai, Prerna Rana, Shubhit Sardana, Vidit Singh, Jaikhomba Singha, Keitaro Takahashi, Pratik Tarafdar, Zenia Zuraiq
High Energy Astrophysical Phenomena
Gamma-ray and radio populations of millisecond pulsars in globular clusters
Hannah Lawson and Duncan R. Lorimer
The populations of millisecond
pulsars (MSPs) across the Milky Way's globular cluster (GC) system serve as powerful diagnostics of
neutron star evolution in a variety of dense stellar environments. Using properties of 118 Galactic GCs, we performed Monte Carlo simulations of their gamma-ray fluxes observed by Fermi. We compared two luminosity models: a 3D fundamental plane (model A) and a lognormal distribution (model B). Both models reproduce the observed gamma-ray fluxes and mirror the scaling law with the GC stellar encounter rate established for low-mass X-ray binaries and
radio MSPs. Due to its lower average gamma-ray luminosities, model B predicts a 6-7 times larger MSP population ($5150^{+720}_{-710}$) than model A ($770\pm60$). Furthermore, both models accurately predict a population-wide expectation of roughly three clusters whose aggregate gamma-ray emission is dominated by a single bright MSP. Invoking a
radio-to-gamma-ray luminosity scaling ($L_r \sim 3.5 \times 10^{-7} L_{\gamma}$), we find that model B predicts a mean
radio pseudoluminosity ($\log L_{\rm pseudo} \sim -1.6$) that is fainter than canonical
pulsars. This result is consistent with recent evidence attributing the apparent faintness of Galactic MSPs to
geometric effects. In contrast, model A implies an intrinsically brighter population ($\log L_{\rm pseudo} \sim -0.3$) that lacks a clear physical basis and is inconsistent with the results found for Galactic
pulsars. The larger underlying population of faint millisecond
pulsars predicted by model B could be probed by sensitive surveys with emerging
radio facilities to further constrain the evolutionary pathways of MSPs.
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High Energy Astrophysical Phenomena
Alex Rojewski and Cecilia Lunardini
Gravitational waves originating from unresolved sources, or
stochastic gravitational wave backgrounds (SGWBs), carry precious information about the physics underlying their diverse sources, and represent an important target for future experimental searches. Here, we model the SGWB due to core collapse
supernovae. Using an extensive collection of state-of-the-art, three-dimensional, multi-second
supernova simulations, we characterize the two main components of this background: one at $f \sim 10^{-2} - 1$ Hz, due to anisotropic
neutrino emission (the gravitational wave
memory); the other at $f \gtrsim 10^{2}$ Hz, from the near-core matter dynamics. We find that the
memory component offers the best prospects of detection, as its characteristic peak at $f\sim 0.1$ Hz is within the reach of future space-born detectors. At the peak, the energy density might be comparable to that of backgrounds from slow roll inflation and from possible cosmological relics, thus potentially impacting searches of these important signals.
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High Energy Astrophysical Phenomena
AT 2022csn: A Photometrically Peculiar Optical/UV Tidal Disruption Event in a Type II AGN
Yael Dgany, Iair Arcavi, Grisha Zeltyn et al. (+18 more)
The emission mechanism and host
galaxy preference of optical/UV tidal disruption events (TDEs) are still not entirely understood. We present observations of the TDE AT 2022csn, which is one of the most distant (d_L~726 Mpc) and luminous (L_peak=2.487^(+0.073)_(-0.067)*10^(44) erg/s) optical/UV TDEs observed to date. Although it is a spectroscopically normal H+He TDE, it shows some photometric peculiarities, exhibiting a pronounced double-peaked light curve (with peaks separated by 18.30 pm 2.84 days in the g-band), and lying in the low-temperature and large-radius end of the optical/UV TDE population. The host
galaxy of AT 2022csn shows evidence for a significant starburst within the last ~Gyr consistent with other optical/UV TDEs, but also narrow emission lines that place it within the Type II AGN region of the BPT diagram. Interaction between the TDE and a pre-existing AGN
accretion disk might explain the peculiar photometric properties. However, it is puzzling that a TDE would be visible in a Type II AGN, where according to the AGN unification picture the central region around the supermassive black hole is obscured. We suggest a few scenarios to reconcile this. AT 2022csn together with AT 2019ahk, which shows similar properties, may belong to a new subset of low-temperature, high-radius TDEs in
galaxies with Type II AGN emission features.
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All authors Yael Dgany, Iair Arcavi, Grisha Zeltyn, Sebastian Gomez, Daichi Hiramatsu, Benny Trakhtenbrot, Megan Newsome, Dalya Baron, Craig Pellegrino, Jamison Burke, Nadejda Blagorodnova, David Jones, Gerard-Garcia Moreno, Erez A. Zimmerman, Asaf Horowicz, Avishay Gal-Yam, Mariusz Gromadzki, Edo Berger, Sara Faris, D. Andrew Howell, Harsh Kumar
High Energy Astrophysical Phenomena
Generation of Correlated Time Series for X-ray Astronomy Applications
Seth Rowan Larner, Michael A. Nowak and Jörn Wilms
Cross-spectral methods have become essential for studying
accretion physics in X-ray binaries and active galactic
nuclei, where coherence and phase lag measurements constrain physical models and reveal variability components invisible in power spectra alone. Recent multi-Lorentzian fitting techniques have uncovered new quasi-periodic features through joint analysis of power spectra and cross-spectra, but testing these methods requires synthetic data with realistic statistical properties. We present an
algorithm for generating pairs of time series with arbitrary power spectra, coherence functions, and phase lag profiles. The method extends existing methods by decomposing the dependent time series into coherent and incoherent components, where the coherent part is constructed through a complex transfer function applied to a reference series. We derive the transfer function and normalization required to preserve target spectral shapes while achieving specified cross-spectral properties. We obtain approximate analytic expressions for the variance of coherence and phase lag
estimators and construct the approximate covariance
matrix relating these quantities to the underlying power and cross-spectra. When fitting models jointly to power and cross-spectra, these correlations must be incorporated into the likelihood. We apply the method to a two-Lorentzian model with component-specific phase lags and demonstrate close agreement between input models and generated power spectra, coherence function, and phase lag profile across four decades in frequency.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
The $g$-mode frequencies in cold neutron stars and nuclear saturation parameters
Hajime Sotani and Hajime Togashi
Oscillation frequencies excited in
neutron stars are crucial for extracting their interior properties. In addition to the fundamental and pressure modes, the
gravity ($g$-) modes can be excited even in zero-temperature stellar models due to the composition gradient. In this study, we systematically study the $g$-mode frequencies, focusing on the nucleonic equation of state. Then, we can derive an empirical relation for the 1st $g$-mode frequencies as a function of the stellar compactness and the combination of the nuclear saturation parameters, $\eta_0 \equiv L/K_0$, where $K_0$ and $L$ denote the incompressibility of symmetric nuclear matter and the density dependence of the nuclear
symmetry energy, respectively. If an observed 1st $g$-mode frequency significantly deviates from our empirical relation, it may indicate the emergence of additional degrees of freedom or new compositions inside the
star.
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High Energy Astrophysical Phenomena
Magnetic rigidity reveals the PeVatron acceleration region in SS 433
Jie Liao, Wancheng Xu, Lang Cui et al. (+10 more)
PeVatrons are
cosmic accelerators capable of driving particles to petaelectronvolt (PeV) energies. Recently, microquasar jets have emerged as compelling Galactic PeVatron candidates. This is especially the case for SS 433 as its $>100$ TeV gamma-ray emission is spatially coincident with an atomic cloud. However, the exact region where PeV
protons are accelerated and injected within these jets remains unresolved. Here we report, using archival, multi-frequency VLBA observations, the
magnetic field profile $B(H)$ along the SS 433 inner jet on tens of AU scale, where $H$ is the distance from the central compact object. We find that the field declines as $B(H) \propto H^{-0.50\pm0.12}$, demonstrating that the
magnetic rigidity $B(H)R_{\rm acc}$ grows with $H$ for a conical jet. This implies the Hillas limit ($E_{\rm max} \propto BH$) to lie well beyond a PeV at a few hundred-AU scale, which becomes a highly potential site for accelerating
protons to energies $E_{\rm cut} \simeq 2.6$ PeV inferred from the LHAASO gamma-ray spectrum. These results reveal a hidden PeVatron within the baryonic ejecta of microquasar SS 433, well upstream of the extended TeV-emitting lobes.
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All authors Jie Liao, Wancheng Xu, Lang Cui, Pak-Hin Thomas Tam, Xi Yan, Linuo Yang, Ruo-yu Liu, Liang Chen, Ning Chang, Yong-Feng Huang, Long Ji, Ashutosh Tripathi, Felix Aharonian
High Energy Astrophysical Phenomena
Production of High Energy Neutrinos in the Coronae of Ultraluminous X-ray Sources
Norita Kawanaka and Shigeo S. Kimura
We investigate the possibility of high-energy
neutrino production in coronae associated with ultraluminous X-ray sources (ULXs) as super-Eddington accreting black holes. Adopting the disk-wind-fed corona model, we calculate
stochastic proton acceleration and the resulting
neutrino emission from the ULX corona. We first examine whether the corona can be regarded as a collisionless
plasma, which is a prerequisite for efficient non-thermal particle acceleration. We find that the collisionless condition is satisfied only when the mass
accretion rate is lower than ($\sim 5\dot{M}_{\rm Edd}$). In this regime,
protons are accelerated up to energies of a few tens of TeV and produce
neutrinos through both photomeson ($p\gamma$) and hadronuclear ($pp$) interactions. The importance of hadronuclear interactions increases with
accretion rate owing to the enhanced coronal density, resulting in broad
neutrino spectra shaped by both $p\gamma$ and $pp$ processes. We also derive a correlation between
neutrino and X-ray luminosities, ($L_{\nu,{\rm tot}} \propto L_X^{2.4}$), and estimate the
neutrino flux from nearby ULXs. We show that M82 X-1 is among the most promising targets and may be detectable at the 90% confidence level by future
neutrino observatories. These results suggest that super-Eddington accreting black holes constitute a previously unexplored class of high-energy
neutrino sources.
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High Energy Astrophysical Phenomena · Cross-listed from astro-ph.CO
A refined method for measuring cosmological distances using variability and proper motions in AGN with VLBI-detected counter-jets
Jeffrey A. Hodgson, Anthony Carr, David Parkinson et al. (+6 more)
In a previous paper, we described a `standard speed-gun' (SSG) distance that uses the speed of light to standardize a ruler under the assumption that the
radio variability seen in blazars is causally limited. The apparent size is then measured with Very Long Baseline Interferometry in order to derive the angular diameter distance. A key limitation of this method is that it requires knowledge of the relativistic Doppler factor. Previously, we estimated the distance to the bright
radio source, 3C 84 at the center of the Perseus cluster assuming a Doppler factor of \delta ~ 1. In this paper, we aim to describe how a detected counter-jet and approaching jet proper motions can be used to remove the need for knowledge of the Doppler factor when measuring cosmological distances in this way. Under the assumption of a disk (or spherical) geometry and parameterizing the relationship between the physical emitting region and the variability timescale via a causality correction factor (kappa), we estimate a refined angular diameter distance to 3C 84 (z=0.0178) with statistical errors. Assuming kappa=1, we derive distances of D_A,disk = 78.9(-9.8+11.0) Mpc (or D_A,sphere = 71.2(-8.8+9.7) Mpc). Comparing these results to literature
benchmarks, we find that the spherical assumption yields a distance consistent with local Type Ia
supernovae calibrated to the SH0ES H0, while a disk-like geometry aligns with expectations from a lower H0 cosmology. Ultimately, this demonstrates that utilizing jet and counter-jet kinematics successfully removes the Doppler-factor dependence from the standard speed-gun method, providing a viable independent distance estimate once the
geometric structure of the jet is resolved.
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All authors Jeffrey A. Hodgson, Anthony Carr, David Parkinson, Matteo Statti, Jaehyeon Myeong, Benjamin L'Huillier, Arman Shafieloo, Ioannis Liodakis, Se Heon Oh
High Energy Astrophysical Phenomena
Accretion-induced spin-up: Implications for mass constraints of AMXPs
Xiaoyu Lai
We investigate the influence of the global structure of accreting millisecond X-ray
pulsars (AMXPs) on
accretion-induced
spin-up, using three equations of state (EoS) models representing
neutron stars,
quark stars, and strangeon
stars. By applying the classical
accretion torque formalism, and deriving the
accretion rate and
magnetic field from observations of three AMXPs — XTE J1751-305, SAX J1808.4-3658, and IGR J00291+5934 — we derive mass contours in the plane of luminosity versus
spin-up rate. Our results show that the inferred masses are broadly consistent across the three EoS models, indicating that the method is insensitive to the specific EoS and can serve as an evolutionary channel for constraining the masses of
pulsar-like compact
stars. Notably, we find that SAX J1808.4-3658 and IGR J00291+5934 are constrained to very low masses, while XTE J1751-305 yields a mass consistent with the typical range for
pulsars. Our analysis suggests that future improvements in distance and
spin-up measurements would refine these mass constraints, which could offer crucial evidence to distinguish different EoS models. This paper also presents the idea that using EoS-specific parameters could yield new insights.
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High Energy Astrophysical Phenomena
The progenitors and circumstellar environments of stripped-envelope interacting supernovae from BPASS
B. Warwick, J. Lyman, D. L. Coppejans et al. (+4 more)
Understanding the progenitors of stripped-envelope interacting
supernovae (SEISNe) is crucial for probing the final stages of massive
star evolution. Despite this, their rarity means the nature of their progenitors remains poorly constrained. We investigate the progenitors of SEISNe, using the Binary Population and Spectral Synthesis stellar
evolution models. The 30,153 stellar models that result in hydrogen-poor core-collapse
supernovae (SN) includes both binary and single
stars, spanning 13
metallicities ($Z=10^{-5}$ to $0.04$). Circumstellar material (CSM) formation during their last 100\,kyr is reconstructed from line-driven and Roche lobe overflow (RLOF) mass loss using three scenarios for the CSM, one looking at a wind only distribution for the CSM, and two involving the formation of a circum-binary disc (CBD). Light curve parameters from each scenario are calculated using an analytical model and fiducial SN explosion parameters. We find only the two CBD scenarios, and consequently no single
star models, reproduce the luminosities and rise times of observed SEISNe. The inferred rates are comparable to observations. Expected progenitors were only found in models with ZAMS masses of $14-40\,$M$_{\odot}$ at $\geq Z_\odot$ and $30-40\,$M$_{\odot}$ at $< Z_\odot$. Modelling the
radio emissions shows that early ($\leq8\,$days) and high frequency ($\geq70\,$GHz) observations are required to constrain the nature of CBDs in these systems. These results indicate that, without phenomena such as eruptive mass loss, SEISNe require massive
stars in binary systems in order to produce sufficient masses of CSM and confine them close to the progenitor.
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All authors B. Warwick, J. Lyman, D. L. Coppejans, C. M. Byrne, J. J. Eldridge, M. Pursiainen, E. R. Stanway
High Energy Astrophysical Phenomena
Searching for core-collapse supernovae in binaries with ZTF
Sylvia J. Zhu, Jakob Nordin, Emma de Oña-Wilhelmi et al. (+1 more)
Context. Stripped envelope
supernovae occur in massive
stars that have lost their outer layers before exploding, possibly from binary interactions. Recently, SN 2022jli was detected with significant periodic oscillations in its lightcurve, likely due to
accretion from a binary companion onto the newborn compact object. Aims. While evidence for periodic oscillations has been found in a few bright and noteworthy
supernovae, the population properties are best understood with systematic searches of large data sets. We present prospects for running a search on data from ZTF and similar surveys that is flexible and computationally inexpensive, with the goal of setting up a search in realtime on data from ZTF, LSST, and similar surveys. Methods. We simulate core collapse
supernova lightcurves with additional features from the binary interactions. We use spline fits to remove the underlying
supernova behavior and isolate the periodicities, then apply a Lomb-Scargle periodogram to recover the simulated period. By varying the conditions, we can make recommendations for different kinds of data sets. Finally, we run the search on two sets of archival ZTF
supernovae to illustrate the concept. Results. For a wide range of binary interaction parameters, we find that a long baseline (200 days) of observations with a three-day cadence effectively retrieve ~50% of the binary oscillations. However, this rate plummets with more typical observation durations; only a few percent are recoverable with a 30-day observation, and 10% with a 75-day observation. A substantial fraction of
supernovae could therefore have binary companion interactions that have simply been undetected. Out of 212 moderately bright and well observed ZTF
supernovae, we find suggestions of periodic oscillations in two candidates.
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All authors Sylvia J. Zhu, Jakob Nordin, Emma de Oña-Wilhelmi, Andrea Ercolino
High Energy Astrophysical Phenomena
Abnormal Nitrogen Abundance in the X-ray Spectrum of Quasi-periodically Erupting Source AT2019wzc
Tao Wu, Xinwen Shu, Luming Sun et al. (+3 more)
Quasi-periodic eruptions (QPEs) are rapid, recurring soft X-ray bursts, whose nature is still in dispute. A compelling case of QPEs has emerged in the slowly evolving optical transient AT2019wzc, possibly associated with the tidal disruption of a post-main-sequence
star by a supermassive black hole. Further evidence of a tidal disruption event (TDE) is crucial to understand the nature of AT2019wzc and establish the link between TDE and QPEs. Here we report the detection of a narrow, blueshifted N VI absorption line in its high-resolution X-ray spectra obtained by XMM-Newton, but weak or undetectable absorption lines from other elements of similar ionization states such as carbon and oxygen. The absorption line features can be reproduced by an ionized gas with ionization parameter $\log \xi \sim 0.3\ {\rm erg~cm~s^{-1}}$ and column density $N_{\rm H}\sim 10^{20}\ {\rm cm^{-2}}$, under the condition of a nitrogen abundance of $11.6_{-7.8}^{+19.6}$ times the solar value. This abnormal nitrogen abundance favors a TDE origin for AT2019wzc, and the absorbing gas may originate from the outflow induced by self-collision of the TDE's debris stream.
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All authors Tao Wu, Xinwen Shu, Luming Sun, Ning Jiang, Jiazheng Zhu, Wenjie Zhang
High Energy Astrophysical Phenomena
Parameter Estimation Horizon of Core-Collapse Supernovae with a Network of Gravitational-Wave Detectors
Almat Akhmetali, Y. Sultan Abylkairov, Solange Nunes et al. (+3 more)
Core-collapse
supernovae are among the most promising yet still undetected sources of gravitational waves. A future detection would provide a direct view of the physical processes occurring deep inside a collapsing
star. In this work, we investigate how networks of current and future gravitational-wave detectors can constrain the properties of rapidly rotating core-collapse
supernovae using their characteristic core-bounce and early post-bounce signals. Using deep-learning techniques, we estimate the peak frequency, rotation rate, and signal amplitude from noisy detector data and compare the performance of different detector-network configurations. We find that detector networks improve both parameter recovery and sky coverage. For current-generation networks, estimation of the peak frequency is possible out to about 30 kpc, while the rotation rate and signal amplitude remain recoverable out to distances exceeding 100 kpc. Third-generation observatories extend these distances by nearly an order of magnitude.
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All authors Almat Akhmetali, Y. Sultan Abylkairov, Solange Nunes, José Antonio Font, Michele Zanolin, Ernazar Abdikamalov