Tag Archives: High Energy Astrophysical Phenomena

Multi-Epoch Spectropolarimetry for a Sample of Type IIn Supernovae: Persistent Asymmetry in Dusty Circumstellar Material [HEAP]

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http://arxiv.org/abs/2304.13034


We present multi-epoch spectropolarimetry and spectra for a sample of 14 Type IIn supernovae (SNe IIn). We find that after correcting for likely interstellar polarization, SNe IIn commonly show intrinsic continuum polarization of 1–3% at the time of peak optical luminosity, although a few show weaker or negligible polarization. While some SNe IIn have even stronger polarization at early times, their polarization tends to drop smoothly over several hundred days after peak. We find a tendency for the intrinsic polarization to be stronger at bluer wavelengths, especially at early times. While polarization from an electron scattering region is expected to be grey, scattering of SN light by dusty circumstellar material (CSM) may induce such a wavelength-dependent polarization. For most SNe IIn, changes in polarization degree and wavelength dependence are not accompanied by changes in the position angle, requiring that asymmetric pre-SN mass loss had a persistent geometry. While 2–3% polarization is typical, about 30% of SNe IIn have very low or undetected polarization. Under the simplifying assumption that all SN IIn progenitors have axisymmetric CSM (i.e. disk/torus/bipolar), then the distribution of polarization values we observe is consistent with similarly asymmetric CSM seen from a distribution of random viewing angles. This asymmetry has very important implications for understanding the origin of pre-SN mass loss in SNe IIn, suggesting that it was shaped by binary interaction.

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C. Bilinski, N. Smith, G. Williams, et. al.
Thu, 27 Apr 23
20/78

Comments: 76 pages, 54 figures (13 in main text, 41 in appendix A)

The directional isotropy of LIGO-Virgo binaries [CL]

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http://arxiv.org/abs/2304.13254


We demonstrate how to constrain the degree of absolute alignment of the total angular momenta of LIGO-Virgo binary black holes, looking for a special direction in space that would break isotropy. We also allow for inhomogeneities in the distribution of black holes over the sky. Making use of dipolar models for the spatial distribution and orientation of the sources, we analyze 57 signals with false-alarm rates < 1/yr from the third LIGO-Virgo observing run. Accounting for selection biases, we find the population of LIGO-Virgo black holes to be fully consistent with both homogeneity and isotropy. We additionally find the data to constrain some directions of alignment more than others, and produce posteriors for the directions of total angular momentum of all binaries in our set. All code and data are made publicly available in https://github.com/maxisi/gwisotropy/.

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M. Isi, W. Farr and V. Varma
Thu, 27 Apr 23
21/78

Comments: N/A

Local magneto-shear instability in Newtonian gravity [HEAP]

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http://arxiv.org/abs/2304.13486


The magneto-rotational instability (MRI) – which is due to an interplay between a sheared background and the magnetic field – is commonly considered a key ingredient for developing and sustaining turbulence in the outer envelope of binary neutron star merger remnants. To assess whether (or not) the instability is active and resolved, criteria originally derived in the accretion disk literature – thus exploiting the symmetries of such systems – are often used. In this paper we discuss the magneto-shear instability as a truly local phenomenon, relaxing common symmetry assumptions on the background on top of which the instability grows. This makes the discussion well-suited for highly dynamical environments such as binary mergers. We find that – although this is somewhat hidden in the usual derivation of the MRI dispersion relation – the instability crucially depends on the assumed symmetries. Relaxing the symmetry assumptions on the background we find that the role of the magnetic field is significantly diminished, as it affects the modes’ growth but does not drive it. This suggests that we should not expect the standard instability criteria to provide a faithful indication/diagnostic of what “is actually going on” in mergers. We conclude by making contact with a suitable filtering operation, as this is key to separating background and fluctuations in highly dynamical systems.

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T. Celora, I. Hawke, N. Andersson, et. al.
Thu, 27 Apr 23
24/78

Comments: 15 pages, 1 figure

X-ray Polarimetry of the accreting pulsar 1A~0535+262 in the supercritical state with PolarLight [HEAP]

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http://arxiv.org/abs/2304.13599


The X-ray pulsar 1A 0535+262 exhibited a giant outburst in 2020, offering us a unique opportunity for X-ray polarimetry of an accreting pulsar in the supercritical state. Measurement with PolarLight yielded a non-detection in 3-8 keV; the 99% upper limit of the polarization fraction (PF) is found to be 0.34 averaged over spin phases, or 0.51 based on the rotating vector model. No useful constraint can be placed with phase resolved polarimetry. These upper limits are lower than a previous theoretical prediction of 0.6-0.8, but consistent with those found in other accreting pulsars, like Her X-1, Cen X-3, 4U 1626-67, and GRO J1008-57, which were in the subcritical state, or at least not confidently in the supercritical state, during the polarization measurements. Our results suggest that the relatively low PF seen in accreting pulsars cannot be attributed to the source not being in the supercritical state, but could be a general feature.

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X. Long, H. Feng, H. Li, et. al.
Thu, 27 Apr 23
25/78

Comments: accepted for publication in ApJ

Searching For Stochastic Gravitational Waves Below a Nanohertz [HEAP]

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http://arxiv.org/abs/2304.13042


The stochastic gravitational-wave background is imprinted on the times of arrival of radio pulses from millisecond pulsars. Traditional pulsar timing analyses fit a timing model to each pulsar and search the residuals of the fit for a stationary time correlation. This method breaks down at gravitational-wave frequencies below the inverse observation time of the array; therefore, existing analyses restrict their searches to frequencies above 1 nHz. An effective method to overcome this challenge is to study the correlation of secular drifts of parameters in the pulsar timing model itself. In this paper, we show that timing model correlations are sensitive to sub-nanohertz stochastic gravitational waves and perform a search using existing measurements of binary spin-down rates and pulsar spin-decelerations. We do not observe a signal at our present sensitivity, constraining the stochastic gravitational-wave relic energy density to $\Omega_\text{GW} ( f ) < 3.9 \times 10 ^{ – 9} $ at 450 pHz with sensitivity which scales as the frequency squared until approximately 10 pHz. We place additional limits on the amplitude of a power-law spectrum of $A_\star \lesssim 8\times10^{-15}$ for the spectral index expected from supermassive black hole binaries, $\gamma = 13/3$. If a detection of a supermassive black hole binary signal above 1 nHz is confirmed, this search method will serve as a critical complementary probe of the dynamics of galaxy evolution.

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W. DeRocco and J. Dror
Thu, 27 Apr 23
26/78

Comments: 13 pages, 2 figures

Parameter estimation of binary black holes in the endpoint of the up-down instability [CL]

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http://arxiv.org/abs/2304.13063


Black-hole binary spin precession admits equilibrium solutions corresponding to systems with (anti-) aligned spins. Among these, binaries in the up-down configuration, where the spin of the heavier (lighter) black hole is co- (counter-) aligned with the orbital angular momentum, might be unstable to small perturbations of the spin directions. The occurrence of the up-down instability leads to gravitational-wave sources that formed with aligned spins but are detected with precessing spins. We present a Bayesian procedure based on the Savage-Dickey density ratio to test the up-down origin of gravitational-wave events. This is applied to both simulated signals, which indicate that achieving strong evidence is within the reach of current experiments, and the LIGO/Virgo events released to date, which indicate that current data are not informative enough.

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V. Renzis, D. Gerosa, M. Mould, et. al.
Thu, 27 Apr 23
32/78

Comments: N/A

The width-flux relation of the broad iron line during the state transition of the black hole X-ray binaries [HEAP]

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http://arxiv.org/abs/2304.13358


The observation of varying broad iron lines during the state transition of the black hole X-ray binaries (BHXBs) have been accumulating.In this work, the relation between the normalized intensity and the width of iron lines is investigated, in order to understand better the variation of iron lines and possibly its connection to state transition. Considering the uncertainties due to ionization and illuminating X-rays, only the effects of geometry and gravity are taken into account. Three scenarios were studied, i.e., the continuous disk model, innermost annulus model, and the cloud model. As shown by our calculations, at given iron width, the line flux of the cloud model is smaller than that of the continuous disk model; while for the innermost annulus model, the width is almost unrelated with the flux. The range of the line strength depends on both the BH spin and the inclination of the disk. We then apply to the observation of MAXI J1631-479 by NuSTAR during its decay from the soft state to the intermediate state. We estimated the relative line strength and width according to the spectral fitting results by Xu et al.(2020), and then compared with our theoretical width-flux relation. It was found that the cloud model was more favored. We further modeled the iron line profiles, and found that the cloud model can explain both the line profile and its variation with reasonable parameters.

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H. Shui, F. Xie, Z. Yan, et. al.
Thu, 27 Apr 23
33/78

Comments: 7 figures, 12 pages, accepted for publication in RAA

Measurements of spin and orbital parameters in Cen X-3 by Insight-HXMT [HEAP]

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http://arxiv.org/abs/2304.13279


We present a detailed temporal analysis for the eclipsing high-mass X-ray binary system Cen X-3 using the Insight-HXMT data in 2018 and 2020. Three consecutive and high statistic observations among data are used for the precise timing analysis. The pulse profiles are revealed to vary with energy and time. The pulse profiles for the 2018 observations showed a double peak in the low energy bands below 10 keV and evolved to a single peak in higher energies without the correlation between pulse fraction and flux, and profiles in low energies changed with time. But the pulse profile for the 2020 observation only showed a broad single-peaked pulse in all energy bands with a positive relation between pulse fraction and flux, which may indicate the transition of the emission patterns from a mixture of a pencil and a fan beam to a dominated pencil-like beam. With performing a binary orbital fitting of spin periods, we obtain an accurate value for the spin period and the orbital parameters. The intrinsic spin period of the neutron star is found to be $4.79920 \pm 0.00006$ s at MJD 58852.697, with the orbital period determined at $P_{\rm orb}=2.08695634\pm 0.00000001$ day, and its decay rate of -(1.7832 $\pm$ 0.0001) $\times$ 10$^{-6}$ yr$^{-1}$ for the binary.

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Q. Liu and W. Wang
Thu, 27 Apr 23
34/78

Comments: 12 pages in the authors’ version, reference: Journal of High Energy Astrophysics, 38 (2023), 32-40

Nonlinear Hall effect in a cylinder [HEAP]

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http://arxiv.org/abs/2304.13630


A conducting cylinder, with a uniform magnetic field along its axis, and radial temperature gradient, is considered. At large temperature gradients the azimuthal Hall electrical current creates the axial magnetic field which strength may be comparable with the original one. It is shown, that the magnetic field generated by the azimuthal Hall current leads to the decrease of magnetic field originated by external sources.

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G. Bisnovatyi-Kogan and M. Glushikhina
Thu, 27 Apr 23
40/78

Comments: 15 pages, 13 figures

A ring-like accretion structure in M87 connecting its black hole and jet [HEAP]

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http://arxiv.org/abs/2304.13252


The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation^{1,2}. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole^3. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of 8.4_{-1.1}^{+0.5} Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.

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R. Lu, K. Asada, T. Krichbaum, et. al.
Thu, 27 Apr 23
45/78

Comments: 50 pages, 18 figures, 3 tables, author’s version of the paper published in Nature

The Chandra Source Catalog Normal Galaxy Sample [GA]

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http://arxiv.org/abs/2304.13159


We present an extensive and well-characterized Chandra X-ray Galaxy Catalog (CGC) of 8557 galaxy candidates in the redshift range z ~ 0.04 – 0.7, optical luminosity 1010 – 1011 Lro, and X-ray luminosity (0.5-7 keV) LX = 2×1040 – 2×1043 erg s-1. We estimate ~5% false match fraction and contamination by QSOs. The CGC was extracted from the Chandra Source Catalog version 2 (CSC2) by cross-correlating with optical and IR all-sky survey data, including SDSS, PanSTARRS, DESI Legacy, and WISE. Our selection makes use of two main criteria that we have tested on the subsample with optical spectroscopical identification. (1) A joint selection based on X-ray luminosity (LX) and X-ray to optical flux ratio (FXO), which recovers 63% of the spectroscopically classified galaxies with a small contamination fraction (7%), a significant improvement over methods using LX or FXO alone (< 50% recovery). (2) A joint W1-W2 (W12) WISE color and LX selection that proves effective in excluding QSOs and improves our selection by recovering 72% of the spectroscopically classified galaxies and reducing the contamination fraction (4%). Of the CGC, 24% was selected by means of optical spectroscopy; 30% on the basis of LX, FXO, and W12; and 46% by using either the LX-FXO or the LX-W12 selection criteria. We have individually examined the data for galaxies with z < 0.1, which may include more than one CSC2 X-ray source, leading to the exclusion of 110 local galaxies. Our catalog also includes near-IR and UV data and galaxy morphological types.

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D. Kim, A. Cassity, B. Bhatt, et. al.
Thu, 27 Apr 23
54/78

Comments: submitted ApJS, 35 pages, 11 figures

Repeated patterns of gamma-ray flares reveal structured jets of blazars as likely neutrino sources [HEAP]

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http://arxiv.org/abs/2304.13044


Fermi-LAT observations provide continuous and regularly-sampled measurements of gamma-ray photon flux for hundreds of blazars. Many of these light curves, spanning almost 15 years, have been thoroughly examined for periodicity in multiple studies. However, the possibility that blazars may exhibit irregularly repeating flaring patterns in their gamma-ray light curves has not been systematically explored. In this study, we aim to find repeating episodes of flaring activity in the 100 brightest blazars using Fermi-LAT light curves with various integration times. We use a Bayesian Blocks representation to convert the time series into strings of symbols and search for repeating sub-strings using a fuzzy search algorithm. As a result, we identify 27 repeated episodes in the gamma-ray light curves of 10 blazars. We find that the patterns are most likely produced in structured jets composed of a fast spine and a slower sheath. When individual emission features propagate in the spine, they scatter seed photons produced in the non-uniform sheath through the inverse Compton mechanism, resulting in a set of gamma-ray flares with a similar profile every such passage. Additionally, we explore the theoretically-predicted possibility that the spine-sheath structure facilitates the production of high-energy neutrinos in blazar jets. Using the catalogue of track-like events detected by the IceCube neutrino telescope, we find evidence supporting this hypothesis at a $3.5\sigma$ significance level.

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P. Novikova, E. Shishkina and D. Blinov
Thu, 27 Apr 23
55/78

Comments: Submitted

Do we have enough evidence to invalidate the mean-field approximation adopted to model collective neutrino oscillations? [HEAP]

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http://arxiv.org/abs/2304.13050


Recent body of work points out that the mean-field approximation, widely employed to mimic the neutrino field within a neutrino-dense source, might give different results in terms of flavor evolution with respect to the correspondent many-body treatment. In this paper, we investigate whether such conclusions derived within a constrained framework should hold in an astrophysical context. We show that the plane waves, commonly adopted in the many-body literature to model the neutrino field, provide results that are crucially different with respect to the ones obtained using wavepackets of finite size streaming with a non-zero velocity. The many-body approach intrinsically includes coherent and incoherent scatterings. The mean-field approximation, on the other hand, only takes into account the coherent scattering in the absence of the collision term. Even if incoherent scatterings are included in the mean-field approach, the nature of the collision term is different from that in the many-body approach. Because of this, if only a finite number of neutrinos is considered, as often assumed, the two approaches naturally lead to different flavor outcomes. These differences are further exacerbated by vacuum mixing. We conclude that existing many-body literature, based on closed neutrino systems with a finite number of particles, is neither able to rule out nor assess the validity of the mean-field approach adopted to simulate the evolution of the neutrino field in dense astrophysical sources, which are open systems.

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S. Shalgar and I. Tamborra
Thu, 27 Apr 23
58/78

Comments: 11 pages, 6 figures, 2 column revtex format

Optical study of the polar BM CrB in low accretion state [HEAP]

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http://arxiv.org/abs/2304.13655


This paper presents a spectral and photometric study of the poorly studied polar BM CrB. Three states of the polar brightness and signs of transition from one-pole to two-pole accretion mode were found by an analysis of ZTF data. It is shown that the transition from the low state to the high state changes the longitude of the main accretion spot (by $\approx 17^{\circ}$) and increases its elongation (by $\approx 10^{\circ}$). The spectra contain Zeeman absorptions of the H$\alpha$ line which are formed at a magnetic field strength of $15.5\pm1$ MG. These absorptions are likely produced by a cold halo extending from the accretion spot at $\approx {^1/_4}$ of the white dwarf radius. Modeling of the behavior of the H$\alpha$ emission line shows that the main source of emission is the part of the accretion stream near the Lagrangian point L$_1$, which is periodically eclipsed by the donor star. The spectra exhibit a cyclotron component formed in the accretion spot. Its modeling by a simple accretion spot model gives constraints on the magnetic field strength $B=15-40$ MG and the temperature $T_e\gtrsim15$ keV.

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A. Kolbin, N. Borisov, A. Burenkov, et. al.
Thu, 27 Apr 23
59/78

Comments: N/A

Enhanced Extreme Mass Ratio Inspiral Rates into Intermediate Mass Black Holes [GA]

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http://arxiv.org/abs/2304.13062


Extreme mass ratio inspirals (EMRIs) occur when stellar-mass compact objects begin a gravitational wave (GW) driven inspiral into massive black holes. EMRI waveforms can precisely map the surrounding spacetime, making them a key target for future space-based GW interferometers such as {\it LISA}, but their event rates and parameters are massively uncertain. One of the largest uncertainties is the ratio of true EMRIs (which spend at least thousands of orbits in the {\it LISA} band) and direct plunges, which are in-band for at most a handful of orbits and are not detectable in practice. In this paper, we show that the traditional dichotomy between EMRIs and plunges — EMRIs originate from small semimajor axes, plunges from large — does not hold for intermediate-mass black holes with masses $M_\bullet \lesssim 10^5 M_\odot$. In this low-mass regime, a plunge always has an $\mathcal{O}(1)$ probability of failing and transitioning into a novel “cliffhanger” EMRI. Cliffhanger EMRIs are more easily produced for larger stellar-mass compact objects, and are less likely for smaller ones. This new EMRI production channel can dominate volumetric EMRI rates $\dot{n}{\rm EMRI}$ if intermediate-mass black holes are common in dwarf galactic nuclei, potentially increasing $\dot{n}{\rm EMRI}$ by an order of magnitude.

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I. Qunbar and N. Stone
Thu, 27 Apr 23
61/78

Comments: 8 pages, 6 figures, comments welcome

Bañados-Silk-West effect with finite forces near different types of horizons: general classification of scenarios [CL]

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http://arxiv.org/abs/2304.13087


If two particles move towards a black hole and collide in the vicinity of the horizon, under certain conditions their energy $E_{c.m.}$ in the center of mass frame can grow unbounded. This is the Ba\~{n}ados-Silk-West (BSW) effect. Usually, this effect is considered for extremal horizons and geodesic (or electrogedesic) trajectories. We study this effect in a more general context, when both geometric and dynamic factors are taken into account. We consider generic axially symmetric rotating black holes. The near-horizon behavior of metric coefficients is determined by three numbers $p,~q,$ $k$ that appear in the Taylor expansions for different types of a horizon$.$ This includes nonextremal, extremal and ultraextremal horizons. We also give general classification of possible trajectories that include so-called usual, subcritical, critical and ultracritical ones depending on the near-horizon behavior of the radial component of the four-velocity. We assume that particles move not freely but under the action of some unspecified force. We find when the finiteness of a force and the BSW effect are compatible with each other. The BSW effect implies that one of two particles has fine-tuned parameters. We show that such a particle always requires an infinite proper time for reaching the horizon. Otherwise, either a force becomes infinite or a horizon fails to be regular. This realizes the so-called principle of kinematic censorship that forbids literally infinite $E_{c.m.}$ in any act of collision. The obtained general results are illustrated for the Kerr-Newman-(anti-)de Sitter metric used as an example. The description of diversity of trajectories suggested in our work can be of use also in other contexts, beyond the BSW effect. In particular, we find the relation between a force and the type of a trajectory.

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H. H.V.Ovcharenko and O. O.B.Zaslavskii
Thu, 27 Apr 23
62/78

Comments: 38 pages, 2 figures

Accretion disk wind during the outburst of the stellar-mass black hole MAXI J1348-630 [HEAP]

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http://arxiv.org/abs/2304.13281


We analyzed two observations of the low-mass black hole X-ray binary MAXI J1348-630 from Nuclear Spectroscopic Telescope Array (NuSTAR) during low hard state and hard intermediate state in the 2019 outburst. The reflection components are found in the X-ray spectra, and the spectral fittings give an inclination angle of $\sim 25^\circ-35^\circ$ for the binary system, and there is an absorption line around $\sim 7$ keV coming from highly ionized iron. The photoionization code XSTAR is used to fit the absorption line, which is attributed to outflows with a velocity of $\sim 10^{4}\rm km\ s^{-1}$ along our line of sight and the column density reaching $10^{23}\rm cm^{-2}$ in low hard and hard intermediate states. The physical mechanism launching fast disk winds from the black hole accretion system is still uncertain. These observations strongly support magnetic launching as the dominant mechanism which drives the high velocity, high ionization winds from the inner accretion disk region in hard and hard intermediate states of MAXI J1348-630.

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H. Wu, W. Wang and N. Sai
Thu, 27 Apr 23
66/78

Comments: 12 pages in the authors’ version, reference:Journal of High Energy Astrophysics, 37 (2023), 25-33

A new small glitch in Vela discovered with a hidden Markov model [HEAP]

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http://arxiv.org/abs/2304.13382


A striking feature of the Vela pulsar (PSR J0835$-$4510) is that it undergoes sudden increases in its spin frequency, known as glitches, with a fractional amplitude on the order of $10^{-6}$ approximately every 900 days. Glitches of smaller magnitudes are also known to occur in Vela. Their distribution in both time and amplitude is less well constrained but equally important for understanding the physical process underpinning these events. In order to better understand these small glitches in Vela, an analysis of high-cadence observations from the Mount Pleasant Observatory is presented. A hidden Markov model (HMM) is used to search for small, previously undetected glitches across 24 years of observations covering MJD 44929 to MJD 53647. One previously unknown glitch is detected around MJD 48636 (Jan 15 1992), with fractional frequency jump $\Delta f/f = (8.19 \pm 0.04) \times 10^{-10}$ and frequency derivative jump $\Delta\dot{f}/\dot{f} = (2.98 \pm 0.01) \times 10^{-4}$. Two previously reported small glitches are also confidently re-detected, and independent estimates of their parameters are reported. Excluding these events, 90% confidence frequentist upper limits on the sizes of missed glitches are also set, with a median upper limit of $\Delta f^{90\%}/f = 1.35 \times 10^{-9}$. Upper limits of this kind are enabled by the semi-automated and computationally efficient nature of the HMM, and are crucial to informing studies which are sensitive to the lower end of the glitch size distribution.

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L. Dunn, A. Melatos, C. Espinoza, et. al.
Thu, 27 Apr 23
70/78

Comments: 10 pages, 7 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society

Relativistic Corrections in White Dwarf Asteroseismology [SSA]

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http://arxiv.org/abs/2304.13055


With the precision now afforded by modern space-based photometric observations from the retired K2 and current TESS missions, the effects of general relativity (GR) may be detectable in the light curves of pulsating white dwarfs (WDs). Almost all WD models are calculated using a Newtonian description of gravity and hydrodynamics. To determine if inclusion of GR leads to observable effects, we used idealized models of compact stars and made side-by-side comparison of mode periods computed using a (i) Newtonian and (ii) GR description of the equilibrium structure and nonradial pulsations. For application to white dwarfs, it is only necessary to include the first post-Newtonian (1PN) approximation to GR. The mathematical nature of the linear nonradial pulsation problem is then qualitatively unchanged and the GR corrections can be written as extensions of the classic Dziembowski equations. As such, GR effects might easily be included in existing asteroseismology codes. The idealized stellar models are (i) \pn1 relativistic polytropes and (ii) stars with cold degenerate-electron equation of state featuring a near-surface chemical transition from $\mu_e = 2$ to $\mu_e = 1$, simulating a surface hydrogen layer. Comparison of Newtonian and 1PN normal mode periods reveals fractional differences on the order of the surface gravitational redshift $z$. For a typical WD, this fractional difference is $\sim 10^{-4}$ and is greater than the period uncertainty $\sigma_{\Pi}/\Pi$ of many white dwarf pulsation modes observed by TESS. A consistent theoretical modeling of periods observed in these stars should in principle include GR effects to 1PN order.

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S. Boston, C. Evans and J. Clemens
Thu, 27 Apr 23
71/78

Comments: N/A

Discovery of Two Cyclotron Resonance Scattering Features in X-ray Pulsar Cen X-3 by Insight-HXMT [HEAP]

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http://arxiv.org/abs/2304.13283


We present the results of the neutron star X-ray binary system Cen X-3 performed by $Insight$-HXMT with two observations during 2017 and 2018. During these two observations, the source reached a X-ray luminosity of $\sim 10^{38}$ erg s$^{-1}$ from 2 — 105 keV. The analysis of the broadband X-ray spectrum reports the presence of two cyclotron resonance scattering features (CRSFs) with the fundamental line at $\sim$ 28 keV and the harmonic line at $\sim 47 $ keV. The multiple lines exist by fittings with different continuum models, like the absorbed NPEX model and a power-law with high energy exponential cutoff model. This is the first time that both fundamental and harmonic lines are detected in Cen X-3. We also show evidence of two cyclotron lines in the phase-resolved spectrum of Cen X-3. The CRSF and continuum spectral parameters show evolution with the pulse profile, and the two line centroid energy ratio does not change significantly and locates in a narrow value range of $1.6-1.7$ over the pulse phase. The implications of the discovering two cyclotron absorption features and phase-resolved spectral properties are discussed.

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W. Yang, W. Wang, Q. Liu, et. al.
Thu, 27 Apr 23
72/78

Comments: 8 pages, MNRAS, 2023, 519, 5402-5409

Multi-band Extension of the Wideband Timing Technique [IMA]

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http://arxiv.org/abs/2304.13072


The wideband timing technique enables the high-precision simultaneous estimation of Times of Arrival (ToAs) and Dispersion Measures (DMs) while effectively modeling frequency-dependent profile evolution. We present two novel independent methods that extend the standard wideband technique to handle simultaneous multi-band pulsar data incorporating profile evolution over a larger frequency span to estimate DMs and ToAs with enhanced precision. We implement the wideband likelihood using the libstempo python interface to perform wideband timing in the tempo2 framework. We present the application of these techniques to the dataset of fourteen millisecond pulsars observed simultaneously in Band 3 (300 – 500 MHz) and Band 5 (1260 – 1460 MHz) of the upgraded Giant Metrewave Radio Telescope (uGMRT) as a part of the Indian Pulsar Timing Array (InPTA) campaign. We achieve increased ToA and DM precision and sub-microsecond root mean square post-fit timing residuals by combining simultaneous multi-band pulsar observations done in non-contiguous bands for the first time using our novel techniques.

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A. Paladi, C. Dwivedi, P. Rana, et. al.
Thu, 27 Apr 23
76/78

Comments: Submitted to MNRAS

Millihertz X-ray variability during the 2019 outburst of black hole candidate Swift~J1357.2$-$0933 [HEAP]

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http://arxiv.org/abs/2304.13313


Swift J1357.2$-$0933 is a black-hole candidate X-ray transient, which underwent its third outburst in 2019, during which several multi-wavelength observations were carried out.~Here, we report results from the \emph{Neil Gehrels Swift} and \emph{NICER} observatories and radio data from \emph{AMI}.~For the first time,~millihertz quasi-periodic X-ray oscillations with frequencies varying between ${\sim}$~1–5~$\rm{mHz}$ were found in \emph{NICER} observations and a similar feature was also detected in one \emph{Swift}–\textsc{XRT} dataset.~Our spectral analysis indicate that the maximum value of the measured X-ray flux is much lower compared to the peak values observed during the 2011 and 2017 outbursts.~This value is ${\sim}$~100 times lower than found with \emph{MAXI} on MJD~58558 much ($\sim$~68 days) earlier in the outburst, suggesting that the \emph{Swift} and \emph{NICER} fluxes belong to the declining phase of the 2019 outburst.~An additional soft component was detected in the \textsc{XRT} observation with the highest flux level, but at a relatively low $L_{\rm X}$~$\sim$~$3{\times}10^{34}~(d/{\rm 6~kpc)}^2\rm{erg}~\rm{s}^{-1}$, and which we fitted with a disc component at a temperature of $\sim 0.17$~keV.~The optical/UV magnitudes obtained from \emph{Swift}–\textsc{UVOT} showed a correlation with X-ray observations, indicating X-ray reprocessing to be the plausible origin of the optical and UV emission.~However, the source was not significantly detected in the radio band.~There are currently a number of models that could explain this millihertz-frequency X-ray variability; not least of which involves an X-ray component to the curious dips that, so far, have only been observed in the optical.

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A. Beri, V. Gaur, P. Charles, et. al.
Thu, 27 Apr 23
77/78

Comments: 14 pages, Accepted for publication in MNRAS

Charged particle dynamics in parabolic magnetosphere around Schwarzschild black hole [CL]

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http://arxiv.org/abs/2304.13603


The study of charged particle dynamics in the combined gravitational and magnetic field can provide important theoretical insight into astrophysical processes around black holes. In this paper, we explore the charged particle dynamics in parabolic magnetic field configuration around Schwarzschild black hole, since the paraboloidal shapes of magnetic field lines around black holes are well motivated by the numerical simulations and supported by observations of relativistic jets. Analysing the stability of bounded orbits and using the effective potential approach, we show the possibility of existence of stable circular off-equatorial orbits around the symmetry axis. We also show the influence of radiation reaction force on the dynamics of charged particles, in particular on the chaoticity of the motion and Poincar\'{e} sections, oscillatory frequencies, and emitted electromagnetic spectrum. Applied to Keplerian accretion disks, we show that in parabolic magnetic field configuration, the thin accretion configurations can be either destroyed or transformed into a thick toroidal structure given the radiation reaction and electromagnetic-disk interactions included. Calculating the Fourier spectra for radiating charged particle trajectories, we find that the radiation reaction force does not affect the main frequency peaks, however, it lowers the higher harmonics making the spectrum more flat and diluted in high frequency range.

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M. Kološ, M. Shahzadi and A. Tursunov
Thu, 27 Apr 23
78/78

Comments: 23 pages, 16 figures

X-ray Spectroscopy of Interstellar Carbon: Evidence for Scattering by Carbon-Bearing Material in the Spectrum of 1ES 1553+113 [HEAP]

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http://arxiv.org/abs/2304.12383


Molecules and particles make up $\sim 40 – 70\%$ of carbon in the interstellar medium, yet the exact chemical structure of these constituents remains unknown. We present carbon K-shell absorption spectroscopy of the Galactic Interstellar Medium obtained with the Low Energy Transmission Grating Spectrometer on the {\it Chandra} Observatory, that directly addresses this question. We probe several lines of sight, using bright AGN as backlighters. We make our measurements differentially with respect to the bright source Mrk 421, in order to take the significant carbon K absorption in the instrument into account. In the spectrum of the blazar 1ES 1553+113 we find evidence for a novel feature: strong extinction on the low-energy side of the neutral C $1s-2p$ resonance, which is indicative of scattering by graphite particles. We find evidence for characteristic particle radii of order $0.1-0.15$ $\mu$m. If this explanation for the feature is correct, limits on the mass of the available carbon along the line of sight may imply that the grains are partially aligned, and the X-rays from the source may have intrinsic polarization.

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J. Staunton and F. Paerels
Wed, 26 Apr 23
4/62

Comments: 11 pages, 9 figures, 4 tables

Record-breaking polarization from the interacting superluminous supernova 2017hcc [SSA]

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http://arxiv.org/abs/2304.12368


We present multiepoch spectropolarimetry of the superluminous interacting Type IIn supernova SN2017hcc, covering 16 to 391 days after explosion. In our first epoch we measure continuum polarization as high as 6%, making SN 2017hcc the most intrinsically polarized SN ever reported. During the first 29 days of coverage, when the polarization is strongest, the continuum polarization has a wavelength dependence that rises toward blue wavelengths, and becomes wavelength independent by day 45. The polarization strength drops rapidly during the first month, even as the SN flux is still climbing to peak brightness. Nonetheless, record-high polarization is maintained until day 68, at which point the source polarization declines to 1.9%, comparable to peak levels in previous well-studied SNe IIn. Thereafter the SN continues in polarization decline, while exhibiting only minor changes in position angle on the sky. The blue slope of the polarized continuum during the first month, accompanied by short-lived polarized flux for Balmer emission, suggests that an aspherical distribution of dust grains in pre-shock circumstellar material (CSM) is echoing the SN IIn spectrum and strongly influencing the polarization, while the subsequent decline during the wavelength-independent phase appears broadly consistent with electron scattering near the SN/CSM interface. The persistence of the polarization position angle between these two phases suggests that the pre-existing CSM responsible for the dust scattering at early times is part of the same geometric structure as the electron-scattering region that dominates the polarization at later times. SN2017hcc appears to be yet another, but much more extreme, case of aspherical yet well-ordered CSM in Type IIn SNe, possibly resulting from pre-SN mass loss shaped by a binary progenitor system.

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J. Mauerhan, N. Smith, G. Williams, et. al.
Wed, 26 Apr 23
6/62

Comments: Submitted to MNRAS April 21, 2023

Torque reversal and cyclotron absorption feature in HMXB 4U 1538-522 [HEAP]

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http://arxiv.org/abs/2304.12797


We present a comprehensive timing and spectral analysis of the HMXB 4U 1538-522 by using the Nuclear Spectroscopic Telescope Array (NuSTAR) observatory data. Using three archived observations made between 2019 and 2021, we have detected $\sim $ 526 s coherent pulsations up to 60 keV. We have found an instantaneous spin-down rate of $\dot{P} = 6.6_{-6.0}^{+2.4} \times 10^{-6}$ s s$^{-1}$ during the first observation. The pulse profiles had a double peaked structure consisting of a broad primary peak and an energy dependent, weak secondary peak. We have also analysed the long-term spin-period evolution of 4U 1538-522 from data spanning more than four decades, including the data from Fermi/GBM. Based on the recent spin trends, we have found that the third torque reversal in 4U 1538-522 happened around MJD 58800. The source is currently spinning up with $\dot{P} = -1.9(1) \times 10^{-9}$ s s$^{-1}$. We also report a periodic fluctuation in the spin-period of 4U 1538-522. The broad-band persistent spectra can be described with a blackbody component and either powerlaw or Comptonization component along with a Fe K${\alpha}$ line at 6.4 keV and a cyclotron absorption feature around 22 keV. We have also found a relatively weak absorption feature around 27 keV in the persistent spectra of 4U 1538-522 in all three observations. We have estimated a magnetic field strength of $1.84{-0.06}^{+0.04} (1+z) \times 10^{12}$ and $2.33_{-0.24}^{+0.15} (1+z) \times 10^{12}$ G for the two features, respectively.

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P. Sharma, C. Jain and A. Dutta
Wed, 26 Apr 23
7/62

Comments: Accepted for publication in MNRAS

The high polarisation of the X-rays from the Black Hole X-ray Binary 4U 1630-47 challenges standard thin accretion disc scenario [HEAP]

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http://arxiv.org/abs/2304.12752


Large, energy-dependent X-ray polarisation is observed in 4U 1630-47, a black hole in an X-ray binary, in the high-soft emission state. In this state, X-ray emission is believed to be dominated by a thermal, geometrically thin, optically thick accretion disc. However, the observations with the Imaging X-ray Polarimetry Explorer (IXPE) reveal an unexpectedly high polarisation degree, rising from 6% at 2 keV to 10% at 8 keV, which cannot be reconciled with standard models of thin accretion discs. We argue that an accretion disc with an only partially ionised atmosphere flowing away from the disc at mildly relativistic velocities can explain the observations.

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A. Ratheesh, M. Dovčiak, H. Krawczynski, et. al.
Wed, 26 Apr 23
11/62

Comments: Submitted to Nature Astronomy

Search for correlations of high-energy neutrinos detected in IceCube with radio-bright AGN and gamma-ray emission from blazars [HEAP]

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http://arxiv.org/abs/2304.12675


The IceCube Neutrino Observatory sends realtime neutrino alerts with high probability of being astrophysical in origin. We present a new method to correlate these events and possible candidate sources using $2,089$ blazars from the Fermi-LAT 4LAC-DR2 catalog and with $3,413$ AGNs from the Radio Fundamental Catalog. No statistically significant neutrino emission was found in any of the catalog searches. The result is compatible with a small fraction, $<1$%, of AGNs being neutrino emitters and prior evidence for neutrino emission presented by IceCube and other authors from sources such as TXS 0506+056 and PKS 1502+06. We also present cross-checks to other analyses that claim a significant correlation using similar data samples, and we find that adding more information on the neutrino events and more data overall makes the result compatible with background.

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R. Abbasi, M. Ackermann, J. Adams, et. al.
Wed, 26 Apr 23
16/62

Comments: N/A

An evolutionary model for V404 Cyg system [SSA]

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http://arxiv.org/abs/2304.12894


V404 Cyg is a Low Mass X-Ray Binary (LMXB) system that has undergone outbursts in 1938, 1989, and 2015. During these events, it has been possible to determine relevant data of the system; such as the masses of the compact object (a black hole, BH) and its companion, the orbital period, the companion spectral type, and luminosity class, among others. Remarkably, the companion star has a metallicity appreciably higher than solar. All these data allow us to construct theoretical models to account for its structure, looking for its initial configuration and predicting its final fate. Assuming that the BH is already formed when the primary star reaches the Zero Age Main Sequence, we used our binary evolution code for such a purpose. We obtained that the present characteristics of the system are nicely accounted for by a model with initial masses of 9 solar masses for the BH, 1.5 solar masses for the companion star, an initial orbital period of 1.5 d and considering that at most 30% of the mass transferred by the donor is accreted by the BH. The metallicity of the donor for our best fit was Z = 0.028 (twice solar metallicity). We also studied the evolution of the BH spin parameter assuming that initially, it is not rotating. Remarkably, the spin of the BHs in our models is far from reaching the available observational determination. This may indicate that the BH in V404 Cyg is initially spinning, a result that may be relevant for understanding the formation BHs in the context of LMXB systems.

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L. Koninckx, M. Vito and O. Benvenuto
Wed, 26 Apr 23
21/62

Comments: 10 pages, 12 figures

Cosmic ray transport in large-amplitude turbulence with small-scale field reversals [HEAP]

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http://arxiv.org/abs/2304.12335


The nature of cosmic ray (CR) transport in the Milky Way remains elusive. The predictions of current micro-physical models of CR transport in magneto-hydrodynamic (MHD) turbulence are drastically different from what is observed. These models of transport usually focus on MHD turbulence in the presence of a strong guide field and ignore the impact of turbulent intermittency on particle propagation. This motivates our studying the alternative regime of large-amplitude turbulence with $\delta B/B_0 \gg 1$, in which intermittent small-scale magnetic field reversals are ubiquitous. We study particle transport in such turbulence by integrating trajectories in stationary snapshots. To quantify spatial diffusion, we use a setup with continuous particle injection and escape, which we term the turbulent leaky box. We find that particle transport is very different from the strong-guide-field case. Low-energy particles are better confined than high-energy particles, despite less efficient pitch-angle diffusion at small energies. In the limit of weak guide field, energy-dependent confinement is driven by the energy-dependent (in)ability to follow reversing magnetic field lines exactly and by the scattering in regions of “resonant curvature”, where the field line bends on a scale that is of order the local particle gyro-radius. We derive a heuristic model of particle transport in magnetic folds that approximately reproduces the energy dependence of transport found in the leaky-box experiments. We speculate that CR propagation in the Galaxy is regulated by the intermittent field reversals highlighted here and discuss the implications of our findings for the transport of CRs in the Milky Way.

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P. Kempski, D. Fielding, E. Quataert, et. al.
Wed, 26 Apr 23
25/62

Comments: Submitted to MNRAS, 15 pages, 9 Figures

Lorentz Violation in Finsler Geometry [CL]

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http://arxiv.org/abs/2304.12767


Lorentz invariance is one of the foundations of modern physics; however, Lorentz violation may happen from the perspective of quantum gravity, and plenty of studies on Lorentz violation have arisen in recent years. As a good tool to explore Lorentz violation, Finsler geometry is a natural and fundamental generalization of Riemann geometry. The Finsler structure depends on both coordinates and velocities. Here, we simply introduce the mathematics of Finsler geometry. We review the connection between modified dispersion relations and Finsler geometries and discuss the physical influence from Finsler geometry. We review the connection between Finsler geometries and theories of Lorentz violation, such as the doubly special relativity, the standard-model extension, and the very special relativity.

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J. Zhu and B. Ma
Wed, 26 Apr 23
30/62

Comments: 29 pages, no figure, final version for journal publication

SN 2020udy: a SN Iax with strict limits on interaction consistent with a helium-star companion [HEAP]

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http://arxiv.org/abs/2304.12361


Early observations of transient explosions can provide vital clues to their progenitor origins. In this paper we present the nearby Type Iax (02cx-like) supernova (SN), SN 2020udy that was discovered within hours ($\sim$7 hr) of estimated first light. An extensive dataset of ultra-violet, optical, and near-infrared observations was obtained, covering out to $\sim$150 d after explosion. SN 2020udy peaked at -17.86$\pm$0.43 mag in the r band and evolved similarly to other ‘luminous’ SNe Iax, such as SNe 2005hk and 2012Z. Its well-sampled early light curve allows strict limits on companion interaction to be placed. Main-sequence companion stars with masses of 2 and 6 M$_\odot$ are ruled out at all viewing angles, while a helium-star companion is allowed from a narrow range of angles (140-180$^\circ$ away from the companion). The spectra and light curves of SN2020udy are in good agreement with those of the ‘N5def’ deflagration model of a near Chandrasekhar-mass carbon-oxygen white dwarf. However, as has been seen in previous studies of similar luminosity events, SN 2020udy evolves slower than the model. Broad-band linear polarisation measurements taken at and after peak are consistent with no polarisation, in agreement with the predictions of the companion-star configuration from the early light curve measurements. The host galaxy environment is low metallicity and is consistent with a young stellar population. Overall, we find the most plausible explosion scenario to be the incomplete disruption of a CO white dwarf near the Chandrasekhar-mass limit, with a helium-star companion.

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K. Maguire, M. Magee, G. Leloudas, et. al.
Wed, 26 Apr 23
36/62

Comments: 18 pages, 14 figures, submitted to MNRAS

A radio-emitting outflow produced by the tidal disruption event AT2020vwl [HEAP]

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http://arxiv.org/abs/2304.12661


A tidal disruption event (TDE) occurs when a star is destroyed by a supermassive black hole. Broadband radio spectral observations of TDEs trace the emission from any outflows or jets that are ejected from the vicinity of the supermassive black hole. However, radio detections of TDEs are rare, with less than 20 published to date, and only 11 with multi-epoch broadband coverage. Here we present the radio detection of the TDE AT2020vwl and our subsequent radio monitoring campaign of the outflow that was produced, spanning 1.5 years post-optical flare. We tracked the outflow evolution as it expanded between $10^{16}$ cm to $10^{17}$ cm from the supermassive black hole, deducing it was non-relativistic and launched quasi-simultaneously with the initial optical detection through modelling the evolving synchrotron spectra of the event. We deduce that the outflow is likely to have been launched by material ejected from stream-stream collisions (more likely), the unbound debris stream, or an accretion-induced wind or jet from the supermassive black hole (less likely). AT2020vwl joins a growing number of TDEs with well-characterised prompt radio emission, with future timely radio observations of TDEs required to fully understand the mechanism that produces this type of radio emission in TDEs.

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A. Goodwin, K. Alexander, J. Miller-Jones, et. al.
Wed, 26 Apr 23
37/62

Comments: 15 pages, 9 figures, accepted for publication in MNRAS

Universal relations to measure neutron star properties from targeted r-mode searches [CL]

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http://arxiv.org/abs/2304.12356


R-mode oscillations of rotating neutron stars(NS) are promising candidates for continuous gravitational wave (GW) observations. In our recent work(Ghosh et al. 2023), we derived universal relations of the NS parameters, compactness and dimensionless tidal deformability with the r-mode frequency. In this work, we investigate how these universal relations can be used to infer various NS intrinsic parameters following a successful detection of the r-modes. In particular, we show that for targeted r-mode searches, these universal relations along with the “I-Love-Q” relation can be used to estimate both the moment of inertia and the distance of the NS thus breaking the degeneracy of distance measurement for continuous gravitational wave(CGW) observations. We also discuss that with a prior knowledge of the distance of the NS from electromagnetic observations, these universal relations can also be used to constrain the dense matter equation of state (EOS) inside NS. We quantify the accuracy to which such measurements can be done using the Fisher information matrix for a broad range of possible, unknown parameters, for both the a-LIGO and Einstein Telescope (ET) sensitivities.

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S. Ghosh
Wed, 26 Apr 23
39/62

Comments: 8 pages, 7 figures, Submitted to MNRAS

Broadband X-ray spectral analysis of the ULX NGC 1313\,X-1 using JeTCAF: Origin of the ULX bubble [HEAP]

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http://arxiv.org/abs/2304.12731


NGC 1313\,X-1 is a mysterious Ultra-luminous X-ray (ULX) source whose X-ray powering mechanism and a bubble-like structure surrounding the source are topics of intense study. Here, we perform the X-ray spectroscopic study of the source using a joint {\it XMM-Newton} and {\it NuSTAR} observations taken during 2012 $-$ 2017. The combined spectra cover the energy band 0.3 $-$ 20 keV. We use the accretion-ejection-based JeTCAF model for spectral analysis. The model fitted disc mass accretion rate varies from 4.6 to 9.6 $\dot M_{\rm Edd}$ and the halo mass accretion rate varies from 4.0 to 6.1 $\dot M_{\rm Edd}$ with a dynamic Comptonizing corona of average size of $\sim 15$ $r_g$. The data fitting is carried out for different black hole (BH) mass values. The goodness of the fit and uncertainties in model parameters improve while using higher BH mass with most probable mass of the compact object to be $133\pm33$ M$_\odot$. We have estimated the mass outflow rate, its velocity and power, and the age of the inflated bubble surrounding the source. Our estimated bubble morphology is in accord with the observed optical bubble and winds found through high-resolution X-ray spectroscopy, suggesting that the bubble expanded by the outflows originating from the central source. Finally, we conclude that the super-Eddington accretion onto a nearly intermediate mass BH may power a ULX when the accretion efficiency is low, though their efficiency increases when jet/outflow is taken into account, in agreement with numerical simulations in the literature.

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B. Palit and S. Mondal
Wed, 26 Apr 23
41/62

Comments: 10 pages, 4 figures, 3 tables, accepted (12/04/2023) for publication in PASP

Discovery of extraordinary X-ray emission from magnetospheric interaction in the unique binary stellar system $ε$ Lupi [HEAP]

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http://arxiv.org/abs/2304.12882


We report detailed X-ray observations of the unique binary system $\epsilon$ Lupi, the only known short-period binary consisting of two magnetic early-type stars. The components have comparably strong, but anti-aligned magnetic fields. The orbital and magnetic properties of the system imply that the magnetospheres overlap at all orbital phases, suggesting the possibility of variable inter-star magnetospheric interaction due to the non-negligible eccentricity of the orbit. To investigate this effect, we observed the X-ray emission from $\epsilon$ Lupi both near and away from periastron passage, using the Neutron Star Interior Composition Explorer mission (NICER) X-ray Telescope. We find that the system produces excess X-ray emission at the periastron phase, suggesting the presence of variable inter-star magnetospheric interaction. We also discover that the enhancement at periastron is confined to a very narrow orbital phase range ($\approx 5\%$ of the orbital period), but the X-ray properties close to periastron phase are similar to those observed away from periastron. From these observations, we infer that the underlying cause is magnetic reconnection heating the stellar wind plasma, rather than shocks produced by wind-wind collision. Finally, by comparing the behavior of $\epsilon$ Lupi with that observed for cooler magnetic binary systems, we propose that elevated X-ray flux at periastron phase is likely a general characteristic of interacting magnetospheres irrespective of the spectral types of the constituent stars.

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B. Das, V. Petit, Y. Nazé, et. al.
Wed, 26 Apr 23
44/62

Comments: Accepted for publication in MNRAS (20 pages, 17 figures)

Evidence for two distinct populations of kilonova-associated Gamma Ray Bursts [HEAP]

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http://arxiv.org/abs/2304.12358


Identification of Gamma Ray Burst (GRB) progenitors based on the duration of their prompt emission ($T_{90}$) has faced several roadblocks recently. Long-duration GRBs (with $T_{90} > 2s$) have traditionally been thought to be originating from the collapse of massive stars, and the short-duration ones (with $T_{90} < 2s$) from compact binary mergers. However, recent observations of a long GRB associated with a kilonova (KN) and a short GRB with supernova (SN) association demand a more detailed classification of the GRB population. In this {\it Letter}, we focus on GRBs associated with KNe, believed to be originating from mergers of binaries involving neutron stars (NS). We make use of the GRB prompt emission light curves of {\it Swift}-BAT 2022 GRB catalog and employ machine learning algorithms to study the classification of GRB progenitors. Our analysis reveals that there are five distinct clusters of GRBs, of which the KN-associated GRBs are located in two separate clusters indicating they may have been produced by different progenitors. We argue that these clusters may be due to subclasses of binary neutron star (BNS) and/or neutron star–black hole (NS-BH) mergers. We also discuss the implications of these findings for future gravitational-wave (GW) observations and how those observations may help in understanding these clusters better.

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D. Dimple, K. Misra and K. Arun
Wed, 26 Apr 23
51/62

Comments: Submitted to ApjL after addressing reviewer’s comments

Type-II Majoron Dark Matter [CL]

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http://arxiv.org/abs/2304.12527


We discuss in detail the possibility that the “type-II majoron” — that is, the pseudo Nambu-Goldstone boson that arises in the context of the type-II seesaw mechanism if the lepton number is spontaneously broken by an additional singlet scalar — account for the dark matter (DM) observed in the universe. We study the requirements the model’s parameters have to fulfill in order to reproduce the measured DM relic abundance through two possible production mechanisms in the early universe, freeze-in and misalignment, both during a standard radiation-dominated era and early matter domination. We then study possible signals of type-II majoron DM and the present and expected constraints on the parameter space that can be obtained from cosmological observations, direct detection experiments, and present and future searches for decaying DM at neutrino telescopes and cosmic-ray experiments. We find that — depending on the majoron mass, the production mechanism, and the value of the vacuum expectation value of the type-II triplet — all of the three decay modes (photons, electrons, neutrinos) of majoron DM particles can yield observable signals at future indirect searches for DM. Furthermore, in a corner of the parameter space, detection of majoron DM is possible through electron recoil at running and future direct detection experiments.

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C. Biggio, L. Calibbi, T. Ota, et. al.
Wed, 26 Apr 23
52/62

Comments: 22 pages + appendices and bibliography, 6 figures

Constraints on the $e^{\pm }$ Pair Injection of Pulsar Halos: Implications from the Galactic Diffuse Multi-TeV Gamma-ray Emission [HEAP]

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http://arxiv.org/abs/2304.12574


Diffuse gamma-ray emission (DGE) has been discovered over the Galactic disk in the energy range from sub-GeV to sub-PeV. While it is believed to be dominated by the pionic emission of cosmic ray (CR) hadrons via interactions with interstellar medium, unresolved gamma-ray sources may also be potential contributors. TeV gamma-ray halos around middle-aged pulsars have been proposed as such sources. Their contribution to DGE, however, highly depends on the injection rate of electrons and the injection spectral shape, which are not well determined based on current observations. The measured fluxes of DGE can thus provide constraints on the $e^\pm$ injection of the pulsar halo population in turn. In this paper, we estimate the contribution of pulsar halos to DGE based on the ATNF pulsar samples with taking into account the off-beamed pulsars. The recent measurement on DGE by Tibet AS$\gamma$ and an early measurement by MILAGRO are used to constrain the pair injection parameters of the pulsar halo population. Our result may be used to distinguish different models for pulsar halos.

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K. Yan and R. Liu
Wed, 26 Apr 23
53/62

Comments: 18 pages, 8 figures, 1 table. Accepted for publication in Physical Review D

Study of the bipolar jet of the YSO Th 28 with VLT/SINFONI: Jet morphology and H$_2$ emission [SSA]

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http://arxiv.org/abs/2304.12974


$Context.$ The YSO Th 28 possesses a highly collimated jet, which clearly exhibits an asymmetric brightness of its jet lobes at optical and NIR wavelengths. There may be asymmetry in the jet plasma parameters in opposite jet lobes (e.g. electron density, temperature, and outflow velocity). $Aims.$ We examined the Th 28 jet in a 3″x3″ where the jet material is collimated and accelerated. Our goal is to map the morphology and determine its physical parameters to determine the physical origin of such asymmetries. $Methods.$ We present $JHK$-spectra of Th 28 obtained with the SINFONI on the (VLT, ESO) in June-July 2015. $Results.$ The [Fe II] emission originates in collimated jet lobes. Two new axial knots are detected at 1″ in the blue lobe and 1″.2 in the red lobe. The H$_2$ radiation is emitted from an extended region with a radius of $\gtrsim270$ au, which is perpendicular to the jet. The PV diagrams of the bright H$_2$ lines reveal faint H$_2$ emission along both jet lobes as well. The compact and faint H I emission (Pa$\beta$ and Br$\gamma$) comes from two regions, namely from a spherical region around the star and from the jet lobes. The size of the jet launching region is derived as 0″.015 ($\sim$3 au at 185 pc), and the initial opening angle of the Th 28 jet is $\sim28^0$, which makes this jet substantially less collimated than most jets from other CTTs. $Conclusions.$ The emission in [Fe II], H$_2$, and H I lines suggests a morphology in which the ionised gas in the disc appears to be disrupted by the jet. The resolved disc-like H$_2$ emission most likely arises in the disc atmosphere from shocks caused by a radial uncollimated wind. The asymmetry of the [Fe II] photocentre shifts with respect to the jet source arises in the immediate vicinity of the driving source of Th28 and suggests that the observed brightness asymmetry is intrinsic as well.

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S. Melnikov, P. Boley, N. Nikonova, et. al.
Wed, 26 Apr 23
60/62

Comments: 18 pages, 14 figures

Progenitor constraint with circumstellar material for the magnetar-hosting supernova remnant RCW 103 [HEAP]

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http://arxiv.org/abs/2304.11819


Stellar winds blown out from massive stars ($\gtrsim 10M_{\odot}$) contain precious information on the progenitor itself, and in this context, the most important elements are carbon (C), nitrogen (N), and oxygen (O), which are produced by the CNO cycle in the H-burning layer. Although their X-ray fluorescence lines are expected to be detected in swept-up shock-heated circumstellar materials (CSMs) in supernova remnants (SNRs), particularly those of C and N have been difficult to detect so far. Here, we present a high-resolution spectroscopy of a young magnetar-hosting SNR RCW~103 with the Reflection Grating Spectrometer (RGS) onboard XMM-Newton and report on the detection of \ion{N}{7} Ly$\alpha$ (0.50~keV) line for the first time. By comparing the obtained abundance ratio of N to O (N/O$=3.8 \pm{0.1}$) with various stellar evolution models, we show that the progenitor of RCW~103 is likely to have a low-mass (10–12~$M_{\odot}$) and medium-rotation velocities ($\lesssim 100~\rm{km~s^{-1}}$). The results also rule out the possibility of dynamo effects in massive ($\geq35~M_{\odot}$) stars as a formation mechanism of the associated magnetar 1E~161348$-$5055. Our method is useful for estimating various progenitor parameters for future missions with microcalorimeters such as XRISM and Athena.

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T. Narita, H. Uchida, T. Yoshida, et. al.
Tue, 25 Apr 23
4/72

Comments: Accepted for publication in ApJ. 11 pages, 8 figures

Constraining the onset density for the QCD phase transition with the neutrino signal from core-collapse supernovae [HEAP]

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http://arxiv.org/abs/2304.12316


The occurrence of a first-order hadron-quark matter phase transition at high baryon densities is investigated in astrophysical simulations of core-collapse supernovae, to decipher yet incompletely understood properties of the dense matter equation of state using neutrinos from such cosmic events. It is found that the emission of a non-standard second neutrino burst, dominated by electron-antineutrinos, is not only a measurable signal for the appearance of deconfined quark matter but also reveals information about the state of matter at extreme conditions encountered at the supernova interior. To this end, a large set of spherically symmetric supernova models is investigated, studying the dependence on the equation of state and on the stellar progenitor. General relativistic neutrino-radiation hydrodynamics is employed featuring three-flavor Boltzmann neutrino transport and a microscopic hadron-quark hybrid matter equation of state class, that covers a representative range of parameters. This facilitates the direct connection between intrinsic signatures of the neutrino signal and properties of the equation of state. In particular, a set of novel relations have been found empirically. These potentially provide a constraint for the onset density of a possible QCD phase transition, which is presently one of the largest uncertainties in modern investigations of the QCD phase diagram, from the future neutrino observation of the next galactic core-collapse supernova.

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N. Largani, T. Fischer and N. Bastian
Tue, 25 Apr 23
10/72

Comments: 14 pages, 5 figures

Shimmering gravitons in the gamma-ray sky [HEAP]

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http://arxiv.org/abs/2304.11222


What is the highest energy at which gravitons can be observed? We address this question by studying graviton-to-photon conversion – the inverse-Gertsenshtein effect – in the magnetic field of the Milky Way. We find that above $\sim 1~\mbox{PeV}$ the effective photon mass grows large enough to quench the conversion rate. The induced photon flux is comparable to the sensitivity of LHAASO to a diffuse $\gamma$-ray background, but only for graviton abundances of order $\Omega_{\text{gw}} h^2_0 \sim 1$. In the future, owing to a better understanding of $\gamma$-ray backgrounds, larger effective areas and longer observation times, sub-PeV shimmering gravitons with a realistic abundance of $\Omega_{\text{gw}} h^2_0 \sim 0.01$ could be detected. We show that this is achieved in a cosmologically-motivated scenario of post-recombination superheavy dark matter decay. Therefore, the sub-PeV range might be the ultimate energy frontier at which gravitons can be observed.

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S. Ramazanov, R. Samanta, G. Trenkler, et. al.
Tue, 25 Apr 23
14/72

Comments: 16 pages, 2 figures

Multi-messenger signals of heavy axionlike particles in core-collapse supernovae: two-dimensional simulations [HEAP]

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http://arxiv.org/abs/2304.11360


Core-collapse supernovae are a useful laboratory to probe the nature of exotic particles. If axionlike particles (ALPs) are produced in supernovae, they can affect the transfer of energy and leave traces in observational signatures. In this work, we develop two-dimensional supernova models including the effects of the production and the absorption of ALPs that couple with photons. It is found that the additional heating induced by ALPs can enhance the explosion energy E_exp; for moderate ALP-photon coupling, we find explosion energies ~0.610^51 erg compared to our reference model without ALPs of ~0.410^51 erg. Our findings also indicate that when the coupling constant is sufficiently high, the neutrino luminosities and mean energies are decreased because of the additional cooling of the proto-neutron star. The gravitational wave strain is also reduced because the mass accretion on the proto-neutron star is suppressed. Although the ALP-photon coupling can foster explodability, including enhancing the explosion energy closer to recent observations, more long-term simulations in spatially three-dimension are needed to draw robust conclusions.

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K. Mori, T. Takiwaki, K. Kotake, et. al.
Tue, 25 Apr 23
20/72

Comments: 11 pages, 8 figures, submitted to PRD

Hydrodynamic Evolution of Sgr A East: The Imprint of A Supernova Remnant in the Galactic Center [HEAP]

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http://arxiv.org/abs/2304.11296


We perform three-dimensional numerical simulations to study the hydrodynamic evolution of Sgr A East, the only known supernova remnant (SNR) in the center of our Galaxy, to infer its debated progenitor SN type and its potential impact on the Galactic center environment. Three sets of simulations are performed, each of which represents a represent a certain type of SN explosion (SN Iax, SN Ia or core-collapse SN) expanding against a nuclear outflow of hot gas driven by massive stars, whose thermodynamical properties have been well established by previous work and fixed in the simulations. All three simulations can simultaneously roughly reproduce the extent of Sgr A East and the position and morphology of an arc-shaped thermal X-ray feature, known as the “ridge”. Confirming previous work, our simulations show that the ridge is the manifestation of a strong collision between the expanding SN ejecta and the nuclear outflow. The simulation of the core-collapse SN, with an assumed explosion energy of 5×10^50 erg and an ejecta mass of 10 M_sun, can well match the X-ray flux of the ridge, whereas the simulations of the SN Iax and SN Ia explosions underpredict its X-ray emission, due to a smaller ejecta mass. All three simulations constrain the age of Sgr A East to be <1500 yr and predict that the ridge should fade out over the next few hundred years. We address the implications of these results for our understanding of the Galactic center environment.

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M. Zhang, Z. Li and Z. Morris
Tue, 25 Apr 23
22/72

Comments: 21 pages, 18 figures. Accepted for publication on MNRAS

Colour-Flavour Locked Quark Stars in Light of the Compact Object in HESS J1731-347 and the GW190814 Event [HEAP]

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http://arxiv.org/abs/2304.12209


The central compact object within HESS J1731- 347 possesses unique mass and radius properties that renders it a compelling candidate for a self-bound star. In this research, we examine the capability of quark stars composed of colour superconducting quark matter to explain the latter object by using its marginalised posterior distribution and imposing it as a constraint on the relevant parameter space. Namely, we investigate quark matter for $N_f=2,3$ in the colour superconducting phase, incorporating perturbative QCD corrections, and we derive their properties accordingly. The utilised thermodynamic potential of this work possesses an MIT bag model formalism with the parameters being established as flavour-independent. In this instance, we conclude the favour of 3-flavour over 2-flavour colour superconducting quark matter, isolating our interest on the former. The parameter space is further confined due to the additional requirement for a high maximum mass ($M_{\text{TOV}} \geq 2.6 M_{\odot}$), accounting for GW$190814$’s secondary companion. We pay a significant attention on the speed of sound and the trace anomaly (proposed as a measure of conformality [\href{https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.252702}{10.1103/PhysRevLett.129.252702}]). We conclude that it is possible for colour-flavour locked quark stars to reach high masses without violating the conformal bound or the $\langle \Theta \rangle {\mu_B} \geq 0$ if the quartic coefficient value $\alpha_4$ does not exceed an upper limit which is solely dependent on the established $M{\text{TOV}}$. For $M_{\text{TOV}}=2.6 M_{\odot}$, we find that the limit reads $\alpha_4 \leq 0.594$. Lastly, a further study takes place on the agreement of colour-flavour locked quark stars with additional astrophysical objects including the GW$170817$ and GW$190425$ events, followed by a relevant discussion.

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P. Oikonomou and C. Moustakidis
Tue, 25 Apr 23
25/72

Comments: 13 pages, 10 figures, 1 table

Constraints on the Galactic Centre environment from \textit{Gaia} hypervelocity stars III: Insights on a possible companion to Sgr A* [GA]

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http://arxiv.org/abs/2304.12169


We consider a scenario in which Sgr A* is in a massive black hole binary (MBHB) with an as-of-yet undetected supermassive or intermediate-mass black hole companion. Dynamical encounters between this MBHB and single stars in its immediate vicinity would eject hypervelocity stars (HVSs) with velocities beyond the Galactic escape velocity. In this work, we use existing HVS observations to constrain for the first time the existence of a companion to Sgr A*. We simulate the ejection of HVSs via the `MBHB slingshot’ scenario and show that the population of HVSs detectable today depends strongly on the companion mass and the separation of the MBHB. We demonstrate that the lack of uncontroversial HVS candidates in \textit{Gaia} Data Release 3 places a firm upper limit on the mass of a possible Sgr A* companion. Within one milliparsec of Sgr A*, our results exclude a companion more massive than $1000 \, \mathrm{M_\odot}$. If Sgr A* recently merged with a companion black hole, our findings indicate that unless this companion was less massive than $500 \, \mathrm{M_\odot}$, this merger must have occurred at least $10$ Myr ago. These results complement and improve upon existing independent constraints on a companion to Sgr A* and show that large regions of its parameter space can now be ruled out.

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F. Evans, A. Rasskazov, A. Remmelzwaal, et. al.
Tue, 25 Apr 23
26/72

Comments: Submitted to MNRAS. 16 pages, 9 figures. Comments welcome

First Detection of the Powerful Gamma Ray Burst GRB221009A by the THEMIS ESA and SST particle detectors on October 9, 2022 [HEAP]

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http://arxiv.org/abs/2304.11225


We present the first results study of the effects of the powerful Gamma Ray Burst GRB 221009A that occurred on October 9, 2022, and was serendipitously recorded by electron and proton detectors aboard the four spacecraft of the NASA THEMIS mission. Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars, and, among them, GRB 221009A is so far the brightest burst ever observed due to its enormous energy ($E_{\gamma iso}\sim10^{55}$ erg) and proximity (the redshift is $z\sim 0.1505$). The THEMIS mission launched in 2008 was designed to study the plasma processes in the Earth’s magnetosphere and the solar wind. The particle flux measurements from the two inner magnetosphere THEMIS probes THA and THE and ARTEMIS spacecraft THB and THC orbiting the Moon captured the dynamics of GRB 221009A with a high-time resolution of more than 20 measurements per second. This allowed us to resolve the fine structure of the gamma-ray burst and determine the temporal scales of the two main bursts spiky structure complementing the results from gamma-ray space telescopes and detectors.

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O. Agapitov, M. Balikhin, A. Hull, et. al.
Tue, 25 Apr 23
28/72

Comments: N/A

Statistical study of a large and cleaned sample of ultraluminous and hyperluminous X-ray sources [HEAP]

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http://arxiv.org/abs/2304.11216


Ultra-/hyperluminous X-ray sources (ULX/HLX) could be interesting laboratories to further improve our understanding of the supermassive black hole growth through super-Eddington accretion episodes and successive mergers of lighter holes. ULXs are thought to be powered by super-Eddington accretion onto stellar-mass compact objects, while HLXs may be accreting intermediate mass black holes (IMBH). However, a significant portion of the sample of ULX/HLX candidates derived from catalogue searches are background AGN. Here we build ULX and HLX samples from recent XMM-Newton, Swift-XRT and Chandra catalogues and the GLADE catalogue of galaxies. We aim to characterise the frequency, environment, hardness and variability of ULXs and HLXs to better assess their differences and understand their populations. After a thorough classification of these X-ray sources, we remove 42% of $S/N>3$ sources shown to be contaminants, to obtain the cleanest sample of ULX/HLX to date. From a sample of 1342 ULXs and 191 HLXs, we study the occupation fraction, hardness, variability, radial distribution and preferred environment of the sources. We build their Malmquist-corrected X-ray luminosity functions (XLF) and compare them with previous studies. We statistically compare ULXs and HLXs and assess the differences in their nature. The interpretation of HLXs as IMBHs is investigated. A significant break is seen in the XLF at $\sim 10^{40}$ erg/s. Our ULX sample, having $\leq 2$% of contaminants, confirms that ULXs are located preferentially in spiral galaxies and galaxies with higher star-formation rates. Unlike ULXs, HLXs seem to reside equally in spiral and lenticular/elliptical galaxies. 35% of the HLX candidates have an optical counterpart, and we estimate the mass of 120 of them in the range of $2000-10^5 M_\odot$. Most HLXs are consistent with an accreting massive black hole in a dwarf galaxy satellite.

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H. Tranin, N. Webb and O. Godet
Tue, 25 Apr 23
33/72

Comments: 27 pages, 24 figures, accepted in A&A

The origin of long soft lags and the nature of the hard-intermediate state in black hole binaries [HEAP]

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http://arxiv.org/abs/2304.12003


Fast variability of the X-ray corona in black hole binaries can produce a soft lag by reverberation, where the reprocessed thermalized disc photons lag behind the illuminating hard X-rays. This lag is small, and systematically decreases with increasing mass accretion rate towards the hard-soft transition, consistent with a decreasing truncation radius between the thin disc and X-ray hot inner flow. However, the soft lag suddenly increases dramatically just before the spectrum becomes disc-dominated (hard-intermediate state). Interpreting this as reverberation requires that the X-ray source distance from the disc increases dramatically, potentially consistent with switching to X-rays produced in the radio jet. However, this change in lag behaviour occurs without any clear change in hard X-ray spectrum, and before the plasmoid ejection event which might produce such a source (soft-intermediate state). Instead, we show how the soft lag can be interpreted in the context of propagation lags from mass accretion rate fluctuations. These normally produce hard lags, as the model has radial stratification, with fluctuations from larger radii modulating the harder spectra produced at smaller radii. However, all that is required to switch the sign is that the hottest Comptonized emission has seed photons which allow it to extend down in energy below the softer emission from the slower variable turbulent region from the inner edge of the disc. Our model connects the timing change to the spectral change, and gives a smooth transition of the X-ray source properties from the bright hard state to the disc-dominated states.

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T. Kawamura, C. Done and T. Takahashi
Tue, 25 Apr 23
34/72

Comments: 7 pages, 7 figures, submitted to MNRAS

Terzina on board NUSES: a pathfinder for EAS Cherenkov Light Detection from space [IMA]

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http://arxiv.org/abs/2304.11992


In this paper we introduce the Terzina telescope as a part of the NUSES space mission. This telescope aims to detect Ultra High Energy Cosmic Rays (UHECRs) through the Cherenkov light emission from the extensive air showers (EAS) that they create in the Earth’s atmosphere. The Cherenkov photons are aligned along the shower axis inside about $\sim 0.2-1^{\circ}$, so that they become detectable by Terzina when it points towards the Earth’s limb. A sun-synchronous orbit will allow the telescope to observe only the night side of the Earth’s atmosphere. In this contribution, we focus on the description of the telescope detection goals, geometry, optical design and its photon detection camera composed of Silicon Photo-Multipliers (SiPMs). Moreover, we describe the full Monte Carlo simulation chain developed to estimate Terzina’s performance for UHECR detection. The estimate of the radiation damage and light background rates, the readout electronics and trigger logic are briefly described. Terzina will be able to study the potential for future physics missions devoted to UHECR detection and to UHE neutrino astronomy. It is a pathfinder for missions like POEMMA or future constellations of similar satellites to NUSES.

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L. Burmistrov
Tue, 25 Apr 23
37/72

Comments: N/A

Key Science Goals for the Next-Generation Event Horizon Telescope [HEAP]

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http://arxiv.org/abs/2304.11188


The Event Horizon Telescope (EHT) has led to the first images of a supermassive black hole, revealing the central compact objects in the elliptical galaxy M87 and the Milky Way. Proposed upgrades to this array through the next-generation EHT (ngEHT) program would sharply improve the angular resolution, dynamic range, and temporal coverage of the existing EHT observations. These improvements will uniquely enable a wealth of transformative new discoveries related to black hole science, extending from event-horizon-scale studies of strong gravity to studies of explosive transients to the cosmological growth and influence of supermassive black holes. Here, we present the key science goals for the ngEHT and their associated instrument requirements, both of which have been formulated through a multi-year international effort involving hundreds of scientists worldwide.

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M. Johnson, K. Akiyama, L. Blackburn, et. al.
Tue, 25 Apr 23
41/72

Comments: 32 pages, 11 figures, accepted for publication in a special issue of Galaxies on the ngEHT (this https URL)

Gravitational-Wave Phasing of Compact Binary Systems to the Fourth-and-a-Half post-Newtonian Order [CL]

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http://arxiv.org/abs/2304.11185


The inspiral phase of gravitational waves emitted by spinless compact binary systems is derived through the fourth-and-a-half post-Newtonian (4.5PN) order beyond quadrupole radiation, and the leading amplitude mode ($\ell$, m) = (2, 2) is obtained at 4PN order. We also provide the radiated flux, as well as the phase in the stationary phase approximation. Rough numerical estimates for the contribution of each PN order are provided for typical systems observed by current and future gravitational wave detectors.

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L. Blanchet, G. Faye, Q. Henry, et. al.
Tue, 25 Apr 23
47/72

Comments: 9 pages, 1 table

Improving the Composition of Ultra High Energy Cosmic Rays with Ground Detector Data [HEAP]

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http://arxiv.org/abs/2304.11197


We show that the maximum shower depth ($X_{\rm max}$) distributions of Ultra-High Energy Cosmic Rays (UHECRs), as measured by fluorescence telescopes, can be augmented by building a mapping to observables collected by surface detectors. Using the publicly available data on “golden hybrid” events from the Pierre Auger Observatory we demonstrate significant correlations between $X_{\rm max}$ and timing information from ground Cherenkov detectors. Using such a mapping we show how to incorporate a subset of ground data into the inference of the $X_{\rm max}$ distribution, where the size of this subset depends on the strength of the correlation found. With a simple linear fit model, we are able to effectively incorporate $\sim13\%$ of all ground data statistics. Finally, we use this augmented dataset to infer the composition of UHECRs and discriminate between hadronic models used in air shower development simulations, and show the results improve significantly due to the effectively larger statistics available.

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B. Bortolato, J. Kamenik and M. Tammaro
Tue, 25 Apr 23
52/72

Comments: 8 pages, 7 figures

The Northern Cross Fast Radio Burst project — III. The FRB-magnetar connection in a sample of nearby galaxies [HEAP]

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http://arxiv.org/abs/2304.11179


Fast radio bursts (FRBs) are millisecond-radio transients observed at cosmological distances. The nature of their progenitors is still under debate, although magnetars are invoked by most models. The FRB-magnetar connection was strengthened by the discovery of an FRB-like event from the Galactic magnetar SGR J1935+215. In this work, we aim to investigate how prevalent are magnetars like SGR~J1935+2154 within FRB progenitors. We carried out an FRB search in a sample of seven nearby (< 12 Mpc) galaxies with the Northern Cross radio telescope for a total of 692 h. We detected one 1.8~ms burst in the direction of M101 with fluence of $58 \pm 5$ Jy ms. Its dispersion measure of 303 pc cm$^{-3}$ places it most-likely beyond M101. Considering no significant detection coming indisputably from the selected galaxies, we place a 38 yr$^{-1}$ upper limit on the total – i.e., including the whole sample – burst rate at the 95\% confidence level. This upper limit constrains $\lambda_{\rm mag} < 0.42$~magnetar$^{-1}$ yr$^{-1}$ or, if combined with literature observations of a similar sample of nearby galaxies, it yields a joint constraint of $\lambda_{\rm mag} < 0.25$ magnetar$^{-1}$ yr$^{-1}$. We also provide the first constraints on the expected rate of FRBs hypothetically originating from ultraluminous X-ray (ULX) sources, since some of the galaxies observed during our observational campaign host confirmed ULXs. We obtain $< 13$ yr$^{-1}$ per ULX on the total sample of galaxies observed. Our results indicate that bursts with energies $E > 10^{34}$ erg from magnetars like SGR~J1935+2154 appear more rare compared to previous observations, and further disfavours them as unique progenitors for the cosmological FRB population, leaving more space open to the contribution from a population of more exotic magnetars, not born via core-collapsed supernovae.

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D. Pelliciari, G. Bernardi, M. Pilia, et. al.
Tue, 25 Apr 23
53/72

Comments: 9 pages, 4 figures, submitted to A&A

Massive black holes in galactic nuclei: Theory and Simulations [HEAP]

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http://arxiv.org/abs/2304.11541


Massive black holes are fundamental constituents of our cosmos, from the Big Bang to today. Understanding their formation from cosmic dawn, their growth, and the emergence of the first, rare quasars in the early Universe remains one of our greatest theoretical and observational challenges. Hydrodynamic cosmological simulations self-consistently combine the processes of structure formation at cosmological scales with the physics of smaller, galaxy scales. They capture our most realistic understanding of massive black holes and their connection to galaxy formation and have become the primary avenue for theoretical research in this field. The space-based gravitational wave interferometer, LISA, will open up new investigations into the dynamical processes involving massive black holes. Multi-messenger astrophysics brings new exciting prospects for tracing the origin, growth and merger history of massive black holes across cosmic ages.

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T. Matteo, D. Angles-Alcazar and F. Shankar
Tue, 25 Apr 23
59/72

Comments: 77 pages, 20 figures, This chapter is the preprint of the version currently in production. Please cite this chapter as the following: T.DiMatteo, D. Angles-Alcazar, and F. Shankar. Massive black holes in galactic nuclei: Theory and simulations, in The Encyclopedia of Cosmology (Set 2): Black Holes, edited by Z. Haiman (World Scientific, New Jersey, 2023)

Timing analysis of Swift J0243.6+6124 with NICER and Fermi/GBM during the decay phase of the 2017-2018 outburst [HEAP]

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http://arxiv.org/abs/2304.11937


We present a timing and noise analysis of the Be/X-ray binary system Swift J0243.6+6124 during its 2017-2018 super-Eddington outburst using NICER/XTI observations. For the initial segments of the data that overlap with the Fermi/GBM pulse frequency history, we apply a synthetic pulse timing analysis to enrich the spin frequency history of the source. In addition, we employ phase-coherent timing analysis for NICER/XTI observations that extends beyond the Fermi/GBM frequency history. We show that the pulse profiles switch from double-peaked to single-peaked when the X-ray luminosity drops below $\sim$$7\times 10^{36}$ erg s$^{-1}$. We suggest that this transitional luminosity is associated with the transition from a pencil beam pattern to a hybrid beam pattern when the Coulomb interactions become ineffective to decelerate the accretion flow, which implies a dipolar magnetic field strength of $\sim$$5\times 10^{12}$ G. We also obtained the power density spectra (PDS) of the spin frequency derivative fluctuations. The red noise component of the PDS is found to be steeper ($\omega^{-3.36}$) than the other transient accreting sources. We find significantly high noise strength estimates above the super-Eddington luminosity levels, which may arise from the torque fluctuations due to interactions with the quadrupole fields at such levels.

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M. Serim, &. Dönmez, D. Serim, et. al.
Tue, 25 Apr 23
61/72

Comments: 18 pages, 7 figures. Submitted to MNRAS

General-Relativistic Hydrodynamics Simulation of a Neutron Star – Sub-Solar-Mass Black Hole Merger [CL]

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http://arxiv.org/abs/2304.11642


Over the last few years, there has been an increasing interest in sub-solar mass black holes due to their potential to provide valuable information about cosmology or the black hole population. Motivated by this, we study observable phenomena connected to the merger of a sub-solar mass black hole with a neutron star. For this purpose, we perform new numerical-relativity simulations of a binary system composed of a black hole with mass $0.5M_\odot$ and a neutron star with mass $1.4 M_\odot$. We investigate the merger dynamics of this exotic system and provide information about the connected gravitational-wave and kilonova signals. Our study indicates that current gravitational-waveform models are unable to adequately describe such systems and that phenomenological relations connecting the binary parameters with the ejecta and remnant properties are not applicable to our system. Furthermore, we find a dependence of the kilonova signal on the azimuthal viewing angle due to the asymmetric mass ejection. This first-of-its-kind simulation opens the door for the study of sub-solar mass black hole – neutron star mergers and could serve as a testing ground for future model development.

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I. Markin, A. Neuweiler, A. Abac, et. al.
Tue, 25 Apr 23
67/72

Comments: 16 pages, 14 figures, to be submitted to PRD, comments welcome

A Cross-correlation Study between IceCube Neutrino Events and the Fermi Unresolved Gamma-ray Sky [HEAP]

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http://arxiv.org/abs/2304.10934


With the coincident detections of electromagnetic radiation together with gravitational waves (GW170817) or neutrinos (TXS 0506+056), the new era of multimessenger astrophysics has begun. Of particular interest are the searches for correlation between the high-energy astrophysical neutrinos detected by the IceCube Observatory and gamma-ray photons detected by the Fermi Large Area Telescope (LAT). So far, only sources detected by the LAT have been considered in correlation with IceCube neutrinos, neglecting any emission from sources too faint to be resolved individually. Here, we present the first cross-correlation analysis considering the unresolved gamma-ray background (UGRB) and IceCube events. We perform a thorough sensitivity study and, given the lack of identified correlation, we place upper limits on the fraction of the observed neutrinos that would be produced in proton-proton (p-p) or proton-gamma (p-gamma) interactions from the population of sources contributing to the UGRB emission and dominating its spatial anisotropy (aka blazars). Our analysis suggests that, under the assumption that there is no intrinsic cutoff and/or hardening of the spectrum above Fermi-LAT energies, and that all gamma-rays from the unresolved blazars dominating the UGRB fluctuation field are produced by neutral pions from p-p (p-gamma) interactions, up to 60% (30%) of such population may contribute to the total neutrino events observed by IceCube. This translates into a O(1%) maximum contribution to the astrophysical high-energy neutrino flux observed by IceCube at 100 TeV.

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M. Negro, M. Crnogorčević, E. Burns, et. al.
Mon, 24 Apr 23
1/41

Comments: This version is submitted to ApJ

Potential of Constraining Propagation Parameters of Galactic Cosmic Rays with the High Energy cosmic-Radiation Detection facility onboard China's Space Station [HEAP]

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http://arxiv.org/abs/2304.11036


Precise measurements of the spectra of secondary and primary cosmic rays are crucial for understanding the origin and propagation of those energetic particles. The High Energy cosmic-Radiation Detection (HERD) facility onboard China`s Space Station, which is expected to operate in 2027, will push the direct measurements of cosmic ray fluxes precisely up to PeV energies. In this work, we investigate the potential of HERD on studying the propagation of cosmic rays using the measurements of boron, carbon, and oxygen spectra. We find that, compared with the current results, the new HERD measurements can improve the accuracy of the propagation parameters by 8\% to 40\%. The constraints on the injection spectra at high energies will also be improved.

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Z. Xu, Q. Yuan, Z. Tang, et. al.
Mon, 24 Apr 23
4/41

Comments: 10 pages, 4 figures

Detectability of Late-time Supernova Neutrinos with Fallback Accretion onto Protoneutron star [HEAP]

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http://arxiv.org/abs/2304.11150


We investigate the late-time neutrino emission powered by fallback mass accretion onto proto-neutron star (PNS), using neutrino radiation-hydrodynamic simulations with full Boltzmann neutrino transport. We follow the time evolution of accretion flow onto PNS until the system reaches a steady state. A standing shock wave is commonly formed in the accretion flow, whereas the shock radius varies depending on mass accretion rate and PNS mass. A sharp increase in temperature emerges in the vicinity of PNS ($\sim 10$ km), which characterizes neutrino emission. Both neutrino luminosity and average energy become higher with increasing mass accretion rate and PNS mass. The mean energy of emitted neutrinos is in the range of $10\lesssim\epsilon\lesssim20\,\mathrm{MeV}$, which is higher than that estimated from PNS cooling models ($\lesssim10\,\mathrm{MeV}$). Assuming a distance to core-collapse supernova of $10\,\mathrm{kpc}$, we quantify neutrino event rates for Super-Kamiokande (Super-K) and DUNE. The estimated detection rates are well above the background, and their energy-dependent features are qualitatively different from those expected from PNS cooling models. Another notable feature is that the neutrino emission is strongly flavor dependent, exhibiting that the neutrino event rate hinges on the neutrino oscillation model. We estimate them in the case with adiabatic Mikheev-Smirnov-Wolfenstein model, and show that the normal- and inverted mass hierarchy offer the large number of neutrino detection in Super-K and DUNE, respectively. Hence the simultaneous observation with Super-K and DUNE of the fallback neutrinos will provide a strong constraint on neutrino mass hierarchy.

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R. Akaho, H. Nagakura and T. Foglizzo
Mon, 24 Apr 23
6/41

Comments: submitted to ApJ

Optical Emission Model for Binary Black Hole Merger Remnants Travelling through Discs of Active Galactic Nucleus [HEAP]

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http://arxiv.org/abs/2304.10567


Active galactic nuclei (AGNs) have been proposed as plausible sites hosting a sizable fraction of the binary black hole (BBH) mergers measured through gravitational waves (GWs) by the LIGO-Virgo-Kagra (LVK) experiment. These GWs could be accompanied by radiation feedback due to the interaction of the BBH merger remnant with the AGN disc. We present a new predicted radiation signature driven by the passage of a kicked BBH remnant throughout a thin AGN disc. We analyse the situation of a merger occurring outside the thin disc, where the merger is of second or higher generation in a merging hierarchical sequence. The coalescence produces a kicked BH remnant that eventually plunges into the disc, accretes material, and inflates jet cocoons. We consider the case of a jet cocoon propagating quasi-parallel to the disc plane and study the outflow that results when the cocoon emerges from the disc. Here we focus on the long time-scale emission produced after the disc outflow expands and becomes optically thin. The bolometric luminosity of such disc outflow evolves as $L\propto t^{-7/2}$. Depending on the parameter configuration, the flare produced by the disc outflow could be comparable to or exceed the AGN background emission at near-infrared, optical, and extreme ultraviolet wavelengths appearing $\sim$[20-500] days after the GW event and lasting for $\sim$[1-200] days, accordingly.

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J. Rodríguez-Ramírez, C. Bom, B. Fraga, et. al.
Mon, 24 Apr 23
8/41

Comments: 11 pages, 8 figures. Submitted to MNRAS

The spin-down accretion regime of Galactic ultra-luminous X-ray pulsar Swift J0243.6+6124 [HEAP]

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http://arxiv.org/abs/2304.10815


The relative high fluxes of the Galactic ultra-luminous X-ray pulsar Swift J0243 allow a detailed study of its spin-down regime in quiescence state, for a first time. After the 2017 giant outburst, its spin frequencies show a linear decreasing trend with some variations due to minor outbursts. The linear spin-down rate is $\sim-1.9\times10^{-12}$ Hz/s during the period of lowest luminosity, from which one can infer a dipole field $\sim1.75\times10^{13}$ G. The $\dot{\nu}-L$ relation during the spin-down regime is complex, and the $\dot{\nu}$ is close to 0 when the luminosity reaches both the high end ($L_{38}\sim0.3$) and the lowest value ($L_{38}\sim0.03$). The luminosity of zero-torque is different for the giant outburst and other minor outbursts. It is likely due to different accretion flows for different types of outburst, as evidenced by the differences of the spectra and pulse profiles at a similar luminosity for different types of outburst (giant or not). The pulse profile changes from double peaks in the spin-up state to a single broad peak in the low spin-down regime, indicating the emission beam/region is larger in the low spin-down regime. These results show that accretion is still ongoing in the low spin-down regime for which the neutron star is supposed to be in a propeller state.

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J. Liu, L. Ji and M. Ge
Mon, 24 Apr 23
9/41

Comments: 7 pages, 7 figs, to appear in ApJ, comments welcome

X-ray radiative transfer in full 3D with SKIRT [HEAP]

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http://arxiv.org/abs/2304.10563


Models of active galactic nuclei (AGN) suggest that their circumnuclear media are complex with clumps and filaments, while recent observations hint towards polar extended structures of gas and dust, as opposed to the classical torus paradigm. The X-ray band forms an interesting window to study these circumnuclear media in great detail. In this work, we extended the radiative transfer code SKIRT with the X-ray processes that govern the broadband X-ray spectra of obscured AGN, to study the structure of AGN circumnuclear media in full 3D, based on their reflected X-ray emission. We extended the SKIRT code with Compton scattering on free electrons, photo-absorption and fluorescence by cold atomic gas, scattering on bound electrons, and extinction by dust. This includes a novel treatment of extreme-forward scattering by dust, and a detailed description of anomalous Rayleigh scattering. To verify our X-ray implementation, we performed the first dedicated benchmark of X-ray torus models, comparing five X-ray radiative transfer codes. Finally, we illustrated the 3D nature of the code by producing synthetic X-ray images and spectra of clumpy torus models. SKIRT forms a powerful new tool to model AGN circumnuclear media in full 3D from X-ray to millimetre wavelengths, and is now publicly available. In the X-ray regime, we find an excellent agreement with the simulation results of the MYTorus and RefleX codes, which validates our X-ray implementation. We find some discrepancies with other codes, which motivates the need for a robust framework that can handle non-linear 3D radiative transfer effects. The new X-ray functionalities of the SKIRT code allow for uncomplicated access to a broad suite of 3D X-ray models for AGN that can easily be tested and modified. This will be particularly useful with the advent of X-ray microcalorimeter observations.

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B. Meulen, P. Camps, M. Stalevski, et. al.
Mon, 24 Apr 23
12/41

Comments: 20 pages, 20 figures, accepted for publication in Astronomy & Astrophysics

Neutron star phase transition as the origin for the fast radio bursts and soft gamma-ray repeaters of SGR J1935+2154 [HEAP]

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http://arxiv.org/abs/2304.10871


Magnetars are believed as neutron stars (NSs) with strong magnetic fields. X-ray flares and fast radio bursts (FRBs) have been observed from the magnetar (soft gamma-ray repeater, SGR J1935+2154). We propose that the phase transition of the NS can power the FRBs and SGRs.Based on the equation of state provided by the MIT bag model and the mean field approximation, we solve the Tolman-Oppenheimer-Volkoff equations to get the NS structure. With spin-down of the NS, the hadronic shell gradually transfers to the quark shell.The gravitational potential energy released by one time of the phase transition can be achieved. The released energy, time interval between two successive phase transitions, and glitch are all consistent with the observations of the FRBs and the X-ray flares from SGR J1935+2154. We conclude that the phase transition of an NS is a plausible mechanism to power the SGRs as well as the repeating FRBs.

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J. Shen, Y. Zou, S. Yang, et. al.
Mon, 24 Apr 23
13/41

Comments: 11 pages, 3 figures

The Host Galaxies of Sub-Chandrasekhar Mass Type Ia Supernovae [CEA]

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http://arxiv.org/abs/2304.10601


In recent years, there has been ample evidence for the existence of multiple progenitor pathways that can result in Type Ia supernova (SNe Ia), including SNe Ia of sub-Chandrasekhar mass origin best distinguished by their redder colors and higher Si II velocities near peak brightness. These SNe can contaminate the population of normal events used for cosmological analyses, creating unwanted biases in the final analyses. Given that many current and future surveys using SNe Ia as cosmological probes will not have the resources to take a spectrum of all the events, likely only getting host redshifts long after the SNe Ia have faded, we need to turn to methods that could separate these populations based purely on photometry or host properties. Here, we present a study of a sample of well observed, nearby SNe Ia and their hosts to determine if there are significant enough difference between these populations that can be discerned only from the stellar population properties of their hosts. Our results indicate that the global host properties, including star formation, stellar mass, stellar population age, and dust attenuation, of sub-Chandrasekhar mass explosions do not differ significantly from those of normal mass origin. However, we do find evidence using Na I D equivalent widths that the local environments of sub-Chandrasekhar mass explosions are more dust-affected than normal SNe Ia. Future work requires strengthening photometric probes of sub-Chandrasekhar SNe and their local environments to distinguish these events.

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A. Nugent, A. Polin and P. Nugent
Mon, 24 Apr 23
16/41

Comments: 16 pages, 10 figures, 2 tables, submitted

The Magnetohydrodynamic-Particle-In-Cell Module in Athena++: Implementation and Code Tests [HEAP]

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http://arxiv.org/abs/2304.10568


We present a new magnetohydrodynamic-particle-in-cell (MHD-PIC) code integrated into the Athena++ framework. It treats energetic particles as in conventional PIC codes while the rest of thermal plasmas are treated as background fluid described by MHD, thus primarily targeting at multi-scale astrophysical problems involving the kinetic physics of the cosmic-rays (CRs). The code is optimized toward efficient vectorization in interpolation and particle deposits, with excellent parallel scaling. The code is also compatible with static/adaptive mesh refinement, with dynamic load balancing to further enhance multi-scale simulations. In addition, we have implemented a compressing/expanding box framework which allows adiabatic driving of CR pressure anisotropy, as well as the $\delta f$ method that can dramatically reduce Poisson noise in problems where distribution function $f$ is only expected to slightly deviate from the background. The code performance is demonstrated over a series of benchmark test problems including particle acceleration in non-relativistic parallel shocks. In particular, we reproduce the linear growth of the CR gyro-resonant (streaming and pressure anisotropy) instabilities, under both the periodic and expanding/compressing box setting. We anticipate the code to open up the avenue for a wide range of astrophysical and plasma physics applications.

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X. Sun and X. Bai
Mon, 24 Apr 23
18/41

Comments: 20 pages, 19 figures, submitted to MNRAS

Particle-in-Cell Simulations of Relativistic Magnetic Reconnection with Advanced Maxwell Solver Algorithms [HEAP]

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http://arxiv.org/abs/2304.10566


Relativistic magnetic reconnection is a non-ideal plasma process that is a source of non-thermal particle acceleration in many high-energy astrophysical systems. Particle-in-cell (PIC) methods are commonly used for simulating reconnection from first principles. While much progress has been made in understanding the physics of reconnection, especially in 2D, the adoption of advanced algorithms and numerical techniques for efficiently modeling such systems has been limited. With the GPU-accelerated PIC code WarpX, we explore the accuracy and potential performance benefits of two advanced Maxwell solver algorithms: a non-standard finite difference scheme (CKC) and an ultrahigh-order pseudo-spectral method (PSATD). We find that for the relativistic reconnection problem, CKC and PSATD qualitatively and quantitatively match the standard Yee-grid finite-difference method. CKC and PSATD both admit a time step that is 40% longer than Yee, resulting in a ~40% faster time to solution for CKC, but no performance benefit for PSATD when using a current deposition scheme that satisfies Gauss’s law. Relaxing this constraint maintains accuracy and yields a 30% speedup. Unlike Yee and CKC, PSATD is numerically stable at any time step, allowing for a larger time step than with the finite-difference methods. We found that increasing the time step 2.4-3 times over the standard Yee step still yields accurate results, but only translates to modest performance improvements over CKC due to the current deposition scheme used with PSATD. Further optimization of this scheme will likely improve the effective performance of PSATD.

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H. Klion, R. Jambunathan, M. Rowan, et. al.
Mon, 24 Apr 23
22/41

Comments: 19 pages, 10 figures. Submitted to ApJ

Optical color of Type Ib and Ic supernovae and implications for their progenitors [SSA]

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http://arxiv.org/abs/2304.10670


Type Ib and Ic supernovae (SNe Ib/Ic) originate from hydrogen-deficient massive star progenitors, of which the exact properties are still much debated. Using the SN data in the literature, we investigate the optical $B-V$ color of SNe Ib/Ic at the $V-$band peak and show that SNe Ib are systematically bluer than SNe Ic. We construct SN models from helium-rich and helium-poor progenitors of various masses using the radiation hydrodynamics code STELLA and discuss how the $B-V$ color at the $V-$band peak is affected by $^{56}$Ni to ejecta mass ratios, $^{56}$Ni mixing and presence/absence of the helium envelope. We argue that the dichotomy in the amounts of helium in the progenitors plays the primary role in making the observed systematic color difference at the optical peak, in favor of the most commonly invoked SN scenario that SNe Ib and SNe Ic progenitors are helium-rich and helium-poor, respectively.

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H. Jin, S. Yoon and S. Blinnikov
Mon, 24 Apr 23
24/41

Comments: Accepted for publication in ApJ. 16 pages

Flares from merged magnetars: their prospects as a new population of gamma-ray counterparts of binary neutron star mergers [HEAP]

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http://arxiv.org/abs/2304.10715


Long-lived massive magnetars are expected to be remnants of some binary neutron star (BNS) mergers. In this paper, we argue that the magnetic powered flaring activities of these merged magnetars would occur dominantly in their early millisecond-period-spin phase, which is in the timescale of days. Such flares endure significant absorption by the ejecta from the BNS collision, and their detectable energy range is from 0.1-10 MeV, in a time-lag of $\sim$ days after the merger events indicated by the gravitational wave chirps. We estimate the rate of such flares in different energy ranges, and find that there could have been ~0.1-10 cases detected by Fermi/GBM. A careful search for $\sim10$ milliseconds spin period modulation in weak short gamma-ray bursts (GRBs) may identify them from the archival data. Future MeV detectors can detect them at a rate from a few to tens per year. The recent report on the Quasi-Period-Oscillation found in two BASTE GRBs should not be considered as cases of such flares, for they were detection in a lower energy range and with a much shorter period spin modulation.

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S. Yi, Z. Zhang and X. Wang
Mon, 24 Apr 23
25/41

Comments: 10 pages, 5 figures, submitted to ApJL

Effects of large-scale magnetic fields on the observed composition of ultra high-energy cosmic rays [HEAP]

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http://arxiv.org/abs/2304.10688


Ultra high-energy (UHE) cosmic rays (CRs) from distant sources interact with intergalactic radiation fields, leading to their spallation and attenuation. They are also deflected in intergalactic magnetic fields (IGMFs), particularly those associated with Mpc-scale structures. These deflections extend the propagation times of CR particles, forming a magnetic horizon for each CR species. The cumulative cooling and interactions of a CR ensemble also modifies their spectral shape and composition observed on Earth. We construct a transport formulation to calculate the observed UHE CR spectral composition for 4 classes of source population. The effects on CR propagation brought about by IGMFs are modeled as scattering processes during transport, by centers associated with cosmic filaments. Our calculations demonstrate that IGMFs can have a marked effect on observed UHE CRs, and that source population models are degenerate with IGMF properties. Interpretation of observations, including the endorsement or rejection of any particular source classes, thus needs careful consideration of the structural properties and evolution of IGMFs. Future observations providing tighter constraints on IGMF properties will significantly improve confidence in assessing UHE CR sources and their intrinsic CR production properties.

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E. Owen, Q. Han and K. Wu
Mon, 24 Apr 23
32/41

Comments: 10 pages, 5 figures, 2 tables. Accepted for publication in Phys. Rev. D

Multi-epoch hard X-ray view of Compton-thick AGN Circinus Galaxy [GA]

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http://arxiv.org/abs/2304.10972


The circumnuclear material around Active Galactic Nuclei (AGN) is one of the essential components of the obscuration-based unification model. However, our understanding of the circumnuclear material in terms of its geometrical shape, structure and its dependence on accretion rate is still debated. In this paper, we present the multi-epoch broadband X-ray spectral modelling of a nearby Compton-thick AGN in Circinus galaxy. We utilise all the available hard X-ray ($> 10$ keV) observations taken from different telescopes, $i.e.,$ $BeppoSAX$, $Suzaku$, $NuSTAR$ and $AstroSat$, at ten different epochs across $22$ years from $1998$ to $2020$. The $3.0-79$ keV broadband X-ray spectral modelling using physically-motivated models, namely MYTORUS, BORUS02 and UXCLUMPY, infers the presence of a torus with a low covering factor of $0.28$, an inclination angle of $77^{\circ}$ $-$ $81^{\circ}$ and Compton-thick line-of-sight column densities ($N_{\rm H,LOS} = 4.13~-~9.26~\times~10^{24}$ cm$^{-2}$) in all the epochs. The joint multi-epoch spectral modelling suggests that the overall structure of the torus is likely to remain unchanged. However, we find tentative evidence for the variable line-of-sight column density on timescales ranging from one day to one week to a few years, suggesting a clumpy circumnuclear material located at sub-parsec to tens of parsec scales.

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A. Kayal, V. Singh, C. Ricci, et. al.
Mon, 24 Apr 23
35/41

Comments: 18 pages, 7 figures, 6 tables, accepted for publication in Monthly Notices of the Royal Astronomical Society

Transient jet ejections associated with limit-cycle behaviors in the very high state of black hole binaries [HEAP]

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http://arxiv.org/abs/2304.10847


Ejection mechanism of transient relativistic jets from black hole binaries is studied. Based on the observations of the limit-cycle behaviors of the superluminal jet source, GRS 1915+105, we infer that the transient jet ejections could happen just after the slim disk emerging from the standard disk at some distance runs over the standard disk and reaches the vicinity of the central black hole. The standard disk releases about a half of the gravitational energy in the course of the accretion, but the released radiative energy could be absorbed by the optically thick slim disk covering the standard disk in this situation. Then, since the inward motion of the slim disk is much faster than that of the standard disk, a quantity of energy released by an amount of gas in the standard disk is received by the much smaller amount of gas in the slim disk. As the result, the energy per mass received by the slim disk is expected to be largely amplified and is estimated to get highly relativistic. Since the energy is much larger than the gravitational energy, the height of the slim disk could significantly increase. Hence, the innermost part of the slim disk from which almost all the angular momentum has been transferred outward could have a much larger height than the black hole size and collide with one another around the central axis of the disk, turning to an outward flow along the axis normal to the disk plane. The flow in this direction can be approximated to be that through the de Laval nozzle and could become supersonic near the distance where the flow has the smallest cross section.

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H. Inoue
Mon, 24 Apr 23
39/41

Comments: accepted to PASJ

Global Electron Thermodynamics in Radiatively Inefficient Accretion Flows [HEAP]

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http://arxiv.org/abs/2304.10684


In the collisionless plasmas of radiatively inefficient accretion flows, heating and acceleration of ions and electrons is not well understood. Recent studies in the gyrokinetic limit revealed the importance of incorporating both the compressive and Alfvenic cascades when calculating the partition of dissipated energy between the plasma species. In this paper, we use a covariant analytic model of the accretion flow to explore the impact of compressive and Alfvenic heating, Coulomb collisions, compressional heating, and radiative cooling on the radial temperature profiles of ions and electrons. We show that, independent of the partition of heat between the plasma species, even a small fraction of turbulent energy dissipated to the electrons makes their temperature scale with a virial profile and the ion-to-electron temperature ratio smaller than in the case of pure Coulomb heating. In contrast, the presence of compressive cascades makes this ratio larger because compressive turbulent energy is channeled primarily into the ions. We calculate the ion-to-electron temperature in the inner accretion flow for a broad range of plasma properties, mass accretion rates, and black hole spins and show that it ranges between $5 \lesssim T_i/T_e \lesssim 40$. We provide a physically motivated expression for this ratio that can be used to calculate observables from simulations of black hole accretion flows for a wide range of conditions.

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K. Satapathy, D. Psaltis and F. Ozel
Mon, 24 Apr 23
41/41

Comments: N/A

Muons in EASs with $E_0 = 10^{19}$ eV according to data of the Yakutsk Array [HEAP]

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http://arxiv.org/abs/2304.09924


Lateral distribution functions of particles in extensive air showers with the energy $E_0 \simeq 10^{19}$ eV recorded by ground-based and underground scintillation detectors with a threshold of $E_{\mu} \simeq 1.0 \times \sec\theta$ GeV at the Yakutsk array during the continuous observations from 1986 to 2016 have been analyzed using events with zenith angles $\theta \le 60^{\circ}$ functions have been compared to the predictions obtained with the QGSJet01 hadron interaction model by applying the CORSIKA code. The entire dataset indicates that cosmic rays consist predominantly of protons.

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A. Glushkov, K. Lebedev and A. Sabourov
Fri, 21 Apr 23
3/60

Comments: 11 pages, 5 figures, 2 tables. Accepted for publication in JETP Letters (v.117, no.4, 2023), minor typos fixed

Massive black holes in galactic nuclei: Observations [HEAP]

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http://arxiv.org/abs/2304.10233


Since a black hole does not emit light from its interior, nor does it have a surface on which light from nearby sources can be reflected, observational study of black hole physics requires observing the gravitational impact of the black hole on its surroundings. A massive black hole leaves a dynamical imprint on stars and gas close by. Gas in the immediate vicinity of an accreting massive black hole can, due to the presence of the black hole, shine so brightly that it outshines the light of the billions of stars in its host galaxy and be detected across the Universe. By observing the emission from stars and gas and determining their kinematics scientists can extract vital information not only on the fundamental properties of the black holes themselves but also the impact they have on their surroundings. As it turns out, supermassive black holes appear to play a vital role in shaping the Universe as we know it, as they can profoundly impact the star formation history in galaxies. As a consequence, these black holes indirectly impact the cosmic build up of chemical elements heavier than Helium and thus affect when and where life can form. For these reasons alone, observations of massive black holes constitute a very active research area of modern astrophysics.
In this chapter we aim to provide a general overview — fit for a non-expert — of what scientists have learned, and hope to learn, from analyzing observations of massive black holes and the material around them.

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M. Vestergaard and K. Gültekin
Fri, 21 Apr 23
13/60

Comments: This chapter is the pre-print of the version currently in production. Please cite this chapter as the following: M. Vestergaard and K. G\”ultekin. “Massive black holes in galactic nuclei: observations,” in The Encyclopedia of Cosmology (Set 2): Black Holes, edited by Z. Haiman (World Scientific, New Jersey, 2023). 77 pages, 21 figures

3D spectroscopy with GTC-MEGARA of the triple AGN candidate in SDSS J102700.40+174900.8 [GA]

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http://arxiv.org/abs/2304.09968


Triple AGN systems are expected to be the result of the hierarchical model of galaxy formation. Since there are very few of them confirmed as such, we present the results of a new study of the triple-AGN candidate SDSS J102700.40+174900.8 (center nucleus) through observations with $\it{GTC}$-$\it{MEGARA}$ Integral Field Unit. 1D and 2D analysis of the line ratios of the three nuclei allow us to locate them in the EW(H$\alpha$) vs. [Nii] /H$\alpha$ diagram. The central nucleus is found to be a retired galaxy (or fake AGN). The neighbors are found to be a strong AGN (southeastern nucleus, J102700.55+174900.2) compatible with a Sy2 galaxy, and a weak AGN (northern nucleus, J102700.38+174902.6) compatible with a LINER2. We find evidence that the neighbors constitute a dual AGN system (Sy2-LINER2) with a projected separation of 3.98 kpc in the optical bands. The H$\alpha$ velocity map shows that the northern nucleus has an H$\alpha$ emission with a velocity offset of $\sim$-500 km s$^{-1}$, whereas the southeastern nucleus has a rotating disk and H$\alpha$ extended emission at kpc scales. Chandra archival data confirm that the neighbors have X-ray (0.5-2) keV and (2-7) keV emission, whereas the center nucleus shows no X-ray emission. A collisional ring with knots is observed in the HST images of the southeastern nucleus. These knots coincide with star formation regions that along with the ring are predicted in a head-on collision. In this case, the morphology changes are probably due to a minor merger that was produced by the passing of the northern through the southeastern nucleus.

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E. Benítez, H. Ibarra-Medel, C. Negrete, et. al.
Fri, 21 Apr 23
17/60

Comments: Accepted for publication in ApJ, 20 pages, 9 figures, 7 tables

Detection of millihertz quasi-periodic oscillations in the low-mass X-ray binary 4U 1730–22 with NICER [HEAP]

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http://arxiv.org/abs/2304.09935


We report the discovery of millihertz quasi-periodic oscillations (mHz QPOs) from the neutron star (NS) low-mass X-ray binary 4U 1730–22 using the Neutron Star Interior Composition Explorer (NICER). After being inactive for almost 50 years, 4U 1730–22 went into outburst twice between June and August 2021, and between February and July 2022. We analyse all the NICER observations of this source, and detect mHz QPOs with a significance > $4\sigma$ in 35 observations. The QPO frequency of the full data set ranged between ~4.5 and ~8.1 mHz with an average fractional rms amplitude of the order of ~2%. The X-ray colour analysis strongly suggests that 4U 1730–22 was in a soft spectral state during the QPO detections. Our findings are consistent with those reported for other sources where the mHz QPOs have been interpreted as the result of a special mode of He burning on the NS surface called marginally stable nuclear burning (MSNB). We conclude that the mHz QPOs reported in this work are also associated with the MSNB, making 4U 1730–22 the eighth source that shows this phenomenology. We discuss our findings in the context of the heat flux from the NS crust.

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G. Mancuso, D. Altamirano, P. Bult, et. al.
Fri, 21 Apr 23
18/60

Comments: 9 pages, 6 figures. Accepted for publication in MNRAS

A Superluminous Supernova Lightened by Collisions with Pulsational Pair-instability Shells [HEAP]

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http://arxiv.org/abs/2304.10416


Superluminous supernovae are among the most energetic stellar explosions in the Universe, but their energy sources remain an open question. Here we present long-term observations of one of the closest examples of the hydrogen-poor subclass (SLSNe-I), SN~2017egm, revealing the most complicated known luminosity evolution of SLSNe-I. Three distinct post-peak bumps were recorded in its light curve collected at about $100$–350\,days after maximum brightness, challenging current popular power models such as magnetar, fallback accretion, and interaction between ejecta and a circumstellar shell. However, the complex light curve can be well modelled by successive interactions with multiple circumstellar shells with a total mass of about $6.8$–7.7\,M$\odot$. In this scenario, large energy deposition from interaction-induced reverse shocks results in ionization of neutral oxygen in the supernova ejecta and hence a much lower nebular-phase line ratio of [O\,\textsc{i}] $\lambda6300$/([Ca\,\textsc{ii}] + [O\,\textsc{ii}]) $\lambda7300$ ($\sim 0.2$) compared with that derived for other superluminous and normal stripped-envelope SNe. The pre-existing multiple shells indicate that the progenitor of SN~2017egm experienced pulsational mass ejections triggered by pair instability within 2 years before explosion, in robust agreement with theoretical predictions for a pre-pulsation helium-core mass of 48–51\,M${\odot}$.

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W. Lin, X. Wang, L. Yan, et. al.
Fri, 21 Apr 23
21/60

Comments: 34 pages, 13 figures, 6 tables

GSpyNetTree: A signal-vs-glitch classifier for gravitational-wave event candidates [CL]

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http://arxiv.org/abs/2304.09977


Despite achieving sensitivities capable of detecting the extremely small amplitude of gravitational waves (GWs), LIGO and Virgo detector data contain frequent bursts of non-Gaussian transient noise, commonly known as ‘glitches’. Glitches come in various time-frequency morphologies, and they are particularly challenging when they mimic the form of real GWs. Given the higher expected event rate in the next observing run (O4), LIGO-Virgo GW event candidate validation will require increased levels of automation. Gravity Spy, a machine learning tool that successfully classified common types of LIGO and Virgo glitches in previous observing runs, has the potential to be restructured as a signal-vs-glitch classifier to accurately distinguish between glitches and GW signals. A signal-vs-glitch classifier used for automation must be robust and compatible with a broad array of background noise, new sources of glitches, and the likely occurrence of overlapping glitches and GWs. We present GSpyNetTree, the Gravity Spy Convolutional Neural Network Decision Tree: a multi-CNN classifier using CNNs in a decision tree sorted via total GW candidate mass tested under these realistic O4-era scenarios.

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S. Alvarez-Lopez, A. Liyanage, J. Ding, et. al.
Fri, 21 Apr 23
23/60

Comments: 19 pages, 12 figures, submitted to Classical and Quantum Gravity

No evidence for p- or d-wave dark matter annihilation from local large-scale structure [CEA]

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http://arxiv.org/abs/2304.10301


If dark matter annihilates into standard model particles with a cross-section which is velocity dependent, then Local Group dwarf galaxies will not be the best place to search for the resulting gamma ray emission. A greater flux would be produced by more distant and massive halos, with larger velocity dispersions. We construct full-sky predictions for the gamma-ray emission from galaxy- and cluster-mass halos within $\sim 200 \, {\mathrm{Mpc}}$ using a suite of constrained $N$-body simulations (CSiBORG) based on the Bayesian Origin Reconstruction from Galaxies algorithm. Comparing to observations from the Fermi Large Area Telescope and marginalising over reconstruction uncertainties and other astrophysical contributions to the flux, we obtain constraints on the cross-section which are two (seven) orders of magnitude tighter than those obtained from dwarf spheroidals for $p$-wave ($d$-wave) annihilation. We find no evidence for either type of annihilation from dark matter particles with masses in the range $m_\chi = 2-500 \, {\mathrm{GeV}}/c^2$, for any channel. As an example, for annihilations producing bottom quarks with $m_\chi = 10 \, {\mathrm{GeV}}/c^2$, we find $a_{1} < 2.4 \times 10^{-21} \, {\mathrm{cm^3 s^{-1}}}$ and $a_{2} < 3.0 \times 10^{-18} \, {\mathrm{cm^3 s^{-1}}}$ at 95% confidence, where the product of the cross-section, $\sigma$, and relative particle velocity, $v$, is given by $\sigma v = a_\ell (v/c)^{2\ell}$ and $\ell=1, 2$ for $p$-, $d$-wave annihilation, respectively. Our bounds, although failing to exclude the thermal relic cross-section for velocity-dependent annihilation channels, are among the tightest to date.

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A. Kostić, D. Bartlett and H. Desmond
Fri, 21 Apr 23
26/60

Comments: 15 pages, 5 figures; submitted to Physical Review D

Black holes in classical general relativity and beyond [CL]

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http://arxiv.org/abs/2304.09984


The Kerr-Newman metric is the unique vacuum solution of the General Relativistic field equations, in which any singularities or spacetime pathologies are hidden behind horizons. They are believed to describe the spacetimes of massive astrophysical objects with no surfaces, which we call black holes. This spacetime, which is defined entirely by the mass, spin, and charge of the black hole, gives rise to a variety of phenomena in the motion of particles and photons outside the horizons that have no Newtonian counterparts. Moreover, the Kerr-Newman spacetime remains remarkably resilient to many attempts in modifying the underlying theory of gravity. The monitoring of stellar orbits around supermassive black holes, the detection of gravitational waves from the coalescence of stellar-mass black holes, and the observation of black-hole shadows in images with horizon-scale resolution, all of which have become possible during the last decade, are offering valuable tools in testing quantitatively the predictions of this remarkable solution to Einstein’s equations.

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D. Psaltis
Fri, 21 Apr 23
35/60

Comments: This chapter is the pre-print of the version currently in production. Please cite this chapter as the following: D. Psaltis. “Black holes in classical general relativity and beyond” in The Encyclopedia of Cosmology (Set 2): Black Holes, edited by Z. Haiman (World Scientific, New Jersey, 2023)

Early-time spectroscopic modelling of the transitional Type Ia Supernova 2021rhu with TARDIS [HEAP]

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http://arxiv.org/abs/2304.10129


An open question in SN Ia research is where the boundary lies between ‘normal’ Type Ia supernovae (SNe Ia) that are used in cosmological measurements and those that sit off the Phillips relation. We present the spectroscopic modelling of one such ’86G-like’ transitional SN Ia, SN 2021rhu, that has recently been employed as a local Hubble Constant calibrator using a tip of the red-giant branch measurement. We detail its modelling from -12 d until maximum brightness using the radiative-transfer spectral-synthesis code tardis. We base our modelling on literature delayed-detonation and deflagration models of Chandrasekhar mass white dwarfs, as well as the double-detonation models of sub-Chandrasekhar mass white dwarfs. We present a new method for ‘projecting’ abundance profiles to different density profiles for ease of computation. Due to the small velocity extent and low outer densities of the W7 profile, we find it inadequate to reproduce the evolution of SN 2021rhu as it fails to match the high-velocity calcium components. The host extinction of SN 2021rhu is uncertain but we use modelling with and without an extinction correction to set lower and upper limits on the abundances of individual species. Comparing these limits to literature models we conclude that the spectral evolution of SN 2021rhu is also incompatible with double-detonation scenarios, lying more in line with those resulting from the delayed detonation mechanism (although there are some discrepancies, in particular a larger titanium abundance in SN 2021rhu compared to the literature). This suggests that SN 2021rhu is likely a lower luminosity, and hence lower temperature, version of a normal SN Ia.

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L. Harvey, K. Maguire, M. Magee, et. al.
Fri, 21 Apr 23
40/60

Comments: Comments: 25 pages, 22 figures, accepted for publication in MNRAS

Localization of binary neutron star mergers with a single Cosmic Explorer [HEAP]

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http://arxiv.org/abs/2304.09889


Next-generation ground-based gravitational-wave detectors, such as Cosmic Explorer (CE), are expected to be sensitive to gravitational-wave signals with frequencies as low as 5 Hz, allowing signals to spend a significant amount of time in the detector frequency band. As a result, the effects caused by the rotation of the Earth become increasingly important for such signals. Additionally, the length of the arms of these detectors can be comparable to the wavelength of detectable gravitational waves, which introduces frequency-dependent effects that are not significant in current-generation detectors. These effects are expected to improve the ability to localize compact binary coalescences in the sky even when using only one detector. This study aims to understand how much these effects can help in localization. We present the first comprehensive Bayesian parameter estimation framework that accounts for all these effects using \textsc{Bilby}, a commonly used Bayesian parameter estimation tool. We focus on sky localization constraints for binary neutron star events with an optimal signal-to-noise ratio of 1000 with one detector at the projected CE sensitivity. We find that these effects help localize sources using one detector with sky areas as low as 10 square degrees. Moreover, we explore and discuss how ignoring these effects in the parameter estimation can lead to biases in the inference.

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P. Baral, S. Morisaki, I. Hernandez, et. al.
Fri, 21 Apr 23
41/60

Comments: N/A

Probing primordial black holes from a first order phase transition through pulsar timing and gravitational wave signals [CL]

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http://arxiv.org/abs/2304.10084


In this work, we assess the sensitivity reach of pulsar timing array (PTA) measurements to probe pointlike primordial black holes (PBHs), with an extended mass distribution, which originate from collapsed Fermi balls that are formed through the aggregation of asymmetric U(1) dark fermions trapped within false vacuum bubbles during a dark first order phase transition (FOPT). The PBH formation scenario is mainly characterized by the dark asymmetry, strength of the FOPT, rate of FOPT, and the percolation temperature. Meanwhile, for PBH masses of interest lying within $10^{-10} M_\odot – 10^{-3}M_\odot$, the relevant signal for PTA measurements is the Doppler phase shift in the timing signal, due to the velocity change induced by transiting PBHs on pulsars. Taking the dark asymmetry parameter to be $10^{-4}$ and $10^{-5}$, we find that percolation temperatures within the 0.1-10 keV range, FOPT rates above $10^3$ times the Hubble parameter at percolation, and FOPT strengths within $10^{-6}-0.1$ can give rise to PBHs that can be probed by an SKA-like PTA observation. On the other hand, the accompanying gravitational wave (GW) signal from the FOPT can be used as a complementary probe, assuming that the peak frequency lies within the $\mathcal{O}(10^{-9})-\mathcal{O}(10^{-6})$ Hz range, and the peak GW abundance is above the peak-integrated sensitivity curves associated with pulsar timing observations that search for stochastic GWs. At the fundamental level, a quartic effective potential for a dark scalar field can trigger the FOPT. By performing a parameter scan, we obtained the class of effective potentials that lead to FOPT scenarios that can be probed by SKA through pulsar timing and GW observations.

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J. Acuña and P. Tseng
Fri, 21 Apr 23
43/60

Comments: 40 pages, 8 figures

The Challenge of Eccentricity when Observing Stellar-mass Binary Black Holes with Space-Based Gravitational Wave Detectors [HEAP]

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http://arxiv.org/abs/2304.10340


Eccentricity is a smoking gun for the formation channel of stellar-mass binary black holes (sBBHs). Space-based gravitational wave observatories can determine binary eccentricity to $e_0\gtrsim\mathcal{O}(10^{-4}) $, but the detection of these systems can be very challenging. A targeted search of archival data triggered by ground-based detectors shrinks the search range thus making the task tractable. Previous studies ignored the effect of eccentricity. For the first time, we constructed a template bank for space-borne gravitational wave detectors that includes the impact of eccentricity. We find that even for a mild upper limit of $0.1$, the inclusion of eccentricity can still boost the template bank size by five orders of magnitudes. Our work marked a solid step towards the detection of a realistic sBBH, and it demonstrated that with the appropriate extension, the template bank method can still identify the early inspiral of sBBHs.

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H. Wang, I. Harry, A. Nitz, et. al.
Fri, 21 Apr 23
44/60

Comments: 7 pages, 3 figures, comments welcome

Hard TeV Gamma-Ray Afterglows of Nearby GRB 190829A as a Tentative Signature of Ultra-High-Energy Cosmic Rays Accelerated in Gamma-Ray Burst Jets [HEAP]

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http://arxiv.org/abs/2304.10188


The observed hard TeV gamma-ray spectrum of the nearby gamma-ray burst (GRB) 190829A may challenge the conventional leptonic GRB afterglow model. It has been proposed that an ultra-high-energy (UHE; $\varepsilon^{‘}{\rm p}\sim 10^{20}$ eV) proton population can be pre-accelerated by internal shocks in GRB jets. We study possible signatures of the UHE protons embedded in the TeV afterglows when they escape the afterglow fireball. We show that the leptonic model can represent the observed multiwavelength lightcurves and spectral energy distributions of GRB 190829A by considering the uncertainties of the model parameters. Attributing the TeV gamma-ray afterglows to the emission of both the electron self-Compton scattering process and the UHE proton synchrotron radiations in the afterglow fireball, we obtain tentative upper limits of $\log{10} \varepsilon_{\rm p}^{\prime}/{\rm eV}\sim 20.46$ and $\log_{10}E_{\rm p, total}/{\rm erg}\leq 50.75$, where $E_{\rm p, total}$ is the total energy of the proton population. The synchrotron radiations of the UHE protons should dominate the early TeV gamma-ray afterglows, implying that early observations are critical for revealing the UHE proton population.

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J. Huang, X. Huang, J. Cheng, et. al.
Fri, 21 Apr 23
51/60

Comments: 9 pages, 4 figures, Accepted for Publication in ApJ

The Detection of a Compact Radio Feature in a Seyfert Galaxy After an Accretion Rate Change [GA]

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http://arxiv.org/abs/2304.10125


X-ray binaries are known to show state transitions related to accretion rate changes which are often accompanied with dramatic changes in the jet emission. However, it is not clear whether this characteristics of stellar-mass black hole systems can be scaled up to the accretion disk of active galactic nuclei. The Seyfert 1 galaxy, KUG 1141+371 has been showing a steadily increasing X-ray flux since 2007, and exhibited variability behaviour similar to the state transitions observed in X-ray binaries. It was hypothesised to undergo a rapid boost of mass accretion. If the X-ray binary analogy holds then the appearance of jet emission can also be expected in KUG 1141+371. While the source was not detected in the Faint Images of the Radio Sky at Twenty-centimeters in 1994, it appears in the VLA Sky Survey in 2019 and at 22 GHz in a VLA observation in 2018 at mJy flux density level. Our VLBI observations revealed a compact, flat-spectrum radio feature. Its high brightness temperature indicates the radio emission originates from an AGN.

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K. Gabányi, K. Smith, S. Frey, et. al.
Fri, 21 Apr 23
54/60

Comments: 5 pages, 2 figures; to appear in the proceedings of the 15th European VLBI Network Symposium and Users’ Meeting (EVN2022), 11-15 July 2022, University College Cork, Ireland

Testing the first law of black hole mechanics with gravitational waves [CL]

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http://arxiv.org/abs/2304.10117


GW191219_163120 is a gravitational wave signal that is believed to have originated from a neutron star-black hole (NSBH) coalescence with an extreme mass ratio. In this work, we use data of GW191219_163120 from LIGO and Virgo to test the first law of black hole mechanics by considering the neutron star as a perturbation to the black hole before the merger, and the remnant black hole as a stationary black hole after the merger. Our results demonstrate consistency with the first law of black hole mechanics, with an error level of about 6\% at 68\% credibility and 10\% at 95\% credibility. We also find that the higher the mass ratio of the gravitational wave source, the more consistent our results are with the first law of black hole mechanics. Overall, our study sheds light on the nature of NSBH coalescences and their implications for black hole mechanics.

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C. Wang and F. Shu
Fri, 21 Apr 23
55/60

Comments: 5 pages, 4 figures, 2 tables

Steep Balmer decrement in weak AGNs may be not caused by dust extinction: clues from low-luminosity AGNs and changing-look AGNs [GA]

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http://arxiv.org/abs/2304.09435


The hydrogen Balmer decrement (e.g., $\rm H\alpha/H\beta$) is widely adopted as an indicator of the internal reddening of active galactic nuclei (AGNs). This is challenged by some low-luminosity AGNs (LLAGNs) and changing-look AGNs (CLAGNs), which have steep Balmer decrement but without strong evidence for absorption. We compile a sample of normal AGNs and CLAGNs with a wider distribution of bolometric Eddington ratio ($\lambda_{\rm Edd}=L_{\rm bol}/L_{\rm Edd}$) and find a strong negative correlation between $\rm H\alpha/H\beta$ and $\lambda_{\rm Edd}$, which suggests that the Balmer decrement is also accretion-rate dependent. We further explore the Balmer decrement based on the photoionization model using the Cloudy code by considering spectral energy distribution (SED) from the accretion disk with different accretion rates (e.g., disk/corona and truncated disk at high and low Eddington ratios, respectively). Both the standard disk and truncated disk predict a negative correlation of $\rm H\alpha/H\beta-\lambda_{\rm Edd}$, where the relation is steeper in the case of the truncated disk. The negative correlations are also explored in two single CLAGNs. The measured negative correlation of $\rm H\alpha/H\beta$ — $\lambda_{\rm Edd}$ is mainly caused by the lower responsivity $({\rm dlog}L_{\rm line}/{\rm dlog}L_{\rm cont})$ in $\rm H\alpha$ relative to that in $\rm H\beta$, due to the larger optical depth in the former. We propose that the steep Balmer decrements in low-Eddington-ratio AGNs (e.g., some Seyferts 1.5-1.9 and CLAGNs) are not simply caused by absorption but mainly caused by the relatively low flux of ionizing photons.

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J. Wu, Q. Wu, H. Xue, et. al.
Thu, 20 Apr 23
15/57

Comments: 13 pages, 3 figures, Accepted for publication in The Astrophysical Journal

Neutron Stars on Modified Teleparallel Gravity [CL]

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http://arxiv.org/abs/2301.06432


We investigate compact objects in modified teleparallel gravity with realistic equations of state. We propose a modification on Teleparallel Equivalent of General Relativity, then an appropriate tetrad is applied on the field equations. A specific set of relations showing a equivalency between our gravitational model and the New General Relativity is found. The conservation equation implies that our Tolman-Oppenheimer-Volkoff equations are presented with an effective pressure and energy density, where a free parameter \b{eta}3 is used to construct them. Numerical analysis using realistic equations of state is made, the behavior of mass, radius and the relation mass-radius as functions of \b{eta}3 is also investigated.

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S. Vilhena, S. Duarte, M. Dutra, et. al.
Thu, 20 Apr 23
17/57

Comments: 8 pages, 5 figures

Nustar observation of the binary system 4U 0114+65 [HEAP]

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http://arxiv.org/abs/2304.09295


The high mass X-ray binary system 4U 0114+65 was observed by Nustar in October 2019, and by XMM-Newton in August 2015. Here we performed spectral and timing analysis of the Nustar observation, and carry out timing analysis on the XMM-Newton data. We measured the spin period of the neutron star from both observations and found a spin-up rate $\dot{p} = 1.54 \pm 0.38 \times 10^{-6} s s^{-1}$. During the Nustar observation two flares occured, one occured shortly after the start of the observation and the other near the end separated by a long period of low/quiescent- state. The large and sudden flares mostly resulted from accretion of Corotating Interaction Region (CIR) material. A common spectral model to HMXBs, powerlaw with high energy cutoff and absorption at low energy, gave a good fit to both flaring and quiescent states. A flourescent iron line was not required in fitting any of the states. On the other hand, very tentative evidence of Cyclotron Resonant Scattering Feature (CRSF) at $\sim$ 17 keV was found during fitting using cyclabs model, however fitting improvement was not significant enough to confirm its detection, plus a very narrow width (< 1 keV) was obtained for the line and its first harmonic. Visual inspection of the spectra showed a deficiency of emission near the expected first and second harmonic. Another important feature visually noticed in the spectra is the presence of hard tail above 50 keV. This could be explained by the shocked material bounding the CIR.

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M. Abdallah, R. Samir, D. Leahy, et. al.
Thu, 20 Apr 23
21/57

Comments: N/A

The spin and mass ratio affects the gravitational waveforms of binary black hole mergers with a total system mass of 12-130 $\rm{M}_\odot$ [HEAP]

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http://arxiv.org/abs/2304.09396


Analyzing the observations obtained by the LIGO and the Virgo Collaborations, a new era has begun in binary black hole (BBH) merger processes and black hole physics studies. The fact that very massive stars that will become black holes at the end of their evolution are in binary or multiple states adds particular importance to BBH studies. In this study, using the SEOBNRv4$_opt$ gravitational waveform model developed for compact binary systems, many ($\sim 10^6$) models were produced under different initial conditions, and the pre- and post-merge parameters were compared. In the models, it is assumed that the initial total mass (M${\rm{tot}}$) of the binary systems varies between 12-130 $\rm{M}\odot$ with step interval 1$\rm{M}\odot$, the mass ratios ($q = \rm{m}{1i}/\rm{m}{2i}$) vary between 1 and 2 with step interval 0.004, and the initial spin ($\abs{\rchi{1i}} = \abs{\rchi_{2i}}$) value varies between $-0.83$ and $+0.83$ with step interval 0.017. Final spin ($\rchi_{f}$), fractional mass loss (M${FL}$), and the maximum gravitational wave amplitude (h${\rm{max}}$) obtained during the merger were compared with appropriate tables and figures obtained from the results of the relativistic numeric model obtained according to the initial parameters. Our results show that M${\rm{FL}}$ in generated BBH coalescences varied about 2.7 to 9.2\%, and $\rchi{\rm{f}}$ between 0.29 and 0.91. In most of the BBHs we have modeled, we found that M${\rm{FL}}$ varies inversely with $q$. However, it has been found that M${\rm{FL}}$ values are not always inversely varied to the $q$ parameter in systems of opposite initial spin, where the large mass black hole component is positively oriented. Accordingly, it is understood that the values of M$_{\rm{FL}}$ decrease to a certain point of $q$ and then increase according to the increasing direction of $q$.

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&. Özbakır and K. Yakut
Thu, 20 Apr 23
23/57

Comments: 29 pages, 5 figure, 5 tables, submitted for publication

The formation of the first black holes [HEAP]

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http://arxiv.org/abs/2304.09311


The most massive black holes at redshifts z = 6 were already over billion solar masses. In this chapter, we discuss the formation and growth of the first black holes in the Universe. The deaths of massive primordial stars provide potential seeds of supermassive black holes. Theoretical models predict that the seed black hole masses range from 10 to 100,000 solar masses. Their initial fueling may be limited by feedback from its progenitor star, the black hole itself, and nearby star formation. Once the halo and galaxy surpasses a critical mass, black hole growth may accelerate as the central gravitational potential deepens with strong ensuing star formation.

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J. Wise
Thu, 20 Apr 23
24/57

Comments: 30 pages, 7 figures. This chapter is the pre-print of the version currently in production. Please cite this chapter as the following: J. H. Wise, “The formation of the first black holes,” in The Encyclopedia of Cosmology (Set 2): Black Holes, edited by Z. Haiman (World Scientific, New Jersey, 2023)

Observations of Stellar-Mass Black Holes in the Galaxy [HEAP]

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http://arxiv.org/abs/2304.09368


Stellar-mass black holes (BHs), with masses comparable to stars, are a major constituent of our Milky Way galaxy. This chapter describes the landscape of challenging, and long-sought efforts to identify these objects in the Galaxy. The first stellar-mass BHs were identified as persistent, but highly variable cosmic X-ray sources. Later, transient BH candidates were detected, and now far outnumber the persistent sources. Decades of effort have also yielded candidate BHs via gravitational microlensing and their orbital effect on binary companions. Populations of BH systems have begun to emerge from these detection strategies, offering insight into the astrophysical context in which BHs exist and driving questions about the formation, assembly, and ongoing evolution of these enigmatic objects.

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M. MacLeod and J. Grindlay
Thu, 20 Apr 23
26/57

Comments: This chapter is the pre-print of the version currently in production. Please cite this chapter as the following: M. MacLeod and J. Grindlay “Observations of Stellar-Mass Black Holes in the Galaxy,” in The Encyclopedia of Cosmology (Set 2): Black Holes, edited by Z. Haiman (World Scientific, New Jersey, 2023). We welcome comments or feedback

RadioAstron Space VLBI Imaging of the jet in M87: I. Detection of high brightness temperature at 22 GHz [GA]

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http://arxiv.org/abs/2304.09816


We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in Feb 2014 at 22 GHz with 21 ground stations, reaching projected $(u,v)$-spacings up to $\sim11\,$G$\lambda$. The imaging experiment was complemented by snapshot RadioAstron data of M87 obtained during 2013–2016 from the AGN Survey Key Science Program. Their longest baselines extend up to $\sim25\,$G$\lambda$. For all these measurements, fringes are detected only up to $\sim$2.8 Earth Diameter or $\sim$3 G$\lambda$ baseline lengths, resulting in a new image with angular resolution of $\sim150\,\mu$as or $\sim20$ Schwarzschild radii spatial resolution. The new image not only shows edge-brightened jet and counterjet structures down to submilliarcsecond scales but also clearly resolves the VLBI core region. While the overall size of the core is comparable to those reported in the literature, the ground-space fringe detection and slightly super-resolved RadioAstron image suggest the presence of substructures in the nucleus, whose minimum brightness temperature exceeds $T_{\rm B, min}\sim10^{12}\,$K. It is challenging to explain the origin of this record-high $T_{\rm B, min}$ value for M87 by pure Doppler boosting effect with a simple conical jet geometry and known jet speed. Therefore, this can be evidence for more extreme Doppler boosting due to a blazar-like small jet viewing angle or highly efficient particle acceleration processes occurring already at the base of the outflow.

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J. Kim, T. Savolainen, P. Voitsik, et. al.
Thu, 20 Apr 23
29/57

Comments: 27 pages, 13 figures, accepted for publication in ApJ

Confronting strange stars with compact-star observations and new physics [HEAP]

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http://arxiv.org/abs/2304.09614


Strange stars ought to exist in the universe according to the strange quark matter hypothesis, which states that matter made of roughly equal numbers of up, down, and strange quarks could be the true ground state of baryonic matter rather than ordinary atomic nuclei. Theoretical models of strange quark matter, such as the standard MIT bag model, the density-dependent quark mass model, or the quasi-particle model, however, appear to be unable to reproduce some of the properties (masses, radii and tidal deformabilities) of recently observed compact stars. This is different if alternative gravity theory (e.g., non-Newtonian gravity) or dark matter (e.g., mirror dark matter) are considered, which resolve these issues. The possible existence of strange stars could thus provide a clue to new physics, as discussed in this review.

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S. Yang, C. Pi, X. Zheng, et. al.
Thu, 20 Apr 23
38/57

Comments: 26 pages, 11 figures. Review paper accepted for publication in Universe

Investigating the large-scale environment of wide-angle tailed radio galaxies in the local Universe [CEA]

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http://arxiv.org/abs/2304.09192


We present a statistical analysis of the large-scale (up to 2 Mpc) environment of an homogeneous and complete sample, both in radio and optical selection, of wide-angle tailed radio galaxies (WATs) in the local Universe (i.e., with redshifts $z\lesssim$ 0.15). The analysis is carried out using the parameters obtained from cosmological neighbors within 2 Mpc of the target source. Results on WATs large-scale environments are then compared with that of Fanaroff-Riley type I (FR Is) and type II (FR IIs) radio galaxies, listed in two others homogeneous and complete catalogs, and selected with the same criterion adopted for the WATs catalog. We obtain indication that at low redshift WATs inhabit environments with a larger number of galaxies than that of FR Is and FR IIs. In the explored redshift range, the physical size of the galaxy group/cluster in which WATs reside appears to be almost constant with respect to FR Is and FR IIs, being around 1 Mpc. From the distribution of the concentration parameter, defined as the ratio between the number of cosmological neighbors lying within 500 kpc and within 1 Mpc, we conclude that WATs tend to inhabit the central region of the group/cluster in which they reside, in agreement with the general paradigm that WATs are the cluster BCG.

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V. Missaglia, A. Paggi, F. Massaro, et. al.
Thu, 20 Apr 23
43/57

Comments: 8 pages, 5 figures, 1 table. Accepted for publication on A&A

Dark matter effects in modified teleparallel gravity [CL]

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http://arxiv.org/abs/2304.07364


This work investigates dark matter (DM) effects in compact objects in modified teleparallel gravity (MTG) in which a modification of Teleparallel Equivalent to General Relativity is used. We applied a tetrad to the modified field equations where a set of relations is found. The conservation equation allows us to rewrite our Tolman-Oppenheimer-Volkoff equations with an effective gravitational coupling constant. As input to these new equations, we use a relativistic mean-field (RMF) model with dark matter content included, obtained from a Lagrangian density with both, hadronic and dark particle degrees of freedom, as well as the Higgs boson, used as a mediator in both sectors of the theory. Through numerical calculations, we analyze the mass-radius diagrams obtained from different parametrizations of the RMF-DM model, generated by assuming different values of the dark particle Fermi momentum and running the free parameter coming from the MTG. Our results show that it is possible for the system simultaneously support more DM content, and be compatible with recent astrophysical data provided by LIGO and Virgo Collaboration, as well as by NASA’s Neutron star Interior Composition Explorer (NICER).

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S. Vilhena, M. Dutra, O. Lourenço, et. al.
Thu, 20 Apr 23
44/57

Comments: 8 pages, 2 figures

Black holes as the end state of stellar evolution: Theory and simulations [HEAP]

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http://arxiv.org/abs/2304.09350


The collapse of massive stars is one of the most-studied paths to black hole formation. In this chapter, we review black hole formation during the collapse of massive stars in the broader context of single and binary stellar evolution and the theory of supernova explosions. We provide a concise overview of the evolutionary channels that may lead to black hole formation — the classical route of iron core collapse, collapse due to pair instability in very massive stars, and the hypothetical scenario of supermassive star collapse. We then review the current understanding of the parameter space for black hole formation and black hole birth properties that has emerged from theoretical and computational modelling of supernova explosions and transient observations. Finally, we discuss what the intricate interplay between stellar evolution, stellar explosions, and binary interactions implies for the formation of stellar-mass black holes.

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A. Heger, B. Müller and I. Mandel
Thu, 20 Apr 23
51/57

Comments: 53 pages, 9 figures. This chapter is the pre-print of the version currently in production. Please cite this chapter as the following: A.Heger, B. M\”uller, and I. Mandel. “Black holes as the end state of stellar evolution: Theory and simulations,” in The Encyclopedia of Cosmology (Set 2): Black Holes, edited by Z. Haiman (World Scientific, New Jersey, 2023)