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Hydrodynamic studies of stellar-mass compact objects (COs) in a common envelope (CE)have shown that the accretion rate onto the CO is a few orders of magnitude below the Bondi-Hoyle-Lyttleton (BHL) estimate. This is several orders of magnitude above the Eddington limit and above the limit for neutrino-cooled accretion (i.e., hypercritical accretion, or HCA). Considering that a binary system inside the CE of a third star accretes material at nearly the same rate as a single object of the same total mass, we propose stellar-evolution channels which form binary black hole (BBH) systems with its component masses within the pair-instability supernova (PISN) mass gap. Our model is based on HCA onto the BBH system engulfed into the CE of a massive tertiary star. Furthermore, we propose a mass transfer mode which allows to store mass lost by the binary onto a third star. Through the use of population synthesis simulations for the evolution of BBHs and standard binary-evolution principles for the interaction with a tertiary star, we are able to produce BBHs masses consistent with those estimated for GW190521. We also discuss the massive binary system Mk34 as a possible progenitor of BBHs in the PISN gap, as well as the spin distribution of the observed mergers in the gravitational-wave catalog., 10 pages, 3 figures, 2 tables, submitted. Comments welcome

A counter-current jet (CCJ) is significantly different from a classical jump – it is like a classical jump with a reverse surface jet layer above it. A series of experiments, with the jet's Froude number in the range 4–10, was conducted to investigate the velocity distribution characteristics of CCJs. It was found, compared with a classical jump, the CCJ velocity distribution was more even and the decay of the maximum velocity was more efficient. It was beneficial to the energy dissipation and the deceleration of a high-speed flow. The variations of velocity with depth were opposite in the upper and lower parts of the zero-velocity line, resulting in relatively large fluid internal friction near the zero-velocity line. The internal friction between the surface jet layer and the lower fluid also increased the energy dissipation rate. A counter-current energy dissipator was found to achieve a good energy dissipation effect without auxiliary energy dissipators, which could be beneficial to engineering applications.

The Zwicky Transient Transient Facility (ZTF) performs a systematic neutrino follow-up program, searching for optical counterparts to high-energy neutrinos with dedicated Target-of-Opportunity (ToO) observations. Since first light in March 2018, ZTF has taken prompt observations for 24 high-quality neutrino alerts from the IceCube Neutrino Observatory, with a median latency of 12.2 hours from initial neutrino detection. From two of these campaigns, we have already reported tidal disruption event (TDE) AT2019dsg and likely TDE AT2019fdr as probable counterparts, suggesting that TDEs contribute >7.8% of the astrophysical neutrino flux. We here present the full results of our program through to December 2021. No additional candidate neutrino sources were identified by our program, allowing us to place the first constraints on the underlying optical luminosity function of astrophysical neutrino sources. Transients with optical absolutes magnitudes brighter that -21 can contribute no more than 87% of the total, while transients brighter than -22 can contribute no more than 58% of the total, neglecting the effect of extinction. These are the the first observational constraints on the neutrino emission of bright populations such as superluminous supernovae. None of the neutrinos were coincident with bright optical AGN flares comparable to that observed for TXS 0506+056/IC170922A, suggesting that most astrophysical neutrinos are not produced during such optical flares. We highlight the outlook for electromagnetic neutrino follow-up programs, including the expected potential for the Rubin Observatory., Submitted to MNRAS, comments welcome!

Gravitational lensing of fast radio bursts (FRBs) offers an exciting avenue for several cosmological applications. However, it is not yet clear how many such events future surveys will detect nor how to optimally find them. We use the known properties of FRBs to forecast detection rates of gravitational lensing on delay time-scales from microseconds to years, corresponding to lens masses spanning 15 orders of magnitude. We highlight the role of the FRB redshift distribution on our ability to observe gravitational lensing. We consider cosmological lensing of FRBs by stars in foreground galaxies and show that strong stellar lensing will dominate on microsecond time-scales. Upcoming surveys such as DSA-2000 and CHORD will constrain the fraction of dark matter in compact objects (e.g. primordial black holes) and may detect millilensing events from intermediate mass black holes (IMBHs) or small dark matter halos. Coherent all-sky monitors will be able to detect longer-duration lensing events from massive galaxies, in addition to short time-scale lensing. Finally, we propose a new application of FRB gravitational lensing that will measure directly the circumgalactic medium of intervening galaxies.

The BSW effect implies that the energy $E_{c.m.}$ in the center of mass frame of two particles colliding near a black hole can become unbounded. Usually, it is assumed that particles move along geodesics or electrogeodesics. Instead, we consider another version of this effect. One particle is situated at rest near a static, generally speaking, distorted black hole. If another particle (say, coming from infinity) collides with it, the energy of collision $E_{c.m.}$ in the center of mass frame grows unbounded (the BSW effect). The force required to keep such a particle near a black hole diverges for nonextremal horizons but remains finite nonzero for extremal one and vanishes in the horizon limit for ultraextremal black holes. Generalization to the rotating case implies that a particle corotates with a black hole but does not have a radial velocity. In doing so, the energy $E\rightarrow 0$, provided the angular momentum $L=0$. This condition replaces that of fine-tuning parameters in the standard version of the BSW effect., 10 pages. Substantial revision, typos corrected. To appear in Grav. Cosm

The current generation of galaxy simulations can resolve individual giant molecular clouds, the progenitors of dense star clusters. But the evolutionary fate of these young massive clusters, and whether they can become the old globular clusters (GCs) observed in many galaxies, is determined by a complex interplay of internal dynamical processes and external galactic effects. We present the first star-by-star $N$-body models of massive ($N\sim10^5-10^7$) star clusters formed in a FIRE-2 MHD simulation of a Milky Way-mass galaxy, with the relevant initial conditions and tidal forces extracted from the cosmological simulation. We select 895 ($\sim 30\%$) of the YMCs with $ > 6\times10^4M_{\odot}$ from Grudić et al.~2022 and integrate them to $z=0$ using the Cluster Monte Carlo Code, \texttt{CMC}. This procedure predicts a MW-like system with 148 GCs, predominantly formed during the early, bursty mode of star formation. Our GCs are younger, less massive, and more core-collapsed than clusters in the Milky Way or M31. This results from the assembly history and age-metallicity relationship of the host galaxy: younger clusters are preferentially born in stronger tidal fields and initially retain fewer stellar-mass black holes, causing them to lose mass faster and reach core collapse sooner than older GCs. Our results suggest that the masses and core/half-light radii of GCs are shaped not only by internal dynamical processes, but also by the specific evolutionary history of their host galaxies. These results emphasize that $N$-body studies with realistic stellar physics are crucial to understanding the evolution and present-day properties of GC systems., 24 pages, 16 figures, matches version accepted by MNRAS

Ongoing MeV telescopes such as INTEGRAL/SPI and Fermi/GBM, and proposed telescopes including the recently accepted COSI and the e-ASTROGAM and AMEGO missions, provide another window in understanding transients. Their signals contain information about the stellar explosion mechanisms and their corresponding nucleosynthesis of short-lived radioactive isotopes. This raises the need of a radiative transfer code which may efficiently explore different types of astrophysical $\gamma$-ray sources and their dependence on model parameters and input physics. In view of this, we present our new Monte-Carlo Radiative Transfer code in Python. The code synthesizes the $\gamma$-ray spectra and light curves suitable for modeling supernova ejecta, including C+O novae, O+Ne novae, Type Ia and core-collapse supernovae. We test the code extensively for reproducing results consistent with analytic models. We also compare our results with similar models in the literature and discuss how our code depends on selected input physics and setting., Comment: 15 pages, 25 figures, published in the Monthly Notices of the Royal Astronomical Society, submitted at 08 May 2022, accepted at 14 Feb 2023, published at 20 Feb 2023

Supermassive black holes (SMBHs) merging in dwarf galaxies will be detectable by the Laser Interferometer Space Antenna (LISA) in the mid-2030s. Previous cosmological hydrodynamic simulations have shown the prediction of massive black holes merging in dwarf galaxies, but these simulations are limited by their resolution and cannot follow black hole pairs all the way to coalescence. We calculate the delay time between black hole pairing and merger based on the properties of the black holes and their host galaxies, and use these properties to calculate gravitational wave strains for eleven different binary black holes that merge inside dwarf galaxies from eight cosmological simulations. This delay time calculation accounts for dynamical friction due to gas and stars, loss-cone scattering, and hardening of the binary due to gravitational radiation. Out of the eleven black hole mergers in the simulations, five black hole pairs will merge within 0.8 - 8 Gyr of forming a close pair and could be observed by LISA, and the remaining six are unresolved due to resolution limitations of the simulation. As all five of the resolved close pairs merge within a Hubble time, we make the broad estimate that close SMBH pairs in dwarf galaxies will merge and be detectable by LISA, but this estimate depends on either the presence of gas during orbital decay or a solution to the dynamical buoyancy problem in cored potentials., 8 pages, 3 figures

Let $\Gamma$ be an irreducible lattice in a product of two locally compact groups and assume that $\Gamma$ is densely embedded in a profinite group $K$. We give necessary conditions which imply that the left translation action $\Gamma\curvearrowright K$ is "virtually" cocycle superrigid: any cocycle $w:\Gamma\times K\rightarrow\Delta$ with values in a countable group $\Delta$ is cohomologous to a cocycle which factors through the map $\Gamma\times K\rightarrow\Gamma\times K_0$, for some finite quotient group $K_0$ of $K$. As a corollary, we deduce that any ergodic profinite action of $\Gamma=\text{SL}_2(\mathbb Z[S^{-1}])$ is virtually cocycle superrigid and virtually W$^*$-superrigid, for any finite nonempty set of primes $S$.

The understanding of neutron transport by Monte Carlo simulations led to major advancements towards precise interpretation of measurements. URANOS (Ultra Rapid Neutron-Only Simulation) is a free software package which has been developed in the last few years in cooperation with particle physics and environmental sciences, specifically for the purposes of cosmic-ray neutron sensing (CRNS). Its versatile user interface and input/output scheme tailored for CRNS applications offers hydrologists straightforward access to model individual scenarios and to directly perform advanced neutron transport calculations. The geometry can be modeled layer-wise, whereas in each layer a voxel geometry is extruded using a two-dimensional map from pixel images representing predefined materials and allowing for the construction of objects on the basis of pixel graphics without a three-dimensional editor. It furthermore features predefined cosmic-ray neutron spectra and detector configurations and also allows for a replication of important site characteristics of study areas – from a small pond to the catchment scale. The simulation thereby gives precise answers to questions like from which location do neutrons originate? How do they propagate to the sensor? What is the neutron's response to certain environmental changes? In recent years, URANOS has been successfully employed by a number of studies, for example, to calculate the cosmic-ray neutron footprint, signals in complex geometries like mobile applications on roads, urban environments and snow patterns.

The first directly observed gravitational wave event, GW150914, featuring the merger of two massive black holes, highlighted the need to determine how these systems of compact remnant binaries are formed. We use the binary population synthesis code COSMIC (Compact Object Synthesis and Monte Carlo Investigation Code) to predict the types of massive stars that will show significant radial velocity variations, indicative of a potential compact object (i.e. a black hole or neutron star) orbiting the star. We "observe" the binaries generated in the populations with a similar number of epochs and RV accuracy as planned for the Milky Way Mapper. In this analysis, we are especially interested in systems where a compact remnant is orbiting a massive O or B star as these systems survived the first supernova and neutron star kick. We test the ability of the Milky Way Mapper observing strategy to distinguish among different mass loss and kick prescriptions. We find that Wolf-Rayet stars or hot subdwarfs in binaries could be detectable (i.e. luminous, high delta RV max), viable progenitors of such objects, while the different prescriptions primarily affect the number of sources., submitted to MNRAS main journal, comments are welcome

We present a systematic study of the unbinned, photon-by-photon likelihood technique which can be used as an alternative method to analyse phase-dependent, X-ray spectro-polarimetric observations obtained with IXPE and other photo-electric polarimeters. We apply the unbinned technique to models of the luminous X-ray pulsar Hercules X-1, for which we produce simulated observations using ixpeobssim package. We consider minimal knowledge about the actual physical process responsible for the polarized emission from the accreting pulsar and assume that the observed phase-dependent polarization angle can be described by the rotating vector model. Using the unbinned technique, the detector's modulation factor, and the polarization information alone, we found that both the rotating vector model and the underlying spectro-polarimetry model can reconstruct equally well the geometric configuration angles of the accreting pulsar. However, the measured polarization fraction becomes biased with respect to underlying model unless the energy dispersion and effective area of the detector are also taken into account. To this end, we present an energy-dispersed likelihood estimator that is proved to be unbiased. For different analyses, we obtain posterior distributions from multiple ixpeobssim realizations and show that the unbinned technique yields $\sim 10\%$ smaller error bars than the binned technique. We also discuss alternative sources, such as magnetars, in which the unbinned technique and the rotating vector model might be applied., 11 pages, 9 figures. Accepted for publication in MNRAS. Source code available at https://github.com/UBC-Astrophysics/Unbinned-Xray-polarimetry

The goal of this paper is to investigate the flux and spectral index distribution of FR II radio galaxy 4C 14.11. We focused on the distribution of flux and spectral indices over the lobes, as well as in their hot spots. For that purpose, we used publicly available observations of this radio galaxy given at 1450 and 8440 MHz. Particularly, we used Leahy's Atlas of radio-emitting double radio sources, Jodrell Bank Centre for Astrophysics in Manchester, as well as NASA/IPAC Extragalactic Database. We found that the non-thermal (synchrotron) radiation dominates over the areas of the lobes. Distinction between hot spots and rest of the lobes are much smaller in the spectral index than in the flux. We also found that over the inner parts of both lobes, spectral index $\alpha$ is flat in average and significantly higher than 1.2, indicating that 4C 14.11 is old AGN., Comment: 8 pages, 5 figures, 1 FITS file. Accepted for publication in Adv. Space Res

Galactic black hole candidate MAXI J1910-057/Swift J1910.2-0546 was simultaneously discovered by MAXI/GSC and Swift/BAT satellites during its first outburst in 2012. We study the detailed spectral and temporal properties of the source in a broad energy range using archival data from Swift/XRT, MAXI/GSC and Swift/BAT satellites/instruments. Low frequency quasi periodic oscillations are observed during the outburst. The combined 1-50 keV spectra are analyzed using the transonic flow solution based Two Component Advective Flow (TCAF) model. Based on the variations of soft and hard X-ray fluxes, their hardness ratios and the variations of the spectral model fitted parameters, we find that the source has evolved through six spectral states. We interpret this spectral state evolution to be a result of two connected outbursts where the leftover matter from a primary outburst is released from the pile-up radius due to a sudden rise of viscosity causing a reflare/secondary outburst. We show a possible configuration of the evolution of accretion flow during the outburst. From the spectral analysis with TCAF model, we estimate the mass of the black hole to be $9.97^{+3.51}_{-3.24}$ $M_\odot$ , and the source distance is estimated to be $3.4-9.6$~kpc from transition luminosity considerations., 15 Pages, 8 Figures, 3 Tables (accepted for publication in Advances in Space Research)

The Event Horizon Telescope (EHT) collaboration has produced the first resolved images of the supermassive black holes at the centre of our galaxy and at the centre of the elliptical galaxy M87. As both technology and analysis pipelines improve, it will soon become possible to produce spectral index maps of black hole accretion flows on event horizon scales. In this work, we predict spectral index maps of both M87* and Sgr A* by applying the general relativistic radiative transfer (GRRT) code IPOLE to a suite of general relativistic magnetohydrodynamic (GRMHD) simulations. We analytically show that the spectral index increases with increasing magnetic field strength, electron temperature, and optical depth. Consequently, spectral index maps grow more negative with increasing radius in almost all models, since all of these quantities tend to be maximised near the event horizon. Additionally, photon ring geodesics exhibit more positive spectral indices, since they sample the innermost regions of the accretion flow with the most extreme plasma conditions. Spectral index maps are sensitive to highly uncertain plasma heating prescriptions (the electron temperature and distribution function). However, if our understanding of these aspects of plasma physics can be tightened, even the spatially unresolved spectral index around 230 GHz can be used to discriminate between models. In particular, Standard and Normal Evolution (SANE) flows tend to exhibit more negative spectral indices than Magnetically Arrested Disk (MAD) flows due to differences in the characteristic magnetic field strength and temperature of emitting plasma., Comment: Accepted for publication in MNRAS

We consider generalized Paley graphs $\Gamma(k,q)$, generalized Paley sum graphs $\Gamma^+(k,q)$, and their corresponding complements $\bar \Gamma(k,q)$ and $\bar \Gamma^+(k,q)$, for $k=3,4$. Denote by $\Gamma = \Gamma^*(k,q)$ either $\Gamma(k,q)$ or $\Gamma^+(k,q)$. We compute the spectra of $\Gamma(3,q)$ and $\Gamma(4,q)$ and from them we obtain the spectra of $\Gamma^+(3,q)$ and $\Gamma^+(4,q)$ also. Then we show that, in the non-semiprimitive case, the spectrum of $\Gamma(3,p^{3\ell})$ and $\Gamma(4,p^{4\ell})$ with $p$ prime can be recursively obtained, under certain arithmetic conditions, from the spectrum of the graphs $\Gamma(3,p)$ and $\Gamma(4,p)$ for any $\ell \in \mathbb{N}$, respectively. Using the spectra of these graphs we give necessary and sufficient conditions on the spectrum of $\Gamma^*(k,q)$ such that $\Gamma^*(k,q)$ and $\bar \Gamma^*(k,q)$ are equienergetic for $k=3,4$. In a previous work we have classified all bipartite regular graphs $\Gamma_{bip}$ and all strongly regular graphs $\Gamma_{srg}$ which are complementary equienergetic, i.e.\@ $\{\Gamma_{bip}, \bar{\Gamma}_{bip}\}$ and $\{\Gamma_{srg}, \bar{\Gamma}_{srg}\}$ are equienergetic pairs of graphs. Here we construct infinite pairs of equienergetic non-isospectral regular graphs $\{\Gamma, \bar \Gamma\}$ which are neither bipartite nor strongly regular., Comment: 22 pages

We explore the impact of diffusive cosmic rays (CRs) on the evolution of the interstellar medium (ISM) under varying assumptions of supernova explosion environment. In practice, we systematically vary the relative fractions of supernovae (SN) occurring in star-forming high-density gas and those occurring in random locations decoupled from star-forming gas to account for SN from run-away stars or explosions in regions that have been cleared by prior SN, stellar winds, or radiation. We explore various mixed models by adjusting these fractions relative to each other. We find that in the simple system of a periodic stratified gas layer the ISM structure will evolve to one of two solutions: a "peak driving" state where warm gas is volume filling or a "thermal runaway" state where hot gas is volume filling. CR pressure and transport are important factors that strongly influence the solution state the ISM reaches and have the ability to flip the ISM between solutions. Observable signatures such as gamma ray emission and HI gas are explored. We find that gamma ray luminosity from pion decay is largely consistent with observations for a range of model parameters. The thickness of the HI gas layer may be too compact, however, this may be due to a large cold neutral fraction of midplane gas. The volume fraction of hot gas evolves to stable states in both solutions, but neither settles to a Milky Way-like configuration, suggesting that additional physics which is omitted here (e.g. a cosmological circum-galactic medium, radiation transport, or spectrally resolved and spatially varying CR transport) may be required., Comment: 27 pages, 21 Figures, submitted to MNRAS, comments welcome

We present general relativistic radiation magnetohydrodynamics (GRRMHD) simulations of super-Eddington accretion flows around supermassive black holes (SMBHs) which may apply to tidal disruption events (TDEs). We perform long duration ($t\geq81,200\, GM/c^3$) simulations which achieve mass accretion rates $\gtrsim 11$ times the Eddington rate and produce thermal synchrotron spectra and images of their jets. The jet reaches a maximum velocity of $v/c \approx 0.5-0.9$, but the density weighted outflow velocity is $\sim0.2-0.35c$. Gas flowing beyond the funnel wall expands conically and drives a strong shock at the jet head while variable mass ejection along the jet axis results in internal shocks and dissipation. For a $T_i/T_e=1$ model, the radio/submillimeter spectra peak at $>100$ GHz and the luminosity increases with BH spin, exceeding $\sim 10^{41} \, \rm{erg\, s^{-1}}$ in the brightest models. The emission is extremely sensitive to $T_i/T_e$ as some models show an order of magnitude decrease in the peak frequency and up to four orders of magnitude decline in their radio/submillimeter luminosity as $T_i/T_e$ approaches 20. Assuming a maximum VLBI baseline distance of $10 \ {\rm{G}}\lambda$, 230 GHz images of $T_i/T_e=1$ models shows that the jet head may be bright enough for its motion to be captured with the EHT (ngEHT) at $D\lesssim110$ (180) Mpc at the $5\sigma$ significance level. Resolving emission from internal shocks requires $D\lesssim45$ Mpc for both the EHT or ngEHT. The 5 GHz emission in each model is dimmer ($\lesssim10^{36} \ {\rm{erg\, s^{-1}}}$) than upper limits placed on TDEs with no radio emission which suggests jets similar to our models may have gone undetected in previous observations. Our models suggest that the ngEHT may be utilized for $>230$ GHz radio/submillimeter followup of future TDEs.

We have investigated how kinetic instabilities such as the Weibel instability (WI), the mushroom instability (MI), and the kinetic Kelvin–Helmholtz instability (kKHI) are excited in jets without and with a toroidal magnetic field, and how such instabilities contribute to particle acceleration. In this work, we use a new jet injection scheme, where an electric current is self-consistently generated at the jet orifice by the jet particles, which produce the toroidal magnetic field. We perform five different simulations for a sufficiently long time to examine the non-linear effects of the jet evolution. We inject unmagnetized e± and e−– p+ (mp/me = 1836), as well as magnetized e± and e−– i+ (mi/me = 4) jets with a top-hat jet density profile into an unmagnetized ambient plasmas of the same species. We show that WI, MI, and kKHI excited at the linear stage, generate a non-oscillatory x-component of the electric field accelerating, and decelerating electrons. We find that the two different jet compositions (e± and e−– i+) display different instability modes, respectively. Moreover, the magnetic field in the non-linear stage generated by different instabilities is dissipated and reorganized into new topologies. A 3D magnetic field topology depiction indicates possible reconnection sites in the non-linear stage, where the particles are significantly accelerated by the dissipation of the magnetic field associated to a possible reconnection event. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., This work was supported by the National Aeronautics and Space Administration (NASA)-NNX12AH06G, NNX13AP-21G, and NNX13AP14G grants. Recent work was also provided by the NASA through Chandra Award Number GO7-18118X (PI: Ming Sun at UAH) issued by the Chandra X-ray Center, which is operated by the SAO for and on behalf of the NASA under contract NAS8-03060. The simulations presented in this report have been performed by Frontera supercomputer at the Texas Advanced Computing Center under the AST21038: Computational Study of Astrophysical Plasmas, and also provided by the NASA through by the grant: Nature Of Hard X-rays From A TeV-detected RadioGalaxy (PI: Ka Wah Wong at SUNY Brockport) issued by the NuSTAR Guest Observer Cycle 6 2019. Y.M. is supported by the ERC Synergy Grant ‘BlackHoleCam: Imaging the Event Horizon of Black Holes’ (Grant No. 610058). The work of I.D. has been supported by the NUCLEU project. Simulations were performed using Pleiades and Endeavor facilities at NASA Advanced Supercomputing (NAS: s2004), using Comet at The San Diego Supercomputer Center (SDSC), and Bridges at the Pittsburgh Supercomputing Center, which are supported by the National Science Foundation (NSF). JLG acknowledges the support of the Spanish Ministerio de Economía y Competitividad (grants AYA2016-80889-P, PID2019-108995GB-C21), the Consejería de Economía, Conocimiento, Empresas y Universidad, Junta de Andalucía (grant P18-FR-1769), the Consejo Superior de Investigaciones Científicas (grant 2019AEP112), and the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709)., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

Non-thermal emission from relativistic Cosmic Ray (CR) electrons gives insight into the strength and morphology of intra-cluster magnetic fields, as well as providing powerful tracers of structure formation shocks. Emission caused by CR protons on the other hand still challenges current observations and is therefore testing models of proton acceleration at intra-cluster shocks. Large-scale simulations including the effects of CRs have been difficult to achieve and have been mainly reduced to simulating an overall energy budget, or tracing CR populations in post-processing of simulation output and has often been done for either protons or electrons. We introduce CRESCENDO: Cosmic Ray Evolution with SpeCtral Electrons aND prOtons, an efficient on-the-fly Fokker-Planck solver to evolve distributions of CR protons and electrons within every resolution element of our simulation. The solver accounts for CR (re-)acceleration at intra-cluster shocks, based on results of recent PIC simulations, adiabatic changes and radiative losses of electrons. We show its performance in test cases as well as idealized galaxy cluster (GC) simulations. We apply the model to an idealized GC merger following best-fit parameters for CIZA J2242.4+5301-1 and study CR injection, radio relic morphology, spectral steepening and synchrotron emission., Comment: 25 pages (21 main paper + 4 appendix), 17 figures. Accepted for publication in MNRAS

We report on detailed multi-wavelength observations and analysis of the very bright and long GRB 210619B, detected by the Atmosphere-Space Interactions Monitor (ASIM) installed on the International Space Station (ISS) and the Gamma-ray Burst Monitor (GBM) on-board the Fermi mission. Our main goal is to understand the radiation mechanisms and jet composition of GRB 210619B. With a measured redshift of $z$ = 1.937, we find that GRB 210619B falls within the 10 most luminous bursts observed by Fermi so far. The energy-resolved prompt emission light curve of GRB 210619B exhibits an extremely bright hard emission pulse followed by softer/longer emission pulses. The low-energy photon indices ($\alpha_{\rm pt}$) values obtained using the time-resolved spectral analysis of the burst suggest a transition between the thermal (during harder pulse) to non-thermal (during softer pulse) outflow. We examine the correlation between spectral parameters and find that both peak energy and $\alpha_{\rm pt}$ exhibit the flux tracking pattern. The late time broadband photometric dataset can be explained within the framework of the external forward shock model with $\nu_m$ $< \nu_c$ $< \nu_{x}$ (where $\nu_m$, $\nu_c$, and $\nu_{x}$ are the synchrotron peak, cooling-break, and X-ray frequencies, respectively) spectral regime supporting a rarely observed hard electron energy index ($p, Comment: 24 pages, 18 figures, 10 tables, accepted for publication in MNRAS

Using the Gauss-Bonnet theorem, we compute and examine the deflection angle of light rays by rotating regular black holes with a cosmological constant. By the help of optical geometries, we first deal with the Hayward black holes with cosmological contributions. Then, we reconsider the study of the Bardeen solutions. We inspect the cosmological constant effect on the deflection angle of light rays. Concretely, we find extra cosmological correction terms generalizing certain obtained findings. Using graphical analysis, we provide a comparative discussion with respect to the Kerr solutions. The results confirm that the non-linear electrodynamic charges affect the space-time geometry by decreasing the deflection angle of light rays by such cosmological black holes., Comment: latex, 16 pages, 4 figures. Accepted for publication in Chin. J. Phys 2022

Full list of authors: Doroshenko, Victor; Poutanen, Juri; Tsygankov, Sergey S.; Suleimanov, Valery F.; Bachetti, Matteo; Caiazzo, Ilaria; Costa, Enrico; Di Marco, Alessandro; Heyl, Jeremy; La Monaca, Fabio; Muleri, Fabio; Mushtukov, Alexander A.; Pavlov, George G.; Ramsey, Brian D.; Rankin, John; Santangelo, Andrea; Soffitta, Paolo; Staubert, Rüdiger; Weisskopf, Martin C.; Zane, Silvia; Agudo, Iván; Antonelli, Lucio A.; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolò; Capitanio, Fiamma; Castellano, Simone; Cavazzuti, Elisabetta; Ciprini, Stefano; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Lalla, Niccolò; Donnarumma, Immacolata; Dovčiak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marin, Frédéric; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Matt, Giorgio; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Ng, Chi-Yung; O'Dell, Stephen L.; Omodei, Nicola; Oppedisano, Chiara; Papitto, Alessandro; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Pilia, Maura; Possenti, Andrea; Puccetti, Simonetta; Ratheesh, Ajay; Romani, Roger W.; Sgrò, Carmelo; Slane, Patrick; Spandre, Gloria; Sunyaev, Rashid A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicolas E.; Tombesi, Francesco; Trois, Alessio; Turolla, Roberto; Vink, Jacco; Wu, Kinwah; Xie, Fei., Using observations of X-ray pulsar Hercules X-1 by the Imaging X-ray Polarimetry Explorer we report a highly significant (>17σ) detection of the polarization signal from an accreting neutron star. The observed degree of linear polarization of ~10% is far below theoretical expectations for this object, and stays low throughout the spin cycle of the pulsar. Both the degree and angle of polarization exhibit variability with the pulse phase, allowing us to measure the pulsar spin position angle 57(2) deg and the magnetic obliquity 12(4) deg, which is an essential step towards detailed modelling of the intrinsic emission of X-ray pulsars. Combining our results with the optical polarimetric data, we find that the spin axis of the neutron star and the angular momentum of the binary orbit are misaligned by at least ~20 deg, which is a strong argument in support of the models explaining the stability of the observed superorbital variability with the precession of the neutron star. © 2022, The Author(s), under exclusive licence to Springer Nature Limited., This Article is based on observations made by IXPE, a joint US and Italian mission. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at the NASA Goddard Space Flight Center (GSFC). The US contribution is supported by NASA and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract number NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract number ASI-OHBI-2017-12-I.0, agreement numbers ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. V.D. and V.F.S. acknowledge support from the German Academic Exchange Service (DAAD) under travel grant number 57525212. J.P. and S.S.T. thank the Russian Science Foundation for support under grant number 20-12-00364 and the Academy of Finland for support under grant numbers 333112, 349144, 349373 and 349906. V.F.S. thanks the German Research Foundation (DFG) for grant number WE 1312/53-1. I.C. is a Sherman Fairchild Fellow at Caltech and thanks the Burke Institute at Caltech for supporting her research. A.A.M. acknowledges support from the Netherlands Organization for Scientific Research Veni Fellowship., info:eu-repo/grantAgreement/MICINN//SEV-2017-0709

Hole-twins – graphs that arise when a vertex is added to a hole in such a way to form a twin with some vertex of the hole – were discussed in a recent paper by Dai, Foley, and Hoang where it was shown that there is a polynomial time algorithm to color ( c l a w , 4 K 1 , hole-twin)-free graphs. We continue our investigation of hole-twin-free graphs and show the coloring problem for ( c l a w , P 7 , hole-twin)-free graphs is also polynomial-time solvable.

The paper answers the question posed in a joint paper by A. A. Klyachko and N. M. Luneva about the optimality of the estimate for the cost of symmetry in graphs. The original estimate says that if n vertices can be removed from a connected graph so that there is no connected subgraph of isomorphic $\Gamma$ left in it, then at most $n|V(\Gamma)|$ vertices that form a set invariant under all automorphisms of the graph so that the graph does not contain a subgraph isomorphic to $\Gamma$. We will prove that there exists a graph $\Gamma$ for which this estimate is not optimal., Comment: in Russian language

Black hole X-ray binaries (BHXRBs) display a wide range of variability phenomena, from long duration spectral state changes to short-term broadband variability and quasi-periodic oscillations (QPOs). A particularly puzzling aspect is the production of QPOs, which -- if properly understood -- could be used as a powerful diagnostic tool of black hole accretion and evolution. In this work we analyse a high resolution three-dimensional general relativistic magnetohydrodynamic simulation of a geometrically thin accretion disk which is tilted by $65^{\circ}$ with respect to the black hole spin axis. We find that the Lense-Thirring torque from the rapidly spinning 10 $M_\odot$ black hole causes several sub-disks to tear off within $\sim 10-20$ gravitational radii. Tearing occurs in cycles on timescales of seconds. During each tearing cycle the inner sub-disk precesses for 1-5 periods before it falls into the black hole. We find a precession frequency of $\sim 3\rm Hz$, consistent with observed low-frequency QPOs. In addition, we find a high frequency QPO (HFQPO) with centroid frequency of $\sim55$Hz in the power spectra of the mass-weighted radius of the inner disk. This signal is caused by radial epicyclic oscillations of a dense ring of gas at the tearing radius, which strongly suggests a corresponding modulation of the X-ray lightcurve and may thus explain some of the observed HFQPOs., Comment: submitted to MNRAS

Let $\Gamma$ be a countable group and let $G$ be the Schreier graph of the free part of the Bernoulli shift of $\Gamma$ (with respect to some finite subset $F \subseteq \Gamma$). We show that the Borel fractional chromatic number of $G$ is equal to $1$ over the measurable independence number of $G$. As a consequence, we asymptotically determine the Borel fractional chromatic number of $G$ when $\Gamma$ is the free group, answering a question of Meehan., Comment: 8 pp

The close correlation observed between emission state and spin-down rate change of pulsars has many implications both for the magnetospheric physics and the neutron star interior. The middle-aged pulsar PSR J0738$-$4042, which had been observed to display variations in the pulse profile associated with its spin-down rate change due to external effects, is a remarkable example. In this study, based on the 12.5-yr combined public timing data from UTMOST and Parkes, we have detected a new emission-rotation correlation in PSR J0738$-$4042 concurrent with a glitch. A glitch that occurred at MJD 57359(5) (December 3, 2015) with $\Delta\nu/\nu \sim 0.36(4)\times 10^{-9}$ is the first glitch event observed in this pulsar and is probably the underlying cause of the emission-rotation correlation. Unlike the usual post-glitch behaviours, the braking torque on the pulsar has continued to increase over 1380 d, corresponding to a significant decrease in $\ddot{\nu}$. As for changes in the pulse profile after the glitch, the relative amplitude of the leading component weakens drastically, while the middle component becomes stronger. A combined model of crustquake induced platelet movement and vortex creep response is invoked to account for this rare correlation. In this scenario, magnetospheric state-change is naturally linked to the pulsar-intrinsic processes that give rise to a glitch., Comment: 13 pages, 6 figures. Accepted for publication in MNRAS. Comments Welcome

In the supercritical range of the polytropic indices $\gamma\in(1,\frac43)$ we show the existence of smooth radially symmetric self-similar solutions to the gravitational Euler-Poisson system. These solutions exhibit gravitational collapse in the sense that the density blows-up in finite time. Some of these solutions were numerically found by Yahil in 1983 and they can be thought of as polytropic analogues of the Larson-Penston collapsing solutions in the isothermal case $\gamma=1$. They each contain a sonic point, which leads to numerous mathematical difficulties in the existence proof., Comment: 92 pages

Binary neutron star mergers are expected to produce fast dynamical ejecta, with mildly relativistic velocities extending to $\beta=v/c>0.6$. We consider the radio to X-ray synchrotron emission produced by collisionless shocks driven by such fast ejecta into the interstellar medium. Analytic expressions are given for spherical ejecta with broken power-law mass (or energy) distributions, $M(>\gamma\beta)\propto(\gamma\beta)^{-s}$ with $s=s_{\rm KN}$ at $\gamma\beta\gamma_0\beta_0$ (where $\gamma$ is the Lorentz factor). For parameter values characteristic of merger calculation results -- a "shallow" mass distribution, $15$, "fast tail" mass distribution -- our model provides an accurate (to 10's of percent) description of the evolution of the flux, including at the phase of deceleration to sub-relativistic expansion. This is a significant improvement over earlier results, based on extrapolations of results valid for $\gamma\beta\gg1$ or $\ll1$ to $\gamma\beta\approx1$, which overestimate the flux by an order of magnitude for typical parameter values. It will enable a more reliable inference of ejecta parameters from future measurements of the non-thermal emission. For the merger event GW170817, the existence of a "fast tail" is expected to produce detectable radio and X-ray fluxes over a time scale of $\sim10^4$days., Comment: 11 pages, 12 figures. Minor revisions following referee's report, accepted to MNRAS

Black hole accretion discs can produce powerful outflowing plasma (disc winds), seen as blue-shifted absorption lines in stellar and supermassive systems. These winds in Quasars have an essential role in controlling galaxy formation across cosmic time, but there is no consensus on how these are physically launched. A single unique observation of a stellar-mass black hole GRO J1655-40 was used to argue that magnetic driving was the only viable mechanism and motivated unified models of magnetic winds in both binaries and Quasars. The alternative, X-ray heating (thermal-radiative wind), was ruled out for the low observed luminosity by the high wind density estimated from an absorption line of a metastable level of Fe xxii. Here we reanalyse these data using a photoionisation code that includes cascades from radiative excitation as well as collisions in populating the metastable level. The cascade reduces the inferred wind density by more than an order of magnitude. The derived column is also optically thick, so the source is intrinsically more luminous than observed. We show that a thermal-radiative wind model calculated from a radiation hydrodynamic simulation matches well with the data. We revisit the previous magnetic wind solution and show that this is also optically thick, leading to a larger source luminosity. However, unlike the thermal-radiative wind, it struggles to reproduce the overall ion population at the required density. These results remove the requirement for a magnetic wind in these data and remove the basis of the self-similar unified magnetic wind models extrapolated to Quasar outflows, 14 pages, 15 figures, accepted by MNRAS

Simplified assumptions about the thermodynamics of the electrons are normally employed in general-relativistic magnetohydrodynamic (GRMHD) simulations of accretion onto black holes. To counter this, we have developed a self-consistent approach to study magnetised and radiatively cooled two-temperature accretion flows around a Kerr black hole in two spatial dimensions. The approach includes several heating processes, radiative cooling, and a coupling between the electrons and the ions via Coulomb interaction. We test our approach by performing axisymmetric GRMHD simulations of magnetised tori accreting onto a Kerr black hole under various astrophysical scenarios. In this way, we find that the inclusion of the Coulomb interaction and the radiative cooling impacts the thermodynamical properties of both the ions and electrons, changing significantly the temperature distribution of the latter, and underlining the importance of a two-temperature approach when imaging these flows. In addition, we find that the accretion rate influences the bulk properties of the flow as well as the thermodynamics of the electrons and ions. Interestingly, we observe qualitatively distinct temperature properties for SANE and MAD accretion modes while maintaining the same accretion rates, which could help distinguishing MAD and SANE accretion flows via observations. Finally, we propose two new relations for the temperature ratios of the electrons, ions, and of the gas in terms of the plasma-$\beta$ parameter. The new relations represent a simple and effective approach to treat two-temperature accretion flows on supermassive black holes such as Sgr A* and M\,87*., Comment: 13 pages, 8 figures, accepted for publication at MNRAS

The propagation of arbitrary amplitude ion-acoustic (IA) solitary waves (SWs) is studied in unmagnetized, collisionless, homogeneous electron-positron-ion (e-p-i) plasmas with finite temperature degeneracy of both electrons and positrons. Starting from a set of fluid equations for classical ions and Fermi-Dirac distribution for degenerate electrons and positrons, a linear dispersion relation for IA waves is derived. It is seen that the wave dispersion is significantly modified due to the presence of positron species and the effects of finite temperature degeneracy of electrons and positrons. In the nonlinear regime, the Sagdeev's pseudopotential approach is employed to study the existence domain and the evolution of nonlinear IA-SWs in terms of the parameters that are associated with the finite temperature degeneracy, the background number densities, and the thermal energies of electrons and positrons. It is found that in contrast to classical electron-ion plasmas both the subsonic and supersonic IA-SWs can exist in a partially degenerate e-p-i plasma., Comment: 9 pages, 5 figures; Revised version to appear in IEEE Transactions on Plasma Science

Due to the randomness of wind power generation, the output power of a wind farm will fluctuate. As a result, the power grid can face the need for increased reserve capacity, increasing scheduling difficulties and wind farm abandonment. An effective way to address these problems is to accurately predict the output power of wind farms. Traditional prediction methods usually make predictions based on wind data obtained at a single height. However, with long prediction periods, prediction errors are relatively large because the wind speed and direction at different heights have spatiotemporal correlations within a wind farm. In the model presented here, the wind power data are first decomposed by a ‘complete ensemble empirical mode decomposition with adaptive noise’ model to obtain modal components with different fluctuation characteristics. Then, the characteristics of wind speed, wind direction, air pressure and other data at different heights are extracted for spatiotemporal feature fusion. Actual measurement data from a wind farm in Chongqing, China are used to verify the feasibility and effectiveness of the proposed method.

We study evolution of single subhaloes with their masses of $\sim10^9 M_\odot$ in a Milky-Way-sized host halo for self-interacting dark matter (SIDM) models. We perform dark-matter-only N-body simulations of dynamical evolution of individual subhaloes orbiting its host by varying self-scattering cross sections (including a velocity-dependent scenario), subhalo orbits, and internal properties of the subhalo. We calibrate a gravothermal fluid model to predict time evolution in spherical mass density profiles of isolated SIDM haloes with the simulations. We find that tidal effects of SIDM subhaloes can be described with a framework developed for the case of collision-less cold dark matter (CDM), but a shorter typical time scale for the mass loss due to tidal stripping is required to explain our SIDM simulation results. As long as the cross section is less than $\sim10\, \mathrm{cm}^2/\mathrm{g}$ and initial states of subhaloes are set within a $2\sigma$-level scatter at redshifts of $\sim2$ predicted by the standard $\Lambda$CDM cosmology, our simulations do not exhibit a prominent feature of gravothermal collapse in the subhalo central density for 10 Gyr. We develop a semi-analytic model of SIDM subhaloes in a time-evolving density core of the host with tidal stripping and self-scattering ram pressure effects. Our semi-analytic approach provides a simple, efficient and physically-intuitive prediction of SIDM subhaloes, but further improvements are needed to account for baryonic effects in the host and the gravothermal instability accelerated by tidal stripping effects., Comment: 19 pages, 12 figures, 1 table. Accepted for publication in MNRAS. Note that results in the previous manuscript (v1) were affected by a bug in our SIDM implementation. We fixed the bug and updated all results accordingly

Since the discovery of an excess in gamma rays in the direction of M31, its cause has been unclear. Published interpretations focus on a dark matter or stellar related origin. Studies of a similar excess in the Milky Way center motivate a correlation of the spatial morphology of the signal with the distribution of stellar mass in M31. However, a robust determination of the best theory for the observed excess emission is very challenging due to large uncertainties in the astrophysical gamma-ray foreground model. Here we perform a spectro-morphological analysis of the M31 gamma-ray excess using state-of-the-art templates for the distribution of stellar mass in M31 and novel astrophysical foreground models for its sky region. We construct maps for the old stellar populations of M31 based on observational data from the PAndAS survey and carefully remove the foreground stars. We also produce improved astrophysical foreground models by using novel image inpainting techniques based on machine learning methods. We find that our stellar maps, taken as a proxy for the location of a putative population of millisecond pulsars in the bulge of M31, reach a statistical significance of $5.4\sigma$, making them as strongly favoured as the simple phenomenological models usually considered in the literature, e.g., a disk-like template with uniform brightness. Our detection of the stellar templates is robust to generous variations of the astrophysical foreground model. Once the stellar templates are included in the astrophysical model, we show that the dark matter annihilation interpretation of the signal is unwarranted. Using the results of a binary population synthesis model we demonstrate that a population of about one million unresolved MSPs could naturally explain the observed gamma-ray luminosity per stellar mass, energy spectrum, and stellar bulge-to-disk flux ratio., Comment: 15 pages, 11 figures, comments are welcome

Calculations of the inner mass function of the Hayward regular black hole with fluxes are reviewed and rederived. We present detailed calculations of the inner mass function in two forms of the Ori approach (the ingoing flux is continuous, the outgoing flux is modeled by a thin null shell) and compare them with calculations in Reissner-Nordstrom black hole. A formal reason of different results is discussed. The energy density of scalar perturbations propagating from the event horizon into the Hayward black hole measured by a free falling observer near the inner horizon is calculated., Comment: 14 pages, no figures

Neutron star-black hole (NSBH) mergers detected in gravitational waves have the potential to shed light on supernova physics, the dense matter equation of state, and the astrophysical processes that power their potential electromagnetic counterparts. We use the population of four candidate NSBH events detected in gravitational waves so far with a false alarm rate $\leq 1~\mathrm{yr}^{-1}$ to constrain the mass and spin distributions and multimessenger prospects of these systems. We find that the black holes in NSBHs are both less massive and have smaller dimensionless spins than those in black hole binaries. We also find evidence for a mass gap between the most massive neutron stars and least massive black holes in NSBHs at 98.6% credibility. Using an approach driven by gravitational-wave data rather than binary simulations, we find that fewer than 14% of NSBH mergers detectable in gravitational waves will have an electromagnetic counterpart. While the inferred presence of a mass gap and fraction of sources with a counterpart depend on the event selection and prior knowledge of source classification, the conclusion that the black holes in NSBHs have lower masses and smaller spin parameters than those in black hole binaries is robust. Finally, we propose a method for the multimessenger analysis of NSBH mergers based on the nondetection of an electromagnetic counterpart and conclude that, even in the most optimistic case, the constraints on the neutron star equation of state that can be obtained with multimessenger NSBH detections are not competitive with those from gravitational-wave measurements of tides in binary neutron star mergers and radio and X-ray pulsar observations., 13 pages, 9 figures, Data release URL in paper; matches published version

We measure the local correlation between radio emission and Compton-$y$ signal across two galaxy clusters, Abell~399 and Abell~401, using maps from the Low-Frequency Array (LOFAR) and the Atacama Cosmology Telescope (ACT) + \Planck. These datasets allow us to make the first measurement of this kind at $\sim$arcminute resolution. We find that the radio brightness scales as $F_{\mathrm{radio}} \propto y^{1.5}$ for Abell~401 and $F_{\mathrm{radio}} \propto y^{2.8}$ for Abell~399. Furthermore, using \XMM data, we derive a sublinear correlation between radio and X-ray brightness for both the clusters ($F_{\mathrm{radio}} \propto F_{\rm X}^{0.7}$). Finally, we correlate the Compton-$y$ and X-ray data, finding that an isothermal model is consistent with the cluster profiles, $y \propto F_{\rm X}^{0.5}$. By adopting an isothermal--$\beta$ model, we are able, for the first time, to jointly use radio, X-ray, and Compton-$y$ data to estimate the scaling index for the magnetic field profile, $B(r) \propto n_{\mathrm{e}}(r)^{\eta}$ in the injection and re-acceleration scenarios. Applying this model, we find that the combined radio and Compton-$y$ signal exhibits a significantly tighter correlation with the X-ray across the clusters than when the datasets are independently correlated. We find $\eta \sim 0.6{-}0.8$. These results are consistent with the upper limit we derive for the scaling index of the magnetic field using rotation measure values for two radio galaxies in Abell~401. We also measure the radio, Compton-$y$, and X-ray correlations in the filament between the clusters but conclude that deeper data are required for a convincing determination of the correlations in the filament., Comment: 16 pages, 8 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

We present theoretical mass estimates of $^{26}$Al and $^{60}$Fe throughout the Galaxy, performed with a numerical chemical evolution model including detailed nucleosynthesis prescriptions for stable and radioactive nuclides. We compared the results for several sets of stellar yields taken from the literature, for massive, low and intermediate mass stars, nova systems (only for $^{26}$Al) and supernovae Type Ia.We then computed the total masses of $^{26}$Al and $^{60}$Fe in the Galaxy. We studied the bulge and the disc of the Galaxy in a galactocentric radius range 0-22 kpc. We assumed that the bulge region (within 2 kpc) evolved quickly suffering a strong star formation burst, while the disc formed more slowly and inside-out. We compared our results with the $^{26}$Al mass observed by the $\gamma$-ray surveys COMPTEL and INTEGRAL to select the best model. Concerning $^{60}$Fe, we do not have any observed mass value so we just performed a theoretical prediction for future observations. In conclusion, low, intermediate mass stars and Type Ia supernovae contribute negligibly to the two isotopes, while massive stars are the dominant source. The nova contribution is, however, necessary to reproduce the observations of $^{26}$Al. Our best model predicts $2.12$ M$_{\odot}$ of $^{26}$Al, in agreement with observations, while for $^{60}$Fe our best mass estimate is $\sim 1.05$ M$_{\odot}$. We also predicted the present injection rate of $^{26}$Al and $^{60}$Fe in the Galaxy and compared it with previous results, and we found a larger present time injection rate along the disc., Comment: accepted,10 pages, 6 figures

The general-relativistic phenomenon of spin-induced orbital precession has not yet been observed in strong-field gravity. Gravitational-wave observations of binary black holes (BBHs) are prime candidates, since we expect the astrophysical binary population to contain precessing binaries. Imprints of precession have been investigated in several signals, but no definitive identification of orbital precession has been reported in any one of the 84 BBH observations to date by the Advanced LIGO and Virgo detectors. Here we report the measurement of strong-field precession in the LIGO-Virgo-Kagra (LVK) gravitational-wave signal GW200129. The binary's orbit precesses at a rate ten orders of magnitude faster than previous weak-field measurements from binary pulsars. We also find that the primary black hole is likely highly spinning. According to current binary population estimates a GW200129-like signal is extremely unlikely, and therefore presents a direct challenge to many current binary formation models., 16 pages, 6 figures. Update to match published version

The discovery of faint FR~I radio jets in the nearby elliptical galaxy NGC 5322 is reported here using 144 MHz LOFAR image. The jets have an angular extent of $\sim40$ arcmin or a projected physical extent of $\sim350$ kpc. The faint jets remain well collimated and disappear in the intergalactic medium, without any visible hotspot or radio lobes. The jets detected up to $\sim20$ kpc extent at higher frequencies are relatively bright within the optical extent of the galaxy but become faint abruptly outside, where detection is made only in the LOFAR image. The total radio luminosity of the galaxy at 144 MHz is estimated to be $3.7(\pm0.4)\times10^{22}$ W Hz$^{-1}$. The 144 MHz radio luminosity of the faint jets outside the optical extent is estimated to be $7.1(\pm2.0)\times10^{21}$ W Hz$^{-1}$. The extent of the jets for its radio luminosity is abnormally large when compared to the general population of radio galaxies. It makes NGC 5322 a member of a rare population of radio galaxies, previously not detected in other radio surveys. A combined effect of stellar core depletion and low-density environment around the jets, inferred from previous studies in other wave-bands, resulting into weak entrainment of surrounding material to the jets could be responsible for its large size despite a low radio luminosity., Comment: MNRAS submitted; 5 pages, 4 figures; comments welcome

Studying Ultraluminous X-ray sources (ULXs) in the optical wavelengths provides important clues about the accretion mechanisms and the evolutionary processes of X-ray binary systems. In this study, three (C1, C2, and C3) possible optical counterparts were identified for well-known neutron star (NS) candidate M51 ULX-8 through advanced astrometry based on the Chandra and Hubble Space Telescope, HST) observations, as well as the GAIA optical source catalogue. Optical periodic modulation of 125.5 days with an amplitude of 0.14 magnitude was determined for C3 which has evidence to represent the optical nature of ULX-8 using one-year (2016-2017) 34 HST ACS (Advanced Camera for Surveys)/WFC (Wide Field Camera) observations. Moreover, surprisingly, the observed optical fluxes of C3 exhibit a bi-modal distribution. This could mean that there is a possible correlation between the optical and the X-ray flux variabilities of the ULX-8. The possible scenarios which are frequently mentioned in the literature proposed for the nature of optical emission and optical super-orbital period. The most probable scenario is that the optical emission could have originated from the accretion disk of the ULX-8., ACCEPTED for publication in MNRAS. 11 pages, 9 figures, 4 Tables

The search for pulsars in a sample of pulsar candidates found based on a multi-year survey conducted with low (6 channels; sampling 0.1s) time-frequency resolution on declinations -9^o < \delta < +42^o was carried out. A Large Phased Array (LPA) transit telescope operating at 111 MHz in the 2.5 MHz band was used. Search, analysis and evidence of pulsar detection were carried out using a visualization program of summed up power spectra obtained from the survey data with high 32 channels; sampling 12.5ms) time-frequency resolution. 11 new pulsars with periods P0 = 0.41-3.75 s and dispersion measure DM=15-154 pc/cm^3 have been discovered. In total, in the survey with a low time-frequency resolution for the period 2016-2021 in a blind search, 208 pulsars were found, of them 42 new and 166 known pulsars. It is shown that in the search on the data with high time-frequency resolution accumulated over a time interval of 7 years, pulsars with a flux density of 0.1 - 0.2 mJy at the frequency of 111 MHz can be detected. When searching for pulsars with regular (periodic) emission at declinations +21^o < \delta < +42^o, all pulsars located outside the galactic plane, having P0 \ge 0.5 s, DM \le 100 pc/cm^3 and the flux density S \ge 0.5 mJy, can be detected, Comment: 13 pages, 7 figures, submitted to MNRAS

With its last observing run, the LIGO, Virgo, and KAGRA collaboration has detected almost one hundred gravitational waves from compact binary coalescences. A common approach to studying the population properties of the observed binaries is to use phenomenological models to describe the spin, mass, and redshift distributions. More recently, with the aim of providing a clearer link to astrophysical processes forming the observed compact binaries coalescences, several authors have proposed to employ synthetic catalogs for population studies. In this paper, we review how to employ and interpret synthetic binary catalogs for gravitational-wave progenitors studies. We describe how to build multi-channel merger rates and describe their associated probabilities focusing on stellar progenitor properties. We introduce a method to quantify the match between the phenomenological reconstruction of merger rates with synthetic catalogs. We detail the implementation of synthetic catalogs for multi-channel hierarchical Bayesian inference, highlighting computational aspects and issues related to hyper-prior choice. We find that when inferring stellar progenitors' properties from gravitational-wave observations, the relative efficiency in compact objects production should be taken into account. Finally, by simulating binary black hole detections with LIGO and Virgo sensitivity expected for the O4 observing run, we present two case studies related to the inference of the common envelope efficiency and progenitor metallicity of the binary black holes. We finally discuss how progenitors' properties can be linked to binary black hole properties., Comment: 13 pages, 12 figures, submitted to MNRAS

{"Bare collapse", the collapse of a bare stellar core to a neutron star with a very small mass ejection links two seemingly unrelated phenomena: the formation of binary neutron star (BNS) systems and the observations of fast and luminous optical transients. We carried out calculations of the collapse due to electron-capture of both evolutionary and synthetic isentropic bare stellar cores. We find that the collapse results in {the formation of} a light ~ 1.3 solar mass neutron star and {an} ejection of ~0.1 solar mass at ~0.1c. The outer shell of the ejecta is composed of Ni56 that can power an ultra-stripped supernova. The models we explored can explain most of the observed fast optical flares but not the brightest ones. Collapse of cores surrounded by somewhat more massive envelopes can produce larger amounts of Ni56 and explain brighter flares. Alternatively, those events can arise due to interaction of the very energetic ejecta with winds that were ejected from the progenitor a few days before the collapse., Comment: Accepted for publication in MNRAS

We study gas inflows onto supermassive black holes using hydrodynamics simulations of isolated galaxies and idealized galaxy mergers with an explicit, multiphase interstellar medium (ISM). Our simulations use the recently developed ISM and stellar evolution model called Stars and MUltiphase Gas in GaLaxiEs (SMUGGLE). We implement a novel super-Lagrangian refinement scheme that increases the gas mass resolution in the immediate neighborhood of the black holes (BHs) to accurately resolve gas accretion. We do not include black hole feedback in our simulations. We find that the complex and turbulent nature of the SMUGGLE ISM leads to highly variable BH accretion. BH growth in SMUGGLE converges at gas mass resolutions $\lesssim3\times10^3{\rm M_\odot}$. We show that the low resolution simulations combined with the super-Lagrangian refinement scheme are able to produce central gas dynamics and BH accretion rates very similar to that of the uniform high resolution simulations. We further explore BH fueling by simulating galaxy mergers. The interaction between the galaxies causes an inflow of gas towards the galactic centres and results in elevated and bursty star formation. The peak gas densities near the BHs increase by orders of magnitude resulting in enhanced accretion. Our results support the idea that galaxy mergers can trigger AGN activity, although the instantaneous accretion rate depends strongly on the local ISM. We also show that the level of merger-induced enhancement of BH fueling predicted by the SMUGGLE model is much smaller compared to the predictions by simulations using an effective equation of state model of the ISM., 16 pages, 10 figures

The paper has been prepared for the JETP issue, dedicated to the 95th anniversary of the birth of E.I. Rashba. E. Rashba stood at the origins of macroscopic quantum tunneling together with his colleagues from the Landau Institute S.V. Iordansky and A.M. Finkelshtein. They pave the way for studying macroscopic quantum tunneling in various systems. In this paper, this approach is extended to cosmological objects such as a black hole and de Sitter Universe. In particular, this allowed to calculate the entropy of Reissner-Nordstr\"om (RN) black hole with two horizons and the corresponding temperature of the thermal Hawking radiation. Several different approaches were used: the method of semiclassical tunneling for calculation of the Hawking temperature; the cotunneling mechanism -- the coherent sequence of tunneling at two horizons, each determined by the corresponding Hawking temperature; the method of singular coordinate transformations for calculations of macroscopic quantum tunneling from the RN black hole to the RN white hole; the method of the adiabatic change of the fine structure constant for the adiabatic transformation from the RN black hole to the Schwarzschild black hole; etc., Comment: 22 pages, no figures, accepted in JETP, arXiv admin note: text overlap with arXiv:2103.10954, arXiv:2107.11193

Relativistic jets are believed to have a substantial impact on the gas dynamics and evolution of the interstellar medium (ISM) of their host galaxies. In this paper, we aim to draw a link between the simulations and the observable signatures of jet-ISM interactions by analyzing the emission morphology and gas kinematics resulting from jet-induced shocks in simulated disc and spherical systems. We find that the jet-induced laterally expanding forward shock of the energy bubble sweeping through the ISM causes large-scale outflows, creating shocked emission and high-velocity dispersion in the entire nuclear regions ($\sim2$ kpcs) of their hosts. The jetted systems exhibit larger velocity widths (> 800 km/s), broader Position-Velocity maps and distorted symmetry in the disc's projected velocities than systems without a jet. We also investigate the above quantities at different inclination angles of the observer with respect to the galaxy. Jets inclined to the gas disc of its host are found to be confined for longer times, and consequently couple more strongly with the disc gas. This results in prominent shocked emission and high-velocity widths, not only along the jet's path, but also in the regions perpendicular to them. Strong interaction of the jet with a gas disc can also distort its morphology. However, after the jets escape their initial confinement, the jet-disc coupling is weakened, thereby lowering the shocked emission and velocity widths., Matches the Published version

We estudy the $H^{p}(\mathbb{Z})$ - $\ell^{q}(\mathbb{Z})$ boundedness of the fractional series operator $T_{\gamma}$ given by \[ (T_{\gamma}b)(j) = \sum_{i \neq \pm j} \frac{b(i)}{|i-j|^{\alpha}|i+j|^{\beta}}, \] where $0 \leq \gamma < 1$, $\alpha, \beta > 0$ and $\alpha + \beta = 1 -\gamma$. By means of a counter-example, we also show that the operator $T_{\gamma}$ is not bounded from $H^{p}(\mathbb{Z})$ into $H^{q}(\mathbb{Z})$., Comment: 10 pages