High Energy Astrophysical Phenomena
Uncovering New Ionized Winds and Relativistic Hot Outflows in MCG-6-30-15 with Chandra HETG and a Bayesian Framework
Erika B. Hoffman, Anna Ogorzałek, Christopher S. Reynolds et al. (+1 more)
Active Galactic
Nuclei (AGN) feedback plays a key role in
galaxy evolution. Highly ionized outflows, detected in X-ray absorption, are a promising candidate for
quasar-mode feedback. We present a new
Bayesian analysis of 0.65 Ms of Chandra High Energy Transmission Gratings (HETG) observations of MCG-6-30-15 from 2000 and 2004. Our approach detects new wind components, improving estimates of outflow demographics and impact. These include a hot ultra-fast outflow (UFO; 0.08c), recently confirmed by XRISM but seen in HETG for the first time, which has the power to potentially influence its host
galaxy. We also detect the first potentially collisionally ionized absorbers in this source, a physical process typically not considered in previous analyses, but potentially important for wind impact and demographics. The warm absorber complex is resolved in unprecedented detail, uncovering evidence of a correlation between outflow velocity and ionization, constraining its geometry. We also confirm the presence of dust in the wind, clearly distinguishing it from the cold ISM components, which may impact wind acceleration. Our work highlights the power of applying new methods to deep, legacy HETG
datasets, and the limitations of current atomic databases when considering OIV, V, and VI K-shell transitions. Furthermore, our work establishes a baseline for decade-scale outflow variability for new observations with XRISM and NewAthena in the future.
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All authors Erika B. Hoffman, Anna Ogorzałek, Christopher S. Reynolds, Lia Corrales
High Energy Astrophysical Phenomena · Cross-listed from astro-ph.GA
Chandra Lensing-cluster Ultradeep Extragalactic Survey (CLUES) I: A 2 Ms Point-Source Catalog of the Abell 2744 Field
Shouyi Wang, Fan Zou, Elena Gallo et al. (+10 more)
In the first paper of the Chandra
Lensing-cluster Ultradeep Extragalactic Survey (CLUES), we present an ultradeep 2 Ms X-ray survey of the Abell 2744 field constructed from 101 archival Chandra ACIS-I observations. With an exposure comparable to the Chandra Deep Fields and further boosted by strong-
lensing magnification from the Abell 2744 cluster at $z=0.3$, this field represents the third deepest extragalactic X-ray survey of the sky and also has rich synergy with extensive coverage by the Hubble Space
Telescope and James Webb Space
Telescope. We present the Chandra data reduction and detect sources in the soft (0.5-2 keV), hard (2-7 keV), and full (0.5-7 keV) bands over a total area of $369~\mathrm{arcmin^2}$. We perform dedicated image fitting with Chandra point spread functions to optimize point-source detections and improve X-ray positions and further screen the detections to address the impact of the central bright, structured intracluster medium. A total of 327 X-ray point sources are detected and cataloged, including their X-ray photometry and basic spectral properties. Detailed simulations are also conducted, based on which the expected 50% flux completeness reaches $6.3\times10^{-16}$, $2.8\times10^{-16}$, and $4.9\times10^{-16}~\mathrm{erg~cm^{-2}~s^{-1}}$ in the full, soft, and hard bands, respectively. The source number density as a function of flux is consistent with those in blank-field surveys within a factor of $\approx2$, with a slight excess above $\approx10^{-14}~\mathrm{erg~cm^{-2}~s^{-1}}$. All X-ray data products are publicly released, including the catalog, X-ray images, exposure maps, background maps, and sensitivity maps.
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All authors Shouyi Wang, Fan Zou, Elena Gallo, Bin Luo, W. N. Brandt, Yuxuan Pang, Tommaso Treu, Xue-Bing Wu, Dieu D. Nguyen, Guido Roberts-Borsani, Shengzhe Wang, Weiwei Xu, Zihao Zuo
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
WIMPs with Enhanced Annihilation from a Feebly Interacting Unstable Partner
Chance Hoskinson, Pearl Sandick and Barmak Shams Es Haghi
Weakly interacting massive particles (WIMPs) constitute one of the best-motivated dark matter (DM) candidates. In this study, we consider a simple extension of the WIMP paradigm in which WIMPs are coupled to a heavier particle that interacts only with them and can decay into WIMPs. In the early Universe, when WIMPs are in thermal
equilibrium with the Standard Model (SM) bath, they serve as a portal to populate the heavy partner through inverse decays. Depending on the lifetime of the partner particle, its eventual decay into WIMPs can significantly alter the WIMP abundance. If the partner decays into WIMPs before their freeze-out from
equilibrium, the standard thermal history remains unchanged. When the decay occurs after WIMP freeze-out, however, the injected non-thermal population of WIMPs can result in an overproduction of DM, therefore requiring a larger WIMP annihilation cross section relative to the standard scenario without the partner. For a given partner lifetime and WIMP annihilation cross section, freeze-out may be delayed due to re-annihilation or followed by a freeze-in phase. By solving the Boltzmann equations both semi-analytically and numerically, we explore these thermal histories and study the required enhancement in the WIMP annihilation cross section compared to the canonical value. This enhancement, which can reach up to three orders of magnitude, leads to stronger annihilation signals in the late Universe. As a result, current and upcoming indirect detection experiments are able to probe the lifetime of the partner particle. We briefly explore possible connections between our scenario and the baryon asymmetry of the Universe. As an example, we show that the Next-to-Minimal Supersymmetric Standard Model (NMSSM) can provide a realization of our scenario, with the possibility of accommodating light higgsino DM with the correct relic abundance.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Proper Time Shifts in Pulsar Timing Arrays
Vincent S. H. Lee
Pulsar timing arrays are a powerful tool for probing low-frequency gravitational phenomena and physics beyond the Standard Model. We establish a general, gauge-invariant framework for the timing residual by identifying the measurable quantity as the proper time interval between consecutive pulse arrivals at Earth. In linearized general relativity, we derive a general expression for this proper time shift and show that it decomposes into Doppler, Shapiro, and Einstein delay contributions whose sum is gauge invariant, similar to frameworks that have been developed for other gravitational-wave detectors such as
laser and atom interferometers. We also provide a recipe for computing the resulting timing residual for any specified perturbation, and we illustrate the method with several physically well-motivated sources, recovering known results where they exist in the literature. This recipe can be directly applied to search for new physics from real
pulsar timing data using existing numerical software.
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High Energy Astrophysical Phenomena
Unifying spatial correlation with hierarchical population inference to constrain the AGN channel for binary black hole mergers
Lucas Pouw, Lorenzo Speri, Niccolò Veronesi et al. (+1 more)
The origin of the stellar-mass binary black holes (BBHs) observed in gravitational wave (GW) events by the LIGO-Virgo-KAGRA (LVK) detectors remains uncertain. One promising formation pathway is the active galactic
nucleus (AGN) channel, in which BBHs embedded in AGN
accretion discs experience enhanced merger rates and may produce rapidly spinning black holes in the upper mass gap. Previous constraints on the AGN contribution to the LVK merger population have relied either on spatial correlations between GW localisations and AGN catalogues or on modelling the intrinsic properties of GW sources. We develop a hierarchical
Bayesian framework that unifies these approaches within a single likelihood for the fraction of AGN-hosted GW events, $f_{\rm agn}$. This framework, combined with the latest gravitational wave transient catalogue GWTC-5.0 and the electromagnetic Quaia AGN catalogue, cannot exclude an AGN contribution to the observed merger rate. For unobscured AGN in the optical and infrared bands with bolometric luminosities $L_{\rm bol}\geq\{10^{44.5},10^{45.5},10^{46.5}\}\,\mathrm{erg\,s^{-1}}$, we exclude $f_{\rm agn} \geq \{0.52,0.41, 0.61\}$ at the 95 percent credible level under our fiducial model. The methodology and results presented in this work lay down the pathway for combining the full GW posterior with electromagnetic observations to infer the properties of GW populations and AGN discs.
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All authors Lucas Pouw, Lorenzo Speri, Niccolò Veronesi, Elena Maria Rossi
High Energy Astrophysical Phenomena
1D PIC Simulations of Resonant Scattering-Driven Pair Cascades in Magnetar Magnetospheres
Jens F. Mahlmann, Alexander A. Philippov, Adrien Soudais et al. (+2 more)
Hard X-rays in persistent magnetar emission originate from radiative processes in pair-loaded magnetospheric
plasma, yet self-consistent kinetic simulations of such radiation-rich systems remain limited. We perform 1D particle-in-
cell simulations of pair creation mediated by resonant inverse Compton scattering (RICS) along isolated field lines in twisted magnetospheres, capturing particle acceleration and radiative drag from first principles. The drag force, which strongly depends on the particle Lorentz factor and location, plays a key role in the magnetospheric
circuit. Strong RICS drag impedes the flow of electrons and positrons, particularly along extended field lines. Nevertheless, the
plasma sustains the
circuit by self-organizing into a single accelerating gap near the
star in one hemisphere. The accelerated
plasma flow from the gap becomes loaded with copious electron-positron pairs in extended RICS zones, and also carries ions extracted from the
star and accelerated in the gap. When radiative drag stops the pair-loaded flow at the
magnetic equator, the ion component transfers momentum through streaming instabilities, delivering a small lepton population into the opposite hemisphere and sustaining the
circuit. The gap confined to a single (anode) hemisphere implies asymmetric hard X-ray production, possibly detectable in phase-resolved magnetar spectra.
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All authors Jens F. Mahlmann, Alexander A. Philippov, Adrien Soudais, Andrei M. Beloborodov, Lorenzo Sironi
High Energy Astrophysical Phenomena
Constraints on the central engine of merger-driven long gamma-ray bursts
Muskan Yadav, Roberto Ricci, Paz Beniamini et al. (+4 more)
Recent observations have identified a new class of long-duration gamma-ray bursts (GRBs) likely produced by compact binary mergers. Using
radio observations and lightcurve modelling, we investigate whether a magnetar remnant can power the long-lasting
prompt emission observed in this merger-driven GRB sample. We derive constraints on the magnetars' rotational energy and
magnetic-field strength, and assess whether the magnetar central-engine model is viable for the observed events. We conducted 2.1 GHz
radio observations of seven nearby merger-driven GRBs ($z<0.25$) using the Australia
Telescope Compact Array (ATCA), obtaining sensitive upper limits on late-time
radio emission 520-6900 days post-burst. We modelled the expected
radio light curves from magnetar-energized ejecta interacting with the circumburst medium and compared them to our observations. We separately tested the magnetar hypothesis against the extended gamma-ray emission using a fallback-accreting magnetar model. No
radio counterpart is detected in any of the observed GRBs, with 3$\sigma$ flux density upper limits of 33-72 $\mu$Jy at 2.1 GHz. Modelling the expected synchrotron emission from magnetar-energized ejecta interacting with the circumburst medium, we find that the
radio non-detections remain compatible with energetic outflows in low-density environments. The analysis of the
prompt gamma-ray emission provides complementary constraints on the
spin period and
magnetic field of the magnetar engine. Once fallback
accretion and jet baryon-loading are considered, the parameter space is narrowly confined.
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All authors Muskan Yadav, Roberto Ricci, Paz Beniamini, Hira Waseem, Tatsuya Matsumoto, Simone Dichiara, Eleonora Troja
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Quasinormal modes of Kerr-Newman-de Sitter black holes from Heun connection formulae
Hideo Furugori, Naotaka Kubo, Hayato Motohashi et al. (+1 more)
We study quasinormal modes governed by the Teukolsky equation in Kerr-Newman-de Sitter spacetime, formally treating the
spin weight and field charge as arbitrary parameters. We use exact Heun connection formulae expressed through classical conformal blocks. We analytically derive the quasinormal mode spectra in the small cosmological constant, near-extremal, and near-Nariai limits. In the small cosmological constant limit, we obtain the leading charged de Sitter spectrum together with its subleading corrections. In both the small cosmological constant and near-extremal limits, solving the full connection condition beyond the leading pole approximation gives rise to generically noninteger-power corrections to the quasinormal mode frequencies, whereas no analogous correction appears in the near-Nariai limit. We also analyze the angular
eigenvalue problem as an illustration of the same connection-formula method.
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All authors Hideo Furugori, Naotaka Kubo, Hayato Motohashi, Daisuke Yoshida
High Energy Astrophysical Phenomena
Spontaneous wandering of the magnetic axis in pulsars: 3D magneto-thermal simulations and the imprint on braking indices
Clara Dehman and Daniele Viganò
Braking index measurements of hundreds of
pulsars, despite observational caveats, show a clear trend: $n<3$ at early ages, $n>3$ at middle ages, and increasingly large, fluctuating values at larger characteristic ages. Crustal
magnetic fields in isolated
neutron stars evolve through Ohmic dissipation and non-linear Hall redistribution across scales, with additional early-time contributions from the chiral
magnetic effect and post-burial re-emergence. Initial conditions are usually assumed dipole-dominated, whereas more complex and realistic fields, with energy spread more evenly over a broad range of scales, have not been explored in this context. We assess how the internal dynamics of initially non-trivial fields change the dipolar field strength and obliquity, and how their combined contribution to the braking index $n$, together with that of the
alignment, compares with the observed values. To this end we perform long-term 3D magneto-thermal simulations, for configurations ranging from the dipole-dominated case to tangled, small-scale-dominated fields. Small-scale dominated configurations with weak dipolar components show rich dynamics: the dipolar mode is continuously fed by the small scales and may grow or decay depending on the initial spectrum, driving $n<3$ or $n>3$, while the obliquity varies on timescales as short as ${\cal O}$(kyr). These spontaneous changes often dominate the
alignment torque and can account for the large values of $n-3$ of either sign observed at characteristic ages $\tau_c\gtrsim10^5$ yr, unlike the dipole-dominated models. However, short-term magnetospheric fluctuations or superfluid-driven variations of the torque may still be needed to explain the measurements and the structured timing residuals quantitatively. Future work comparing these models with the observed timing properties could fine-tune the most promising initial configurations.
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High Energy Astrophysical Phenomena
X-ray to Mid-IR Spectral Energy Distributions: A Catalog of X-ray Selected AGNs in the XMM-COSMOS Survey
Şeyda Şen, Eda Sonbas, Ece Kilerci et al. (+4 more)
We present a component-resolved analysis of the IR–X-ray connection in a sample of 104 spectroscopically confirmed Type~1 AGN. By combining \xmm, \swift/UVOT, and new high–angular resolution \jwst/NIRCam imaging for a subset of the sources, we constructed detailed SEDs in which the IR emission was explicitly decomposed into
accretion-disk,
torus, and polar-dust components. This approach enables us to isolate the intrinsic AGN-IR luminosities with minimal host-
galaxy contamination, providing a clean assessment of the physical relationship between the
accretion flow, circumnuclear dust, and the X-ray corona. By incorporating JWST/NIRCam observations into our SED decomposition, we significantly reduce host-
galaxy contamination and isolate the nuclear infrared emission with greater fidelity, particularly at near-infrared (NIR) wavelengths. This improvement is most apparent at 1 $\mu\mathrm{m}$, where sources with JWST coverage exhibit a markedly steeper relation between $\nu$L$_{\nu}$ (2 keV) and the NIR luminosity than those without JWST data. This behavior is naturally explained by starlight dilution, whereby host-
galaxy emission dominates lower-resolution measurements.
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All authors Şeyda Şen, Eda Sonbas, Ece Kilerci, Hasan Avdan, Kalvir S. Dhuga, Ersin Göğüş, W. N. Brandt
High Energy Astrophysical Phenomena
Large ${\rm Pm}$ small-scale kinematic dynamo in protoneutron stars
Shipra Verma, Kannabiran Seshasayanan, Raphaël Raynaud et al. (+1 more)
Magnetars are young, isolated
neutron stars that possess an exceptionally strong
magnetic field, with surface dipolar strengths on the order of $10^{15}$ G. One of the plausible scenarios for generating such a strong field is an exponential amplification by a turbulent convective dynamo during the protoneutron
star phase. However, the short expected duration of the convection ($\sim 10$ s) imposes a stringent constraint on the dynamo growth rate. We perform an extensive set of 82 three-dimensional convective dynamo simulations in the anelastic approximation and investigate the kinematic phase to quantify the dynamo growth rate $\gamma$. We find that $\gamma$ increases with both the
magnetic Prandtl number ${\rm Pm}$ and the Rayleigh number ${\rm Ra}$, with the most unstable mode becoming highly non-axisymmetric and multipolar. We further observe a gradual transition from large-scale to small-scale dynamo as the
magnetic Reynolds number ${\rm Rm}$ increases, resulting in a
magnetic field that is predominantly concentrated at small scales. The trend remains unchanged when the outer
magnetic boundary condition is varied. Since resolving the increasingly small scales becomes numerically impractical, we employ the theoretical small-scale Kazantsev dynamo model to explore the large ${\rm Pm}$ regime characteristic of protoneutron
stars. The model qualitatively captures the growth rate behaviour observed in simulations and, upon extrapolation to the large ${\rm Pm}$ limit, indicates that $\gamma$ is only weakly dependent on the resistivity in a PNS. Under conditions relevant to the PNS, this model predicts a
magnetic energy growth rate of the order of $\sim 1$ ms$^{-1}$.
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All authors Shipra Verma, Kannabiran Seshasayanan, Raphaël Raynaud, Jérôme Guilet
High Energy Astrophysical Phenomena
Caught by its own light: Wimpzillas, the LHAASO knee and the diffuse $\gamma$-ray sky
D. Akl, A.J. Iovino, D. Kantzas et al. (+1 more)
We use the
proton spectrum resolved by LHAASO across the knee to test superheavy dark matter in the nucleon channel at PeV energies. Both the hardening at $0.34$ PeV and the knee at $3.3$ PeV are reproduced by nucleons from a relic of mass $5\cdot 10^{7}$ GeV decaying in the Galactic
halo, with the mass as the only shape parameter of the spectrum and the background index profiled under an independent prior on the
proton slope below $0.1$ PeV. It works equally well in all three hadronic-interaction-model reconstructions. On the other hand, the
photons of the same cascade rule out this interpretation by about two orders of magnitude against the
photon fraction of the
cosmic radiation, and by about one order of magnitude against the LHAASO diffuse Galactic emission.
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All authors D. Akl, A.J. Iovino, D. Kantzas, A. V. Macciò
High Energy Astrophysical Phenomena
A fast radio burst from a non-targeted low-frequency survey
Cristian Di Pietrantonio, Marcin Sokolowski, Clancy W. James et al. (+13 more)
Fast
radio bursts (FRBs) are bright, millisecond-duration transient
radio signals of extragalactic origin with unknown source and emission mechanisms. While several thousand FRBs have been discovered at frequencies above 400 MHz, detections at lower frequencies have been exceptionally rare. Contributing to their rarity are the magnified dispersive delay, in the tens of seconds, and signal scattering that make low-frequency searches with established techniques computationally prohibitive. In particular, the only confirmed detection below 300 MHz came from a Low-Frequency Array observing campaign targeted at FRB 20180916B, a source already known to emit at higher frequencies. Here we present the first non-targeted detection of an FRB below 300 MHz, achieved in a wide-field, imaging-based survey with the Murchison Widefield Array. The implied FRB rate is consistent with that observed at higher frequencies, demonstrating that non-targeted wide-field surveys can uncover an unbiased, large low-frequency FRB population. This result challenges models invoking severe scattering or absorption to explain previous non-detections, and strengthens the case of low-frequency observations as promising avenue to study the local environment of FRBs.
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All authors Cristian Di Pietrantonio, Marcin Sokolowski, Clancy W. James, N. D. Ramesh Bhat, Randall Wayth, Danny C. Price, Christopher Harris, Chia Min Tan, Christopher P. Lee, Bradley W. Meyers, Mahitha Ega, Samuel J. McSweeney, Christopher Schlipalius, Gregory Sleap, Steven E. Tremblay, Mengyao Xue
High Energy Astrophysical Phenomena
Investigating past high-energy fluxes with paleo-detectors
Claudio Galelli
Paleo-detectors provide a unique avenue to reconstruct the multi-million-year history of
cosmic-ray (CR) flux, preserving signatures of transient high-energy events such as nearby
supernovae. This technique aims to use natural minerals as particle detectors, looking at the persistent damage tracks created by CR-induced nuclear recoils, accumulated over the minerals' geological lifespan, offering a geological archive of past particle fluxes. Building on our study of Messinian Salinity Crisis evaporites, which demonstrated that minerals with specific geological histories may enable the detection of primary CR flux variations, we have now expanded to diverse terrestrial records. This contribution presents our recent publication proposing olivine xenoliths from Auvergne, France, where eruption chronosequences could allow for the differentiation of CR flux scenarios over the last 50 kyr. This phenomenological work is supported by the INFN-funded PRImuS experiment, which aims to prove the efficacy of high-throughput optical microscopy and
plasma etching to analyze these mineral targets. By validating theoretical track-length spectra and refining the estimates of experimental effects, PRImuS's goal is to establish paleo-detectors as a powerful tool for very-long-range time-domain astrophysics.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Impact of the Host Galaxy on the Search for Gravitational-Wave Microlensing by Compact Objects
Uddeepta Deka, Apratim Ganguly, Soham Bhattacharyya et al. (+1 more)
Gravitational-wave (GW) microlensing occurs when an intervening compact object causes diffraction of the GW, imprinting characteristic frequency-dependent modulations on the observed signal. Current searches for microlensing signatures in the detected GW events, including those used to constrain the fraction of dark matter in the form of compact objects, assume an isolated point mass lens (PML) model. However, astrophysical compact objects are typically embedded within larger structures, such as
galaxies, whose potentials introduce additional convergence and tidal shear, thereby perturbing the lensed signal. In this work, we study the impact of the background
galaxy in the search for microlensing by compact objects using a PML model. We distribute the compact objects inside a
galaxy following the Navarro-Frenk-White density profile. We model the microlensing effects using the potential of a PML embedded in a constant convergence and shear, which are, in turn, calculated from a singular isothermal sphere model of the
galaxy lens. We demonstrate that neglecting the
galaxy's effects can systematically reduce sensitivity in microlensing searches, particularly for high microlens masses. Thus, future searches may need to incorporate the additional effect of the lens
galaxy, particularly those aimed at placing robust constraints on the abundance of compact dark matter.
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All authors Uddeepta Deka, Apratim Ganguly, Soham Bhattacharyya, Parameswaran Ajith
High Energy Astrophysical Phenomena
Impact of Equation of State on Black Hole Accretion Flows and Radiative Properties
Yun-Ming Zhu, Indu K. Dihingia, Yosuke Mizuno et al. (+2 more)
Previous literature has documented that black hole shadow images are mainly shaped by spacetime geometry and
plasma microphysics governing
accretion flows. However, the influence of equations of state (EoS) remains under-explored. In this paper, we quantify how different
plasma microphysics prescriptions, specifically the choice of EoS and electron-heating models, affect flow thermodynamics and the corresponding synthetic black-hole images. We perform three-dimensional general-relativistic magnetohydrodynamics (GRMHD) simulations using two constant-$\gamma$ ideal EoSs with $\gamma = 4/3$ and 5/3 and a temperature-dependent variable EoS (TM) in both
accretion flow states: Standard And Normal
Evolution (SANE) and Magnetically Arrested Disk (MAD) regimes. The dynamical models are post-processed with general-relativistic radiative transfer (GRRT) calculations at 86GHz and 230GHz, employing thermal and hybrid $\kappa$ electron distribution functions for synchrotron radiation. We also compare the two-temperature electron heating prescription based on turbulent heating and
magnetic reconnection. The constant-$\gamma$ EoSs systematically overestimate or underestimate gas and electron temperatures across disk and jet regions, whereas the variable EoS provides a smoother trans-relativistic interpolation between the two limiting regimes. These differences substantively impact the synchrotron emissivity, image morphology, and the amplitude of flux variability. In particular, the variable EoS exhibits systematically larger temporal variability than the constant-$\gamma$ models. These results demonstrate that adopting a physically self-consistent description of the EoS is essential for realistic modeling of
accretion-flow thermodynamics and horizon-scale images like Event Horizon
Telescope (EHT) observations.
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All authors Yun-Ming Zhu, Indu K. Dihingia, Yosuke Mizuno, Ziri Younsi, Christian M. Fromm
High Energy Astrophysical Phenomena
Testing a Pre-Supernova Contribution to $^{44}$Ti in Cassiopeia A
Toshiki Sato, Joshua Issa, Falk Herwig et al. (+4 more)
The radioactive isotope $^{44}$Ti in Cassiopeia A has been used as a tracer of the innermost ejecta and explosion asymmetries in core-collapse
supernova explosions. However, recent stellar-
evolution models suggest substantial $^{44}$Ti may also be synthesized prior to explosion during oxygen-carbon (O-C) shell mergers, a process proposed for the Cas A progenitor. We investigate this pre-
supernova contribution by combining NuSTAR measurements of the spatial and kinematic distribution of $^{44}$Ti with X-ray and infrared ejecta diagnostics. The low- and intermediate-velocity $^{44}$Ti components are more closely associated with O-layer tracers than with shocked Fe-rich material. If the $^{44}$Ti associated with the O-layer tracers was synthesized prior to core collapse, it could contribute up to $\sim7\times10^{-5}~M_\odot$, about half of the total. We find that this amount of $^{44}$Ti can be produced in O-C shell-merger models with ingestion rates and convective velocities higher than those in standard one-dimensional stellar-
evolution calculations. Stable Fe-group abundance ratios measured with XRISM provide an additional constraint on the explosive contribution, as three-dimensional models with larger $^{44}$Ti yields tend to predict Ti/Fe and Mn/Cr ratios above the observed values. These results suggest that both pre-
supernova shell-merger nucleosynthesis and explosive burning contribute to the observed $^{44}$Ti.
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All authors Toshiki Sato, Joshua Issa, Falk Herwig, Yui Kuboike, J. Martin Laming, Kai Matsunaga, Ryo Sawada
High Energy Astrophysical Phenomena
Population synthesis of low-mass binaries with wind-accreting neutron stars
Marina Afonina and Sergei Popov
We perform population synthesis modeling of
neutron star binary systems containing a low-mass main-sequence companion underfilling its Roche lobe. About $10^5$ such systems are expected to exist in the Milky Way. In the majority of such systems, NSs are expected to start accreting the stellar wind matter within a few Gyr, resulting in the appearance of a dim X-ray source. The exact value of this fraction mainly depends on the efficiency of the propeller
spin-down, properties of the stellar wind, and common envelope efficiency. Mostly, NSs in such systems are formed in electron capture
supernovae. Thus, they obtain a low natal kick. Due to this, the center-of-mass velocities of such binaries are low, too. Only in the case of high common envelope efficiency ($\alpha_\mathrm{CE}\gtrsim 3$), a few tens of long-lived high-velocity binaries can be produced in core-collapse
supernovae.
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High Energy Astrophysical Phenomena
Radiation Pressure Instability-Driven Variability of Line-Driven Disk Winds in AGNs: Connection to Periodic Luminosity Variations and UFO Appearance
Yutaro Kuroda, Ken Ohsuga, Mariko Nomura et al. (+1 more)
We investigated the temporal variability of line-driven disk winds induced by radiation pressure instability in
accretion disks surrounding supermassive black holes. This is the first study to self-consistently couple one-dimensional hydrodynamic simulations of
accretion disks with two-dimensional radiation hydrodynamic simulations of line-driven winds and to analyze their time-dependent
evolution. Our results show that periodic luminosity oscillations caused by radiation pressure instability lead to corresponding changes in both the mass outflow rate and the covering factor of gas expected to be observed as ultra-fast outflows (UFOs), with a delay comparable to the viscous timescale around the wind base. The viewing angles from which UFOs are expected to be observed also change with time. Our results therefore imply that, depending on the viewing angle, UFOs may not be detected even during high-luminosity states, whereas they may be detected even at lower luminosities. These findings are consistent with observations showing that UFOs are not always detected at high luminosities and can sometimes be detected even at lower luminosities. For a black hole mass of $10^{7.4}M_\odot$, a mass
accretion rate of $1.3L_{\rm Edd}/c^2$ at a radius of about 100 Schwarzschild radii, a viscosity parameter of $\alpha=0.1$, and a viscosity prescription parameter of $\mu=0.45$, the mass outflow rate shows a delay of approximately 2–5 yr relative to the luminosity variation, and the covering factor consequently reaches a maximum of $\sim 30\%$ from the high-luminosity phase through the declining phase. Our results suggest that the intermittent detection of UFOs in luminosity-variable AGNs can be explained by radiation pressure instability driven variability of the line-driven disk winds.
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All authors Yutaro Kuroda, Ken Ohsuga, Mariko Nomura, Kenya Watarai
High Energy Astrophysical Phenomena
Supernova nucleosynthesis: a review
Shuai Zha, Yudong Luo and Zhanwen Han
Supernovae are major drivers of
cosmic chemical
evolution. They synthesize heavy elements and disperse them into the interstellar medium via their explosion shocks. Light elements are converted into heavier ones during both presupernova
evolution and the explosive event itself.
Supernova explosions generate nucleosynthesis environments rich in
neutrons,
protons, and
neutrinos under unique thermodynamic conditions, which can enable the production of heavy elements beyond iron. Modern numerical simulations are constructing increasingly realistic explosion models of various
supernova channels, providing more accurate nucleosynthesis conditions and chemical yields. In tandem with advances in large-scale spectroscopic surveys delivering precise, high-resolution stellar abundance data, as well as isotopic ratios from presolar grains and meteorites, our understanding of the
supernova role in
cosmic nucleosynthesis is poised to advance significantly. We review recent progress in modeling various
supernova channels, with particular emphasis on nucleosynthesis yields derived from state-of-the-art simulations. We examine the roles of Type Ia, core-collapse, electron-capture, and pair-instability
supernovae in producing intermediate-mass, iron-peak, trans-iron, and very heavy elements, as well as their characteristic chemical imprints. We also outline major theoretical uncertainties that affect yield predictions. We intend this review to serve as a timely reference for theoretical model development and a practical guide for interpreting observational abundance data.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Bridging Between Statistical Mechanics and Black Hole Evolution: Theoretical Formalism
Suvodip Mukherjee
Black holes in the Universe span nearly ten orders of magnitude in mass over a large
cosmic timescale, dating back to at least the Universe's early history, when it was only a few hundred million years old. The formation and
evolution of these objects remain a mystery because no direct probe can trace each black hole across the full mass range and
cosmic time. This work shows, for the first time, a statistical mechanical description of black hole
evolution. I show that though each black hole and its
evolution are governed by
stochastic processes, one can make a macroscopic description of the distribution function of black holes in the Universe, and its
evolution over the entire mass range and
cosmic time can be expressed in terms of the Kramers-Moyal expansion. This bridging between statistical mechanics and black hole
evolution in terms of the Kramers-Moyal expansion enables the discovery of the underlying physical processes that play a role in the
evolution of black holes. In the future, the application of this technique to data accessible from different messengers, such as gravitational waves and electromagnetic waves, which probe black holes in the Universe, can lead to a data-driven understanding of the underlying physical processes by this statistical mechanics technique despite the ignorance of the underlying microscopic
stochastic processes.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Charging of rotating black holes: kinetic simulations of black hole magnetospheres
Martin Kološ, Farukh Abdulkhamidov, Arman Tursunov et al. (+2 more)
Whether a rotating black hole (BH) immersed in an external
magnetic field charges up to the Wald value $Q_{\rm W}=2aMB$, where $M$ and $a$ are the BH mass and
spin parameter, and $B$ is the strength of the external field, is a long-standing open question in BH electrodynamics, with consequences for charge separation, particle acceleration and the structure of BH magnetospheres. We address it with axisymmetric general-relativistic particle-in-
cell simulations performed with GRZeltron, including self-consistent pair creation. For representative values of the BH
spin, we evolve the same asymptotically uniform Wald field from two opposite initial horizon charges, $Q_{0}=0$ and $Q_{0}=Q_{\rm W}$, and track the accumulated charge through the BH horizon. We find that both branches relax within a few tens of gravitational times to the same saturated charge value. Thus, the
equilibrium is a dynamical attractor of the kinetic magnetosphere rather than a
memory of the initial data. The attractor lies well below $Q_{\rm W}$, at $\xi_{\rm eq}\equiv Q_{\rm eq}/Q_{\rm W}\approx 0.3$ for $a\lesssim0.7$, then falling almost to $\xi_{\rm eq}\approx0$ for large
spins $a\approx1$. We derive an analytic expression for $\xi_{\rm eq}$ by requiring equal
magnetic fluxes through the horizon associated with positive and negative charges, and find its
spin dependence to be in agreement with the simulations. The charge state of an astrophysical BH is therefore driven by kinetic
plasma processes, and the Wald charge is an upper bound, not a general
equilibrium value. Since $\xi_{\rm eq}<1$, charging does not quench the horizon-infinity potential drop that powers energy-extraction processes such as the Blandford-Znajek mechanism.
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All authors Martin Kološ, Farukh Abdulkhamidov, Arman Tursunov, Jorge A. Rueda, Benoît Cerutti