High Energy Astrophysical Phenomena 30
☆ Mapping the Perseus Galaxy Cluster with XRISM: Gas Kinematic Features and their Implications for Turbulence
Congyao Zhang, Irina Zhuravleva, Annie Heinrich, Elena Bellomi, Nhut Truong, John ZuHone, Eugene Churazov, Megan E. Eckart, Yutaka Fujita, Julie Hlavacek-Larrondo, Yuto Ichinohe, Maxim Markevitch, Kyoko Matsushita, François Mernier, Eric D. Miller, Koji Mori, Hiroshi Nakajima, Anna Ogorzalek, Frederick S. Porter, Ayşegül Tümer, Shutaro Ueda, Norbert Werner
In this paper, we present extended gas kinematic maps of the Perseus cluster
by combining five new XRISM/Resolve pointings observed in 2025 with four
Performance Verification datasets from 2024, totaling 745 ks net exposure. To
date, Perseus remains the only cluster that has been extensively mapped out to
~0.7$r_{2500}$ by XRISM/Resolve, while simultaneously offering sufficient
spatial resolution to resolve gaseous substructures driven by mergers and AGN
feedback. Our observations cover multiple radial directions and a broad
dynamical range, enabling us to characterize the intracluster medium kinematics
up to the scale of ~500 kpc. In the measurements, we detect high velocity
dispersions ($\simeq$300 km/s) in the eastern region of the cluster,
corresponding to a nonthermal pressure fraction of $\simeq$7-13%. The velocity
field outside the AGN-dominant region can be effectively described by a single,
large-scale kinematic driver based on the velocity structure function, which
statistically favors an energy injection scale of at least a few hundred kpc.
The estimated turbulent dissipation energy is comparable to the gravitational
potential energy released by a recent merger, implying a significant role of
turbulent cascade in the merger energy conversion. In the bulk velocity field,
we observe a dipole-like pattern along the east-west direction with an
amplitude of $\simeq\pm$200-300 km/s, indicating rotational motions induced by
the recent merger event. This feature constrains the viewing direction to
~30$^\circ$-50$^\circ$ relative to the normal of the merger plane. Our
hydrodynamic simulations suggest that Perseus has experienced at least two
energetic mergers since redshift z~1, the latest associated with the radio
galaxy IC310. This study showcases exciting scientific opportunities for future
missions with high-resolution spectroscopic capabilities (e.g., HUBS, LEM, and
NewAthena).
comment: 15 pages, 17 figures, submitted to A&A
☆ Tycho supernova exploded inside a planetary nebula (SNIP)
I examine recent observations of the type Ia supernova remnant (SNR Ia) Tycho
and conclude that Tycho is an SN Ia inside a planetary nebula (SNIP). The
observations reveal two opposite protrusions, termed ears, projected on the
main shell of Tycho. The pair of ear structures resembles that of the SNRs Ia
Kepler, SNR G299-2.9, and SNR G1.9+0.3, which earlier studies considered as
SNIPs. The requirement that the explosion occurs within hundreds of thousands
of years after the formation of the planetary nebula (by the second star to
evolve) makes the core-degenerate scenario the most likely for Tycho. Several
other possible scenarios lead to an SNIP, but they are unlikely for Tycho. The
identification of Tycho as an SNIP leads to two general conclusions. (1) The
fraction of SNIPs among normal SNe Ia is very large, ~70-90%. Namely, the vast
majority of normal SNe Ia are SNIPs. (2) To accommodate the large fraction of
SNIPs, the delay time distribution of normal SNe Ia includes not only the
stellar evolution timescale (as usually assumed), but also includes pockets of
younger stellar populations in galaxies without ongoing star formation; the
SNIPs come from the younger stellar populations in galaxies.
comment: It will be submitted in two days to allow for comments (including
missing references)
☆ The Influence of the Accretion Disc Structure on X-ray Spectral States in Symbiotic Binaries
Symbiotic stars are binary systems where a white dwarf (WD) accretes material
from the wind of an evolved, late-type companion. X-ray-emitting symbiotic
systems are classified into $\alpha$, $\beta$, $\delta$, and $\beta/\delta$
types, attributed to distinct physical mechanisms such as thermonuclear
burning, wind interactions, and accretion-driven boundary layers. We present
synthetic X-ray spectra derived from hydrodynamics simulations using the
PHANTOM code, coupled with radiative-transfer calculations from SKIRT. We
reproduce all X-ray spectral types by exploring different density structure of
the accretion disc, the viewing angle, the plasma temperature of the boundary
layer, and/or the presence of extended emission. The synthetic X-ray spectra
consist of both absorbed and reflected components. In systems with massive,
high-column density discs and viewing angles close to edge-on, the reflected
continuum can dominate the X-ray emission. This effect is less pronounced in
systems with low-mass, lower-column density discs. We explore i) systems going
from $\delta$ to $\beta$ states, ii) $\delta$-types that become $\beta/\delta$
sources, iii) the variability of the three Fe emission lines in the 6.0-7.0
energy range, and iv) the possible physical processes behind the $\alpha$
sources. The observations from iconic symbiotic systems are discussed in line
of the present models. Our framework offers predictive power for future X-ray
monitoring and provides a path toward connecting accretion disc physics with
observed spectral states in symbiotic binaries with accreting WDs.
comment: 12 pages, 12 figures; Accepted to MNRAS
☆ Energy calibration of LHAASO-KM2A using the cosmic ray Moon shadow
We present a precise measurement of the westward, rigidity-dependent shift of
the Moon's shadow using three and a half years of cosmic-ray data collected by
the Kilometer Square Array (KM2A) of the Large High Altitude Air Shower
Observatory (LHAASO). These measurements enable us to calibrate the detector
energy response in the range 20-260 TeV, with results showing excellent
agreement with the response derived from Monte Carlo (MC) simulations of the
KM2A detector. We also measure a best-fit parameter $\epsilon = 0.015 \pm
0.08$, corresponding to a 95% confidence interval of [-14%, +17%] for the
energy-scale estimation. This result establishes the exceptional accuracy of
the KM2A-MC in simulating the detector's response within this energy range.
comment: 12 pages, 13 figures, 2 tables
☆ High-energy photons from Gamma-Ray Bursts, but no neutrinos
The Cannon-Ball model of Gamma-Ray Bursts and their afterglows--described in
the text and in innumerable previous occasions--is extremely successful and
predictive. In a few intrinsically bright GRBs, gamma-rays with energies in the
TeV range have been observed. The CB model, I argue, has no difficulty in
describing the origin and approximate properties of these high-energy gamma
rays and the extreme difficulty of observing their accompanying neutrinos.
comment: 8 pages, 13 figures
☆ JWST and Keck Observations of the Off-Nuclear TDE AT 2024tvd: A Massive Nuclear Star Cluster and Minor-Merger Origin for its Black Hole
Kishore C. Patra, Ryan J. Foley, Nicholas Earl, Kyle W. Davis, Enrico Ramirez-Ruiz, V. Ashley Villar, Sebastian Gomez, K. Decker French, Kirsty Taggart, Prasiddha Arunachalam, Phillip Macias, Ravjit Kaur, Samaporn Tinyanont
We present JWST/NIRSpec and NIRCam observations of the first optically
selected off-nuclear tidal disruption event (TDE), AT 2024tvd, along with
Keck/KCWI integral field unit spectroscopy. The spectra show broad H and He
emission lines that are characteristic of a TDE. Stellar kinematics show smooth
host-galaxy morphology and ordered bulge rotation, with no evidence of
disturbances in velocity, dispersion, age or metallicity space. We construct
the first quasi-simultaneous spectral-energy distribution (SED) from X-rays to
infrared for a TDE and decompose it into three components: the TDE accretion
flow, an unresolved nuclear star cluster (NSC), and heated dust emission. The
accretion component implies a black hole mass of $\log(M_\bullet/M_\odot) =
5.50\pm 0.04$, an instantaneous super-Eddington accretion rate of $\log
(\dot{M}/M_{\odot} yr^{-1}) = -1.22 \pm 0.04$, and an outer disk photosphere
radius of $\log(r_{out}/r_{g}) = 3.8 \pm 0.1$. The dust emission is well
described by a blackbody with $T_{dust} = 873\pm 15$ K and peak luminosity
$\log (L_{dust}/erg$ $s^{-1}) = 40.80\pm 0.01$, consistent with a dust echo
near the sublimation radius. The SED is best fit when including additional
stellar emission above the galaxy background at the TDE location, corresponding
to $\log(M_{\star}/M_\odot) = 7.97^{+0.16}_{-0.26}$, which we interpret as a
massive NSC or an ultra-compact dwarf galaxy. These results support a
minor-merger origin for the MBH responsible for the TDE over scenarios
involving gravitational recoil or dynamical ejection from the nucleus.
comment: 22 pages, 9 figures, comments welcome
☆ Modeling gamma-ray signatures of particle acceleration in stellar clusters from GeV to PeV
Young massive stellar clusters (YMSCs) have recently regained interest as
PeVatron candidates, potentially accounting for the cosmic-ray (CR) knee as
alternatives to isolated supernova remnants (SNRs). LHAASO's unique capability
to detect photons above 0.1 PeV, hence tracing multi-PeV CRs, can provide
critical constraints on galactic acceleration models when combined with
H.E.S.S. and Fermi-LAT data. We investigate the transport of particles from
YMSCs acceleration sites, namely wind termination shocks (WTS) or embedded
SNRs, to nearby dense molecular clouds where proton-proton interactions produce
high-energy gamma rays. We determine the necessary conditions, such as the
distance between the acceleration site and the target, or the cluster's power
and age, for detectable gamma-ray excesses and identify viable systems through
parameter space exploration. By comparing with observations, we can constrain
key physical parameters including WTS efficiency, diffusion coefficient and
injection slope. Our analysis also examines whether some of LHAASO's
unidentified sources might correspond to such cluster-cloud systems.
comment: 8 pages, 3 figures, ICRC proceeding
☆ Gamma-rays from Wolf-Rayet stellar winds
Gamma-ray observations of young star clusters have recently provided evidence
for particle acceleration occurring at stellar wind termination shocks, fueled
by the mechanical energy of stellar winds from massive stars. In this work, we
explore the possibility that the wind from a single powerful star, whether
isolated or part of a cluster, can alone provide sufficient energy to generate
gamma-ray emission detectable by current instruments. This scenario is
particularly relevant given that a significant fraction of Wolf-Rayet (WR)
stars are not found within clusters. To investigate this, we compiled a large
sample of WR stars and ranked them based on their wind luminosity divided by
the square of their distance, a proxy for their potential gamma-ray flux. We
then searched for spatial coincidences between the most promising candidates
and cataloged gamma-ray sources. This analysis leads us to propose associations
between the stars WR14, WR110, WR111, and WR114 and several unidentified
gamma-ray sources. These results suggest that WR stellar winds could represent
a distinct and previously unrecognized population of gamma-ray emitters.
comment: 8 pages, 2 figures, ICRC proceeding
☆ The double neutron star PSR J1946+2052 I. Masses and tests of general relativity
Lingqi Meng, Paulo C. C. Freire, Kevin Stovall, Norbert Wex, Xueli Miao, Weiwei Zhu, Michael Kramer, James M. Cordes, Huanchen Hu, Jinchen Jiang, Emilie Parent, Lijing Shao, Ingrid H. Stairs, Mengyao Xue, Adam Brazier, Fernando Camilo, David J. Champion, Shami Chatterjee, Fronefield Crawford, Ziyao Fang, Qiuyang Fu, Yanjun Guo, Jason W. T. Hessels, Maura MacLaughlin, Chenchen Miao, Jiarui Niu, Ziwei Wu, Jumei Yao, Mao Yuan, Youlin Yue, Chengmin Zhang
We conducted high-precision timing of PSR J1946+2052 to determine the masses
of the two neutron stars in the system, test general relativity (GR) and
assessed the system's potential for future measurement of the moment of inertia
of the pulsar. We analysed seven years of timing data from the Arecibo 305-m
radio telescope, the Green Bank Telescope (GBT), and the Five-hundred-meter
Aperture Spherical radio Telescope (FAST). The data processing accounted for
dispersion measure variations and relativistic spin precession-induced profile
evolution. We employed both DDFWHE and DDGR binary models to measure the spin
parameters, kinematic parameters and orbital parameters. The timing campaign
has resulted in the precise measurement of five post-Keplerian parameters,
which yield very precise masses for the system and three tests of general
relativity. One of these is the second most precise test of the radiative
properties of gravity to date: the intrinsic orbital decay, $\dot{P}_{\rm
b,int}=-1.8288(16)\times10^{-12}\rm\,s\,s^{-1}$, represents $1.00005(91)$ of
the GR prediction, indicating that the theory has passed this stringent test.
The other two tests, of the Shapiro delay parameters, have precisions of 6\%
and 5\% respectively; this is caused by the moderate orbital inclination of the
system, $\sim 74^{\circ}$; the measurements of the Shapiro delay parameters
also agree with the GR predictions. Additionally, we analysed the higher-order
contributions of $\dot{\omega}$, including the Lense-Thirring contribution.
Both the second post-Newtonian and the Lense-Thirring contributions are larger
than the current uncertainty of $\dot{\omega}$
($\delta\dot{\omega}=4\times10^{-4}\,\rm deg\,yr^{-1}$), leading to the
higher-order correction for the total mass.
comment: 12 figures and 3 tables, accepted for publication in A&A
☆ DIPLODOCUS II: Implementation of transport equations and test cases relevant to micro-scale physics of jetted astrophysical sources
DIPLODOCUS (Distribution-In-PLateaux methODOlogy for the CompUtation of
transport equationS) is a novel framework being developed for the general
transport of particle distribution functions through the seven dimensions of
phase space, including forcing terms and interactions between particles.
Following Paper I, which details the background analytic framework, this second
paper provides an overview of the numerical implementation in the form of the
code package Diplodocus.jl, written in Julia, including the description of a
novel Monte-Carlo sampling technique for the pre-computation of anisotropic
collision integrals. In addition to the discussion of numerical implementation,
a selection of test cases are presented to examine the package's capabilities.
These test cases focus on micro-scale physical effects: binary collisions,
emissive interactions and external forces that are relevant to the modelling of
jetted astrophysical sources, such as Active Galactic Nuclei and X-Ray
Binaries.
comment: 26 pages, 24 figures, submitted to Physical Review D
☆ Enhanced Localization of Dark Lensed Gravitational Wave Events Enables Host Galaxy Identification and Precise Cosmological Inference
Lensed gravitational wave (GW) events are expected to be powerful new probes
of cosmology, contingent on redshift measurement by electromagnetic
observations. Host galaxy identification is thus crucial but challenging due to
poor localization by GW signal alone. In this paper, we show that the
third-generation ground-based GW detectors will detect a population of lensed
events with three or more detectable images (including the central one), each
arriving at distinct times and Earth locations in the space, forming an
effective network that reduces the typical localization area to $\sim0.01$
deg$^2$. For at least $90\%$ (or $50\%$) of these events, the localization
improves by more than a factor of $10$ (or $30$) comparing with unlensed cases.
Such precise localization and multiple-image detections enable robust
host-galaxy identification and, through lens modelling, further yield
sub-arcsecond position. As ``dark lensed sirens", these events become powerful
probes of cosmological parameters. Using simulated lensed compact-binary
mergers, we show that two-year or longer observations with third-generation GW
detectors can measure the Hubble constant to $\lesssim1$\% precision via ``dark
lensed sirens" (even when relying solely on lensed stellar-mass binary black
hole events), while simultaneously constraining other cosmological parameters.
This approach will provide an independent, complementary avenue for measuring
cosmological parameters.
comment: 23 pages, 8 figures, accepted for publication in Astrophysical
Journal Letters
☆ Optically thick winds of very massive stars suppress intermediate-mass black hole formation
Intermediate-mass black holes (IMBHs) are the link between stellar-mass and
supermassive black holes. Gravitational waves have started unveiling a
population of IMBHs in the $\sim 100-300 \, \mathrm{M_{\odot}}$ range. Here, we
investigate the formation of IMBHs from very massive stars (VMSs, $>100\,{}
\mathrm{M_{\odot}}$). We calculate new VMS models that account for the
transition from optically thin to optically thick winds, and study how this
enhanced mass loss affects IMBH formation and the black hole mass function at
intermediate and high metallicity ($Z=10^{-4}-0.02$). We show that optically
thick winds suppress the formation of IMBHs from direct VMS collapse at
metallicities $Z>0.001$, one order of magnitude lower than predicted by
previous models. Our models indicate that the stellar progenitors of GW231123
must have had a metallicity $Z<0.002$, if the primary black hole formed via
direct VMS collapse.
comment: 10 pages, 7 figures. Comments welcome
☆ Lanthanide Impact on the Infra-Red Spectra of Nebular Phase Kilonovae
Nebular phase kilonovae (KNe) have significant infra-red (IR) emission
thought to be mostly forbidden emission lines from rapid neutron capture
(r-process) species in neutron star merger ejecta. Lanthanide elements in
particular have complex atomic structures with many IR transitions. Using
non-local thermodynamic equilibrium (NLTE) radiative transfer simulations, we
explore the impact of lanthanides on the IR spectra of KNe in the nebular
phase, exploring a parameter space of ejecta mass and lanthanide fraction. We
find that lanthanide impact is greater at higher densities, corresponding to
earlier epochs and greater ejecta masses. The wavelengths most affected are
found to be $\lambda \lesssim 4~\mu$m, with the species Ce\,\textsc{iii} and Nd
\textsc{ii} being the most important contributors to spectral formation. We
also find significant emission from species proposed in observations, notably
Te\,\textsc{iii} at 2.1 $\mu$m, and Se\,\textsc{iii} at 4.5 and 5.7 $\mu$m,
while W\,\textsc{iii} is subdominant at 4.5 $\mu$m. The Te\,\textsc{iii}
feature at 2.1 $\mu$m is always blended, particularly with Zr\,\textsc{ii},
Ce\,\textsc{iii}, and Nd\,\textsc{ii}. We do not reproduce the smooth
blackbody-like continua observed in AT2023vfi. Based on our results, we argue
that line opacity alone is likely insufficient to produce optically thick
continua in the nebular phase, even in the case of lanthanide/actinide-rich
ejecta, as our models are optically thin in the IR at these epochs. Given that
lanthanide contributions are dominant below 4 $\mu$m, we suggest that NIR
observations best probe these elements, while MIR spectroscopy with
\textit{JWST} can reliably probe non-lanthanide emission even in relatively
lanthanide-rich cases.
comment: 25 pages, 15 figures, submitted to MNRAS
☆ Infrared spectral signatures of light r-process elements in kilonovae
Anders Jerkstrand, Quentin Pognan, Smaranika Banerjee, Nicholas Sterling, Jon Grumer, Niamh Ferguson, Keith Butler, James Gillanders, Stephen Smartt, Kyohei Kawaguchi, Blanka Vilagos
A central question regarding neutron star mergers is whether they are able to
produce all the r-process elements, from first to third peak. The high
abundances of first-peak elements (atomic number $Z \sim 31-40$) in the solar
composition means they may dominate the ejecta mass in kilonovae. We here study
theoretical infrared signatures of such light elements with spectral synthesis
modelling. By combining state-of-the-art NLTE physics with new radiative and
collisional data for these elements, we identify several promising diagnostic
lines from Ge, As, Se, Br, Kr and Zr. The models give self-consistent line
luminosities and indicate specific features that probe emission volumes at
early phases ($\sim$10d), the product of ion mass and electron density in late
phases ($\gtrsim$75d), and in some cases direct ionic masses at intermediate
phases. Emission by [Se I] 5.03 \mum\ + [Se III] 4.55 \mum\ can produce
satisfactory fits to the Spitzer photometry of AT2017gfo. However, the models
show consistently that with a Kr/Te and Se/Te ratio following the solar
r-process pattern, Kr + Se emission is dominant over Te for the blend at 2.1
\mum\ observed in both AT2017gfo and AT2023vfi. The somewhat better line
profile fit with [Te III] may suggest that both AT2017gfo and AT2023vfi had a
strongly sub-solar production of the light r-process elements. An alternative
scenario could be that Kr + Se in an asymmetric morphological distribution
generates the feature. Further JWST spectral data, in particular covering the
so far unobserved $>5$ \mum\ region, holds promise to determine the light
r-process production of kilonovae, and in particular whether the light elements
are made in a slow disk wind or in a fast proto-NS outflow. We identify
specific needs for further atomic data on recombination rates and collision
strengths for $Z=31-40$ elements.
comment: Submitted to MNRAS
☆ The probe limit in MHD and its implications for magnetic transport
Many phenomenological and effective field-theoretical (EFT) applications of
magnetohydrodynamics (MHD) in the presence of a background magnetic field
employ a simplifying assumption whereby the electromagnetic and the
energy-momentum fluctuations decouple. In studies of magnetic transport, for
example in magnetic diffusion, the conservation of energy and momentum is then
neglected. In this paper, we investigate the details and the consistency of
this so-called $\textit{probe limit}$ in different parametric regimes of MHD
plasmas. In the first part of the paper, our discussion explores the
hydrodynamic (higher-form) theory of MHD. In the second part, we then
explicitly test the probe limit by using a microscopic holographic (AdS/CFT)
model of a strongly coupled plasma. In the process, we develop the holographic
Schwinger-Keldysh EFT prescription for describing the bulk 2-form fields and
their dual 1-form symmetries. Moreover, we find evidence of a phase transition
at low temperatures and show that magnetic Hall transport can emerge as a
consequence of background charge density that breaks the charge conjugation
symmetry of the state. Finally, we discuss the implications for magnetic
transport, with a particular view towards the dynamics of dense nuclear matter
in neutron stars.
comment: v1: 40+4 pages plus references, 10 figures
☆ Fe XVIII-XXIV K beta Inner-shell Absorption Lines in the X-ray Spectra of Neutron Star and Black Hole Binaries with XRISM
Masahiro Tsujimoto, Daiki Miura, Hiroya Yamaguchi, Ehud Behar, Chris Done, Maria Diaz Trigo, Chamani M. Gunasekera, Peter A. M. van Hoof, Stefano Bianchi, Maryam Dehghanian, Gary J. Ferland
The advent of the X-ray microcalorimeter spectrometer Resolve onboard the
XRISM space telescope opened a new era for high-resolution X-ray spectroscopy
of astrophysical plasmas. Many spectral features were newly detected, including
the K alpha and K beta inner-shell transition lines of mildly ionized (F- to
Li-like) Fe at 6-8 keV in the spectra of X-ray binaries and active galactic
nuclei. The widely used atomic databases contain information on the K alpha but
not K beta lines of these ions. We conducted the atomic structure calculation
using FAC to derive the Fe K alpha and K beta lines and verified the result
against ground experiments and other calculations of the Fe K alpha lines. We
then implemented the Fe K beta lines in a radiative transfer code (cloudy) and
compared the synthesized and observed spectra with XRISM. A reasonably good
agreement was obtained between the observation and the ab initio calculations.
This exemplifies the need to expand the atomic databases to interpret
astrophysical spectra.
comment: 4 pages, 6 figures, accepted for publication in Plasma and Fusion
Research
☆ Spatio-Temporal Evolution of the March 2022 ICME Revealed by Multi-Point Observations of Forbush Decreases
Gaku Kinoshita, Beatriz Sanchez-Cano, Yoshizumi Miyoshi, Laura Rodoriguez-Garcia, Emilia Kilpua, Benoit Lavraud, Mathias Rojo, Marco Pinto, Yuki Harada, Go Murakami, Yoshifumi Saito, Shoichiro Yokota, Daniel Heyner, David Fischer, Nicolas Andre, Kazuo Yoshioka
Interplanetary coronal mass ejections (ICMEs) cause Forbush Decreases (FDs)
effects, which are local decreases in background galactic cosmic rays (GCR).
Even though FDs can be observed with simple particle instruments, their
amplitude and shape provide physical profiles of passing ICMEs. However, in
some cases, previous statistical studies of the heliocentric distance
dependence of FD changes associated with ICME propagation have found no strong
correlation. We need the criteria for evaluating the relationship between ICMEs
structure and FD, necessary for FDs statistical analysis. This study
investigates the effect of evolutions and interactions of ICMEs on FDs profiles
in the inner Solar System, using multipoint comparisons. We focus on multipoint
ICME observations by Solar Orbiter, BepiColombo, and near-Earth spacecraft from
March 10-16, 2022, when these spacecraft were ideally located for studying the
radial and longitudinal evolutions of ICME and accompanying FDs. We compared
GCR variations with the multiple in-situ data and ICME model, clarifying the
correspondence between the evolution of each ICME structure in radial and
azimuthal directions and the depth and gradients of the FD. The radial
comparison revealed decreases in FD intensities and gradients associated with
the expansion of the ICME. The longitudinal difference found in FD intensity
indicates longitudinal variations of the ICMEs shielding effect. These results
suggest that accurate multi-point FD comparisons require determining the
relationship between the observers position and the inner structure of the
passing ICMEs.
comment: 21 pages, 11 figures
♻ ☆ Small Progenitors, Large Couplings: Type Ic Supernova Constraints on Radiatively Decaying Particles
Francisco R. Candón, Damiano F. G. Fiorillo, Hans-Thomas Janka, Bart F. A. van Baal, Edoardo Vitagliano
Supernova (SN) 1987A is a celebrated laboratory in searches for gamma-ray
flashes produced by the radiative decay of sub-GeV particles such as axion-like
particles (ALPs), sterile neutrinos, and novel gauge bosons. At large
couplings, however, particles decay rapidly inside the stellar envelope, which
results in a suppression of the signal. Focusing on the prototypical example of
ALPs with a photon coupling, we show that core-collapse SNe of Type Ic are much
less affected by this attenuation, thanks to the compactness of their
progenitors ensuing from the loss of their envelope. While Fermi-LAT may miss
the brief gamma-ray flash from a single Type Ic SN, their high rate allows for
a statistical approach: by stacking many events, we can obtain constraints that
significantly surpass those from SN 1987A at large couplings. Our approach can
be extended to any feebly interacting particle featuring a decay channel into
photons.
comment: 7+7 pages, 2+5 figures
♻ ☆ DIPLODOCUS I: Framework for the evaluation of relativistic transport equations with continuous forcing and discrete particle interactions
DIPLODOCUS (Distribution-In-PLateaux methODOlogy for the CompUtation of
transport equationS) is a novel framework being developed for the mesoscopic
modelling of astrophysical systems via the transport of particle distribution
functions through the seven dimensions of phase space, including continuous
forces and discrete interactions between particles. This first paper in a
series provides an overview of the analytical framework behind the model,
consisting of an integral formulation of the relativistic transport equations
(Boltzmann equations) and a discretisation procedure for the particle
distribution function (Distribution-In-Plateaux). The latter allows for the
evaluation of anisotropic interactions, and generates a conservative numerical
scheme for a distribution function's transport through phase space.
comment: 16 pages, 7 figures; submitted to Physical Review D; typos corrected,
references added
♻ ☆ JWST Spectroscopy of SN Ia 2022aaiq and 2024gy: Evidence for Enhanced Central Stable Ni Abundance and a Deflagration-to-Detonation Transition
Lindsey A. Kwok, Chang Liu, Saurabh W. Jha, Stéphane Blondin, Conor Larison, Adam A. Miller, Mi Dai, Ryan J. Foley, Alexei V. Filippenko, Jennifer E. Andrews, Moira Andrews, Katie Auchettl, Carles Badenes, Thomas G. Brink, Kyle W. Davis, Andreas Flörs, Lluís Galbany, Or Graur, D. Andrew Howell, Sahana Kumar, Réka Könyves-Tóth, Natalie LeBaron, Colin W. Macrie, Keiichi Maeda, Kate Maguire, Curtis McCully, Nicolas E. Meza-Retamal, Estefania Padilla Gonzalez, Rüdiger Pakmor, Jeniveve Pearson, Anthony L. Piro, Abigail Polin, Nabeel Rehemtulla, César Rojas-Bravo, David J. Sand, Chita Sangkachan, Michaela Schwab, Huei Sears, Mridweeka Singh, Bhagya M. Subrayan, Kirsty Taggart, Tea Temim, Jacco H. Terwel, Samaporn Tinyanont, József Vinkó, Xiaofeng Wang, J. Craig Wheeler, Yi Yang, WeiKang Zheng
We present optical + near-infrared (NIR) + mid-infrared (MIR) observations of
the normal Type Ia supernovae (SN Ia) 2022aaiq and 2024gy in the nebular phase,
continuously spanning 0.35-28 microns. Medium-resolution JWST spectroscopy
reveals novel narrow ($v_{\mathrm{FWHM}}<1500$ km s$^{-1}$) [Ni II] 1.94 and
6.64 micron cores in both events. The MIR [Ni II] 6.64 micron line exhibits a
distinct narrow core atop a broader base, indicating a central enhancement of
stable Ni. This structure points to high central densities consistent with a
near-Chandrasekhar-mass ($M_{Ch}$) progenitor or a high-metallicity
sub-$M_{Ch}$ progenitor. From detailed line-profile inversions of SN 2024gy, we
derive emissivity profiles for stable iron-group elements (IGEs), radioactive
material, and intermediate-mass elements (IMEs), revealing spatially distinct
ejecta zones. The [Ni III] 7.35 micron line shows a shallow-to-steep slope
transition -- a "broken-slope" morphology -- that matches predictions for
delayed detonation explosions with separated deflagration and detonation ashes.
We also reanalyze and compare to archival JWST spectra of SN 2021aefx and the
subluminous SN 2022xkq. We estimate a stable $^{58}$Ni mass of $\sim0.1$
M$_\odot$ for SN 2024gy, consistent with delayed detonation models, and
$\sim0.01$ M$_\odot$ for SN 2022xkq, favoring sub-$M_{Ch}$ scenarios. These
results demonstrate that resolved line profiles, now accessible with JWST,
provide powerful diagnostics of explosion geometry, central density, and
progenitor mass in SN Ia.
comment: 30 pages, 17 figures, 2 tables, submitted to AAS Journals
♻ ☆ Accelerated inference of binary black-hole populations from the stochastic gravitational-wave background
Third-generation ground-based gravitational wave detectors are expected to
observe $\mathcal{O}(10^5)$ of overlapping signals per year from a multitude of
astrophysical sources that will be computationally challenging to resolve
individually. On the other hand, the stochastic background resulting from the
entire population of sources encodes information about the underlying
population, allowing for population parameter inference independent and
complementary to that obtained with individually resolved events. Parameter
estimation in this case is still computationally challenging, as computing the
power spectrum involves sampling $\sim 10^5$ sources for each set of
hyperparameters describing the binary population. In this work, we build on
recently developed importance sampling techniques to compute the SGWB
efficiently and train neural networks to interpolate the resulting background.
We show that a multi-layer perceptron can encode the model information,
allowing for significantly faster inference. We test the network assuming an
observing setup with CE and ET sensitivities, where for the first time we
include the intrinsic variance of the SGWB in the inference, as in this setup
it presents a dominant source of measurement noise.
♻ ☆ A Time-Dependent Solution for GSN 069 Disk Evolution and the Nature of Long-Lived Tidal Disruption Events
We present the implementation of a fully time-dependent relativistic disk
model-based on the light curve fitting package FitTeD-into the X-ray spectral
fitting environment, pyXspec. This implementation enables simultaneous fitting
of multi-epoch and multi-wavelength spectral data, where the only free
parameters are those describing the black hole and the initial conditions,
while the subsequent evolution is governed by the dynamical equations of an
evolving accretion flow. We use it fit seven epochs of X-ray spectra and two
epochs of UV spectra of the 'long-lived' tidal disruption event (TDE) and
quasi-periodic eruption (QPE) source GSN 069, from 2010 through late-2019. Our
results show that such 'long-lived', X-ray-bright TDEs-of which GSN 069 is a
prime, but not unique, example-can naturally be explained within the same
framework as events with shorter-lived X-ray emission, like ASASSN-14li and
AT2019dsg. Their distinction lies in the `viscous' timescale parameter-tied to
the disk's angular momentum transport efficiency-which should be treated as a
free parameter when modeling the disk evolution of transient events. We examine
the implications for QPE models by tracking the time evolution of disk
properties such as mass surface density and accretion rate. We argue that
existing QPE models may not be able to reproduce the observed connection
between the presence (2018) or absence (2014) of eruptions and the disk
properties. In the context of orbiter-disk collision models, the change in mass
surface density appears insufficient to explain the needed variation in the
eruption's temperature. The absence of eruptions in GSN 069 in 2014 remains a
challenge for QPE models.
comment: 25 pages, 13 Figs, +Appendix. Published ApJ. Accepted version
♻ ☆ Hunting Primordial Black Hole Dark Matter in Lyman-$α$ Forest
A very pressing question in contemporary physics is the identity of Dark
Matter (DM). Primordial Black Holes (PBHs) are one of the most well-motivated
DM candidates. Light PBHs have been constrained by either the non-detection of
their Hawking radiation itself, or by the non-observation of any measurable
effects of this radiation on astrophysical and cosmological observables. We
constrain the PBH contribution to the DM density by non-detection of their
Hawking radiation's effect on the intergalactic medium (IGM) temperature
evolution. We use the latest deductions of IGM temperature from Lyman-$\alpha$
forest observations. We put constraints on the fraction of DM as PBHs with
masses $5 \times 10^{15}$ g - $10^{17}$ g, separately for spinning and
non-spinning BHs. We derive constraints by dealing with the heating effects of
the astrophysical reionization sources on the IGM in two ways. In one way, we
completely neglect this heating due to astrophysical sources, thus giving us
weaker constraints, but completely robust to the reionization history of the
universe. In the second way, we utilise some modelling of the ionization and
temperature history, and use it to derive more stringent constraints. We find
that for non-spinning PBHs of mass $10^{16}$ g, the current measurements can
constrain the PBH-density to be $\lesssim$ 0.1\% of the total DM. We find that
these constraints are competitive, and hence provide a new observable to probe
the nature of PBH DM. The systematics affecting Lyman-$\alpha$ forest
measurements are different from other constraining observations, and thus this
is a complementary probe.
comment: v2: 15 pages, 2 Figures. Minor editorial changes, results unchanged.
Published in The European Physical Journal C
♻ ☆ Ultra-long MeV transient from a relativistic jet: a tidal disruption event candidate
Gor Oganesyan, Elias Kammoun, Annarita Ierardi, Alessio Ludovico De Santis, Biswajit Banerjee, Emanuele Sobacchi, Felix Aharonian, Samanta Macera, Pawan Tiwari, Alessio Mei, Shraddha Mohnani, Stefano Ascenzi, Samuele Ronchini, Marica Branchesi
On July 2, 2025, the Gamma-ray Burst Monitor (GBM) onboard the Fermi
Gamma-ray space telescope detected three short-duration MeV transients with
overlapping sky locations. These events, named as GRB 250702D, B, and E
(collectively referred to as DBE), triggered the detector with delays of
approximately 1-2 hours between each burst. Follow-up observations of this
unusually long MeV transient (lasting >3 hours) by the Neil Gehrels Swift
Observatory and the Nuclear Spectroscopic Telescope Array over a period of 10
days revealed a steep temporal decline in soft X-rays ($\propto t^{-1.9 \pm
0.1}$). The time-averaged spectra during the outbursts are well described by a
single power law $dN_{\gamma}/dE \propto E^{-1.5}$, while upper limits above
100 MeV imply a spectral cutoff between 10 MeV and 100 MeV. Using standard
gamma-ray transparency arguments, we derive a lower limit on the bulk Lorentz
factor. Combined with the steep decline in X-rays, these constraints point to a
relativistic jet origin. The properties of DBE are inconsistent with
established GRB spectral-energy correlations, disfavoring classical long GRB
progenitors. Instead, the basic characteristics of DBE resemble those of
previously reported jetted tidal disruption events (TDEs), though alternative
progenitor channels cannot be excluded. In the relativistic TDE scenario, DBE
is the first one with detected MeV gamma-ray emission. We argue that the
observed emission is most likely produced by synchrotron radiation from sub-TeV
electrons.
comment: Accepted for publication in A&A (Letter)
♻ ☆ Radio emission from airplanes as observed with RNO-G
RNO-G Collaboration, :, S. Agarwal, J. A. Aguilar, N. Alden, S. Ali, P. Allison, M. Betts, D. Besson, A. Bishop, O. Botner, S. Bouma, S. Buitink, R. Camphyn, J. Chan, S. Chiche, B. A. Clark, A. Coleman, K. Couberly, S. de Kockere, K. D. de Vries, C. Deaconu, P. Giri, C. Glaser, T. Glüsenkamp, H. Gui, A. Hallgren, S. Hallmann, J. C. Hanson, K. Helbing, B. Hendricks, J. Henrichs, N. Heyer, C. Hornhuber, E. Huesca Santiago, K. Hughes, A. Jaitly, T. Karg, A. Karle, J. L. Kelley, J. Kimo, C. Kopper, M. Korntheuer, M. Kowalski, I. Kravchenko, R. Krebs, M. Kugelmeier, R. Lahmann, C. -H. Liu, M. J. Marsee, Z. S. Meyers, K. Mulrey, M. Muzio, A. Nelles, A. Novikov, A. Nozdrina, E. Oberla, B. Oeyen, N. Punsuebsay, L. Pyras, M. Ravn, A. Rifaie, D. Ryckbosch, O. Schlemper, F. Schlüter, O. Scholten, D. Seckel, M. F. H. Seikh, J. Stachurska, J. Stoffels, S. Toscano, D. Tosi, J. Tutt, D. J. Van Den Broeck, N. van Eijndhoven, A. G. Vieregg, A. Vijai, C. Welling, D. R. Williams, P. Windischhofer, S. Wissel, R. Young, A. Zink
This paper describes how intentional and unintentional radio emission from
airplanes is recorded with the Radio Neutrino Observatory Greenland (RNO-G). We
characterize the received signals and define a procedure to extract a clean set
of impulsive signals. These signals are highly suitable for instrument
calibration, also for future experiments. A set of signals is used to probe the
timing precision of RNO-G in-situ, which is found to match expectations. We
also discuss the impact of these signals on the ability to detect neutrinos
with RNO-G.
♻ ☆ Tidal heating in detached double white dwarf binaries
Short--period ($P<$1 hr orbits) detached double white dwarf binary (DWDB)
components identified with transient surveys (e.g. SDSS, ZTF) have hot surface
temperatures ($>$10,000 K) and observed radii a factor two larger than
completely degenerate white dwarfs. We formulate tidal heating in helium
composition extremely low mass white dwarf (ELM WD) components of detached
DWDBs which reach mass transfer within a Hubble time. We combine a mass radius
relation which varies with surface temperature and the equilibrium tidal
friction model of Hut 1981, where the additional orbital energy loss from tidal
friction is accounted for by increases in the primary surface temperature, and
hence increasing radius. Applying this heating model to the current sample of
binaries with ZTF, we predict temperature increases from the present day of up
to $\sim$40\% before the onset of mass transfer. We find that helium white
dwarfs are generically hot and large at the onset of mass transfer, even for
the oldest DWDBs whose components can cool to be degenerate by the present day.
In the population of Galactic DWDBs, we find that the onset of mass transfer
should occur at orbital periods as long as 1000s (17 minutes), or binary
gravitational wave frequency of 2 mHz. This is over three times longer than
periods expected for degenerate WD (5 minutes). Since mass transferring DWDBs
are progenitors for a variety of transients and stellar populations e.g. RCrB
stars, AM CVn binaries, so-called Type .Ia supernova, the finite temperature of
donor white dwarfs should be taken into account.
comment: 25 pages, 5 figures. Accepted to The Astrophysical Journal
♻ ☆ 1FLAT: a Firmamento-based catalog of AGN in Fermi-LAT high Galactic latitude γ-ray sources
P. Giommi, M. Doro, M. Gouvêa, L. Fronte, F. Metruccio, F. Arneodo, U. Barres de Almeida, S. Di Pippo, T. Kerscher, A. Macció, B. Mazzon, M. Morrone, E. Prandini, A. Rodríguez, A. Ruina, N. Sahakyan, L. Silveri, D. Tripathi
We present a systematic reassessment of 5,062 high-Galactic latitude
gamma-ray sources from the Fermi-LAT 4FGL-DR4 catalog using Firmamento, a
web-based platform for multi-frequency source discovery and analysis. Our goal
is to provide an independent evaluation of LAT gamma-ray source associations
through alternative spectral and spatial methods that combine recent and legacy
survey data, supplemented by human supervision of spectral energy distributions
(SEDs), source morphology, flux variability, and template-based comparisons.
Firmamento confirms the 4FGL-DR4 and 4LAC-DR3 counterparts or unassociated
sources in 4,493 cases (88.8%), demonstrating the robustness of both
approaches. Beyond this general agreement, we identify 421 new blazar
counterparts among previously unassociated sources, thereby reducing the
fraction of unidentified extragalactic Fermi-LAT sources from 25% to 17%. In
addition, in 64 cases we find alternative blazar associations, while in 49
instances we do not confirm the 4FGL-DR4 association. For all confirmed blazar
counterparts we provide homogeneous estimates of synchrotron peak frequency and
peak flux using machine-learning and template-based methods; these agree with
4LAC-DR3 values in most cases, though significant discrepancies appear for a
few dozen sources, often due to improved X-ray coverage. The primary outcome of
this work is the 1st Firmamento LAT AGN table (1FLAT), made publicly available
through the Firmamento platform (https://firmamento.nyuad.nyu.edu), where all
related multi-wavelength data and images are available. The project involved
extensive manual validation and benefited from the active participation of
graduate and undergraduate students, highlighting the platform's value for both
research and education.
comment: Accepted for publication in ApJS. 1FLAT can be accessed here:
https://huggingface.co/datasets/micheledoro/1FLAT.fits
♻ ☆ Splitting the Gravitational Atom: Instabilities of Black Holes with Synchronized/Resonant Hair
Black holes (BHs) with synchronized bosonic hair challenge the Kerr paradigm,
linking superradiance from ultralight fields -- creating gravitational atoms --
to bosonic stars across parameter space. In the ''very hairy'' regime, where a
small horizon lies inside a bosonic star containing most of the energy, they
deviate sharply from Kerr, but their dynamics remain unexplored. We show that
for such solutions the horizon gets naturally ejected from the center of its
scalar environment, and observe a similar dynamics in a cousin model of BHs
with resonant scalar hair, albeit with a different fate. This dynamical
splitting is likely to be generic for sufficiently hairy BHs in the broader
class of models with synchronized or resonant hair, but possible exceptions may
exist.
comment: 8 pages, 9 figures. Submitted version. Modified Fig. 2, updated Figs.
4, 5, 8 and 9. Minor additions and updates to main text
♻ ☆ Resonant W and Z Boson Production in FSRQ Jets: Implications for Diffuse Neutrino Fluxes
Blazars, particularly Flat Spectrum Radio Quasars (FSRQs), are well-known for
their ability to accelerate a substantial population of electrons and
positrons, as inferred from multiwavelength radiation observations. Therefore,
these astrophysical objects are promising candidates for studying high-energy
electron--positron interactions, such as the production of $W^{\pm}$ and $Z$
bosons. In this work, we explore the implications of electron--positron
annihilation processes in the jet environments of FSRQs, focusing on the
resonant production of electroweak bosons and their potential contribution to
the diffuse neutrino flux. By modeling the electron distribution in the jet of
the FSRQ 3C~279 during a flaring state, we calculate the reaction rates for
$W^{\pm}$ and $Z$ bosons and estimate the resulting diffuse fluxes from the
cosmological population of FSRQs. We incorporate the FSRQ luminosity function
and its redshift evolution to account for the population distribution across
cosmic time, finding that the differential flux contribution exhibits a
pronounced peak at redshift $z \sim 1$. While the expected fluxes remain well
below the detection thresholds of current neutrino observatories such as
IceCube, KM3NeT, or Baikal-GVD, the expected flux from the $Z$ boson production
could account for approximately $10^{-3}$ of the total diffuse astrophysical
neutrino flux. These results provide a theoretical benchmark for the role of
Standard Model electroweak processes in extreme astrophysical environments and
emphasize the interplay between particle physics and astrophysics, illustrating
that even rare high-energy interactions can leave a subtle but quantifiable
imprint on the diffuse astrophysical neutrinos.
comment: 21pages, 7 figures, 1 table, submitted to JCAP
♻ ☆ GW250114 reveals black hole horizon signatures
The horizon of a black hole, the "surface of no return," is characterized by
its rotation frequency $\Omega_H$ and surface gravity $\kappa$. A striking
signature is that any infalling object appears to orbit at $\Omega_H$ due to
frame dragging, while its emitted signals decay exponentially at a rate set by
$\kappa$ as a consequence of gravitational redshift. Recent theoretical work
predicts that the merger phase of gravitational waves from binary black hole
coalescences carries direct imprints of the remnant horizon's properties, via a
"direct wave" component that (i) oscillates near $2\Omega_H$, reflecting the
horizon's frame dragging and the quadrupole nature of the gravitational
radiation, and (ii) decays at an increasing rate characterized by $\kappa$,
with additional screening from the black hole's potential barrier. In this
paper, we report observational evidence for the direct wave in GW250114 with a
matched-filter signal-to-noise ratio of $14.0^{+0.2}_{-0.1}$
($13.5^{+0.1}_{-0.2}$) in the LIGO Hanford (Livingston) detector. The measured
properties are in full agreement with theoretical predictions. These findings
establish a new observational channel to directly measure frame-dragging
effects in black hole ergospheres and explore (near-)horizon physics in
dynamical, strong-gravity regimes.
comment: 6+2 pages, 4+1 figures