Astrophysics of Galaxies
Jet-driven shocks and turbulence in radio-loud Active Galactic Nuclei observed with JWST MIRI/MRS
Rogemar A. Riffel, Gabriel L. Souza-Oliveira, Luis Colina et al. (+34 more)
Jet-cloud interactions are a key manifestation of Active
Galactic Nucleus (AGN) feedback on
nuclear scales, distinct from the large-scale
radio-mode feedback that suppresses gas cooling in
galaxy halos. On these smaller scales,
radio jets can inject energy and momentum into the interstellar medium (ISM), shaping the physical and kinematic properties of the
nuclear and circumnuclear regions of
galaxies. Using JWST MIRI/MRS observations of seven nearby
radio-loud AGN (3C293, 3C305, Centaurus A, Cygnus A, IC5063, NGC1052, and M87), we investigate jet-driven
turbulence in both the warm molecular and ionized gas phases. By combining spatially resolved H$_2$/PAH flux ratios with diagnostic line ratios of the ionized gas, we constrain the dominant H$_2$ excitation processes and assess the impact of
radio jet–ISM interactions on the multiphase gas. We find that
radio jets drive enhanced
turbulence in both molecular and ionized (traced by [FeII], [NeII] and [NeIII] lines) gas, not only along but also perpendicular to the jet axis, indicating that jet–ISM interactions extend beyond the collimated jet channel and affect the
nuclear environment. Strong correlations between the H$_2$/PAH ratio, the H$_2$ excitation temperature, and shock-sensitive ionized-gas tracers indicate that jet-driven shocks dominate the excitation of the H$_2$ rotational lines in most sources. These results indicate that
radio jets are a key driver of multiphase ISM kinematics and excitation in nearby
radio-loud
galaxies.
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All authors Rogemar A. Riffel, Gabriel L. Souza-Oliveira, Luis Colina, Almudena Alonso-Herrero, Marina Bianchin, Kalliopi M. Dasyra, Lorenzo Evangelista, Kameron Goold, Pierre Guillard, Rogério Riffel, Anil Seth, Thaisa Storchi-Bergmann, Nadia Zakamska, Samile Araujo-Santos, Anelise Audibert, Enrica Bellocchi, Steph Campbell, Françoise Combes, Guilherme S. Couto, José Henrique Costa-Souza, Richard I. Davies, Maitê S. Z. de Mellos, Tanio Díaz-Santos, Fergus R. Donnan, Ismael García-Bernete, Santiago García-Burillo, Laura Hermosa Muñoz, Erin K. S. Hicks, Alvaro Labiano, Enrique Lopez-Rodriguez, Vincenzo Mainieri, Christopher Packham, Miguel Pereira Santaella, Cristina Ramos Almeida, Claudio Ricci, Lucas Ramos Vieira, Vivian U
High Energy Astrophysical Phenomena
Is XRISM/Resolve probing a "raining" absorber in Mrk 509?
M. Dadina, V. Missaglia, V. Braito et al. (+19 more)
X-ray spectroscopy of AGN offers unique insights into the reprocessing of radiationand gas dynamics near SMBH. The Sey 1
galaxy Mrk 509 is an ideal laboratory for these studies since its complex FeK$\alpha$ in emission and the past evidences of transient and fast flows. We present the first high-resolution 2-12 keV spectrum of Mrk 509 obtained with the Resolve calorimeter on-board XRISM, complemented with XMM-Newton and NuSTAR observations to constrain the broadband continuum. We modeled the spectra using self-consistent reflection models for the continuum and emission lines, and photoionized
plasma models for the absorption components. The XRISM/Resolve spectrum reveals a narrow FeK$\alpha$ core resolved with $\sigma \sim 10 eV$ (v$_{FWHM} \sim$ 1100 km/s) and a broader component with $\sigma \sim 450 eV$. We also find tentative evidence (3.6$\sigma$) for a ionized absorber. The data suggest that this component is infalling with a velocity of $v_{in} \sim 11000$ km/s and that it is located within few thousands gravitational radii. The narrow FeK$\alpha$ emission is consistent with an origin in the dusty
torus, while the broad component arises from the inner BLR or in the
accretion disk (R$\sim 30--120 r_g$). Relativistic reflection modeling indictaes the inner edge if the emitting disk to R$\geq 27 r_g$. If confirmed, the high velocity inflow would likely represent fragmented clumps of a "failed wind" raining onto the
accretion disk. providing potential direct evidence that non-standard
accretion processes coexist with canonical disk-like flows in the inner regions of AGNS.
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All authors M. Dadina, V. Missaglia, V. Braito, M. Cappi, A. Luminari, D. Barret, E. Bertola, S. Bianchi, A. Comastri, G. Chartas, J. Kaastra, E. Kammoun, G. Lanzuisi, G. Matzeu, R. Middei, E. Nardini, F. Nicastro, Pierre-Olivier Petrucci, C. Pinto, R. Serafinelli, A. Tortosa, C. Vignali
Astrophysics of Galaxies
A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE). XXI. Statistical properties of individual HII regions in perturbed galaxies
A. Boselli, M. Fossati, Y. Roehlly et al. (+8 more)
We use narrow-band Halpha+[NII] imaging data gathered during VESTIGE, a blind survey of the Virgo cluster carried out with MegaCam at the CFHT, to identify HII regions in 385
galaxies showing ionised gas emission. We identify 76645 HII regions in 322
star-forming
galaxies and study their physical properties for those above the completeness limit (L(Ha)>=10^37 erg s-1). The present work is focused on perturbed cluster
galaxies, identified as those having a reduced amount of HI when compared to similar objects in the field. We derive composite luminosity functions, diameter and electron density distributions, and several scaling relations, and compare them to those already derived for gas-rich, unperturbed systems identified during the VESTIGE survey. The analysis shows that the statistical and physical properties of HI gas-deficient cluster
galaxies are different from those of unperturbed systems, with perturbed objects having a steeper faint-end slope and a brighter characteristic Ha luminosity than gas-rich
galaxies. The difference in the two distributions comes principally from the outer disc (outside the effective radius). The analysis of the scaling relations indicates that perturbed objects have a lower number of HII regions per unit
stellar mass and disc surface than unperturbed systems, with differences increasing with the HI-deficiency parameter, principally in the outer disc where HII regions are less present in gas-poor systems. All these differences can be explained in the framework of
galaxy evolution in rich environments, where their hydrodynamic interaction with the surrounding ICM (ram pressure) removes the gas outside-in quenching the
star formation activity in the outer disc once the HI is removed.
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All authors A. Boselli, M. Fossati, Y. Roehlly, M. Boquien, J. Braine, P. Cote, J.C. Cuillandre, B. Epinat, L. Ferrarese, S. Gwyn, G. Hensler
High Energy Astrophysical Phenomena
ENGRAVE follow-up of a type IIb supernova spatially coincident with the sub-threshold gravitational wave trigger S250818k
K. Ackley, M. T. Botticella, A. Boye et al. (+54 more)
The candidate gravitational wave (GW) event S250818k was one of only three non-retracted LIGO-Virgo-KAGRA public alerts issued during the fourth observing run of the network (O4) with a binary
neutron star (BNS) merger classification probability exceeding one percent. This triggered a
prompt search for a potential electromagnetic (EM) counterpart in the large localisation error region (949 deg$^2$ projected in the sky at 90% credible level). The transient SN2025ulz, discovered by the Zwicky Transient Facility (ZTF) during the search, attracted a great deal of
attention due to a potential spatial and temporal coincidence, and due to its initial fast decay and featureless spectrum. Here, we report on the follow up of this transient by the Electromagnetic counterparts of gravitational wave sources at the Very Large
Telescope (ENGRAVE) Collaboration. We conducted an extensive multi-wavelength observational campaign, which led to the spectral classification of the transient as a type IIb
supernova (SN), indicating that it is unrelated to the candidate GW event. In this article, we describe our observing strategies, data reduction, and interpretation. All of our results confirm and strengthen our classification of the source, and also show that shock cooling tails associated with type IIb SNe are one of the most prominent contaminants in kilonova searches.
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All authors K. Ackley, M. T. Botticella, A. Boye, M. Branchesi, G. Bruni, E. Cappellaro, S. Chaty, T.-W. Chen, F. D'Ammando, V. D'Elia, F. F. De Pasquale, Dimple, R. A. J. Eyles-Ferris, M. Fraser, G. Gianfagna, J. H. Gillanders, G. Greco, M. Gromadzki, C. P. Gutièrrez, A. Hajela, L. Izzo, P. G. Jonker, S. Kobayashi, R. Kotak, G. P. Lamb, G. Leloudas, A. J. Levan, J. D. Lyman, K. Maguire, A. Martin-Carrillo, A. Melandri, M. J. Michałowski, S. R. Oates, F. Onori, B. Patricelli, E. Pian, G. Pignata, S. Piranomonte, L. Piro, Q. Pognan, M. L. Pumo, S. Ronchini, A. Rossi, R. Roy, A. Saccardi, O. S. Salafia, R. Salvaterra, N. Sarin, S. Schulze, S. J. Smartt, R. L. C. Starling, D. Steeghs, N. R. Tanvir, A. L. Thakur, S. D. Vergani, S. Yi, D. R. Young
Earth and Planetary Astrophysics
Astrochemical Inheritance of Terrestrial Planets Water from Local Wet Silicates
Lise Boitard-Crépeau, Stefano Pantaleone, Cecilia Ceccarelli et al. (+3 more)
The delivery of water to the inner
Solar System rocky
planets, including Earth, remains debated, as standard models assume that they formed from dry grains, inside the snowline of the protosolar nebula. However, a recent work showed that a not-negligible amount of water formed during the prestellar phase could have been retained by pebbles and planetesimals at the Earth's orbit in enough quantities to reproduce its water content. This study was based based on
quantum mechanics (QM) calculations of the binding energy (BE) of water on amorphous ice and on a kinetic approach. Here, we present new QM calculations of the BE of water frozen on the surface of silicate grains, and show that it is on average about twice larger than that on the amorphous ice. The contribution of this first layer of frozen water increases the
dust temperature at which frozen water can be retained. This provides a local source of water not only for the Earth, but also for the inner rocky
planets. The predictions from our model are in agreement with the available estimates of water content in terrestrial
planets. This suggests that water delivery from the outer
Solar System may not be required.
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All authors Lise Boitard-Crépeau, Stefano Pantaleone, Cecilia Ceccarelli, Pierre Beck, Lydie Bonal, Piero Ugliengo
Astrophysics of Galaxies
Using Ly$\alpha$ Transmitted Spectrum to Probe IGM Transmission and Identify Ionized Structures in Cosmic Reionization
Weida Hu, Casey Papovich, Lu Shen et al. (+16 more)
We present a study of intergalactic medium (IGM) transmission at $4.5 < z < 6.5$ using high-signal-to-noise JWST/NIRSpec prism spectroscopy of 143
galaxies at $5<z<7$ from the CAPERS and JADES surveys. By comparing the observed flux blueward of Ly$\alpha$ emission line to the prediction of spectral energy distribution modeling, we directly measure the IGM transmission along the individual
galaxy sightlines. The average transmission measured from these
galaxy sightlines is consistent with previous measurements based on luminous
quasars. Current NIRSpec spectroscopy is sufficiently deep to probe IGM transmission on single sightlines. We find evidence for a highly ionized structure, \bubble, at $z\sim 5.75-6$ in the GOODS-S field based on the analysis of a high-S/N spectrum of one
galaxy, GS-18846, at $z=6.335$. The IGM transmission of GS-z6IS is $0.17\pm0.02$, an order of magnitude higher than the average of previous measurements at this
redshift. This structure has a line-of-sight scale of $\sim110$ cMpc and spatially extends over at least $21\times17$ cMpc$^2$. GS-z6IS is associated with a known large-scale
galaxy overdensity at the same
redshift, whose member
galaxies show enhanced Ly$\alpha$ visibility and a broader Ly$\alpha$ equivalent width distribution compared to field
galaxies at similar
redshift. This result supports the interpretation that Ly$\alpha$ overdensity can trace bubbles of increased IGM transmission, although environmental effects on
galaxy properties may also contribute. Our study demonstrates that high-S/N
galaxy spectra offer a powerful new approach to tracing ionized structures during the epoch of reionization.
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All authors Weida Hu, Casey Papovich, Lu Shen, Pablo Arrabal Haro, Bren E. Backhaus, Nikko J. Cleri, Mark Dickinson, James S. Dunlop, Steven L. Finkelstein, Mauro Giavalisco, Anton M. Koekemoer, Vasily Kokorev, Sara Mascia, Lorenzo Napolitano, Laura Pentericci, Aaron Smith, Anthony J. Taylor, Xin Wang, L. Y. Aaron Yung
Astrophysics of Galaxies
Unravelling the complex structure of the Fe II emission region in Type 1 active galactic nuclei
Jelena Kovačević-Dojčinović, Ivan Dojčinović and Luka Č. Popović
Using a large sample of Type 1 AGN spectra, we investigated the complex structure of the Fe II emission region in order to understand the atomic processes responsible for the enhancement of the Fe II emission. We explored correlations between Fe II features and other spectral parameters, with special focus placed on the
quasar main sequence, whose underlying physics is crucial for understanding the origin of the strong Fe II emission. The Fe II emission was modelled using the flexible Fe II template that decomposes the optical Fe II lines into several line groups. According to the atomic properties of transitions, the Fe II lines were divided into inconsistent and consistent groups (Fe II$_{incons}$ and Fe II$_{cons}$), while Fe II$_{cons}$ lines were additionally decomposed into components originating from different parts of the broad-line region (Fe II$_{ILR}$ and Fe II$_{VBLR}$). We traced the behaviour of these line groups and components along the
quasar main sequence. Anti-correlation between the equivalent width (EW) of Fe II and the FWHM of Fe II appears to be a more fundamental relation underlying the
quasar main sequence. The increase in the EW Fe II for smaller line widths is primarily caused by the strengthening of the EW Fe II$_{incons}$ lines and, with a smaller contribution, by the enhancement of the EW Fe II$_{ILR}$ components, while the EW of Fe II$_{VBLR}$, on average, does not significantly change along the
quasar main sequence. The results indicate a possible stratification of the Fe II emission region occurring in sources with strong Fe II emission. An increased Eddington ratio may modify the broad-line region structure, leading to specific physical conditions suitable for triggering additional atomic processes. This may result in the appearance of Fe II$_{incons}$ lines and FeII$_{ILR}$ components, which consequently increase the optical Fe II strength.
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Astrophysics of Galaxies
Morphological and Star Formation Properties of Cosmic Noon Massive Quiescent Galaxies
Vaidik Prasal, Yogesh Wadadekar, Pralay Biswas et al. (+1 more)
We analyze the
star formation and morphological properties of massive quiescent
galaxies at
cosmic noon ($2 < z < 3$) in the Abell 2744 field, using deep JWST NIRCam broadband and medium-band imaging from the UNCOVER Treasury program and the MegaScience survey, complemented by archival HST data. Using BAGPIPES SED modeling, we select 14 unique massive quiescent
galaxies ($M_* \gtrsim 10^{10}$ M$_\odot$, $\mathrm{sSFR} < 0.2/t_\mathrm{age}$). Morphological analysis with statmorph and pysersic reveals that most
galaxies are intermediate type or S0s with a median Sérsic index $n \sim 4$, consistent with bulge-dominated systems. This value remains constant over $z \sim 1.5$–$4$, indicating that the morphology of massive
galaxies is linked to their quiescence since at least $z \sim 4$. Spatially resolved SED modeling with piXedfit shows that 11 out of 14
galaxies exhibit positive radial sSFR gradients, providing direct evidence for inside-out quenching, with the mean sSFR increasing by $\sim2$ dex from $R/R_e = 0.5$ to $4.5$. Formation time ($t_{50}$) profiles confirm that inner regions formed $\approx 0.5$ Gyr earlier, on average, than the outer regions, and quenching timescale profiles show that the cores were quenched more rapidly than the outskirts. Most
galaxies are compact, with a mean half-mass radius of $R_e = 1.95 \pm 0.13$ kpc. The observed inside-out quenching pattern is consistent with quenching driven by AGN feedback, while the bulge-dominated morphologies suggest morphological quenching may also contribute.
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All authors Vaidik Prasal, Yogesh Wadadekar, Pralay Biswas, Rashi Jain
High Energy Astrophysical Phenomena
Modeling large glitches with core superfluidity in a Hybrid star
Yogeesh N., Anil Kumar and Monika Sinha
Many
pulsars exhibit a peculiar behaviour in their pulse profile of a sudden increase in their rotational period, which is popularly known as a
pulsar glitch. Some of them show
giant glitches with relative amplitude $\Delta\Omega/\Omega \sim 10^{-6}-10^{-5}$. With the model of pinned
neutron vortices inside the
neutron star (NS) crust, this large glitch cannot be explained so far. However, the increasing evidence of massive
pulsars indicates the appearance of exotic degrees of freedom in the inner core of the
pulsars. Given this, we consider the
pulsar as a hybrid
star (HS). This model opens up the possibility of
vortex-pinning inside the core. Under the Gibbs
equilibrium conditions, it is possible for
hadrons and the
quark phase to coexist. Due to the global charge neutrality condition,
quark pasta structures are formed in the background of hadronic matter. We consider these pasta structures as pinning sites of superfluid
vortices. We show that considering the core contribution, our calculations come to be of the order of $\Delta\Omega/\Omega \sim 10^{-6}$, which is close to the observations shown by the Vela-like
pulsars.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Testing General Relativity Through Gravitational Wave Classification: A Convolutional Neural Network Framework
Lavinia Heisenberg, Shayan Hemmatyar and Hector Villarrubia-Rojo
We present a machine learning framework for testing general relativity (GR) with gravitational wave signals from binary black hole mergers. Using the source parameters of 173 BBH events from the GWTC catalog as a realistic astrophysical population, we generate simulated GR waveforms and construct beyond GR (BGR) waveforms by applying controlled phase deformations. We introduce a response function formalism that provides a systematic framework for quantifying how any observable responds to modifications of GR. We train convolutional neural networks (CNNs) on two input representations: whitened waveforms and a response function type observable derived from the waveform mismatch, which isolates the effect of phase deviations from the bulk signal. Using response functions as the CNN input improves the classification sensitivity by a factor of approximately 33 compared to whitened waveforms, demonstrating that the choice of observable representation is as important as the classifier architecture. We study the fundamental limits of this classification through Bayes optimal error analysis, averaging methods that reveal coherent patterns hidden in noise, and a comparison between CNN accuracy and a single feature classifier as a proxy for human performance. At all deformation scales, the CNN outperforms the best single feature approach. We extend the framework to physically motivated theories using the parameterized post Einsteinian (ppE) formalism and apply it to massive
gravity, where the classifier detects deviations for graviton masses of order $m_g \sim 10^{-23}\;\mathrm{eV}/c^2$ with aLIGO design sensitivity.
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Cosmology and Nongalactic Astrophysics
Investigating cosmic distance duality and dark energy evolution through intermediate and high-z probes
Anna Chiara Alfano
We investigate deviations from the
cosmic distance duality relation adopting model-dependent and -independent approaches using i) a Taylor expansion, ii) a power-law parameterization, iii) a logarithmic correction, iv) a (2;1) Padé
polynomial and v) a second order Chebyshev parameterization. We derive constraints on all parameters using observational Hubble data,
galaxy clusters, type Ia
supernovae, DESI data and gamma-ray bursts. Through Monte-Carlo Markov chain analyses adopting the Metropolis Hastings
algorithm, we find no significant violation of duality, then model selection criteria favor flat scenarios even though a slight
curvature is not totally ruled out. For the $H_0$ tension we find a preference at $1$-$\sigma$ for $h^R_0=0.730\pm0.010$ from
supernovae when dropping DESI data and for $h^P_0=0.674\pm 0.005$ from Planck when using DESI and gamma-ray bursts.
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Solar and Stellar Astrophysics
The chemical fingerprint of the Gaia BH3 system. Evidence for early cluster enrichment from the analysis of 51 elements
Gregory Vanden Broeck, Thibault Merle, Nhat Tan Mai et al. (+5 more)
The
Gaia BH3 system hosts the most massive known
stellar-origin black hole and a low-mass metal-poor companion whose chemical composition may constrain early explosive nucleosynthesis processes. We investigate the chemical abundances of the companion in order to constrain the formation of this remarkable system. We perform a detailed analysis of high-resolution ESO-UVES spectra of the companion. 51 elements from lithium to uranium were investigated through spectral synthesis, including 15 treated in NLTE. We compare the resulting pattern to r-process enriched
stars, to nucleosynthesis models and to
stars of the ED-2 stream. The abundance pattern of the BH3 companion is consistent with that of r-I
stars and is well reproduced by a combination of core-collapse
supernova yields and an r-process component. The chemical patterns of four ED-2
stars closely match that of the companion especially when a dilution is taken into account. The present analysis provides the most detailed chemical characterisation of a metal-poor
star associated with a
stellar-mass black hole. The chemical similarity with ED-2
stars argue against local pollution across the binary system. The abundances instead reflect early spatially inhomogeneous enrichment of the progenitor cluster.
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All authors Gregory Vanden Broeck, Thibault Merle, Nhat Tan Mai, Sophie Van Eck, Stephane Goriely, Lionel Siess, Alain Jorissen, Do Thi Hoai
Instrumentation and Methods for Astrophysics
Design, Testing, and Commissioning of the Sun Yat-sen University (SYSU) 80 cm Infrared Telescope
Zhong-Nan Dong, Bin Ma, Chun Chen et al. (+23 more)
The Sun Yat-sen University (SYSU) 80 cm
telescope is a new generation near-infrared (NIR) facility in China dedicated to time-domain astronomy, while also serving as a testbed for emerging NIR cameras. Commissioned in October 2024 at the 4100 m Lenghu site on the Tibetan Plateau in China, the
telescope adopts a reflective Cassegrain design with two Nasmyth foci for J and K bands. The J band imaging system, initially equipped with a 640 x 512 off-the-shelf InGaAs camera (INS Mars640) and upgraded in June 2025 to a 1280 x 1024 science-grade, deeply cooled camera (YNAOIR), achieves background-limited performance with a dark current of ~ 14 e-/s/pix and a readout noise of ~ 11 e-. The system reaches a limiting magnitude of J ~ 17 mag (Vega system) in single 20 s exposures and depths of J ~ 19.4 mag with stacked 30 minute exposures. For a variable with J ~ 14 mag during on-sky tests, the system delivers millimagnitude-level photometric precision. Since commissioning, the
telescope observed transients such as gamma-ray bursts (GRBs),
supernovae and comets, variables including active
galactic nuclei (AGNs), high-
redshift quasars (z > 6), and brown
dwarfs, as well as deep-field imaging reaching J ~ 20.5 mag. This validates the feasibility of using InGaAs cameras for astronomical observations, encouraging other institutions to develop dedicated infrared
telescopes or integrate infrared cameras into existing optical
telescopes.
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All authors Zhong-Nan Dong, Bin Ma, Chun Chen, Wei-Sen Huang, Jin-Ji Li, Jia-Qi Lin, Yun Shi, Hao-Ran Zhang, Duo-Le Cao, Bao-Gang Chen, Tai-Ran Deng, Rui-Chen Gao, Yi Hu, Hong-Zhuang Li, Xia Li, Pu Lin, Yang Liu, Bo Ma, Rong-Feng Shen, Li-Duo Song, Fang-Yu Xu, Hao-Nan Yang, Yan Yu, Jun Yuan, Xiang-Tao Zeng, Hao-Yuan Zheng
High Energy Astrophysical Phenomena
The Impact of the Magnetised Cosmic Web on Ultra High Energy Cosmic Ray Propagation
Allegra Firinu, Franco Vazza and Carmelo Evoli
The origin of ultra-high-energy
cosmic rays (UHECRs) remains an open question. Extragalactic
magnetic fields can modify their propagation and, at sufficiently low energies, suppress the observed flux through the
magnetic horizon (MH) effect.} {We quantify the impact of the MH on the propagation of UHECR
protons using cosmological simulations and a dedicated numerical framework that follows
cosmic rays in a time-evolving background.} {We use UMAREL, a parallel code developed for this study, to propagate UHECR
protons through a cosmological volume simulated with ENZO. The
magnetic-field configurations are chosen to be consistent with recent
radio constraints on
magnetic fields in
cosmic-web filaments. Unlike stationary approaches, we follow particle trajectories through a sequence of time-evolving snapshots and compare the resulting arrival properties with those in an unmagnetised reference model.} {We find that observationally motivated extragalactic
magnetic fields progressively suppress the flux of arriving
protons below \(E \lesssim 3 \times 10^{19}\,\mathrm{eV}\) through an effective
Magnetic Horizon (MH). We estimate \(R_{\mathrm{MH}} \sim 50\,\mathrm{Mpc}\) for
protons with \(E = 10^{18}\,\mathrm{eV}\) and \(R_{\mathrm{MH}} \sim 150\,\mathrm{Mpc}\) for
protons with \(E = 10^{19}\,\mathrm{eV}\).} {The MH generated by extragalactic
magnetic fields must be taken into account when modelling UHECR propagation and interpreting the spectrum observed in the local Universe.}
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Earth and Planetary Astrophysics
The first detection of an atmosphere on a trans-Neptunian object beyond Pluto
Ko Arimatsu, Fumi Yoshida, Tsutomu Hayamizu et al. (+4 more)
Trans-Neptunian objects (TNOs) in the outer
Solar System are predominantly small, icy worlds long presumed to be atmosphereless except for the largest bodies. Until now, Pluto has been unique among TNOs in exhibiting a substantial atmosphere (nitrogen with trace methane and carbon monoxide) at microbar pressure levels. All other known TNOs, including ~ 1000-km-sized bodies such as Eris, Haumea, Makemake, and Quaoar, have shown no detectable atmospheres in
stellar occultation observations, with surface pressure upper limits of order 1-100 nanobars. Here we report the first detection of an atmosphere around a TNO besides Pluto. A
stellar occultation by the ~ 250-km-radius plutino (612533) 2002 XV93 on 10 January 2024 revealed a refractive signature, indicating the presence of a thin atmosphere. The derived surface pressure is 100-200 nanobars, i.e. approximately a hundred times lower than Pluto's and yet significantly above previous limits for other larger bodies. This discovery provides the first evidence that even a sub-1000-km TNO can retain an atmosphere, challenging current paradigms of volatile retention. Our findings indicate that a fraction of distant icy minor
planets can exhibit atmospheres possibly caused by ongoing cryovolcanic activity or a recent impact event of a small icy object.
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All authors Ko Arimatsu, Fumi Yoshida, Tsutomu Hayamizu, Satoshi Takita, Katsumasa Hosoi, Takafumi Ootsubo, Jun-ichi Watanabe
Earth and Planetary Astrophysics
Mean tropical year length at arbitrary ecliptic longitude
Daniel Quigley
We compute the mean interval between successive returns of the apparent geocentric
solar longitude $\lambda$ to a fixed value $L \in \{0^\circ, 45^\circ, 90^\circ, \ldots, 315^\circ\}$, averaged over a multi-millennium window; this gives eight “mean years” against which calendar leap rules can be tuned: four cardinal-point years (equinoxes and solstices); four cross-quarter years. The construction is built on Meeus's low-precision
solar theory (Astronomical
Algorithms, 2nd ed., 1998), itself a low-order truncation of Newcomb's Tables of the Sun re-expanded around J2000.0. Where Meeus presents
polynomial coefficients without justification, we draw on Smart's Textbook on Spherical Astronomy (6th ed., revised by Green, 1977) for the underlying derivations. Numerical accuracy is validated against the cardinal-point intervals tabulated in Meeus, More Mathematical Morsels, 2002. We close with a derivation of the secular drift equation, showing that, regardless of how well a leap rule is tuned, the slow shrinkage of the tropical year produces a quadratic cumulative error that reaches one day in $\sim$5{,}700 years for any fixed intercalation rule.
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Solar and Stellar Astrophysics
Low-luminosity Wolf-Rayet stars: a model-data comparison
Siyu Wu, Zhi Li and Yan Li
A growing number of
Galactic Wolf-Rayet (WR)
stars, in particular WC and transitional WN/C (WNC) objects, have been reported at comparatively low luminosities. If confirmed, these low-luminosity WR
stars provide stringent tests of
stellar-
evolution models, because their HR-diagram locations and surface compositions are highly sensitive to internal mixing and to the adopted WR-phase mass-loss history.We examine whether the HR-diagram positions and wind properties of low-luminosity WC/WNC
stars can be reproduced by single-
star evolutionary tracks at approximately
solar metallicity, and we identify cases where additional channels (e.g. binary stripping) or dominant systematic uncertainties are likely required. Low-luminosity WNC/WC
stars offer sensitive leverage on WR mixing and mass-loss prescriptions. A staged model-data comparison shows that revised WR winds can alleviate the luminosity-side tension for faint WCL
stars, but the simultaneous requirements of temperature, surface composition, and WR-like wind density remain important. The WNC
stars provide the strongest evidence that additional mixing, stripping, or binary-related channels may be required.
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High Energy Astrophysical Phenomena · Cross-listed from physics.plasm-ph
Distributions of particles accelerated by strong Alfvénic turbulence
Stanislav Boldyrev, Daniel Humphrey, Vadim Roytershteyn et al. (+1 more)
This work presents a model for generating nonthermal power-law tails of particles' energy probability density functions in turbulent collisionless
plasmas, applicable to both non-relativistic and relativistic scenarios. We propose that strong Alfvénic
turbulence energizes
plasma particles through
curvature acceleration, particularly for particles with Larmor radii comparable to the scales of
turbulence. When the energy density of the energized particles increases, the efficiency of the energy exchange process diminishes. As a result, the acceleration process saturates, leading to power-law distributions of particle momentum and energy. In the non-relativistic case, the momentum probability density function scales as $f(p) dp \propto p^{-3} dp $, while in the ultrarelativistic case, the energy probability density function scales as $ f(\gamma) d\gamma \propto \gamma^{-3} d\gamma $, where $\gamma$ is the Lorentz factor. This model provides a unified framework for understanding particle acceleration in both energy regimes, complementing existing analytical approaches. The predicted scalings are consistent with available observations of energetic ion distributions in the heliosphere and with the findings from numerical simulations of ultrarelativistic particle acceleration in magnetically dominated
plasma turbulence.
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All authors Stanislav Boldyrev, Daniel Humphrey, Vadim Roytershteyn, Cristian Vega
Solar and Stellar Astrophysics
A Search for Variability of Ultracool Dwarfs with the Zwicky Transient Facility
Haomiao Huang, Shu Wang, Xiaodian Chen et al. (+2 more)
Rotationally modulated photometric variability of ultracool
dwarfs encodes key information about cloud structure and temperature contrasts. Large homogeneous optical
datasets are crucial for linking atmospheric heterogeneity to fundamental parameters such as rotation, mass, and age. We present a search for rotation periods in ultracool
dwarfs using Zwicky Transient Facility (ZTF) optical light curves. By propagating the coordinates to the ZTF epoch and applying Lomb-Scargle analysis, we identified 226 periodic variables, including 32 robust detections and 194 tentative cases. Among the robust detections, 12 have no previously published periods, while 20 have literature counterparts, most of which are consistent with the published values. Most robust detections are M
dwarfs, reflecting the optical sensitivity limits of ZTF. We find a trend of decreasing periods toward later spectral types in relatively old
dwarfs (> 100 Myr), suggesting faster rotation for late-M types than for mid-M types. The age-period relation of our sample is broadly consistent with angular-momentum-conservation models at higher-mass regime of brown
dwarfs, consistent with the M-
dwarf bias of our catalog. Many additional candidates remain to be confirmed due to sparse sampling or low S/N. Future high-cadence, multi-wavelength monitoring and systematic mining of ZTF and upcoming surveys will be crucial for validating these periods, extend sensitivity to later (L/T) types, and better connect rotation with cloud physics across the
stellar-substellar boundary.
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All authors Haomiao Huang, Shu Wang, Xiaodian Chen, Zhijun Tu, Jifeng Liu
High Energy Astrophysical Phenomena
Hadronic Scenario for Galactic PeVatron LHAASO J1912+1014u Supported by Fermi-LAT $\gamma$-ray Data and FUGIN CO Data
Tsunefumi Mizuno, Hidetoshi Sano, Takeru Murase et al. (+3 more)
LHAASO has reported 43 sub-PeV $\gamma$-ray sources, which are promising candidates for
cosmic-ray (CR) accelerators above the PeV energy, commonly called as PeVatrons. Multi-wavelength observations are crucial for identifying the underlying particle species and estimating the CR energy content of these sources. In this work we investigate the region around LHAASO J1912+1014u (and HESS J1912+101) using
Fermi-LAT $\gamma$-ray data and FUGIN CO data. We analyzed 15 years of
Fermi-LAT data in the 0.4–409.6 GeV energy range. By improving the standard
Fermi-LAT diffuse emission model, we significantly reduced the large residuals around the source in the 1.6-12.8 GeV band. We detected a statistically significant excess above the diffuse background, which likely represents $\ge$10 GeV emission associated with the LHAASO/H.E.S.S. source. The GeV excess exhibits a hard spectrum (
photon index of about 2.1) and is well reproduced by interstellar gas templates with systemic velocities of about 25 $\mathrm{km~s^{-1}}$ or 60 $\mathrm{km~s^{-1}}$. We performed a comprehensive fit to the GeV–TeV spectral energy distribution. Although a leptonic scenario can reproduce the observed spectrum, a hadronic scenario is favored once electron cooling is considered. The inferred CR
proton spectrum has an index of $\sim$2.2, and the total CR
proton energy above 1 GeV is (1–5) $\times 10^{49}~\mathrm{erg}$, depending on the assumed velocity range of the associated interstellar gas. A stringent upper limit on diffuse X-ray emission further supports the
proton PeVatron scenario.
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All authors Tsunefumi Mizuno, Hidetoshi Sano, Takeru Murase, Tomohiko Oka, Hiromasa Suzuki, Naohito Nakahara
Cosmology and Nongalactic Astrophysics
Beyond collective fluctuations: probing micro-image swarms in lensed quasars with intensity interferometry
Ashish Kumar Meena and Prasenjit Saha
Each strongly lensed image of a
quasar behind a
lensing galaxy (or
galaxy cluster) is composed of a swarm of micro-images. This is a result of microlensing due to
stellar-scale substructure in the lens. The presence of microlenses forms a network of micro-caustics, and a source transiting these micro-caustics gives rise to variation in observed strongly lensed images. These micro-image swarms are currently observable only through collective intensity fluctuations, which hide the underlying information on the
stellar (and compact dark matter, if any) mass functions within the swarm. To unlock the information present in micro-image swarms, it is necessary to explore new techniques. In this work, we study the prospects of determining the micro-image swarm size in lensed
quasar images using the intensity interferometry (i.e., the Hanbury Brown & Twiss effect). We consider QSO 2237+0305 and PS J0147+4630, two of the brightest lens
quasars in the sky, and study micro-image swarm features in visibility space for both macro-minimum and macro-saddle-point images. At the end, we argue that, with ongoing and expected technical advances, observations of micro-image swarms are plausible, at least for the brightest lensed
quasars.
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Cosmology and Nongalactic Astrophysics
Constraints on Ultralight Scalar and Dark Photon Dark Matter from PPTA-DR3 and EPTA-DR2
Xiao-Song Hu, Siyuan Chen, Kuo Liu et al. (+18 more)
The cold dark matter model successfully describes the Universe on large scales, yet faces challenges at sub-
galactic scales. Ultralight dark matter (ULDM), with particle masses around $10^{-22} \mathrm{eV}$, offers a promising solution to these small-scale issues.
Pulsar Timing Arrays (PTAs), designed to detect nanohertz gravitational waves, can also provide a sensitive probe for ULDM signals. In this work, we perform a
Bayesian search for ULDM using PTA data sets, focusing on two types of signals: the oscillatory gravitational potential from scalar ULDM and the fifth-force interaction mediated by dark
photon dark matter (DPDM). We incorporate
pulsar distances in the analysis to better model the ULDM density. No statistically significant evidence for ULDM has been found, therefore we place 95% confidence-level upper limits on the relevant parameters. For scalar ULDM, our analysis does not exclude the scenario in which ULDM constitutes all of dark matter. The constraints from PPTA-DR3 show significant improvements over the earlier PPTA-DR2 (2018 Preview) across most of the mass range, and are consistent with the recent uncorrelated limits from other PTAs. We also present for the first time the DPDM constraints using EPTA data. The obtained bounds on the DPDM from the EPTA-DR2 and PPTA-DR3 are comparable to existing constraints.
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All authors Xiao-Song Hu, Siyuan Chen, Kuo Liu, Xingjiang Zhu, Shi-Yi Zhao, Wu Jiang, John Antoniadis, N. D. Ramesh Bhat, Amodio Carleo, Shi Dai, Valentina Di Marco, Huanchen Hu, Wenhua Ling, Yang Liu, Saurav Mishra, Christopher J Russell, Ryan M. Shannon, Clemente Smarra, Jingbo Wang, Lin Wang, Andrew Zic
Astrophysics of Galaxies
Fragmentation in the Serpens/Aquila Star-forming Region
Samuel Fielder, Helen Kirk, Michael Dunham et al. (+1 more)
We present a population study of Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 6 observations of the 100 most gravitationally unstable dense cores in Aquila using a simple mass versus size analysis. We identify 66 continuum sources from ALMA 12m observations at 106GHz and through comparisons with known protostellar catalogs; two of these detected dense cores appear to be completely starless, without any accompanying/nearby protostar detections. Additionally, we find nine other starless ALMA 12m detections within protostellar cores that have fragmented into a mixture of starless and protostellar substructures. We test the turbulent core collapse model by conducting synthetic observations of turbulent magnetohydrodynamical simulations of collapsing starless cores in order to predict how many starless cores should be detected given their central density and density profile. The simulations predict at least one (1.19) detection, consistent with our two detections of ALMA 12m emission within completely starless cores. We also use a combination of ALMA Compact Array Cycle 4 observations and the Herschel Gould Belt Survey data to analyze how mass is distributed on three distinct spatial scales, in order to understand how
turbulence shapes the
evolution of substructure development as dense cores collapse to form new
star systems. We find an increase in multiplicity at the smallest scales when the parent larger-scale structure also has a higher degree of fragmentation.
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All authors Samuel Fielder, Helen Kirk, Michael Dunham, Stella Offner
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Helicity-dependent corrections to black-hole shadows from the gravitational spin Hall effect
C. A. S. Almeida
Black-hole shadows are purely
geometric in the leading-order
geometric-optics approximation: their boundary is set by null geodesics and carries no information about the polarization of the probing radiation. At subleading order, the gravitational
spin Hall effect of light introduces helicity-dependent corrections to
photon propagation. We show that, in any static spherically symmetric spacetime, an exact equatorial reflection
symmetry of the full
spin Hall equations forces these corrections to cancel at the capture threshold: the critical impact parameter remains identical for opposite helicities, and no polarization-dependent shadow splitting occurs. Rotation breaks this
symmetry. Using a double perturbative expansion in the black-hole
spin $\chi = a/M$ and in the inverse frequency $1/\omega$, we derive the first non-vanishing helicity-dependent shift of the critical impact parameter for slowly rotating (Kerr) black holes. The effect is linear in $\chi$, scales as $1/\omega$, and appears as a $\cos\phi$ modulation of the shadow boundary, with a sign reversal on one side of the image for
spins $\chi \gtrsim 0.21$. Although parametrically small for astrophysical sources, the splitting is a robust, model-independent signature of
spin-optical dynamics in strong fields. Our analysis also identifies a methodological pitfall: a naive radial projection that suppresses transverse motion can produce a spurious splitting even in spherical
symmetry, a lesson of general relevance for future studies of
spin-optical effects.
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