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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 7 November

High Energy Astrophysical Phenomena

A Mass-Independent Damping Timescale in Black Hole Accretion Systems

Haoyang Zhang, Shenbang Yang, Li Zhang et al. (+1 more)

The scaling laws reveal the underlying structural similarities shared by astrophysical systems across vastly different scales. In black hole accretion systems, the scaling relations between the characteristic damping timescales (CDTs) of light curves and black hole mass offer valuable insights into the underlying physical structure of accretion disks. Here, we investigate the long-term hard X-ray CDTs of 106 black hole and neutron star accretion systems using light curves from the Swift Burst Alert Telescope 157-month catalog. Unexpectedly, for the first time, we discover a mass-independent CDT in these black hole accretion systems, in contrast to well-established scaling laws. This puzzling phenomenon can be attributed to conductive timescales arising from disk–corona interactions, instead of the intrinsic accretion disk processes characterized by scaling laws, and it may further modulate jet emission in blazars. This result demonstrates thermal conduction as a key mechanism driving hard X-ray variability and offers new observational evidence for the disk–corona–jet connection.
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All authors Haoyang Zhang, Shenbang Yang, Li Zhang, Benzhong Dai

Astrophysics of Galaxies

The stellar mass function of quiescent and star-forming galaxies and its dependence on morphology in COSMOS-Web

Marko Shuntov, Olivier Ilbert, Claudia del P. Lagos et al. (+33 more)

We study the stellar mass function (SMF) of quiescent and star-forming galaxies and its dependence on morphology in 10 redshift bins at $0.2<z<5.5$ using the COSMOS2025 catalog built from $0.54 \, {\rm deg}^2$ JWST imaging from COSMOS-Web. Galaxies are selected by type using the $NUVrJ$ rest-frame color diagram and classified morphologically by bulge-to-total light ratio ($B/T$). The quiescent SMF shows rapid early build-up, with the most massive systems (${\rm log}(M_{\star}/{\rm M_{\odot}})\gtrsim11$) assembled by $z\sim1$ and evolving little since. The star-forming SMF evolves more slowly, following a mass-evolution scenario where galaxies grow via star formation and quench at the characteristic mass $\log(M^{*}/{\rm M}_{\odot})\sim10.6$. Bulge systems ($B/T>0.6$) dominate the quiescent SMF at ${\rm log}(M_{\star}/{\rm M_{\odot}})>10$ at all redshifts, while disks ($B/T<0.2$) dominate at ${\rm log}(M_{\star}/{\rm M_{\odot}})<9$. However, most bulge-dominated galaxies are star-forming, with their fraction increasing with redshift and decreasing mass, consistent with being progenitors of quiescent bulges. We find evidence for environmental quenching onset at $z\sim3$ from the upturn in the quiescent SMF at ${\rm log}(M_{\star}/{\rm M_{\odot}})<9.5$, contributed by disk-dominated galaxies consistent with satellite quenching that retains disk morphologies. Number densities of ${\rm log}(M_{\star}/{\rm M_{\odot}})>10$ quiescent galaxies are lower than recent literature by $0.1-0.7$ dex, but agree well with simulations at $2<z<3$. At $z>3$, simulations increasingly underpredict observations. Finally, we build an empirical model describing galaxy number density evolution by parametrizing quenching rates, baryon conversion efficiency, and bulge formation. Our model supports a scenario where star-forming galaxies grow central bulges before quenching in massive halos.
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All authors Marko Shuntov, Olivier Ilbert, Claudia del P. Lagos, Sune Toft, Francesco Valentino, Wilfried Mercier, Hollis B. Akins, Nguyen Binh, Malte Brinch, Caitlin M. Casey, Maximilien Franco, Fabrizio Gentile, Ghassem Gozaliasl, Aryana Haghjoo, Santosh Harish, Michaela Hirschmann, Marc Huertas-Company, Shuowen Jin, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Clotilde Laigle, Joseph S. W. Lewis, Georgios E. Magdis, Henry Joy McCracken, Bahram Mobasher, Thibaud Moutard, Pascal A. Oesch, Louise Paquereau, Alvio Renzini, Michael R. Rich, David B. Sanders, Greta Toni, Laurence Tresse, Andrea Weibel, John R. Weaver, Lilan Yang

Solar and Stellar Astrophysics

Co-existence of Internal Gravity Waves and Tayler-Spruit Magnetic Fields in the Radiative Core of Low-mass Stars

L. Amard and S. Mathis

The Tayler-Spruit dynamo (TSD) is able to generate a small-scale magnetic field in the differentially rotating stably stratified layers of stars and was recently observed in numerical simulations. In parallel, the propagation of internal gravity waves in stars can be modified in the presence of a magnetic field. Here we first want to estimate the interaction between a magnetic field generated by the TSD and internal gravity waves in the radiative core of low-mass stars. This allows us to then characterise the effect of this interplay on the observed standing modes spectrum and on the internal transport of angular momentum by progressive waves. To do this, we use the STAREVOL evolution code to compute the structure of low-mass rotating stars along their evolution. In particular, we implement a formalism to describe the TSD and estimate the regions where the generated magnetic field is strong enough to change the identity of internal gravity waves to magneto-gravity waves. In addition, we evaluate the possible limitation of angular momentum transport by the combined action of rotation and magnetism. We show that along the pre-main sequence and main-sequence evolution, the lowest frequencies of the excited gravity wave spectrum could be converted to magneto-gravity waves by the magnetic field generated by the TSD. During the red-giant branch we find that most of the excited spectrum of progressive internal gravity waves could be converted into magneto-gravity waves in the very central region.
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Solar and Stellar Astrophysics

On the possibility of using decayless kink oscillations of coronal loops to forecast powerful solar flares and coronal mass ejections

A.B. Nechaeva, I.V. Zimovets, I.N. Sharykin et al. (+1 more)

This work investigates the decayless kink oscillations of solar coronal loops and examines possible changes in their behaviour in active regions (ARs) before powerful solar flares (M- and X-class) and in the absence of powerful flares. To this end, we analysed 14 ARs with powerful flares and 14 ARs without powerful flares. For each event, images obtained in the 171 Åand 94 ÅAIA/SDO channels with 12-second cadence for 4 hours before the flare were retrieved and analysed. For ARs without powerful flares, arbitrary time intervals of similar duration were considered for comparison. Since the decayless oscillations have a very low amplitude (1-2 AIA/SDO pixels), we used the Motion Magnification technique to amplify the amplitude of these oscillations. Time-distance maps were constructed from the processed images in the 171 Åchannel, from which oscillatory patterns were extracted 'manually'. Wavelet analysis was performed to check for changes in the oscillation period. No systematic changes were found. No obvious differences in the behaviour of oscillations in ARs with and without powerful flares were detected either. Additional information was obtained on coronal mass ejections (CMEs) from ARs in the vicinity of the time intervals under consideration. Based on the results of the analysis of a small sample of events, we came to the preliminary conclusion that the registration and analysis of decayless kink oscillations of high (~ 100-600 Mm) coronal loops based on this methodology is not promising for predicting powerful flares and CMEs.
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All authors A.B. Nechaeva, I.V. Zimovets, I.N. Sharykin, S.A. Anfinogentov

Solar and Stellar Astrophysics

High-spectral Resolution, Multi-wavelength Center-to-limb Observations of the Sun

Meetu Verma, Carsten Denker, Alexander G. M. Pietrow et al. (+2 more)

The center-to-limb variations (CLVs) of photospheric and chromospheric spectral lines were obtained in 2025 July and August using drift scans from the echelle spectrograph of the 0.7 m Vacuum Tower Telescope at the Observatorio del Teide (ODT) in Tenerife, Spain. This instrument can observe four spectral regions simultaneously, enabling multi-line spectroscopy with high spectral resolution of various activity features and the quiet Sun in the lower solar atmosphere. The initial results of Halpha observations demonstrate the diagnostic potential of drift scans obtained with a ground-based, high-resolution telescope. Data products include spectroheliograms and maps of physical parameters such as line-of-sight velocity, line width, and line-core intensity. The combination of the CLV from photospheric and chromospheric lines, as well as the wide range of formation heights of the selected lines, renders this dataset ideal for characterizing stellar and exoplanet atmospheres.
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All authors Meetu Verma, Carsten Denker, Alexander G. M. Pietrow, Robert Kamlah, Dominique J. M. Petit dit de la Roche

Earth and Planetary Astrophysics

Upper limits on atmospheric abundances of KELT-11b and WASP-69b from a retrieval approach

F. Lesjak, L. Nortmann, D. Cont et al. (+18 more)

WASP-69b and KELT-11b are two low-density hot Jupiters, which are expected to show strong atmospheric features in their transmission spectra. Such features offer valuable insights into the chemical composition, thermal structure, and cloud properties of exoplanet atmospheres. High-resolution spectroscopic observations can be used to study the line-forming regions in exoplanet atmospheres and potentially detect signals despite the presence of clouds. We aimed to detect various molecular species and constrain the chemical abundances and cloud deck pressures using high-resolution spectroscopy. We observed multiple transits of these planets with CARMENES and applied the cross-correlation method to detect atmospheric signatures. Further, we used an injection-recovery approach and retrievals to place constraints on the atmospheric properties. We detected a tentative H$_2$O signal for KELT-11b but not for WASP-69b, and searches for other molecules such as H$_2$S and CH$_4$ resulted in non-detections for both planets. By investigating the signal strength of injected synthetic models, we constrained which atmospheric abundances and cloud deck pressures are consistent with our cross-correlation results. In addition, we show that a retrieval-based approach leads to similar constraints of these parameters.
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All authors F. Lesjak, L. Nortmann, D. Cont, P. J. Amado, M. Azzaro, J. A. Caballero, S. Czesla, A. Hatzes, Th. Henning, M. López-Puertas, K. Molaverdikhani, D. Montes, J. Orell-Miquel, E. Pallé, A. Peláez-Torres, A. Quirrenbach, A. Reiners, I. Ribas, A. Sánchez-López, A. Schweitzer, F. Yan

Earth and Planetary Astrophysics

Mass determination of the three long-period Neptune- and sub-Neptune-sized planets transiting TOI-282

A. Barone, F. Rodler, D. Gandolfi et al. (+16 more)

TOI-282 is a bright (V=9.38) F8 main-sequence star known to host three transiting long-period ($P_b$=22.9 d, $P_c$=56.0 d, and $P_d$=84.3 d) small ($R_p\approx$ 2-4 $R_{\oplus}$) planets. The orbital period ratio of the two outermost planets, namely TOI-282 c and d, is close to the 3:2 commensurability, suggesting that the planets might be trapped in a mean motion resonance. We combined space-borne photometry from the TESS telescope with high-precision HARPS and ESPRESSO Doppler measurements to refine orbital parameters, measure the planetary masses, and investigate the architecture and evolution of the system. We performed a Markov chain Monte Carlo joint analysis of the transit light curves and radial velocity time series, and carried out a dynamical analysis to model transit timing variations and Doppler measurements along with N-body integration. In agreement with previous results, we found that TOI-282 b, c, and d have radii of $R_b=2.69 \pm 0.23 \ R_{\oplus}$, $R_c=4.13^{+0.16}_{-0.14} \ R_{\oplus}$, and $R_d=3.11 \pm 0.15 \ R_{\oplus}$, respectively. We measured planetary masses of $M_b=6.2\pm1.6 \ M_{\oplus}$, $M_c=9.2\pm2.0 \ M_{\oplus}$, and $M_d=5.8^{+0.9}_{-1.1} \ M_{\oplus}$, which imply mean densities of $\rho_b=1.8^{+0.7}_{-0.6} \ \text{g cm}^{-3}$, $\rho_c=0.7 \pm 0.2 \ \text{g cm}^{-3}$, and $\rho_d=1.1^{+0.3}_{-0.2} \ \text{g cm}^{-3}$, respectively. The three planets may be water worlds, making TOI-282 an interesting system for future atmospheric follow-up observations with JWST and ELT.
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All authors A. Barone, F. Rodler, D. Gandolfi, A. Bonfanti, P. Leonardi, L. Visca, M. Fridlund, M. Brogi, L. Fossati, P. E. Cubillos, W. D. Cochran, S. Csizmadia, J. Livingston, G. Nowak, E. Pallé, C. M. Persson, S. Redfield, H. Schmerling, A. M. S. Smith

High Energy Astrophysical Phenomena

Searching for Electromagnetic Counterpart Candidates to GW231123

Lei He, Liang-Gui Zhu, Zheng-Yan Liu et al. (+14 more)

The detection of GW231123, a gravitational-wave (GW) event with exceptionally massive and rapidly spinning black holes, suggests the possible formation within an active galactic nucleus (AGN) disk, which provides a favorable environment for potentially generating an observable electromagnetic (EM) counterpart. We conduct a search for such a counterpart by crossmatching the GW localization with a comprehensive catalog of AGN flares from the Zwicky Transient Facility. Our analysis yields six plausible optical flare candidates that are spatially and temporally coincident with GW231123 and exhibit significant deviations from their AGN baseline flux. Although these candidates represent a crucial first step, their true nature remains inconclusive. Confirming any one of these flares via future observations would provide a landmark validation of the AGN formation channel and unlock the multi-messenger potential of this extraordinary merger.
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All authors Lei He, Liang-Gui Zhu, Zheng-Yan Liu, Rui Niu, Chao Wei, Bing-Zhou Gao, Ming-Shen Zhou, Run-Duo Liang, Ken Chen, Jian-Min Wang, Ning Jiang, Zhen-Yi Cai, Ji-an Jiang, Zi-Gao Dai, Ye-Fei Yuan, Jian Li, Wen Zhao

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

The tidal response of a relativistic star

Nils Andersson, Rhys Counsell, Fabian Gittins et al. (+1 more)

We develop a fully relativistic approach for determining the response of a compact star to a time/frequency dependent (tidal) environment. The strategy involves matching the solution for the linearised fluid dynamics in the star's interior to the spacetime perturbations in the near-zone surrounding the body, along with an identification of the tidal driving and the star's response. Notably, this identification is exact in Newtonian gravity and we provide strong evidence that it remains robust also in the relativistic case. The argument does not involve a sum over the star's quasinormal modes and hence circumvents one of the obstacles that have held up the development of models for relativistic tides. Numerical results are provided, at the proof-of-principle level, for a realistic matter equation of state from the Brussels-Skyrme family, including composition stratification leading to the presence of low-frequency gravity modes. We also sketch the connection with the field-theory inspired approach to the problem, in which the tidal response is expressed in terms of asymptotic scattering amplitudes. We argue that progress in this direction is essential in order to complete the description of tides in relativistic stars.
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All authors Nils Andersson, Rhys Counsell, Fabian Gittins, Suprovo Ghosh

High Energy Astrophysical Phenomena

The most distant optically polarised GRB afterglow: GRB 240419A at z = 5.178

R. Brivio, S. Covino, M. Ferro et al. (+31 more)

Gamma-ray bursts (GRBs) are extremely bright phenomena powered by relativistic jets arising from explosive events at cosmological distances. The nature of the jet and the configuration of the local magnetic fields are still unclear, with the distinction between different models possibly provided by the detection of early-time polarisation. Past observations do not agree on a universal scenario describing early-time polarisation in GRB afterglows, and new studies are necessary to investigate this open question. We present here the discovery of GRB\,240419A, its redshift determination of $z=5.178$, its early-time optical polarimetry observations, and the multi-wavelength monitoring of its afterglow. We analysed three epochs of polarimetric data to derive the early-time evolution of the polarisation. The multi-wavelength light curve from the X-rays to the near-infrared band was also investigated to give a broader perspective on the whole event. We find a high level of polarisation, $P=6.97^{+1.84}_{-1.52}$\,%, at 1740~s after the GRB trigger, followed by a slight decrease up to $P=4.81^{+1.87}_{-1.53}$\,% at 3059~s. On the same timescale, the polarisation position angle is nearly constant. The multi-band afterglow at the time of the polarisation measurements is consistent with a forward shock (FS), while the earlier evolution at $t-t_0\lesssim700$ s can be associated with the interplay between the forward and the reverse shocks or with energy injection. The detected polarised radiation when the afterglow is FS-dominated and the stable position angle are consistent with an ordered magnetic field plus a turbulent component driven by large-scale magnetohydrodynamic instabilities. The lack of a jet break in the light curve prevents a comparison of the polarisation temporal evolution with theoretical expectations from magnetic fields amplified by microscopic-scale turbulence, limiting ...
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All authors R. Brivio, S. Covino, M. Ferro, A. Saccardi, A. Martin-Carrillo, A. Kuwata, K. Toma, P. D'Avanzo, Y.-D. Hu, L. Izzo, S. Kobayashi, T. Laskar, G. Leloudas, D. B. Malesani, M. Pursiainen, S. Vergani, K. Wiersema, S. Bloemen, S. Campana, V. D'Elia, S. de Wet, M. de Pasquale, P. J. Groot, P. Jakobsson, J. Mao, A. Melandri, G. Pugliese, A. Rossi, R. Salvaterra, B. Schneider, N. R. Tanvir, J. van Roestel, P. M. Vreeswijk, T. Zafar

Astrophysics of Galaxies

Stellar Population Astrophysics (SPA) with the TNG 23 IR elemental abundances of 114 giant stars in 41 Open Clusters

Shilpa Bijavara Seshashayana, Henrik Jönsson, Valentina D'Orazi et al. (+4 more)

Open clusters have been extensively used as tracers of Galactic chemical evolution, as their constituent stars possess shared characteristics, including age, Galactocentric radius, metallicity, and chemical composition. By examining the trends of elemental abundances with metallicity, age, and Galactocentric radius, valuable insights can be gained into the distribution and nucleosynthetic origins of chemical elements across the Galactic disc. The infrared domain in particular facilitates the observation of some elemental abundances that can be challenging or impossible to discern in the optical, for example K and F. The objective of this study is to derive the stellar parameters and elemental abundances of up to 23 elements in 114 stars spanning 41 open clusters using high-resolution infrared spectroscopy. In addition, the present study aims to examine the chemical evolution of the Galactic disc. This is achieved by investigating radial abundance gradients, variations in abundance between clusters, and the dependence of chemical abundances on cluster age.
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All authors Shilpa Bijavara Seshashayana, Henrik Jönsson, Valentina D'Orazi, Angela Bragaglia, Mingjie Jian, Gloria Andreuzzi, Marina Dal Ponte

Astrophysics of Galaxies

Spatially resolved PAH$_{3.3}$ emission and stellar ages in ram pressure stripped clumps at $z\sim0.3$

Pietro Benotto, Benedetta Vulcani, Peter J. Watson et al. (+8 more)

Ram pressure stripping (RPS) plays a crucial role in shaping galaxy evolution in dense environments, yet its impact on the molecular and dusty phases of the interstellar medium remains poorly understood. We present JWST/NIRCam $3.3\mathrm{\mu m}$ polycyclic aromatic hydrocarbon (PAH) emission maps for the nine most striking RPS galaxies in the Abell 2744 cluster at redshift $z_{cl}=0.306$, tracing the effects of environmental processes on small dust grains. Exploiting multi-band JWST/NIRCam and HST photometry, we performed a spatially resolved ultraviolet (UV) to mid-infrared (MIR) spectral energy distribution (SED) fitting to characterise stellar populations in both galactic disks and clumps detected in the stripped tails. We detected PAH$_{3.3}$ emission in eight of the nine galaxies at $5\sigma$, with morphologies revealing disk truncation and elongation along the RPS direction. In three galaxies, PAH$_{3.3}$ emission is also found in star-forming clumps embedded in the stripped tails up to a distance of $40\mathrm{kpc}$. Star formation rates inferred from PAH$_{3.3}$ emission are in agreement with those derived from SED fitting averaged over the past $100\mathrm{Myr}$ within an intrinsic scatter of $0.4\mathrm{dex}$, but the relation appears to be age-dependent. The spatial correlation between the PAH strength, stellar age, and star formation rate (SFR) is consistent across disks and tails and demonstrates that PAH-carrying molecules can survive and become stripped by ram pressure. Finally, age gradients revealed by the SED fitting provide observational evidence of the fireball model in star-forming, stripped clumps of galaxies at $z \sim 0.3$. This work represents the first detailed study of PAH emission in cluster galaxies, offering new insights into the fate of dust and star formation in extreme environments.
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All authors Pietro Benotto, Benedetta Vulcani, Peter J. Watson, Giulia Rodighiero, Bianca M. Poggianti, Marco Gullieuszik, Jacopo Fritz, Thomas S.-Y. Lai, Augusto E. Lassen, Matthew A. Malkan, Alessia Moretti

Cosmology and Nongalactic Astrophysics

Sym-EFT: Accelerating Effective Field Theory of Large Scale Structure with Symbolic Regression

Despoina Farakou and Constantinos Skordis

We present an emulator suite for the one- and two-loop cold dark matter power spectrum from the Effective Field Theory of Large Scale Structures (EFTofLSS). Specifically, we emulate separately the various contributions to the one- and two-loop parts of the power spectrum, leaving out the possible counterterms which can be added as multiplicative prefactors. By leaving the time-dependence of the counterterms unspecified at the emulation stage, our technique has the advantage of being extremely versatile in fitting any type of counterterm parametrisation to data, or to simulations, without having to change the emulator. We construct our emulators using the method of symbolic regression which results in functions that can be used directly in computer code, while achieving errors of better than $0.5\%$ within the $k$-range of validity of EFT and maintaining ultra-fast computational evaluation of less than $\sim5\times10^{-4}s$ on a single core.
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High Energy Astrophysical Phenomena

Formation of millisecond pulsar-helium star binaries

Zhu-Ling Deng, Xiang-Dong Li, Yong Shao et al. (+2 more)

PSR J1928+1815, the first recycled pulsar-helium (He) star binary discovered by the Five-hundred-meter Aperture Spherical radio Telescope, consists of a 10.55 ms pulsar and a companion star with mass $1-1.6\,M_{\sun}$ in a 0.15-day orbit. Theoretical studies suggest that this system originated from a neutron star (NS) intermediate-mass or high-mass X-ray binary that underwent common envelope (CE) evolution, leading to the successful ejection of the giant envelope. The traditional view is that hypercritical accretion during the CE phase may have recycled the NS. However, the specific mechanism responsible for accelerating its spin period remains uncertain due to the complex processes involved in CE evolution.In this study, we investigate the influence of Roche lobe overflow (RLO) accretion that takes place prior to the CE phase on the spin evolution of NSs. Our primary objective is to clarify how this process affects the spin characteristics of pulsars. We utilized the stellar evolution code MESA and the binary population synthesis code BSE to model the formation and evolution of NS-He star binaries. We calculated the distributions of the orbital period, He star mass, NS spin period, and magnetic field for NS + He star systems in the Galaxy. Our results indicate that RLO accretion preceding the CE phase could spin up NSs to millisecond periods through super-Eddington accretion. Considering a range of CE efficiencies $\alpha_{\rm CE}$ from 0.3 to 3, we estimate the birthrate (total number) of NS + He star systems in our Galaxy to be 5.2$\times 10^{-5}$ yr$^{-1}$ (626 systems) to 1.9$\times 10^{-4}$ yr$^{-1}$ (2684 systems).
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All authors Zhu-Ling Deng, Xiang-Dong Li, Yong Shao, Ying-Han Mao, Long Jiang

Astrophysics of Galaxies

NGC 6860, Mrk 915, and MCG -01-24-012. II. Inflowing and outflowing cold molecular gas and the connection with ionized gas in Seyfert galaxies

Bruno Dall'Agnol de Oliveira, Thaisa Storchi-Bergmann, Neil Nagar et al. (+5 more)

We present a study of the cold molecular gas kinematics in the inner ~ 4-7 kpc (projected sizes) of three nearby Seyfert galaxies, with AGN luminosities of ~ 10$^{44}$ erg/s, using observations of the CO(2-1) emission line, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) at ~ 0.5-0.8$^{\prime\prime}$ (~ 150-400 pc) spatial resolutions. After modeling the CO profiles with multiple Gaussian components, we detected regions with double-peak profiles that exhibit kinematics distinct from the dominant rotational motion. In NGC 6860, a molecular outflow surrounding the bipolar emission of the [O III] ionized gas is observed extending up to $R_{out}$ ~ 560 pc from the nucleus. There is evidence of molecular inflows along the stellar bar, although an alternative scenario, involving a decoupled rotation in a circumnuclear disk (CND) can also explain the observed kinematics. Mrk 915 shows double-peak CO profiles along one of its spiral arms. Due to its ambiguous disk orientation, part of the CO emission can be interpreted as a molecular gas inflow or an outflow reaching $R_{out}$ ~ 2.8 kpc. MCG -01-24-012 has double-peak profiles associated with a CND, perpendicular to the [O III] bipolar emission. The CO in the CND is rotating while outflowing within $R_{out}$ ~ 3 kpc, with the disturbances possibly being caused by the passage of the ionized gas outflow. Overall, the mass inflow rates are larger than the accretion rate needed to produce the observed luminosities, suggesting that only a fraction of the inflowing gas ends up feeding the central black holes. Although we found signatures of AGN feedback on the cold molecular phase, the mass outflow rates of ~ 0.09-3 M$_\odot$/yr indicate an overall weak impact at these AGN luminosities. Nonetheless, we may be witnessing the start of the depletion and ejection of the molecular gas reservoir that has accumulated over time.
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All authors Bruno Dall'Agnol de Oliveira, Thaisa Storchi-Bergmann, Neil Nagar, Santiago Garcia-Burillo, Rogemar A. Riffel, Dominika Wylezalek, Pranav Kukreti, Venkatessh Ramakrishnan

High Energy Astrophysical Phenomena

Probing Lorentz Invariance Violation at High Energies Using LHAASO Observations of GRB221009A via DisCan Algorithm

Yu-Chen Hua, Xiao-Jun Bi, Yu-Ming Yang et al. (+1 more)

The Lorentz invariance violation (LIV) predicted by some quantum gravity theories would manifest as an energy-dependent speed of light, which may potentially distort the observed temporal profile of photons from astrophysical sources at cosmological distances. The dispersion cancellation (DisCan) algorithm offers a powerful methodology for investigating such effects by employing quantities such as Shannon entropy, which reflects the initial temporal characteristics. In this study, we apply the DisCan algorithm to search for LIV effects in the LHAASO observations of GRB 221009A, combining data from both the WCDA and KM2A detectors that collectively span an energy range of $\sim 0.2-13$ TeV. Our analysis accounts for the uncertainties from both energy resolution and temporal binning. We derive $95\%$ confidence level lower limits on the LIV energy scale of $E_{\rm{QG}}/10^{19}~\text{GeV}>21.1$ (13.8) for the first-order subluminal (superluminal) scenario, and $E_{\rm{QG}}/10^{11}~\text{GeV}> 14.9$ (13.7) for the second-order subluminal (superluminal) scenario.
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All authors Yu-Chen Hua, Xiao-Jun Bi, Yu-Ming Yang, Peng-Fei Yin

Astrophysics of Galaxies

Quokka-based understanding of outflows (QED) – IV. Limitations of H$\alpha$ as an outflow diagnostic

Rongjun Huang, Aditi Vijayan and Mark R. Krumholz

The presence of broad wings in the H$\alpha$ line is commonly used as a diagnostic of the presence and properties of galactic winds from star-forming galaxies. However, the accuracy of this approach has not been subjected to extensive testing. In this paper, we use high-resolution simulations of galactic wind launching to calibrate the extent to which broad H$\alpha$ wings can be used to infer the properties of galactic outflows. For this purpose, we analyse a series of high-resolution wind simulations from the QED suite spanning two orders of magnitude in star formation surface density ($\Sigma_\mathrm{SFR}$). We show that the broad component of H$\alpha$ emission correlates well with the wind mass flux at heights $\sim1$ kpc above the galactic plane, but that the correlation is poor at larger distances from the plane, and that even at 1 kpc the relationship between mass flux and surface brightness of broad H$\alpha$ is significantly sub-linear. The sub-linear scaling suggests that the electron column density in the wind increases systematically with outflow strength, and that the conventional assumption of constant electron density in the wind leads to a systematic overestimate of how steeply mass loading factors depend on $\Sigma_\mathrm{SFR}$. We provide empirical scaling relations that observers can apply to correct for this effect when converting H$\alpha$ measurements to mass outflow rates. Finally, we use synthetic observations of the density-diagnostic $[\mathrm{S_{II}}]\,\lambda\lambda6716,6731$ doublet to show that using this diagnostic only slightly improves estimates of wind outflow rates compared to the naive assumption of constant electron density, and performs significantly worse than the empirical correlation we provide.
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Astrophysics of Galaxies

A deep X-ray look to the most obscured quasar at z~3.6 and its environment

I. Villani, L. Zappacosta, E. Piconcelli et al. (+17 more)

The most luminous and obscured quasars (QSOs) detected in infrared all-sky surveys could represent a key co-evolutionary phase from nuclear to circum-galactic (CG) scales in the formation of massive galaxies. In this context, Hot Dust Obscured Galaxies (Hot DOGs) at z ~2-4 provide a unique opportunity to study the link between cosmic mass assembly and nuclear accretion in high-z luminous QSOs/galaxies. W0410-0913 (hereafter W0410-09) is a luminous ($\rm ~L_{\rm bol} \sim 6.4 \times10^{47} \rm erg\ s^{-1}$) obscured QSO at z = 3.631, with a 30 kpc CG Ly$\alpha$ nebula (CGLAN), smaller than the ~ 100 kpc nebulae around unobscured Type-I QSOs, and an exceptional overdense environment of ~ 19 Ly$\alpha$ emitters (LAEs) within 300 kpc and $\pm$ 200 $\rm km ~s^{-1}$ of the Hot DOG. We aim to detect and characterize nuclear accretion in W0410-09 and its environment. Exploiting a deep proprietary ~280 ks Chandra observation, using empirical and physically motivated models for obscured sources, we show that W0410-09 exhibits Compton-thick obscuration ($\rm~ N_H > 10^{24} \rm cm^{-2}$) and high intrinsic luminosity ($\rm ~L_{2-10} > 10^{45} \rm erg ~s^{-1}$), making it one of the most luminous obscured QSOs at z $>$ 3.5. With the exclusion of W0410-09 we do not detect X-ray emission from any of the 19 LAEs, except for a 3$\sigma$ signal in the 6-7 keV rest-frame band, interpreted as Fe K$\alpha$ emission, suggesting the presence of heavily obscured yet undetected AGN emission in several LAEs. Including W0410-09, the estimated AGN fraction is $f_{\rm AGN}^{\rm LAE} = 5^{+12}_{-4}$%, potentially up to ~35% if unresolved obscured AGN are considered as suggested by the Fe K$\alpha$ line detection. We conclude that W0410-09 is in a critical transitional blow-out phase, during which powerful QSO-driven outflows are clearing the nuclear obscuration, ultimately leading to an unobscured luminous quasar.
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All authors I. Villani, L. Zappacosta, E. Piconcelli, M. Ginolfi, F. Ricci, F. La Franca, F. Arrigoni-Battaia, A. Bongiorno, S. Cantalupo, S. Carniani, F. Civano, A. Comastri, F. Fiore, R. Maiolino, L. Pentericci, C. Ricci, R. Schneider, R. Valiante, C. Vignali, F. Vito

Astrophysics of Galaxies

Discovery of an X-ray Luminous Radio-Loud Quasar at $z=3.4$: A Possible Transitional Super-Eddington Phase

Sakiko Obuchi, Kohei Ichikawa, Satoshi Yamada et al. (+11 more)

We report the multiwavelength properties of eFEDS J084222.9+001000 (hereafter ID830), a quasar at $z=3.4351$, identified as the most X-ray luminous radio-loud quasar in the eROSITA Final Equatorial Depth Survey (eFEDS) field. ID830 shows a rest-frame 0.5-2 keV luminosity of $\log (L_\mathrm{0.5-2\,keV}/\mathrm{erg}~\mathrm{s}^{-1}) = 46.20 \pm 0.12$, with a steep X-ray photon index ($\Gamma =2.43 \pm 0.21$), and a significant radio counterpart detected with VLA/FIRST 1.4 GHz and VLASS 3 GHz bands. The rest-frame UV to optical spectra from SDSS and Subaru/MOIRCS $J$-band show a dust reddened quasar feature with $A_\mathrm{V} = 0.39 \pm 0.08$ mag and the expected bolometric AGN luminosity from the dust-extinction-corrected UV luminosity reaches $L_\mathrm{bol,3000}= (7.62 \pm 0.31) \times 10^{46}$ erg s$^{-1}$. We estimate the black hole mass of $M_\mathrm{BH} = (4.40 \pm 0.72) \times 10^{8} M_{\odot}$ based on the MgII$\lambda$2800 emission line width, and an Eddington ratio from the dust-extinction-corrected UV continuum luminosity reaches $\lambda_\mathrm{Edd,UV}=1.44 \pm 0.24$ and $\lambda_{\mathrm{Edd,X}} = 12.8 \pm 3.9$ from the X-ray luminosity, both indicating the super-Eddington accretion. ID830 shows a high ratio of UV-to-X-ray luminosities, $\alpha_\mathrm{OX}=-1.20 \pm 0.07$ (or $\alpha_\mathrm{OX}=-1.42 \pm 0.07$ after correcting for jet-linked X-ray excess), higher than quasars and little red dots in super-Eddington phase with similar UV luminosities, with $\alpha_\mathrm{OX}<-1.8$. Such a high $\alpha_\mathrm{OX}$ suggests the coexistence of a prominent radio jet and X-ray corona, in this high Eddington accretion phase. We propose that ID830 may be in a transitional phase after an accretion burst, evolving from a super-Eddington to a sub-Eddington state, which could naturally describe the high $\alpha_\mathrm{OX}$.
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All authors Sakiko Obuchi, Kohei Ichikawa, Satoshi Yamada, Nozomu Kawakatu, Teng Liu, Naoki Matsumoto, Andrea Merloni, Kosuke Takahashi, Ingyin Zaw, Xiaoyang Chen, Kazuhiro Hada, Zsofi Igo, Hyewon Suh, Julien Wolf

High Energy Astrophysical Phenomena

Unveiling the Nature of Superorbital Modulation of SMC X-1 using NinjaSat

Chin-Ping Hu, Naoyuki Ota, Takuya Takahashi et al. (+13 more)

We report a long-term, high-cadence timing and spectral observation of the X-ray pulsar SMC X-1 using NinjaSat, a 6U CubeSat in low-Earth orbit, covering nearly a full superorbital cycle. SMC X-1 is a high-mass X-ray binary exhibiting a 0.7 s X-ray pulsar and a non-stationary superorbital modulation with periods ranging from approximately 40 to 65 days. Its peak luminosity of $1.3\times10^{39}$~\lumcgs\ makes it a local analogue of ultraluminous X-ray pulsars powered by supercritical accretion. We find that the spin-up rate during the high state remains consistent with the long-term average, with no significant correlation between spin-up rate and flux. This result indicates that the modulation is primarily geometric rather than accretion-driven. The hardness ratio and spectral shape are stable throughout the entire superorbital cycle, supporting obscuration by optically thick material or energy-independent scattering. In addition, the 2–20 keV pulse profile varies with superorbital phase, which may be explained either by variable covering fraction due to geometric obscuration, or by free precession of the neutron star. This represents the first complete measurement of spin-up rate and spectral evolution across a single superorbital cycle in SMC X-1, highlighting the scientific capability of CubeSat-based observatories.
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All authors Chin-Ping Hu, Naoyuki Ota, Takuya Takahashi, Tomoshi Takeda, Teruaki Enoto, Toru Tamagawa, Biswajit Paul, Sota Watanabe, Wataru Iwakiri, Tatehiro Mihara, Amira Aoyama, Satoko Iwata, Kaede Yamasaki, Takayuki Kita, Soma Tsuchiya, Mayu Ichibakase

High Energy Astrophysical Phenomena

LHAASO Detection of Ultra-High-Energy Gamma-Ray Emission toward the Giant Molecular Clouds

Zhen Cao, F. Aharonian, Y.X. Bai et al. (+313 more)

The $\gamma$-ray from Giant molecular clouds (GMCs) is regarded as the most ideal tool to perform in-situ measurement of cosmic ray (CR) density and spectra in our Galaxy. We report the first detection of $\gamma$-ray emissions in the very-high-energy (VHE) domain from the five nearby GMCs with a stacking analysis based on a 4.5-year $\gamma$-ray observation with the Large High Altitude Air Shower Observatory (LHAASO) experiment. The spectral energy distributions derived from the GMCs are consistent with the expected $\gamma$-ray flux produced via CR interacting with the ISM in the energy interval 1 - 100 $~\rm$ TeV. In addition, we investigate the presence of the CR spectral `knee' by introducing a spectral break in the $\gamma$-ray data. While no significant evidence for the CR knee is found, the current KM2A measurements from GMCs strongly favor a proton CR knee located above 0.9$~\rm$ PeV, which is consistent with the latest measurement of the CR spectrum by ground-based experiments.
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All authors Zhen Cao, F. Aharonian, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, W. Bian, A.V. Bukevich, C.M. Cai, W.Y. Cao, Zhe Cao, J. Chang, J.F. Chang, A.M. Chen, E.S. Chen, G.H. Chen, H.X. Chen, Liang Chen, Long Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, X.B. Chen, X.J. Chen, Y. Chen, N. Cheng, Y.D. Cheng, M.C. Chu, M.Y. Cui, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, Z.G. Dai, Danzengluobu, Y.X. Diao, X.Q. Dong, K.K. Duan, J.H. Fan, Y.Z. Fan, J. Fang, J.H. Fang, K. Fang, C.F. Feng, H. Feng, L. Feng, S.H. Feng, X.T. Feng, Y. Feng, Y.L. Feng, S. Gabici, B. Gao, C.D. Gao, Q. Gao, W. Gao, W.K. Gao, M.M. Ge, T.T. Ge, L.S. Geng, G. Giacinti, G.H. Gong, Q.B. Gou, M.H. Gu, F.L. Guo, J. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Guo, Y.A. Han, O.A. Hannuksela, M. Hasan, H.H. He, H.N. He, J.Y. He, X.Y. He, Y. He, S. Hernández-Cadena, B.W. Hou, C. Hou, X. Hou, H.B. Hu, S.C. Hu, C. Huang, D.H. Huang, J.J. Huang, T.Q. Huang, W.J. Huang, X.T. Huang, X.Y. Huang, Y. Huang, Y.Y. Huang, X.L. Ji, H.Y. Jia, K. Jia, H.B. Jiang, K. Jiang, X.W. Jiang, Z.J. Jiang, M. Jin, S. Kaci, M.M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, K. Kurinov, B.B. Li, Cheng Li, Cong Li, D. Li, F. Li, H.B. Li, H.C. Li, Jian Li, Jie Li, K. Li, L. Li, R.L. Li, S.D. Li, T.Y. Li, W.L. Li, X.R. Li, Xin Li, Y. Li, Y.Z. Li, Zhe Li, Zhuo Li, E.W. Liang, Y.F. Liang, S.J. Lin, B. Liu, C. Liu, D. Liu, D.B. Liu, H. Liu, H.D. Liu, J. Liu, J.L. Liu, J.R. Liu, M.Y. Liu, R.Y. Liu, S.M. Liu, W. Liu, X. Liu, Y. Liu, Y. Liu, Y.N. Liu, Y.Q. Lou, Q. Luo, Y. Luo, H.K. Lv, B.Q. Ma, L.L. Ma, X.H. Ma, J.R. Mao, Z. Min, W. Mitthumsiri, G.B. Mou, H.J. Mu, A. Neronov, K.C.Y. Ng, M.Y. Ni, L. Nie, L.J. Ou, P. Pattarakijwanich, Z.Y. Pei, J.C. Qi, M.Y. Qi, J.J. Qin, A. Raza, C.Y. Ren, D. Ruffolo, A. Sáiz, D. Semikoz, L. Shao, O. Shchegolev, Y.Z. Shen, X.D. Sheng, Z.D. Shi, F.W. Shu, H.C. Song, Yu.V. Stenkin, V. Stepanov, Y. Su, D.X. Sun, H. Sun, Q.N. Sun, X.N. Sun, Z.B. Sun, N.H. Tabasam, J. Takata, P.H.T. Tam, H.B. Tan, Q.W. Tang, R. Tang, Z.B. Tang, W.W. Tian, C.N. Tong, L.H. Wan, C. Wang, G.W. Wang, H.G. Wang, J.C. Wang, K. Wang, Kai Wang, Kai Wang, L.P. Wang, L.Y. Wang, L.Y. Wang, R. Wang, W. Wang, X.G. Wang, X.J. Wang, X.Y. Wang, Y. Wang, Y.D. Wang, Z.H. Wang, Z.X. Wang, Zheng Wang, D.M. Wei, J.J. Wei, Y.J. Wei, T. Wen, S.S. Weng, C.Y. Wu, H.R. Wu, Q.W. Wu, S. Wu, X.F. Wu, Y.S. Wu, S.Q. Xi, J. Xia, J.J. Xia, G.M. Xiang, D.X. Xiao, G. Xiao, Y.L. Xin, Y. Xing, D.R. Xiong, Z. Xiong, D.L. Xu, R.F. Xu, R.X. Xu, W.L. Xu, L. Xue, D.H. Yan, T. Yan, C.W. Yang, C.Y. Yang, F.F. Yang, L.L. Yang, M.J. Yang, R.Z. Yang, W.X. Yang, Z.H. Yang, Z.G. Yao, X.A. Ye, L.Q. Yin, N. Yin, X.H. You, Z.Y. You, Q. Yuan, H. Yue, H.D. Zeng, T.X. Zeng, W. Zeng, X.T. Zeng, M. Zha, B.B. Zhang, B.T. Zhang, C. Zhang, F. Zhang, H. Zhang, H.M. Zhang, H.Y. Zhang, J.L. Zhang, Li Zhang, P.F. Zhang, P.P. Zhang, R. Zhang, S.R. Zhang, S.S. Zhang, W.Y. Zhang, X. Zhang, X.P. Zhang, Yi Zhang, Yong Zhang, Z.P. Zhang, J. Zhao, L. Zhao, L.Z. Zhao, S.P. Zhao, X.H. Zhao, Z.H. Zhao, F. Zheng, W.J. Zhong, B. Zhou, H. Zhou, J.N. Zhou, M. Zhou, P. Zhou, R. Zhou, X.X. Zhou, X.X. Zhou, B.Y. Zhu, C.G. Zhu, F.R. Zhu, H. Zhu, K.J. Zhu, Y.C. Zou, X. Zuo Y.H. Yu

High Energy Astrophysical Phenomena

Precise Measurement of the Cosmic Ray Helium Spectrum above 0.1 PeV

LHAASO Collaboration: Zhen Cao, F. Aharonian, Y.X. Bai et al. (+324 more)

We report a measurement of the cosmic ray helium energy spectrum in the energy interval 0.16 – 13~PeV, derived by subtracting the proton spectrum from the light component~(proton and helium) spectrum obtained with observations made by the Large High Altitude Air Shower Observatory~(LHAASO) under a consistent energy scale. The helium spectrum shows a significant hardening centered at $E \simeq$ 1.1~PeV, followed by a softening at $\sim$ 7 PeV, indicating the appearance of a helium `knee'. Comparing the proton and helium spectra in the LHAASO energy range reveals some remarkable facts. In the lower part of this range, in contrast to the behavior at lower energies, the helium spectrum is significantly softer than the proton spectrum. This results in protons overtaking helium nuclei and becoming the largest cosmic ray component at $E \simeq$ 0.7 PeV. A second crossing of the two spectra is observed at $E \simeq$ 5 PeV, above the proton knee, when helium nuclei overtake protons to become the largest cosmic ray component again. These results have important implications for our understanding of the Galactic cosmic ray sources.
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All authors LHAASO Collaboration: Zhen Cao, F. Aharonian, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, W. Bian, J. Blunier, A.V. Bukevich, C.M. Cai, Y.Y. Cai, W.Y. Cao, Zhe Cao, J. Chang, J.F. Chang, E.S. Chen, G.H. Chen, H.K. Chen, L.F. Chen, Liang Chen, Long Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, X.B. Chen, X.J. Chen, X.P. Chen, Y. Chen, N. Cheng, Q.Y. Cheng, Y.D. Cheng, M.Y. Cui, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, Z.G. Dai, Danzengluobu, Y.X. Diao, A.J. Dong, X.Q. Dong, K.K. Duan, J.H. Fan, Y.Z. Fan, J. Fang, J.H. Fang, K. Fang, C.F. Feng, H. Feng, L. Feng, S.H. Feng, X.T. Feng, Y. Feng, Y.L. Feng, S. Gabici, B. Gao, Q. Gao, W. Gao, W.K. Gao, M.M. Ge, T.T. Ge, L.S. Geng, G. Giacinti, G.H. Gong, Q.B. Gou, M.H. Gu, F.L. Guo, J. Guo, K.J. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Guo, R.P. Han, O.A. Hannuksela, M. Hasan, H.H. He, H.N. He, J.Y. He, X.Y. He, Y. He, S. Hernández-Cadena, B.W. Hou, C. Hou, X. Hou, H.B. Hu, S.C. Hu, C. Huang, D.H. Huang, J.J. Huang, X.L. Huang, X.T. Huang, X.Y. Huang, Y. Huang, Y.Y. Huang, A. Inventar, X.L. Ji, H.Y. Jia, K. Jia, H.B. Jiang, K. Jiang, X.W. Jiang, Z.J. Jiang, M. Jin, S. Kaci, M.M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, K. Kurinov, Cheng Li, Cong Li, D. Li, F. Li, H.B. Li, H.C. Li, Jian Li, Jie Li, K. Li, L. Li, R.L. Li, S.D. Li, T.Y. Li, W.L. Li, X.R. Li, Y. Li, Zhe Li, Zhuo Li, E.W. Liang, Y.F. Liang, S.J. Lin, P. Lipari, B. Liu, C. Liu, D. Liu, D.B. Liu, H. Liu, J. Liu, J.L. Liu, J.R. Liu, M.Y. Liu, R.Y. Liu, S.M. Liu, W. Liu, X. Liu, Y. Liu, Y. Liu, Y.N. Liu, Y.Q. Lou, Q. Luo, Y. Luo, H.K. Lv, B.Q. Ma, L.L. Ma, X.H. Ma, I.O. Maliy, J.R. Mao, Z. Min, W. Mitthumsiri, Y. Mizuno, G.B. Mou, A. Neronov, K.C.Y. Ng, M.Y. Ni, L. Nie, L.J. Ou, Z.W. Ou, P. Pattarakijwanich, Z.Y. Pei, D.Y. Peng, J.C. Qi, M.Y. Qi, J.J. Qin, D. Qu, A. Raza, C.Y. Ren, D. Ruffolo, A. Sáiz, D. Savchenko, D. Semikoz, L. Shao, O. Shchegolev, Y.Z. Shen, X.D. Sheng, Z.D. Shi, F.W. Shu, H.C. Song, Y. Su, D.X. Sun, H. Sun, J.X. Sun, Q.N. Sun, X.N. Sun, Z.B. Sun, N.H. Tabasam, J. Takata, P.H.T. Tam, H.B. Tan, Q.W. Tang, R. Tang, Z.B. Tang, W.W. Tian, C.N. Tong, L.H. Wan, C. Wang, D.H. Wang, G.W. Wang, H.G. Wang, J.C. Wang, K. Wang, Kai Wang, Kai Wang, L.P. Wang, L.Y. Wang, L.Y. Wang, R. Wang, W. Wang, X.G. Wang, X.J. Wang, X.Y. Wang, Y. Wang, Y.D. Wang, Z.H. Wang, Z.X. Wang, Zheng Wang, D.M. Wei, J.J. Wei, Y.J. Wei, T. Wen, S.S. Weng, C.Y. Wu, H.R. Wu, Q.W. Wu, S. Wu, X.F. Wu, Y.S. Wu, S.Q. Xi, J. Xia, J.J. Xia, G.M. Xiang, D.X. Xiao, G. Xiao, Y.F. Xiao, Y.L. Xin, H.D. Xing, Y. Xing, D.R. Xiong, B.N. Xu, C.Y. Xu, D.L. Xu, R.F. Xu, R.X. Xu, S.S. Xu, W.L. Xu, L. Xue, D.H. Yan, T. Yan, C.W. Yang, C.Y. Yang, F.F. Yang, L.L. Yang, M.J. Yang, R.Z. Yang, W.X. Yang, Z.H. Yang, Z.G. Yao, X.A. Ye, L.Q. Yin, N. Yin, X.H. You, Z.Y. You, Q. Yuan, H. Yue, H.D. Zeng, T.X. Zeng, W. Zeng, X.T. Zeng, M. Zha, B.B. Zhang, B.T. Zhang, C. Zhang, H. Zhang, H.M. Zhang, H.Y. Zhang, J.L. Zhang, J.Y. Zhang, Li Zhang, P.F. Zhang, R. Zhang, S.R. Zhang, S.S. Zhang, S.Y. Zhang, W. Zhang, W.Y. Zhang, X. Zhang, X.P. Zhang, Yi Zhang, Yong Zhang, Z.P. Zhang, J. Zhao, L. Zhao, L.Z. Zhao, S.P. Zhao, X.H. Zhao, Z.H. Zhao, F. Zheng, T.C. Zheng, B. Zhou, H. Zhou, J.N. Zhou, M. Zhou, P. Zhou, R. Zhou, X.X. Zhou, X.X. Zhou, B.Y. Zhu, C.G. Zhu, F.R. Zhu, H. Zhu, K.J. Zhu, Y.C. Zou, X. Zuo

High Energy Astrophysical Phenomena

Detecting FRB by DANCE: a method based on DEnsity ANalysis and Cluster Extraction

Mao Yuan, Jiarui Niu, Yi Feng et al. (+7 more)

Fast radio bursts (FRBs) are transient signals exhibiting diverse strengths and emission bandwidths. Traditional single-pulse search techniques are widely employed for FRB detection; yet weak, narrow-band bursts often remain undetectable due to low signal-to-noise ratios (SNR) in integrated profiles. We developed DANCE, a detection tool based on cluster analysis of the original spectrum. It is specifically designed to detect and isolate weak, narrow-band FRBs, providing direct visual identification of their emission properties. This method performs density clustering on reconstructed, RFI-cleaned observational data, enabling the extraction of targeted clusters in time-frequency domain that correspond to the genuine FRB emission range. Our simulations show that DANCE successfully extracts all true signals with SNR~>5 and achieves a detection precision exceeding 93%. Furthermore, through the practical detection of FRB 20201124A, DANCE has demonstrated a significant advantage in finding previously undetectable weak bursts, particularly those with distinct narrow-band features or occurring in proximity to stronger bursts.
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All authors Mao Yuan, Jiarui Niu, Yi Feng, Xu-ning Lv, Chenchen Miao, Lingqi Meng, Bo Peng, Li Deng, Jingye Yan, Weiwei Zhu

Solar and Stellar Astrophysics

Investigation on the Predictive Potentiality of Photospheric Magnetic Parameters for Distinguishing Confined from Eruptive Solar Flares

Jinhui Pan and Rui Liu

A question often arises as to why some solar flares are confined in the lower corona while others, termed eruptive flares, are associated with coronal mass ejections (CMEs). Here we intend to rank the importance of pre-flare magnetic parameters of active regions in their potentiality to predict whether an imminent flare will be eruptive or confined. We compiled a dataset comprising 277 solar flares of GOES-class M1.0 and above, taking place within 45 deg from the disk center between 2010 and 2023, involving 94 active regions. Among the 277 flares, 135 are confined and 142 are eruptive. Our statistical analysis reveals that the magnetic parameters that are most relevant to the flare category are: total unsigned magnetic flux $\Phi$, mean magnetic shear angle $\Theta$ along the polarity inversion line (PIL), photospheric free magnetic energy $E_f$, and centroid distance $d$ between opposite polarities. These four parameters are not independent of each other, but in combination, might be promising in distinguishing confined from eruptive flares. For a subset of 77 flares with high-gradient PILs, the area of high free energy regions ($A_{\mathrm{Hi}}$) becomes the most effective parameter related to the flare type, with confined flares possessing larger $A_{\mathrm{Hi}}$ than eruptive ones. Our results corroborate the general concept that the eruptive behavior of solar flares is regulated by an interplay between the constraining overlying flux, which is often dominant in both $\Phi$ and $E_f$ and related to $d$, and the current-carrying core flux, which is related to $\Theta$.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Low-reheating scenario in dark Higgs inflation and its impact on dark photon dark matter production

Sarif Khan, Jinsu Kim and Pyungwon Ko

We investigate dark matter (DM) phenomenology and cosmic inflation within a unified framework based on a dark $U(1)_D$ gauge extension of the Standard Model (SM). The associated dark gauge boson, namely the dark photon, serves as a viable DM candidate, which we call dark photon dark matter (DPDM), whilst the dark Higgs field drives inflation. We explore a low-reheating scenario where DM production occurs during reheating, resulting in significant entropy dilution of the DPDM abundance. Both weakly interacting massive particle (WIMP) and feebly interacting massive particle (FIMP) DM scenarios are explored, depending on the dark gauge coupling strength. For FIMP-type DM, the entropy dilution allows for stronger couplings whilst maintaining the correct relic abundance, potentially bringing these candidates within the reach of current and near-future detection experiments. Similarly, WIMP-type DM can be realised with weaker couplings. We perform a comprehensive parameter scan incorporating constraints from collider data, DM direct and indirect detection experiments, and cosmological observations. Taking quantum corrections and running of the couplings into account, we demonstrate that dark Higgs inflation yields predictions for the spectral index $n_s$ and the tensor-to-scalar ratio $r$ that are consistent with the Planck, BICEP/Keck, and ACT data. The nonminimal coupling of the dark Higgs inflaton field to gravity is shown to be much smaller than in the case of the SM Higgs inflation scenario, avoiding unitarity concerns. We show that reheating temperatures as low as 1 GeV and 1 MeV can be achieved through the decay and scattering processes of the inflaton, respectively, with the latter allowing for larger Higgs mixing angles and enhanced detection prospects. Our results establish that this minimal extension successfully unifies DM physics with inflationary cosmology.
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High Energy Astrophysical Phenomena

Recoil-Enabled Energy Transfer from Coherent Neutrino Scattering in Core-Collapse Supernovae

Tatsushi Shima

We revisit neutrino-matter coupling in the post-shock region of core-collapse supernovae by restoring nuclear recoil in coherent neutrino-nucleus scattering (CEvNS). The resulting local energy transfer (a few keV per ~10 MeV neutrino) accumulates across the ~100 km stalled-shock layer, yielding a total heating of 10^49-10^50 erg, comparable within an order of magnitude to the increment required to trigger shock revival in current multidimensional simulations. This indicates that the long-standing failure of isoenergetic transport schemes to revive the shock originates from their neglect of recoil kinematics. Because the momentum exchange in each scattering is tiny, the emergent neutrino spectra and lepton-number balance remain essentially unchanged. The result highlights nuclear recoil as a minimal yet physically grounded correction to standard neutrino transport, providing a self-consistent route toward reliable explosion modeling.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Novel Solar System Probes for Primordial Black Holes

Oem Trivedi and Abraham Loeb

Primordial Black Holes (PBHs) represent one of the more interesting ways to address dark matter, at the interface of both cosmology and quantum gravity. It is no surprise then that testing PBHs is a venue of active interest, with several cosmological and astrophysical probes constraining different mass ranges. In this work, we propose novel Solar System scale searches for PBHs, motivated by the unique precision and coverage of local observables. We show that asteroid to dwarf planet mass PBHs can induce measurable dipolar timing signatures in pulsar timing arrays, while planetary mass PBHs can generate detectable ADAF accretion flares through interactions with Kuiper Belt bodies. Together, these complementary approaches open a new observational frontier for probing PBHs across mass ranges that remain unconstrained by conventional cosmological methods.
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Thursday 6 November

Solar and Stellar Astrophysics

Multiplicity of stellar systems in the solar neighbourhood, wide binaries, and planet-hosting stars

Javier González-Payo

This doctoral thesis studies stellar multiplicity in the solar neighborhood (d < 10 pc) and in systems hosting planets (d < 100 pc). Using data from the Washington Double Star Catalogue, Gaia DR3, and a comprehensive literature review, it builds the most complete and homogeneous sample of multiple systems within 10 pc. Multiplicity and companion fractions are derived with reduced uncertainties, providing improved statistical reliability. The analysis of orbital periods from one day to millions of years shows that the log-normal cumulative distribution can be seen as a modern revision of Öpik's law. A key contribution is the study of wide binaries ({\rho} > 1000 arcsec) with Gaia DR3, expanding the known sample by over an order of magnitude and improving astrometric precision. Newly identified companions, including ultracool dwarfs at the M-L boundary and a hot white dwarf, refine the distinction between true binaries and unrelated young moving-group members. The thesis also explores the effect of multiplicity on exoplanetary systems within 100 pc. New stellar companions are found in known planetary systems, with separations for over 200 pairs and parameters compiled for 276 exoplanets. Compared to single-star systems, multiple systems host more massive, short-period, and high-eccentricity planets. About 22% of exoplanetary systems have stellar companions, with significant (> 4 {\sigma}) correlations between high eccentricities and small projected separations, and a weaker (> 2 {\sigma}) trend showing that massive planets (M > 40 M_Earth) orbit closer in multiple systems. Finally, a review of Giovanni Battista Hodierna's 17th-century catalogues shows he compiled the first list of multiple systems over a century earlier than previously believed, advancing the understanding of stellar multiplicity and its influence on planetary formation.
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Solar and Stellar Astrophysics

Calcium Excess in Novae: Beyond Nuclear Physics Uncertainties

Mallory Loria, Pavel Denissenkov, Chris Ruiz et al. (+1 more)

We examine Ca abundances in classical novae from spectroscopic observations spanning 65 years and investigate whether they are systematically high compared to those predicted by nova models. For the first time, we perform Monte Carlo simulations assessing the impact of nuclear reaction rate uncertainties on abundances predicted by multi-zone nova models. While the Ca abundances in the models are sensitive to variations of rates of the reactions 37Ar(p,gamma)38K and 38K(p,gamma)39Ca, the nuclear physics uncertainties of these reactions cannot account for the discrepancy between the observed and predicted Ca abundances in novae. Furthermore, the overabundance of Ca has important implications for measuring 7Be in nova ejecta, as Ca lines are used to estimate 7Be abundances. If the Ca abundance is incorrectly determined, it could lead to inaccurate 7Be abundance estimates. Possible alternative explanations for the observed Ca overabundance are discussed.
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All authors Mallory Loria, Pavel Denissenkov, Chris Ruiz, Falk Herwig

Solar and Stellar Astrophysics

SCATTER Common Envelope Formalism for Triples

Rosanne Di Stefano, Amaan Khwaja and Chiaki Kobayashi

Many stars are components of triple-star systems, or of higher-order multiples. In such systems mass transfer is common, and when the transfer is dynamically unstable, a common envelope forms. As such, it is important to be able to compute the post-common-envelope orbital separations among the various stars comprising the system, and to determine whether the common envelope induces mergers or makes later mergers inevitable. In this paper we compute the results of common-envelope evolution for triples. We employ the SCATTER formalism, a new approach to the computation of post-common-envelope separations. This work has applications to gravitational-wave mergers, Type Ia supernovae, and a broad range of other highly energetic phenomena.
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