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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 29 December

Instrumentation and Methods for Astrophysics

Lossless compression of simulated radio interferometric visibilities

A. R. Offringa and R. J. van Weeren

Context. Processing radio interferometric data often requires storing forward-predicted model data. In direction-dependent calibration, these data may have a volume an order of magnitude larger than the original data. Existing lossy compression techniques work well for observed, noisy data, but cause issues in calibration when applied to forward-predicted model data. Aims. To reduce the volume of forward-predicted model data, we present a lossless compression method called Simulated Signal Compression (Sisco) for noiseless data that integrates seamlessly with existing workflows. We show that Sisco can be combined with baseline-dependent averaging for further size reduction. Methods. Sisco decomposes complex floating-point visibility values and uses polynomial extrapolation in time and frequency to predict values, groups bytes for efficient encoding, and compresses residuals using the Deflate algorithm. We evaluate Sisco on diverse LOFAR, MeerKAT, and MWA datasets with various extrapolation functions. Implemented as an open-source Casacore storage manager, it can directly be used by any observatory that makes use of this format. Results. We find that a combination of linear and quadratic prediction yields optimal compression, reducing noiseless forward-predicted model data to 24% of its original volume on average. Compression varies by dataset, ranging from 13% for smooth data to 38% for less predictable data. For pure noise data, compression achieves just a size of 84% due to the unpredictability of such data. With the current implementation, the achieved compression throughput is with 534 MB/s mostly dominated by I/O on our testing platform, but occupies the processor during compression or decompression. Finally, we discuss the extension to a lossy algorithm.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Compact star and compact star matter properties from a baryonic extended linear sigma model with explicit chiral symmetry breaking

Yao Ma, Yong-Liang Ma and Lu-Qi Zhang

Based on a baryonic extended linear sigma model including explicit chiral symmetry breaking effect, the structure of neutron stars with the emergence of hyperons is investigated using the relativistic mean field approximation. It is found that, except for the lightest scalar meson $\sigma$ whose structure is not well understood so far, the vacuum mass spectra of relevant hadrons and nuclear matter properties around saturation density can be well reproduced. Nevertheless, based on the present model and the applied relativistic mean field approach, we found that, to have a realistic mass-radius relation of neutron stars, the $\pi N$ sigma term $\sigma_{\pi N}$ that denotes the contribution of explicit symmetry breaking should deviate from its empirical values at vacuum. Specifically, $\sigma_{\pi N}\sim -600$ MeV, rather than $(32\text{--}89) \rm \ MeV$ at vacuum. With an appropriate choice of $\sigma_{\pi N}$ and $K(n_0)$, our framework can give a more observationally favored mass-radius relation of neutron stars with the emergence of hyperons, suggesting a possible density dependence of the low energy constants, at least within the present leading order framework with the relativistic mean field approach. The present result provides a new perspective on the relation between microscopic explicit chiral symmetry breaking in dense matter and macroscopic structure of compact stars and calls for more systematic treatments beyond leading order relativistic mean field calculation.
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High Energy Astrophysical Phenomena

Observations of the Fermi bubbles and the Galactic center excess with the DArk Matter Particle Explorer

F. Alemanno, Q. An, P. Azzarello et al. (+145 more)

The DArk Matter Particle Explorer (DAMPE) is a space-borne high-energy particle detector that surveys the $\gamma$-ray sky above$\sim 2~\rm GeV$ with a peak acceptance of $\sim 0.2~\rm m^2\,sr$. With the 102 months of data collected by DAMPE, we show that the Fermi bubbles are detected at a significance of $\sim 26\sigma$ and identify a GeV excess in the direction of Galactic center at $\sim 7 \sigma$ confidence. Both spectra and morphology are consistent with those observed by Fermi-LAT and the GeV excess component can be interpreted by the dark matter annihilation with a mass of $\sim 50$ GeV and a velocity-averaged cross section of $\sim 10^{-26}~{\rm cm^{3}~s^{-1}}$ for the $\chi \chi \rightarrow b\bar{b}$ channel. Our results thus provide the first independent detection of these two intriguing diffuse gamma-ray sources besides Fermi-LAT.
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All authors F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong, G. Donvito, J. L. Duan, K. K. Duan, R. R. Fan, Y. Z. Fan, F. Fang, K. Fang, C. Q. Feng, L. Feng, S. Fogliacco, J. M. Frieden, P. Fusco, M. Gao, F. Gargano, E. Ghose, K. Gong, Y. Z. Gong, D. Y. Guo, J. H. Guo, S. X. Han, Y. M. Hu, G. S. Huang, X. Y. Huang, Y. Y. Huang, M. Ionica, L. Y. Jiang, W. Jiang, Y. Z. Jiang, J. Kong, A. Kotenko, D. Kyratzis, S. J. Lei, B. Li, M. B. Li, W. H. Li, W. L. Li, X. Li, X. Q. Li, Y. M. Liang, C. M. Liu, H. Liu, J. Liu, S. B. Liu, Y. Liu, F. Loparco, M. Ma, P. X. Ma, T. Ma, X. Y. Ma, G. Marsella, M. N. Mazziotta, D. Mo, Y. Nie, X. Y. Niu, A. Parenti, W. X. Peng, X. Y. Peng, C. Perrina, E. Putti-Garcia, R. Qiao, J. N. Rao, Y. Rong, R. Sarkar, P. Savina, A. Serpolla, Z. Shangguan, W. H. Shen, Z. Q. Shen, Z. T. Shen, L. Silveri, J. X. Song, H. Su, M. Su, H. R. Sun, Z. Y. Sun, A. Surdo, X. J. Teng, A. Tykhonov, G. F. Wang, J. Z. Wang, L. G. Wang, S. Wang, X. L. Wang, Y. F. Wang, D. M. Wei, J. J. Wei, Y. F. Wei, D. Wu, J. Wu, S. S. Wu, X. Wu, Z. Q. Xia, Z. Xiong, E. H. Xu, H. T. Xu, J. Xu, Z. H. Xu, Z. L. Xu, Z. Z. Xu, G. F. Xue, M. Y. Yan, H. B. Yang, P. Yang, Y. Q. Yang, H. J. Yao, Y. H. Yu, Q. Yuan, C. Yue, J. J. Zang, S. X. Zhang, W. Z. Zhang, Yan Zhang, Yi Zhang, Y. J. Zhang, Y. L. Zhang, Y. P. Zhang, Y. Q. Zhang, Z. Zhang, Z. Y. Zhang, C. Zhao, H. Y. Zhao, X. F. Zhao, C. Y. Zhou, X. Zhu, Y. Zhu

High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Neutron Star Equation of State with Nucleon Short-Range Correlations: A Concise Review and Open Issues

Bao-Jun Cai, Bao-An Li and Yu-Gang Ma

Nucleon short-range correlations (SRCs) and the associated high-momentum tail (HMT) in its momentum distribution $n(k)$ represent a universal feature of strongly interacting Fermi systems. In nuclear matter, SRCs arise primarily from the spin-isospin dependence of the tensor and short-range components of the nucleon-nucleon interaction, leading to a substantial depletion of its Fermi sea and a characteristic $k^{-4}$ tail populated predominantly by isosinglet neutron-proton pairs. These microscopic structures modify both the kinetic and interaction contributions to the Equation of State (EOS) of dense matter and thereby influence a broad range of neutron-star (NS) properties. This short review provides a streamlined overview of how SRC-induced changes in $n(k)$ reshape the kinetic EOS, including its symmetry energy part and how these effects propagate into macroscopic NS observables, including mass-radius relations, tidal deformabilities, direct Urca thresholds and core-crust transition. We summarize key existing results, highlight current observational constraints relevant for testing SRC-HMT effects, and outline open questions for future theoretical, experimental, and multimessenger studies of dense nucleonic matter.
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Astrophysics of Galaxies

Detections of Compact Radio Continuum toward Methanol Maser Rings Using the VLA

Anna Bartkiewicz, Olga Bayandina, Alberto Sanna et al. (+5 more)

High-mass protostars are deeply embedded in dust inside their natal cores and are not easily detectable. However, maser emission at centimeter wavelengths, owing to its high brightness, enables us to study gas kinematics in protostars' circumstellar regions. We aim to understand the origin of the ring-like structures outlined by the 6.7 GHz methanol maser emission in six high-mass young stellar objects by performing a sensitive search of the associated radio-continuum emission and derive its properties. We used the Karl G. Jansky Very Large Array in the A configuration at C and K bands in order to image radio-continuum as well as 6.7 GHz methanol and 22 GHz water maser emission. We present the first images of the thermal jets towards four targets in our sample, G23.389+00.185, G23.657-00.127, G28.817+00.365, and G30.400-00.296. In a further target, G23.207-00.377, the complex K band continuum emission makes it unclear whether the detected peaks trace jet knots from a single young protostar or mark multiple compact young protostars. The remaining source G31.047+00.356 shows radio continuum emission associated with an evolved H II region.
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All authors Anna Bartkiewicz, Olga Bayandina, Alberto Sanna, Marian Szymczak, Luca Moscadelli, Agnieszka Kobak, Huib Jan van Langevelde, Ashwin Varma

Solar and Stellar Astrophysics

On Systematic Errors in Cross-Identification of Binary Stars in Gaia

E. Malik, P. Kaigorodov, D. Kovaleva et al. (+1 more)

Using Gaia DR3 data, binary star catalogs have been created containing information on a total of more than 2.6 million pairs. This increases by more than an order of magnitude the ensemble of binary stars with known characteristics, which previously numbered about 140 thousand pairs. To perform statistical analysis of the complete ensemble of binary stars, including both previously known and newly discovered pairs, cross-identification by coordinates was carried out between the most complete pre-Gaia publication compilative binary star catalog ILB and data from binary star catalogs based on Gaia DR3 results. An analysis of the results of this identification was performed, showing the dependence of its characteristics both on the data from the source catalogs and on coordinates. It is shown that in dense stellar fields, particularly in the Galactic disk, an increase in the fraction of false positive identifications can be expected. At the same time, for systems with large proper motion, there is a high probability of a false negative outcome. Possible modifications to the identification method are proposed to reduce the role of the described systematic errors and increase the reliability of its results.
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All authors E. Malik, P. Kaigorodov, D. Kovaleva, O. Malkov

High Energy Astrophysical Phenomena

Unveiling SN 2022eyw: A Bright Member of the Type Iax Supernova Subclass

Hrishav Das, Devendra K. Sahu, Anirban Dutta et al. (+3 more)

We present comprehensive photometric and spectroscopic observations of Supernova (SN) 2022eyw, a luminous member of the Type Iax SN subclass. SN 2022eyw reached a peak absolute magnitude of $M_g = -17.80\pm0.15$ mag and exhibited a rise time of $\sim$15 days, placing it among the brighter Iax events. The bolometric light curve indicates a synthesized $^{56}$Ni mass of $0.11\pm0.01~\text{M}_{\odot}$, with an estimated ejecta mass of $0.79\pm0.09~\text{M}_{\odot}$ and kinetic energy of $0.19\times10^{51}$ erg. The spectral evolution from -8 to +110 days past maximum reveals features characteristic of bright Type Iax Supernovae, including a transition from Fe III to Fe II dominance, moderate expansion velocities, and a lack of strong C III absorption. TARDIS spectral modelling of the early-phase spectra indicates a well-mixed ejecta dominated by Fe-group elements. In addition, traces of unburnt carbon are detected, pointing to incomplete burning as expected in pure deflagration models. Late-time spectral evolution shows a blend of permitted and forbidden lines. Comparison with deflagration models suggests that SN 2022eyw originated from a partial deflagration of a Chandrasekhar-mass white dwarf, with explosion properties intermediate between the N3-def and N5-def models. These observations support pure deflagration of a CO white dwarf as a viable explosion mechanism for its luminous members.
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All authors Hrishav Das, Devendra K. Sahu, Anirban Dutta, Mridweeka Singh, G.C. Anupama, Rishabh Singh Teja

Cosmology and Nongalactic Astrophysics

Three channel dissipative warm Higgs inflation with global inference via genetic algorithms

Wei Cheng

This paper constructs and analyzes a three channel dissipative framework for Warm Higgs Inflation, wherein the total dissipation coefficient, $\Upsilon(h,T)$, is decomposed into low temperature, high temperature, and threshold activated contributions. A genetic algorithm is employed for the global numerical solution and statistical inference of the background field dynamics. To overcome the single channel dominance degeneracy in high dimensional parameter scans, two classes of structural priors are introduced into the objective function: a mixing prior to suppress extreme channel fractions and an entropy prior to favor multi channel coexistence. Furthermore, the adoption of a layered warmness criterion (e.g., $Q \equiv \Upsilon/3H$) decouples model selection from cosmological observables, thereby enhancing analytical transparency. The complete workflow is demonstrated on a $14$ dimensional phenomenological model. An ablation study of the priors (noprior vs. mixing vs. mixing+entropy) yields $18871$ viable parameter points, revealing that the priors significantly enhance the discovery probability of non-trivial multi channel solutions within a parameter space naturally biased towards single channel dominance. After imposing the observational constraint $r < 0.036$, the number of retained solutions for each scenario is $14485$, $1889$, and $1971$, respectively. A typical best fit solution exhibits a "channel relay" dynamical feature during its evolution and a genuinely mixed state at the pivot scale (e.g., $f_{{\rm HT},*}\simeq 0.399480$, $f_{{\rm th},*}\simeq 0.600517$), implying that the microscopic origin of dissipation need not be unique within a single inflationary history.
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High Energy Astrophysical Phenomena

Possibility of Month-scale Quasi-periodic Oscillations in the Gamma-ray Light Curve of OP 313

Sandeep Kumar Mondal, Shubham Kishore, Alok C. Gupta et al. (+1 more)

In this work, we report evidence suggesting the potential future detection of a month-scale quasi-periodic oscillation (QPO) in the gamma-ray light curve of OP 313. We analysed almost 16.8 years of Fermi-LAT gamma-ray data and applied the Bayesian block method to the monthly-binned light curve. We identified four high-flux states and investigated the possibility of a QPO in the fourth high-flux state (MJD 59482-60832). Using the Weighted Wavelet Z-transform (WWZ) and Lomb-Scargle Periodogram (LSP) methods, we find tentative evidence for a month-scale QPO; however, its detection significance is limited by the small number of observed cycles. With a sufficiently long data set, the QPO may be detected with higher significance in the future. We further explored possible physical origins of this potential QPO and examined several models. We found that a curved-jet model can explain the observed behaviour.
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All authors Sandeep Kumar Mondal, Shubham Kishore, Alok C. Gupta, Gwenael Giacinti

High Energy Astrophysical Phenomena

Revisiting the Reported Period of FRB 20201124A Using MCMC Methods

Jun-Yi Shen and Yuan-Chuan Zou

Fast radio bursts (FRBs) are millisecond-duration radio transients whose physical origin remains uncertain. Magnetar-based models, motivated by observed properties such as polarization and large rotation measures, suggest that FRB emission may be modulated by the magnetar spin period. We present an efficient method to search for periodic signals in repeating FRBs by combining phase folding and Markov Chain Monte Carlo (MCMC) parameter estimation. Our method accelerates period searches. We test the method using observational data from repeater FRB 20201124A, and show that it can recover reported candidate periods.
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Astrophysics of Galaxies

SiO emission in the filamentary Infrared Dark Cloud G035.39-00.33: An ALMA view

Rong Liu, Izaskun Jiménez-Serra, Giuliana Cosentino et al. (+8 more)

Filamentary infrared dark clouds (IRDCs) are believed to represent the initial conditions for massive star and cluster formation. We investigate the IRDC G035.39-00.33 using SiO, H13CO+, CH3OH, and CS emission observed with ALMA at 3.5\arcsec\ resolution (0.05 pc). The SiO emission traces shock activity within the cloud, providing insights into current star formation and cloud formation mechanisms. We identify several regions with broad SiO emission clearly associated with outflows, pinpointing the locations of ongoing star formation across the cloud. The ALMA images also reveal a series of spatially extended SiO emission spots with narrow line profiles, aligned along an arc-like path that is also seen in CS and CH3OH emission. While the broad SiO emission is mainly associated with the main cloud filament, as seen in visual extinction, the narrow SiO arch is located at the edge of the cloud, far from the identified sites of star formation activity. The presence of these arc-like morphologies suggests that large-scale shocks may have compressed the gas in the surroundings of the G035.39-00.33 cloud, shaping its filamentary structure. By inspecting the large-scale radio continuum emission around G035.39-00.33, we find that this IRDC is part of a larger star-forming complex where the densest and coolest material appears at the interacting regions between a Supernova Remnant (SNR) and an expanding HII region. In particular, we hypothesize that this IRDC may be spatially coincident with the ionized expanding gas associated with the previously identified SNR G35.6-0.4. We suggest that collisions between giant molecular clouds and expanding gas flows from interacting SNRs and HII regions may be responsible for the observed arc-like structures. Such shock compressions could play an important role in the formation of IRDCs and in the potential triggering of star formation.
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All authors Rong Liu, Izaskun Jiménez-Serra, Giuliana Cosentino, Jonathan C. Tan, Ashley Thomas Barnes, Francesco Fontani, Paola Caselli, Antonio Martínez-Henares, Chi-Yan Law, Jonathan D. Henshaw, Tie Liu

Earth and Planetary Astrophysics

Predicting the detection yields of giant planets and brown dwarfs with CSST astrometry

Yifan Xuan, Fabo Feng, Zhensen Fu et al. (+3 more)

Chinese Space Station Telescope (CSST), which will begin its scientific operations around 2027, is going to survey the sky area of the median-to-high Galactic latitude and median-to-high ecliptic latitude. The high astrometric precision of the CSST Survey Camera for faint objects enables the detection of a number of giant planets and brown dwarfs around M-dwarfs and brown dwarfs via differential astrometry in its optical survey. In this paper, we predict the number of giant planets and brown dwarfs around stars and brown dwarfs detectable with CSST astrometry. We generate synthetic samples of CSST stellar and substellar sources, and carry out companion injection-recovery simulations in the samples using different occurrence rates for FGK-dwarfs, M-dwarfs, and brown dwarfs. We calculate companion yields based on CSST astrometric precision. Our analysis reveals that over its 10-year mission, the CSST Survey Camera could barely discover giant planets and low-mass BDs around FGK-dwarfs, but is projected to detect 20 - 170 giant planets and low-mass brown dwarfs around M-dwarfs within 300 pc, and 300 - 570 brown dwarf binaries within 600 pc. Therefore, CSST astrometry is likely to significantly increase the current sample of substellar companions around M-dwarfs and brown dwarfs. This sample will deepen our understanding of planet formation and evolution around low-mass stars and brown dwarfs.
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All authors Yifan Xuan, Fabo Feng, Zhensen Fu, Shilong Liao, Zhaoxiang Qi, Yang Chen

High Energy Astrophysical Phenomena

Kilonova and progenitor properties of merger-driven gamma-ray bursts

P. Singh, G. Stratta, A. Rossi et al. (+6 more)

Gamma-Ray Burst (GRB) prompt and afterglow emission, as well as a kilonova (KN), are the expected electromagnetic (EM) counterparts of Binary Neutron Star (BNS) and Neutron Star – Black Hole (NSBH) mergers. We aim to infer the KN ejecta parameters and the progenitor properties by modeling merger-driven GRBs with a claim of KN, good data and robust redshift measurement. We model the afterglow and KN, and perform a Bayesian analysis, within the Nuclear physics and Multi-Messenger Astrophysics (NMMA) framework. The KN emission is modeled with the radiative transfer code POSSIS and for afterglow we use the afterglowpy library. In contrast to previous approaches, our methodology simultaneously models both afterglow and KN. We find that all GRBs in our sample have a KN, but we were unable to confirm or exclude its presence in GRB 150101B. A BNS progenitor is favored for GRB 160821B, GRB 170817A/AT2017gfo, GRB 211211A, and GRB 230307A. For GRB 150101B and GRB 191019A, we obtain a slight preference for NSBH scenario, while a BNS is also viable. For KN emission, we find that the median wind mass $\langle M_{\rm wind}\rangle=0.027^{+0.046}_{-0.019}$ $M_{\odot}$ is larger than the dynamical $\langle M_{\rm dyn}\rangle = 0.012^{+0.007}_{-0.006}$ $M_{\odot}$. We find that $M_{\rm wind}$ and the beaming corrected kinetic energy of the jet can be attributed as $log(M_{\rm wind})=-20.23+0.38\,log(E_{0,J})$. We confirm the results of numerical simulation that $\tilde\Lambda$ increases with decrease in $\mathcal{M}_{\rm \,Chirp}$. Our work shows that EM modeling can be effective for probing the progenitors, and for the first time presents the progenitor properties of a sizable sample of merger-driven GRBs.
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All authors P. Singh, G. Stratta, A. Rossi, P.T.H. Pang, M. Bulla, F. Ragosta, A. De Rosa, D.A. Kann, F. Cogato

Astrophysics of Galaxies

The Dependence of the Extinction Coefficient on Reddening for Galactic Cepheids

Huajian Wang, Xiaodian Chen and Shu Wang

Cepheids are fundamental distance indicators, playing a crucial role not only in the cosmic distance ladder but also in mapping the structure, kinematics, and extinction properties of the Milky Way. Using high-precision photometry and parallaxes from $Gaia$ Data Release 3, we identify a significant anti-correlation between the $G$-band extinction coefficient and reddening for Galactic Cepheids, quantified as $R_G = 1.918 \pm 0.060 - (0.106 \pm 0.022)\,E(G_{\mathrm{BP}} - G_{\mathrm{RP}})$. We propose that this anti-correlation arises from the combination of the non-linear effects inherent to the broad $Gaia$ bands and the $R_V$ variations caused by diverse interstellar medium. Adopting a fixed $R_G$ would not only lead to an overestimation of the metallicity dependence of Cepheid luminosities, but also systematically underestimate the distances to highly reddened Cepheids. Moreover, the strong reddening dependence of $R_G$ makes Wesenheit function based on it unsuitable for highly reddened Cepheids, since the definition of Wesenheit magnitudes requires a fixed extinction coefficient. In contrast, infrared-based distances, being less affected by non-linear effects and insensitive to $R_V$, provide the most reliable Cepheid distances at present. This work emphasizes the importance of accurately determining $R_V$ for Galactic Cepheids and accounting for non-linear effects in distance measurements, particularly in the optical bands.
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High Energy Astrophysical Phenomena

New Constraints on Cosmic-ray boosted Sub-GeV Dark Matter via Light Mediators

Yang Yu, Guan-Sen Wang, Bo Zhang et al. (+3 more)

Traditional direct detection experiments lack the sensitivity to probe the sub-GeV dark matter (DM), primarily due to the low energy of the expected nuclear recoils. In this work, we investigate cosmic-ray (CR) upscattering as a mechanism to accelerate DM particles to detectable velocities in underground experiments. By analyzing four models of DM-nucleon interactions – namely scalar, vector, pseudoscalar, and axial-vector mediators – we derive constraints on the coupling parameters using data from the LZ, XENON, and Borexino experiments, covering mediator mass from $10^{-6}$ to $1$ GeV. As the mediator mass varies, the shift in dominance between momentum transfer and mediator mass leads to a turnover in the constraints around $10^{-2}$–$10^{-3}~\mathrm{GeV}$. Our results extend the reach of direct detection into the sub-GeV window and clarify the critical role of momentum dependence in light-mediator scenarios.
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All authors Yang Yu, Guan-Sen Wang, Bo Zhang, Tian-Peng Tang, Bing-Yu Su, Lei Feng

High Energy Astrophysical Phenomena

SN 2022acko: a low-luminosity SNe IIP with signs of early circumstellar interaction

Lin Han, Zhang Jujia, Wang Xiaofeng et al. (+13 more)

We present optical-ultraviolet photometry and optical spectra for the type II supernova (SN) 2022acko. The spectroscopic observations span phases from $\sim$ 1.5 to $\sim$ 60 days after the explosion, while the light curve was observed up to $\sim$ 300 days. The V-band peak is $-15.5 \pm 0.3$ mag, suggesting that SN 2022acko is a low-luminosity SN II (LLSN). The overall observed properties of SN 2022acko are consistent with those produced by a lower mass progenitor ($\rm M_{ZAMS} \sim $9-10M$_{\odot}$). The spectra at $t=1.5$d and $t=2.5$d exhibit a broad emission feature peaking near 4600 Å (the “ledge” feature), which we interpret as blueshifted He II 4686 Ålines arising from the ionized ejecta. Moreover, a possible flash-ionized (FI) emission line of H$\alpha$ (FWHM $\sim 1100\ \rm km \ s^{-1}$) was superposed on the broad emission component of H$\alpha$ P-Cgyni profile in the $t=1.5$d spectrum. Assuming an ejecta velocity of $\rm 12000\ km\ s^{-1}$, the rapid disappearance of this narrow H$\alpha$ emission line within two days suggests highly confined CSM within $\sim \rm 2\times10^{14}\, cm$. Assuming a spherically symmetric CSM, the mass loss rate within this radius is estimated to be $\rm \sim 5 \times 10^{-4} M_{\odot} \ year^{-1}$ based on our hybrid light curve model. The early “ledge” feature observed in SN 2022acko have also been observed in other SNe II, suggesting that early-phase circumstellar interaction (CSI) is more common than previously thought.
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All authors Lin Han, Zhang Jujia, Wang Xiaofeng, Hu Maokai, Zha Shuai, Xiang Danfeng, Li Liping, Reguitti Andrea, Zhang Xinghan, Cai Yongzhi, Wang Zhenyu, Zhao Zeyi, Zhai Qian, Huang Fang, Lin Weili, Bai Jinming

High Energy Astrophysical Phenomena

Interpreting the diversity of afterglow emission from radio-detected tidal disruption events with instantaneous and delayed outflows

Yuri Sato, Mukul Bhattacharya, Jose Carpio et al. (+2 more)

Tidal disruption events (TDEs) occur when a star is gravitationally disrupted by the tidal field of a supermassive black hole during a close encounter. Radio emission has recently been detected in TDEs and is commonly attributed to synchrotron radiation from both wind and jetted outflows. However, several TDEs exhibit bright radio flares at late times, which cannot be easily explained if the wind is launched promptly after the stellar disruption. The radio light curves of TDEs with delayed radio flares are modeled using three scenarios: an instantaneous wind, a delayed wind, and a delayed relativistic jet. We show that the instantaneous wind model struggles to reproduce delayed radio flare events, indicating the necessity of an additional delayed outflow component. In contrast, the delayed wind model provides a consistent explanation for the observed radio phenomenology, successfully reproducing events both with and without delayed radio flares. For some delayed radio flare events (e.g., ASASSN-15oi and AT 2019dsg), both the delayed wind and delayed jet models can reproduce the observed radio light curves, making it challenging to distinguish between these scenarios based on radio data alone. To break this degeneracy, we present calculations of detailed multiwavelength spectra from radio to x-ray and very-high-energy gamma-ray bands, including both synchrotron and inverse-Compton processes. Within this framework, the delayed jet model produces x-ray and optical emission detectable at typical TDE distances, in contrast to wind-driven scenarios. Our results highlight how multiwavelength campaigns offer effective means to distinguish between possible outflow mechanisms. We apply our model to AT 2025aarm, which is one of the closest TDEs that has been observed, and show the importance of x-ray observations.
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All authors Yuri Sato, Mukul Bhattacharya, Jose Carpio, Jewel Capili, Kohta Murase

High Energy Astrophysical Phenomena

Unveiling Multimessenger Emission from Hidden Cores of Microquasars

Yu-Jia Wei, Kohta Murase and B. Theodore Zhang

Microquasars are radio-emitting X-ray binaries with relativistic jets and are established sources of $\sim 100$~TeV gamma rays, making them promising candidates for cosmic-ray acceleration. Motivated by recent detections of $\sim 100~$TeV photons from Cygnus~X-1 and multi-PeV photons from Cygnus~X-3, we employ the Astrophysical Multimessenger Emission Simulator (AMES) to model their multimessenger emission from radio to ultrahigh-energy gamma rays. Our modeling suggests that particle acceleration is extremely efficient in the jet region. The observed $\gtrsim 0.1$~PeV gamma rays can originate from either $p\gamma$ or $pp$ interactions, depending on the location and physical conditions of the emission region, while also reproducing the lower-energy spectra. These configurations yield observationally testable predictions. In the poorly constrained $0.1$-$10$~TeV band, the models predict either a deep valley, a mild suppression, or a power-law spectrum. Additionally, models involving compact emission regions comparable to the orbital separation predict strong variability, while those invoking more extended and static external zones show more stable behavior. We also provide a possible qualitative explanation for the energy-dependent modulation patterns, relying primarily on changes in the Doppler factor and external $\gamma\gamma$ absorption. In particular, explaining the PeV emission from Cygnus~X-3 favors a compact emission region, for which a magnetic field strength of order $10^2~\mathrm{G}$ is required. Finally, after accounting for pion and muon cooling, the predicted neutrino flux is suppressed, implying that detection is more challenging than previously thought.
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Astrophysics of Galaxies

MAMMOTH-LyC: Investigating the Role of Galaxy Mergers in a Strong Lyman Continuum Leaker at $z=2.39$

Shengzhe Wang, Xin Wang, Matthew A. Malkan et al. (+16 more)

The MAMMOTH-LyC survey is a cycle 30 Hubble Space Telescope (HST) medium program obtaining 18-orbit-deep WFC3/UVIS F225W imaging in two massive galaxy protocluster fields at $z\sim2.2$. We introduce this survey by reporting the discovery of J1244-LyC1, a strong Lyman continuum (LyC) leaker at $z = 2.39$, exhibiting clear merger signatures. J1244-LyC1 has a highly significant ($6\sigma$) LyC detection, corresponding to an absolute escape fraction of $f_{\mathrm{esc}} \! =\!36\%\pm6\%$ ($1\sigma$). The LyC emission is spatially resolved into multiple peaks that coincide with the system's disturbed morphology, confirming genuine multi-site LyC leakage. With a stellar mass of $10^{10.2}{M_\odot}$, J1244-LyC1 is both the first confirmed high-redshift LyC-leaking merger and the most massive LyC emitter known to date. We interpret J1244-LyC1 as a merger-driven starburst system in which tidal interactions have disrupted the interstellar medium, creating multiple low-column-density pathways that facilitate LyC escape. This discovery provides the first direct evidence of spatially resolved LyC escape in a merging system, offering new insight into the potential role of major mergers in driving the cosmic reionization.
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All authors Shengzhe Wang, Xin Wang, Matthew A. Malkan, Harry I. Teplitz, Rebecca L. Davies, Karl Glazebrook, Keunho J. Kim, Themiya Nanayakkara, Hang Zhou, Yiming Yang, Chao-Wei Tsai, Yuxuan Pang, Zheng Cai, Xiaohui Fan, Alaina Henry, Zihao Li, Dong Dong Shi, Xian Zhong Zheng, Zhiyu Yan

Instrumentation and Methods for Astrophysics · Cross-listed from hep-ex

Search for Annual Modulation in Combined ANAIS 112 and COSINE 100 Data using Bayesian Model Comparison

Om Godse and Shantanu Desai

We perform a Bayesian model comparison test between a sinusoidal modulation model and a constant value model using about three years of combined COSINE-100 and ANAIS-112 data. We use both uniform priors and normal priors (based on DAMA best-fit values) for the angular frequency and phase of the cosine signal. We find natural log of Bayes factor for the cosine model compared to the constant value model to be less than 1.15 for the data in both 1-6 keV and 2-6 keV energy intervals. This shows that there is no evidence for cosine signal from dark matter interactions in the combined ANAIS-112/COSINE-100 data. Our analysis codes have also been made publicly available.
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Astrophysics of Galaxies

The GLASS-JWST Early Release Science Program. V. H$\alpha$ luminosity functions at $z\sim1.3$ and $z\sim2.0$

Yuxuan Pang, Xin Wang, Tommaso Treu et al. (+11 more)

We present H$\alpha$ luminosity function (LF) measurements at redshifts $z\sim1.3$ and $z\sim2.0$ using JWST NIRISS grism data from the GLASS-JWST survey. Based on emission lines spectroscopically identified in the F115W, F150W and F200W filters, we select 99 H$\alpha$ emitters. Through detailed effective volume and completeness analysis for each source, we construct the H$\alpha$ LF in two redshift bins. Thanks to the sensitivity of NIRISS WFSS and gravitational lensing magnification, our sample reaches intrinsic H$\alpha$ luminosities $\sim$10 times deeper than previous grism surveys, down to $L_{\rm H\alpha}\sim10^{40.5}~\rm erg~s^{-1}$ at $z\sim1.3$ and $L_{\rm H\alpha}\sim10^{40.9}~\rm erg~s^{-1}$ at $z\sim2.0$ with completeness larger than 0.8, corresponding to star formation rates of 0.4 and 1.0 $M_{\odot}~\rm yr^{-1}$, respectively. We robustly constrain the faint-end slope of the H$\alpha$ luminosity function to be $-1.50^{+0.14}_{-0.08}$ at $z\sim1.3$ and $-1.60^{+0.17}_{-0.09}$ at $z\sim2.0$ after considering the cosmic variance of $\sim 20\%$, consistent with previous estimations. The emission-line samples presented here will enable further detailed studies of galaxy properties including metallicities. We find a negligible contribution from bright active galactic nuclei in our sample. We estimate integrated cosmic star formation rate densities of $0.097^{+0.015}_{-0.016}~M_{\odot}~\rm yr^{-1}~Mpc^{-3}$ at $z\sim1.3$ and $0.129^{+0.025}_{-0.030}~M_{\odot}~\rm yr^{-1}~Mpc^{-3}$ at $z\sim2.0$. The methodology presented here can be readily applicable to other JWST slitless spectroscopic datasets and future wide-field slitless surveys, including those from Euclid, Roman, and the Chinese Space Station Telescope.
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All authors Yuxuan Pang, Xin Wang, Tommaso Treu, Qianqiao Zhou, Shengzhe Wang, Xue-Bing Wu, Maruša Bradač, Karl Glazebrook, Nicha Leethochawalit, Matthew A. Malkan, Themiya Nanayakkara, Benedetta Vulcani, Peter J. Watson, Hu Zhan

Instrumentation and Methods for Astrophysics

Why Machine Learning Models Systematically Underestimate Extreme Values II: How to Fix It with LatentNN

Yuan-Sen Ting

Attenuation bias – the systematic underestimation of regression coefficients due to measurement errors in input variables – affects astronomical data-driven models. For linear regression, this problem was solved by treating the true input values as latent variables to be estimated alongside model parameters. In this paper, we show that neural networks suffer from the same attenuation bias and that the latent variable solution generalizes directly to neural networks. We introduce LatentNN, a method that jointly optimizes network parameters and latent input values by maximizing the joint likelihood of observing both inputs and outputs. We demonstrate the correction on one-dimensional regression, multivariate inputs with correlated features, and stellar spectroscopy applications. LatentNN reduces attenuation bias across a range of signal-to-noise ratios where standard neural networks show large bias. This provides a framework for improved neural network inference in the low signal-to-noise regime characteristic of astronomical data. This bias correction is most effective when measurement errors are less than roughly half the intrinsic data range; in the regime of very low signal-to-noise and few informative features. Code is available at https://github.com/tingyuansen/LatentNN.
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Sunday 28 December

Instrumentation and Methods for Astrophysics

Sustainable, Local Socio-Economic Development Through Astronomy

Joyful E. Mdhluli and IAU Office of Astronomy for Development

Astronomy, often perceived as a distant or luxury science, holds immense potential as a driver for sustainable local socio-economic development. This paper explores how astronomy can create tangible benefits for communities through education, tourism, technology transfer, and capacity building. Using case studies from South Africa, Chile, Indonesia, and India, we demonstrate how astronomical facilities and initiatives have stimulated local economies, generated employment, supported small enterprises, and enhanced STEM participation, while simultaneously inspiring a sense of shared global heritage. The analysis identifies both successes and challenges, including unequal benefit distribution, limited local ownership, and sustainability gaps once external funding ends. Building on these lessons, we propose a practical framework/guidelines for designing, implementing, and evaluating astronomy-based community initiatives, rooted in participatory engagement and aligned with the UN Sustainable Development Goals (SDGs). This paper positions astronomy as a catalyst for inclusive growth, demonstrating that investment in the cosmos can translate into grounded, measurable benefits for people and places on Earth.
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High Energy Astrophysical Phenomena

Exploring the Limits of Machine Learning Classification of Neutron Star Matter Models

Wasif Husain

We investigate the extent to which supervised machine learning techniques can distinguish between neutron-star matter models using macroscopic and oscillation-related quantities derived from theoretical stellar configurations. Four representative matter scenarios nucleonic, hyperonic, dark matter admixed, and strange matter models are considered, and a synthetic dataset is constructed from solutions of the Tolman Oppenheimer Volkoff equations under fixed microphysical and transport assumptions. A shallow neural network classifier is trained on physically motivated features, including gravitational mass, stellar radius, and oscillation related quantities, to evaluate classification performance across the model space. Rather than aiming at unique composition inference, the analysis focuses on identifying regimes of distinguishability and intrinsic degeneracy between models. We find that certain matter scenarios can be separated under controlled assumptions, while others exhibit substantial overlap, reflecting fundamental similarities in their effective equations of state. These results demonstrate that machine learning provides a useful computational framework for mapping the limits of model classification in neutron-star studies, clarifying where inference is feasible and where it remains intrinsically model dependent. The methodology is readily extensible to more complex microphysics and to future multi messenger datasets.
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Instrumentation and Methods for Astrophysics

Two birds with one stone: simultaneous realization of both Lunar Coordinate Time and lunar geoid time by a single orbital clock

Tian-Ning Yang, Ren-Fang Geng, Jing Zhang et al. (+3 more)

Context. Among options for definition of the lunar reference time, the option taking Lunar Coordinate Time (O1) has its simplicity but cannot be realized by any clock without steering, while another option adopting the lunar geoid (selenoid) proper time (O2) has its convenience for users on the lunar surface but would bring a new scaling of spatial coordinates and mass parameter of the Moon. Aims. We propose a ”time aligned orbit” that the readings of an ideal clock in this orbit could equal to the selenoid proper time in O2 and these readings could be converted to Lunar Coordinate Time in O1 by a known linear transformation. Methods. We show that there exist the time aligned orbit around the Moon with its semi-major axis of about 1.5 lunar radius slightly depending on its inclination. We conduct a set of numerical simulations to assess to what extent a clock on these orbits could realize O2 in a more realistic lunar environment. Results. We find that the proper time in our simulations would desynchronize from the selenoid proper time up to 190 ns after a year with a frequency offset of 6E-15, which is solely 3.75% of the frequency difference in O2 caused by the lunar surface topography. These numbers might be further reduced to 13 ns and 4E-16, if we could account for the deviation of the mean orbits in our simulations from the nominal ones. Conclusions. One might simultaneously realize O1 and O2 by deployment of a single clock in the time aligned orbit. This approach also has its scalability for other terrestrial planets beyond the Earth-Moon system.
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All authors Tian-Ning Yang, Ren-Fang Geng, Jing Zhang, Chong Yang, Yong Huang, Yi Xie

Astrophysics of Galaxies

Finding Quasars behind the Galactic Plane. IV. Candidate Selection from Chandra with Random Forest

Xu Zhang, Yanli Ai, Yanxia Zhang et al. (+8 more)

Quasar samples remain severely incomplete at low Galactic latitudes because of strong extinction and source confusion. We conduct a systematic search for quasars behind the Galactic plane using X-ray sources from the Chandra Source Catalog (CSC 2.1), combined with optical data from Gaia DR3 and mid-infrared data from CatWISE2020. Using spectroscopically confirmed quasars and stellar-type objects from data sets including DESI, SDSS, and LAMOST, we apply a Random Forest classifier to identify quasar candidates, with stellar contaminants suppressed using Gaia proper-motion constraints. Photometric redshifts are estimated for the candidates using a Random Forest regression model. Applying this framework to previously unclassified CSC sources, we identify 7570 quasar candidates, including 1060 Galactic Plane Quasar (GPQ) candidates at |b|<20{\deg}, of which 551 are high-confidence candidates. Relative to the previously known GPQ sample, our selected GPQs reach lower optical and X-ray fluxes, improving sensitivity to low-flux GPQs. In addition, both the GPQ candidates and known GPQs display harder X-ray spectra than the all-sky quasar sample, consistent with increased absorption through the Galactic plane. Pilot spectroscopy confirms two high-confidence GPQ candidates as quasars at spectroscopic redshifts of z=1.2582 and z=1.1313, and further spectroscopic follow-up of the GPQ sample is underway. This work substantially improves the census of GPQs and provides a valuable target sample for future spectroscopic follow-up, enabling the use of GPQs to refine the reference frames for astrometry and probe the Milky Way interstellar and circumgalactic media with the absorption features of GPQs.
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All authors Xu Zhang, Yanli Ai, Yanxia Zhang, Yuming Fu, Xue-Bing Wu, Zhiying Huo, Wenfeng Wen, Jiayuan Zhou, Dexuan Kong, Linfeng Zeng, Heng Wang

High Energy Astrophysical Phenomena · Cross-listed from physics.comp-ph

Reconstructing Relativistic Magnetohydrodynamics with Physics-Informed Neural Networks

Corwin Cheung, Marcos Johnson-Noya, Michael Xiang et al. (+2 more)

We construct the first physics-informed neural-network (PINN) surrogates for relativistic magnetohydrodynamics (RMHD) using a hybrid PDE and data-driven workflow. Instead of training for the conservative form of the equations, we work with Jacobians or PDE characteristics directly in terms of primitive variables. We further add to the trainable system the divergence-free condition, without the need of cleaning modes. Using a novel MUON optimizer implementation, we show that a baseline PINN trained on early-time snapshots can extrapolate RMHD dynamics in one and two spatial dimensions, and that posterior residual-guided networks can systematically reduce PDE violations.
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All authors Corwin Cheung, Marcos Johnson-Noya, Michael Xiang, Dominic Chang, Alfredo Guevara

Earth and Planetary Astrophysics

A Linearized Approach to Radial-Velocity Extraction. II: Shot-Noise-Limited Precision via Spectral Factorization

Sahar Shahaf and Barak Zackay

We generalize the short-time Fourier transform (STFT) formalism for radial velocity extraction to cases where the underlying spectral components are unknown. The method factorizes a spectroscopic time series into principal spectra and time-dependent kernels, enabling simultaneous recovery of both. In Fourier space, each inverse-wavelength slice is decomposed by singular value decomposition, and radial velocity shifts are inferred from phase differences between epochs. In the high-SNR regime, this provides a linearized and statistically tractable estimate of differential velocities. The method is validated on synthetic and SOAP simulations and applied to EXPRES observations of HD 34411 and $\tau$ Ceti, recovering coherent signals and reaching the instrumental precision limit of ~30 cm/s. Apart from p-mode modulation, the residuals show no significant long-term correlations and allow the detection of signals with semi-amplitudes down to ~50 cm/s with $\lesssim10$ cm/s uncertainty. The framework thus enables extreme-precision radial velocity measurements in the presence of spectral variability, representing a step toward detecting and characterizing Earth-like planets around solar-type stars.
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Instrumentation and Methods for Astrophysics

Dark matter direct detection: status, results and future plans

Laura Baudis

Direct dark matter detection experiments search for rare signals induced by hypothetical, galactic dark matter particles in low-background detectors operated deep underground. I will briefly review the direct detection principles, the expected signals and backgrounds, and the main experimental techniques. I will then discuss the status of ongoing experiments aiming to discover new particles in the keV - TeV mass range, as well as future detectors and their sensitivity.
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Astrophysics of Galaxies

Empirical Relationship Between Dark Matter and Baryon Profiles for Solving the Core-Cusp and Diversity Problems of Galaxies

Kento Kamada

The rotation velocity profiles of galaxies (rotation curves) remain unexpectedly flat at large distances, where visible matter alone should make the rotation velocity decrease with radius. To explain this missing gravity, conventional frameworks assume unseen mass or alternative gravitational effects. While the dark matter hypothesis has become the standard paradigm, this framework faces persistent small-scale challenges, such as the core-cusp and diversity problems, and struggles to explain the observed correlation between dark matter and baryons, as evidenced by the Radial Acceleration Relation and the baryonic Tully-Fisher relation. Here, we introduce a simple empirical law for the dark matter in a single galaxy, stating that the dark matter energy density $\rho_{\mathrm{DM}}$ is related to the baryonic gravitational potential $U_b$ and the total baryonic mass of the galaxy $M_b$ as $\rho_{\mathrm{DM}} = K M_b^{-3/2} (U_b/c^2)^2$. When applied to 122 galaxies from the SPARC database with a single fitting parameter $K$, this empirical equation reproduces both the diverse inner structures and outer flat regions of the observed rotation curves, resolving the core-cusp and diversity problems. In each galaxy, the observed velocity data for various distances were well fitted, with the minimum $\chi^2/\mathrm{dof}$ value around unity, by the rotation curve calculated from this empirical equation. The fitted $K$ values for the 122 galaxies were concentrated within a narrow range, and the minimum $\chi^2/\mathrm{dof}$ values were significantly reduced for galaxies with specific stellar mass-to-light ratio data given by the THINGS survey. These results demonstrate the validity of the empirical law. The success of the empirical law may suggest the existence of new fields interacting with baryons.
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