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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 28 May

Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph

Propagation of waves in weakly ionized two-fluid plasmas. II. Nonlinear Alfvénic waves

David Martínez-Gómez

Weakly ionized plasmas can be found in the lower layers of the solar and stellar atmospheres and in structures such as prominences and spicules. A variety of density perturbations and bulk flows detected in these environments have been explained as the result of the ponderomotive force generated by nonlinear Alfvénic waves. In addition, the dissipation of the energy carried by these waves leads to heating of the plasma. Here, we use a two-fluid model to study the combined influence of Hall's current and elastic collisions between ions and neutrals on the propagation of linearly and circularly polarized transverse waves in weakly ionized plasmas. We derive analytical expressions for the damping and heating rates, showing their dependence on the strength of the collisional coupling and on the polarization state. We also perform numerical simulations to investigate the nonlinear generation of density perturbations and bulk flows related to the ponderomotive force and the energy dissipation by the ion-neutral interaction. We find that the nonlinear perturbations associated with the circularly polarized eigenmodes do not show the oscillatory motions typically caused by linearly polarized eigenmodes, but they retain the non-oscillatory bulk flows. We also briefly discuss how in weak coupling conditions the nonlinear dynamics of the neutral fluid is mainly driven by the wave energy dissipation while the ponderomotive force only directly acts on the charged fluid, resulting in different amplitudes of the longitudinal motions and the perturbations of density and temperature.
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Solar and Stellar Astrophysics

The outer rings of SN 1987A from year 1994 to 2024: morphology, light curves, and optical to mid-infrared spectra

Sophie Rosu, Elko Gerville-Reache, Steven Thomas et al. (+14 more)

The outer rings (ORs) of Supernova (SN) 1987A were ejected ~20000 years before the explosion. Their characterisation is crucial for constraining the properties of the progenitor of this famous SN. While numerous studies investigated in detail the ejecta, equatorial ring (ER), and reverse shocks, few were dedicated to the ORs. We fill this gap and investigate the ORs physical properties. We analyse data obtained over a long temporal period, from multiple instruments, and over a wide wavelength range from optical to mid-infrared of the northern and southern ORs (NOR and SOR). We combine observations taken with HST between 1994 and 2022, VLT/MUSE in 2023, and JWST in 2022 and 2024. We measure emission flux in the ORs in HST and JWST/NIRCam images. We extract optical and mid-infrared spectra for the ORs in MUSE and JWST/MIRI/MRS data and measure line emission fluxes. We analyse the evolution of the ORs clumps' morphology over time with HST. The optical lightcurves of the ORs have shown a steady decline with time over the last 30 years. It is expected as the ORs were ionised by the initial SN UV-flash and are since then fading. The observations do not show any sign of interaction of the SN ejecta with the ORs. We estimated the decay times for [O III] to be 900 and 680 days for the NOR and SOR, and for Halpha+[N II] to be 15870 and 7160 days for the NOR and SOR. We constrained the temperature from the optical [N II] lines to 13400-16900K and 11800-14500K for the NOR and SOR. We constrained the electron density from the optical [S II] lines to 610-670cm-3 and 720-790cm-3 for the NOR and SOR. The spectra of the ORs differ significantly from the spectrum of the ER in lines detected and line ratios. The ORs will likely keep on fading for the next years, until the SN ejecta sweep them up. Continued monitoring of SN1987A and its ring system at all wavelengths is essential to capture this instant.
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All authors Sophie Rosu, Elko Gerville-Reache, Steven Thomas, Josefin Larsson, Patrick J. Kavanagh, Jason Spyromilio, Claes Fransson, Christa Gall, Robert D. Gehrz, Alec S. Hirschauer, Olivia C. Jones, Robert P. Kirshner, Peter Lundqvist, Mikako Matsuura, Margaret Meixner, Beth Sargent, Jesper Sollerman

Instrumentation and Methods for Astrophysics

Extending Hubble into the 2030s to Resolve the Physics of LyC Escape

Cody Carr, Stephan McCandliss, Michelle Berg et al. (+6 more)

Current observations with the James Webb Space Telescope (JWST) suggest that star-forming galaxies produce enough ionizing (LyC; $\lambda < 91.2$ nm) photons to drive cosmic reionization, but the efficiency with which these photons escape their host galaxies remains uncertain. Absorption by the neutral intergalactic medium progressively suppresses direct LyC detections above redshift $z\sim3$, forcing astronomers to rely on indirect diagnostics of LyC escape calibrated at low redshift. Low-resolution ultraviolet observations of high-redshift analogs obtained with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope (HST) have been critical for developing these diagnostics. These studies suggest that stellar feedback plays a central role in regulating LyC escape, although the role of galactic winds and the underlying physical mechanisms remain poorly constrained. High-resolution spectroscopy blueward of 160.0 nm (rest-frame) is required to resolve the kinematic structure of the winds and reveal the physics governing LyC escape. Such observations are currently only possible with HST and represent a major science driver for the future Habitable Worlds Observatory (HWO). Extending the lifetime of HST and prioritizing ultraviolet observations are essential for interpreting current JWST studies of the early Universe and important preparatory science for HWO.
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All authors Cody Carr, Stephan McCandliss, Michelle Berg, Renyue Cen, Kevin France, Matthew Hayes, Alaina Henry, M. S. Oey, Alberto Saldana-Lopez

High Energy Astrophysical Phenomena

Long-Duration GRB 211211A: Internal Energy Dissipation Driven by a Long-Lived Magnetar

Nissim Fraija

The most promising candidate for short-duration gamma-ray bursts (GRBs) is the merger of two neutron stars (NSs), which produces kilonovae (KNe) in the aftermath. This merging can result in a fast-spinning, highly magnetic NS, known as a millisecond magnetar, whose accretion processes can explain different phases in GRBs. The identification of a KN associated with the atypical long-duration GRB 211211A contradicted the classification schemes of the GRB progenitors. This study presents a comprehensive analysis of gamma- and X-ray observations, focusing on modeling X-ray data from a long-lived magnetar with two distinct fallback accretion rates ($\dot{M}\propto t^0$ and $\propto t^{\frac12}$) during the initial phase. The internal energy dissipation of the magnetar spin-down power, through the magnetization parameter, accounts for the long duration of the prompt gamma-ray episode observed in GRB 211211A. Furthermore, we provide a satisfactory explanation for the precursor and extended emissions following the prompt episode within the magnetar model with two fallback accretion rates. Although these accretion rates explain different characteristics, the model that incorporates a variable accretion rate offers a more accurate description. The current scenario for the GRB 211211A observations aligns with a compact binary merger that produces a long-lived magnetar instead of an immediate black hole.
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Earth and Planetary Astrophysics

An archival summary: 15 years of ALMA observations on disks and planet formation

Nicolas T. Kurtovic, Lizxandra Flores-Rivera, Laura M. Perez et al. (+15 more)

The Atacama Large (sub-)millimeter Array (ALMA) has been in scientific operations for almost 15 years. We celebrate this achievement by providing a summary of the “Disks and planet formation” scientific category, with an emphasis on the disks located in the nearby star-forming regions. As of the beginning of February 2026, ALMA had observed 3933 independent coordinates, which we analyzed by their location in the sky, frequency coverage, exposure time, spectral line coverage, and angular resolution. We encourage the community to explore new scientific questions that are made possible through the archival datasets.
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All authors Nicolas T. Kurtovic, Lizxandra Flores-Rivera, Laura M. Perez, Miguel Vioque, Myriam Benisty, Felipe Alarcón, Marcelo Barraza-Alfaro, Pietro Curone, Kiyoaki Doi, Sierra Grant, Haochang Jiang, Akimasa Kataoka, Feng Long, Álvaro Ribas, Anibal Sierra, Lucas Stapper, Milou Temmink, Francesco Zagaría

Solar and Stellar Astrophysics

Detection of unidentified molecular pure rotational lines in C-rich PNe I. The fullerene-containing PN IC 418

T. Huertas-Roldán, J. P. Fonfría, J. Alcolea et al. (+7 more)

Molecular emission is observed in a wide variety of astrophysical environments, yet a substantial fraction of spectral features detected at mm wavelengths remains unidentified. Identifying these features is essential for constraining the inventory of interstellar and circumstellar molecules and for understanding the chemical pathways operating in evolved stars. In this study, we investigate a set of weak unidentified molecular features detected in the C-rich PN IC 418. We aim to constrain the nature of their molecular carriers and assess their possible connection to fullerene-related chemistry. High-sensitivity observations at 2, 3, and 7 mm were carried out using the RT40m and IRAM 30m radio telescopes. The spectral features found in these data sets were compared with public molecular spectroscopic databases. Spectral-pattern searches and line fits were performed under linear, symmetric, and asymmetric rotor approximations to estimate rotational constants of potential molecular carriers. We report the detection of 20 weak (SNR~2-13) unidentified features (UFs), none of which can be attributed to mm radio recombination lines, instrumental artifacts, or known molecular species. The observed features are inconsistent with the regular line spacing expected from linear molecules or symmetric rotors, although a recurrent doublet-like pattern is identified. The estimated rotational constants (B~2 500-3 660 MHz) suggest carriers with 4-13 atoms and are incompatible with those expected from C60 derivatives (B~100 MHz). Non-planar carbonaceous molecules produced during the destruction/processing of hydrogenated amorphous carbon (HAC) grains are suggested as promising candidates. The catalog of UFs presented here is made publicly available to facilitate future comparisons with laboratory measurements and theoretical calculations aimed at identifying their molecular carriers.
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All authors T. Huertas-Roldán, J. P. Fonfría, J. Alcolea, D. A. García-Hernández, S. Mato, J. J. Díaz-Luis, R. Barzaga, A. Manchado, V. Bujarrabal, M. A. Gómez-Muñoz

Solar and Stellar Astrophysics

Quantifying the effect of passband on observations in the Ca II K line

Ajay Kumar Yadav, Theodosios Chatzistergos, Natalie Krivova et al. (+33 more)

Full-disk observations of the Sun in the Ca II K line have been carried out since the late 19th century at various observatories worldwide. These long-term records of solar activity are crucial for reducing discrepancies among solar irradiance reconstructions and for advancing our understanding of the solar dynamo. To construct a consistent composite record, data from different observatories must be cross-calibrated to account for variations in spectral passband and spatial resolution, which are the primary sources of discrepancies between archives. In this study, we use high spectral and spatial resolution observations in the Ca II K line from the state-of-the-art Sunrise III mission to emulate different passbands and derive empirical contrast-contrast relationships between them. We find that these relationships are well described by a power law and provide coefficients for different combinations of passband widths in the range 0.1–9 Angstroms and spatial resolutions between 1 arcsec and 6 arcsec. Applying such a relationship to observations from two major Ca II K archives demonstrates its potential to improve their cross-calibration. The results provide a foundation for the construction of a consistent, century-long time series of solar activity from historical and modern Ca II K observations.
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All authors Ajay Kumar Yadav, Theodosios Chatzistergos, Natalie Krivova, Sami K. Solanki, Francisco A. Iglesias, Ilaria Ermolli, Andreas Lagg, Achim Gandorfer, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alex Feller, Tino L. Riethmüller, Alberto Álvarez-Herrero, Masahito Kubo, H. N. Smitha, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Laurent Gizon, Johannes Hoelken, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović, Yasuhito Narita

Earth and Planetary Astrophysics

Dust dynamics in disk dust traps and late planetesimal formation

Maya Tatarelli, Alessandro Morbidelli and Elena Lega

The streaming instability is the leading model for planetesimal formation in protoplanetary disks, but it typically operates within the first ~Myr. In the Solar System, however, some planetesimals (the chondrite parent bodies) formed 2-4 Myr after disk formation, implying that dust must have been retained for extended periods. Pressure bumps efficiently trap dust, but trapping alone does not guarantee planetesimal formation: even modest gas turbulence can inhibit vertical settling and radial concentration, preventing dust density from reaching Hill density. This motivates the study of alternative dust-gas instabilities, such as the Dusty Rossby Wave Instability (DRWI). We investigate the viability of such instabilities in global disk simulations using the multi-fluid code fargOCA. We first reproduce previous 2D shearing-box results in a global 2D viscous disk and characterize the dust clumping produced by the DRWI. We find that the instability is suppressed in fully 3D viscous disks by unperturbed high-z gas layers caused by dust settling near the midplane. We then explore the inviscid limit and find that multiple dust sub-rings form, concentrating solids into thin ring structures. These would appear observationally as a single radially broad, vertically thin ring, explaining observed protoplanetary disk rings without invoking anisotropic turbulence. Dust concentrations in the sub-rings may remain below the threshold for gravitational collapse, but gas photoevaporation enhances dust settling and radial concentration, eventually forming dense dust clumps in both viscous and inviscid cases. We conclude that planetesimal formation within dust-trapping pressure bumps is favored in very low-viscosity disks at late evolutionary stages, after sufficient gas removal by photoevaporation. This is consistent with the inferred late formation of chondrite parent bodies in the Solar System.
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Astrophysics of Galaxies

High-S/N Quasar Observations with HST/COS: Deep Fields for Spectroscopy

Andrew J. Fox, Jerry Kriss, Philipp Richter et al. (+49 more)

Hubble is still in prime observing condition for making transformative discoveries in UV astronomy. In this white paper we describe the science case for a deep (S/N>30) UV spectroscopic survey with HST/COS targeting approximately 20 QSOs at 0.5<z<1.5 at good resolution (20 km/s). This survey would capitalize on our current UV capability, produce a legacy dataset enabling community science in many areas of galactic and extragalactic research, and pioneer a path for future UV science with the Habitable Worlds Observatory. Such high-S/N spectra are largely missing from the MAST archives, and would be analogous to the deep Hubble imaging fields (HDF, UDF, Frontier Fields) that have been enormously successful and far-reaching in their science impact. This legacy dataset would enable frontier science programs in several areas, including (1) studies of the CGM and IGM at unparalleled sensitivity, covering a wide range of UV metal lines and reaching very low H I column densities of log N=12.6 and low metallicities near [Z/H]=-2, enabling precision studies of the chemical abundances, ionization, temperature, and baryon and metal budgets of the CGM and IGM; (2) diffuse gas in the Milky Way and Local Group, including high-velocity clouds and gas streams from satellite mergers; (3) AGN outflows, which would be probed in the rest-frame extreme ultraviolet (EUV), covering continuum-generation mechanisms and diagnostics of gas in accretion-disk outflows.
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All authors Andrew J. Fox, Jerry Kriss, Philipp Richter, J. Michael Shull, Frances Cashman, Sapna Mishra, Annelia Anderson, Nahum Arav, Ramona Augustin, Kathleen Barger, Michelle Berg, Rongmon Bordoloi, Sanchayeeta Borthakur, Joseph Burchett, Jane Charlton, Hsiao-Wen Chen, Christopher Churchill, Ryan Cooke, Annalisa de Cia, Gisella de Rosa, Romeel Davé, Yakov Faerman, Travis Fischer, David French, Farhan Hasan, Svea Hernandez, Cameron Hummels, Sean Johnson, Glenn Kacprzak, Vikram Khaire, Doyeon Avery Kim, Brad Koplitz, Varsha Kulkarni, Nicolas Lehner, Matilde Mingozzi, Talawanda Monroe, Sowgat Muzahid, Benjamin Oppenheimer, Molly Peeples, Céline Péroux, Patrick Petitjean, Andreea Petric, Max Pettini, Zhijie Qu, Kate Rowlands, Ravi Sankrit, Debopam Som, Raghunathan Srianand, Nicolas Tejos, Jason Tumlinson, Bart Wakker, Jessica Werk

Earth and Planetary Astrophysics

Spin-Orbit Geometry of AU Mic b and c from Back-to-Back Transits Observed Contemporaneously with Magellan PFS, LCOGT, and CHEOPS

Zitao Lin, Gyula M. Szabó, Krzysztof Sz. Zieliński et al. (+37 more)

Young planets offer a unique window into the early stages of planetary evolution. AU Mic is one of the nearest (9.8 pc) pre-main sequence stars (~20 Myr), hosting two transiting Neptune-sized planets and a debris disk. Previous studies have shown that the rotation of the central star, the debris disk, and the inner planet b are all aligned, suggesting that the system has not undergone violent evolution. Here we report new Rossiter-McLaughlin (RM) measurements for both AU Mic b and c, which happened to transit back-to-back on Aug 24 and 25, 2024, using the Magellan Planet Finder Spectrograph (PFS), accompanioned with contanporaneous photometry from LCOGT and CHEOPS. We confirm the aligned orbit of AU Mic b ($\lambda_b=1{\deg} \pm 12{\deg}$) and finding two possible solutions for AU Mic c: we slightly favor an aligned solution ($\lambda_c=-10{\deg} \pm 16{\deg}$) but cannot rule out a polar solution ($\lambda_c=87{\deg}\ ^{+36{\deg}}_{-29{\deg}}$). Broader considerations, including dynamical stability and transit possibility, also support the mutually aligned scenario. An unexpected stellar signal during ingress and the poor TTV predictions of AU Mic c prevent a precise constraint on its obliquity, and various attempts using chromatic spectral analyses fail to outperform simple data exclusion in mitigating the stellar contamination. Our observation highlights the importance of understanding stellar activity across multiple timescales and channels when characterizing young, active systems. A robust solution for the AU Mic architecture will require either a better understanding of stellar activity or future observations fortuitously free from strong stellar contamination.
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All authors Zitao Lin, Gyula M. Szabó, Krzysztof Sz. Zieliński, Zhen Guo, Zoltán Garai, R. Paul Butler, Alexis Brandeker, Johanna K. Teske, Davide Gandolfi, Haochuan Yu, Nicolas Billot, Suzanne Aigrain, Michael Cretignier, Liang Wang, Xuan Mao, Wei M. Yuan, Hongpeng Lu, Jiayin Li, Yann Alibert, Ádám Boldog, Vincent Bourrier, Giovanni Bruno, Jeffrey D. Crane, Fei Dai, Olivier D. S. Demangeon, Alexis Heitzmann, Zhecheng Hu, Pradip Karmakar, Levente Kriskovics, Monika Lendl, He Y. Liu, Pierre F. L. Maxted, Hugh P. Osborn, Gaetano Scandariato, Stephen A. Shectman, Sérgio G. Sousa, Solène Ulmer-Moll, Mu-Tian Wang, Thomas G. Wilson, Sharon X. Wang

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Black Hole Photon Rings Saturate the Quantum Chaos Bound

D. Giataganas, G.F. Giudice, A. Kehagias et al. (+2 more)

We study the quantum chaos bound in the photon ring region surrounding black holes. By evaluating the Lyapunov exponent associated with unstable null geodesics in a broad class of generalized Kerr geometries, as well as the temperature induced by a string probe, we show that the quantum chaos bound is exactly saturated on equatorial circular orbits of the photon ring. We confirm our result by deriving the same exponent from out-of-time-order correlators in the near ring region. As a byproduct, we show that the photon ring saturation of the quantum chaos bound implies the saturation of the Bekenstein bound on the rate of information emission from the ringdown phase through the quasi-normal modes in the eikonal limit. Our results extend the known correspondence between black hole thermodynamics and chaotic dynamics, highlighting the role of the photon ring as a probe of the fundamental limits on thermalization and information scrambling in black holes.
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All authors D. Giataganas, G.F. Giudice, A. Kehagias, F. Quevedo, A. Riotto

Earth and Planetary Astrophysics

Modeling carbon outgassing from chondritic planetesimals

Bo Peng and Diana Valencia

The thermochemical evolution of planetesimals is an underprobed stage of volatile delivery to terrestrial planets during their formation, and may contribute to the volatile depletion of the Earth relative to primitive chondrites. We have developed a model of C outgassing from porous, chondritic planetesimals. Our model tracks the thermal evolution and the production of CO/CO2 gas using the redox states of ordinary and enstatite chondrites (OC and EC, respectively, collectively the "NCs"), and CI and CV carbonaceous chondrites ("CCs"). We posit the formation of global fractures when local gas pressure exceeds confinement levels, which vent the excess directly to space, leading to efficient C depletion. We also account for sintering and the enthalpy of dehydration from wet carbonaceous chondrite bodies. We find that C depletion is more efficient on CC planetesimals than NCs due to the former's oxidized environment: for 10-100 km planetesimals formed at 2 Myr after CAI formation, > 50% of C is depleted in almost all CC bodies while < 50% is depleted in almost all NC bodies. Both the largest and the smallest bodies tend to preserve more C, the former due to sintering locking condensed C in against escape, while the latter due to efficient conductive cooling. Earlier accreted planetesimals deplete more C: bodies formed before ~ My deplete most of their C. Our results favor NC planetesimals as the C carriers during terrestrial planets' accretion. Terrestrial planets likely accreted from a mix of C-depleted and C-rich bodies from both CC and NC reservoirs.
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High Energy Astrophysical Phenomena

Gamma-ray signature of superluminous supernovae: Fermi-LAT GeV detection of SN 2017egm and evidence of a central engine

F. Acero, A. Acharyya, A. Adelfio et al. (+116 more)

Superluminous supernovae (SLSNe) are a rare class of transients with peak luminosities 10-100 times greater than those of standard core-collapse supernovae (SNe). The mechanisms powering their extreme brightness remain debated, with circumstellar medium (CSM) interaction, or energy injection from a central engine like a magnetar wind nebula being the most plausible scenarios. To further constrain the underlying mechanism, we carried out a systematic search for GeV gamma-ray emission using the Fermi-LAT telescope from a sample of nearby hydrogen-poor (Type I) and hydrogen-rich (Type II) SLSNe over the past 16 years. Among the sample, only SN 2017egm shows significant gamma-ray emission, with likelihood test statistic (TS) values of 26-33 (i.e., >5$\sigma$) depending on the adopted time window. The signal arises between 50 and 160 days after explosion and is well described by a power-law spectrum with index $\Gamma=2.17 \pm 0.23$. The emission is consistent both in terms of its light curve and its spectrum, with predictions from magnetar models requiring either low nebular magnetization or faster spin-down than dipole losses. The CSM shell interaction scenario can reproduce the observed flux level but not the observed timing of the gamma-ray signal. In addition, the observed ratio, $L_{\gamma}/L_{opt} \sim 1$, is inconsistent with theoretical expectations and not in line with ratio measurements in other interacting CSM-dominated objects (e.g., novae or SNe) where this ratio is less than $10^{-2}$. Our study strongly suggests that a central engine like a magnetar plays a key role in this SLSN and could explain the bulk of the optical and gamma-ray light curves properties. Finally, simulations of 50 hours of CTAO observations indicate that a SN 2017egm-like event would be detectable up to 140 Mpc in the magnetar model but not in the CSM model due to strong gamma-gamma absorption.
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All authors F. Acero, A. Acharyya, A. Adelfio, M. Ajello, E. Aviano, L. Baldini, J. Ballet, C. Bartolini, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, E. Bissaldi, R. Bonino, P. Bruel, S. Buson, R. A. Cameron, P. A. Caraveo, F. Casaburo, F. Casini, E. Cavazzuti, C. C. Cheung, N. Cibrario, G. Cozzolongo, P. Cristarella Orestano, F. Cuna, S. Cutini, F. D'Ammando, D. Depalo, S. W. Digel, N. Di Lalla, A. Dinesh, L. Di Venere, P. Fauverge, A. Fiori, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, C. Gasbarra, D. Gasparrini, S. Germani, F. Giacchino, N. Giglietto, M. Giliberti, F. Giordano, M. Giroletti, I. A. Grenier, M.-H. Grondin, S. Guiriec, R. Gupta, E. Hays, J. W. Hewitt, A. Holzmann Airasca, D. Horan, X. Hou, T. Kayanoki, M. Kerr, M. Kuss, A. Laviron, M. Lemoine-Goumard, A. Liguori, J. Li, I. Liodakis, P. Loizzo, F. Longo, F. Loparco, S. López Pérez, L. Lorusso, M. N. Lovellette, P. Lubrano, S. Maldera, A. Manfreda, G. Martí-Devesa, R. Martinelli, M. N. Mazziotta, M. Michailidis, P. F. Michelson, N. Mirabal, T. Mizuno, P. Monti-Guarnieri, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, N. Omodei, M. Orienti, E. Orlando, G. Panzarini, M. Persic, M. Pesce-Rollins, R. Pillera, T. A. Porter, G. Principe, S. Rainò, R. Rando, B. Rani, M. Razzano, A. Reimer, O. Reimer, M. Sánchez-Conde, P. M. Saz Parkinson, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, D. J. Suson, H. Tajima, D. J. Thompson, D. F. Torres, Z. Wadiasingh, K. Wood, G. Zaharijas, W. Zhang, E. Chatzopoulos, B. D. Metzger, P. J. Pessi, I. Vurm

Solar and Stellar Astrophysics

Evidence of triggered star formation in the Pillars of Creation from JWST observations

Jing Wen, Bingqiu Chen, Jian Gao et al. (+3 more)

Stars form in molecular clouds under the influence of their local environments, yet the role of massive stellar feedback in either triggering or suppressing star formation remains a fundamental question in astrophysics. The Pillars of Creation in the Eagle Nebula, sculpted by ionizing radiation and stellar winds from massive stars in NGC 6611, offer a natural laboratory for investigating this question. Here we present high-resolution observations of the Pillars of Creation using the JWST Near Infrared Camera and Mid-Infrared Instrument, revealing 253 young stellar object (YSO) candidates. These YSO candidates show spatial correlations with the edges of feedback-driven structures, with overdensities along the boundaries. A weak trend of decreasing stellar age with increasing distance from the ionizing source was tentatively observed. There also appears to be an enhancement in the star formation rate within the past 1 Myr in this region. Such age and spatial associations suggest that while the bulk of the YSOs may have formed contemporaneously with the central cluster, a subset could be associated with triggered star formation. The JWST image of intricate structures, including a spiral-like disk and bi-reflection nebulae at the tips of Pillar I and Pillar II, further highlights the complexity of star formation processes.
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All authors Jing Wen, Bingqiu Chen, Jian Gao, Jun Li, Ming Yang, Biwei Jiang

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Problems of cosmology on small scales of the Universe

I.D. Karachentsev

Six challenges for the standard cosmological model $\Lambda$CDM are listed, which arise when comparing theoretical predictions with observational data on scales of ~1 Mpc. Different parameters of luminous and dwarf galaxies in the local sphere with a radius of 12 Mpc are presented. The average densities of stellar matter and dark matter are reproduced depending on a distance in the Local volume. Observational data on distribution of angular momentum of nearby galaxies are considered. A comparison of the dark matter mass estimates for systems of galaxies based on motions of their internal (virialized) members and neighboring galaxies is given. The reasons for the low derived value of the dark matter density, $\Omega_m = 0.08\pm0.02$, in the Local Universe with respect to the global value $\Omega_m = 0.30\pm0.02$ are discussed
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High Energy Astrophysical Phenomena

Transient Signatures of Star-Envelope Collisions in Little Red Dots

Tomoya Suzuguchi and Kohei Inayoshi

Little red dots (LRDs) are compact high-redshift objects, newly discovered by the James Webb Space Telescope. Although LRDs exhibit broad Balmer emission lines suggestive of the presence of active galactic nuclei (AGN), their spectral features differ significantly from those of ordinary AGN. Recent studies suggest that their characteristics can be explained if accreting supermassive black holes (SMBHs) are embedded within dense gaseous envelopes and surrounded by compact stellar clusters. In this scenario, stars in the cluster can scatter onto plunging orbits that intersect the envelope and collide with its surface. Here we investigate the observational properties of such star-envelope collisions as luminous transient events. We find that collisions involving red supergiants with radii of $\sim 10^{3}~R_\odot$, together with gaseous envelopes whose masses are comparable to those of the central SMBHs, are the most promising targets due to their high luminosities and long durations. For compact clusters with sizes of $\lesssim 10~{\rm pc}$, such massive stars can participate in star-envelope collisions within their lifetimes at event rates reaching $\sim 0.3~{\rm yr}^{-1}$ per LRD. We show that these transients are detectable with future wide-field surveys such as the Nancy Grace Roman Space Telescope if they occur at relatively low redshifts ($z \lesssim 1$). Detection of such transients would provide strong evidence for the envelope+stellar-cluster scenario of LRDs and offer a unique probe of the envelope mass, which is otherwise difficult to constrain from LRD spectra alone.
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Cosmology and Nongalactic Astrophysics

Exploring the High-Redshift 21-cm Signal via Self-Consistent Simulations using Artificial Neural Network Emulation

Colton R. Feathers, Eli Visbal, Steven Murray et al. (+2 more)

We present a novel, self-consistent, semi-numeric Cosmic Dawn (CD) simulation in which small-scale star formation (SF) is calibrated to the AEOS and Renaissance hydrodynamic simulations. SF proceeds within dark matter (DM) halos via neural network emulation while considering large-scale fluctuations in density and feedback. We translate the resulting 3D distribution of galaxies into predictions for the 21-cm brightness temperature, \Tb, and power spectrum, \PS. We simulate several unique realizations to study the impact of varying astrophysics on \Tb, finding that more efficient Population II (PopII) SF largely yields stronger Lyman-$\alpha$ coupling, resulting in a shallower and wider absorption trough. However, we find that PopII SF dominates \PS\ at $z \lesssim 20$ and on smaller scales at intermediate redshifts ($k \gtrsim 0.2\ \mathrm{Mpc^{-1}}$ at $z \simeq 34-20$) while Population III (PopIII) SF dominates \PS\ at $z\gtrsim34$ and on larger scales at intermediate redshifts. Compared with previous works, we find that the combination of hydrodynamic SF calibration, a critical halo mass for SF considering \Htwo\ self-shielding, and stochastic DM halo merger histories results in both earlier SF and higher SF rates across CD. Further, we find that the delay period separating PopIII and PopII SF (\tdelay) significantly impacts \Tb, and that one must include DM halo merger histories to properly account for this transition. Finally, we find our fiducial \Tb\ to be detectable at $z\lesssim25$ with 1080 hours of HERA observations under moderate foreground assumptions, and the lack of such a detection at $z \gtrsim 20$ would suggest \tdelay\ $\gtrsim$ 30 Myr.
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All authors Colton R. Feathers, Eli Visbal, Steven Murray, Ryan Hazlett, Yin-Zhe Ma

Earth and Planetary Astrophysics

The asymmetric carbon-rich chemistry of the planet-forming disk of HD 142527 triggered by late infall

Milou Temmink, Ewine F. van Dishoeck, Alice S. Booth et al. (+3 more)

The planet-forming disk of HD 142527 is known for its azimuthally asymmetric dust trap, shadows, and spiral arms. We use new ALMA observations to investigate the molecular composition and to determine the ongoing chemical processes and the origin of its asymmetric molecular emission. The observations cover a wide variety of molecular species, enlarging the known molecular inventory of this system. Strikingly, the emission of H$_2$CO, CN, and C$_2$H is dominated by spiral-like features peaking in the southern region of the disk, opposite to the large dust trap, while no relation is found between the observed asymmetries and the shadows seen in the scattered light. We attribute these features to low-density, late infalling, atomic carbon-rich material that locally enhances the C/O-ratio and, subsequently, facilitates the gas-phase formation of these species. The emission of C$^{17}$O and the HCO$^+$ $J$=1-0 transition is aligned with the large dust trap, likely due to an azimuthal enhancement in the surface density. Differences between the two observed C$^{17}$O transitions may be due to dust obscuration effects. This is not expected to affect molecular emission at 3 millimetres, given the lower optical depth of the dust trap. The four observed transitions of CS display different azimuthal extents and strengths, with the lines with lower upper level energies appearing more ring-like. An analysis of the $^{13}$CO brightness temperature yields no significant azimuthal temperature variations. Therefore, we propose that the observed CS transitions trace two different reservoirs: a cold reservoir that resides on a Keplerian orbit and a second, hotter reservoir of CS that is facilitated by the infalling material. A single weak transition of SO is observed, which may be explained by weak shocks induced by the spirals observed in the scattered light that liberate sulphur.
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All authors Milou Temmink, Ewine F. van Dishoeck, Alice S. Booth, Nienke van der Marel, Myriam Benisty, Michiel R. Hogerheijde

Earth and Planetary Astrophysics

A Calibrated Bayesian Search for Potential Chemical Technosignatures in Polluted White Dwarf

Bo-Lun Huang, Zhen-Zhao Tao and Tong-Jie Zhang

We present a meteorite-calibrated Bayesian framework for searching archival abundance records for chemical technosignatures–operationally, compositional patterns better explained by an idealised "processed" template (endmember) than by the empirical distribution of natural rocks. We fit a multi-modal natural-composition reference using 3,493 whole-rock meteorite analyses, and for each of 697 star-paper abundance sets–spanning at least 397 distinct objects once Gaia-designated repeats are consolidated–we compare the Bayesian evidence for (i) natural material and (ii) a mixture of natural material with a fixed siderophile-enriched template, parameterised by a Ca-normalized mixing fraction alpha. Strong support for the processed template is uncommon: in the photospheric compilation (atm) 8/697 records have BF > 10 (4/697 have BF > 100), and in the diffusion-adjusted steady-state subset (acc ss; 148 records spanning at least 94 objects) 6/148 have BF > 10. We report the highest-evidence candidate records and infer the fraction of records detectably favoring the mixture model, with posterior medians pi-tilde = 0.011 (atm) and pi-tilde = 0.041 (acc ss). We calibrate the analysis with end-to-end injection-recovery experiments matched to each record's coverage and censoring. The calibration shows that discrimination is driven mainly by chemical information, typically requires greater-than-or-similar-to 5 detected elements for decisive support, and–for the siderophile template–is strongest for exact five-element panels that include Fe, Mg, Cr, and Ti together with Ni, Si, or Na. These results constrain the detectable incidence of the tested processed-composition class in current data and set observational requirements for future multi-element surveys and expanded template families.
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Cosmology and Nongalactic Astrophysics

The observer power spectrum for lightcone statistics, integrated relativistic observables and wide angle effects

Chris Clarkson and Pritha Paul

The statistics of large-scale structure are naturally described by power spectra in Fourier space. For fields on spatial hypersurfaces, translational invariance makes different Fourier modes uncorrelated and the power spectrum diagonal. Cosmological observables, however, are measured on our past lightcone, where wide-angle effects, radial evolution and integrated effects such as lensing break this symmetry: Fourier-space statistics become non-diagonal, with mode-mixing generated by the geometry of the lightcone itself. We define a more natural observer power spectrum by Fourier transforming over observer positions on a spatial hypersurface with fixed lightcone coordinates, rather than over source positions on a single lightcone. This forms a field on the observer hypersurface with a moveable light-ray leg. Statistical homogeneity of the observer hypersurface implies that this spectrum is diagonal for any observable, whether local or integrated and does not suffer from mode-mixing. We show how the various two-point statistics used in large-scale structure analysis are each recovered as projections of the observer spectrum. This extends directly to higher-order statistics. We illustrate it by constructing the relativistic kernel for the observed galaxy number count fluctuation, including density, redshift-space distortions, Doppler, lensing magnification, and integrated Sachs-Wolfe contributions.
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Cosmology and Nongalactic Astrophysics

Model Independent Probe of Variation of Cosmic Opacity with Redshift

Savita Gahlaut and Meetu Luthra

Cosmic opacity may vary spatially due to the inhomogeneous distribution of dust, its grain properties, and the efficiency of photon attenuation. In this work, we present a model independent method to investigate the variation of cosmic opacity with redshift. Using strong gravitational lensing data we construct the opacity independent comoving distance function and we use latest supernovae type Ia (SNe Ia) Pantheon+ data to estimate the opacity dependent comoving distances. Using the distance duality equation, opacity parameter is constrained. Our analysis indicates a transparent Universe on average over the redshift range ($0.01 \leq z \leq 2.26137$) of Pantheon+ sample. However, if we split the dataset into subsamples with redshift bins of width $\bigtriangleup z = 0.1$, we find appreciable deviation from the transparency in several redshift intervals. Particularly, in the redshift range $0.3 < z \leq 0.4$, the opacity parameter is $\epsilon = -0.4283^{+0.1914}_{-0.2027}$. The current SNe Ia observations indicate the variation of opacity parameter with redshift. These results may have a significant impact on the values of the cosmological parameters deduced from the SNe Ia observations.
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Solar and Stellar Astrophysics

Stellar Population Astrophysics (SPA) with the TNG. CNO abundances in 28 open clusters

Bruno Ćurjurić, Arnas Drazdauskas, Gražina Tautvaišienė et al. (+4 more)

Aims. Our main aim with this work was to enlarge the pool of open clusters with determined carbon, nitrogen, and oxygen abundances in evolved giants to further advance chemical clocks in stellar age determinations. Methods. High-resolution spectra were analysed using a differential model atmosphere method. Carbon abundances were derived using spectral synthesis of the C2 band heads at 5135 and 5635.5 Å. The CN features at 6470-6490 Å were analysed to determine the abundances of nitrogen. The oxygen abundances were determined from the [O I] line at 6300 Å. Results. We provide abundances of C, N, and O for 88 giants in 28 open clusters and in two stars of the association Theia 1214. The results were compared with theoretical predictions and used for the analysis of the [C/N] relations with age, and we investigated the origin of the two Theia 1214 stars. Conclusions. Precise age dating requires separate age calibrations of [C/N] ratios for the first-ascent giants of the lower part of the red giant branch and for the red clump stars to account for the additional abundance alterations during the post-red giant branch luminosity bump evolution. In the first-ascent giant stars with larger turn-off masses, the observed C/N ratios are slightly higher than those predicted by standard models, and the obtained [C/N] versus age relation is flatter in the young age regime than in previous studies. We doubt that the two stars we investigated in the Theia 1214 association belong to the tail of NGC 752. Most probably, they are field stars.
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All authors Bruno Ćurjurić, Arnas Drazdauskas, Gražina Tautvaišienė, Angela Bragaglia, Natalia Alvarez-Baena, Valentina D'Orazi, Marina Dal Ponte

High Energy Astrophysical Phenomena

Enhanced All-Distance Equi-Zenith Angle Method for Cosmic-Ray Anisotropy Measurement

Dong-Xu Sun, Dan Li, Wei Liu et al. (+3 more)

Long-term observations indicate that the relative intensity of cosmic-ray anisotropy remains below $0.1\%$ for energies less than $\sim 1$ PeV. Measuring such faint signals poses a significant challenge in data analysis, requiring careful removal of instrumental and atmospheric artifacts. The all-distance equi-zenith angle method is widely employed to extract cosmic-ray anisotropies, as it effectively suppresses the instantaneous variations arising from the instrument and atmosphere. \textcolor{black}{However, instability in the detector efficiency makes precise measurements of anisotropy challenging with this method.} In this work, we present an enhanced all-distance equi-zenith angle method for cosmic-ray anisotropy measurement. Unlike previous implementations, our improved approach enables the simultaneous measurement of anisotropies over multiple time frames and allows the detection efficiency to be determined directly from the data. This feature makes the method especially suitable for applications where the detector array does not operate with long-term stability\textcolor{black}{, and thus allows for the measurement of anisotropy with high-precision}. Moreover, our enhanced method is also feasible when the data do not span complete tropical years.
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All authors Dong-Xu Sun, Dan Li, Wei Liu, Qiang Yuan, Yi-Qing Guo, Hong-bo Hu

Astrophysics of Galaxies

MAMMOTH-Grism: Gas-phase Metallicity Gradients of Star-forming Galaxies in Protocluster Environments at Cosmic Noon

Yi-Ming Yang, Xin Wang, Chao-Wei Tsai et al. (+11 more)

Environment plays a crucial role in shaping galaxy formation, yet the impact of overdensities on the internal chemical structure of galaxies at cosmic noon is still under debate. Here, we present spatially resolved gas-phase metallicity gradients for 42 star-forming galaxies in three massive protoclusters at $z \sim 2.3$, derived fromHubble Space Telescope (HST) slitless grism spectroscopy from the MAMMOTH-Grism survey. We find that the majority (29 of 42, $\sim$69%) of these protocluster members exhibit positive (inverted) metallicity gradients, a fraction significantly higher than observed in field galaxies of similar mass and redshift. By examining correlations with global properties, we show that these positive gradients are strongly associated with galaxies that are metal-deficient relative to the field mass-metallicity relation, particularly among the massive population ($\log(M_*/M_\odot) > 9.95$). These trends suggest that galaxies in dense protocluster environments experience substantial, enhanced inflows of pristine gas toward their central regions, which dilute the central metallicity and produce the observed inverted gradients. Our results provide observational evidence that environmental effects actively regulate gas accretion and chemical redistribution during the peak epoch of cosmic star formation.
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All authors Yi-Ming Yang, Xin Wang, Chao-Wei Tsai, Zihao Li, Zheng Cai, Anahita Alavi, Fuyan Bian, James Colbert, Xiaohui Fan, Alaina L. Henry, Matthew A. Malkan, Dong Dong Shi, Harry I. Teplitz, Xian Zhong Zheng

Astrophysics of Galaxies

A New Cartwheel-like Collisional Ring Galaxy

Vladimir P. Reshetnikov, Sergey S. Savchenko, Alexander A. Marchuk et al. (+5 more)

We report the discovery of a new Cartwheel-type collisional ring galaxy, PGC\,1112751, which we named “Eridanus Wheel” (EW). Such systems result from head-on collisions between galaxies and are of considerable interest as laboratories for studying star formation in propagating density waves and the response of the star-gas disk of galaxies to strong external perturbations. During a systematic visual inspection of fields from the DESI Legacy Imaging Surveys, we identified a galaxy at a redshift of $z=0.0856$ whose morphology closely resembles that of the famous Cartwheel Galaxy. EW exhibits a well-defined inner ring and a more diffuse outer ring, with so-called “spokes” visible in the region between them. The ring galaxy and its possible intruder are connected by a faint optical bridge. The projected distance between the centers of the galaxies is about 60 kpc. Using data from the DESI Legacy Surveys, we performed a photometric study of galaxies in the $griz$ filters. We conclude that the Eridanus Wheel is a giant late-type galaxy with a strong radial color gradient, whose observed morphology is most likely explained by a relatively recent head-on collision with an early-type galaxy. The further evolution of this object will most likely lead to the formation of a galaxy with a low surface brightness disk.
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All authors Vladimir P. Reshetnikov, Sergey S. Savchenko, Alexander A. Marchuk, Ilia V. Chugunov, Matvey D. Kozlov, Dmitry I. Makarov, Aleksandra V. Antipova, Anastasia M. Sypkova

Astrophysics of Galaxies

An Obscured Tidal Disruption Event Uncovered by Its Mid- and Near-Infrared Dust Echo in a Star-Forming Galaxy

Hui Liu, Luming Sun, Ning Jiang et al. (+8 more)

We present a comprehensive study of an infrared (IR) flare in the star-forming galaxy SDSS J010320.39+140152.5, which is selected from the sample of mid-IR (MIR) outbursts in nearby galaxies (MIRONG). Its MIR luminosity rose rapidly to a peak of $\sim5.4\times10^{43}$ \lum, maintained in the high state for about a year, and decreased continuously afterward. No optical variability was detected throughout the IR flare. Near-IR follow-up observations around the peak pinpointed the flare's location to spatially coincide with the galactic nucleus, with a $3\sigma$ upper limit of the offset of $\lesssim100$ pc. The IR spectral energy distribution (SED) of the flare is consistent with thermal emission of dust with temperatures of $\sim900$ K. Using a dust radiative transfer model, we inferred a peak UV luminosity of $\sim(4-10)\times10^{44}$ erg s$^{-1}$ and a total energy of $\sim(0.9-2)\times10^{52}$ ergs released. We ruled out the possibility of a supernova, and prefer that the IR flare originated from an obscured tidal disruption event (TDE) rather than a changing-look active galactic nucleus (AGN). This flare stands as one of the most compelling cases to date for the emerging class of dust-obscured TDEs in recent years. They are missed by optical surveys, partly accounting for the observed bias in TDE host galaxies, and represent a crucial, yet often overlooked, component for a complete understanding of the TDE population.
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All authors Hui Liu, Luming Sun, Ning Jiang, Xinwen Shu, Yibo Wang, Tinggui Wang, Roc M. Cutri, Liming Dou, Fabao Zhang, Jiazheng Zhu, Zhenfeng Sheng

Solar and Stellar Astrophysics

Sub-surface structural changes associated with successive 11-yr solar activity cycles have been progressively more confined near the surface: new helioseismic results on Cycles 22 – 25 from BiSON

William J. Chaplin, Sarbani Basu, Rachel Howe et al. (+3 more)

We use Sun-as-a-star helioseismology data, collected by the Birmingham Solar-Oscillations Network (BiSON), to examine the relationship between the solar-cycle-induced frequency shifts of whole-Sun, low-angular degree solar p modes and well-known proxies of global solar activity. Changes in behaviour between the low-frequency modes and proxies, which in a previous study we found had occurred on the declining phase of Cycle 23, appear to have persisted into Cycle 25. More striking is a significant change in the relationship for higher-frequency modes, which the new Cycle 25 data now reveal. The observed mean frequency shifts in Cycle 25 are much stronger than one would expect for these modes based on the relationship between the frequencies and proxies seen in previous cycles, in particular Cycle 22. In sum, Cycle 25 is as strong as Cycles 22 and 23 when observed in this higher-frequency seismic band, in marked contrast to the relative sizes of the cycles seen in the global activity proxies, where Cycle 25 is noticeably weaker. When considered alongside a systematic reduction of the sensitivity of the mid-frequency modes to activity over the past three cycles, these results suggest that sub-surface structural changes associated with successive 11-year cycles are becoming ever more progressively confined just beneath the solar surface.
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All authors William J. Chaplin, Sarbani Basu, Rachel Howe, Yvonne Elsworth, Steven J. Hale, Eleanor Murray

Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

Quantum transitions of vector vortex light in gravitational waves

Haorong Wu and Xilong Fan

We develop a theoretical framework to describe the full interaction between vector vortex light fields and gravitational waves (GWs). Using perturbation theory and the canonical quantization of the electromagnetic field, we calculate the quantum transition probabilities of vector Bessel beams propagating through GWs. We demonstrate that GWs induce fourteen different quantum transition channels across orbital angular momentum (OAM) $l$ and spin angular momentum (SAM) $\sigma$, mapping initial states $\ket{\sigma,l}$ to $\ket{\sigma+\Delta \sigma,l+j-\Delta \sigma}$, where $\Delta\sigma \in \{-2, 0, 2\}$ represents the change in SAM and $j \in \{-3, \dots, 3\}$ denotes the change in total angular momentum. Among these channels, SAM-conserving transitions between OAM states, specifically $\ket{\sigma, l}\rightarrow \ket{\sigma, l\pm 1}$, provide the most viable mechanism for experimental detection. Conversely, spin-flip transitions are shown to be heavily suppressed relative to OAM transitions. Additionally, the reversal of SAM induces an asymmetric shift in the OAM transition channels, reflecting the underlying coupling between SAM and OAM during the gravitational interaction. Based on these transition channels, we propose a new cavity-based GW detection configuration. By relying on quantum transitions rather than macroscopic arm-length changes, this scheme is inherently insensitive to displacement-based disturbances like seismic noise, offering a new paradigm and frequency bands for GW observation.
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High Energy Astrophysical Phenomena

Time-Domain Deep Learning for Pairwise Identification of Strongly Lensed Gravitational-Wave Candidates

Fan Zhang, Qikai Zhang, Qiyuan Yang et al. (+3 more)

As gravitational wave (GW) catalogs continue to expand, exhaustive Bayesian comparisons of candidate event pairs become increasingly computationally expensive, which motivates the development of fast prescreening methods for strongly lensed GW searches. We formulate lensed-pair identification as a binary verification problem using two preprocessed strain segments. To address this task, we propose Physics-Inspired ResNet (PI-ResNet), a Siamese one-dimensional residual network for pairwise GW candidate classification. Unlike spectrogram-based prescreening approaches, PI-ResNet operates directly on whitened time-domain strain data and avoids an intermediate time–frequency image representation. A shared residual backbone with Squeeze-and-Excitation (SE) modules encodes the two input segments, and the paired embeddings are compared through absolute feature differences and Hadamard-product interactions. We train and evaluate the model using simulated GW signals from binary black hole mergers lensed by point-mass (PM) and singular isothermal sphere (SIS) lenses, injected into simulated LIGO and Einstein Telescope (ET) detector noise. Under ET design noise, PI-ResNet achieves accuracies of $95.60\%$ for SIS lenses and $93.80\%$ for PM lenses, while maintaining $84.03\%$ and $78.25\%$ accuracy under simulated LIGO H1–L1 Gaussian noise. These results suggest that direct learning from 1D strain data provides an efficient and physically motivated preselection statistic for candidate lensed GW pairs, while also indicating the need for detector-domain adaptation.
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All authors Fan Zhang, Qikai Zhang, Qiyuan Yang, Jiaqing Huang, Yong Yuan, Xilong Fan

Solar and Stellar Astrophysics

Multiple populations detection with the Chinese Space Station Survey Telescope main survey camera

Zhuohang Li, Xia Li, Hao Tian et al. (+6 more)

Multiple stellar populations (MPs), characterized by star-to-star light-element abundance variations, are ubiquitous in globular clusters (GCs). Spectroscopy directly reveals these anomalies, while photometric studies, especially with the Hubble Space Telescope (HST), have been essential for tracing MP sequences in colour-magnitude diagrams (CMDs). However, the limited field of view of HST confines most studies to cluster centres. The upcoming Chinese Space Station Survey Telescope (CSST), with its wide field of view and UV-optical coverage, will enable systematic MP studies over entire clusters. We assess the capability of the CSST wide-field camera to detect and characterize MPs in GCs using realistic simulations. Synthetic stellar population models with different helium abundances ($\Delta Y$) and CNO variations were used to simulate CSST observations of GCs at distances of 9.6 and 20~kpc under different exposure times. MP detectability was evaluated using CMDs in seven CSST bands and UV-optical pseudo-colour diagrams. For a GC at 9.6~kpc, the $NUV-u$ colour is highly sensitive to $\Delta Y$ and CNO variations, with separations of $\Delta(NUV-u)\approx0.16$ mag for red giants and up to 0.44 mag for dwarfs. MPs can be resolved when the total UV exposure exceeds $\sim1000$~s and the optical exposure exceeds $\sim300$~s. At 20~kpc, encompassing $\sim80\%$ of Galactic GCs, CSST still retains strong diagnostic power, resolving populations with $\Delta Y\geq0.06$ and $\delta[\mathrm{N/Fe}]\geq0.64$, and separating MPs down to $i\sim19.5$ mag in clusters with large chemical spreads. The $NUV$-$u$-$g$ combination provides diagnostic performance comparable to the HST F275W–F336W–F438W system. CSST will enable homogeneous MP surveys across the full spatial extent of star clusters in the Milky Way and nearby galaxies.
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All authors Zhuohang Li, Xia Li, Hao Tian, Xin Zhang, Antonino P. Milone, Long Wang, Baitian Tang, Edoardo P. Lagioia, Chengyuan Li