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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 18 February

Earth and Planetary Astrophysics

Two warm sub-Saturn mass planets identified from the TESS Full Frame Images

Felipe I. Rojas, Rafael Brahm, Andrés Jordán et al. (+47 more)

Context. Characterization of warm giants is crucial to constrain giant planet formation and evolution. Measuring the mass and radius of these planets, combined with their moderated irradiation, allows us to estimate their planetary bulk composition, which is a key quantity to comprehend giant planet formation and structure. Aims. We present the discovery of two transiting warm giant planets orbiting solar-type stars from the Transiting Exoplanet Survey Satellite (TESS), which were characterized by further spectroscopic and photometric ground-based observations. Methods. We performed a joint analysis of photometric data with radial velocities to confirm and characterize TOI-883 b and TOI-899 b, two sub-Saturns orbiting solar-like stars. Results. TOI-883 b and TOI-899 b have masses of $0.123 \pm 0.012$ $M_J$ and $0.213 \pm 0.024$ $M_J$, radius of $0.604 \pm 0.028$ $R_J$ and $0.991 \pm 0.044$ $R_J$, periods of $10.06$ d and $12.85$ d and equilibrium temperature of $1086 \pm 19$ K and $1040 \pm 19$ K, respectively. Conclusions. While having similar masses, orbital periods and stellar host properties, these planets seem to have different internal compositions, which could point to distinct formation histories. Both planets are suitable targets for atmospheric studies to further constrain formation scenarios of planets in the Neptune-Saturn mass range
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All authors Felipe I. Rojas, Rafael Brahm, Andrés Jordán, Néstor Espinoza, Thomas Henning, Jan Eberhardt, Melissa J. Hobson, Martin Schlecker, Marcelo Tala Pinto, Trifon Trifonov, Lyu Abe, Gaspar Bakos, Mauro Barbieri, Khalid Barkaoui, Christopher J. Burke, R. Paul Butler, Ilaria Carleo, Karen A. Collins, Jeffrey D. Crane, Zoltan Csubry, Phil Evans, Tristan Guillot, Chelsea X. Huang, Jon M. Jenkins, Matias I. Jones, Diana Kossakowski, David W. Latham, Andrew W. Mann, Djamel Mékarnia, Maximiliano Moyano, Sangeetha Nandakumar, Hugh P. Osborn, George Ricker, David Rodriguez, Paula Sarkis, Richard P. Schwarz, Sara Seager, Ramotholo Sefako, Stephen Shectman, Gregor Srdoc, Stephanie Striegel, Vincent Suc, Johanna Teske, Ian Thompson, Pascal Torres-Miranda, Roland Vanderspek, José Vines, Sharon X. Wang, Joshua N. Winn, Carl Ziegler

Astrophysics of Galaxies

HOLISMOKES XX. Lens models of binary lens galaxies with five images of Supernova Winny

L. R. Ecker, A. G. Schweinfurth, R. Saglia et al. (+13 more)

Strongly lensed supernovae (SNe) provide a powerful way to study cosmology, SNe and galaxies. Modelling the lens system is key to extracting astrophysical and cosmological information. We present adaptive-optics-assisted high-resolution images of SN Winny (SN 2025wny) in the J and K filters obtained with the Large Binocular Telescope (LBT). The LBT imaging confirms the presence of a fifth point source, whose colour is consistent with that of the other SN images at similar phases, while lens modelling robustly supports its interpretation as an additional image of SN~Winny. We measure the positions of the five SN images with uncertainties varying between 1 and 14 milliarcseconds. We build the first mass models using lenstronomy and GLEE, and explore three classes of mass models for the two lens galaxies G1 and G2. The optimal model class of the three is a singular isothermal ellipsoid for G1, a singular isothermal sphere for G2, and an external shear. We infer the enclosed masses within the Einstein radius as 4.61^{+0.06}_{-0.04} \times 10^{11}\,M_\odot for G1 and 1.01\pm0.02 \times 10^{11}\,M_\odot for G2. The lensing configuration by the two lens galaxies can produce two additional magnified SN images beyond the five observed ones; the exclusion of such model configurations further constrains the lens model parameters. Our model fits to the observed image positions with an RMS of ~0.0012" - 0.0025", within the observed positional uncertainties. The predicted magnifications of the multiple images vary between ~1.6 (for the faintest fifth image E) to ~10 (for the brightest image A). The predicted relative lensing magnifications of the multiple images do not match that of the observed within 2\sigma uncertainties. The differences in the relative magnifications could be due to millilensing/microlensing. Our mass models form the basis for future analyses of this unique system. (abridged)
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All authors L. R. Ecker, A. G. Schweinfurth, R. Saglia, L. Deng, S. H. Suyu, C. Saulder, J. Snigula, R. Bender, R. Cañameras, T.-W. Chen, A. Galan, A. Halkola, E. Mamuzic, A. Melo, S. Schuldt, S. Taubenberger

Earth and Planetary Astrophysics

Meteor statistics I: The distribution of instrumental magnitudes

Althea V. Moorhead, Peter G. Brown, Margaret D. Campbell-Brown et al. (+2 more)

The distribution of meteor magnitudes is known to follow an exponential distribution, where the base of this distribution is called the population index. The distribution of observed magnitudes preserves this behavior, but is truncated by the detection threshold. If both the population index and detection threshold can be determined, observed meteor rates can be converted to fluxes and extrapolated to any desired brightness or size. We argue that the distribution of observed or instrumental meteor magnitudes is best modeled as an exponentially modified Gaussian (exGaussian) distribution. This is for three reasons: first, an exGaussian distribution is the natural result of random variations in detection threshold and/or post-detection measurement errors in magnitude. Second, an exGaussian distribution provides a better fit to the magnitude distribution than all other competing distributions in the literature; we demonstrate this using both a set of faint optical meteor magnitudes and a set of radar meteor echo amplitudes. Finally, the population index, mean detection threshold, and random variation/error terms are easily extracted from the best-fit parameters of an exGaussian distribution.
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All authors Althea V. Moorhead, Peter G. Brown, Margaret D. Campbell-Brown, Michael J. Mazur, Denis Vida

Cosmology and Nongalactic Astrophysics

Chiral gravitational waves from multi-phase magnetogenesis

H. V. Ragavendra, Gianmassimo Tasinato and L. Sriramkumar

Cosmological vector fields are central to many early-Universe phenomena, including inflationary dynamics, primordial magnetogenesis, and dark-matter scenarios. However, constructing models able to generate cosmological magnetic fields while avoiding strong coupling, backreaction, and cosmic microwave background constraints remains challenging. We study a novel mechanism in which brief non–slow-roll phases during inflation amplify primordial magnetic fields at small scales, while maintaining theoretical consistency and observational viability. We incorporate parity-violating interactions in the vector sector and demonstrate, for the first time in a non–slow-roll framework, that chirality can significantly boost magnetic-field amplitudes and imprint distinctive polarization-dependent spectral features. We complement detailed numerical computations with an analytical treatment yielding compact expressions for chiral vector mode functions that reproduce the main spectral properties. We then develop a systematic formalism to evaluate the stochastic gravitational-wave background naturally induced at second order by these amplified fields, identifying both an intensity component and a circularly polarized contribution with characteristic frequency profiles. We discuss detection prospects with future multiband gravitational-wave observatories, showing that chiral signatures could provide a distinctive observational probe. Our results introduce new avenues for enhancing primordial magnetic fields and their associated gravitational-wave signals, opening promising possibilities for their future detection and interpretation, both with cosmological and gravitational wave probes.
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High Energy Astrophysical Phenomena

GOTO identification and broadband modelling of the counterpart to the SVOM GRB 250818B

S. Belkin, G. P. Lamb, K. Ackley et al. (+61 more)

Rapid localisation and follow-up of gamma-ray bursts (GRBs) increasingly rely on low-latency triggers from new missions coupled to wide-field robotic optical facilities. We present the discovery and multi-wavelength follow-up of GRB 250818B, detected by the Space Variable Objects Monitor (SVOM) and localised optically by the Gravitational-wave Optical Transient Observer (GOTO). We compile and homogenise X-ray, optical/NIR, and radio data to build broadband light curves and spectral energy distributions. The afterglow is unusually luminous for a nominal short GRB, lying on the bright end of the short-GRB population in X-rays and optical and among the most luminous high-redshift short-GRB afterglows in the radio. MeerKAT detects the source at 3.1 GHz, while ALMA provides deep higher-frequency limits. Keck/LRIS spectroscopy shows continuum and metal absorption (Fe II, Mg II, Mg I), giving $z=1.216$. Synchrotron forward-shock modelling favours a constant-density medium and strongly prefers refreshed (energy-injection) emission, well described by a two-component jet with $E_{K,iso} \sim 4\times10^{52}$ erg, $n_0 \sim 3.6$ cm$^{-3}$, $\theta_j \simeq 0.10$ rad ($\sim 5.7$ deg), and $p \simeq 1.64$. The host association is ambiguous: the nearest LS DR10 galaxy candidate ($r_{AB} \sim 24.7$) is offset by $\sim 4$ arcsec ($\sim 34$ kpc) with chance-alignment probability $P_{cc} \sim 0.2$, and current imaging does not exclude a fainter, near-coincident host. SED fitting of the candidate host suggests a low-mass galaxy. GRB 250818B highlights the power of rapid wide-field counterpart identification in the SVOM era, while host-association uncertainty can still limit offset-based interpretation.
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All authors S. Belkin, G. P. Lamb, K. Ackley, M. E. Wortley, S. McGee, G. Schroeder, M. Shrestha, B. P. Gompertz, D. K. Galloway, R. Starling, W.-f. Fong, T. Laskar, C. Liu, A. C. Gordon, N. Pankov, A. E. Volvach, L. N. Volvach, A. Shein, A. Pozanenko, M. J. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, V. S. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, D. Pollacco, S. Awiphan, J. Casares, P. Chote, A. Chrimes, R. Eyles-Ferris, B. Godson, P. Irawati, D. Jarvis, Y. Julakanti, L. Kelsey, M. R. Kennedy, T. Killestein, A. Kumar, A. Levan, S. Littlefair, M. Magee, S. Mandhai, D. Mata S'anchez, S. Mattila, J. McCormac, D. Mkrtichian, S. Moran, J. Mullaney, D. O'Neill, M. Patel, K. Pu, M. Pursiainen, A. Sahu, U. Sawangwit, E. Stanway, Y. Sun, B. Warwick, K. Wiersema

Solar and Stellar Astrophysics

Searching for White Dwarf Candidates Formed Through Binary evolution in Star Clusters

Huahui Yan, Li Wang, David R. Miller et al. (+11 more)

White dwarfs (WDs), the evolutionary endpoints of most stars, can form through both single-star and binary channels. While single-star evolutionary models enable reliable WD age estimates, binary evolution introduces interactions that can accelerate WD formation and result in a variety of exotic WDs, which may exhibit strong magnetic fields, rapid rotation, or even serve as potential gravitational wave sources. Such systems offer valuable insights into magnetic field generation, angular momentum evolution, and compact object physics. Star clusters, with their approximately coeval populations, allow precise age determination of member WDs. If a WD's total age derived from single-star evolution exceeds that of its host cluster, it likely indicates a binary origin. In this study, we use Gaia 5D astrometry to identify 439 WD candidates in 117 open clusters, with 244 likely formed via binary evolution. We discuss the possibility of dynamical ejection for WDs meeting only 2D (proper motion space) membership criteria. Spectroscopic observations further reveal a subset with strong magnetic fields and rapid rotation, supporting their binary evolutionary origin.
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All authors Huahui Yan, Li Wang, David R. Miller, Chenyu He, Jiamao Lin, Xiaoying Pang, Jingkun Zhao, Jincheng Guo, Richard de Grijs, Hongwei Ge, Zhen Guo, Bo Ma, Dichang Chen, Chengyuan Li

Solar and Stellar Astrophysics

New self-consistent theoretical descriptions for mass-loss rates of O-type stars

F. Figueroa-Tapia, J. A. Panei, M. Curé et al. (+5 more)

Massive O-type stars lose a significant fraction of their mass through radiation-driven winds, a process that critically shapes their evolution and feedback into the interstellar medium. Accurate predictions of mass-loss rates are essential for models of stellar structure and population synthesis. We computed wind parameters for O-type stars using a self-consistent approach that couples the hydrodynamics of the wind with detailed calculations of the line acceleration. This approach follows the theory of radiation-driven stellar winds and allows us to derive mass-loss rate distributions for different atomic configurations of the stellar flux. We used the TLUSTY code for stellar atmosphere models to compute non-local thermodynamic equilibrium models; these models served as input radiation fields for the calculation of the line-force parameters, for which we used the LOCUS code. These line-force parameters were then iteratively coupled with the HYDWIND code to solve the wind hydrodynamics. The procedure was applied across a grid of stellar parameters for three chemical configurations. We obtain self-consistent wind parameters for a broad set of O-type stellar models. The results show a systematic decrease in mass-loss rates with the inclusion of more elements in the radiation field, which is attributed to a strong effect on the UV region of the spectral energy distribution. As more elements are included, resulting in a larger number of spectral lines, the contribution from the UV diminishes, leading to lower mass-loss rates. We fitted three theoretical prescriptions for $\dot{M}$ using a Bayesian approach; this yielded Pearson correlation values greater than 0.92 for all three model grids. It also allowed for the estimation of the wind momentum-luminosity relationships for each of the grids, yielding results similar to those based on observations of O-type stars.
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All authors F. Figueroa-Tapia, J. A. Panei, M. Curé, I. Araya, S. Ekström, A. C. Gormaz-Matamala, R. O. J. Venero, L. S. Cidale

Solar and Stellar Astrophysics

The role of radiative torques in the molecular cloud core L43

Marco Leon Scheiter and Sebastian Wolf

Polarized emission from interstellar dust grains is commonly used to infer information about the underlying magnetic field from the diffuse interstellar medium to molecular cloud cores. Therefore, the ability to accurately determine properties of the magnetic field requires a thorough understanding of the dust alignment mechanism. We investigate the influence of anisotropic radiation fields on the alignment of dust particles by magnetic fields, known as radiative torque (RAT) alignment. Specifically, we take advantage of the unique spatial configuration of the molecular cloud core L43, which contains an embedded yet optically visible star acting as a local source of anisotropic illumination. Based on polarization maps obtained at wavelengths of $154 \mu\mathrm{m}$ (SOFIA/HAWC+), as well as $450 \mu\mathrm{m}$ and $850 \mu\mathrm{m}$ (JCMT/SCUBA-2), which show variations in the degree and angle of polarized emission across all wavelengths, we applied the differential measure analysis method to infer magnetic field strengths and analyze the global polarization spectrum of this source. We derived plane-of-sky magnetic field strengths ranging from approximately 13 to 60 $\mu\mathrm{G}$, varying with wavelength, and find a negative slope of the polarization spectrum. Compared to 3D radiative transfer simulations, this finding can be attributed, at least partially, to variations in dust properties and temperatures along the line of sight. However, the additional influence of variations in the magnetic field orientation along the line of sight cannot be ruled out. Our results favor radiative torques as the primary alignment mechanism, as they indicate that the degree of polarization is dependent on temperature and hence the strength of the local radiation field.
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High Energy Astrophysical Phenomena

Resolving the Multiple Component Outflows in PG 1211+143: II. The Soft X-ray View of the Ultra Fast Outflow

James Reeves, Valentina Braito, Misaki Mizumoto et al. (+16 more)

The nearby quasar, PG 1211+143, has one of the prototype examples of an ultra fast outflow (UFO), as seen in several past XMM-Newton and Chandra observations. In December 2024, PG 1211+143 was observed simultaneously with XRISM Resolve and XMM-Newton, allowing both the Fe K and soft X-ray outflows to be examined at high resolution simultaneously. The Resolve spectrum revealed a forest of Fe K band absorption lines from the UFO (Mizumoto et al. 2026), comprising of up to six discrete velocity components ranging from $v/c=-0.074$ to $v/c=-0.40$. Here we present the simultaneous XMM-Newton RGS (Reflection Grating Spectrometer) spectrum, where three lower ionization counterparts of the Fe K velocity zones are observed; at $v/c=-0.074, -0.12$ and $-0.33$. The soft X-ray absorbers tend to be somewhat less ionized than their Fe K counterparts, with their opacity mainly arising from Fe L shell lines and highly ionized Oxygen. From comparing the Resolve and RGS absorbers, we show that the outflow can be parameterized with a density profile varying with radius as $r^{-5/3}$, while the lower ionization zones likely originate from denser clumps of gas. Pure electron scattering appears insufficient to provide enough thrust to power the wind, unless sufficient low ionization gas capable of radiative line driving exists outside of the line of sight. Overall, PG 1211+143 provides further evidence for the clumpy nature of accretion disk winds, as was recently revealed in the quasar PDS 456 with XRISM.
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All authors James Reeves, Valentina Braito, Misaki Mizumoto, Steven Kraemer, Ehud Behar, Chris Done, Kouichi Hagino, Gabriele Matzeu, Hirofumi Noda, Mariko Nomura, Shoji Ogawa, Ken Ohsuga, Atsushi Tanimoto, Tracey Turner, Yoshihiro Ueda, Satoshi Yamada, Sreeparna Ganguly, Paolo Somenzi, Omer Reich

Earth and Planetary Astrophysics

Benchmarking Photolysis Rates with Socrates (24.11): Species for Earth and Exoplanets

Sophia M. Adams, James Manners, Nathan Mayne et al. (+2 more)

Using the Socrates photolysis scheme, we present newly calculated photolysis rates under modern Earth atmospheric conditions for species directly relevant to Earth and species relevant to different atmospheric compositions. We compare to a previous photolysis comparison exercise, namely PhotoComp 2011. Overall, we find good agreement between our results and previous work, with discrepancies usually caused by the implementation of temperature or pressure dependent quantum yields and updated cross-section data. We provide a new set of benchmark photolysis rates for additional species both for Solar irradiance and when irradiated by an M dwarf host star. In general, the higher actinic flux at far-UV and shorter wavelengths of the M dwarf compared to the Sun drives increased photolysis rates for reactions with high threshold energies. This work provides an updated set of benchmark results for further studies of photolysis in the Earth's atmosphere and that of other planets.
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All authors Sophia M. Adams, James Manners, Nathan Mayne, Mei Ting Mak, Éric Hébrard

Cosmology and Nongalactic Astrophysics

Euclid preparation. CIV. Impact of galaxy intrinsic alignment modelling choices on Euclid 3x2pt cosmology

Euclid Collaboration: D. Navarro-Gironés, I. Tutusaus, M. Crocce et al. (+273 more)

The Euclid galaxy survey will provide unprecedented constraints on cosmology, but achieving unbiased results will require an optimal characterisation and mitigation of systematic effects. The intrinsic alignments (IAs) of galaxies are one of the dominant contaminants of the weak lensing (WL) and galaxy-galaxy lensing (GGL) probes. In this work, we assess IA modelling choices for Euclid DR1 3x2pt analyses by using synthetic data vectors and comparing the performance of the two most commonly used IA models, non-linear alignment (NLA) and tidal alignment tidal torquing (TATT), along with several variations. Our analyses combine three perspectives: (i) the constraining power on the IA and cosmological parameters for each IA model, (ii) the bias that results when the IA analysis model differs from the model used to generate the synthetic data vector, and (iii) the degeneracies between IAs and photometric redshift (photo-z) nuisance parameters. Amongst the IA models analysed, the redshift-dependent TATT model (zTATT) provides the most flexible description of IAs, with a constraining power similar to simpler IA models, making it a suitable choice for Euclid DR1 3x2pt analyses.
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All authors Euclid Collaboration: D. Navarro-Gironés, I. Tutusaus, M. Crocce, S. Gouyou Beauchamps, R. Paviot, B. Joachimi, J. Ruiz-Zapatero, D. Sciotti, N. Tessore, J. Blazek, G. Cañas-Herrera, P. Carrilho, J. M. Coloma-Nadal, H. Hoekstra, A. Porredon, B. Altieri, S. Andreon, C. Baccigalupi, M. Baldi, S. Bardelli, A. Biviano, M. Bolzonella, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, V. F. Cardone, J. Carretero, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Escoffier, M. Farina, R. Farinelli, S. Farrens, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, L. Gabarra, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, S. Kermiche, A. Kiessling, M. Kilbinger, B. Kubik, K. Kuijken, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, N. Mauri, E. Medinaceli, M. Meneghetti, E. Merlin, G. Meylan, P. Monaco, A. Mora, M. Moresco, C. Moretti, L. Moscardini, R. Nakajima, C. Neissner, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, I. Risso, E. Romelli, M. Roncarelli, C. Rosset, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, P. Tallada-Crespí, I. Tereno, S. Toft, R. Toledo-Moreo, F. Torradeflot, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, Y. Wang, J. Weller, F. M. Zerbi, E. Zucca, M. Ballardini, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, T. Castro, J. A. Escartin Vigo, J. García-Bellido, J. Macias-Perez, R. Maoli, J. Martín-Fleitas, R. B. Metcalf, M. Pöntinen, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, L. Bazzanini, J. Bel, D. Bertacca, M. Bethermin, F. Beutler, A. Blanchard, L. Blot, M. Bonici, M. L. Brown, S. Bruton, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, P. Dimauro, V. Duret, M. Y. Elkhashab, Y. Fang, P. G. Ferreira, A. Finoguenov, A. Franco, K. Ganga, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, E. J. Gonzalez, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, A. Montoro, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, L. Pagano, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, C. Pattison, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, K. Rojas, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, E. Sellentin, L. C. Smith, K. Tanidis, F. Tarsitano, R. Teyssier, A. Troja, D. Vergani, F. Vernizzi, G. Verza, P. Vielzeuf, S. Vinciguerra, N. A. Walton, A. H. Wright, S.-S. Li

Instrumentation and Methods for Astrophysics

The Astronomical Telescope of the University of Stuttgart (ATUS): Development, Optimization, and Lessons Learned

Karsten Schindler, Jürgen Wolf and Alfred Krabbe

ATUS, the Astronomical Telescope of the University of Stuttgart, is a fully remote-controlled 0.6 m f/8.17 Ritchey-Chrétien telescope optimized for high-cadence, high-fidelity photometry of transient sources. Observations are time-referenced with very high accuracy and precision, making it an ideal platform for time-domain astronomy and space situational awareness. Initially conceived to support instrument developments and operations of SOFIA, the Stratospheric Observatory for Infrared Astronomy, it evolved into a scientific instrument for various use cases in instrument development, astronomical research, and teaching. This paper presents an overview of its development and optimization to achieve diffraction-limited images and highly accurate pointing and tracking, even at high speeds. The findings and lessons learned are universally applicable to other telescopes that are currently at the planning stage, or where similar issues might be encountered.
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2602.16415 · 18 Feb · 44 pages, 30 figures, 8 tables. This is the Accepted Manuscript version of an article accepted for publication in the Publications of the Astronomical Society of the Pacific. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it

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Earth and Planetary Astrophysics

Deepest ever photographed Geminid with small but not negligible terminal mass

Pavel Spurný and Jiří Borovička

We report an instrumental observation of the very exceptional Geminid fireball which was observed in scope of the Czech part of the European Fireball Network (EN) on 13 December 2012 at 4h12m59.4s UT. The uniqueness of this Geminid fireball consists of the record depth of its penetration in the atmosphere (to the height of 32.5 km) and in the fact that most likely a very small fraction of its initial mass survived severe deceleration in the atmosphere and landed on the ground. Such deeply penetrating Geminid with so precise and reliable data has not yet been observed. From a comparison with a large number of Geminids observed by the European Fireball Network and all brightest Geminids from the Prairie Fireball Network in USA and the Canadian MORP Network, we have shown that for Geminids with an entry mass greater than approximately 10 grams, the terminal altitude limit does not decrease further as it does for smaller Geminids, but remains constant at around 38 km. In this comparison, we have shown that there is only one exception, and that is the Geminid presented here. This one penetrated nearly 6 km deeper with very low terminal speed for Geminids. During the atmospheric flight this Geminid meteoroid slowed down from its original speed of 35.75 km/s to 6.8 km/s. This small meteoroid with initial mass of only 0.25 kg is probably the fastest candidate for a meteorite dropping event ever observed. This solid meteoroid belonging to the meteor shower survived a significant dynamic pressure of almost 2 MPa and thus ranks among the interplanetary bodies of asteroidal origin that caused the observed meteorite fall. Although a similar Geminid event has been previously presented in the literature, we demonstrate here that this claim was flawed.
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Solar and Stellar Astrophysics

Accretion Disk Magnetic Braking

Kurt Liffman

A protostellar disk is threaded by a static magnetic field that is perpendicular to the disk-surface. The magnetic field acts to brake the protostellar disk and cause the disk material to move towards the protostar. General analytic equations are derived for the accretion speed, and mass accretion rate. Simplified analytic equations are also obtained for the disk energy dissipation, accretion timescale and the disk radial position plus disk surface density, as a function of time. In addition to providing physical insight, such equations might be useful as a check on computational models for protostar and protostellar disk formation.
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Solar and Stellar Astrophysics

Localized $^{18}$O production in white dwarf mergers

Alexander Holas, Veronica Agaeva, Friedrich K. Roepke et al. (+5 more)

The merger of a He white dwarf (WD) and a CO WD is the favored formation channel for R Coronae Borealis (RCB) stars. These stars exhibit ${^{16}}\mathrm{O}/{^{18}}\mathrm{O}$ ratios that are orders of magnitude lower than the solar value. However, it is not fully understood whether such low ${^{16}}\mathrm{O}/{^{18}}\mathrm{O}$ ratios can be achieved in WD merger remnants for the predicted lifetime of RCB stars of around $10^4\,\mathrm{years}$. In this work, we perform detailed nucleosynthesis calculations of a 3D magnetohydrodynamical simulation of a merger of a $0.3\,M_\odot$ He WD and a $0.6\,M_\odot$ CO WD for $4000\,\mathrm{s}$ at which point a steady state in temperature and density is reached. From this point, we follow several radial zones to study the long-term production of ${^{18}}\mathrm{O}$ and its variability throughout the burning region. We find that the asymmetric merger process leaves an imprint on the distribution of the abundances at the end of our hydrodynamic simulation. During the long-term evolution up to $100\,\mathrm{years}$, we observe ${^{16}}\mathrm{O}/{^{18}}\mathrm{O}$ ratios of order of unity, although the timescale on which ${^{18}}\mathrm{O}$ is destroyed again is highly location dependent. Importantly, our calculations suggest that in the outer layers of the burning shell, the dominant production channel is $^{14}\mathrm{C}(\alpha,\gamma)^{18}\mathrm{O}$ instead of the commonly considered $^{14}\mathrm{N}(\alpha,\gamma)^{18}\mathrm{F}(\beta^+)^{18}\mathrm{O}$ reaction, whereby the former can be sustained for longer periods of time. Furthermore, these outer regions do not reach the conditions necessary for fast $\alpha$-captures in ${^{18}}\mathrm{O}$ to ${^{22}}\mathrm{Ne}$, thus being favorable to maintaining a low ${^{16}}\mathrm{O}/{^{18}}\mathrm{O}$ ratio.
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All authors Alexander Holas, Veronica Agaeva, Friedrich K. Roepke, Samuel W. Jones, Javier Moran-Fraile, Marco Vetter, Rüdiger Pakmor, Philipp Podsiadlowski

Cosmology and Nongalactic Astrophysics

High significance detection at 4.8 GHz of the radio halo in the Coma galaxy cluster with the Sardinia Radio Telescope

P. Marchegiani, M. Murgia, F. Loi et al. (+4 more)

We present the results of observations of the radio halo in the Coma galaxy cluster at 4.8 GHz performed with the Sardinia Radio Telescope. The radio halo in this cluster is detected for the first time at this frequency with a statistical significance higher than $3\sigma$. After the removal of the Radio Frequency Interference and of the discrete sources contribution, and after the correction for the Sunyaev-Zel'dovich effect, we estimate a flux density of $61\pm11$ mJy, higher than the value previously reported in literature at this frequency. By using the value we obtained, it is possible to estimate an integrated spectral index between 4.8 and 6.6 GHz of $\alpha\sim1.17$, where $F(\nu)\propto \nu^{-\alpha}$, indicating a possible higher-frequency slowdown of the spectral steepening observed between 1.4 and 4.8 GHz. Such a spectral behavior is compatible with turbulent re-acceleration if the seed electrons have a spectrum extending up to high energies, as in the case of continuous injection by hadronic interactions or dark matter annihilation. We also report the detection at 4.8 GHz of a polarized spot inside the halo, without an evident counterpart, already detected at 6.6 GHz.
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All authors P. Marchegiani, M. Murgia, F. Loi, V. Vacca, F. Govoni, S. Cocchi, F. Gandossi

Earth and Planetary Astrophysics

Numerical analysis of Lyapunov Times for Trans-Neptunian Objects and Main-Belt Asteroids: stability, accuracy, and methodological comparisons

Paweł Wajer, Małgorzata Królikowska and Jakub Suchecki

We computed Lyapunov times ($T_L$) for a sample of trans-Neptunian objects (TNOs) and outer main-belt asteroids (MBAs) using three numerical approaches: the variational method and two implementations of the renormalization technique. For each object, $T_L$ was derived both from the nominal orbit and from ensembles of 1001 orbital clones, enabling direct comparison between single-orbit and ensemble-based estimates. Across the sample, the methods generally produced consistent results, though larger discrepancies were observed for some MBAs. TNOs, in contrast, displayed greater consistency across methods, likely due to fewer overlapping resonances. Importantly, clone ensembles provided more robust and reliable stability indicators than nominal-orbit computations. Median values from clone populations reduced method-dependent biases and revealed dynamical behaviors that would remain hidden in single-orbit analyses, especially for objects with poorly constrained orbits or evolving in resonant regions. While our study focused on a limited but diverse set of objects, the methodology can be directly extended to larger populations, offering a systematic framework for exploring the long-term stability and dynamical evolution of main-belt asteroids, trans-Neptunian objects or other classes of objects in the Solar System.
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Earth and Planetary Astrophysics · Cross-listed from math.SG

Comet-type periodic motions and their out-of-plane bifurcations in the Earth-Moon CR3BP: a computational symplectic analysis

Cengiz Aydin

Comet-type periodic orbits of the circular restricted three-body problem (CR3BP) are periodic solutions that are generated from very large retrograde and direct circular Keplerian motions around the common center of mass of the primaries. In this paper we first provide an analytical proof of the existence of the comet-type periodic orbits by using the classical Poincaré continuation method. Within this analytical approach, we also determine the Conley-Zehnder index, defined as a Maslov index using a crossing form. Then, by applying a standard corrector-predictor technique, we explore numerically the two families of comet orbits within the Earth-Moon CR3BP. We compute their stability indices, identify vertical self-resonant bifurcations of higher order periods (of multiplicity from integer multiples up to six), investigate the vertically bifurcated spatial periodic solutions, and discuss their orbital characteristics. We also describe the orbits that are in resonance with the Earth and the Moon. We illustrate our main results in the form of bifurcation graphs, based on symplectic invariants, that provide a topological overview of the connections of the bifurcated branches, including bridge families.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det

Characterization of an MPPC-Based Scintillator Telescope and Measurement of Cosmic Muon Angular Distribution

Sahla Manithottathil, Anuj Gupta, Mudit Kumar et al. (+1 more)

This report presents the design, characterization, and application of a high-sensitivity optical detection system based on plastic scintillators coupled to Multi-Pixel Photon Counters (MPPCs). The primary objective was to evaluate the performance of MPPCs (Silicon Photomultipliers) as robust, low-voltage alternatives to traditional photomultiplier tubes for detecting faint scintillation light. The optoelectronic properties of the sensors were analyzed, including single-photoelectron gain calibration and dark count rate measurements, to optimize the signal-to-noise ratio. By embedding wavelength-shifting fibers to enhance light collection efficiency, the system was configured into a three-fold coincidence telescope. The angular distribution of the cosmic ray muon flux was measured to validate the detector's stability and geometric acceptance. Fitting the experimental data to a $\bm{\cos^n(\theta)}$ distribution yielded an angular exponent of $\bm{n = 1.44 \pm 0.06}$, consistent with literature values. These results demonstrate the efficacy of the MPPC-scintillator coupling for precise photon counting and timing applications in high-energy physics instrumentation.
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All authors Sahla Manithottathil, Anuj Gupta, Mudit Kumar, Navaneeth Poonthottathil

Cosmology and Nongalactic Astrophysics

SPT-CL J0417-4748: A Deep Chandra Study of a Relaxed Galaxy Cluster Without Central Star Formation

Taweewat Somboonpanyakul, Adam B. Mantz, Steven W. Allen et al. (+7 more)

We present an in-depth Chandra X-ray analysis of the galaxy cluster SPT-CL J0417$-$4748 (hereafter SPT J0417), at z = 0.58, with a focus on its thermodynamic properties and the apparent absence of central star formation. Utilizing a total Chandra exposure of 103 ks, we find that the large-scale X-ray morphology is consistent with a dynamically relaxed, cool-core system. The intracluster medium (ICM) shows a central density of 0.08+/-0.01 cm^{-3}, a central pseudo-entropy of 26^{+6}_{-5} keVcm^{2} and a central cooling time of 515^{+96}_{-75} Myr, values typical of massive cool-core clusters. Despite these conditions, no evidence of recent or ongoing star formation is detected in the brightest cluster galaxy (BCG). Spectral energy distribution (SED) fitting of DES photometry indicates that the bulk of the stellar population formed at z~1.25, with no significant star formation over the past ~3 Gyr, while optical spectra from Magellan show no [O II] emission. Complementary ASKAP radio and Spitzer infrared data indicate a lack of strong current AGN activity in the BCG. SPT J0417 exemplifies massive, relaxed, cool-core clusters in which cooling and star formation appear almost completely quenched, providing valuable insights into how AGN feedback regulates the long-term thermal balance of the intracluster medium.
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All authors Taweewat Somboonpanyakul, Adam B. Mantz, Steven W. Allen, Anthony M. Flores, R. Glenn Morris, Haley R. Stueber, Lindsey E. Bleem, Benjamin Floyd, Julie Hlavacek-Larrondo, Keunho J. Kim

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

Gravitational Waves from Primordial Black Holes formed by Null Energy Condition Violation during Inflation

Dong-Hui Yu, Jia-Zuo Zhang and Yong Cai

A transient violation of the null energy condition (NEC) during inflation provides a novel mechanism for producing primordial black holes (PBHs) and stochastic gravitational wave (GW) backgrounds. In this work, we extend previous studies by computing the GW contributions from both the ringdown phase of PBH formation and subsequent binary mergers. Our results show that this scenario produces a rich, multi-component GW spectrum consisting of primordial GWs, scalar-induced GWs, and GW emissions from PBH ringdown and binary mergers. We demonstrate that these correlated signatures across different frequency bands provide a novel and powerful avenue to probe or constrain NEC violation during inflation through future multi-band GW observations.
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Solar and Stellar Astrophysics · Cross-listed from cs.LG

Prediction of Major Solar Flares Using Interpretable Class-dependent Reward Framework with Active Region Magnetograms and Domain Knowledge

Zixian Wu, Xuebao Li, Yanfang Zheng et al. (+14 more)

In this work, we develop, for the first time, a supervised classification framework with class-dependent rewards (CDR) to predict $\geq$MM flares within 24 hr. We construct multiple datasets, covering knowledge-informed features and line-of sight (LOS) magnetograms. We also apply three deep learning models (CNN, CNN-BiLSTM, and Transformer) and three CDR counterparts (CDR-CNN, CDR-CNN-BiLSTM, and CDR-Transformer). First, we analyze the importance of LOS magnetic field parameters with the Transformer, then compare its performance using LOS-only, vector-only, and combined magnetic field parameters. Second, we compare flare prediction performance based on CDR models versus deep learning counterparts. Third, we perform sensitivity analysis on reward engineering for CDR models. Fourth, we use the SHAP method for model interpretability. Finally, we conduct performance comparison between our models and NASA/CCMC. The main findings are: (1)Among LOS feature combinations, R_VALUE and AREA_ACR consistently yield the best results. (2)Transformer achieves better performance with combined LOS and vector magnetic field data than with either alone. (3)Models using knowledge-informed features outperform those using magnetograms. (4)While CNN and CNN-BiLSTM outperform their CDR counterparts on magnetograms, CDR-Transformer is slightly superior to its deep learning counterpart when using knowledge-informed features. Among all models, CDR-Transformer achieves the best performance. (5)The predictive performance of the CDR models is not overly sensitive to the reward choices.(6)Through SHAP analysis, the CDR model tends to regard TOTUSJH as more important, while the Transformer tends to prioritize R_VALUE more.(7)Under identical prediction time and active region (AR) number, the CDR-Transformer shows superior predictive capabilities compared to NASA/CCMC.
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All authors Zixian Wu, Xuebao Li, Yanfang Zheng, Rui Wang, Shunhuang Zhang, Jinfang Wei, Yongshang Lv, Liang Dong, Zamri Zainal Abidin, Noraisyah Mohamed Shah, Hongwei Ye, Pengchao Yan, Xuefeng Li, Xiaojia Ji, Xusheng Huang, Xiaotian Wang, Honglei Jin

Astrophysics of Galaxies

PDRs4All XVIII. JWST-NIRCam Photometric properties of protoplanetary disks in the Orion Nebula Cluster

P. Amiot, O. Berné, I. Schroetter et al. (+10 more)

We use the high angular resolution NIRCam images from the PDRs4All program, combined with those of GTO program 1256, to extract key properties of disks in the Orion Nebula Cluster. We measure disk radii in silhouette against the bright background, identify dissociation fronts (DFs) and ionization fronts (IFs), determine Paschen $\alpha$ intensities, and derive near-infrared spectral energy distributions (SEDs). From these diagnostics we define a typology of ONC disks. Type I sources show merged IFs and DFs close to the disk surface. Type II sources have DFs at the disk surface and IFs located tens of astronomical units away. Type III sources show a DF at the disk surface but no IF. For all types, PAH emission traces the PDR. We find that the disk radius $r_{\rm disk}$ increases with projected distance to the ionizing source $d_{\rm proj}$, following $r_{\rm disk} \propto d_{\rm proj}^{0.30}$, consistent with disk truncation by photoevaporation. Disk radii measured in the infrared are larger than those measured at millimeter wavelengths, suggesting radial dust segregation within the disks. In agreement with PDR models, the thermal pressure in the disk PDR increases with the FUV radiation field $G_0$, but with a flatter slope. Finally, the SEDs of candidate Jupiter Mass Binary Objects (JuMBOs) are similar to those of Type III disks, except for JuMBO24, which resembles a Type I or Type II source. Its SED is consistent with a young low-mass binary hosting an unresolved ionized disk.
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All authors P. Amiot, O. Berné, I. Schroetter, M. Robberto, T. J. Haworth, C. Boersma, E. Dartois, A. Fuente, J.R. Goicoechea, E. Habart, M. J. McCaughrean, T. Onaka, E. Peeters

High Energy Astrophysical Phenomena

A XRISM view of the iron line complex in NGC 1068: Rethinking the prototypical Compton-thick AGN

S. Bianchi, B. Vander Meulen, E. Bertola et al. (+32 more)

We analyze a XRISM/Resolve observation of NGC1068, focusing on the Fe K$\alpha$ and Fe K$\beta$ fluorescent lines and on the Fe XXV and Fe XXVI emission complexes. Line centroid energies, intrinsic widths, flux ratios, and constraints on the Compton shoulder are derived through local spectral fitting, and compared with atomic calculations and theoretical predictions. The centroid energies of the Fe K$\alpha$ and Fe K$\beta$ lines tightly constrain the emitting material to be neutral or near-neutral. The observed Fe K$\beta$/K$\alpha$ ratio, together with the stringent upper limit on the Compton shoulder ($\lesssim$8–11% of the core flux), disfavour reflection dominated by a homogeneous, classical Compton-thick medium, indicating that most of the neutral Fe K$\alpha$ emission arises in optically thin or moderately Compton-thick gas. The Fe XXV and Fe XXVI emission lines exhibit remarkably large velocity widths, of several thousand km~s$^{-1}$. These broad profiles closely resemble the integrated optical and infrared [O III] and [O IV] lines associated with the large-scale biconical outflow, and are naturally interpreted as the X-ray signature of a more highly ionized, faster, and more spatially confined phase of the same outflow. The iron-K emission of NGC1068 reveals a stratified circumnuclear environment in which neutral and highly ionized components arise in physically distinct regions. The neutral Fe K fluorescence originates predominantly in optically thin or mildly Compton-thick material, despite the persistently Compton-thick line-of-sight obscuration, indicating a geometrically complex cold reprocessor. The highly ionized iron emission lines trace a fast component consistent with a warm bipolar outflow on parsec scales, whose large velocities and inferred energetics suggest that it may represent an efficient channel for feedback in a heavily obscured Seyfert galaxy.
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All authors S. Bianchi, B. Vander Meulen, E. Bertola, V. Braito, A. Comastri, P. Condò, M. Dadina, R. Della Ceca, A. De Rosa, V. E. Gianolli, M. Guainazzi, K. Iwasawa, E. Kammoun, M. Laurenti, A. Luminari, A. Marinucci, G. Matt, G. Matzeu, R. Middei, G. Miniutti, E. Nardini, F. Nicastro, F. Panessa, P.-O. Petrucci, E. Piconcelli, C. Pinto, G. Ponti, R. Serafinelli, P. Severgnini, D. Tagliacozzo, F. Tombesi, A. Tortosa, F. Ursini, C. Vignali, L. Zappacosta

Solar and Stellar Astrophysics

Propagation Characteristics of the April 21, 2023 CME

Sandeep Kumar, Nandita Srivastava, Parthib Banerjee et al. (+1 more)

Accurate estimation of propagation characteristics of coronal mass ejections (CMEs) is crucial for predicting their geoeffectiveness. Stereoscopic techniques to study the kinematics of CMEs generally have been carried out using remote sensing observations from three viewpoints, i.e. STEREO-A, STEREO-B, and SOHO. Since the loss of STEREO-B in 2014, stereoscopic reconstruction of CMEs has been restricted to the observations from only two viewpoints, i.e., STEREO-A and SOHO. When the angle of separation between STEREO-A and SOHO is small, it leads to larger uncertainties in the CME kinematics derived using stereoscopic techniques. In this paper, we demonstrate how this limitation can be addressed and how uncertainties in the estimation of CME kinematics and propagation direction can be reduced. For this purpose, we selected the CME of April 21, 2023, which was observed by two spacecraft, i.e. STEREO-A and SOHO, separated by a small 10 degree angle. Using the Graduated Cylindrical Shell (GCS) model on the remote-sensing observations near the Sun and the Advanced Drag-Based Model (ADBM) in the heliosphere, we estimated the arrival time of the CME at different locations in the heliosphere and compared it with the actual arrival time obtained from the in-situ measurements taken by three spacecraft, BepiColombo, STEREO-A and Wind. Our analysis reveals a directional uncertainty of approx 20 degree from observations from two viewpoints. These uncertainties significantly affect the arrival-time prediction of the CME. We consider the actual chronology of CME arrival times at STEREO-A and Wind as critical parameters to constrain the direction of propagation, which serves as a key input in the ADBM. The chronology of arrival of the CME ejecta at STEREO-A, which is 4.5 hrs earlier than at Wind, proved essential for resolving directional ambiguities in the GCS reconstruction model
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All authors Sandeep Kumar, Nandita Srivastava, Parthib Banerjee, Nat Gopalswamy

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

Phenomenological Rotating Extension of Black Holes with Primary Scalar Hair: Shadow Signatures in Beyond Horndeski Gravity

Kourosh Nozari, Milad Hajebrahimi, Sara Saghafi et al. (+2 more)

The Event Horizon Telescope (EHT) image of M87* provides a direct test of strong-field gravity, measuring an angular shadow diameter $\theta_{d}=42\pm 3~\mu\mathrm{as}$ and a circularity deviation $\Delta C\leq 0.1$. Such observations allow quantitative tests of the Kerr paradigm and of possible deviations from the no-hair theorem. In scalar-tensor extensions of gravity, black holes may possess primary scalar hair, introducing an additional independent parameter beyond mass and spin. In this work, we construct a rotating configuration inspired by black hole solutions with primary scalar hair in beyond Horndeski gravity and analyze their photon regions and shadow formation. We show that the scalar hair parameter $Q$ induces characteristic modifications of the shadow, and in particular negative $Q$ enlarges the shadow and reduces its oblateness, while positive $Q$ shrinks and enhances its distortion. Adopting M87* as a representative case within this framework and imposing the EHT bounds on $\theta_{d}$ and $\Delta C$, we identify the viable $(a,Q)$ parameter space. We find that current observations do not exclude rotating black holes with primary scalar hair, although the allowed region is significantly restricted for $Q>0$. Finally, the scalar-hair-induced deviations are of order $\mathcal{O}(\mu\mathrm{as})$, placing them near the sensitivity threshold of present instruments and within reach of next-generation horizon-scale imaging.
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All authors Kourosh Nozari, Milad Hajebrahimi, Sara Saghafi, G. Mustafa, Emmanuel N. Saridakis

High Energy Astrophysical Phenomena

The Enigmatic Type Icn Supernova 2024abvb Located ~22 kpc from Its Host Galaxy

J. Shi, K. Auchettl, W. B. Hoogendam et al. (+29 more)

We report multiwavelength observations of the highly offset (~22.4 kpc) SN 2024abvb, the sixth Type Icn supernova to date. With a peak magnitude of Mr = -19.55 +/- 0.11 mag, it is among the most luminous in the existing sample and shows similar colours and decline rates to other SNe Icn. The early optical spectra show a blue continuum with narrow C II features (vFWHM ~ 2000 km s^-1), consistent with a typical wind velocity of a Wolf-Rayet star. The absence of C III lambda 5696 emission at the time of explosion is consistent with a Type Ibn supernova; however, the lack of narrow He lines in both the optical and near-infrared spectra supports a SNe Icn classification. Unlike the majority of SNe Icn, we do not detect broad features in the late-time (7-21 days relative to o-band peak) spectral phase of SN 2024abvb. Semi-analytical modelling of the light curves shows that it can be reproduced by ~2.6 Msun of SN ejecta interacting with ~0.3 Msun of circumstellar material (CSM), both larger than other SNe Icn but consistent with rapidly evolving SNe Ibn. The metallicity at the SN location is significantly lower than the global metallicity of its host galaxy, suggesting that line-driven mass loss required to strip the progenitor of its H and He envelopes was likely inefficient. We estimate the star-formation-rate history at the location of SN 2024abvb and find that it lies at the bottom ~5th percentile among SESNe hosts, inconsistent with a Wolf-Rayet progenitor. Based on its spectral features, local and host environment properties, and host-galaxy offset, we favour an 8-10 Msun star stripped by a compact companion as the progenitor, with a sufficient runaway velocity to reach the observed offset.
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All authors J. Shi, K. Auchettl, W. B. Hoogendam, D. Farias, N. Sarin, K. W. Davis, N. Morrell, J. T. Hinkle, D. O. Jones, C. Lidman, C. Angus, C. Ashall, C. R. Burns, D. D. Desai, A. Do, L. Galbany, E. Y. Hsiao, M. E. Huber, M. Y. Kong, B. Martin, K. Medler, A. Möller, C. Pfeffer, A. Polin, L. Rauf, S. Romagnoli, B. Schmidt, B. J. Shappee, M. D. Stritzinger, A. Syncatto, B. E. Tucker, M. A. Tucker

Solar and Stellar Astrophysics

Reinterpreting the sunward electron deficit: Implications for solar wind acceleration and core population formation

Zoltan Nemeth

This paper re-evaluates the relationship between the observed sunward electron cutoff energy and the depth of the Sun's global electrostatic potential. It investigates whether taking into account the effects of local traps formed by magnetic fluctuations provides an alternative explanation for the observed electron deficit. The fluctuations of the highly variable interplanetary magnetic field form a series of shallow magnetic mirror traps that move at approximately the speed of the solar wind. The study investigates the dynamics of electrons as they move outward against an attractive solar electrostatic potential and interact with these traps. By following the motion of the electrons using first-principles calculations, we assess the effect of the traps on the velocity distribution of the particles. Electrons that escape the local trap continue to lose energy as they move outward until they are eventually captured by subsequent traps, preventing them from returning to the observer as sunward-moving particles. We derive a mathematical expression for the cutoff velocity, defined as the limit beyond which particles can no longer overtake the outer endpoint of a local trap. It turns out that the observed cutoff energy characterizes only the local potential drop within a trap, rather than the total depth of the Sun's potential well. The true potential well can be significantly deeper, scaled by the ratio of the radial distance from the Sun to the trap size. Furthermore, electrons captured by these moving traps contribute to the formation of the solar wind core population. The Sun's electrostatic potential is a more significant factor in solar wind acceleration than previously interpreted from cutoff data. The interaction between electrostatic deceleration and moving magnetic traps provides a new framework for understanding the origin and behavior of the solar wind core electrons.
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High Energy Astrophysical Phenomena

Cosmic-Ray Spectra and Metal Budget Regulated by the Galactic Wind

Yusaku Fukumoto, Katsuaki Asano and Jiro Shimoda

We study the advection effect of the Galactic wind on the local cosmic ray spectra. The spectral hardening from a few hundred GV and softening from a few TV are reproduced by a velocity profile with a maximum velocity of $\sim 700~\mbox{km}~ \mbox{s}^{-1}$ without introducing a break in the power-law dependence of the diffusion coefficient. Additionally, we find that a hard CR spectrum below $\sim$ TV with an index of $\sim 2$ at an altitude $\sim 3$-$5$ kpc from the Galactic disk. This hard spectrum is favorable for the gamma-ray spectrum of the Fermi bubbles. With the obtained CR fluxes, we discuss the matter circulation in our Galaxy with the wind. While the wind has an essential role in maintaining the metal abundance in the disk, the production rate of Beryllium, which originates from CR spallation, is so low that the ratio Be/O in the halo should be larger than that in the disk gas.
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Solar and Stellar Astrophysics

Investigating Ionospheric TEC Variations in Solar and Geomagnetic Influences Across Solar Activity Phases

Ziyadat Hassan, Zamri Zainal Abidin, Affan Adly Nazri et al. (+1 more)

This study examines the variability of ionospheric total electron content (VTEC) in response to solar and geomagnetic drivers across solar cycles 23 to 25. While the dominant effect of solar radiation on VTEC is well-known, a comprehensive understanding of how these relationships and their time-lags vary across distinct solar cycle phases and across cycles of differing intensity has been lacking. Using global VTEC data from the Chinese Academy of Sciences Global Ionospheric Maps (CASG) and solar-geophysical indices from NASA's OMNI dataset spanning from 1998 to 2025, this study bridges that gap by quantifying correlation strengths and time-lag relationships between VTEC and parameters such as $F_{10.7}$ solar flux, R sunspot number, Kp, Ap, and Dst indices, and solar wind properties. Results show that solar proxies, particularly $F_{10.7}$ and R sunspot number, exhibit the strongest, most consistent correlations with VTEC, especially during the ascending and descending phases of the solar cycle, with a characteristic $\sim2$-day lag attributed to thermospheric oxygen dynamics and ionospheric recombination processes. In contrast, geomagnetic indices exhibit weaker and phase-dependent correlations, while direct correlations between solar wind parameters and global VTEC are weak, as their influence is primarily mediated by geomagnetic activity and exhibits strong regional and temporal heterogeneity. Phase-resolved analyses further reveal that geomagnetic activity plays a more prominent role during transitional phases, while maximum and minimum periods are dominated by EUV variability and non-solar drivers, respectively. These findings highlight the necessity of incorporating solar phase and time-lag dependencies in ionospheric modelling and forecasting efforts.
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All authors Ziyadat Hassan, Zamri Zainal Abidin, Affan Adly Nazri, Nursyazela Badrina Baharin