Peer Revenue Returns subject to peer review

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Monday 30 March

Instrumentation and Methods for Astrophysics

Mercury Craters Named after Tajik-Persian Poets: Planetary Nomenclature as a Form of Preserving Cultural Heritage

Rizoi Bakhromzod

Nine impact craters on Mercury bear the names of Persian-Tajik poets: Rudaki, Saadi, Nizami, Rumi, Navoi, Firdousi, Hafiz, Sanai, and Mahsati. We compile IAU-approved coordinates, diameters, quadrant designations, approval dates (1976–2025), and MESSENGER-derived geological characteristics for each crater, and place these data in the broader context of Solar System objects associated with Tajik-Persian civilisation, including lunar craters (Al-Biruni, Avicenna, Omar Khayyam, Abul Wafa, Nasireddin, Alfraganus, Azophi, Al-Khwarizmi), main-belt asteroids, and Enceladus surface features named from the One Thousand and One Nights. The approval timeline mirrors the successive stages of Mercury mapping: two craters were designated after Mariner 10 (1976), three more following Mariner 10 data analysis (1979, 1985), two after the first MESSENGER flybys (2008, 2010), two after MESSENGER orbital operations (2014), and one in 2025. Geological diversity is notable: the Sanai basin (490 km, ~3.8–3.9 Ga) is among the oldest large structures on Mercury; Firdousi shows lava-flooded floor morphology; Rumi hosts an explosive pyroclastic vent intersected by Palmer Rupes; Hafiz contains low-reflectance material and hollows; Navoi is a pit-floor crater; and Nizami exhibits polygonal wall geometry. These results illustrate how planetary nomenclature serves as a stable, internationally maintained record of cultural heritage.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Cosmic Shear in Effective Field Theory at Two-Loop Order: Revisiting $S_8$ in Dark Energy Survey Data

Shi-Fan Chen, Joseph DeRose, Mikhail M. Ivanov et al. (+1 more)

Cosmic shear is a powerful probe of cosmological distances, matter abundance and clustering in the low-redshift Universe. Cosmological parameter extraction from cosmic shear data is limited by our understanding of baryonic astrophysics, which severely restricts the range of scales used in such analyses. We show that the remaining scales are largely perturbative and can be accurately described with two-loop effective field theory (EFT) predictions. We present the first consistent analysis of the public cosmic shear data from the DES-Y3 catalogs in EFT at the two-loop order, renormalizing small-scale sensitivity in cosmic-shear predictions via a lensing-counterterm expansion and accounting for the intrinsic alignments of galaxies with spin-2 EFT predictions. We constrain the lensing amplitude competitively with standard (empirically-modeled) methods, finding $S_8 = 0.783^{+0.038}_{-0.031}$ ($S_8 = 0.802^{+0.031}_{-0.026}$ with BAO). The perturbativity of cosmic shear suggests novel opportunities for testing new physics with ongoing and upcoming cosmic shear experiments like Roman, Euclid, and LSST. As an example, we derive matter clustering constraints within the dynamical dark energy model from a combination of our DES-EFT cosmic shear likelihood, early-universe CMB priors, DESI BAO, and supernovae data, finding $S_8 = 0.824\pm 0.029$, indicating no $S_8$ tension in the growth of cosmic structure regardless of the underlying cosmological model and expansion history.
Read the full abstract

All authors Shi-Fan Chen, Joseph DeRose, Mikhail M. Ivanov, Oliver H. E. Philcox

High Energy Astrophysical Phenomena

The average X-ray spectrum of the volume-complete M-, F-, G-, and K-type star sample within 10 pc of the Sun

Xueying Zheng, Gabriele Ponti, Nicola Locatelli et al. (+15 more)

F, G, K and M type stars are the most abundant stellar population in the Milky Way and are expected to contribute to its diffuse X-ray emission. Yet their intrinsic average X-ray spectrum remains poorly constrained due to their faint X-ray luminosities, leaving their collective role in the X-ray background of the Milky Way uncertain. We analysed the volume-complete sample of M- (M0–M6) and FGK-type stars within 10 pc of the Sun using data from eROSITA all-sky survey aboard the Spectrum-Roentgen-Gamma (SRG) mission (eRASS:4). Individual spectra were normalized by exposure and distance and stacked to produce representative averages. The distance-normalized emission measures yield an average X-ray luminosity of $(2.6 \pm0.1)\times 10^{27}$ erg/s for M-type stars, and $(15\pm3)\times 10^{27}$ erg/s for F, G and K-type stars in 0.2–2.0 keV. The average spectra could be well described by a sum of three and two thermal models. Fitted temperatures and abundances remain consistent across M-star subgroups, while early-M stars are surprisingly on average less luminous than mid/late-M types. These results offer new insights into the collective X-ray properties of nearby stars, and provide motivation to explore the link with the unresolved soft X-ray background of the Galaxy.
Read the full abstract

All authors Xueying Zheng, Gabriele Ponti, Nicola Locatelli, Beate Stelzer, Enza Magaudda, Konrad Dennerl, Michael Freyberg, Jeremy Sanders, Marilena Caramazza, Manami Sasaki, Andrea Merloni, Jan Robrade, Teng Liu, He-shou Zhang, Martin G. F. Mayer, Yi Zhang, Michael C. H. Yeung, Werner Becker

Cosmology and Nongalactic Astrophysics

Estimation and mitigation of foregrounds in projected kSZ velocity reconstruction

Carmen Embil Villagra, Fiona McCarthy, Antón Baleato Lizancos et al. (+2 more)

The kSZ effect has recently emerged as a powerful probe for precision cosmology through its ability to reconstruct the large-scale velocity field. In particular, the kSZ-reconstructed velocity-galaxy cross-correlation is sensitive to signatures of primordial non-Gaussianity through its imprint on the galaxy bias. The kSZ velocity reconstruction is performed using small-scale information from CMB temperature and galaxy overdensities. As the sensitivity of these measurements improves, systematic effects such as extragalactic foreground contamination present in CMB maps become increasingly important. We present a study of foreground biases to the kSZ-reconstructed velocity-galaxy cross-correlation. We derive the relevant foreground contributions from the thermal Sunyaev-Zel'dovich effect and the cosmic infrared background, modeling them using a halo model description of the dominant one- and two-halo terms. We compare our analytic predictions to measurements obtained using ACT DR6 temperature maps and DESI Legacy Imaging Survey galaxies, finding qualitative agreement. We introduce a parity-odd estimator constructed from antisymmetric combinations of tomographic velocity-galaxy correlations and show analytically that, under the Limber approximation, this estimator entirely cancels the foreground contamination while preserving the full cosmological signal without loss of signal-to-noise. Finally, we apply this parity-odd estimator to the data combination mentioned above and show that the fit to the velocity-galaxy correlation is dramatically improved compared to the analysis without mitigation; our estimator detects the signal at 11$\sigma$, with an amplitude consistent with recent studies.
Read the full abstract

All authors Carmen Embil Villagra, Fiona McCarthy, Antón Baleato Lizancos, Blake D. Sherwin, Anthony Challinor

Instrumentation and Methods for Astrophysics

SNID-SAGE: A Modern Framework for Interactive Supernova Classification and Spectral Analysis

Fiorenzo Stoppa and Stephen J. Smartt

We present SNID-SAGE (SuperNova IDentification-Spectral Analysis and Guided Exploration), a framework for supernova spectral classification with both a fully interactive graphical interface and a scriptable command-line pipeline for large-scale processing. The pipeline combines deterministic spectral preprocessing, FFT-based cross-correlation against a curated template library, ranking of candidate matches using a composite quality metric, and consolidation of redshift and classification solutions into a single result with associated quality and confidence estimates. SNID-SAGE includes an upgradeable template library (about 6000 spectra), interactive line identification with velocity measurements, and optional natural-language summaries of classification results. We evaluate SNID-SAGE using two complementary tests: (i) leave-one-out cross-validation, in which each template spectrum is matched against the remainder of the library; and (ii) large-scale application to WISeREP spectra with valid coverage across the 4000-7000 A interval, irrespective of spectral type, comprising approximately 46 000 spectra, with redshift validation against known host-galaxy measurements where available. The full validation results and the SNID-SAGE framework are publicly available, supporting integration into spectroscopic survey workflows.
Read the full abstract

High Energy Astrophysical Phenomena

Can a single supernova remnant account for the gamma-ray emission of G106.3+2.7?

P. Cristofari, G. Emery, T. Lubrano di Vavaria et al. (+4 more)

SNR G106.3+2.7 is a complex TeV emitting source whose emission is still poorly understood. It has especially been at the center of numerous discussions on its potential for being a supernova remnant (SNR) PeVatron, since its gamma-ray spectra seems not to exhibit any significant suppression in the multi–TeV range, up to $\sim 600$ TeV, thereby indicating the presence of $\sim$ PeV particles. We study the hypothesis in which a SNR evolving in a clumpy or cloudy environment is powering the TeV gamma-ray emission, detected mainly from two regions, the "head" and the "tail". We discuss the implications of such an hypothesis. We rely on a simple physically motivated analytical modeling of the shock dynamics and of the content of accelerated particles and confront it to available gamma-ray observations. We find that the current observed TeV gamma-ray emission in the head and tail regions can be accounted for by an active single SNR, with a natural hardening of the spectrum due to the expansion in a clumpy medium or escaping to a dense region in the tail. However, in all scenarios, the broadband gamma-ray emission from the GeV range to the $\gtrsim 100$ TeV range is difficult to reconcile with a standard SNR - whether originating from a thermonuclear or a core-collapse supernova - and instead points toward an association with the pulsar.
Read the full abstract

All authors P. Cristofari, G. Emery, T. Lubrano di Vavaria, H. Costantini, F. Cassol, M.-S. Carrasco, B. Le Nagat Neher

High Energy Astrophysical Phenomena

An Intertwined Short and Long GRB with 4-minute Separation

Liang Li, Yu Wang, Bing Zhang et al. (+19 more)

Gamma-ray bursts (GRBs), the most energetic transients in the Universe, are traditionally classified into long-duration ($T_{90}>2$ s) and short-duration ($T_{90}<2$ s) events, associated with the core collapse of massive stars (Type II) and the merger of compact binary systems (Type I), respectively. The two classes exhibit distinct observational properties that serve as key diagnostic criteria for classification. Here we report GRB 160425A, a peculiar event comprising two sub-bursts separated by four minutes: a short-duration burst ($G_1$) and a long-duration burst ($G_2$). Nearly all standard prompt-emission diagnostics, including pulse morphology, duration, hardness ratio, minimum variability timescale, spectral properties, and established empirical correlations, consistently categorize $G_1$ as a short-like (Type I, merger-origin) and $G_2$ as a long-like (Type II, collapsar-origin) GRB. The coexistence of merger and collapsar signatures in a single event challenges existing progenitor frameworks and calls for a re-evaluation of GRB classification schemes and progenitor scenarios.
Read the full abstract

All authors Liang Li, Yu Wang, Bing Zhang, Ye Li, Shu-Rui Zhang, Jochen Greiner, Zhi-Ping Jin, Jin-Jun Geng, Hou-Jun Lv, Asaf Peer, Maria Dainotti, Tong Liu, Yi-Zhong Fan, Yong-Feng Huang, Zi-Gao Dai, Melin Kole, Wei-Hua Lei, Ye-Fei Yuan, Shuang-Nan Zhang, Felix Ryde, She-Sheng Xue, Rong-Gen Cai

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

Probing soft signals of gravitational-wave memory with space-based interferometers

Yan Cao, Yong-Liang Ma and Yong Tang

Gravitational-wave displacement memory is a remarkable, ubiquitous prediction of general relativity that has not yet been detected. Unlike the oscillatory components of gravitational waveforms, displacement memory is associated with soft gravitons and provides the leading low-frequency observable of its parent event. Analogous soft signals may also be associated with velocity and integrated-displacement memory. The simple, universal spectral shapes of soft waveforms provide effective templates for matched filtering and parameter estimation. In this paper, we investigate the detection prospects for such soft memory signals with future space-based laser interferometers. As realistic examples, we examine the infrared spectral features of gravitational waves from moderately relativistic nonspinning compact binary scattering and comparable-mass quasi-circular, nonprecessing black hole mergers. In both cases, the low-frequency spectrum can be described by a soft displacement-memory waveform with finite-frequency corrections. Using the adopted instrumental-noise models, simulated Bayesian parameter-estimation analyses show that a single LISA-like detector can constrain the memory amplitude and arrival time for signals with matched-filter signal-to-noise ratios of order 10. BBO Stage 1 could measure null displacement memory from sufficiently loud stellar-mass compact binary mergers. We also evaluate the detectability of an idealized stochastic background of soft displacement-memory signals. These results establish gravitational-wave bursts with memory as concrete targets for space-based interferometers.
Read the full abstract

Solar and Stellar Astrophysics

Finding the elusive RR Lyrae companions via speckle imaging

R. Salinas, V. Kalari, G. Hajdu et al. (+25 more)

Despite their key role in astrophysics, the binary properties of RR Lyrae stars (RRL) remain almost completely unknown since only a single RRL is confirmed as belonging to a binary system. Finding companions to RRL is difficult since most of them will be at wider orbits, given that close orbits will likely ensue mass transfer disrupting the conditions to develop stellar pulsations. These wide orbits open the possibility that RRL companions may be more easily found by high-resolution imaging. We observed 81 RRL with the speckle interferometers Zorro and 'Alopeke at the Gemini telescopes, reaching the diffraction limit of $\sim$20 mas of these 8m-class telescopes, and therefore exploring a new parameter space around RRL. We have detected 10 newly identified companions around these 81 RRL, with projected separations between 20 AU to 220 AU. An analysis of the field contamination shows that all of these detected companions are most likely gravitationally bound binaries. From these observations we can estimate an RRL binary fraction higher than 12%, ruling out a binary fraction higher than 25% at the 99% confidence level. These numbers are significantly more elevated than previous estimations which were close to a binary fraction of only 1%, albeit derived with methods exploring a different parameter space. For RRL with thin disc kinematics, we find that the binary fraction is significantly lower, at around 6%, with a single thin disc RRL having a companion out of the 16 observed. The nature of the companions, found to be stars in the lower red giant branch and upper main sequence, is also studied via the measurement of the minimum light colors of the RRL, which appears as a useful method for the search and analysis of RRL in binary systems.
Read the full abstract

All authors R. Salinas, V. Kalari, G. Hajdu, Z. Prudil, C. Sáez-Carvajal, W. Narloch, M. Catelan, S.B. Howell, K. Bąkowska, R. Chini, C. Gałan, M. Górski, M. Kałuszyński, P. Karczmarek, M. Kicia, W. Kiviaho, K. Kotysz, F. Marcadon, D. Moździerski, H. Netzel, G. Pietrzyński, W. Pych, M. Radziwonowicz, P. Romaniuk, R. Smolec, P. Wielgórski, B. Zgirski, P. Żuk

Astrophysics of Galaxies

How Overmassive Black Holes Formed at Cosmic Dawn

Muhammad A. Latif, Daniel J. Whalen, Sadegh Khochfar et al. (+1 more)

Overmassive black hole galaxies (OBGs) at redshifts $z \sim$ 10, or 450 Myr after the Big Bang, are one of the most puzzling discoveries by the James Webb Space Telescope to date because they formed by such early epochs and their black-hole to stellar mass ratios are a hundred times higher than those in galaxies today. Here we show that OBGs are simply the result of DCBH birth in primordial halos at early times. A 70,000 M$_{\odot}$ DCBH forming at $z =$ 25.7 in our cosmological simulation grows at about half the Eddington rate to $6.0 \times 10^6$ M$_{\odot}$ by $z =$ 10.1. Its host galaxy reaches a stellar mass of $4 \times 10^8$ M$_{\odot}$, a metallicity $Z =$ 0.1 Z$_{\odot}$, a star formation rate of 2 M$_{\odot}$ yr$^{-1}$, and $M_{\rm BH}/M_{\ast}$ $\sim$ 0.01, on par with OBGs like GN-z11, UHZ1, and GHZ9 at $z =$ 10.6, 10.1, and 10.2, respectively. Our simulation, the first to follow the coevolution of a DCBH and its host galaxy for several hundred Myr, shows that this ratio is a natural result of initial suppression of star formation by the DCBH and the later, violent blowout of metals by Pop III supernovae. Our models provide an excellent match to the spectra of UHZ1 and GHZ9 at $z =$ 10.1 and 10.4, respectively.
Read the full abstract

All authors Muhammad A. Latif, Daniel J. Whalen, Sadegh Khochfar, Fergus Cullen

High Energy Astrophysical Phenomena

Variable ADAF disk as the origin of Changing-Look AGN

Chun Xu

We propose that changing-look AGN transitions arise from variations in the size of the inner ADAF disk. The AGN accretion disk consists of an outer thin disk and an inner thick ADAF component, whose size is intrinsically unstable and evolves over time. The size variations of the ADAF are governed by a parameter \eta, which represents the turbulence strength within the accretion flow. \eta also determines the accretion rate onto the central black hole and controls jet formation and outflow rate, with the latter regulating the line-of-sight absorption. From the perspective of a variable ADAF, changing-state and changing-observation AGN are two sides of the same coin. We further discuss gigahertz-peaked and compact steep-spectrum radio sources as possible manifestations of intermediate-to-large scale ADAFs. Finally, we propose that AGN unification models should include both orientation and ADAF size as key parameters.
Read the full abstract

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

Removing the Cosmological Bound on the Axion Scale via Confinement During Inflation

Gia Dvali, Sophia Fitz and Lucy Komisel

We implement the scenario of early relaxation of the axion via a high scale confinement within $SU(5)$ grand unified theory and study an epoch of strong QCD in inflationary cosmology. We consider scenarios in which, during inflation, the $SU(5)$ is either entirely or partially in the confining phase. This generates an early potential for the axion and dilutes its energy density removing any cosmological upper bound on the decay constant. We show that a phase of strong QCD can be realized by at least two mechanisms: 1) A direct coupling between the inflaton and the gauge fields and/or 2) by restoration of the $SU(5)$ symmetry during the inflationary epoch. In the latter case, strong coupling is already achieved via the RG running of the $SU(5)$ gauge coupling. We show that the mechanism works for all known realizations of the invisible axion idea: Peccei-Quinn (PQ) type formulations in which the anomalous global symmetry is realized via additional scalars (DFSZ) or heavy fermions (KSVZ) as well as the two-form gauge axion formulation based entirely on the QCD gauge redundancy without any anomalous global symmetry. Even if the expectation value of the PQ scalar vanishes during inflation, the axion is a well defined degree of freedom represented by the phase of the fermion 't Hooft determinant. For the DFSZ case, this phase is composed out of a condensate of the ordinary quarks, amounting to an early universe version of the $\eta'$-meson. In all considered scenarios, the present day axion can be a viable dark matter candidate for an arbitrarily large value of the decay constant.
Read the full abstract

Solar and Stellar Astrophysics

Small-scale impulsive EUV emission enhancements along network loops

A. Dolliou, H. Peter, S. Mandal et al. (+4 more)

Network loops are a common feature in the quiet Sun. The physical processes sustaining their energy budget is still under discussion. We rely on a multi-instrumental (Solar Orbiter/EUI, Solar Orbiter/PHI, IRIS) observation of a six hours quiet Sun region to measure the dynamics and the possible magnetic drivers of impulsive EUV emission enhancements along network loops. We report the detection of small-scale impulsive EUV emission enhancements with EUI/HRIEUV in three network loops. We selected four EUV emission enhancements to measure their plane-of-sky velocities in HRIEUV; their Doppler velocities in the line (log Si iv T = 4.8) with IRIS ; their possible relation to small-scale flux emergence and fluctuation in one of the loop footpoint. The plane-of-sky velocities of the four EUV emission enhancements have a component that seem to appear almost instantaneously along the loop (more than 220 km/s) ; and two of them had a co-temporal component with a PoS velocity of up to , starting near one of the loop footpoint. In one case, we measured with IRIS a co-temporal intensity increase in the line associated with Doppler velocities down to and up to along the line of sight. Finally, we found evidence of small-scale (8E16 Mx) mixed polarity field emergence and fluctuation near one of the loop footpoint. We concluded that the fast component on the plane-of-sky are consistent with a thermal transfer or supersonic plasma flows, while the slower component is consistent with plasma flows. A possible physical origin for these EUV emission enhancements would be magnetic reconnection driven by either photospheric motion of the loop footpoints or by the reconnection of the loop with small-scale magnetic bipoles.
Read the full abstract

All authors A. Dolliou, H. Peter, S. Mandal, L. P. Chitta, L. Teriaca, Y. Chen, D. Calchetti

Solar and Stellar Astrophysics

Interpretative Modeling of Structured Winds Using Linear Polarization

R Ignace

Polarization provides additional diagnostic opportunities for probing the structured environments of massive stars as well as the illumination of those environments by stars that are not spherical. After a brief overview of polarization considerations relevant to hot massive stars, selected applications are presented. Examples related to dense Wolf-Rayet winds are chosen: clumpy wind flow, co-rotating interaction regions, and colliding wind interactions. Brief remarks are given about the prospects for opening a new window on massive star studies using UV spectropolarimetry with the Polstar mission concept.
Read the full abstract

Astrophysics of Galaxies

Euclid Quick Data Release (Q1). The Strong Lensing Discovery Engine F – Bright and low-redshift strong lenses

Euclid Collaboration: L. R. Ecker, M. Fabricius, S. Seitz et al. (+345 more)

We present 72 additional galaxy-galaxy strong lenses that complement the sample discovered in the Euclid Quick Release 1 data (63.1 deg^2) of the Strong Lens Discovery Engine (SLDE) papers A-E. It is shown that previous pre-selection of potential lenses, which excluded objects from the Gaia catalogue, led to missing several bright and low-redshift strong lenses, adding more than 10% new strong lens candidates compared to the previous search. In total, the catalogue includes 38 "grade A" (confident) and 34 "grade B" (probable) candidates. These lenses are identified through a combination of two independent searches for bright nearby objects: one based on machine-learning models followed by expert visual inspection, and the other based solely on expert visual inspection, targeting objects not included in the initial machine-learning selection (a limitation identified only after extensive visual inspection). With these additional strong lens candidates, we augment the expected number of high-confidence candidates in the Euclid Wide Survey from previous forecasts to 120000. Detailed semi-automated lens modelling confirms at least 41 systems out of 72, a fraction consistent with that found in SLDE A (315 out of 488). These include: multiple edge-on disc lenses; sources with arcs near the lens centre; "red sources"; and an edge-on disk galaxy lensing a galaxy merger, producing two sets of lensed features, an Einstein ring and a doubly imaged component. The median redshift of these systems is $\Delta$ z ~ 0.3 lower than that of the SLDE A sample.
Read the full abstract

All authors Euclid Collaboration: L. R. Ecker, M. Fabricius, S. Seitz, R. Saglia, N. E. P. Lines, P. Holloway, T. Li, A. Verma, F. Balzer, Q. Jin, A. Manjón-García, S. H. Vincken, J. Wilde, J. A. Acevedo Barroso, J. W. Nightingale, K. Rojas, S. Schuldt, M. Walmsley, T. E. Collett, G. Despali, A. Sonnenfeld, C. Tortora, R. B. Metcalf, R. Bender, C. Saulder, E. Baeten, C. Cornen, D. Delley, K. Finner, A. Galan, R. Gavazzi, L. C. Johnson, L. Leuzzi, C. Macmillan, P. J. Marshall, M. Millon, A. More, L. A. Moustakas, J. Pearson, J.-N. Pippert, C. Scarlata, D. Sluse, C. Spiniello, T. T. Thai, L. Ulivi, Han. Wang, X. Xu, F. Courbin, M. Meneghetti, N. Aghanim, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, F. Dubath, X. Dupac, S. Dusini, A. Ealet, S. Escoffier, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, W. Gillard, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, D. Le Mignant, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, Y. Mellier, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, H.-W. Rix, E. Romelli, M. Roncarelli, E. Rossetti, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, S. Serrano, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, M. Ballardini, M. Bolzonella, E. Bozzo, C. Burigana, R. Cabanac, A. Cappi, T. Castro, B. Clément, J. A. Escartin Vigo, L. Gabarra, J. García-Bellido, V. Gautard, S. Hemmati, M. Huertas-Company, J. Macias-Perez, R. Maoli, J. Martín-Fleitas, M. Maturi, N. Mauri, P. Monaco, A. Pezzotta, M. Pöntinen, C. Porciani, I. Risso, 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, P. Bergamini, D. Bertacca, M. Bethermin, F. Beutler, A. Blanchard, L. Blot, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, Y. Charles, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, P.-A. Duc, V. Duret, M. Y. Elkhashab, A. Enia, Y. Fang, A. Finoguenov, A. Fontana, A. Franco, K. Ganga, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, H. Hildebrandt, J. Hjorth, L. K. Hunt, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, M. Lattanzi, L. Legrand, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, A. Loureiro, M. Magliocchetti, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, C. Moretti, G. Morgante, K. Naidoo, P. Natoli, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, G. Rodighiero, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, A. Venhola, D. Vergani, G. Vernardos, G. Verza, P. Vielzeuf, S. Vinciguerra, N. A. Walton, A. H. Wright

High Energy Astrophysical Phenomena

Comprehensive Measurement of Spectral Evolution in a GRB Flare: High Time-Resolution Insights into the "Double-Tracking" Phenomenon

Zheng-Hang Yu, Wen-Jun Tan, Chen-Wei Wang et al. (+41 more)

The spectral evolution characteristics of the prompt emission in gamma-ray bursts (GRBs) have been extensively studied, but detailed investigations of spectral evolution in a GRB flare remain lacking. In this work, we present the first analysis of spectral parameter evolution in a GRB flare through high time-resolved spectral fitting of the Brightest Flare in GRB 221009A. We find that the $\alpha$-Flux, $E_p$-Flux, and $E_p$-$\alpha$ relationships during both the overall phase and the rise phase of flare can be well described by simple power-law model, showing positive correlations. Therefore, we conclude that Brightest Flare exhibits "Double-tracking" behavior. Since values of $\alpha$ do not exceed the synchrotron "death line" (-2/3), we explain this phenomenon using a magnetic dissipation synchrotron radiation model. In the decay phase of flare, the $E_p$-Flux and $E_p$-$\alpha$ correlations become notably flatter, with their power-law indices decreasing significantly compared to those in the rise phase. This may be due to the fact that the next flare begins to erupt before the Brightest Flare has completely ended, resulting in the combined effects of both two flares. Our study of spectral parameter relations of the Brightest Flare provides new insights into the radiation mechanisms of both GRB prompt emission and flares.
Read the full abstract

All authors Zheng-Hang Yu, Wen-Jun Tan, Chen-Wei Wang, Shao-Lin Xiong, Chao Zheng, Peng Zhang, Hao-Xuan Guo, Zheng-Hua An, Ce Cai, Min Gao, Ke Gong, Dong-Ya Guo, Yue Huang, Bing Li, Cheng-Kui Li, Xiao-Bo Li, Xin-Qiao Li, Jia-Cong Liu, Ya-Qing Liu, Xiao-Jing Liu, Xiang Ma, Wen-Xi Peng, Rui Qiao, Yang-Zhao Ren, Li-Ming Song, Jin Wang, Jin-Zhou Wang, Ping Wang, Yue Wang, Xiang-Yang Wen, Shuo Xiao, Sheng-Lun Xie, Wang-Chen Xue, Sheng Yang, Shu-Xu Yi, Da-Li Zhang, Fan Zhang, Zhen Zhang, Xiao-Yun Zhao, Jin-Peng Zhang, Wen-Long Zhang, Yan-Qiu Zhang, Shuang-Nan Zhang, Shi-Jie Zheng

High Energy Astrophysical Phenomena

Search for TeV emission from spider millisecond pulsars with HAWC

R. Alfaro, E. Anita-Rangel, M. Araya et al. (+90 more)

Millisecond pulsars (MSPs) are observed to emit multi-wavelength radiation, from radio to GeV. Spider MSPs, which interact with their low-mass companion in close orbit (orbital periods $< 1$ day), may lead to strong intrabinary shocks that can further accelerate electron and positron pairs produced in the magnetosphere, possibly emitting very-high-energy (0.1–100 TeV; VHE) photons through inverse Compton scattering. Using 2565 days of HAWC Pass 5 data, we search for VHE emission from spider MSPs and present upper limits on individual sources. We also perform a stacking analysis to examine whether the two sets of spider systems, classified as redbacks and black widows depending on the companion mass, exhibit different spectral properties. Our study places constraints on TeV emission from MSPs and suggests that they are unlikely to contribute significantly to the Galactic diffuse emission at TeV and higher energies.
Read the full abstract

All authors R. Alfaro, E. Anita-Rangel, M. Araya, J.C. Arteaga-Velázquez, D. Avila Rojas, H.A. Ayala Solares, R. Babu, P. Bangale, E. Belmont-Moreno, A. Bernal, F. Calore, T. Capistrán, A. Carramiñana, S. Casanova, A.L. Colmenero-Cesar, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, P. Desiati, N. Di Lalla, R. Diaz Hernandez, M.A. DuVernois, J.C. Díaz-Vélez, K. Engel, T. Ergin, C. Espinoza, K. Fang, N. Fraija, S. Fraija, J.A. García-González, F. Garfias, A. Galván-Gámez, N. Ghosh, A. Gonzalez Muñoz, M.M. González, J.A. González, J.A. Goodman, S. Groetsch, D. Guevel, J. Gyeong, J.P. Harding, S. Hernández-Cadena, I. Herzog, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, S. Kaufmann, D. Kieda, K. Leavitt, W.H. Lee, H. León Vargas, A.L. Longinotti, G. Luis-Raya, K. Malone, S. Manconi, O. Martinez, J. Martínez-Castro, J.A. Matthews, P. Miranda-Romagnoli, J.A. Morales-Soto, M. Mostafá, M. Najafi, L. Nellen, R. Noriega-Papaqui, N. Omodei, M. Osorio-Archila, E. Ponce, Y. Pérez Araujo, C.D. Rho, A. Rodriguez Parra, D. Rosa-González, M. Roth, H. Salazar, A. Sandoval, M. Schneider, J. Serna-Franco, M. Shin, Y. Son, R.W. Springer, O. Tibolla, K. Tollefson, I. Torres, F. Ureña-Mena, E. Varela, X. Wang, Z. Wang, H. Wu, S. Yu, X. Zhang, H. Zhou, C. de León

Solar and Stellar Astrophysics

JW-VL: A Vision-Language Model for Solar Physics

Mingfu Shao, Hui Wang, Liyue Tong et al. (+7 more)

Vision-Language Models (VLMs) have achieved breakthrough progress in general knowledge domains, yet adaptation to specialized scientific fields remains challenging due to multimodal representation shifts and the limited integration of domain-specific knowledge. To address the limitations of general-purpose VLMs when applied to solar physics image recognition, analysis, and reasoning, we propose JinWu Vision-Language (JW-VL), a fine-tuned foundation model tailored for solar physics. The model integrates multi-wavelength observational data from both space-based and ground-based telescopes, encompassing representative spectral bands spanning the photosphere, chromosphere, and corona. Built upon a cross-modal alignment knowledge distillation framework, JW-VL learns a joint visual-semantic embedding that enables end-to-end modeling from raw solar observational data to downstream tasks, including solar image recognition, solar activity analysis via image-based question answering, and optical character recognition (OCR), while also supporting the construction of a multi-band, cross-instrument solar image benchmark dataset. Furthermore, as a demonstration of interdisciplinary applicability, we developed a "Daily Solar Activity Reports" agent comprising core modules for solar activity level assessment, significant active region characterization, magnetic field complexity analysis, potential space weather impact assessment, and identifying active regions for targeted observation. While JW-VL may not yet meet the rigorous, high-precision demands of operational solar physics, it bridges raw observations and diverse downstream tasks, establishing a valuable methodological framework for applying multimodal deep learning to the field.
Read the full abstract

All authors Mingfu Shao, Hui Wang, Liyue Tong, Yuyang Li, Cunshi Wang, Jiaben Lin, Suo Liu, Haiqing Xu, Yin Zhang, Jing Huang

Astrophysics of Galaxies

Andromeda XXXVI: discovery of a new ultra-faint dwarf galaxy towards M31

Joanna D. Sakowska, David Martínez-Delgado, Michelle L. M. Collins et al. (+4 more)

We present deep imaging of Andromeda XXXVI (And XXXVI), a dwarf galaxy discovered through visual inspection of the Pan-Andromeda Archaeological Survey, using observations obtained with the OSIRIS+GTC instrument. The colour-magnitude diagram of And XXXVI shows a well-defined red giant branch (RGB). However, constraining a distance is challenging because the tip of the RGB is sparsely populated and no horizontal branch stars are found. The RGB is nevertheless well matched by an old (12.5 Gyr), metal-poor ([Fe/H]= - 2.5) isochrone shifted to the distance of Andromeda (776 kpc). With a projected distance of 119 kpc from M31, And XXXVI is therefore likely a satellite of Andromeda. With MV -5.9 +-0.1, half-light radius rh 64 +30-19 pc, and an ellipticity 0.015 +0.032-0.012, And XXXVI is one of the faintest of ultra-faint M31 dwarfs discovered to date. The discovery of And XXXVI adds to the faint end of M31's satellite luminosity function, suggesting the presence of an even larger population of very faint satellites. Deeper space-based imaging and/or spectroscopic observations are needed to better constrain its position within M31's halo. Combined with a detailed star formation history, such data would help determine whether its old, metal-poor stellar population indicates early quenching, similar to the trends seen in Milky Way satellites, and whether And XXXVI could be considered a reionisation fossil.
Read the full abstract

All authors Joanna D. Sakowska, David Martínez-Delgado, Michelle L. M. Collins, Matteo Monelli, Giuseppe Donatiello, Amandine Doliva-Dolinsky, Isabel M. E. Santos-Santos

Solar and Stellar Astrophysics

Period-Luminosity Relations, projection factor and radii of Anomalous Cepheids

Piotr Wielgórski, Grzegorz Pietrzyński, Wolfgang Gieren et al. (+24 more)

Anomalous Cepheids are radially pulsating stars observed in dwarf galaxies, the Galactic bulge and halo, and globular clusters. Similarly to other radially pulsating stars, they can be used as distance indicators through their Period-Luminosity Relations (PLRs) and the geometrical Baade-Wesselink (BW) method. We aim to calibrate the zero-point of the distance scale of Anomalous Cepheids using nearby representatives of this class of pulsating stars. We collected optical and near-infrared photometry and spectra for a sample of nearby Anomalous Cepheids with twotelescopes located at the Rolf Chini Cerro Murphy Observatory and optical telescopes offered by the Las Cumbres Observatory, and with instruments hosted and operated by the European Southern Observatory. Using parallaxesmeasured by the Gaia space mission and mean magnitudes from our new photometry, we calibrate the zero-point of the PLRs in Johnson B, V, 2MASS J, H, KS , and Pan-STARRS g, r, i passbands and selected Wesenheit indices. Using the surface brightness-colour relation version of the BW technique, we also determined the projection factors and mean radii of three nearby Anomalous Cepheids. Precision of the measured zero-points is at the level of 0.04-0.05mag and their systematic uncertainty is estimated to about 0.1mag. We used our zero-points and literature photometry of the Large Magellanic Cloud Anomalous Cepheids to measure the distance modulus of this galaxy and obtained a value of 18.454$\pm$0.045(statistical) mag, in a very good agreement with the most accurate value from eclipsing binaries. The obtained projection factors are 1.38$\pm$0.13, 1.59$\pm$0.21 and 1.35$\pm$0.14 for V716 Oph, XX Vir and UY Eri, respectively. The radii measured for V716 Oph and UY Eri are in agreement with the period-radius relation obtained from the Large Magellanic Cloud Anomalous Cepheids.
Read the full abstract

All authors Piotr Wielgórski, Grzegorz Pietrzyński, Wolfgang Gieren, Bartlomiej Zgirski, Weronika Narloch, Gergely Hajdu, Jesper Storm, Nicolas Nardetto, Pierre Kervella, Bogumił Pilecki, Marek Górski, Radosław Smolec, Ricardo Salinas, Dariusz Graczyk, Vincent Hocdé, Paulina Karczmarek, Monica Taormina, Wojciech Pych, Henryka Netzel, Rolf Chini, Klaus Hodapp, Mikołaj Kałuszyński, Francisco Pozo Nuñez, Krzysztof Kotysz, Dawid Moździerski, Przemysław Mikołajczyk, Piotr Kołaczek-Szymański

Solar and Stellar Astrophysics

Solar energetic particles and their association with radio emissions

Diana E. Morosan, Anshu Kumari, Immanuel Jebaraj et al. (+6 more)

Energetic particle populations are ubiquitous throughout the Universe. In our solar system, the most prominent sources of energetic particles are solar flares or collisionless shocks often driven by huge eruptions of magnetised plasma called coronal mass ejections (CMEs). Remotely, low energy electrons from the Sun can be observed as solar radio bursts that are produced by accelerated electron beams undergoing beam-plasma interactions. There are still many open questions on the generation of solar energetic particles (SEP): how and where are SEPs accelerated during solar flares and CMEs and how they escape the solar atmosphere? Another important question is: what is the link between the solar radio bursts and the observed SEPs at spacecraft? SKA can provide high-resolution radio images combined with spectroscopic observations to determine the acceleration time, trajectory and escape of low energy electrons from the solar corona. The synergy between SKA and current space missions will help investigate solar activity and energetic particles across a wide range of wavelengths and particle energies. Particle data from spacecraft can be used to make a connection between radio bursts and SEPs by comparing SEP inferred injection times and energies to those of electrons generating radio bursts at the Sun. Radio observations in turn can be used to distinguish between flare and shock acceleration since different radio bursts pinpoint towards different energetic processes. Since the acceleration region and origin of SEPs of various properties is still largely debated, radio observations have the potential to be an invaluable tool in unraveling these processes.
Read the full abstract

All authors Diana E. Morosan, Anshu Kumari, Immanuel Jebaraj, Eduard P. Kontar, Mugundhan V., Ketaki Deshpande, Nina Dresing, Puja Majee, Divya Paliwal

Earth and Planetary Astrophysics

A break in planet occurrence near the pebble isolation mass should be observable by the Roman microlensing survey

Claudia Danti, Michiel Lambrechts and Hannah Diamond-Lowe

Microlensing detections are uniquely well-suited to probing the population of planets outside the water iceline, down to planetary masses comparable to the Earth. Here, we perform 1D pebble-accretion population synthesis simulations to explore a sample of iceline planets around stars with masses and metallicities similar to the target population of the Galactic Bulge Time-domain microlensing survey of the Nancy Grace Roman Space Telescope. We find that the planet distribution in the microlensing sensitivity space deviates from a log-uniform distribution in mass and orbital radius. When planetary core growth comes to a halt as planets reach the pebble isolation mass, $M_{\mathrm{iso}}$, the combined effects of planetary migration and runaway gas accretion create an occurrence break. Our simulations highlight that, between 1 and 50 AU, the fraction of stars hosting isolation-mass planets (1 to 5 $M_{\mathrm{iso}}$) is lower by a factor 20 compared to less massive planets (0.2 to 1 $M_{\mathrm{iso}}$). If this break in planetary occurrence rates around the pebble isolation mass is detected in future lensing surveys, it would further validate the core accretion paradigm for giant planet formation.
Read the full abstract

Astrophysics of Galaxies

Star Formation Beyond the Optical Disk : The Low-Density Outskirts of NGC2090

Jyoti Yadav, Mousumi Das, S Amrutha et al. (+1 more)

We present a far-ultraviolet (FUV) analysis of the star-forming complexes (SFCs) in the nearby spiral galaxy NGC\,2090, based on observations from the Ultraviolet Imaging Telescope (UVIT), and compare it with emission from the optical and infrared bands. NGC\,2090 exhibits prominent star formation in its extended outer disk, with FUV emission traced out to $\sim$30 kpc, far beyond the truncation of the old stellar disk at $\sim$5 kpc. It is classified as an extended UV (XUV) disk galaxy. We identify and characterize the SFCs both within and beyond the optical radius (R$_{25}$), estimating their physical sizes and star formation rates (SFRs). The outer-disk SFCs are generally smaller in area and show a narrower distribution of SFR surface density ($\Sigma_{\mathrm{SFR}}$) compared to the inner-disk SFCs. We investigate the properties of the inner disk using mid-infrared data from the James Webb Space Telescope (JWST), and find that the polycyclic aromatic hydrocarbon (PAH) emission is strongly correlated with regions of active star formation. The specific SFR (sSFR) increases with radius, consistent with a scenario of inside-out disk growth. The observed number of SFCs and their H$\alpha$-to-FUV flux ratios in the outer disk of NGC\,2090 indicate ongoing massive star formation and are consistent with a top-heavy IMF, implying that the upper end of the IMF is not truncated in the low-density, metal-poor outskirts. These results suggest that XUV disks can host significant massive star formation despite their low stellar density and metallicity.
Read the full abstract

All authors Jyoti Yadav, Mousumi Das, S Amrutha, Dimitra Rigopoulou

Cosmology and Nongalactic Astrophysics

Investigating the $H_0$ Tension and Expansion-History Mismatch with Diverse Dark Energy Parametrization Frameworks

Upala Mukhopadhyay, Purba Mukherjee and Alexandre Tkatchenko

In this work, we investigate whether the mismatch between early- and late-Universe inferences of the cosmic expansion history is associated with a particular redshift range, and whether models that alleviate the $H_0$ tension also provide a consistent description of $H(z)$ across cosmic time. We consider four late-time cosmological frameworks: $\Lambda$CDM, a dark energy (DE) equation-of-state parametrization, a DE pressure parametrization, and a generalized scale-factor parametrization. Using Planck CMB data as an early-Universe anchor and Pantheon+ with SH0ES calibration as a late-Universe probe, together with DESI DR2 BAO measurements, we first assess the $H_0$ tension in each framework and then reconstruct the expansion history through $H(z)$. We further compare these parametric reconstructions with non-parametric reconstruction employing Gaussian process regression. We find that the expansion histories inferred within $\Lambda$CDM remain significantly discrepant over the full redshift range considered, whereas the alternative phenomenological parametrizations largely localize the mismatch to lower redshifts. Among these models, the pressure parametrization gives the strongest reduction of the $H_0$ tension, to approximately $2.6\sigma$, while still exhibiting significant discrepancies in the reconstructed $H(z)$ at intermediate redshifts. Both the parametric and model-independent reconstructions identify the strongest deviations around $z=0.51$ and $z=0.706$ consistently, indicating robust late-time tensions in the cosmic expansion rate.
Read the full abstract

Solar and Stellar Astrophysics · Cross-listed from nucl-th

Study of radiative proton capture by the 7Be nucleus with the use of ab initio approaches

D. Rodkin and Yu. Tchuvilsky

A theoretical study of the 7Be(p,gamma)8B reaction in the astrophysical energy range with the use of ab initio methods is presented. The used approaches are No-Core Shell Model and Cluster Channels Orthogonal Functions Method. The scheme also contains elements of R-matrix theory and procedures for extrapolating various data obtained in ab initio computations. The developed approach as a whole allows one not only to calculate the astrophysical S-factor and all nuclear characteristics that determine its value, but also to evaluate the reliability of the obtained results and to identify the dominant reaction mechanisms against a background of insignificant ones.The high accuracy of the obtained results and has been demonstrated.
Read the full abstract

High Energy Astrophysical Phenomena

Evolution of Quasi-Periodic Eruptions in the post-TDE Accretion Disk Perturbed by an Orbiting Star

Martin Mondek, Michal Zajaček, Henry Best et al. (+3 more)

Quasi-periodic eruptions (QPEs) are a recently discovered class of highly variable X-ray bursts originating in galactic nuclei. These high-amplitude bursts exhibit periodicity ranging from tens of minutes to several days. QPEs are also characterized by variable peak amplitudes that can vary by a factor of few. While multiple physical models have been proposed to explain QPE light curves, none can fully account for all the observed features. A possible connection between QPEs and tidal disruption events (TDEs) has been suggested, particularly due to the past optical/UV outbursts that can be traced back for several sources, the long-term decay in the continuum luminosity, and the soft, thermal-dominated X-ray spectrum. Our primary goal is to verify whether the long-term decrease in eruption amplitudes detected for some QPE sources is consistent with the accretion disk being formed following a TDE. In this work, we adopt a simplified extreme mass ratio inspiral (EMRI) scenario, where a Solar-type star orbits a supermassive black hole (SMBH) and collides with an accretion disk twice per orbit, generating eruptions. We assume a post-TDE disk that follows a temporal power-law decline in mass accretion ($\propto t^{-p}$, $p>0$). As our aim is to develop a toy-model scenario, we have used purely analytical methods without considering all intervening processes in their full generality. Indications are that (i) the observed long-term decline in QPE amplitudes can be reproduced if the first monitored epoch occurs years to a few decades after the tidal disruption, (ii) stellar mass loss caused by ablation can play an important role in the evolution of QPE amplitudes in systems with heavy main-sequence (MS) stars.
Read the full abstract

All authors Martin Mondek, Michal Zajaček, Henry Best, Taj Jankovič, Vladimír Karas, Petr Kurfürst

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

Cosmological peculiar velocities in general relativity?

Christos G. Tsagas

Cosmological peculiar velocities have traditionally been studied within the framework of Newtonian theory. Around the turn of the century, a few quasi-Newtonian analyses appeared in the literature, but led to equations and results identical to those of the purely Newtonian approach [1]. More recently, a series of studies introduced a relativistic treatment of the peculiar-velocity problem, criticising the quasi-Newtonian approach as effectively Newtonian in nature [2]. These works also reported a linear growth-rate of $v \propto t$ for peculiar velocities, in contrast to the slower Newtonian/quasi-Newtonian scaling of $v \propto t^{1/3}$. In a manuscript uploaded to the archives a few days ago [3], the authors defended their earlier quasi-Newtonian work and criticised the more recent relativistic treatments. However, the limitations of the quasi-Newtonian approach are not a new concern, but they have been noted at least since [4]. There, it was clearly stated that the quasi-Newtonian approximation leads to Newtonian-like equations and results, and readers were cautioned against applying it to large-scale cosmological studies. Given that one of the authors of [3] was also a coauthor of [4], the self-contradiction is evident. The relativistic analyses have, in fact, confirmed the concerns of [4], clarified the underlying issues and shown how they can be resolved. Motivated by [3], we present a critical comparison of the two approaches and in the process identify several internal inconsistencies in that manuscript.
Read the full abstract

Astrophysics of Galaxies

A Black Hole Star at Cosmic Noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick winds in a Little Red Dot at z=1.7

Alberto Torralba, Jorryt Matthee, Andrea Weibel et al. (+12 more)

Recent studies at high redshift have revealed an enigmatic class of Little Red Dots (LRDs) with extreme Balmer breaks, stronger than in any stellar atmosphere. However, it is unclear whether such objects exist at lower redshift, especially given the low number of LRDs reported at $z\lesssim 2$. Here we report the discovery of PAN-BH*-1, an LRD with an extreme Balmer break at $z=1.73$, identified from JWST/NIRCam pure-parallel imaging taken by the PANORAMIC survey, and confirmed by deep VLT/X-Shooter spectroscopy. The rest-optical to near-infrared spectral energy distribution of PAN-BH*-1 is consistent with a photospheric continuum with effective temperature $T_{\rm eff}\approx 4800$ K. The broad H$\alpha$ emission line shows remarkably deep absorption, stronger than previously measured in any LRD. The absorption trough spans from $-520$ km/s to $+267$ km/s with respect to the systemic redshift. The presence of blue- and red-shifted absorption suggests complex dynamics of the obscuring gas along the line of sight. We speculate that the absorption trough can be produced by a thick wind launched from a thick, rotating photospheric disk, the latter being the source of the red optical continuum. While the source is unresolved in the rest-optical JWST data ($r_{\rm eff,UV}<47$ pc), the rest-NUV HST imaging shows an extended morphology with $r_{\rm eff,opt}=1.0^{+0.5}_{-0.3}$ kpc, that we interpret as a host galaxy with a stellar mass $\sim 10^8$ $M_\odot$, in line with the narrow H$\alpha$ emission. The discovery of this object at cosmic noon highlights the feasibility of systematic searches for extreme LRDs with wide-area facilities such as Euclid and Roman.
Read the full abstract

All authors Alberto Torralba, Jorryt Matthee, Andrea Weibel, Rohan P. Naidu, Yilun Ma, Aidan P. Cloonan, Aayush Desai, Anna de Graaff, Jenny E. Greene, Christian Kragh Jespersen, Ivan G. Kramarenko, Sara Mascia, Pascal A. Oesch, Wendy Q. Sun, Christina C. Williams

Earth and Planetary Astrophysics

Mass determination of the ultra-short-period planet LHS 3844 b. First K-band radial velocity measurements with CRIRES+

E. Nagel, J. Köhler, M. Zechmeister et al. (+21 more)

We present the first planet mass measurement obtained with CRIRES+ radial velocity (RV) observations using the K-band gas cell. Our target, LHS 3844 b (TOI-136), is a transiting super-Earth with radius $R_b=1.286^{+0.043}_{-0.044}R_\oplus$ and an orbital period of $P_b = 0.462929709^{+0.000000044}_{-0.000000042}$d, placing it in the class of ultra-short-period (USP) planets. The host star LHS 3844 is an old ($7.8\pm1.6$Gyr), slowly rotating ($P_{rot} = 130.0^{+16.9}_{-13.4}$d) M5.0 dwarf with $M_\star = 0.151\pm0.014M_\odot$ at a distance of 15pc (V=15.2mag, K=9.2mag). Combining our CRIRES+ RVs with archival ESPRESSO spectra, and confirming the signal in each dataset independently, we detected periodic RV variations with a semi-amplitude $K_b=6.95^{+0.55}_{-0.60}$m/s, implying a planetary mass of $m_b = 2.37\pm0.25M_\oplus$ and a bulk density of $\rho_b = 6.15^{+0.60}_{-0.61}$gcm$^{-3}$, consistent with a predominantly rocky composition. We further found excess RV variability that may be attributed to stellar jitter or to an additional planetary signal, for which we identified a tentative super-Earth candidate with a period of $\approx6.88$d. Owing to its proximity to its M-dwarf host, LHS 3844 b experiences intense irradiation and is unlikely to retain a substantial H/He envelope. Interior modeling places an upper limit on the iron-core mass fraction, which is consistent with an Earth-like rocky composition. With an emission spectroscopy metric of 28, LHS 3844 b is a prime JWST target for atmospheric and surface characterization and the most promising surface-characterization target known. Phase-curve spectroscopy may reveal its surface mineralogy and enable the first robust detection of exoplanet surface spectral features. Our results demonstrate that near-infrared RVs obtained with CRIRES+ enable robust mass measurements of super-Earths orbiting late M dwarfs.
Read the full abstract

All authors E. Nagel, J. Köhler, M. Zechmeister, A. D. Rains, U. Seemann, A. Hatzes, A. Reiners, N. Piskunov, L. Boldt-Christmas, P. Bristow, P. Chaturvedi, D. Cont, S. Czesla, R. J. Dorn, E. Guenther, Y. Jung, O. Kochukhov, F. Lesjak, F. Lucertini, T. Marquart, L. Nortmann, M. Rengel, F. Rodler, J. V. Smoker

Earth and Planetary Astrophysics

Weighing the mass of LHS 3844 b

Alejandro Hacker, Nicola Astudillo-Defru, Rodrigo F. Díaz et al. (+7 more)

Context: LHS 3844 b (TOI-136 b) is a ultra short-period, Earth-size exoplanet detected by TESS. It is one of the most favourable object for atmospheric characterisation and the study of its surface with the James Webb Space Telescope. However, the dynamical mass of this planet has not been measured yet. Aims: We aim to determine the mass of LHS 3844 b using high-precision radial velocity (RV) measurements and assess the robustness of the inferred signal across different noise and orbital modelling assumptions. Methods: We analyse 25 ESPRESSO RV observations within a fully Bayesian framework. We explore 15 competing RV models that differ in their treatment of correlated stellar variability (through different Gaussian Process kernels) and long-term drifts. Marginal likelihoods are computed for all models and used for Bayesian model comparison and evidence-weighted parameter estimation. Results: The RV planetary signal is robustly detected across all models, and the inferred semi-amplitude remains stable under all tested noise and drift prescriptions. From the evidence-weighted posterior samples we derive a planetary mass of $2.27 \pm 0.23$ M$_\oplus$ and a bulk density of $5.67 \pm 0.65$ gcm$^{-3}$, consistent with a predominantly rocky composition. Model comparison favours GP kernels including periodic or quasi-periodic components associated with stellar rotation and disfavors models with additional long-term drifts. Using interior-structure inference, we find that the core mass fraction is comparable to (or slightly smaller than) Earth's and only trace amounts of water are permitted, supporting a dry, terrestrial interior. We also investigate a tentative additional signal near $\sim 6.9$ days, but Bayesian model comparison does not provide conclusive support for its planetary interpretation.
Read the full abstract

All authors Alejandro Hacker, Nicola Astudillo-Defru, Rodrigo F. Díaz, Caroline Dorn, Xavier Bonfils, José M. Almenara, Pía Cortés-Zuleta, Xavier Delfosse, Thierry Forveille, Stephane Udry