Instrumentation and Methods for Astrophysics
On-sky demonstration of a vector Zernike wavefront sensor in a cascaded adaptive optics system
M. Motte, V. Chambouleyron, R. Fétick et al. (+13 more)
To directly image and characterise Earth-like
exoplanets, future high-contrast instruments will require adaptive-optics systems operating at increasingly high loop frequencies to reduce temporal errors. Increasing the loop frequency reduces the signal-to-noise ratio per wavefront-sensor frame, making highly sensitive wavefront sensors, such as the Zernike wavefront sensor (ZWFS), attractive candidates. However, the limited dynamic range of the classical ZWFS makes on-sky operation challenging. We therefore investigate whether a ZWFS can be used as a second-stage sensor in an on-sky cascaded adaptive-optics system. To this end, we added a second AO stage, called OZIRIIS, to the PAPYRUS platform at the Observatoire de Haute-Provence. OZIRIIS combines a vector Zernike wavefront sensor (v-ZWFS) with a 97-actuator deformable mirror operating at 400 Hz downstream of the pyramid-based first AO stage. Real-time control relied on a single ZWFS signal, while the full v-ZWFS was used a posteriori for non-linear reconstruction and telemetry analysis. The second-stage correction increased the measured Strehl ratio by up to 16 percentage points. Analysis of the telemetry using the full v-ZWFS to reconstruct residuals revealed optical-gain effects affecting the ZWFS at low Strehl ratio. The good agreement between on-sky measurements and numerical simulations further supports the calibration strategy based on synthetic reference signals and interaction
matrices. These results demonstrate that Zernike wavefront sensing can be operated in closed loop on sky and support its use in future cascaded extreme adaptive-optics systems.
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All authors M. Motte, V. Chambouleyron, R. Fétick, F. Oyarzun, M. A. Alagao, A. Striffling, E. Vinerskas, J.-F. Sauvage, C. T. Héritier, E. Muslimov, M. Cissé, A. Rahim, J. Kent Wallace, T. Wenger, B. Neichel, T. Fusco
Solar and Stellar Astrophysics
Astrometric modeling of unresolved variable binary systems. II. Application to Gaia epoch astrometry of nearby pulsating and convective red giants
L. Decin, K. Sivkova, P. Kervella et al. (+2 more)
(Abbreviated) The interpretation of high-precision astrometry for intrinsically variable
stars remains challenging, particularly for unresolved binary systems containing asymptotic giant branch (AGB)
stars. In such systems, large-amplitude pulsations and evolving convective surface structures induce time-dependent photocentre displacements that perturb the observed orbital motion. At the same time, Gaia DR4 epoch astrometry offers the prospect of deriving accurate orbital solutions and parallaxes for nearby unresolved AGB binaries. Building upon the variability-induced mover (VIM) framework, we extend the astrometric model for unresolved evolved binaries by combining Keplerian photocentre motion, pulsation-induced flux-dependent photocentre shifts, and convection-induced photocentre motion. In the forward simulations, convection is represented either by
stochastic photocentre displacements drawn from an exponential correlation function or by photocentre time series extracted from 3D radiation-hydrodynamic simulations. We then test a
retrieval framework that fits the orbital and VIM signal while incorporating a red-noise covariance
matrix to account for correlated astrometric residuals produced by convection. We show that Gaia epoch astrometry can recover reliable orbital and astrometric parameters for unresolved AGB binaries despite strong pulsation- and convection-induced photocentre variability. Pulsation-induced variability produces a coherent VIM signal that can be modeled jointly with the Keplerian photocentre orbit, while convection-induced photocentre motion behaves primarily as temporally correlated astrometric noise.
Retrievals that ignore this correlated component lead to biased proper motions and parallaxes, whereas the inclusion of a physically motivated red-noise covariance model enables accurate recovery of the underlying orbital solution and astrometric parameters.
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All authors L. Decin, K. Sivkova, P. Kervella, A. Chiavassa, E. Beguin
Cosmology and Nongalactic Astrophysics
Not all those missing are lost: leveraging galaxy clustering in incomplete catalogs to unleash dark sirens cosmology
Riccardo Barbieri, Marios Kalomenopoulos, Matteo Tagliazucchi et al. (+2 more)
Gravitational waves offer a unique opportunity to solve the Hubble tension. In order to do so, we have to extract as much information as possible from cross correlating gravitational wave events (used as "dark sirens") with incomplete
galaxy catalogs. Traditional methods assume a uniform in comoving volume distribution for
galaxies missing from the catalogs, which neglects the fact that
galaxies tend to cluster, leading to less precise and possibly biased posteriors. In this paper, we introduce a new method for accounting for
galaxy clustering when dealing with an incomplete
galaxy catalog, by adding back
galaxies to the incomplete catalog and distributing them in pixels according to the correlation function $\xi(r)$. We find that our method drastically improves on traditional ones when the
galaxy catalog is only $1\%-10\%$ complete, leading to posteriors that are between 2 and 4 times as precise, depending on the completeness fraction, without introducing any biases. Our method produces results comparable to traditional methods at extremely low catalog completeness fractions (<0.5%) or for very high uncertainties in the recovered luminosity distance and sky localization of the gravitational wave events.
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All authors Riccardo Barbieri, Marios Kalomenopoulos, Matteo Tagliazucchi, Jonathan Gair, Sadegh Khochfar
High Energy Astrophysical Phenomena
TeV Gamma Rays and Neutrinos from Winds Driven by Radiatively Inefficient Accretion Flows of Low-Luminosity Active Galactic Nuclei
Nobuyuki Sakai, John F. Beacom and Kohta Murase
Recently, the Large High Altitude Air Shower Observatory (LHAASO) reported the first TeV gamma-ray detection from a low-luminosity active galactic
nucleus (LLAGN) lacking a strong jet. This source, NGC 4278, is one of the nearest LLAGNs that can be studied in detail as a template for more distant objects. Most previous studies have focused on the month-scale-variable gamma-ray activities, seeking to explain them with weak jets. We focus instead on NGC 4278's quiet-period emission, proposing a different mechanism based on a wind launched from a radiatively inefficient
accretion flow (RIAF). In particular, we model particle acceleration at a wind-driven shock and calculate the resulting multimessenger emission. To match the TeV gamma-ray fluxes reported by LHAASO in the quiet period, our model requires a wind power of $\lesssim2\times10^{43}~\mathrm{erg~s^{-1}}$ with a spectral index of injected
cosmic rays of 2.0. We show that this is achievable through Bondi
accretion of the ionized gas observed on the 100-pc scale, for a shallow
accretion profile. We discuss the testability of our wind-driven shock scenario with multimessenger observations. As another important application, we extend our model to Sgr A*, the nearest LLAGN, and show that its TeV gamma-ray emission is reproduced with reasonable parameters. Our results suggest that RIAF-driven winds may be a generic emission mechanism in LLAGNs, making this class a potentially important population of both gamma-ray emitters and
cosmic-ray accelerators.
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Instrumentation and Methods for Astrophysics
Learning Radio Astronomical Representations with LeJEPA and Very Small Models
Erica Lastufka, Mariia Drozdova, Vitaliy Kinakh et al. (+4 more)
Representations learned by
vision foundation models pretrained on natural images have been shown to be useful for out-of-domain astronomical images. Performance on scientific downstream tasks increases with model size, which both carries higher inference costs and limits scalability, even when considering parameter-efficient adaptation. An alternative is to learn representations directly from astronomical observations rather than natural images, through self-supervised pretraining. We evaluate LeJEPA's ability to learn robust representations using very small
vision models ($\sim$6M parameters) pretrained on
Radio Galaxy Zoo images, comparing with established self-supervised frameworks. We test whether LeJEPA's latent-space regularization leads to better
radio galaxy morphology classification. Across three evaluation
datasets, LeJEPA achieves performance comparable to a substantially larger foundation model while producing more consistent representations across training and evaluation
datasets. These results suggest that the choice of representation learning objective is critical for enabling small domain-specific models to achieve performance competitive with representations transferred from large foundation models in scientific imaging.
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All authors Erica Lastufka, Mariia Drozdova, Vitaliy Kinakh, Taras Holotyak, Miroslava Dessuages-Zavadsky, Daniel Schaerer, Svyatoslav Voloshynovskiy
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
NS-UNO: Neutron Star EoS Inference from an Unconstrained Number of Observations
Valéria Carvalho, Márcio Ferreira, Michał Bejger et al. (+1 more)
Future multimessenger observations of
neutron stars (NS) are expected to substantially increase both the number and precision of astrophysical constraints on the equation of state (EoS) of dense matter. This motivates inference frameworks capable of accommodating a variable, non fixed number of observations while preserving the posterior information associated with each measurement. In this work, we introduce NS-UNO, a Neural Posterior Estimation framework for NS EoS inference designed to accommodate an Unconstrained Number of Observations (UNO). NS-UNO combines a hierarchical DeepSets model with a conditional normalising flow, enabling a single trained model to perform inference from mass-radius observation sets of varying size, with each observation represented by a set of posterior samples. We demonstrate accurate and well calibrated posterior reconstructions using a model trained jointly on piecewise polytropic and non-parametric Gaussian process EoS ensembles. The reconstruction improves as observations probe a broader range of NS masses, while remaining robust to variations in the number and precision of the observations. The model also generalises to EoSs outside the families used during training. Finally, we qualitatively demonstrate the framework on current multimessenger constraints from NICER and GW170817. NS-UNO provides a flexible and scalable approach to NS EoS inference, naturally suited to the increasingly diverse observational
datasets expected from next generation multimessenger astronomy.
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All authors Valéria Carvalho, Márcio Ferreira, Michał Bejger, Constança Providência
High Energy Astrophysical Phenomena
Cascades from ultra-high-energy neutrinos
Gaetano Di Marco, Rhorry Gauld, Rafael Alves Batista et al. (+2 more)
Neutrinos produced at the highest energies can interact with
cosmic neutrino and radiation backgrounds during their propagation to Earth. The many available $\nu\nu$, $\nu\bar{\nu}$, and $\nu\gamma$ channels can lead to their absorption or energy redistribution, whilst the leptonic and hadronic final states may feed secondary fluxes of
neutrinos,
protons, and electromagnetic particles through the decay or hadronisation of the heavy leptons,
bosons, and
quarks produced. We present a framework to characterise these propagation effects in detail, \texttt{$\nu$propa}, an extension of the CRPropa Monte Carlo code that interfaces with event generators and to dedicated computations of the relevant cross sections. It also treats flavour oscillations in
vacuum. Using this code, we investigate sources at high
redshifts ($z = 10$), and find a strong absorption of the
prompt flux beyond~$\sim 10^{21} \; \text{eV}$, although the copious secondary
neutrinos partially compensate this depletion, also contributing to the spectrum at lower energies. The framework is designed to study scenarios of cosmological
neutrino production beyond~EeV energies such as superheavy dark matter,
cosmic strings, and primordial black holes, and to yield reliable predictions for the forthcoming
neutrino observatories.
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All authors Gaetano Di Marco, Rhorry Gauld, Rafael Alves Batista, Alfonso García-Soto, Miguel Á. Sánchez-Conde
Solar and Stellar Astrophysics
Interferometric Survey of Stellar Parameters: Towards homogeneous FGK stars parameters and surface-brightness color relation in the context of PLATO space mission
Romina V. Ibañez Bustos, Denis Mourard, Nicolas Nardetto et al. (+20 more)
The estimation of stellar angular diameters can be performed from the surface brightness - color relation (SBCR) and photometry. The SBCR have been considered by the PLATO space mission as an independent empirical alternative for estimating stellar radii of FGK
stars. In this context, we have implemented an homogeneous approach not only for calibrating the SBCR for FGK-IV/V
stars but, also for determining their fundamental parameters in order to place the
stars reliably on the HR diagram and to study their impact on the SBCR. We have performed interferometric observations of 18 quiescent FGK-IV/V
stars in the Gaia color range of $3.088 \leq G \leq 5.498$. For the first time, we used 3 different interferometers operating in the $R$, $H$ , and $K$ bands to measure polychromatic limb-darkened angular diameters (LDAD). In parallel, by using public domain spectra we have estimated the stellar parameters ($T_{eff}$, $log g$ and Z) by using the open python tool iSpec. We achieved an average accuracy of 2.3% for the LDAD based on polychromatic observations. However, we have observed that our SBCR does not follow the calibration of the relation between surface brightness and color in Gaia found in the literature. Furthermore, we found that $log g$ and $Z$ have no impact on the SBC relation; given the characteristics of our sample of quiescent
stars, it constitutes an ideal set of targets for conducting a new SBCR calibration within the framework of the PLATO space mission. In this context, we reported a SBCR calibration with $\sigma_{RMS} = $ 0.012, 0.009, 0.009 in the $G, G_{BP}$ and $G_{RP}$ Gaia bands, respectively. This article is part of a series of papers reporting the first results obtained using a polychromatic approach to measure LDAD, employing a fully homogeneous methodology for both determining the fundamental parameters of
stars and measuring the LDAD, $\theta_{LD}$.
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All authors Romina V. Ibañez Bustos, Denis Mourard, Nicolas Nardetto, Jeremy Jones, Nayeem Ebrahimkutty, Juraj Jonák, Hugo Nowacki, Mathieu Vrard, Philippe Berio, Julien Dejonghe, Roxanne Ligi, Frédéric Morand, David Salabert, Orlagh Creevey, Armando Domiciano de Souza, Manon Bailleul, Karine Perraut, Markus Wittkowski, John D. Monnier, Stefan Kraus, Narsireddy Anugu, Mayra Gutierrez, Noura Ibrahim
Solar and Stellar Astrophysics
Joint Observations of PTPS Targets (JOTA). Combined spectroscopic and photometric analysis of 16 SB1 systems
Robert Jaros, Andrzje Niedzielski, Sohaib Ali et al. (+9 more)
Context. The Pennsylvania-Toruń
Planet Search, which operates on a sample of $\sim$1000 northern-hemisphere
stars, has been underway since 2004.
Stars with radial velocity (RV) amplitudes exceeding 2 km s$^{-1}$ represent a backup subprogram sample dedicated to monitoring binary
stars with multiple instruments. Aims. We used almost 21 years of combined RV measurements to search for Doppler signals consistent with stellar or brown dwarf companions and to produce a catalog of both known and previously unpublished binary
stars in our
planet-search sample. Methods. We analyzed the combined RV measurements, searching for stellar companions and obtaining orbital solutions for both known and new binary systems. We also searched for periods in available long-term photometric monitoring data from All Sky Automated Survey (ASAS), and applied Gaia astrometric data whenever available. Results. We report the results of long-term RV monitoring of 16 systems: new detections of low-mass companions to 11
stars and updated orbital elements based on combined sets of our new and literature data for five systems. For two objects (TYC 3318-00789-1 and TYC 3318-01538-1), we find evidence of activity or the influence of another unseen companion, possibly due to line-profile variations or unresolved spectral contamination. We present true masses for three systems in our sample: TYC 1931-1040-1, TYC 3451- 1449-1, and TYC 3667-1636-1. We obtained these masses using Gaia DR3 non-single
star data.
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All authors Robert Jaros, Andrzje Niedzielski, Sohaib Ali, Divyansh Srivastava, Julia Sierzputowska, Monika Adamów, Jorge Lillo-Box, Dmytro Orikhovskyi, Aleksander Wolszczan, Eva Villaver, Theodor Pribulla, Martin Vaňko
Solar and Stellar Astrophysics
Equilibrium \(\mathrm{H}_2^+/\mathrm{H}^-\) Abundance Ratios in MARCS Atmosphere Models
Aiganym Sarsembayeva and Hernando Quevedo
We investigate the
equilibrium abundance ratio of the molecular hydrogen ion \(\mathrm{H}_2^+\) and the negative hydrogen ion \(\mathrm{H}^-\) in stellar atmospheres using compact Saha-type
equilibrium expressions and layer-by-layer partial pressures from MARCS model atmospheres. The analysis distinguishes the temperature-dependent coefficient ratio \(K_{\mathrm{H}_2^+}(T)/K_{\mathrm{H}^-}(T)\) from the full abundance ratio, which also depends on the local ionisation factor \(N_{\mathrm{H}^+}/N_e\). The internal partition function \(Z_{\mathrm{H}_2^+}(T)\) is included in the \(\mathrm{H}_2^+\)
equilibrium coefficient. We processed \(51{,}994\) MARCS models, corresponding to \(2{,}911{,}664\) atmospheric layers, and computed \(N(\mathrm{H}_2^+)/N(\mathrm{H}^-)\) directly from the tabulated
equilibrium partial pressures, constructing the first systematic map of this ratio across the MARCS grid. \(\mathrm{H}_2^+\) exceeds \(\mathrm{H}^-\) in \(827{,}350\) layers, corresponding to \(F=0.284\), or \(28.4\%\) of all analysed layers. Although \(\mathrm{H}^-\) remains dominant in the global logarithmic mean, with \(\langle \log_{10}[N(\mathrm{H}_2^+)/N(\mathrm{H}^-)] \rangle=-4.229\), \(\mathrm{H}_2^+\) becomes comparable to or more abundant than \(\mathrm{H}^-\) in a substantial subset of layers. Its relative significance increases toward higher \(T_{\mathrm{eff}}\), lower \([\mathrm{Fe}/\mathrm{H}]\), and deeper layers. The balance is therefore controlled by the combined local thermodynamic and ionisation structure, not by temperature alone. These ratios are
equilibrium abundance diagnostics and do not imply opacity dominance; assessing opacity requires wavelength-dependent cross-sections and radiative-transfer calculations.
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Instrumentation and Methods for Astrophysics
DINOspec: Efficient Multimodal Alignment of Vision and Spectral Foundation Models for Astronomy
Erica Lastufka, Mariia Drozdova, Daniel Schaerer et al. (+1 more)
Astronomical observations provide
multimodal views of physical systems, with images and spectra capturing complementary properties of celestial objects. Scientific foundation models can learn powerful representations from these observations, but representations learned by separate models remain difficult to combine. We investigate whether physical representations learned by separate
vision and spectral models can be aligned without retraining their encoders. We introduce DINOspec, a
multimodal framework that aligns a frozen DINOv3 image encoder with a pre-trained AION-1 spectral tokenizer using lightweight adapters and contrastive learning on 20,472 paired images and spectra of astronomical objects. DINOspec improves
galaxy morphology classification (F1: 0.72$\rightarrow$0.78) and spectral classification (F1: 0.70$\rightarrow$0.74) while training at most 21M parameters. Improvements depend on the downstream task, revealing asymmetric transfer between independently learned representations, while spectroscopic
redshift prediction remains unchanged ($R^2\approx0.9$). These results demonstrate that scientific foundation models can be composed through lightweight representation
alignment.
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All authors Erica Lastufka, Mariia Drozdova, Daniel Schaerer, Svyatoslav Voloshynovskiy
Cosmology and Nongalactic Astrophysics
Thermodynamic reconstruction in observationally constrained dynamical dark energy models
Sonej Alam
We perform an observational and thermodynamic analysis of four cosmological models $\Lambda$CDM, CPL, MPL, and the three-parameter MmAH parametrization. All dynamical models improve the fit relative to $\Lambda$CDM, with $\Delta\chi^2 \sim 6$-$6.5$, with MPL providing the best fit, while MmAH remains viable. Although
Bayesian evidence mildly favors $\Lambda$CDM due to its lower complexity, the dynamical dark energy models remain competitive alternatives given current observations. We then reconstruct thermodynamic quantities within observationally constrained cosmological models, extending previous theoretical studies. The bestfit heat capacity reconstruction indicates that the divergence associated with a second order thermodynamic phase transition coincides with the deceleration-acceleration transition only in $\Lambda$CDM, whereas for the dynamical dark energy models it occurs at distinct
redshifts, suggesting that this coincidence is not universal. The generalized second law is satisfied for all models over $0 \le z \le 1$, while the Hessian analysis reveals a transient instability at the phase transition; however, the late time thermodynamic stability is model dependent, with CPL and MPL remaining stable and $\Lambda$CDM and MmAH failing to satisfy both stability conditions simultaneously. These results show that thermodynamic properties reconstructed within observationally constrained cosmological models provide a complementary probe of dark energy, with the thermodynamic phase transition emerging as an intrinsically model dependent phenomenon.
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Astrophysics of Galaxies
Photometric redshifts for active galactic nuclei with LePHARE for the Vera C. Rubin Observatory
R. Shirley, M. Salvato, J. Cohen-Tanugi et al. (+31 more)
Active Galactic
Nuclei (AGN) play a crucial role in
galaxy evolution, but they are a minority of extragalactic sources with diverse Spectral Energy Distributions (SEDs), which depend on their means of selection. Upcoming large-scale surveys such as LSST will identify many AGN, but analysis tools are not optimized for them. The limited number of photometric bands in these surveys impacts the calculation of photometric
redshifts for AGN, which are essential for scientific advancement. We use LePHARE to demonstrate the impact that a limited number of bands and erroneous assumptions have on the determination of the photometric
redshifts of AGN. We conduct tests on six AGN samples selected using X-ray,
radio, infrared, variability, color, and spectroscopic criteria in the COSMOS field, using photometry from HSC-CLAUDS, which is closest in depth and wavelength coverage to LSST. We present the LSST pipeline for LePHARE within the
Redshift Assessment Infrastructure Layers (RAIL), facilitating comparison between SED fitting and machine learning
algorithms. AGN that appear as point-like sources in optical data will be assigned highly unreliable photometric
redshifts if they are processed using
galaxy templates. Additionally, shallow all-sky surveys (like eROSITA, WISE, and ZTF) miss many AGN. As a result, these "hidden" AGN are often misidentified as
galaxies in public survey data, leading to incorrect photometric
redshift. We provide the configurations that are suggested for each type of AGN alongside measures of expected performance as a function of
redshift, magnitude, and selection. To facilitate studies with a panchromatic view of AGN, we also release photometric
redshifts and posterior distributions for all AGN sources identified in the COSMOS field using the six criteria, based on 28-band photometry.
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All authors R. Shirley, M. Salvato, J. Cohen-Tanugi, O. Ilbert, S. Arnouts, R. Ansari, R. Assef, M. Banerji, A. Bongiorno, W. N. Brandt, J. Buchner, J. Comparat, D. Ilić, A. Kovačević, J. Kubica, B. Laloux, O. Lynn, A. Malz, L. Marchetti, C. Mazzucchelli, T. Mkrtchyan, K. Nandra, D. Oldag, C. Ricci, W. Roster, E. Saremi, S. Satheesh-Sheeba, T. Tasnim. Ananna, M. J. Temple, M. Vaccari, A. Viitanen, C. Wolf, Z. Yu, T. Zhang
High Energy Astrophysical Phenomena
ALMA Observations of DEM L241/LMC P3 in the Large Magellanic Cloud: Evidence for the Formation of Cool Molecular Jets Driven by a Microquasar
Yasuo Fukui, Bhuvana G. R., Hidetoshi Sano et al. (+17 more)
We present ALMA observations of DEML 241/LMC P3, the most luminous $\gamma$-ray binary consisting of a compact object and an O
star, in CO emission. We have found an one-sided jet-like CO feature of 8 pc length and 1 pc width, which accompanies another weaker CO jet candidate with slightly different orientation. The one-sided CO jet exhibits striking
alignment with LMC P3, suggesting that the jet was driven by LMC P3. We have determined kinetic temperature of the CO jet to be significantly high at 33$-$60 K as compared with $\sim$15 K in the nearby non-jet CO cloud whereas no radiative heat source is found. We interpret that the high temperatures are due to shock heating of a microquasar jet driven by the $\gamma$-ray binary, where the compact object has an
accretion disk fed by the O
star winds. The CO jet matches existing predictions from magneto-hydrodynamical simulations, which show that CO jet can form from the interaction of the microquasar jet and an ambient ISM cloud. These results provide strong evidence that CO jets are a signature sculptured by microquasar jets, lending support for mass
accretion in LMC P3 as the $\gamma$-ray origin. The results suggest a second case of CO jets potentially driven by a microquasar along with the CO jets in the microquasar candidate HESS J1023-575 recently identified in the Milky Way. Further, our results suggest the use of sub-mm observations for identifying microquasars, opening a new possible window for their discovery and study.
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All authors Yasuo Fukui, Bhuvana G. R., Hidetoshi Sano, Kisetsu Tsuge, Rami Z. E. Alsaberi, Rin Yamada, Yuya Asano, Aya Bamba, Miroslav Filipovic, Charles Law, Norikazu Mizuno, Toshikazu Onishi, Paul Plucinsky, Gavin Rowell, Manami Sasaki, Piyush Sharda, Hiromasa Suzuki, Kengo Tachihara, Kazuki Tokuda, Yumiko Yamane
Solar and Stellar Astrophysics
Phosphorus abundances and multi-element co-enrichment in nearby FGK stars
Dario Esposito, Giovanni Covone, Donato Giovannelli et al. (+9 more)
The distribution of bio-essential elements is key to assessing the chemical fertility of galactic environments. We analyse phosphorus abundances for 233 nearby FGK
stars from the Hypatia Catalog, separating thin- and thick-disk populations. We study [P/Fe] as a function of [Fe/H] and other elemental abundances using non-parametric tests and bootstrap resampling, and we examine residual correlations at fixed [Fe/H] together with molar ratios involving P. We find a [P/Fe]-[Fe/H] trend broadly similar to that of alpha elements, supporting a dominant origin in core-collapse
supernovae, while deviations point to additional nucleosynthetic channels. Phosphorus shows strong positive correlations with several CHNOPS, alpha, and Fe-peak elements, especially in the thin disk. These co-enrichment patterns remain significant at fixed [Fe/H], indicating that they are not a trivial consequence of global
metallicity. Thin-disk
stars are also more enriched than thick-disk
stars in many elements. The solar P/Mg and P/Si ratios are representative of the local stellar population, whereas solar P/O is relatively elevated. Overall, phosphorus emerges as a tracer of genuine multi-element co-enrichment and of the chemical fertility of the solar neighbourhood.
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All authors Dario Esposito, Giovanni Covone, Donato Giovannelli, Paola Manini, Christian Magliano, Laura Inno, Luca Cacciapuoti, Víctor M. Rivilla, Vito Saggese, Leonardo Testi, Emanuele Cristiano, Luca Tonietti
High Energy Astrophysical Phenomena
SNAD: enabling discovery in the era of big data
Maria Pruzhinskaya, Emille E. O. Ishida, Konstantin Malanchev et al. (+8 more)
In the era of wide-field surveys and big data in astronomy, the SNAD team is exploiting the potential of modern
datasets for discovering new, unforeseen, or rare astrophysical objects and phenomena with machine learning (ML). The SNAD pipeline was built under the hypothesis that, although automatic ML
algorithms have a crucial role to play in this task, the scientific discovery is only completely realized when such systems are designed to boost the impact of domain knowledge experts. Our key contributions include the development of the Coniferest Python library, which offers implementations of two active learning
algorithms with an “expert in loop”, and the creation of the SNAD Transient Miner, facilitating the search for specific types of transients. We have also developed the SNAD Viewer, a web portal that provides a centralized view of individual objects from the Zwicky Transient Facility's (ZTF) data releases, making the analysis of potential anomalies more efficient. Finally, when applied to ZTF data, our approach has resulted in more than a hundred new
supernova (SN) candidates, along with a few other non-catalogued objects, such as red dwarf
flares, superluminous SNe, RS CVn type variables, and young stellar objects.
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All authors Maria Pruzhinskaya, Emille E. O. Ishida, Konstantin Malanchev, Anastasia Lavrukhina, Etienne Russeil, Timofey Semenikhin, Sreevarsha Sreejith, Emmanuel Gangler, Matwey Kornilov, Vladimir Korolev, Alina Volnova
Astrophysics of Galaxies
Broad-band host measurements of little red dots and similar compact nuclei require source-conditioned polychromatic PSFs
Sergio Bonaque-González
Characterizing compact sources in the early Universe is difficult because light from physically distinct components can overlap within the same diffraction-limited image. A common method uses field
stars to model how a single point of light appears and from this estimates the intrinsic structure and contributions of the physical components of the distant object under study. Many important properties inferred for high-
redshift objects depend on the accuracy of this method. Using the little red dots (LRDs) analysed by Zhang et al. as a test case, this work shows that applying the method through broad filters to objects whose spectra differ from those of the field
stars can systematically misassign light, overestimating an existing extended component or creating an apparent one where none exists. At the measured level, this error is large enough to alter the inferred sizes, luminosities and masses, and therefore the physical interpretation of these systems. The physical and mathematical origin of the error is established and a correction applicable to other compact distant sources is demonstrated.
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Earth and Planetary Astrophysics
Planar Three-Body Problem: theoretical predictions and simulation results
Yogesh Dandekar, Ethan Springer, Shoval Zard et al. (+3 more)
We investigate the statistical properties of the non-hierarchical planar three-body problem, relevant to astrophysical systems with nearly planar dynamics, including protoplanetary disks and AGN disks. Using the Flux-based statistical theory of the three-body problem, previously studied in three dimensions, we derive theoretical predictions for several statistical observables in the planar case. Focusing on ergodic disintegration outcomes, we compare these predictions directly with numerical simulations and contrast the results with the corresponding unconstrained three-dimensional case. Our analysis is based on one million simulations for each of eight distinct mass sets. We examine escape probabilities, properties of marginal escape events, eccentricity distributions, lifetime distributions, and relative prevalence of prograde and retrograde escapes. While several of the theoretical predictions are in good agreement with the simulations, others exhibit unexpected discrepancies. We discuss possible explanations for these deviations.
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All authors Yogesh Dandekar, Ethan Springer, Shoval Zard, Alessandro Alberto Trani, Barak Kol, Ofek Birnholtz
High Energy Astrophysical Phenomena
Hunting the nature of the Seyfert 1 galaxy GRS 1734-292: can it be a gamma-ray emitter?
Luigi Foschini
It has been proposed that the
radio-weak Seyfert
galaxy GRS 1734-292 is the counterpart of 3EG J1736-2908 and of the nearby Fermi/LAT source. I examine this identification, considering that the
radio weakness could result from free-free absorption of a relativistic jet. An association with the EGRET detections is plausible, whereas the latest Fermi/LAT localization no longer favors GRS 1734-292. New observations, especially at
radio frequencies of tens of GHz, would help to settle the issue.
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Astrophysics of Galaxies
Testing SALT Approximations with Numerical Radiative Transfer Code. II. Thermal and Microturbulent Line Broadening
Cody Carr, Renyue Cen, Leo Michel-Dansac et al. (+2 more)
Forward models that connect galactic winds to their predicted spectral-line profiles have proved effective for inferring wind properties in controlled settings, but important limitations remain. In particular, many models rely on the Sobolev approximation to solve the radiative transfer equation and neglect line broadening caused by thermal and turbulent motions within the wind. In the first paper of this series, we demonstrated that neglecting this broadening in Semi-Analytical Line Transfer (SALT) models can bias the recovery of fundamental wind properties from mock observations. Here, we extend the SALT framework to incorporate this motion by solving the radiative transfer equation in the single-scattering limit. We treat re-emission using an escape-probability approach similar to that adopted under the Sobolev approximation, while allowing
photons to escape from resonance regions of finite thickness. We validate the model and investigate parameter degeneracies by fitting mock spectra generated with Monte Carlo radiative transfer simulations assuming identical outflow configurations. We identify a degeneracy between the Doppler-broadening parameter and the radial density and velocity profiles: shallower density and velocity gradients can mimic the effects of greater velocity dispersion. Nevertheless, integrated quantities are well recovered. Over the range $13 \leq \log(N_{\mathrm{Si}^+}/\mathrm{cm}^{-2}) \leq 18$, the recovered ionic column densities have a scatter of 0.26 dex and are systematically overestimated by 0.22 dex. Mass-outflow rates evaluated at the terminal wind radius have a scatter of 0.88 dex and are systematically overestimated by 0.51 dex. These results represent substantial improvements over previous versions of the model.
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All authors Cody Carr, Renyue Cen, Leo Michel-Dansac, Claudia Scarlata, Alaina Henry
High Energy Astrophysical Phenomena
SN 2019cqc: A Hydrogen-rich Superluminous Supernova Showing Electron-Scattering Signatures
Dinesh Hebbar, Rupak Roy, Matt Nicholl et al. (+15 more)
Hydrogen-rich superluminous
supernovae without narrow emission lines (SLSNe-II) are rare transients whose powering mechanisms remain debated, particularly the role of circumstellar medium (CSM) interaction. We present photometric and spectroscopic observations of SN 2019cqc to investigate its power source and progenitor mass loss. We model the lightcurve using MOSFiT with the csm and csmni models to constrain the explosion and CSM parameters. SN 2019cqc peaked at $M_g = -20.21 \pm 0.07$ and emitted $\sim 1.7 \times 10^{50}\,\mathrm{erg}$ of energy in the form of radiation. Photometric and spectroscopic modeling indicates that CSM interaction dominates in both scenarios, with best-fit CSM and ejecta masses of $\sim 4.5~ M_\odot$ and $\sim 32~ M_\odot$, respectively. The inferred CSM properties imply an extreme eruptive mass loss at a rate of $\sim 0.2--0.3 ~M_\odot\,\mathrm{yr^{-1}}$ in the years preceding the core collapse, consistent with a variable progenitor of luminous blue variable progenitor. We observe a persistent blueshifted asymmetry in the H$\alpha$ emission line. At early times ($\lesssim +110$~d), this is attributed to electron scattering with bulk Velocity of ejecta, while the profile at late epochs ($\gtrsim +402$~d onward) suggests the subsequent formation of dust in the ejecta. Additionally, we identify a distinct, short-lived feature at $\sim$ 4600 Å , likely a blend of ionized C III/N III lines powered by the interaction of the SN-shock with the extended atmosphere.
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All authors Dinesh Hebbar, Rupak Roy, Matt Nicholl, Jesper Sollerman, Joseph P Anderson, Mariusz Gromadzki, D. Andrew Howell, Tuomas Kangas, Seppo Mattila, Daichi Hiramatsu, Avishay Gal-Yam, Edo Berger, K. Azalee Bostroem, Ting-Wan Chen, Joseph Farah, Sebastian Gomez, Curtis McCully, Jeonghee Rho
Solar and Stellar Astrophysics
Systematic and Statistical Properties of Prominence Eruptions on the M-dwarf YZ CMi
Yuto Kajikiya, Kosuke Namekata, Yuta Notsu et al. (+4 more)
M-dwarfs produce frequent
flares, and their associated mass ejections are expected to significantly affect the habitability of close-in
exoplanets. Recent spectroscopic observations have revealed several prominence eruptions-indicative of stellar mass ejections-on M-dwarfs through Doppler shifts of the H$\alpha$ line. However, systematic and statistical studies, particularly regarding their association with white-light
flares, have been limited due to the lack of intensive and continuous simultaneous photometric and spectroscopic monitoring of the same target
star. We conducted one month of continuous spectroscopic observations of the active M-dwarf YZ CMi using the 3.8-m Seimei
telescope with an unprecedentedly high time cadence of $\sim$1 min, simultaneously with TESS. We detected four prominence eruptions, among which two events showed rapid, short-duration eruptions with velocities of $\sim$300-500 km s$^{-1}$ and durations of $\sim$5 min. Such short-duration events may have been missed in previous observations due to insufficient time cadence. We further performed a systematic analysis using 35 H$\alpha$
flares on YZ CMi observed simultaneously with TESS. Notably, most prominence eruptions (6 out of 7) were not associated with detectable white-light
flares. This result suggests that most observed prominence eruptions on M-dwarfs may have occurred near the stellar limb, where white-light
flares are difficult to detect, which may imply a potential observational bias in their detectability due to low contrast with the background emission. These first statistical constraints, together with the discovery of rapid, short-duration prominence eruptions, indicate that previous observations may have underestimated both the frequency and velocities of mass ejections on M-dwarfs due to observational biases and highlight the necessity of reassessing their impact on close-in
exoplanets.
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All authors Yuto Kajikiya, Kosuke Namekata, Yuta Notsu, Kai Ikuta, Hiroyuki Maehara, Bunei Sato, Daisaku Nogami
Solar and Stellar Astrophysics
OB stars identified in LAMOST Data Release 10
Guang Yang, Zhicun Liu, Xiao-Long Wang et al. (+2 more)
A large sample of OB
stars plays an important role in studying the stellar parameters of massive
stars, as well as the formation and
evolution of the Milky Way. With the help of the Large Sky Area Multi-Object Fiber Spectroscopic
Telescope (LAMOST) Data Release 10 (DR10), we are able to construct a large sample of OB
stars with spectroscopic data. In this study, we identify 48,463 spectra of 34,550 OB
stars from LAMOST DR10, based on the Hertzsprung-Russell (H-R) diagram constructed with Gaia DR3 data and spectral line indices measured from LAMOST DR10 low-resolution spectra. Among these, 6907 OB
stars are newly identified. We use the MKCLASS tool to derive the spectral subtypes of the OB sample. The spatial distribution of 25,287 OB
stars and the Toomre diagram of 20,397 OB
stars indicate that the majority of these
stars are located in the Galactic disk. Based on their peculiar velocities, we identify 1960 runaway
star candidates.
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All authors Guang Yang, Zhicun Liu, Xiao-Long Wang, Yanjun Guo, Wenyuan Cui
Earth and Planetary Astrophysics
Empirical Constraints on the CO Snowline Transition in HD 163296: The Local CO Column and $^{13}$C$^{18}$O Optical Depth
Chunhua Qi, Takahiro Ueda, David J. Wilner et al. (+1 more)
CO isotopologue emission is widely used to infer gas masses and volatile carbon abundances in protoplanetary disks, but converting line emission into a CO column depends on optical depth, temperature structure, linewidth, and isotope ratios. Inferring CO/H$_2$ additionally requires an independent constraint on the local hydrogen column. We use high-resolution $^{13}$C$^{18}$O $2$-$1$ observations of HD 163296 to derive a spatially localized empirical constraint on the CO column at the resolved CO snowline edge. We focus on the 70-75 au annulus, on the inner, high-column side of the observed profile steepening near 75 au. Using RADEX slab calculations conditioned on a two-dimensional temperature structure, we infer an effective beam-averaged CO column from the absolute integrated intensity. Across representative temperatures, isotope-ratio pairs, and effective local linewidths of 0.30 and 0.50 km s$^{-1}$, we find $N_{\rm CO}^{\rm beam}=(1.6-2.4)\times10^{20}$ cm$^{-2}$ and $^{13}$C$^{18}$O line-center optical depths $\tau=0.39-0.97$. Thus, even this rare isotopologue is not safely optically thin at the snowline edge. Adopting $N_{\rm H2}=2.5\times10^{24}$ cm$^{-2}$ from a published parametric gas surface-density profile gives the conditional abundance ${\rm CO/H_2}=(6.4-9.5)\times10^{-5}$. A beam-forward radial-profile analysis gives consistent columns, and a physical disk model with a near-canonical warm-layer CO abundance supplies a comparable CO column. The measurement is consistent with the higher C$^{17}$O-based MAPS estimate. For the adopted hydrogen column, the inferred CO/H$_2$ ratio is consistent with a near-canonical abundance on the warm side of the snowline.
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All authors Chunhua Qi, Takahiro Ueda, David J. Wilner, Catherine C. Espaillat
Solar and Stellar Astrophysics
Moment-based formulas for the transport coefficients
J.-F. Wang and G. Qin
The coefficients of the transport equations, describing the propagation features, are particularly important in astrophysics, interplanetary physics, and experimental
plasma physics. In this paper, the variable-dependent
diffusion coefficients are investigated. For the momentum transport equations, we find that the coefficients are related to statistical quantities, some of which are new. In addition, these coefficients take logarithmic forms, which are different from the results derived in previous papers. For isotropic pitch-angle scattering, we also obtain a formula that takes a logarithmic form. For fractional transport equations, the coefficients expressed in terms of the moments are obtained from the governing equations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Building a Better Beta: Nucleation and Timescales in Cosmological Phase Transitions
William Searle and Csaba Balázs
First-order phase transitions in the early universe can generate a
stochastic background of gravitational waves, offering a unique probe of high-energy physics. In this work, we investigate aspects of bubble nucleation and transition timescales, which play a central role in shaping the resulting gravitational wave spectrum. Many common approaches characterise the transition rate via a Taylor expansion of the false
vacuum decay rate. We argue that a more fundamental description is instead given by the distribution of bubble lifetimes, and define a new timescale, $\beta_\nu$, as the first moment of this distribution. We show that $\beta_\nu$ reproduces the behaviour of previous timescale definitions in the appropriate limits, while avoiding their pathologies, and offers a more natural description of the ensemble of nucleated bubbles. We then quantify the impact of this improved timescale on the predicted gravitational wave spectrum, finding that it shifts the peak amplitude by up to an order of magnitude relative to previous definitions. As next-generation gravitational wave detectors come online, robust theoretical predictions will be essential; we hope this work represents a step in that direction.
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Earth and Planetary Astrophysics
Atmospheric escape fractionates secondary but not primary atmospheres
Mara Attia and Tim Lichtenberg
A
planet's atmosphere, heated by starlight, can flow off as a wind, taking some gases and leaving others in unknown proportions. Yet this selection wrote the noble-gas records of the terrestrial
planets, and decides which gases hot
exoplanets keep. We solve this fractionated escape problem for arbitrary composition: a wind sorts gases only for secondary, hydrogen-poor atmospheres, and removes primary, hydrogen-rich atmospheres wholesale. The algebraic solution recovers every published formula as special cases. It provides a unified interpretation of atmospheric
evolution across the Solar System and
exoplanets. Fractionating argon on Mars stripped carbon while sparing krypton, Venus' retained argon constrains the wind intensity that removed its water, Earth's xenon record excludes a neutral wind. The same solution ranks the rocky
exoplanets under JWST observation by the gases they can keep.
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