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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 15 July

Solar and Stellar Astrophysics

A Homogeneous Spectroscopic and Evolutionary Study of cool HgMn and hot Metallic A Stars

F. Kahraman Aliçavuş, E. Çelik and E. Niemczura

We present a homogeneous spectroscopic and evolutionary analysis of chemically peculiar stars, focusing on HgMn and metallic A (Am) subclasses. Particular emphasis was placed on the coolest HgMn stars and the hottest Am stars, motivated by the long-standing hypothesis that these objects may represent consecutive evolutionary stages of a similar stellar population. High-resolution spectra of 13 HgMn and 14 Am targets were analyzed to derive atmospheric parameters and detailed chemical abundances. While all HgMn stars were confirmed to retain their chemically peculiar nature, only six of the fourteen candidate Am stars exhibit abundance patterns consistent with genuine Am characteristics, highlighting the importance of homogeneous spectroscopic classification. We investigate the temperature dependence of elemental abundances, finding a positive correlation between Mn abundance and $T_{\rm eff}$ and a negative correlation for Ni, supporting the operation of atomic diffusion. Stellar evolutionary models were computed with the MESA code using atmospheric parameters derived from the spectroscopic analysis. The locations of the confirmed HgMn and Am stars in the Hertzsprung–Russell diagram support the possibility that the cool HgMn stars and the hot Am stars may occupy overlapping evolutionary sequences. Although only a limited number of candidate pairs were identified, further analyses using evolutionary models that include atomic diffusion are needed to test the possible connection between the two subclasses.
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Astrophysics of Galaxies

Mapping Dust Attenuation at Kiloparsec Scales. IV. A Dust-model Interpretation of Attenuation Curves in Nearby Galaxies

Ruonan Guo, Cheng Li, Tao Jing et al. (+3 more)

In this fourth paper on kiloparsec-scale dust attenuation, we ask whether the empirical trends found in Papers I–III can be translated into effective dust properties. Using attenuation curves for 2487 high-continuum-S/N spaxels in 91 SwiM v4.2 galaxies, we construct a grid of uniform-screen dust models composed of astronomical silicate and graphite grains with MRN-like size distributions. We fit the normalized attenuation-curve shape to constrain model parameters and then use the attenuation amplitude to estimate the model-dependent dust mass surface density. The inferred dust masses, compositions, and small-grain fractions are therefore effective quantities defined within the adopted attenuation model. The fitted models reproduce the main attenuation-curve variations and provide a direct bridge to Papers I–III: within this model, the relative 2175Å\ bump sequence maps mainly onto the effective fraction of small graphitic/carbonaceous grains, while the NUV-slope sequence maps onto the effective small-silicate grain fraction and total silicate mass fraction. Non-SF regions have higher dust mass surface densities but lower dust-to-stellar mass ratios than SF regions, separating absolute dust content from dust content per unit stellar mass. Regions with larger specific H$\alpha$ surface brightness have larger dust-to-stellar mass ratios but lower inferred small-grain fractions, especially lower small-silicate fractions. In non-SF regions this quantity is interpreted as ionized-gas emission per unit stellar mass rather than as a direct sSFR. These model-dependent trends support a picture in which local dust processing changes the relative abundance of small grains and thereby shapes the attenuation-curve variations found across the series.
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All authors Ruonan Guo, Cheng Li, Tao Jing, Shuang Zhou, Niu Li, Zhuo Cheng

Solar and Stellar Astrophysics

Cradle of Life: From the Formation of Stars to Habitable Worlds with the SKAO

Eleonora Bianchi, Joseph R. Callingham and the Cradle of Life working group

This chapter provides an overview of the different science cases covered by the "Cradle of Life" working group, which aims to leverage the capabilities of the Square Kilometre Array Observatory (SKAO) to trace the physical and chemical pathways toward stars and planets formation, how such stars impact their planets, and whether life could exist in such conditions. At its highest frequencies, the SKAO will probe the earliest stages of the raw material fuelling planet formation, while enabling deep, unprecedented searches for prebiotic molecules both in high-mass and solar-type protostars. Concurrently, the lowest frequencies will be deployed to detect and characterize exoplanetary magnetic fields via their auroral radio emission, and the type of space weather a planet experiences from its host star. Across the entire frequency range, the SKA telescopes will conduct systematic searches of technosignatures. Together, these high-impact research areas establish a comprehensive roadmap for the SKAO to uncover the origins of life in the universe.
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Instrumentation and Methods for Astrophysics

Fabrication of focusing optics for TA-MOONS: Micro-MOONS

Ceiwynn Longworth, Megan Delamer, Suvrath Mahadevan et al. (+3 more)

Understanding star and planet formation requires optical to near-infrared spectroscopic observations of a large number of young stellar objects. The TIFR-ARIES Multi-Object Optical to Near-infrared Spectrometer's (TA-MOONS) primary objective is to preform a large spectroscopic survey of young stellar objects across wavelengths of 360 nm to 2.5 microns, with the multiplexed capability of observing up to eight sources simultaneously. Multiplexity is achieved by moving pickup mirrors on robotic arms. One component of this robotic arm system is Micro-MOONS, a micro-optic array, nanofabricated to enable accurate calibration, validation, and positioning of stellar images onto the pickup mirrors. The micro-mirrors of the Micro-MOONS system are spherically concave, fabricated via two-photon polymerization(2PP) in the NanoScribe GT2 system, and are printed on plasma-cleaned silicon substrates using IP-S photoresist, followed by gold coating. 2PP allows for fine, detailed shapes on a sub-micron scale that are otherwise difficult and costly to obtain. The optimization of Micro-MOONS focuses on achieving uniformity, minimizing surface roughness, and preserving the desired radius of curvature to avoid beam obstruction near the pickup mirrors. This work demonstrates the feasibility of integrating advanced custom-printed micro-optics into multi-object spectroscopic instruments, enabling improved calibration and efficiency in large-scale stellar surveys.
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All authors Ceiwynn Longworth, Megan Delamer, Suvrath Mahadevan, Joe P. Ninan, Kathleen Gehoski, Krushna Jadhav

Cosmology and Nongalactic Astrophysics

Evaporating cosmologically coupled black holes

Marco Calzà, Davide Pedrotti, Massimiliano Rinaldi et al. (+1 more)

Cosmologically coupled black holes (CCBHs), whose masses evolve in response to the cosmological expansion, have recently attracted significant theoretical and observational interest. Existing studies have treated CCBHs as purely classical objects, neglecting the effect of Hawking radiation (HR), which competes with the cosmological coupling (CC) mechanism. We take a first step towards studying evaporating CCBHs, adopting a quasi-adiabatic approximation in which the HR rate is evaluated at the instantaneous CCBH mass, and modeling the CC mechanism through the phenomenological scaling of the mass with the scale factor, $M \propto a^k$. We show that, depending on the coupling strength $k$, even late-time CC activation can significantly delay Hawking evaporation, or lead to asymptotic CC-dominated mass growth, with important implications. We set limits on the abundance of primordial CCBHs from $\gamma$-ray observations, finding limits which are weaker than their uncoupled counterparts, as CCBHs are kept farther from the endpoint of evaporation for a longer time. Unlike standard primordial black holes, the CCBH formation and present-day masses no longer approximately coincide, even for formation masses $M_{\text{form}} \gtrsim 10^{15}\,{\text{g}}$. Therefore, the same population of primordial CCBHs may be subject to evaporation limits through its past emission history, as well as to other limits (such as microlensing) through its present-day mass.
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All authors Marco Calzà, Davide Pedrotti, Massimiliano Rinaldi, Sunny Vagnozzi

Solar and Stellar Astrophysics

The SKA as a Probe of Heliospheric Turbulence and Radio-wave Propagation Effects

Nicolina Chrysaphi, Eduard P. Kontar, Hamish A. S. Reid et al. (+3 more)

Density turbulence in the heliosphere can impact traversing radio photons originating from anywhere in the universe, leading to distortions of both the spectroscopic and imaging properties of the radio sources. Extra-solar radio sources exhibit scintillation and angular broadening, while monochromatic signals from spacecraft are spectrally broadened. It was recently demonstrated that such impacts, referred to as radio-wave propagation effects, are particularly significant in observations of solar radio bursts excited through the plasma emission mechanism. A comparison of detailed observations with simulations is required in order to quantify the radio-wave propagation effects and disentangle the true radio-source properties from the observed ones, enabling the diagnosis of the heliospheric environment. Consequently, theoretical advancements and our ability to quantify the heliospheric turbulence depend on the quality and quantity of available observations. SKA pathfinders, like LOFAR, have been key to the significant progress recently achieved, but have also highlighted areas where the available observing capabilities are lacking. The SKA's unrivalled sensitivity will be crucial in identifying and distinguishing fine and faint radio structures, where our ability to model them defines whether we can accurately describe the heliospheric turbulence and deduce the fundamental properties of the radio sources. The SKA will be an indispensable tool in observing solar radio emissions from the Sun to beyond 1 au, complemented by ground-based interferometers that can reach frequencies down to the ionospheric cut-off at 10 MHz and space-based radio instruments which cover frequencies down to a few kHz.
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All authors Nicolina Chrysaphi, Eduard P. Kontar, Hamish A. S. Reid, Sophie Musset, Shilpi Bhunia, Kamen Kozarev

Earth and Planetary Astrophysics

Reflation: redox-driven atmospheric inflation as tracer of super-Earth geochemistry

Lorenzo Cesario, Tim Lichtenberg, Mara Attia et al. (+3 more)

We demonstrate that the redox-sensitivity of mantle outgassing can trigger transient episodes of atmospheric re-inflation in highly irradiated and geochemically-reduced super-Earths, a mechanism we term reflation. Mantle redox governs the outgassing and speciation of CHONS volatiles, setting the background secondary atmospheric composition during extended photoevaporation at highly irradiated conditions. Using simulations of the coupled atmosphere-interior evolution of irradiated super-Earths, we illustrate that reduced mantles close to the iron-wustite buffer initially produce CO-dominated atmospheres. Hydrodynamic escape continuously removes volatiles while outgassing from the melt replenishes the atmosphere with H2, converted from H2O dissolved in the underlying magma ocean. This leads to a late-stage transition from C- to H-dominated gas that transiently re-inflates super-Earth atmospheres and decreases their bulk densities by up to $\sim$60$\%$ between several hundreds of Myr to Gyr after their formation, prior to complete atmospheric erosion by photoevaporation. In contrast, oxidised mantles, closer to Earth-like geochemistry, strongly buffer their atmospheric composition while exposed to hydrodynamic escape, producing monotonic radius deflation. Reflation events are triggered by geochemically-reduced mantles, intermediate escape efficiencies, high irradiation, and initial water inventories $\gtrsim$ 5 Earth oceans. This redox-dependent evolutionary divergence hinges on the sensitive feedback between interior and atmospheric evolution serving as a potential tracer of historical geochemical state. Population-level reflation signatures of close-in super-Earths may thus serve as tracers of interior geochemistry and formation conditions.
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All authors Lorenzo Cesario, Tim Lichtenberg, Mara Attia, Harrison Nicholls, Imre Kisvardai, Quentin Changeat

Astrophysics of Galaxies

RABBITS IV: Stellar feedback and SMBH merging time-scales in the sub-Milky Way mass regime

Ruby J. Wright, Roosa Heiskanen, Shihong Liao et al. (+5 more)

Merging supermassive black holes (SMBHs) in low- and intermediate-mass galaxies are important sources for future millihertz gravitational-wave observatories such as LISA. Predicting the delay between galaxy coalescence and SMBH merger is therefore critical for modelling the observable SMBH merger population. Using the KETJU code, we perform 16 equal-mass galaxy merger simulations as part of the Resolving supermAssive Black hole Binaries In galacTic hydrodynamical Simulations (RABBITS) series to investigate SMBH binary evolution in galaxies with stellar masses below $M_{\star}\lesssim10^{10}\,{\rm M}_{\odot}$. We systematically vary the strength of stellar feedback by altering the supernova outflow velocity by a factor of $\sim4$, while still producing galaxies consistent with observed scaling relations. We find post-hardening SMBH merger time-scales spanning $\sim30$-$500\,{\rm Myr}$, with stronger stellar feedback producing systematically longer merger delays through its impact on the central stellar density of the merger remnants. Across our suite, merging time-scales vary by more than an order of magnitude, demonstrating that uncertainties in stellar feedback alone can translate into large uncertainties in SMBH merger delays. At the onset of hardening, the binary evolution remains consistent with stellar-dynamical hardening models based on the local stellar density and velocity dispersion near the binary sphere of influence. Using KETJU as a benchmark, we show that merging time-scales can be recovered with useful accuracy when these nuclear stellar properties are extrapolated from scales up to $\sim 100\,R_{\rm infl}$. These results provide a promising route for modelling SMBH mergers in cosmological simulations.
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All authors Ruby J. Wright, Roosa Heiskanen, Shihong Liao, Alexander Rawlings, Peter H. Johansson, Max Mattero, Fiona H. Panther, Atte Keitaanranta

Solar and Stellar Astrophysics

Unveiling the nature of G6096: a likely hierarchical triple system

Yinghao Xu, Xinlin Zhao, Song Wang et al. (+10 more)

G6096 (Gaia DR3 609651611028044544) was recently reported as a wide ($P\sim 450$ days) and eccentric ($e\sim0.18$) binary possibly hosting a massive white dwarf or neutron star. In this work, through analyses of the projected rotational velocity between the blue and red bands, spectral disentangling, joint radial velocity and astrometric fitting, and X-ray emission, we suggest that the system contains additional visible component(s) rather than a compact object. We develop a new approach to reveal the nature of G6096 by jointly modeling the spectral energy distribution, rotational velocity, and astrometric measurements. Finally, we speculate that G6096 is a hierarchical triple main-sequence star system, comprising a primary with a mass of $\sim 0.75\,M_\odot$ orbited by an inner binary consisting of two dwarfs with masses of $\sim 0.62\,M_\odot$ and $\sim 0.40\,M_\odot$, respectively. This method may help reveal a population of triple systems when applied to Gaia astrometric data, particularly the upcoming DR4.
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All authors Yinghao Xu, Xinlin Zhao, Song Wang, Guang-Yao Xiao, Zikun Lin, Xue Li, Hao-Bin Liu, Henggeng Han, Weiyi Chen, Yucong Weng, Meng Sun, Xiaohong Yang, Jifeng Liu

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

High-Energy Neutrinos from Black Hole Evaporation in Neutron Stars

Ioannis Dalianis

We investigate the production of high-energy neutrinos from microscopic black holes formed through the gravitational collapse of asymmetric dark matter accumulated inside neutron stars. When Hawking evaporation dominates over accretion, long-lived, feebly interacting particles beyond the Standard Model escape the neutron star and subsequently decay into high-energy neutrinos. We analyze the repeated cycle of dark matter capture, black hole formation, and evaporation, identifying two distinct regimes determined by the competition between the dark matter thermalization time and the collapse cycle. In particular, we identify a partially thermalized regime in which the dark matter cloud evolves toward a quasi-stationary state with a temperature significantly exceeding that of the neutron star core. We derive the time-integrated Hawking emission, the resulting secondary neutrino spectra, and the expected Galactic and diffuse extragalactic neutrino fluxes. The predicted signal exhibits two distinctive signatures: a broad neutrino spectrum with a characteristic energy scale set by the initial Hawking temperature of the evaporating black hole, whose spectral peak naturally lies above $\mathcal{O}(10)$ TeV, and an extended Galactic component strongly concentrated toward the Galactic Center. Although the predicted event rates are generally small, the resulting signal may contribute at the percent level to the observed Galactic high-energy neutrino flux under favorable microscopic and astrophysical conditions. The proposed mechanism provides a new observational window on Hawking evaporation through microscopic black holes continuously produced inside neutron stars, linking dark matter, compact objects, black hole thermodynamics and high-energy neutrino astronomy.
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Astrophysics of Galaxies

Tidal Tails of Galactic Open Clusters: A Review of Methods, Evidence, and Sources of Disagreement

Tahereh Ramezani, Johana Balciráková, Prapti Mondal et al. (+3 more)

Tidal tails are a natural consequence of the dynamical evolution of open clusters in the Galactic tidal field, but their observational identification is intrinsically difficult because their surface density is low and the Galactic disc contains a dense and kinematically structured field population. This review paper provides a critical synthesis of the observational and theoretical status of tidal tails of Galactic open clusters and, in particular, assesses how membership definitions, data dimensionality, clustering algorithms, and dynamical assumptions affect reported tail detections. We compare the principal approaches used with Gaia data, including convergent-point and co-moving selection, density-based clustering, probabilistic membership models, machine-learning methods, and orbit/N-body-based filtering. We compile published measurements for a representative sample of nearby clusters and explicitly distinguish robust detections from candidate or method-dependent extended structures. The literature has progressed from detailed studies of a few nearby clusters to systematic searches involving tens to hundreds of systems. The Hyades remains a benchmark because independent analyses recover coherent leading and trailing tails, but the extent and membership of the tails depend on the adopted selection. Large Gaia DR3 studies demonstrate that extended populations are common among nearby and intermediate-age clusters, while also showing that some structures can be produced or exaggerated by projection, field contamination, or the assumptions built into the membership model. Recent homogeneous analyses report tails in most of the nearby clusters in selected samples, but the corresponding catalogues should not be interpreted as equivalent because their completeness, contamination, and physical definitions of a "tail member" differ.
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All authors Tahereh Ramezani, Johana Balciráková, Prapti Mondal, Katerina Neumannova, Ernst Paunzen, Gabriel Szasz

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

Solid-state gravitational-wave detectors at GHz frequencies: the search for the primordial stochastic GW background and light primordial black hole binaries

Juan Garcia-Bellido

Reheating after inflation is one of the strongest sources of gravitational waves (GW), producing a stochastic background (SGWB) with a non-thermal spectrum peaked at frequencies of order a few GHz. Detecting it is difficult: experiments based on the inverse Gertsenshtein effect in intense magnetic fields reach the MHz but not the GHz band, where the typical strain is around $10^{-30}$. The same window contains the coalescence of light primordial black hole (PBH) binaries, whose merger frequency $f\simeq4.4\ \mathrm{kHz}\,(M_\odot/M)$ falls in the MHz–GHz range for planetary to sub-planetary masses; since such objects are necessarily sub-solar, their detection would be strong evidence for PBHs as a component of the dark matter. We propose a solid-state detector at GHz frequencies that could integrate over months to years the GW continuously arriving from the Big Bang and search for light PBH binary coalescence. As a concrete realization we consider a modular array of $\sim10^3$ ultra-pure sapphire $(10\ \mathrm{cm})^3$ monocrystals forming a cubic-metre detector read out by cryogenic single-phonon sensors, whose segmentation provides thermal isolation, favourable counting statistics and coincidence-based background rejection. We also compare candidate materials, finding diamond superior per unit volume but limited by the unavailability of large single crystals. Finally, we contrast the two targets. The stationary background is a shot-noise-limited counting problem, best served by a narrow, resonance-enhanced, long-integration search; the loud transient chirp of a nearby merger is better caught by a fast, broad-band search with coincidence tagging. Because the phonon spectrum is continuous, a modular solid-state array can serve both, by staggering resonant cells across the band while running a broad-band subset for chirp tracking.
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Earth and Planetary Astrophysics

GRACE-DG: A Discontinuous Galerkin Method-Based Code for General Nonlinear Coagulation-Fragmentation Equations

Jing Yang, Zhuo Chen and Xue-Ning Bai

Dust plays a crucial role in protoplanetary disks (PPDs) evolution and planet formation, influencing disk dynamics through gas-dust coupling, regulating disk temperature by dominating continuum opacity, and altering disk ionization fraction by capturing free electrons. In this work, we develop a high-order discontinuous Galerkin (DG) method-based open-source code GRACE-DG to solve the collision-induced coagulation-fragmentation equations. In particular, we have derived a new conservative formulation for the non-linear fragmentation term, which enables the DG method to capture the mass transfer process. The new solver exhibits good convergence in coupled aggregation and breakage simulations, making it highly suitable for future integration into hydrodynamic codes.
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Astrophysics of Galaxies

Adaptive optics imaging of the nuclei of Seyfert 2 galaxies: An unexpectedly high incidence of nuclear stellar rings

Nina Mackensen, Jochen Heidt and Francisco Pozo Nuñez

High-resolution imaging of active galactic nuclei (AGNs) on subkiloparsec scales is essential for investigating their fueling. Observations in the near-infrared (NIR) are especially valuable as they minimize the absorption by dust. However, the inferred nuclear morphology may depend on the method used to analyze the images. We assess whether ground-based adaptive-optics observations of the cores of Seyfert 2 galaxies in the Ks band provide advantages over HST observations at shorter wavelengths (V and H bands). We also investigate whether a dedicated 2D analysis is preferable to a 1D approach. A sample of 18 Seyfert 2 galaxies was observed with the adaptive optics (AO) system in the Ks band at the Large Binocular Telescope (LBT) and compared to archival HST V- or H-band images. The analysis included a 2D modeling procedure via GALFIT as well as an unsharp masking technique. Results from different filters are consistent, showing no clear advantage of the redder filter. Using both GALFIT and unsharp masking in tandem is preferable, as the two methods provide complementary strengths. We identified nuclear stellar rings in 8 of the 18 galaxies in our sample (44 +/- 12%). This fraction is significantly higher than reported in previous studies and about a factor of two higher than reported in the most complete atlas of nuclear rings. The radii, size distribution, and inferred masses of the detected nuclear rings are similar to those observed in non-active galaxies. Low-luminosity AGNs appear to have little impact on nuclear ring formation and evolution. The high incidence of nuclear stellar rings in our study is unexpected and warrants further investigation. This could be tested further using the large number of suitable archival HST images available. If confirmed, it would imply that nuclear stellar rings are considerably more common than previously recognized.
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Astrophysics of Galaxies

The different methods to calculate cluster membership probabilities

Tahereh Ramezani, Prapti Mondal, Katerina Neumannova et al. (+3 more)

Reliable membership determination is a fundamental step in the study of star clusters. With the advent of $Gaia$ astrometry, a wide range of statistical and machine-learning techniques has been developed to assign membership probabilities. However, the current situation of membership lists is very unsatisfactory. This review summarises the main methodologies, compares their strengths and limitations, and discusses future directions. The aim is to provide a comprehensive overview and to lead to a more efficient and reliable approach for the forthcoming $Gaia$ DR4. Basically, we know of spatial, classical kinematic, and photometric methods, as well as maximum likelihood and Bayesian statistical methods, and machine learning and clustering algorithms. These different methods come with many modifications and flavours. We assessed all the advantages and disadvantages of the known methods to determine cluster membership probabilities. Although nowadays most methods are based on poor statistical numerics, the more robust algorithms should still be taken into account. It is important to apply and compare several methods. The next step must be to define a list of standard star clusters to test and verify all known methods. The list must cover the complete grid of cluster parameters (age, distance, reddening, and metallicity) and total masses.
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All authors Tahereh Ramezani, Prapti Mondal, Katerina Neumannova, Ernst Paunzen, Johana Supikova, Gabriel Szasz

Solar and Stellar Astrophysics

Multi-height Diagnosis of MHD Wave Periods and their Propagation in Solar Plages Using IRIS Observations

Gayathri Hegde and Pradeep Kayshap

This work aims to investigate magnetohydrodynamic (MHD) waves in solar plages at five distinct heights, spanning from photosphere to the upper chromosphere, using spectroscopic observations provided by Interface Region Imaging Spectrograph (IRIS). The dominant period is found to not change within the plages, while, in pores, the dominant period decreases linearly from 4.20 to 3.20 minutes from the photosphere to the upper chromosphere. Furthermore, in the solar plages, cross-wavelet analysis reveals that periods from 2.0 to 6.0 minutes propagate till the upper chromosphere from the photosphere. The periods beyond 6 minutes have a zero/constant phase difference in the photosphere and in the middle chromosphere. Thus, the 6.0-minute period would be considered the cutoff period at these heights. Next, the propagation speeds of MHD waves above solar plages are estimated in the photosphere and chromosphere. Within the limit of uncertainties, the propagation speed in solar plage is close to the sound speed; hence, the waves are slow magnetoacoustic in nature. Lastly, with the help of phase difference analysis, we found that formation heights of Mg ii k2r and Mg ii k3 are underestimated in solar plage, while the formation height of Mn i is overestimated. In case of pores, the formation heights of Mg ii k2r, Mg ii k3, and Mn i are overestimated. Interestingly, in the quiet-Sun (QS), the formation heights of Mn i and Fe i are nearly the same, and also the formation height of Mg ii k3 is similar to the formation height of Mg ii k2r. In conclusion, some important findings are reported in this work, namely, (1) dominant periods at five different heights between the photosphere and chromosphere, (2) estimation of cutoff periods in the photosphere, middle chromosphere, and the upper chromosphere in the plages, and (3) variations in the formation heights of these spectral lines in pore, plage, and QS.
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High Energy Astrophysical Phenomena

Towards a joint X-ray and gamma-ray analysis of Pulsar Wind Nebulae with Gammapy

Katharina Egg and Alison M. W. Mitchell

For detailed studies of Pulsar Wind Nebulae (PWNe), objects that show photon emission across the entire electromagnetic spectrum, multiwavelength analyses are crucial. The comparison of especially X-ray and gamma-ray emission and their angular sizes can help us to constrain the properties of PWNe, such as their particle transport mechanism or their potential for the acceleration of hadronic particles. In this vein, we are working towards a joint analysis of eROSITA X-ray data and H.E.S.S. gamma-ray data. To enable this, eROSITA data is adapted into the framework of Gammapy, a Python package for gamma-ray analysis through a multi-step process of adapting the formats of not only the photon event list, but also all X-ray response functions, into open data formats compatible with Gammapy. This is accomplished using newly developed Python converter functions. In this contribution we present the first eROSITA maps of the PWN MSH 15-52 in Gammapy, compared to the associated H.E.S.S. emission.
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Instrumentation and Methods for Astrophysics

Proof of concept of heterodyne interferometry at 10.6 um using photonic correlation

Tituan Allain, Jean-Philippe Berger, Guillaume Bourdarot et al. (+2 more)

The task of imaging complex dust environments such as the inner astronomical units of a planet-forming disks requires dedicated mid-infrared (MIR) interferometric facilities with kilometric baselines and a large number of telescopes. Extrapolating technologies from current facilities is not straightforward. We aim to demonstrate the feasibility of using MIR heterodyne interferometry with a photonic correlation approach to recombine MIR signals from distant telescopes. We want to determine the current technological limits of such systems are. We developed a laboratory demonstration bench that can correlate MIR signals at 10 um with a photonic correlator. The photonic correlator uses commercially available telecom components at 1.5 um to transport and correlate heterodyne signals that could go up to 10 GHz in bandwidth, directly extendable to 40 GHz. We used the demonstration bench to study the noise levels and detection limits of a heterodyne interferometer with a photonic correlation. We confirm the correlation exhibited by wideband MIR signals with the photonic correlator, along with a characterization of the performance of the system and analyzed the noise levels. We show that the photonic correlator does not limit the detection and that it can be used to compensate for free-space delays at 10 um with a fiber delay at 1.5 um. With our current sub-optimal commercial infrared (IR) detectors, we have derived a detection limit of 130 Jy that is coherent flux for 8 m class telescopes with 1 h of incoherent integration. We discuss the possibility of lowering the detection limit down to typical T-Tauri stars (approximately 1 Jy) using new detectors and coherent integration based upon local oscillator synchronization with telecom fiber links.
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All authors Tituan Allain, Jean-Philippe Berger, Guillaume Bourdarot, Carlo Sirtori, Hugues Guillet De Chatellus

High Energy Astrophysical Phenomena

Assessing the sensitivity to Axion-Like-Particle Dark Matter with very-high-energy gamma-ray observations of selected AGN and galaxy cluster pairs

Cervane Grimaud, Denys Malyshev and Emmanuel Moulin

Axion-Like-Particles (ALPs) are pseudo-scalar particles actively searched as light dark matter candidates. ALPs can couple to photons which give rise to the possibility of oscillations with photons in an external magnetic field. If sufficiently strong, this coupling can imprint distinctive spectral irregularities in the gamma ray spectrum of astrophysical sources. We present a prospective study on the sensitivity of probing ALP-photon interactions using stacked observations of selected active galactic nuclei (AGNs) located behind galaxy clusters. The ALP-photon conversion in cluster magnetic fields produces absorption-like features in AGN spectra that are difficult to predict for individual sources. To address this, we apply a stacking analysis of multiple AGN-cluster pairs, yielding a controlled prediction of the expected ALP induced spectral patterns and enhancing the sensitivity to such irregularities. Using simulated data for selected hard-spectrum Fermi/LAT AGNs that can be observed by Imaging Atmospheric Cherenkov Telescopes such as H.E.S.S., we evaluate the performance of this method. The combination of mock IACT observations with our stacking approach enable exploration of the previously uncharted ALP dark matter parameter space in the neV mass range.
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Earth and Planetary Astrophysics

Advanced Techniques in Stability Analysis of Trans-Neptunian Objects

Tamás Kovács

The trans-Neptunian region (30-50 AU) is a dynamically structured reservoir of icy planetesimals whose orbital architecture reflects resonant dynamics, chaotic transport, and long-term gravitational sculpting by the giant planets. This review synthesizes recent developments in the dynamical investigation of trans-Neptunian objects (TNOs), with an emphasis on mean-motion and secular resonances, as well as chaotic diffusion, in a system whose growing observational census makes it an ideal testbed for chaos detection methods. Classical indicators, including Lyapunov exponents, MEGNO, SALI/GALI, and frequency map analysis, provide the quantitative backbone for mapping TNO phase space and are complemented by modern approaches such as Lagrangian descriptors, the FAIR resonance identification method, entropy-based chaos indicators, and recurrence plot divergence methods. An anomalous diffusion framework, in which mean squared displacement scales as a power law in time, further enables classification of sub- and superdiffusive orbital transport. Machine learning has emerged as a powerful complement to traditional dynamical methods: surrogate classifiers, deep neural network solvers, and hybrid physics-data-driven frameworks together extend reliable prediction horizons in chaotic regimes and open new routes for Bayesian inference of migration scenarios. The review concludes that the most promising path forward lies in hybrid dynamical-statistical frameworks anchored to Hamiltonian dynamics, enabling efficient exploration of high-dimensional parameter spaces informed by the expanding body of trans-Neptunian observations.
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High Energy Astrophysical Phenomena

Combined KM3NeT/ARCA and ANTARES search for compact neutrino sources

V.Kulikovskiy, B.Caiffi, S.Alves Garre et al. (+9 more)

High-energy neutrinos from point-like sources are searched in the combined dataset from ANTARES and the available KM3NeT/ARCA data. This analysis demonstrates the potential of combining data from these neutrino detectors using a binned likelihood approach.
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All authors V.Kulikovskiy, B.Caiffi, S.Alves Garre, J. Aublin, M. de Jong, A. Heijboer, G. Illuminati, R. Muller, V. Parisi, M. Sanguineti, F. Vazquez de Sola, S. Zavatarelli

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

Right-Handed Neutrino Production by an Axion-like Inflaton: Implications for Leptogenesis

Weiyi Deng, Chengcheng Han, Wuzhou Yin et al. (+1 more)

We study heavy right-handed neutrino production induced by a derivative coupling to an axion-like inflaton and its implications for non-thermal leptogenesis. We develop a unified treatment of Majorana-fermion production during inflation and preheating. During inflation, the rolling inflaton background generates a helicity-asymmetric spectrum that can be obtained analytically in the slow-roll regime, while during preheating the oscillating background drives repeated non-adiabatic production events with a helicity-dependent effective momentum and a natural momentum cutoff. We compute the resulting abundance in both the delayed-decay and prompt-decay limits, including the effects of Pauli blocking and successive production stages. We further clarify the relation between the fermion basis used to identify non-adiabatic production and the Hamiltonian-diagonal basis used to define instantaneous occupation numbers. Applying these results to non-thermal leptogenesis, we identify parameter regions consistent with the observed baryon asymmetry.
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All authors Weiyi Deng, Chengcheng Han, Wuzhou Yin, Tong Ju

Instrumentation and Methods for Astrophysics

Design and Implementation of a Microservice-Architecture Master Control System for AIMS

Li-Yue Tong, Jia-Ben Lin, Jun-Feng Hou et al. (+11 more)

The mid-infrared solar magnetic field telescope AIMS (An Infrared System for the Accurate Measurement of Solar Magnetic Field) is the first ground-based telescope designed to directly measure solar magnetic fields via Zeeman splitting in the 8-14 um band, overcoming the century-long bottleneck of model-dependent indirect measurements. Its remote high-altitude site, heterogeneous multi-institute components, and complex observation modes comprising Fourier Transform Infrared (FTIR) spectropolarimetry and broadband imaging demand a highly autonomous Master Control System (MCS). We present the design and implementation of the AIMS MCS, featuring three key contributions: (1) an L0-L5 telescope automation classification inspired by the SAE J3016 autonomous driving standard, providing well-defined boundaries and a progressive evolution roadmap; (2) a three-layer system framework device control, autonomy support, and central decision-implemented with a microservice software architecture that achieves loose coupling, high cohesion, and continuous integration of heterogeneous components; and (3) a suite of key enabling tech-nologies including automatic pointing/tracking, autofocus via lucky-frame selection combined with power spectral ratio analysis, and environment-adaptive observation integrating auto-exposure, cloud detection, and power/thermal monitoring. The MCS has been validated across three telescopes at progressive automation levels: AIMS itself, the WenQuan Solar Magnetic Field Telescope, and the Solar Full-disk Multi-layer Magnetograph (SFMM). Collectively, these deployments demonstrate the feasibility and stability of the proposed architecture for progressive telescope automation.
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All authors Li-Yue Tong, Jia-Ben Lin, Jun-Feng Hou, Yuan-Yong Deng, Dong-Guang Wang, Guang-Qian Liu, Song-Bo Xu, Shang-Jie Ren, Lian-Wei Zhao, Zhi-Wei Feng, Wei Duan, Ming-Fu Shao, Hui Wang, Chen Yang

Solar and Stellar Astrophysics

Improving reddening estimates for RR Lyrae stars in the Gaia bands: a machine learning approach to the PAC(Z) relation

A. Garofalo, T. Muraveva, L. Monti et al. (+3 more)

RR Lyrae stars are essential tracers of old stellar populations and distance indicators across the Milky Way and nearby galaxies. However, their use as standard candles is limited by uncertainties in extinction, especially in the Gaia bands. In Gaia DR3, absorption values (AG) for fundamental-mode RR Lyrae (RRab) were based on an empirical period-amplitude-color (PAC) relation calibrated on a small sample and on passband transformations. We aim to recalibrate extinction relations for RRab stars and establish, for the first time, analogous relations for first-overtone RR Lyrae (RRc) stars in the Gaia passbands. We used Gaia DR3 photometry and pulsation properties of an all-sky reference sample. Intrinsic colors (G - GRP)0 and (GBP - GRP)0 were derived through sequential feature selection combined with linear regression and bootstrap resampling, ensuring robust estimates of color excess and AG. We recalibrated PACZ relations for RRab stars and derived, for the first time, PAC relations for RRc stars in the Gaia bands. The new relations reproduce intrinsic colors with residual scatters of ~0.03-0.04 mag and provide AG estimates across both pulsation types. Tests on RR Lyrae stars in Galactic globular clusters and dwarf galaxies show consistent AG values, with the PAC(Z) relations based on (GBP - GRP) being more stable than those using (G - GRP). The new relations provide reliable extinction estimates for both RRab and RRc stars, improving on the DR3 implementation and offering a valuable tool for Galactic studies in view of Gaia DR4.
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All authors A. Garofalo, T. Muraveva, L. Monti, G. Clementini, F. Cusano, L. Valentini

Instrumentation and Methods for Astrophysics

JW-ASTClaw: A Generalizable Multi-Agent Framework for Autonomous Solar Telescope and Its Implementation within Chinese Meridian Project

Li-Yue Tong, Jia-Ben Lin, Yuan-Yong Deng et al. (+4 more)

We present the first deployment of an end-to-end autonomous control system driven by a large language model (LLM) on an operational solar telescope-the Solar Full-disk Multi-layer Magnetograph (SFMM), named JW-ASTClaw. This system employs a multi-agent framework adopting a decoupled three-layer architecture (perception-decision-execution) interconnected through the Model Context Protocol (MCP), which addresses real-time adaptive scheduling under complex environmental conditions while achieving high portability: the perception and decision logic are reused unchanged across instruments, requiring only telescope-specific command interfaces to be adapted. Three perception agents-data-quality-agent, cloud-analyzer-agent, and flare-detector-agent-encode senior observer expertise, including wind jitter detection via limb-ring standard deviation, projected-circle zonal cloud analysis, and multi-band active region identification, as LLM-callable rules, while a central reasoning engine performs multi-source fusion and conflict resolution. The system supports graceful degradation from cloud LLM to local inference and finally to rule-based fallback, designed for remote field stations with unstable connectivity. Cross-season validation on archival data demonstrates 100% cloud detection with zero false positives across 10 distinct observation dates, with active-region counts and positions closely matching the NOAA Solar Region Summary (SRS) reports (102 vs. 100 across 10 separate validation dates). These capabilities significantly improve scientific-intent-driven observation accessibility, enable rapid flare response for space weather monitoring, enhance data usability under adverse conditions, and increase observability during partially cloudy periods.
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All authors Li-Yue Tong, Jia-Ben Lin, Yuan-Yong Deng, Ying-Zi Sun, Ming-Fu Shao, Hui Wang, Chen Yang

Earth and Planetary Astrophysics

SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program II. Spectrophotometric analysis and orbital monitoring of directly imaged companions

Andrea Bernardi, Alice Zurlo, Cecilia Lazzoni et al. (+6 more)

Over the past decade, advances in high-contrast imaging instrumentation, coupled with extreme adaptive optics systems, have enabled the discovery of tens of planets and brown dwarfs orbiting at wide separations from their host stars (a larger than 10 au). The existence of companions at these separations challenges current planet-formation paradigms, highlighting the importance of high-contrast imaging as the only technique capable of directly probing this region of planetary systems. In this paper, we present a survey of thirteen planets and brown dwarfs observed with VLT/SPHERE between June 2023 and July 2025. These data provide updated photometry in the 1.0-1.7 micron range and new high-precision astrometry, enabling tighter constraints on their orbital properties. We used the IRDIS subsystem to acquire dual-band H2H3 images (H2 = 1.593 microns, H3 = 1.667 microns) for all companions in our sample. For the three objects located within the IFS field of view (GQ Lup B, PZ Tel B, and HD 984 B), we additionally obtained low-resolution (R ~ 50) near-infrared (0.96-1.34 micron) spectra. We combined our new astrometric measurements with those available in the literature to derive updated orbital solutions. The orbital fitting was performed using the orbitize! Python package. For CT Cha b, HIP 78530 B, HIP 64892 B, and RX J1609.5-2105 b, this work provides the first orbital solutions to date. We derived new photometry for all objects, which, when compared with field dwarfs in color-magnitude diagrams, indicates spectral types ranging from mid-M to mid-L. For the companions observed with IFS, their spectra are best matched by those of M6-M8.5 field dwarfs. Our updated orbital fits provide tighter constraints for nearly all companions and are consistent with non-circular orbits in all cases, potentially disfavoring core-accretion formation within their circumstellar disks.
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All authors Andrea Bernardi, Alice Zurlo, Cecilia Lazzoni, Silvano Desidera, Dino Mesa, Sebastian Pérez, Pedro Henrique Nogueira, Domenico Barbato, Anuroop Dasgupta

Solar and Stellar Astrophysics

Ion-Scale Current Sheets Embedded in Reconnection Jet Shear Layer of the Near-Sun Heliospheric Current Sheet

Dae-Young Lee, Dooyoung Choi, Kyung-Eun Choi et al. (+1 more)

Context. Magnetic reconnection in the heliospheric current sheet (HCS) plays an important role in restructuring the solar wind magnetic topology and generating plasma jets and magnetic islands. While large-scale signatures of HCS reconnection have been reported in many observational studies, the kinetic-scale structure embedded within reconnection regions remains less well understood. Aims. We investigate the ion-scale currents sheets (CSs) embedded within an HCS reconnection region and their relationship to the flow-shear layer at the edge of a reconnection jet. Methods. We analyzed an HCS crossing observed by the Parker Solar Probe on March 29, 2024, using high-time-resolution magnetic field measurements. We focused on ion-scale magnetic transitions within two brief intervals of flow-shear layer at the edges of the reconnection jet and examined them in a local LMN coordinate system. Results. Twelve representative CSs are identified, whose duration is on average $\sim$0.06 sec, corresponding to spatial scales of only a few ion inertial lengths. They are classified into three types based on the behavior of the out-of-plane magnetic component $B_{M}$: (1) CSs showing clear bipolar $B_{M}$ variations without bifurcation in reconnecting-field ($B_{L}$), (2) CSs with both bipolar $B_{M}$ variations and bifurcated $B_{L}$ profiles characterized by a plateau structure, and (3) CSs where strong fluctuations obscure an otherwise expected bipolar signature. Conclusions. The reconnection jet shear layer in the HCS may serve as an active site that hosts a chain of ion-scale CSs. This provides new insight into the multiscale structure of HCS reconnection and suggests that flow shear layers may play an important role in generating secondary kinetic-scale structures.
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All authors Dae-Young Lee, Dooyoung Choi, Kyung-Eun Choi, Sung Jun Noh

Instrumentation and Methods for Astrophysics

Scientific-Intention Driven Embodied Intelligent Solar Telescope: Conceptual Design

Lin Jiaben, Tong Liyue, Wang Hui et al. (+2 more)

Artificial Intelligence (AI) is profoundly transforming the paradigms of scientific research. Cutting-edge technologies such as Large Language Models (LLMs) and embodied intelligence are continuously pushing the boundaries of scientific instrumentation. Against this backdrop, this paper proposes a novel conceptual system: the Scientific-Intention Driven Embodied Intelligent Solar Telescope (SIDEST). The system is designed with three core layers to achieve three types of intelligent scientific research closed loops. First, the Scientific Intent Research and Demonstration Layer parses the research objectives and intents of scientists (e.g., solar physicists) through natural language interaction, achieving a closed loop for the generation and optimization of executable observation plans aligned with scientific intent via in-depth research. Subsequently, the Observation Realization Layer schedules embodied intelligent solar telescopes to implement a closed loop for the execution of scientific observation plans. Finally, the Evaluation and Evolution Layer coordinates intelligent agents for data processing and scientific analysis to analyze observation data, generate research reports, and iteratively optimize observation strategies and model methods based on results, thereby realizing a self-evolving closed loop for the entire system. During the research process, we constructed a minimal prototype system based on a precision temperature control device for solar telescope birefringent filters to validate the core principles of SIDEST. This prototype successfully implemented all key steps of intention-driven automated research, demonstrating the feasibility of the technical pathways for the three types of intelligent research closed loops. SIDEST redefines telescopes through cutting-edge AI methods.
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All authors Lin Jiaben, Tong Liyue, Wang Hui, Shao Mingfu, Yang Chen

High Energy Astrophysical Phenomena

Inverse Transfer in Non-helical 2D Collisionless Magnetic Turbulence: Island-Merger Picture with Kinetic Effects

Yangyang Cai, Hongzhe Zhou and Yosuke Mizuno

Magnetic inverse transfer is often invoked to connect small-scale magnetic-field generation to larger coherence scales in high-energy and cosmological plasmas. The underlying magnetohydrodynamic (MHD) arguments combine two logically distinct ingredients: a bulk quantity that is asymptotically conserved in the limit of small resistivity, and a time scale determined by the decay dynamics. In this work, we explore whether this scenario still holds in decaying nonhelical turbulence formed by collisionless plasmas using particle-in-cell simulations. The simulations approximately satisfy $B^2\xi_B^2\simeq{\rm const}$ as in the MHD case, and the fitted exponents in $B^2\propto t^{-p}$ and $\xi_B\propto t^q$ obey $p\simeq2q$. Here $B^2\equiv\langle B_x^2+B_y^2\rangle$ is the average in-plane magnetic energy density, and $\xi_b$ is the magnetic integral scale. However, the decay time scale differs from the MHD case as inferred from the decay exponents. We found $p<1$ and $q<1/2$ in all cases with different initial magnetization $\sigma_0$, with both exponents lower than the MHD values and varying systematically with $\sigma_0$. The spectral peak also migrates toward lower wavenumber at a rate faster than the growth of $\xi_B$, indicating a broken self-similarity. The broken self-similarity is attributed to the appearance of kinetic scales in the magnetic energy spectrum due to pressure anisotropy and Larmor-scale magnetic structures. These results indicate that in astrophysical collisionless plasmas, including but not restrict to solar wind, pulsar-wind nebulae, interstellar medium, and cosmological plasmas, magnetic coherence can continue to grow by inverse transfer, but extrapolations based on MHD decay-time scaling can overestimate the rate of large-scale field growth.
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High Energy Astrophysical Phenomena

Distinct Velocity Components in the Absorption Lines of the Neutron Star X-ray Binary AX J1745.6-2901

Kai Matsunaga, Maxime Parra, Yutaro Nagai et al. (+10 more)

Accretion disks in X-ray binaries regulate mass transfer onto compact objects and drive radiative and kinetic feedback to their surroundings. Here we report X-ray spectroscopy of the eclipsing neutron star low-mass X-ray binary AX J1745.6-2901 with XRISM/Resolve. The phase-averaged Fe XXVI Ly{\alpha} absorption profile exhibits two absorption minima with relative depths that are inconsistent with the theoretical Ly{\alpha}1/Ly{\alpha}2 doublet ratio expected from a single velocity component. We demonstrate that this profile is well described by two discrete velocity components: a blueshifted component at v~ -160 km/s and a redshifted component at v ~ +590 km/s. The significance of the redshifted component is more than 3 sigma based on a Monte-Carlo calculation. This velocity structure persists across orbital phases, disfavoring a localized origin such as a bulge or dip. The blueshifted component, well below the outer-disk escape velocity, is consistent with a slow outflow or disk atmosphere. The redshifted absorber can be explained either by infalling gas from a failed wind or by a gravitational redshift, and the present data cannot rule out either possibility. Regardless of its origin, the redshifted component is kinematically separate from the disk atmosphere and outflow. The absence of absorption at intermediate velocities further indicates a genuinely bimodal velocity distribution rather than the two ends of a single continuous flow, offering a new view of the absorbing-gas kinematics.
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All authors Kai Matsunaga, Maxime Parra, Yutaro Nagai, Teruaki Enoto, Yoshitomo Maeda, Takayuki Hayashi, Shifra Mandel, Kaya Mori, Hideki Uchiyama, Masayoshi Nobukawa, Hiroya Yamaguchi, Megumi Shidatsu, Ryota Tomaru