Astrophysics of Galaxies
The Spatial Distribution of Intra-Cluster Globular Clusters in the Fornax Cluster
Raffaele D'Abrusco, Marco Mirabile, Michele Cantiello et al. (+6 more)
We investigate the spatial distribution of the Intra-Cluster Globular Clusters (ICGCs) detected in the core of the Fornax
galaxy cluster. By separately modeling different components of the observed population of Globular Clusters (GCs), we confirm the existence of an abundant ICGCs over-density with a geometrically complex, elongated morphology roughly centered on the cluster dominant
galaxy NGC 1399 and stretching along the E-W direction. We identify several areas in the ICGCs distribution that deviate from a simple elliptical model and feature large density enhancements. These regions are characterized based on their statistical significance, GCs excess number, position, size and location relative to the
galaxies in their surroundings. The relations between the spatial distribution and features of the ICGCs structures, mostly populated by blue GCs, and properties of the intra-cluster light and
dwarf galaxies detected in the core of the Fornax cluster are described and discussed. The line-of-sight velocity distribution of spectroscopically confirmed GCs within the ICGCs structures is compatible with the systemic velocities of nearby bright
galaxies in the Fornax cluster, suggesting that the ICGCs population is at least partially composed of GCs stripped from their hosts. We argue that the findings here presented suggest that, on sub-cluster scales, different mechanisms contribute to the growth of the ICGC. The western region of Fornax is likely associated with old merging events that predate the assembly of the Fornax cluster. The eastern side instead points to a mix of
tidal disruption of
dwarf galaxies and stripping from the GCSs of massive hosts, more typical of relaxed, high-density cluster environments.
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All authors Raffaele D'Abrusco, Marco Mirabile, Michele Cantiello, Enrica Iodice, Avinash Chaturvedi, Michael Hilker, Giuseppina Fabbiano, Marilena Spavone, Maurizio Paolillo
Earth and Planetary Astrophysics
Exoplanet climate characterization with transit asymmetries – A comprehensive population study from the optical to the infrared
Ludmila Carone, Christiane Helling, Sebastian Gernjak et al. (+2 more)
Space missions (CHEOPS, JWST, PLATO) facilitate detailed characterization of
exoplanets. This work provides a framework to characterize cloud and
climate properties of close-in gas
giants via transit depth asymmetries from the optical to the infrared (0.33 ...10 $\mu$m). The AFGKM ExoRad 3D GCM grid provides gas temperature profiles for an ensemble of 50 tidally locked gaseous
planets orbiting diverse host
stars. It is combined with a detailed kinetic cloud formation model. The end result is a set of synthetic transit spectra and evening-to-morning transit asymmetries that span
climate regimes: warm (T=800 K ... 1000K), intermediately hot (T=1200 K ... 2000 K) and ultrahot (T =2200 K ... 2600 K). WASP-39b observations suggest iron-free clouds with less abundant cloud condensation
nuclei than previously expected. The ensemble study shows that clouds increase transit limb differences due to asymmetries in cloud coverage and by enhancing horizontal differences in the gas temperatures. For hot
planets, evening-to-morning differences of up to 150 ppm are suggested in the optical and 100 ppm in the infrared (2-8 micron). For ultra-hot Jupiters, evening-to-morning transit differences are dominated by the morning cloud for a cloud-free evening limb: They are strongly negative in the PLATO band (0.5-1~$\mu$m, -500 ppm), moderately negative in the near-infrared (1-1.5~$\mu$m, -200 ppm) and moderately positive (+100 ppm) for $\lambda > 2\mu$m. For a partly cloudy evening terminator, the evening-to-morning transit asymmetry is moderately positive in the whole wavelength range. Warm Jupiter
planets exhibit negligible transit asymmetries. PLATO and JWST transit asymmetry observations between 1-2 $\mu$m are optimal to characterize cloudy planetary atmospheres around K -A
stars. JWST observations are most effective for M
star planets with transit differences > +500 ppm for 8-10 $\mu$m.
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All authors Ludmila Carone, Christiane Helling, Sebastian Gernjak, Hanna Leitner, Tamara Janz
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
General Framework for the Spontaneous Scalarization of Regular Black Holes
Ernesto Contreras, Mikaela Carrasco-Hidalgo, Pedro Bargueño et al. (+1 more)
We investigate the spontaneous scalarization of generic, static, and spherically symmetric regular black holes supported by nonlinear electrodynamics. Starting from an arbitrary seed metric, we employ the P-dual formalism to reconstruct the electromagnetic sector and subsequently couple a real scalar field nonminimally. As a worked example, we apply the framework to the regular Balart-Vagenas black hole, showing that scalarized and scalar-free branches can coexist in a region where the scalarized configurations are entropically preferred. We further assess possible observational imprints, finding percent-level deviations in both the shadow size and the fundamental scalar quasi-normal modes ($< 10\%$ for small charge-to-mass ratios), indicating that current electromagnetic and gravitational-wave observations do not rule out these solutions. Our construction thus provides a general route to explore scalarization on top of nonlinear-electrodynamics-supported spacetimes, extending beyond specific Reissner-Nordström-like cases.
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All authors Ernesto Contreras, Mikaela Carrasco-Hidalgo, Pedro Bargueño, Arthur G. Suvorov
Instrumentation and Methods for Astrophysics
Cosmic Ray Detection and Rejection for CSST
Yan Yu, Bin Ma, Tianmeng Zhang et al. (+2 more)
As a space
telescope, the China Space Station Survey
Telescope (CSST) will face significant challenges from
cosmic ray (CR) contamination. These CRs will severely degrade image quality and further influence scientific analysis. Due to the CSST's sky survey strategy, traditional multi-frame stacking methods become invalid. The limited revisits prompted us to develop an effective single-image CR processing method for CSST. We retrained the DeepCR model based on CSST simulated images and achieved 97.90+-0.18% recall and 98.67+-0.05% precision on CR detection. Moreover, this paper puts forward an innovative morphology-sensitive inpainting method, which focuses more on areas with higher scientific value. We trained a UNet++ model especially on contaminated
stellar/
galactic areas, alongside adaptive median filtering for background regions. This method achieves effective for CRs with different intensities and different distances from centers of scientific targets. By this approach, the photometric errors of CR-corrected targets could be restricted to the level comparable to those of uncontaminated sources. Also, it increases the detection rate by 13.6% compared to CR masking. This method will provide a robust CR mitigation for next-generation space
telescopes.
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All authors Yan Yu, Bin Ma, Tianmeng Zhang, Yi Hu, Yajie Zhang
Solar and Stellar Astrophysics
Apsidal motion in massive binaries
Sophie Rosu
One of the most efficient and reliable observational technique allowing to probe the internal structure of a
star is the determination of the apsidal motion in close eccentric binaries. This secular precession of the binary orbit's major axis depends on the
tidal interactions occurring between the two
stars. Its rate is directly related to the internal structure of the
stars, in particular their inner density profile. Combining radial velocity and light curve data over a long timescale, the apsidal motion rate can be constrained, together with the fundamental parameters of the
stars. Confrontation of observational parameters to
stellar models then allows us to constrain the internal structure of
stars. This powerful technique has been known for years but has been seldom applied to massive
stars. I highlight its interest and reveal recent results concerning several massive binaries. While standard
stellar models predict
stars having a smaller internal
stellar structure constant, that is to say,
stars having a smaller density contrast, than expected from observations, I demonstrate that the addition of mixing inside the models helps to solve, at least partially, this discrepancy. Studies with the non-perturbative code MoBiDICT showed that the perturbative model assumption is not justified in highly distorted
stars, in which cases the apsidal motion is underestimated, exacerbating even more the need for enhanced mixing inside the models. But what happens if the binary is a double-line spectroscopic but non-eclipsing binary? In that case, we indeed have no estimate of the masses and radii of the
stars. Surprisingly, the apsidal motion equations combined with the binary' spectroscopic observations allow us to derive the masses of the
stars, in a model-dependent way. Rodolfo Barbá contributed to the development of this original method that I bring out.
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Solar and Stellar Astrophysics
Origin of Joy's Law in the context of Near-Surface Convection on the Sun
Hannah Schunker and Asha Lakshmi K V
Joy's law is a well-established statistical property of
solar active regions that any theory of active region emergence must explain. This tilt angle of the active region away from an east-west
alignment is a critical component for converting the toroidal
magnetic field to poloidal
magnetic field in some leading dynamo theories, and observations show they are important for the reversal of the sign of the global
solar magnetic dipole. This review aims to synthesise observational results related to the onset of Joy's law, placing them within the broader context that describes active region emergence as a largely passive process occurring near the surface of the Sun.
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Solar and Stellar Astrophysics
Populations of tidal and pulsating variables in eclipsing binaries
Alex Kemp, Jasmine Vrancken, Joey S. G. Mombarg et al. (+4 more)
In this work, we seek to characterise a large sample of 14377 main sequence eclipsing binaries in terms of their
stellar, asteroseismic, and orbital properties. We conduct manual vetting on a 4000-target subset of our full 14377-target sample to identify targets with pressure or
gravity modes. We infer
stellar properties including the mass, convective core mass, radius, and central H fraction for the primary using
Gaia Data Release 3 effective temperature and luminosity estimates and a grid of asteroseismically calibrated
stellar models. We use surface brightness ratio and radius ratio estimates from previous eclipse analysis to study the effect of binarity on our results. Our manual vetting identifies 751 candidate g-mode pulsators, 131 p-mode pulsators, and a further 48 hybrid pulsators. The inferred
stellar properties of the hybrid and p-mode pulsators are highly correlated, while the orbital properties of the hybrid pulsators align best with the g-mode pulsators. The g-mode pulsators themselves show a distribution that peaks around the classical g dor instability region but extends continuously towards higher masses, with no detectable divide between the classical g dor and SPB instability regions. There is evidence at the population level for a heightened level of
tidal efficiency in
stars showing g-mode or hybrid variability. Correcting the primary mass inference for binarity based on eclipse measurements of the surface brightness and radius ratios results in a relatively small shift towards lower masses. This work provides a working initial characterisation of this sample from which more detailed analyses folding in asteroseismic information can be built. It also provides a foundational understanding of the limitations and capabilities of this kind of rapid, scalable analysis that will be highly relevant in planning the exploitation of future large-scale binary surveys.
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All authors Alex Kemp, Jasmine Vrancken, Joey S. G. Mombarg, Luc IJspeert, Mykyta Kliapets, Andrew Tkachenko, Conny Aerts
Instrumentation and Methods for Astrophysics
Derivative-Aligned Anticipation of Forbush Decreases from Entropy and Fractal Markers
Juan D. Perez-Navarro and D. Sierra-Porta
We develop a feature-based framework to anticipate Forbush decreases in one-minute
neutron-monitor records by tracking sliding-window invariants from information theory, scaling, and geometry. For each station we compute marker time series, including Shannon, spectral, approximate and sample
entropy; Lempel-Ziv complexity; correlation dimension; and Higuchi and Katz fractal dimensions. Markers are smoothed with an exponentially weighted moving average and analyzed through within-station standardized first differences. Timing is referenced to an operational
alignment time defined as the minimum of the smoothed count first difference, and marker leads are reported in minutes (negative values indicate anticipation). Station-level detectability is evaluated on a pre-
alignment window using a robust z-score detector with bilateral threshold and persistence, without cross-correlation or hypothesis testing. We apply the pipeline to two FD episodes with broad station coverage (2023-04-23 and 2024-05-10; 28 stations each). Across events, a compact CORE panel shows consistently high detection rates and predominantly anticipatory lead distributions, with typical median leads on the order of several hours depending on the invariant and event. Lead dispersion across stations is substantial, with interquartile ranges commonly spanning a few hours, highlighting the need for station-wise criteria and distributional summaries rather than single-station inference. Representative marker trajectories confirm that early flagging corresponds to sustained pre-
alignment excursions in marker differences, not tabulation artifacts. The approach is reproducible from open code, operates on native station units without cross-station homogenization, and remains qualitatively stable under sensitivity sweeps of windowing, smoothing, and detector parameters.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Systematic study of scalar, vector, and mixed density dependencies in relativistic mean-field descriptions of hyperonic matter in neutron stars
Aprajita Shrivastava, Prasanta Char, Sakshi Gautam et al. (+1 more)
We investigate the equation of state (EOS) of hyperonic
neutron star (NS) matter within a density-dependent relativistic mean-field (DDRMF) framework. The effects of scalar, vector, and mixed density dependencies in
meson-
baryon couplings are systematically examined along with alternative forms of the $\rho$-
meson coupling. Several
meson-nucleon parameter sets are explored here for the first time for
neutron stars and compared with the standard DD2 EOS. Most new parameterizations produce stiffer EOSs, leading to
neutron stars with larger radii and higher
tidal deformabilities. However, the inclusion of $\Lambda$ hyperons softens these EOSs, and the resulting maximum masses still satisfy the two
solar mass limits and agree with NICER measurements. These results highlight the importance of exploring alternative density dependencies in constraining dense matter through multi-messenger observations.
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All authors Aprajita Shrivastava, Prasanta Char, Sakshi Gautam, Sarmistha Banik
Solar and Stellar Astrophysics
Velocity field of an Active Region filament from GRIS IR He I and IRIS UV observations
M. Murabito, V. Andretta, S. Parenti et al. (+4 more)
Plasma flow measurements in
solar active region filaments are rare, particularly in the infrared and ultraviolet ranges that probe the chromosphere and transition region. In addition, previous studies generally focused on prominences and filaments near the
solar limb. This study presents a multi-wavelength, multi-instrument analysis of an active region filament observed on the
solar disk on November 9 and 10, 2020. Our goal is to characterize the
plasma flows in the filament using spectroscopic measurements in both the infrared and ultraviolet spectral ranges. This is important for understanding the mechanisms for filament support, mass loading, and energy balance. Furthermore, this also offers observational
benchmarks for filament modeling and simulations. Spectra from the IRIS satellite, including the Mg II k, C II and Si IV lines were analyzed alongside ground-based observations from the GREGOR Infrared Spectrograph and High-resolution Fast Imager instruments whose observed spectral ranges include the chromospheric He I and H{\alpha} lines. Persistent blueshifts were measured within the filament structure in both spectral ranges. These can be interpreted as upflow velocities ranging from 0.5 to 15 km s^-1, with the Si IV showing the highest values. Red shifted emission in the He I and Mg II k3 at the footpoints of a newly formed dark bundle suggest chromospheric downflows, likely due to spatial overlap between an arch filament system close to the filament footpoints. The weak redshifted signal in the Si IV emission may suggest confinement to lower atmospheric layers. The observed velocity patterns provide, for the first time, a comprehensive and coherent view of the
plasma dynamics from the chromosphere to the transition region, illustrating that the filament emission is consistently blueshifted in all the spectral windows, and thus in different temperature regimes.
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All authors M. Murabito, V. Andretta, S. Parenti, C. Kuckein, S. J. Gonzàlez Manrique, S. M. Lezzi, S. L. Guglielmino
High Energy Astrophysical Phenomena
On the nature and Galactic origin of the Be binary MWC 656. New insights from VLA, Gaia, and Fermi-LAT
Sergio A. Dzib and Frederic Jaron
The binary
star MWC 656 was initially proposed as the first confirmed system composed of a Be
star and a black hole. However, recent studies have challenged this interpretation, suggesting that the compact companion is unlikely to be a black hole. In this study, we revisit the nature of MWC 656 by analyzing archival data across multiple wavelengths, including
radio observations from the VLA, optical astrometry from the
Gaia satellite, and high-energy $\gamma$-ray data from the
Fermi-LAT. Using all available VLA observations at X-band (8.0-12.0 GHz), we produce the deepest
radio map toward this system to date, with a noise level of 780 nJy beam$^{-1}$. The source MWC 656 is detected with $S_\nu=4.6\pm0.8\mu$Jy and a spectral index of $\alpha=1.2\pm1.8$, derived by sub-band imaging. The
radio and X-ray luminosity ratio of MWC 656 is consistent with both the fundamental plane of accreting black holes and with the Güdel-Benz relation for magnetically active
stars, leaving the emission mechanism ambiguous. The optical astrometric results of MWC 656 indicate a peculiar velocity of $11.2\pm2.3$ km s$^{-1}$, discarding it as a runaway
star. Its current location, 442 pc below the
Galactic plane, implies a vertical travel time incompatible with the lifetime of a B1.5-type
star. Moreover, the agreement between observed and expected motion in all three velocity components argues against a deceleration scenario, suggesting that MWC 656 likely formed in situ at high
Galactic latitude. We carried out maximum likelihood analysis of
Fermi-LAT data, but cannot report a significant detection of $\gamma$-ray emission from this source. These results reinforce recent evidence that challenge the black hole companion interpretation, and favor a non-BH compact object such as a white
dwarf or
neutron star.
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Cosmology and Nongalactic Astrophysics
Galaxy assembly bias in cosmological hydrodynamical simulations: a comparison between SIMBA and IllustrisTNG
Hong-Gang Yang, Marcos Pellejero, John Peacock et al. (+1 more)
Modelling of large-scale structure is increasingly concerned with
galaxy assembly bias (GAB), the dependence of
galaxy clustering on quantities other than
halo mass. We investigate how baryonic physics affects the strength and
redshift evolution of GAB using the largest runs of two state-of-the-art cosmological hydrodynamical simulations: SIMBA and IllustrisTNG. We quantify GAB by comparing the clustering of
stellar-mass-selected
galaxies to that of shuffled samples, where
galaxies are randomly reassigned to
haloes of similar mass. We find that GAB in both simulations increases from approximately zero at $z=5$ to a $\sim\,5\%$ change in clustering amplitude at $z=2$. After this epoch, the trends diverge: GAB in TNG continues to increase, reaching $\sim\,10\%$ at $z=0$, while in SIMBA it decreases to nearly zero. By further shuffling
galaxies within bins of
halo mass and
cosmic environment – characterised by smoothed matter overdensity ($\delta_5$) and
tidal anisotropy ($\alpha_5$) – we show that most of the GAB in both simulations can be attributed to the overdensity, while
tidal anisotropy contributes negligibly in both simulations. Exploring this effect from the point of view of the
halo occupation distribution (HOD), we find that numbers of central and satellite
galaxies vary with overdensity – but only near the respective turn-on masses for these two constituents: the
galaxy contents of high-mass
haloes are very nearly independent of environment. We present a simple parameterisation that allows the HOD modelling to be modified to reflect this form of density-dependent GAB.
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All authors Hong-Gang Yang, Marcos Pellejero, John Peacock, Romeel Davé
Earth and Planetary Astrophysics
Chasing the storm: Investigating the application of high-contrast imaging techniques in producing precise exoplanet light curves
Ben J. Sutlieff, David S. Doelman, Jayne L. Birkby et al. (+10 more)
Substellar companions such as
exoplanets and brown
dwarfs exhibit changes in brightness arising from top-of-atmosphere inhomogeneities, providing insights into their atmospheric structure and dynamics. This variability can be measured in the light curves of high-contrast companions from the ground by combining differential spectrophotometric monitoring techniques with high-contrast imaging. However, ground-based observations are sensitive to the effects of
turbulence in Earth's atmosphere, and while adaptive optics (AO) systems and bespoke data processing techniques help to mitigate these, residual systematics can limit photometric precision. Here, we inject artificial companions to data obtained with an AO system and a vector Apodizing Phase Plate coronagraph to test the level to which telluric and other systematics contaminate such light curves, and thus how well their known variability signals can be recovered. We find that varying companions are distinguishable from non-varying companions, but that variability amplitudes and periods cannot be accurately recovered when observations cover only a small number of periods. Residual systematics remain above the
photon noise in the light curves but have not yet reached a noise floor. We also simulate observations to assess how specific systematic sources, such as non-common path aberrations and AO residuals, can impact aperture photometry as a companion moves through pupil-stabilised data. We show that only the lowest-order aberrations are likely to affect flux measurements, but that thermal background noise is the dominant source of scatter in raw companion photometry. Predictive control and focal-plane wavefront sensing techniques will help to further reduce systematics in data of this type.
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All authors Ben J. Sutlieff, David S. Doelman, Jayne L. Birkby, Matthew A. Kenworthy, Jordan M. Stone, Frans Snik, Steve Ertel, Beth A. Biller, Charles E. Woodward, Andrew J. Skemer, Jarron M. Leisenring, Alexander J. Bohn, Luke T. Parker
High Energy Astrophysical Phenomena
Search for neutrino emission from blazar $\gamma$-ray flares accounting for possible neutrino time delays
Egor Podlesnyi and Foteini Oikonomou
We report the results of the search for the high-energy
neutrino emission associated with blazar
flares, accounting for a possible lag of
neutrinos with respect to the electromagnetic emission, either due to the slowness of the
proton energy losses in $p\gamma$ collisions and/or
proton acceleration. We perform two tests, cross-matching
neutrinos with energies $E_{\nu} \gtrsim 100$ TeV from the public catalogue of
neutrino alerts IceCat-1 with active
galactic nuclei from two source samples based on 1) the MOJAVE database and 2) the CGRaBS catalogue, and utilising
Fermi-LAT light curves from the public light curve repository. We scan over a wide range of values of the jet-frame time delay $t^{\prime}_{\mathrm{delay}}$ between the
neutrino arrival and the time of the prior major $\gamma$-ray
flare and find a pre-trial $\sim 2\sigma$ correlation at $t^{\prime}_{\mathrm{delay}} \sim 10^{3}$ d, which is consistent ($p_{\mathrm{post-trial}} \sim 0.1$) with expectations under the null hypothesis after trial correction.
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High Energy Astrophysical Phenomena · Cross-listed from cs.LG
MiniFool – Physics-Constraint-Aware Minimizer-Based Adversarial Attacks in Deep Neural Networks
Lucie Flek, Oliver Janik, Philipp Alexander Jung et al. (+8 more)
In this paper, we present a new
algorithm, MiniFool, that implements physics-inspired
adversarial attacks for testing neural network-based classification tasks in particle and astroparticle physics. While we initially developed the
algorithm for the search for astrophysical tau
neutrinos with the IceCube
Neutrino Observatory, we apply it to further data from other science domains, thus demonstrating its general applicability. Here, we apply the
algorithm to the well-known MNIST data set and furthermore, to Open Data data from the CMS experiment at the Large
Hadron Collider. The
algorithm is based on minimizing a cost function that combines a $\chi^2$ based test-statistic with the deviation from the desired target score. The test statistic quantifies the probability of the perturbations applied to the data based on the experimental uncertainties. For our studied use cases, we find that the likelihood of a flipped classification differs for both the initially correctly and incorrectly classified events. When testing changes of the classifications as a function of an attack parameter that scales the experimental uncertainties, the robustness of the network decision can be quantified. Furthermore, this allows testing the robustness of the classification of unlabeled experimental data.
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All authors Lucie Flek, Oliver Janik, Philipp Alexander Jung, Akbar Karimi, Timo Saala, Alexander Schmidt, Matthias Schott, Philipp Soldin, Matthias Thiesmeyer, Christopher Wiebusch, Ulrich Willemsen
Earth and Planetary Astrophysics
Experiments reveal extreme water generation during planet formation
Francesca Miozzi, Anat Shahar, Edward D. Young et al. (+7 more)
The most abundant type of
planet discovered in the
Galaxy has no analogue in our
Solar System and is believed to consist of a rocky interior with an overlying thick H2 dominated envelope. Models have predicted that the reaction between the atmospheric hydrogen and the underlying magma ocean can lead to the production of significant amounts of water. The models suffer however from the current lack of experimental data on the reaction between hydrogen and silicate melt at high pressures and temperatures. Here we present novel experimental results designed to investigate this interaction.
Laser heating diamond anvil
cell experiments were conducted between 16 and 60 GPa at temperatures above 4000 K. We find that copious amounts of hydrogen dissolve into the silicate melt with a large dependence on temperature rather than pressure. We also find that the reduction of iron
oxide leads to the production of significant amounts of water along with the formation of iron-enriched blebs. Altogether, the results predict that the typical processes attending
planet formation will result in significant water production with repercussions for the chemistry and structure of the planetary interior as well as the atmosphere.
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All authors Francesca Miozzi, Anat Shahar, Edward D. Young, Jianhua Wang, Andrew Steele, Stephan Borensztajn, Suzy M. Vitale, Emma S. Bullock, Nicolas Wehr, James Badro
Astrophysics of Galaxies
BALNet: Deep Learning-Based Detection and Measurement of Broad Absorption Lines in Quasar Spectra
Yangyang Li, Zhijian Luo, Shaohua Zhang et al. (+5 more)
Broad absorption line (BAL)
quasars serve as critical probes for understanding active
galactic nucleus (AGN)
outflows, black hole
accretion, and
cosmic evolution. To address the limitations of manual classification in large-scale spectroscopic surveys - where the number of
quasar spectra is growing exponentially - we propose BALNet, a deep learning approach consisting of a one-dimensional convolutional neural network (1D-CNN) and bidirectional long short-term
memory (Bi-LSTM) networks to automatically detect BAL troughs in
quasar spectra. BALNet enables both the identification of BAL
quasars and the measurement of their BAL troughs. We construct a simulated
dataset for training and testing by combining non-BAL
quasar spectra and BAL troughs, both derived from SDSS DR16 observations. Experimental results in the testing set show that: (1) BAL trough detection achieves 83.0% completeness, 90.7% purity, and an F1-score of 86.7%; (2) BAL
quasar classification achieves 90.8% completeness and 94.4% purity; (3) the predicted BAL velocities agree closely with simulated ground truth labels, confirming BALNet's robustness and accuracy. When applied to the SDSS DR16 data within the
redshift range 1.5<z<5.7, at least one BAL trough is detected in 20.4% of spectra. Notably, more than a quarter of these are newly identified sources with significant absorption, 8.8% correspond to redshifted systems, and some narrow/weak absorption features were missed. BALNet greatly improves the efficiency of large-scale BAL trough detection and enables more effective scientific analysis of
quasar spectra.
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All authors Yangyang Li, Zhijian Luo, Shaohua Zhang, Du Wang, Jianzhen Chen, Zhu Chen, Hubing Xiao, Chenggang Shu
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Analytical sensitivity curves of the second-generation time-delay interferometry
Chunyu Zhang
Forthcoming space-based gravitational-wave (GW) detectors will employ second-generation time-delay interferometry (TDI) to suppress
laser frequency noise and achieve the sensitivity required for GW detection. We introduce an inverse light-path operator $\mathcal{P}_{i_{1}i_{2}i_{3}\ldots i_{n-1}i_{n}}$, which enables simple representation of second-generation TDI combinations and a concise description of light propagation. Under the instantaneous equal-arm, equilateral triangular-constellation approximation, analytical expressions and high-accuracy approximate formulas are derived for the sky- and polarization-averaged response functions, noise power spectral densities (PSDs), and sensitivity curves of TDI Michelson, Sagnac-type ($\alpha,\beta,\gamma$), Monitor, Beacon, Relay, and fully symmetric Sagnac ($\zeta$) combinations, as well as their orthogonal $A, E, T$ channels. The validity of the analytical results is confirmed via Monte Carlo integration with $10^{4}$ randomly sampled sky locations and polarization angles. Our results show that: (i) second-generation TDIs have the same sensitivities as their first-generation counterparts; (ii) the $A, E, T$ sensitivities and the optimal sensitivity are independent of the TDI generation and specific combination; (iii) the $A$ and $E$ channels have equal averaged responses, noise PSDs, and sensitivities, while the $T$ channel has much weaker response and sensitivity at low frequencies; (iv) except for the $(\alpha,\beta,\gamma)$ and $\zeta$ combinations and the $T$ channel, all sensitivity curves exhibit a flat section; (v) the averaged response, noise PSD, and sensitivity of $\zeta$ scale with those of the $T$ channel. These analytical and approximate formulations provide useful equal-arm
benchmarks for instrument optimization and data-analysis preparatory studies for future space-based GW detectors.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Black holes in a dense infinite medium: a toy-model regularizing the Schwarzschild metric
Aurélien Barrau, Killian Martineau and Hanane Zelgoum
We revisit the dynamics of a black hole accreting energy from a surrounding homogeneous and infinite space. We argue for a simple heuristic modification of the Schwarzschild approximation when the density of the medium is not negligible anymore. The resulting behavior is drastically modified: the mass divergence at finite time is cured and the thermodynamical properties are deeply changed. Some potential consequences for
quantum gravity and bouncing models are also pointed out. Those conclusions being mostly obtained from a Newtonian approach, they only aim at guiding toward a more rigorous treatment. Still, interestingly, the behavior is far more convincing that the one usually obtained.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
U-spin symmetry energy and hyperon puzzle in $\Lambda$-admixed neutron stars
Hao-Song You, Ting-Lan Yu, Sophia Han et al. (+2 more)
By combining the ($u$,$d$) I-
spin doublets or ($d$,$s$) U-
spin doublets, the SU(3)
flavor symmetry of light
quarks can be decomposed into SU(2)$_I\times$U(1)$_Y$ or SU(2)$_U\times$U(1)$_Q$ subgroups, which have been widely adopted to categorize
hadrons and their decay properties. The standard I-
spin counterpart for the interactions among nucleons, namely the
nuclear symmetry energy $E_\mathrm{sym}(n_\mathrm{b})$, characterizes the variation of binding energy as the
neutron to
proton ratio in a
nuclear system. We propose the U-
spin symmetry energy $E_\mathrm{U}(n_\mathrm{b})$ for hyperonic matter to characterize the variation of binding energy with the inclusion of hyperons. In particular, we include $\Lambda$ hyperons in dense matter and neglect contributions from other hyperons, then constrain $E_\mathrm{U}(n_\mathrm{b})$ using
nuclear physics and astrophysical observations through a
Bayesian inference approach. Our results show that $E_\mathrm{U}(n_\mathrm{b})$ is much smaller than 9$E_\mathrm{sym}(n_\mathrm{b})$, indicating a substantially weaker dependence of the adopted binding energy functional on the U-
spin asymmetry than on the corresponding I-
spin asymmetry. Consequently, the $\Lambda$ hyperon potential increases significantly with density and becomes repulsive at higher densities, leading to more than 50% probability for the emergence of $\Lambda$ hyperons in the posterior, which are likely to vanish again at densities $n_\mathrm{b} \gtrsim 5\,n_0$. In scenarios where $\Lambda$ hyperons do emerge, the onset density $n_{\mathrm{b}}^\Lambda$ typically falls in the range $2\,n_0$–$5\,n_0$, corresponding to central densities of
neutron stars more massive than $1.0\,\rm{M_\odot}$.
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All authors Hao-Song You, Ting-Lan Yu, Sophia Han, Cheng-Jun Xia, Ren-Xin Xu
Cosmology and Nongalactic Astrophysics
Fast End-to-End Framework for Cosmological Parameter Inference from CMB Data Using Machine Learning
Larissa Santos, Camila P. Novaes, Elisa G. M. Ferreira et al. (+1 more)
Precise estimation of cosmological parameters from the
cosmic microwave background (CMB) remains a central goal of modern cosmology and a key test of inflationary physics. However, this task is fundamentally limited by strong foreground contamination, primarily from
Galactic emissions, which obscure the faint CMB B-mode polarization signal. In this Letter, we introduce a fast, simulation-based, end to end pipeline that integrates a robust component separation technique with machine-learning, leading to cosmological parameter estimation. Our approach combines the Analytical Blind Separation (ABS) method for foreground removal with a neural network (NN) framework optimized to extract cosmological parameters directly from full-sky simulations. We assess the performance of this methodology for the forthcoming LiteBIRD and PICO satellite missions, designed to detect CMB B modes with unprecedented sensitivity. Applying the pipeline to realistic sky simulations, we obtain 1 sigma errors of 0.0035 (LiteBIRD) and 0.0030 (PICO) for the optical depth tau, and 0.005 (LiteBIRD) and 0.0014 (PICO) for the tensor-to-scalar ratio, r. In all cases, the recovered parameters are consistent with input values within 1 sigma across most of the parameter space. Results for LiteBIRD are in excellent agreement with the latest forecasts from the collaboration. Our findings establish this combined ABS-NN pipeline as a competitive, accurate, and computationally efficient alternative for cosmological parameter inference, offering a powerful framework for forthcoming CMB experiments.
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All authors Larissa Santos, Camila P. Novaes, Elisa G. M. Ferreira, Carlo Baccigalupi
Astrophysics of Galaxies
The ALMA-QUARKS survey: Hot Molecular Cores are a long-standing phenomenon in the evolution of massive protostars
Dezhao Meng, Tie Liu, Jarken Esimbek et al. (+34 more)
We present an analysis of the
QUARKS survey sample, focusing on protoclusters where Hot Molecular Cores (HMCs, traced by CH3CN(12–11)) and UC HII regions (traced by H30\alpha/H40\alpha) coexist. Using the high-resolution, high-sensitivity 1.3 mm data from the
QUARKS survey, we identify 125 Hot Molecular Fragments (HMFs), which represent the substructures of HMCs at higher resolution. From line integrated intensity maps of CH3CN(12–11) and H30\alpha, we resolve the spatial distribution of HMFs and UC HII regions. By combining with observations of CO
outflows and 1.3 mm continuum, we classify HMFs into four types: HMFs associated with jet-like
outflow, with wide-angle
outflow, with non-detectable
outflow, and shell-like HMFs near UC HII regions. This diversity possibly indicates that the hot core could be polymorphic and long-standing phenomenon in the
evolution of massive protostars. The separation between HMFs and H30\alpha/H40\alpha emission suggests that sequential high-mass
star formation within young protoclusters is not likely related to feedback mechanisms.
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All authors Dezhao Meng, Tie Liu, Jarken Esimbek, Sheng-Li Qin, Guido Garay, Paul F. Goldsmith, Jianjun Zhou, Xindi Tang, Wenyu Jiao, Yan-Kun Zhang, Fengwei Xu, Siju Zhang, Anandmayee Tej, Leonardo Bronfman, Aiyuan Yang, Sami Dib, Swagat R. Das, Jihye Hwang, Archana Soam, Yisheng Qiu, Dalei Li, Yuxin He, Gang Wu, Lokesh Dewangan, James O. Chibueze, Pablo García, Prasanta Gorai, Naval Kishor Bhadari, Yong Zhang, Patricio Sanhueza, Yongquan Luo, Jia-Hang Zou, Kee-Tae Kim, Dongting Yang, Lei Zhu, Xunchuan Liu, Macleod Gordon
Earth and Planetary Astrophysics
Limits on forming coreless terrestrial worlds in the TRAPPIST-1 system
Dongyang Huang and Caroline Dorn
With seven temperate Earth-sized
planets revolving around an ultracool red
dwarf, the nearby TRAPPIST-1 system offers a unique opportunity to verify models of
exoplanet composition, differentiation, and interior structure. In particular, the low bulk densities of the TRAPPIST-1
planets, compared to terrestrial
planets in our
solar system, require either substantial amount of volatiles to be present or a corefree scenario where the metallic core is fully oxidised. Here, using an updated metal-silicate partitioning model, we show that during core-mantle differentiation oxygen becomes more siderophile (iron-loving) implying larger
planet radii. For the seven TRAPPIST-1
planets, however, we find that they are not sufficiently large to oxidise all the iron in the core, if they differentiate from an Earth-like composition. Oxygen partitioning in rocky worlds precludes coreless
planets up to about 4 Earth masses. The observed density deficit in the TRAPPIST-1
planets, and more generally in M
dwarf systems if confirmed by future observations, may be explained by system-dependent element budgets during
planet formation, which are intrinsically linked to their
stellar metallicity.
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Astrophysics of Galaxies
Unveiling the distribution and redshift dependence of host galaxy dispersion measures using localized fast radio bursts
Yu Sang and Hai-Nan Lin
Fast
Radio Bursts (FRBs) are enigmatic
radio pulses whose origins are poorly understood. The dispersion measure of host
galaxy (${\rm DM_{host}}$) provides critical insights into the local environment of FRB sources. In this study, we analyze a sample of 117 well-localized FRBs to investigate the statistical properties of ${\rm DM_{host}}$ and its potential correlations with host
galaxy parameters, including
redshift,
stellar mass,
star formation rate (SFR), and
galaxy age. Our results reveal that ${\rm DM_{host}}$ is consistent with a log-normal distribution, with the mean $\mu_{\rm host}=5.03\pm 0.02$ and standard deviation $\sigma_{\rm host} = 0.96\pm 0.03$, which corresponds to a median value ${\rm Med}({\rm DM_{host}})=\exp(\mu_{\rm host})=153\pm 3~{\rm pc~cm^{-3}}$. We find a moderate positive correlation between ${\rm DM_{host}}$ and
redshift, but no statistically significant correlations are found between ${\rm DM_{host}}$ and
stellar mass, SFR, or
galaxy age. Our findings highlight the importance of ${\rm DM_{host}}$ as a diagnostic tool for unraveling FRB origins, and underscore the need for future FRB surveys with deep multiwavelength host
galaxy follow-up.
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Astrophysics of Galaxies
CosmoDRAGoN II: Remnant Radio Galaxies in Group and Cluster Environments
Georgia S.C. Stewart, Stanislav S. Shabala, Ross J. Turner et al. (+5 more)
Radio galaxy remnants are a rare subset of the
radio-loud active
galactic nuclei (RLAGN) population, representing the quiescent phase in the RLAGN lifecycle. Despite their observed scarcity, they offer valuable insights into the AGN duty cycle and feedback processes. Due to the mega-year timescales over which the RLAGN lifecycle takes place, it is impossible to observe the active to remnant transition in real-time. Numerical simulations offer a solution to follow the long-term
evolution of RLAGN
plasma. In this work, we present the largest suite (to date) of three-dimensional, hydrodynamic simulations studying the dynamic
evolution of the active-to-remnant transition and explore the mechanisms driving cocoon
evolution, comparing the results to the expectations of analytic modelling. Our results show key differences between active and remnant sources in both cluster environments and in lower-density group environments. We find that sources in low-density environments can remain overpressured well into the remnant phase. This significantly increases the time for the remnant lobe to transition to a buoyant regime. We compare our results with analytic expectations, showing that the long-term
evolution of
radio remnants can be well captured for remnants whose expansion is largely pressure-driven if the transition to a coasting phase is assumed to be gradual. We find that remnants of low-powered progenitors can continue to be momentum-driven for about 10 Myr after the jets switch-off. Finally, we consider how the properties of the progenitor influence the mixing of the remnant lobe and confirm the expectation that the remnants of high-powered sources have long-lasting shocks that can continue to heat the surrounding medium.
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All authors Georgia S.C. Stewart, Stanislav S. Shabala, Ross J. Turner, Patrick M. Yates-Jones, Martin G. H. Krause, O. Ivy Wong, Chris Power, Martin J. Hardcastle
Solar and Stellar Astrophysics
Discovery of Seven Cold and Distant Brown Dwarfs with JWST RUBIES
Sara J. Morrissey, Adam J. Burgasser, Anna de Graaff et al. (+2 more)
We report near-infrared spectral model fits to seven distant L- and T-type
dwarfs observed with the JWST Near Infrared Spectrograph (NIRSpec) as part of the Red Unknowns: Bright Infrared Extragalactic Survey (RUBIES). Comparison of 0.9-2.5 $\mu$m near-infrared spectra of these sources to spectral standards indicates spectral types spanning L1 to T8 and spectrophotometric distances spanning 800-3,000 pc. Fits to three grids of spectral models yield atmosphere parameters and spectrophotometric distances largely consistent with our classifications, although fits to L
dwarf spectra indicate missing components to the models. Three of our sources have vertical displacements from the
Galactic plane exceeding 1~kpc, and have high probabilities of membership in the
Galactic thick disk population. Of these, the L
dwarf RUBIES-BD-3 (RUBIES-EGS-3081) is well-matched to subdwarf standards, while the early T
dwarf RUBIES-BD-5 (RUBIES-UDS-170428) is best fit by metal-poor atmosphere models; both may be a thick disk or
halo brown
dwarfs. We critically examine the 1-5 $\mu$m spectra of the current sample of 1-2 kpc mid- and late-T
dwarfs, finding that temperature, surface
gravity,
metallicity, and vertical mixing efficiency can all contribute to observed variations in near-infrared spectral structure and the strength of the 4.2 $\mu$m CO band. This work aims to guide ongoing JWST, Euclid, and other space-based spectral surveys that are expected to uncover thousands of low-temperature
stars and brown
dwarfs throughout the Milky Way.
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All authors Sara J. Morrissey, Adam J. Burgasser, Anna de Graaff, Ian McConachie, Gabriel Brammer
Astrophysics of Galaxies
Emanuele Contini, Marilena Spavone, Rossella Ragusa et al. (+2 more)
We study the formation and
evolution of
stellar halos (SHs) around bright central
galaxies (BCGs), focusing on their scaling relations, colors, and
metallicities across
cosmic time, and compare model predictions with ultra–deep imaging data. We use the semianalytic model FEGA25, applied to merger trees from high–resolution dark matter simulations, including an updated treatment of intracluster light (ICL) formation. SHs are defined as the
stellar component within the transition radius, linked to
halo concentration. Predictions are compared with observations from the VST Early-type
GAlaxy Survey (VEGAS) and Fornax Deep Survey (FDS). The SH mass correlates strongly with both BCG and ICL masses, with tighter scatter in the SH–ICL relation. The transition radius peaks at 30–40 kpc nearly independent of
redshift, but can reach $\sim400$ kpc in the most massive
halos, after z=0.5. SHs and ICL show nearly identical color distributions at all epochs, both reddening toward $z=0$. At $z=2$, SHs and the ICL are $\sim0.4$ dex more metal–poor than BCGs, but the gap shrinks to $\sim0.1$ dex by the present time. Observed colors are consistent with model predictions, while observed
metallicities are lower, suggesting a larger contribution from disrupted
dwarfs. SHs emerge as transition regions between BCGs and the ICL, dynamically and chemically coupled to both. Their properties depend on
halo concentration, ICL formation efficiency, and the progenitor mass spectrum. Upcoming wide–field photometric and spectroscopic surveys (e.g. LSST, WEAVE, 4MOST) will provide crucial tests by mapping structure,
metallicity, and kinematics in large
galaxy samples.
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All authors Emanuele Contini, Marilena Spavone, Rossella Ragusa, Enrica Iodice, Sukyoung K Yi
High Energy Astrophysical Phenomena
Strange Matter
Chengjun Xia, Xiaoyu Lai and Renxin Xu
Pulsar-like objects are extremely compact, with an average density that exceeds
nuclear saturation density, where the fundamental strong interaction plays an essential role, particularly in the low-energy regime. The internal structures and properties of those objects are profoundly connected to phenomena such as
supernova explosions, gamma-ray bursts, fast
radio bursts, high/low-mass compact
stars, and even to issues like dark matter and
cosmic rays. However, due to the non-perturbative nature of
quantum chromodynamics, significant uncertainties remain in our current understanding of the composition and equation of state (EOS) for the dense matter inside them. Drawing on three-flavour
symmetry and the strong coupling between light
quarks, this paper presents a novel perspective on the nature of
pulsars: they are actually composed of strange matter, in the form of either strange
quark matter or strangeon (analogous to nucleons and representing multibaryon states with three-flavour
symmetry) matter. As both strange
quark matter and strangeon matter contain non-zero strangeness, we refer to them collectively as “strange matter”, and to the corresponding compact
stars as “strange
stars”. We then briefly introduce several physical models describing strange matter and present the resulting structures and properties of strange
stars. This includes discussions on the EOSs, surface properties, mass-radius relations, glitches, binary compact
star mergers, and dark matter. Furthermore, we will explore how observational properties of
pulsar-like objects support the strange
star model.
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