High Energy Astrophysical Phenomena
Identification of Gamma Ray Pulsar Candidates in the Fermi-LAT 4FGL-DR4 Unassociated Sources Using Supervised Machine Learning
A. Pathania, K. K. Singh, S. K. Singh et al. (+3 more)
The Large Area
Telescope (LAT) on board the
Fermi Gamma-ray Space
Telescope has been continuously providing good quality survey data of the entire sky in the high energy range from 30 MeV to 500 GeV and above since August 2008. A succession of gamma-ray source catalogs is published after a comprehensive analysis of the
Fermi–LAT data. The most recent release of data in the fourth
Fermi–LAT catalog of gamma-ray sources (4FGL-DR4), based on the first 14 years of observations in the energy band 50 MeV-1 TeV, contains 7195 sources. A large fraction ($\sim$ 33%) of this population has no known counterparts in the lower wave bands. Such high energy gamma-ray sources are referred to as unassociated or unidentified. An appropriate classification of these objects into known type of gamma-ray sources such as the active
galactic nuclei or
pulsars is essential for population studies and pointed multi-wavelength observations to probe the radiative processes. In this work, we perform a detailed classification of the unassociated sources reported in the 4FGL-DR4 catalog using two supervised machine learning techniques-Random Forest and Extreme Gradient Boosting. We mainly focus on the identification of new gamma-ray
pulsar candidates by making use of different observational features derived from the long-term observations with the
Fermi–LAT and reported in the incremental 4FGL-DR4 catalog. We also explore the effects of data balancing approach on the classification of the
Fermi–LAT unassociated sources.
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All authors A. Pathania, K. K. Singh, S. K. Singh, A. Tolamatti, B. B. Singh, K. K. Yadav
Instrumentation and Methods for Astrophysics
The Astronomical Plate Digitization at SHAO
Yong Yu, Meiting Yang, Zhengjun Shang et al. (+5 more)
The digitization of historical astronomical plates is essential for preserving century-long observational data. This work presents the development and application of the specialized digitizers at the Shanghai Astronomical Observatory (SHAO), including technical details, international collaborations, and scientific applications on the plates.
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All authors Yong Yu, Meiting Yang, Zhengjun Shang, Liangliang Wang, Jing Yang, Zhenghong Tang, Jianhai Zhao, Massinissa Hadjara
Earth and Planetary Astrophysics
Fragmentation-limited dust filtration in 2D simulations of planet-disk systems with dust coagulation. Parameter study and implications for the inner disk's dust mass budget and composition
Thomas Pfeil, Philip J. Armitage and Yan-Fei Jiang
Super-thermal gas
giant planets or their progenitor cores are known to open deep gaps in protoplanetary disks, which stop large, drifting
dust particles on their way to the inner disk. The possible separation of the disk into distinct reservoirs and the resulting
dust depletion interior to the gap have important implications for planetesimal formation and the chemical and isotopic composition of the inner regions of protoplanetary disks.
Dust fragmentation, however, maintains a reservoir of small grains which can traverse the gap.
Dust evolution models are thus instrumental for studies of a gap's filtration efficiency. We present 2D multifluid hydrodynamic simulations of
planet-disk systems with
dust coagulation and fragmentation. For the first time, we evolve a series of 2D simulation with
dust coagulation over 45000 planetary orbits and track the
dust's size
evolution and origin by using the TriPoD
dust coagulation method. We investigate the effects of different planetary masses, fragmentation velocities, and viscosities on the inner disk's
dust mass budget and composition, and highlight the advantages of multi-dimensional simulations over 1D models. Filtering can only be efficient for high planetary masses, high fragmentation velocities, and low diffusivities. Clear compositional distinctions between the inner and outer disk could not have been maintained by Jupiter's core if the fragmentation velocity was low, even if $\alpha \lesssim 5 \times 10^{-4}$. Significant "contamination" of the inner disk by outer-disk
dust occurs in much less than $2 \times 10^5$ yr in this case and even for more massive objects. This either places tight constraints on the physical conditions in the
Solar nebula or mandates consideration of alternative explanations for the NC-CC dichotomy. Astrophysical constraints on the parameters could discriminate between these possibilities.
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Cosmology and Nongalactic Astrophysics
Reconstructing the local density field with combined convolutional and point cloud architecture
Baptiste Barthe-Gold, Nhat-Minh Nguyen and Leander Thiele
We construct a neural network to perform regression on the local dark-matter density field given line-of-sight peculiar velocities of dark-matter
halos, biased tracers of the dark matter field. Our architecture combines a convolutional U-Net with a point-cloud DeepSets. This combination enables efficient use of small-scale information and improves reconstruction quality relative to a U-Net-only approach. Specifically, our hybrid network recovers both clustering amplitudes and phases better than the U-Net on small scales.
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High Energy Astrophysical Phenomena
Gamma-Ray Spectra of $R$-Process Nuclei
Axel Gross, Samuel Cupp and Matthew R Mumpower
The radioactive decay of unstable
nuclei created in the rapid
neutron capture process releases a large amount of $\gamma$-rays. When the ejecta are optically thick, these $\gamma$-rays may contribute to an associated kilonova. Once transparent, prominent spectral features will be directly observable in current and future $\gamma$-ray detectors. In this work, we study and compare the $\gamma$-ray spectra of different representative $r$-process trajectories across a broad range of timescales, from hours to 50,000 years, identifying the
nuclei which significantly contribute. We discuss these findings in the context of observability, noting that there are several practical challenges to connecting observed signatures to specific
nuclei. However, if these challenges can be overcome, direct observation of $\gamma$-rays from $r$-process sites can provide insight into the fundamental physics underpinning the $r$-process.
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Cosmology and Nongalactic Astrophysics
Cleaning Galactic foregrounds with spatially varying spectral dependence from CMB observations with fgbuster
Arianna Rizzieri, Clément Leloup, Josquin Errard et al. (+1 more)
In the context of maximum-likelihood parametric component separation for next-generation full-sky CMB polarization experiments, we study the impact of fitting different spectral parameters of
Galactic foregrounds in distinct subsets of pixels on the sky, with the goal of optimizing the search for
primordial B modes. Using both simulations and analytical arguments, we highlight how the post-component separation uncertainty and systematic foreground residuals in the cleaned CMB power spectrum depend on spatial variations in the spectral parameters. We show that allowing spectral parameters to vary across subsets of the sky pixels is essential to achieve competitive S/N on the reconstructed CMB after component separation while keeping residual foreground bias under control. Although several strategies exist to define pixel subsets for the spectral parameters, each with its advantages and limitations, we show using current foreground simulations in the context of next-generation space-borne missions that there are satisfactory configurations in which both statistical and systematic residuals become negligible. The exact magnitude of these residuals, however, depends on the mission's specific characteristics, especially its frequency coverage and sensitivity. We also show that the post-component separation statistical uncertainty is only weakly dependent on the properties of the foregrounds and propose a semi-analytical framework to estimate it. On the contrary, the systematic foreground residuals highly depend on both the properties of the foregrounds and the chosen spatial resolution of the spectral parameters.
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All authors Arianna Rizzieri, Clément Leloup, Josquin Errard, Davide Poletti
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Effects of dark dipole radiation on eccentric supermassive black hole binary inspirals
Mu-Chun Chen and Yan Cao
The final-parsec problem has long posed a central challenge in understanding the merger of supermassive black hole binaries. In this paper, we investigate a scenario in which a dark scalar or vector field is sourced by eccentric binaries, leading to accelerated mergers through additional dipole radiation, and thereby extending the range of masses for which the binary can merge within a Hubble time. The Newtonian-order radiation fluxes from an eccentric charged Keplerian binary are derived using general results for localized periodic sources in flat spacetime. We find that dipole radiation, although insufficient to fully resolve the final-parsec problem, can alter the low-frequency spectrum of the
stochastic gravitational-wave background from supermassive black hole binary inspirals. We construct a simplified model for the spectrum and perform a
Bayesian analysis using the current
pulsar timing array data.
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High Energy Astrophysical Phenomena
AT 2018cow at ~5 years: additional evidence for a tidal disruption origin
Anne Inkenhaag, Andrew J. Levan, Andrew Mummery et al. (+1 more)
The Luminous Fast Blue Optical Transient (LFBOT) AT 2018cow is the prototype of its class with an extensive set of multi-wavelength observations. Despite a rich data set there is, still, no consensus about the physical nature and origin of this event. AT 2018cow remained UV bright 2-4 years after the explosion, which points at an additional energy injection source, most likely from an
accretion disk. We present additional late time UV data obtained with the Hubble Space
Telescope, to show there is no significant fading in the optical since the last epoch and only marginal fading in the UV. The new UV data points match the predictions of previously published
accretion disk models, where the disk is assumed to form from the
tidal disruption of a low mass
star by an intermediate mass black hole. This consistency provides evidence that AT 2018cow could indeed be a
tidal disruption event. The marginal decay is in contrast with the predictions of light curves produced by interacting
supernovae. The difference between expectations for disc emission and interacting
supernovae will further increase with time, making data at even later times a route to robustly rule out interaction between
supernova ejecta and circumstellar material.
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All authors Anne Inkenhaag, Andrew J. Levan, Andrew Mummery, Peter G. Jonker
Cosmology and Nongalactic Astrophysics
The dark sector of the Universe as a scalar field in Horndeski Gravity
M. S. Oliveira, F. A. Brito and J. A. V. Campos
In the present work, we study a subclass of Horndeski
gravity characterized by a non-minimal derivative coupling between a scalar field and the Einstein tensor, as a possible alternative to alleviate the observational tension associated with estimates of the Hubble constant $H_{0}$. Two scenarios within a flat FRW spacetime were considered. In the first case, the scalar field mimics cold dark matter, whereas in the second case, it acts as dark energy. We derive the dynamical equations and perform a statistical analysis using observational data of $H(z)$, obtaining constraints for the cosmological parameters. The results indicate that the model can effectively fit the
cosmic expansion rate at late epochs, providing values of $H_{0}$ that are more compatible with local measurements. These results suggest that the non-minimal coupling sector in the Horndeski context constitutes a viable and promising approach to alleviate the $H_{0}$ tension and investigate scenarios beyond the standard cosmological model.
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Astrophysics of Galaxies
A first look at quasar-galaxy clustering at $z\simeq7.3$
Jan-Torge Schindler, Joseph F. Hennawi, Frederick B. Davies et al. (+8 more)
We present JWST observations of the environments surrounding two high-
redshift quasars, J0252$-$0503 at $z = 7.0$ and J1007$+$2115 at $z = 7.5$, which enable the first constraints on
quasar-
galaxy clustering at $z \sim 7.3$.
Galaxies in the vicinity of the
quasars are selected through ground-based and JWST/NIRCam imaging and then spectroscopically confirmed with JWST/NIRSpec using the multi-shutter assembly (MSA). Over both fields, we identified 51 $z>5$
galaxies, of which eight are found within a $\Delta v_{\textrm{LOS}}=\pm1500 \rm{km} \rm{s}^{-1}$ line-of-sight velocity window from the
quasars and another eight in the background. The
galaxy J0252\_8713, located just $7\,\rm{pkpc}$ and $\Delta v_{\textrm{LOS}} \approx 360\,\rm{km}\,\rm{s}^{-1}$ from
quasar J0252$-$0503, emerges as a compelling candidate for one of the most distant
quasar-
galaxy mergers. Combining the
galaxy discoveries over the two fields, we measure the
quasar-
galaxy cross-correlation and obtain a correlation length of $r_0^{\rm{QG}}\approx7.6_{-1.6}^{+1.7}\,h^{-1}\,\rm{cMpc}$, based on a power-law model with a fixed slope of $\gamma_{\rm{QG}} = 2.0$. Under the assumption that
quasars and
galaxies trace the same underlying dark matter density fluctuations, we infer a minimum dark matter
halo mass for $z\simeq7.3$
quasars of $\log_{10}(M_{\textrm{halo, min}}/\textrm{M}_{\odot})= 11.6_{-0.7}^{+0.6}$ in a
halo model framework. Compared to measurements from EIGER at $\langle z \rangle = 6.25$ and ASPIRE at $\langle z \rangle = 6.7$ (where $\log_{10}(M_{\textrm{halo, min}}/\textrm{M}_{\odot}) \gtrsim 12.3$), our clustering results provide tentative evidence for a non-monotonic
redshift evolution of
quasar clustering properties. We further estimate a
quasar duty cycle of $f_{\rm{duty}}\approx0.05\%$, consistent with constraints from
quasar proximity zones and IGM damping wings. (abridged)
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All authors Jan-Torge Schindler, Joseph F. Hennawi, Frederick B. Davies, Sarah E. I. Bosman, Feige Wang, Jinyi Yang, Anna-Christina Eilers, Xiaohui Fan, Koki Kakiichi, Elia Pizzati, Riccardo Nanni
Solar and Stellar Astrophysics
Starspot temperature of CoRoT-2 from multiwavelength observations with SPARC4
Adriana Valio, Eder Martioli, Andre O. Kovacs et al. (+5 more)
Measuring starspot temperatures is crucial for understanding
stellar magnetic activity, as it affects
stellar brightness variations, influences
exoplanet transit measurements, and provides constraints on the physical conditions and energy transport in active regions, offering insights into
stellar dynamos. Our goal is to determine the temperature of starspots on the active
star CoRoT-2 to enhance our understanding of
magnetic activity in young,
solar-like
stars. Multiwavelength observations were conducted using the SPARC4 instrument on the 1.6-m
telescope at Pico dos Dias Observatory (Brazil), capturing simultaneous transit data in four photometric bands (g, r, i, and z). The ECLIPSE model, combined with MCMC fitting, was used to model spot characteristics during the planetary transit of CoRoT-2 b. The spot intensities were analyzed considering three different methods: the assumption of blackbody emission, the PHOENIX atmospheric model, and multiwavelength fitting assuming the same spot parameters for all wavelengths. Two starspots were detected in the residuals of the light curve, yielding temperature estimates of 5040 - 5280 K based on the three different methods. These values align more closely with the temperatures of
solar penumbrae than with typical umbral temperatures, suggesting relatively moderate
magnetic activity. The radius of the spots ranged from 0.34 - 0.61 the planetary radius, or equivalently (38 - 69)$\times10^6$m, much larger than sunspots. This study provides a method to estimate spot temperatures on active
stars using multiband photometry, with results indicating penumbral-like temperatures on CoRoT-2. The methodology enhances precision in starspot temperature estimation, beneficial for studies of
stellar activity and
exoplanet characterization.
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All authors Adriana Valio, Eder Martioli, Andre O. Kovacs, Viktor Y. D. Sumida, Leandro de Almeida, Diego Lorenzo-Oliveira, Francisco Jablonski, Claudia V. Rodrigues
Cosmology and Nongalactic Astrophysics
BASILISK III. Stress-testing the Conditional Luminosity Function model
Kaustav Mitra and Frank C. van den Bosch
The Conditional Luminosity Function (CLF) is an effective and flexible way of characterizing the
galaxy-
halo connection. However, it is subject to a particular choice for its parametrization, which acts as a prior assumption. Most studies have been restricted to what has become a standard CLF parametrization with little to no variation. The goal of this paper is to investigate whether this model is sufficient to fully characterize the small-scale data extracted from spectroscopic surveys and to gauge how adding or removing degrees of freedom impact the inference regarding the
galaxy-
halo connection. After extensive validation with realistic mock data, we use Basilisk, a highly constraining
Bayesian hierarchical tool to model the kinematics and abundance of satellite
galaxies, to test the standard CLF model against a slew of more flexible variants. In particular, we test whether the SDSS data favour any of these variants in terms of a goodness-of-fit improvement, and identify the models that are sufficiently flexible, beyond which additional model freedom is not demanded by the data. We show that some of these additional degrees of freedom, which have hitherto not been considered, result in a drastic improvement of the fit and cause significant changes in the inferred
galaxy-
halo connection. This highlights that an empirical model comes with an implicit prior about the parametrization form, which needs to be addressed to ensure that it is sufficiently flexible to capture the complexity of the data and to safeguard against a biased inference.
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Instrumentation and Methods for Astrophysics
Emergent Denoising of SDSS Galaxy Spectra Through Unsupervised Deep Learning
Oliver Camilleri, Zahra Sharbaf and Ignacio Ferreras
Spectroscopy represents the ideal observational method to maximally extract information from
galaxies regarding their
star formation and chemical enrichment histories. However, absorption spectra of
galaxies prove rather challenging at high
redshift or in low mass
galaxies, due to the need to spread the
photons into a relatively large set of spectral bins. For this reason, the data from many state-of-the-art spectroscopic surveys suffer from low signal-to-noise (S/N) ratios, and prevent accurate estimates of the
stellar population parameters. In this paper, we tackle the issue of denoising an ensemble by the use of unsupervised Deep Learning techniques trained on a homogeneous sample of spectra over a wide range of S/N. These methods reconstruct spectra at a higher S/N and allow us to investigate the potential for Deep Learning to faithfully reproduce spectra from incomplete data. Our methodology is tested on three key line strengths and is compared with synthetic data to assess
retrieval biases. The results suggest a standard Autoencoder as a very powerful method that does not introduce systematics in the reconstruction. We also note in this work how careful the analysis needs to be, as other methods can – on a quick check – produce spectra that appear noiseless but are in fact strongly biased towards a simple overfitting of the noisy input. Denoising methods with minimal bias will maximise the quality of ongoing and future spectral surveys such as DESI, WEAVE, or WAVES.
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Astrophysics of Galaxies
Probing viscosity of the intracluster medium using ram-pressure stripping
Yung-Hsuan Tseng, Hsiang-Yi Karen Yang, Ryan Farber et al. (+1 more)
Galaxies falling into
galaxy clusters can leave imprints on both the corona of
galaxies and the intracluster medium (ICM) of
galaxy clusters. Throughout this infall process, the
galaxy's atmosphere is subjected to ram pressure from a headwind, leading to the stripping morphology observed in its tail. The morphological
evolution is affected by the properties of the surrounding ICM such as
magnetic fields and viscosity. In this Letter, we perform 3D Braginskii-magnetohydrodynamic simulations using the FLASH code with varied ICM viscosity models. Specifically, we explore four models: an inviscid case, unsuppressed isotropic viscosity, unsuppressed anisotropic viscosity, and anisotropic viscosity suppressed by
plasma instabilities. Our findings indicate that the isotropic viscosity case effectively suppresses hydrodynamic instabilities and shows strong viscous heating and the least mixing with the ICM, enabling the formation of long, coherent tails. The inviscid model has the shortest tail due to vigorous mixing, and the models with anisotropic viscosity are in between. The model with suppressed anisotropic viscosity due to
plasma instabilities exhibits enhanced
turbulence in the
galactic tail and a concurrent limitation in viscous heating compared to the model neglecting
plasma instabilities. These findings highlight the significant impact of ICM
plasma physics on the processes of ram pressure stripping of
galaxies.
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All authors Yung-Hsuan Tseng, Hsiang-Yi Karen Yang, Ryan Farber, Mateusz Ruszkowski
Solar and Stellar Astrophysics
Gaia DR3 Open Cluster Cepheids: A Unified Catalog with Calibrated Period-Age and Period-Wesenheit Relations
Shunhong Deng, Zhihong He, Anbing Ren et al. (+7 more)
Classical Cepheids (CCs) in
Galactic open clusters (OCs) provide essential observational constraints for calibrating the period-age relation (PAR) and the period-Wesenheit relation (PWR) of CCs. However, distant and long-period OC Cepheids remain limited, while the confirmed samples still require more precise determinations of their physical properties, such as ages and extinctions. In this work, we present a comprehensive census of OC Cepheids based on an extensive sample of distant OCs from
Gaia Data Release 3 (DR3). By combining astrometric and photometric membership analyses, we identified 110 CCs associated with 102 OCs, of which 41 CCs across 37 OCs were classified as OC Cepheids, while the remaining cases were considered candidate or rejected associations. Our results are consistent with previous studies, while 4 of the 41 OC Cepheids are newly reported here. Using updated cluster parameters derived from manual isochrone fitting, we primarily refined the PAR to log Age = (-0.595 $\pm$ 0.044) log P + (8.430 $\pm$ 0.042) and recalibrated the PWR to WG = (-3.615 $\pm$ 0.083) log P + (-2.379 $\pm$ 0.096). This study expands the sample of confirmed and candidate OC Cepheids. The newly longest-period confirmed OC Cepheid is BM Per (CWNU 3123) with log P = 1.36, and two newly discovered OC Cepheid candidates have distances exceeding 6 kpc. Moreover, the PAR and PWR are improved by incorporating refined OC ages and updated parallaxes, respectively.
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All authors Shunhong Deng, Zhihong He, Anbing Ren, Qian Cui, Xiaoyue Zhou, Liming Peng, Chenxin Wang, Ziang Chen, Yangping Luo, Kun Wang
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Primordial Black Holes, Charge, and Dark Matter: Rethinking Evaporation Limits
Sebastian Schuster, Jessica Santiago, Justin Feng et al. (+1 more)
Limits on the dark matter fraction of small mass
primordial black holes from Hawking radiation are predominantly derived from the assumption of a Schwarzschild black hole evaporating. However, astrophysical black holes are usually much more realistically modelled by the rotating Kerr black hole solution. Meanwhile, electromagnetically charged black holes are astrophysically of little importance due to their fast neutralisation in the present universe. Dark matter is not just a possible solution to issues of astrophysics and cosmology, but also to issues of the standard model of particle physics. Extensions of this model thus can lead to charges present in the early universe which remain preserved in the charge of
primordial black holes - even when the corresponding particles have disappeared from the particle content of the present epoch of the universe. Here, we report on a thorough proof-of-concept that such charges can greatly change evaporation limits for
primordial black hole dark matter. Special emphasis is placed on (near-)extremal black holes, for which this effect is especially pronounced.
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All authors Sebastian Schuster, Jessica Santiago, Justin Feng, Matt Visser
High Energy Astrophysical Phenomena
A broadband study of FRB20240114A with the Effelsberg 100-m radio telescope
P. Limaye, L.G. Spitler, N. Manaswini et al. (+5 more)
We present Effelsberg 100-m
telescope observations of the hyperactive repeating fast
radio burst source FRB 20240110A, discovered by CHIME/FRB in January 2024. Using the Ultra BroadBand (UBB) receiver, spanning 1.3-6.0 GHz, we detected over 700 unique bursts across four observing epochs. A comprehensive analysis of their temporal and spectral properties reveals four distinct spectro-temporal morphologies, including simple, complex and frequency-drifting structures. No bursts were detected across the full UBB band, confirming the band-limited emission typical of repeating FRBs. We find modest frequency
evolution in burst widths but constant fractional bandwidths, and strong variability in burst rates that may be influenced by scintillation. The waiting-time distributions indicate predominantly independent burst events, with occasional clustering suggesting a characteristic emission timescale of $\sim$10 ms. Additionally, this study presents a multi-frequency analysis of waiting-time distributions, offering new insights into the complex frequency drifts commonly observed in repeating FRBs. These broadband observations provide a detailed view of the frequency-dependent burst behavior of FRB 20240110A and offer insights into the variability and temporal structure of repeating FRB emission.
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All authors P. Limaye, L.G. Spitler, N. Manaswini, J. Benáček, F. Eppel, M. Kadler, L. Nicotera, J. Wongphechauxsorn
Instrumentation and Methods for Astrophysics
Mephisto: Self-Improving Large Language Model-Based Agents for Automated Interpretation of Multi-band Galaxy Observations
Zechang Sun, Yuan-Sen Ting, Yaobo Liang et al. (+3 more)
Astronomical research has long relied on human expertise to interpret complex data and formulate scientific hypotheses. In this study, we introduce Mephisto – a multi-
agent collaboration framework powered by large
language models (LLMs) that emulates human-like
reasoning for analyzing multi-band
galaxy observations. Mephisto interfaces with the CIGALE codebase (a library of spectral energy distribution, SED, models) to iteratively refine physical models against observational data. It conducts deliberate
reasoning via tree search, accumulates knowledge through self-play, and dynamically updates its knowledge base. Validated across diverse
galaxy populations – including the James Webb Space
Telescope's recently discovered "Little Red Dot"
galaxies – we show that Mephisto demonstrates proficiency in inferring the physical properties of
galaxies from multi-band photometry, positioning it as a promising research copilot for astronomers. Unlike prior black-box machine learning approaches in astronomy, Mephisto offers a transparent, human-aligned
reasoning process that integrates seamlessly with existing research practices. This work underscores the possibility of LLM-driven
agent-based research for astronomy, establishes a foundation for fully automated, end-to-end artificial intelligence (AI)-powered scientific workflows, and unlocks new avenues for AI-augmented discoveries in astronomy.
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All authors Zechang Sun, Yuan-Sen Ting, Yaobo Liang, Nan Duan, Song Huang, Zheng Cai
Cosmology and Nongalactic Astrophysics
Enhancing Multiplet Alignment Measurements with Imaging
Alexus Annika Kumwembe, Claire Lamman, Daniel Eisenstein et al. (+35 more)
We demonstrate that measurements of the gravitational
tidal field made with spectroscopic
redshifts can be improved with information from imaging surveys. The average orientation of small groups of
galaxies, or "multiplets" is correlated with large-scale structure and is used to measure the direction of
tidal forces. Previously, multiplet intrinsic
alignment has been measured in DESI using
galaxies that have spectroscopic
redshifts. The DESI Legacy Imaging catalog can be used to supplement multiplet catalogs. Our findings show that
galaxy positions from the imaging catalog produce a measurement similar to the measurements made with only spectroscopic data. This demonstrates that imaging can improve our signal-to-noise ratio for multiplet
alignment in DESI.
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All authors Alexus Annika Kumwembe, Claire Lamman, Daniel Eisenstein, Jessica Nicole Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, Biprateep Dey, Peter Doel, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztanaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Mustapha Ishak, Jorge Jimenez, Dick Joyce, Robert Kehoe, Theodore Kisner, Ofer Lahav, Martin Landriau, Marc Manera, Ramon Miquel, Seshadri Nadathur, Nathalie Palanque-Delabrouille, Ignasi Perez-Rafols, Francisco Prada, Graziano Rossi, Eusebio Sanchez, David Schlegel, Hee-Jong Seo, Joseph Harry Silber, David Sprayberry, Gregory Tarle, Benjamin Alan Weaver
Cosmology and Nongalactic Astrophysics
Probing departures from $\Lambda$CDM by late-time datasets
Himanshu Chaudhary, Vipin Kumar Sharma, Salvatore Capozziello et al. (+1 more)
Observational data play a pivotal role in identifying cosmological models that are both theoretically consistent and empirically viable. In this work, we investigate the level of preference for dynamical dark energy over a cosmological constant using current late-time observational
datasets, including
Cosmic Chronometers ,
Baryon Acoustic Oscillations from DESI DR2, and different Type Ia
supernova catalogs (Pantheon$^+$, DES-Dovekie, Union3). We analyze various dynamical dark energy models, including $\omega$CDM, o$\omega$CDM, $\omega_0\omega_a$CDM, Logarithmic, Exponential, JBP, BA, and GEDE. In most cases, the o$\Lambda$CDM and o$\omega$CDM models favor an open Universe. For the o$\omega$CDM, the inclusion of DES-Dovekie or Union3 data together with CC and DESI DR2 favors a nearly flat geometry. Using the CC + DESI DR2
dataset, the preference for dynamical dark energy lies between the $1$-$2\sigma$ level. When different
supernova catalogs (DES-Dovekie or Union3) are included, the deviation from $\Lambda$CDM in the $\omega$CDM, $\omega_0\omega_a$CDM, Logarithmic, JBP, BA, and GEDE models increases to the $2$-$2.74\sigma$ level, while the Pantheon$^{+}$ sample yields deviations below the $2\sigma$ level. We find consistent evidence for $\omega_0 > -1$ and $\omega_a < 0$ across all dark energy models, indicating a preference for dynamical dark energy characterized by a Quintom-B type scenario. The $\Lambda$CDM paradigm has long served as the standard framework of modern cosmology; however recent DESI DR2 results have exposed emerging tensions with the cosmological constant $\Lambda$, hinting at possible new physics in the dark energy sector. Even so, the currently available data are still not strong enough to definitively rule out the $\Lambda$CDM model.
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All authors Himanshu Chaudhary, Vipin Kumar Sharma, Salvatore Capozziello, G. Mustafa
Cosmology and Nongalactic Astrophysics
The superclustering of hot gas: cosmological sensitivity in the Websky simulations
M. Lokken, J. R. Bond, R. Hložek et al. (+3 more)
Combinations of
galaxy surveys and
cosmic microwave background secondaries, such as the thermal Sunyaev-Zel'dovich (tSZ) effect, are increasingly being used to jointly constrain cosmology and astrophysical properties of the gas within and beyond
halos. Standard cross-correlations measure a directionless correlation between the microwave maps and
galaxy catalogs. However, more information about the
cosmic web structure can be captured by summary statistics which include environmental constraints and measure oriented correlations along axes of structure, such as filaments or superclusters. This work studies the sensitivity of multipole moments of constrained oriented stacks, a directional and environmentally-dependent statistic, to variations in cosmological and astrophysical parameters. We run nine different 2.4 Gpc-per-side simulations with the Websky
algorithm, varying the matter density within flat $\Lambda$CDM, and create mock tSZ maps with each. We also apply six different gas prescriptions, imitating AGN feedback variations, to the fiducial cosmology. We analyze oriented stacks of the tSZ signal in supercluster regions in each simulation, focusing on signal out to $\sim20$ transverse Mpc from massive ($M>5\times10^{13}~M_\odot$)
halos. The cosmology variations affect anisotropic and isotropic measurements similarly, while the
halo-pasted gas variations mostly affect the isotropic signal. Our results suggest it is worthwhile to incorporate directional information into SZ-
galaxy cross-correlations to increase cosmological sensitivity and help break degeneracies with gas physics.
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All authors M. Lokken, J. R. Bond, R. Hložek, N. J. Carlson, Z. Li, A. van Engelen
Earth and Planetary Astrophysics
Direct Spectroscopy of 51 Eridani b with JWST NIRSpec
Alexander Madurowicz, Jean-Baptiste Ruffio, Bruce Macintosh et al. (+4 more)
We present high-contrast direct spectroscopy of the low-mass, cool
exoplanet 51 Eridani b (2-4 M$_\textrm{Jup}$, $\sim$750 K) using JWST / NIRSpec in a fixed-slit configuration (F290LP / G395H, $3-5\,\mu$m, R$\sim$2,700). A cross correlation analysis between the continuum-subtracted data and atmospheric forward models indicates a detection of molecular signals of planetary origin at $4.8\sigma$ at the expected position and velocity of the
planet. The detection of the planetary signal is driven primarily by molecular features from methane and carbon monoxide, providing the first direct confirmation of these two molecules coexisting in chemical disequilibrium in the atmosphere of 51 Eridani b. A new comprehensive atmospheric model analysis shows consistency between the ground-based IFU spectroscopy and the NIRSpec data, with the best-fit model parameters: $T_\mathrm{eff}$ = 800$^{+21.5}_{-55.5}$ K, $\log g$ = 3.75$^{+0.09}_{-0.37}$, $[\mathrm{M}/\mathrm{H}]$ = 0.7$^{+0.07}_{-0.21}$, $\textrm{C}/\textrm{O}$ = 0.458$^{+0.08}_{-0.09}$, $\log K_\mathrm{zz}$ = 3$^{+0.47}_{-0.73}$, $R_\mathrm{P}$ = 1.36$^{+0.07}_{-0.03}$ $R_\mathrm{Jup}$, $f_\mathrm{hole}$ = 0.3$^{+0.10}_{-0.07}$, and the NIRSpec errorbar inflation parameter: $\hat{e}$ = 1.74$^{+0.02}_{-0.03}$. We conclude with a discussion on the lessons learned between the fixed slit and IFU-based high contrast spectroscopic methods from our observing program, including some possibilities to improve the analysis method.
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All authors Alexander Madurowicz, Jean-Baptiste Ruffio, Bruce Macintosh, Marshall Perrin, Quinn M. Konopacky, Aneesh Baburaj, Kielan Hoch
Earth and Planetary Astrophysics
SOAPv4: A new step toward modeling stellar signatures in exoplanet research
E. Cristo, J. P. Faria, N. C. Santos et al. (+6 more)
We present and describe a new version of the spot oscillation and
planet code, SOAPv4. Our aim is to demonstrate its capabilities in modeling
stellar activity in the context of RV measurements and its effects on transmission spectra. To do this, we employed
solar observations alongside synthetic spectra and compared the resulting simulations. We used SOAPv4 to simulate photospheric active regions and planetary transits for a Sun-like
star hosting a hot Jupiter. By varying the input spectra, we investigated their impact on the resulting absorption spectra and compared the corresponding simulations. We then assessed how
stellar activity deforms these absorption profiles. Finally, we explored the chromatic signatures of
stellar activity across different wavelength ranges and discussed how such effects have been employed in the literature to confirm
planet detections in radial-velocity measurements. We present the latest updates to SOAP, a tool developed to simulate active regions on the
stellar disk while accounting for wavelength-dependent contrast. This functionality enables a detailed study of chromatic effects on radial-velocity measurements. In addition, SOAPv4 models
planet-occulted line distortions and quantifies the influence of active regions on absorption spectra. Our simulations indicate that granulation can introduce line distortions that mimic planetary absorption features, potentially leading to misinterpretations of atmospheric dynamics. Furthermore, comparisons with ESPRESSO observations suggest that models incorporating non-local thermodynamic
equilibrium effects provide an improved match to the absorption spectra of HD 209458 b, although they do not fully reproduce all observed distortions.
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All authors E. Cristo, J. P. Faria, N. C. Santos, W. Dethier, B. Akinsanmi, A. Barka, O. Demangeon, J. P. Lucero, A. M. Silva
Instrumentation and Methods for Astrophysics · Cross-listed from physics.comp-ph
Iterated Agent for Symbolic Regression
Zhuo-Yang Song, Zeyu Cai, Shutao Zhang et al. (+8 more)
Symbolic regression (SR), the automated discovery of mathematical expressions from data, is a cornerstone of scientific inquiry. However, it is often hindered by the combinatorial explosion of the search space and a tendency to overfit. Popular methods, rooted in genetic programming, explore this space syntactically, often yielding overly complex, uninterpretable models. This paper introduces IdeaSearchFitter, a framework that employs Large
Language Models (LLMs) as semantic operators within an evolutionary search. By generating candidate expressions guided by natural-
language rationales, our method biases discovery towards models that are not only accurate but also conceptually coherent and interpretable. We demonstrate IdeaSearchFitter's efficacy across diverse challenges: it achieves competitive, noise-robust performance on the Feynman Symbolic Regression Database (FSReD), outperforming several strong baselines; discovers mechanistically aligned models with good accuracy-complexity trade-offs on real-world data; and derives compact, physically-motivated parametrizations for Parton Distribution Functions in a frontier high-energy physics application. IdeaSearchFitter is a specialized module within our broader iterated
agent framework, IdeaSearch, which is publicly available at https://www.ideasearch.cn/.
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All authors Zhuo-Yang Song, Zeyu Cai, Shutao Zhang, Jiashen Wei, Jichen Pan, Shi Qiu, Qing-Hong Cao, Tie-Jiun Hou, Xiaohui Liu, Ming-xing Luo, Hua Xing Zhu
Astrophysics of Galaxies
MOLLId: software for automatic identification of spectral molecular lines in the sub-millimeter and millimeter bands and its application to the spectra of protostars from the region RCW 120
A. A. Farafontova, M. S. Kirsanova and S. V. Salii
In this work, we present the program MOLLId (MOLecular Line Identification) for automated molecular lines approximation with gaussian profile. Molecular identification was performed using multi-level comparison of the lines' center frequencies and rest frequencies from the spectroscopic database. The program was tested using identification of the molecular lines in observational spectra of young
stellar objects RCW 120 YSO S1 and RCW 120 YSO S2, located near the border of the RCW 120 PDR. In the spectra of the RCW 120 YSO S1 source, 100 lines of 41 molecules were identified over the level of 4-6 sigma. In the spectra of the RCW 120 YSO S2 source, 407 lines of 79 molecules were identified over the level 3-5 sigma. Using Intel Core i7-12700K CPU, identification time is equal to 6 and 8 minutes per spectral range for the YSOs S1 and S2, respectively. From the analysis of CH3OH, CH3CN, CH3CCH molecules identified in RCW 120 YSO S2 we found a two-component structure and estimated the physical parameters in the LTE approximation for each of the components.
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Astrophysics of Galaxies
The Dependence of Halo Clustering on Subhalo Anisotropy and Planarity
Nathaniel P. Johnson and Andrew R. Zentner
We show that host cold dark matter (CDM)
haloes cluster in a manner that depends upon the anisotropy and planarity of their subhaloes, indicating an environmental dependence to subhalo anisotropy and planarity. The spatial distributions of both satellite
galaxies about central
galaxies and subhaloes about host
haloes have been subjects of interest for two decades. Important questions include the degree to which satellites are distributed anisotropically about their hosts or exhibit planarity as well as the degree to which this anisotropy depends on the environment of the system. We study the spatial distributions of subhaloes in a cosmological N-body simulation. We find that CDM subhaloes are distributed in a manner that is strongly anisotropic and planar, in agreement with prior work, though w e present this in a new way. The more novel result is that anisotropy has an environmental dependence. Systems with subhaloes that exhibit $\textit{less}$ ($\textit{more}$) anisotropy, $\textit{less}$ ($\textit{more}$) planarity, and reside $\textit{further}$ from ($\textit{closer}$ to) their host centres cluster more $\textit{strongly}$ ($\textit{weakly}$). Moreover, these clustering effects are not primarily the result of the correlation between subhalo anisotropy and/or planarity and another $\textit{single}$
halo property upon which clustering is already known to depend (e.g. concentration). This is a new and distinct effect. We discuss the impact of this result on the anisotropies of satellites as predict ed by CDM, its testability, and its possible relation to the anisotropies observed about the large
galaxies of the Local Group. In an appendix, we clarify our construction of ellipsoidal mock
halo catalogues.
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Earth and Planetary Astrophysics
Lorenzo Peerani, Saburo Howard and Ravit Helled
The composition and internal structure of gas
giant exoplanets encode key information about their formation and
evolution. We investigate how different assumed interior structures affect the inferred bulk
metallicity and its correlation with planetary mass. For a sample of 44
giant exoplanets (0.12-5.98 MJ), we computed evolutionary models with CEPAM and retrieved their bulk
metallicities under three structural hypotheses: core+envelope (CE), dilute core (DC), and fully mixed (FM). Across all structures, we recover a significant positive correlation between total heavy-element mass (MZ) and planetary mass (M), and a negative correlation between bulk
metallicity (Z) and M (also for Z/Zstar vs M). Dilute core structures yield
metallicities comparable to CE models, regardless of the assumed extent of the composition gradient. Increasing atmospheric
metallicity augments the inferred bulk
metallicity, as enhanced opacities slow planetary cooling. Non-adiabatic DC models can further increase the retrieved
metallicity by up to 35 percent. We find that the mass-
metallicity anti-correlation is primarily driven by low-mass, metal-rich
planets (M < 0.2 MJ), and that massive
planets (greater than about 1 MJ) can exhibit unexpectedly high
metallicities (Z approximately 0.1-0.3). Improved constraints on convective mixing, combined with upcoming accurate measurements of planetary masses, radii, and atmospheric compositions from missions such as PLATO and Ariel, will provide further constraints on interior structure and formation models of gas
giant planets.
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Solar and Stellar Astrophysics
Phase-resolved spectroscopic observations of the magnetic cataclysmic binary EF Eridani: Revealing complex magnetic accretion during a high state
Zwidofhela N. Khangale, Stephen B. Potter, David A. H. Buckley et al. (+1 more)
We present high-resolution, phase-resolved spectroscopic observations of the polar EF Eri, obtained with SALT and the SAAO 1.9-m
telescope during its recent emergence from a three-decade-long low state. The average spectrum shows strong emission from the Balmer lines (H$\alpha$ and H$\beta$) and He~ii 4686 Å, along with weaker emission from the He~i lines and the Bowen fluorescence (C~iii/N~iii) blend at 4650 Å. The emission lines redward of 5500 Å transition to pure absorption at orbital phases $\sim$0.75–0.95, which we attribute to obscuration of the line-emitting region by the
accretion stream. Trailed spectra of the emission lines reveal multicomponent structures consistent with other polars. In this first Doppler study of EF Eri, tomograms of the strongest lines (He~ii 4686 Å and the Balmer lines), using both the standard and inside-out projections, identify three key emission regions: the irradiated face of the secondary
star, the ballistic and threading regions of the
accretion stream, and the magnetically confined flow. Our Doppler maps show not only the ballistic stream but also two unambiguous
magnetic accretion flows, which is consistent with the presence of multiple
magnetic accretion regions.
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All authors Zwidofhela N. Khangale, Stephen B. Potter, David A. H. Buckley, Paul E. Barrett
High Energy Astrophysical Phenomena
The very high energy view of gamma-ray bursts with the MAGIC telescopes
Alessio Berti, Željka Bošnjak, Alberto Castro-Tirado et al. (+22 more)
Gamma-ray bursts (GRBs) are one of the main targets for the observations of the MAGIC
telescopes. As a result of the effort in improving the sensitivity of the instrument and the automatic follow-up strategy, MAGIC detected two GRBs in the very-high-energy (VHE, $E>100$ GeV) range, namely GRB 190114C and GRB 201216C. In GRB 190114C ($z=0.42$), the data collected by MAGIC revealed a new emission component at sub-TeV energies in the afterglow of the GRB. The very rich multi-wavelength
dataset, spanning 17 orders of magnitude in energy, allowed to perform a detailed modelling of the broadband emission. The multi-wavelength data could be modelled within a one-zone synchrotron-self Compton scenario with internal $\gamma-\gamma$ absorption, where the model parameters are compatible with those found in previous GRB afterglow studies below GeV energies. Similarly, GRB 201216C broadband emission could be explained using the same model, although the amount of simultaneous multi-wavelength data is reduced with respect to GRB 190114C. In particular, GRB 201216C challenged the current MAGIC detection potential, as its
redshift was determined to be $z=1.1$, strongly reducing the observed gamma-ray flux but making it the most distant source detected at VHE. These two detections, accompanied by evidence of VHE emission from a few more GRBs, opened up new questions such as the presence of sub-TeV emission in different classes and phases of GRBs. In this contribution we will present the status of the MAGIC GRB follow-up program, with an highlight on its detected GRBs. Moreover we will show the results on the GRBs observed by MAGIC from 2013 to 2019 with no evidence of VHE emission, in particular for those with simultaneous X-ray observations and
redshift $z<2$. We will discuss the implications of these results for GRB physics and the challenges and prospects for future GRB observations with MAGIC.
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All authors Alessio Berti, Željka Bošnjak, Alberto Castro-Tirado, Stefano Covino, Susumu Inoue, Francesco Longo, Serena Loporchio, Davide Miceli, Razmik Mirzoyan, Elena Moretti, Lara Nava, Koji Noda, David Paneque, Antonio Stamerra, Yusuke Suda, Kenta Terauchi, Ievgen Vovk, Katsuaki Asano, Satoshi Fukami, Nuria Jordana-Mitjans, Andrea Melandri, Carole Mundell, Michele Palatiello, Manisha Shrestha, Iain Steele
High Energy Astrophysical Phenomena
Explanation of the Mass Distribution of Binary Black Hole Mergers
Lei Li, Guoliang Lv, Chunhua Zhu et al. (+5 more)
Gravitational wave detectors are observing an increasing number of binary black hole (BBH) mergers, revealing a bimodal mass distribution of BBHs, which hints at diverse formation histories for these systems. Using the rapid binary population synthesis code MOBSE, we simulate a series of population synthesis models that include chemically homogeneous
evolution (CHE). By considering
metallicity-specific
star formation and selection effects, we compare the intrinsic merger rates and detection rates of each model with observations. We find that the observed peaks in the mass distribution of merging BBHs at the low-mass end (10\msun) and the high-mass end (35\msun) are contributed by the common envelope channel or stable mass transfer channel (depending on the stability criteria for mass transfer) and the CHE channel, respectively, in our model. The merger rates and detection rates predicted by our model exhibit significant sensitivity to the choice of physical parameters. Different models predict merger rates ranging from 15.4 to $96.7\,\rm{Gpc^{-3}yr^{-1}}$ at
redshift $z$ = 0.2, and detection rates ranging from 22.2 to 148.3$\mathrm{yr^{-1}}$ under the assumption of a detectable
redshift range of $z \le$ 1.0.
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All authors Lei Li, Guoliang Lv, Chunhua Zhu, Sufen Guo, Hongwei Ge, Weimin Gu, Zhuowen Li, Xiaolong He