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Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 6 June

Solar and Stellar Astrophysics

Modern Time-Series and Spectral Methods for Analyzing Solar and Stellar Oscillatory Signals

Yuan Ding and Feng Song

Time-series analysis plays a central role in understanding oscillatory and wave phenomena in solar and stellar atmospheres. However, astrophysical observations are inherently affected by instrumental noise, non-stationary dynamics, and uneven sampling. This review provides a comprehensive overview and comparative analysis of principal methods for detecting and characterizing periodicities in solar and stellar signals. We cover Fourier-transform-based transforms, nonlinear-fitting-based methods (Lomb–Scargle periodogram), time-frequency methods (wavelet and synchrosqueezed transforms), and adaptive decomposition techniques (Empirical Mode Decomposition). Advanced statistical significance tests, including false-alarm probability, autoregressive models, and Bayesian Markov Chain Monte Carlo (MCMC) approaches, are discussed their practical limitations and misuse risks. Through comparative analysis using synthetic benchmarks, we provide guidelines for selecting methods based on signal stationarity, sampling regularity, and noise characteristics. Finally, we outline future directions that integrate Bayesian inference with time-frequency analysis to achieve both statistical rigor and temporal localization in studying non-stationary solar and stellar oscillations.
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Cosmology and Nongalactic Astrophysics

Prior-Averaged Ranking of Low-Order Monomial Potentials in Low-Temperature Warm Inflation

Xin Peng, Xiang Cheng, Wei Cheng et al. (+3 more)

We compare the relative prior-averaged weights of the monomial potentials \(V_p(\phi)=\lambda_p\phi^p/p\), with \(p=2,3,4\), in low-temperature warm inflation with the dissipative coefficient fixed to \(\Upsilon=C_\phi T^3/\phi^2\). The dissipative form, background equations, primordial-spectrum prescription, and compressed observable likelihood are held fixed while the monomial power is varied. For each branch, the warm background equations, including radiation backreaction, are solved numerically, and the broadened likelihood for \((A_s,n_s,r_{0.05})\) is integrated over the adopted prior domain to obtain \(Z_{\rm eff}^{(A_s,n_s,r)}\). For the reference configuration \(N_*=55\), \(\sigma_r=0.005\), and the viability-conditioned prior A, we obtain \(\Delta\ln Z_{\rm eff}(p=2)=-32.18\) and \(\Delta\ln Z_{\rm eff}(p=3)=-6.99\) relative to \(p=4\). The same ranking is retained for the specific variations of \(N_*\), the prior domains, the random seeds, and the smoothing width of the upper-bound penalty examined here. A representative quartic trajectory gives \(n_s=0.96420\), \(r_{0.05}=0.02663\), \(Q_*=4.68\times10^{-3}\), and \(T_*/H_*=10.67\). Its scalar spectrum is evaluated using the assumed Bose–Einstein occupation prescription. A component test at this representative point indicates that the occupation term contributes more to the scalar enhancement than the fitted dissipative growth factor. Thus, within the compressed-likelihood setup, the adopted thermal-occupation prescription, and the adopted viability-conditioned priors, the prior-averaged ranking is \(p=4>p=3\gg p=2\).
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All authors Xin Peng, Xiang Cheng, Wei Cheng, Yi-Rong Ma, Yu Pan, Jun Zeng

Cosmology and Nongalactic Astrophysics

Faraday Complexity and Depolarisation in a High-Rotation-Measure Radio Galaxy from the Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) DR2

Debajyoti Mondal, Abhik Ghosh and Dipanjan Banerjee

We present a broadband spectro-polarimetric analysis of the extragalactic radio source RACS\_0900-28\_7036 using SPICE-RACS DR2 observations with the Australian Square Kilometre Array Pathfinder (ASKAP). The source was selected for its large rotation measure (${\rm RM}=345.7\pm0.2~{\rm rad~m^{-2}}$), substantial excess relative to the local foreground ($\Delta {\rm RM}\approx171~{\rm rad~m^{-2}}$), and strong evidence of Faraday complexity ($\sigma_{\rm add}/\delta\sigma_{\rm add}\approx8.6$). Observations span 803–1083~MHz in 36 spectral channels, enabling detailed characterization of Faraday rotation and wavelength-dependent depolarization. One-dimensional QU-fitting and Bayesian model selection identify a multi-component model comprising one Burn-slab component and two external Faraday dispersion components (1 Slab + 2 EFD) as the preferred description. The dominant astrophysical component exhibits ${\rm RM}\approx345.5~{\rm rad~m^{-2}}$ with modest Faraday dispersion ($\sigma_{\rm RM}\approx3~{\rm rad~m^{-2}}$), consistent with the Galactic foreground rotation measure at the source position (${\rm RM}_{\rm Gal}=331.9\pm33.1~{\rm rad~m^{-2}}$). A secondary broader component at ${\rm RM}\approx131.5~{\rm rad~m^{-2}}$ shows strong depolarization ($\sigma_{\rm RM}\approx19.5~{\rm rad~m^{-2}}$), indicating an additional turbulent Faraday-active medium along the line of sight. The fractional polarization spectrum and $q$–$u$ plane evolution further confirm multiple Faraday-active regions along the line of sight. These results demonstrate that ASKAP broadband spectropolarimetry can resolve complex Faraday structures and probe turbulent magnetized environments, providing a framework for systematic depolarization studies across the full SPICE-RACS catalog and enabling statistical investigations of Faraday complexity in diverse extragalactic radio sources.
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Friday 5 June

Earth and Planetary Astrophysics · Cross-listed from physics.space-ph

Numerical Study of Alfven Wave-Energetic Particle Interaction in the Inner Van Allen Belt and predictions of Seismic-Related Energetic Proton Bursts for the IITMSAT Mission

Snehanshu Maiti and Harishankar Ramachandran

The IIT Madras nano-satellite aims to investigate the science of energetic particle precipitation from the inner Van Allen radiation belt into the upper ionosphere as a potential precursor to earthquakes. Precursors in the form of low frequency electromagnetic waves can appear several hours before an earthquake. These waves, captured near the ionosphere magnetosphere transition region, propagate along geomagnetic field lines as Alfven waves and interact resonantly with trapped energetic particles in the radiation belt, causing their precipitation. Such precipitation can be observed by satellites as energetic particle bursts occurring a few hours prior to the earthquake. A numerical study of Alfven wave energetic proton interactions in the inner Van Allen belt is presented here to investigate the energetic proton precipitation and make predictions to support the scientific objective of the IITM satellite mission. A kinetic model of the energetic trapped proton population in the inner belt is developed, yielding a steady-state distribution that reproduces the observed density profile. The Finite Difference Time Domain method is employed to simulate both narrowband seismic event specific emissions and broadband background noise representing magnetohydrodynamic Alfven wave activity in the inner radiation belt. The studies of interactions of narrow-band Alfven wave packets with the energetic protons in the belt reveals that a sharp cyclotron resonance condition arises at a low Alfven frequency 10 Hz, causing substantial precipitation of high energy protons 125 MeV from their stable mirror orbits. This precipitation can be clearly distinguished from background noisy interactions. Based on these results, we predict the optimal satellite orbital altitude for detecting such energetic proton bursts.
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High Energy Astrophysical Phenomena

Searching for axion dark matter conversion spectral lines in neutron star magnetospheres with FAST

Sinuo Gao, Chen Wang and Maoyuan Liu

The axion is a well-motivated dark matter candidate, which can convert into narrow radio spectral lines via the Primakoff effect in the strongly magnetized magnetospheres of neutron stars. This provides a novel astrophysical probe for axion searches that is complementary to laboratory experiments. Using FAST, the world's most sensitive single-dish radio telescope, we observed two X-ray dim isolated neutron stars (RXJ1605.3+3249 and RXJ1308.6+2127) within its sky coverage, which are predicted to yield the strongest axion-conversion spectral lines (ACL). Although no significant signal was detected at the 5 sigma confidence level, we establish new upper limits on the axion-photon coupling constant g_{a gamma gamma} less than or similar to 5 x 10^{-12} GeV^{-1} for axion masses ranging from 4.14 to 6.20 micro-eV corresponding to the 1.0-1.5 GHz observational band. This result constitutes the tightest constraint in this axion mass range among all existing studies employing the same ACL-based method.
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Cosmology and Nongalactic Astrophysics

Measurements of the Angular Homogeneity Scale from DESI DR1

Mariana Lopes-Dias, Carlos A.P. Bengaly, Xiaoyun Shao et al. (+4 more)

The study of the large-scale distribution of galaxies provides essential information for testing the standard cosmological model, namely the $\Lambda$CDM paradigm. This scenario is based upon two foundations: General Relativity as the theory of gravity, and the Cosmological Principle, which states that the Universe is statistically homogeneous and isotropic on large scales – so that we can measure distances and ages in the Universe assuming the FLRW metric. In this work, we perform a test of the Cosmological Principle by probing the angular homogeneity scale, $\theta_H$, using the state-of-the-art observational data of Luminous Red Galaxies (LRGs) from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). Our analysis is performed exclusively in two dimensions, across narrow redshift ranges inside a larger redshift sample of $0.4 < z < 1.1$, in two different surveyed regions of the sky (North and South Galactic Caps), as we want to minimize a priori dependences on an underlying cosmological model. We obtain that such a scale is indeed identified in all redshift ranges, and that they are consistent with mock simulations assuming the $\Lambda$CDM model. Moreover, our results are in great agreement with previous measurements using Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 16 (SDSS-IV eBOSS DR16), as well as between the north and south galactic caps of the DESI DR1 survey. These findings help underpinning statistical isotropy and homogeneity of the Universe as a physically valid hypothesis in light of upcoming stage-IV redshift surveys, hence are consistent with one of the fundamental pillars of the standard cosmological model.
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All authors Mariana Lopes-Dias, Carlos A.P. Bengaly, Xiaoyun Shao, Rodrigo Gonçalves, Paula S. Ferreira, Gabriela Coutinho de Carvalho, Jailson Alcaniz

Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph

Hybrid simulations of the proton beam instabilities in the young solar wind. The formation of hammerhead-like distributions

R. A. López, Shaaban M. Shaaban, M. Lazar et al. (+4 more)

Parker Solar Probe (PSP) observations in the young solar wind reveal new properties of both plasma particle velocity distributions (VDs) and associated electromagnetic (EM) wave fluctuations. The quasilinear (QL) kinetic theory of plasma wave instabilities has recently shown that new hammerhead (HH) proton distributions can be generated by the relaxation of proton beams through the instabilities of right-handed (RH) polarized waves. Such RH waves have indeed been reported in association with HH distributions. In this paper, new results from hybrid simulations of proton-beam-plasma systems with properties typical of those observed to excite EM-RH wave instabilities are presented. From the long-term evolution of these systems, it is found that beam relaxation is driven by instabilities and growing wave fluctuations, leading to HH-type features in the velocity distributions. The production of these features, as well as their prominence, depends on the magnetic power of the waves generated by the instabilities and, therefore, implicitly on the available free energy, quantified by the plasma beta parameter and the relative beam drift. The simulation results capture the self-consistent evolution of the instabilities and their nonlinear development. Linear theory, together with simulations, helps identify the nature of the unstable modes and the plasma conditions under which they arise. The good agreement with quasi-linear (QL) theory further indicates that it can serve as a computationally efficient complementary framework for interpreting the associated wave-particle interactions.
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All authors R. A. López, Shaaban M. Shaaban, M. Lazar, L. Pezzini, S. Poedts, H. Fichtner, P. H. Yoon

Instrumentation and Methods for Astrophysics

Dynamic Range Beyond Bit Depth of a CMOS Image Sensor Using Interleaved Row Readout

Supriyo Ghosh, William Martin, Hugh R. A. Jones et al. (+3 more)

The dynamic range available from a sensor is vital to its utility. The limits on the dynamic range that can be obtained from an image sensor are set by the brightest and faintest objects that can be detected. In recent years, CMOS (complementary metal-oxide-semiconductor) image sensors (CIS) have gained high popularity due to their low cost and high availability. However, as with all detectors, the dynamic range is constrained by the sensor's bit depth. Here, we have modified the readout scheme of a commercial CIS120 sensor from Teledyne e2v, to enhance its dynamic range. We have advanced the interleaved row readout method proposed by Wocial et al. by using a more sophisticated approach, which enables us to readout chosen rows much more frequently to avoid saturation and then readout other rows on the sensor once to form the image. Our laboratory tests provide a dynamic range of 134 dB elevated from the sensor's native 12-bit of about 71 dB. We also built a camera housing that enabled first-time operation of interleaved row readout on-sky to observe the bright stars, Vega and Polaris. In complex mode we obtained unsaturated single exposure images of these bright stars, which have magnitudes near zero and detect background stars with Gaia G magnitudes around 15 in a single exposure, with a detection threshold of 5$\sigma$. The achievable dynamic range with this interleaved row readout is limited only by the readout noise and scattering in the camera optics.
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All authors Supriyo Ghosh, William Martin, Hugh R. A. Jones, Angaraj Duara, Konstantin Stefanov, Jesper Skottfelt

Solar and Stellar Astrophysics

Extending asteroseismic magnetometry across the diverse landscape of magnetic structures

Nicholas Z. Rui, J. M. Joel Ong, Armand Leclerc et al. (+5 more)

Magnetic fields have now been asteroseismically measured in the cores of many red giants. However, most interpretations of these measurements assume that the magnetic field is far below the critical field strength known to be exceeded by red giants exhibiting gravity-mode suppression. A recent method based on the traditional approximation of rotation and magnetism accurately predicts mode frequencies under fields up to this critical value by modeling gravity waves as individual magnetogravity “polarizations” which propagate through a waveguide-like mode cavity. So far, this formalism has been limited to magnetic fields which are axisymmetric about the rotation axis. In this study, we extend this approach by calculating the polarizations of magnetogravity waves under arbitrarily shaped magnetic fields under potentially rapid rotation. We consider the special cases of a dipolar magnetic field misaligned with the rotation axis as well as a dipole-plus-quadrupole magnetic field with no rotational symmetry. We show that non-axisymmetric field configurations can induce avoided crossings between polarizations, and that waves in such systems can convert between magnetogravity polarizations as they propagate, especially when the magnetic field strength is locally below a stratification-dependent threshold value. This threshold is distinct from the critical field strength for gravity-mode suppression, and is instead similar to the magnetic field strength at which perturbation theory breaks down.
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All authors Nicholas Z. Rui, J. M. Joel Ong, Armand Leclerc, Daniel Lecoanet, Lisa Bugnet, Janosz W. Dewberry, Bastien Liagre, Stéphane Mathis

Instrumentation and Methods for Astrophysics

Do Vision-Language Models See Dwarf Galaxies the Way We Do?

Dimitrios Tanoglidis, Chin Yi Tan, Kate Overdeck et al. (+1 more)

With the advent of powerful, general-purpose vision-language models (VLMs), there has been growing interest in their potential to assist astronomical discovery, a field characterized by large volumes of image data. In this work, we evaluate VLMs on the challenging task of identifying ultra-faint dwarf galaxy candidates using multi-panel diagnostic images from survey data. We compare model predictions to human annotations from a large-scale citizen science campaign. We find that zero-shot VLMs closely reproduce aggregate human calibration and perform well on less ambiguous cases. However, there is significant variability at the level of individual examples, and attempts to obtain uncertainty estimates (via self-reported confidence or repeated inference) fail to yield reliable and practically useful measures. Our results highlight both the promise and the current limitations of deploying VLMs for large-scale scientific discovery in realistic settings.
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All authors Dimitrios Tanoglidis, Chin Yi Tan, Kate Overdeck, Alex Drlica-Wagner

Instrumentation and Methods for Astrophysics

Beyond Point Estimates: Benchmarking Uncertainty Quantification Methods on the AION-1 Astronomical Foundation Model

Karla Tame-Narvaez, Aleksandra Ćiprijanović and Shubhendu Trivedi

Foundation models for astronomical surveys offer powerful learned representations that can be transferred to downstream regression tasks such as galaxy property estimation. However, point predictions alone are insufficient for scientific inference; reliable uncertainty quantification (UQ) is essential. We compare seven UQ methods on galaxy property regression using frozen AION-1 foundation-model embeddings, predicting redshift, stellar mass, stellar-population age, gas-phase metallicity, and specific star-formation rate, from Legacy Survey photometry/imaging and DESI spectra, with PROVABGS-derived labels. Distribution-free conformal methods achieve marginal coverage within $\sim$1\,pp of the nominal 90% across all properties, while non-conformal baselines (Deep Ensembles, MC~Dropout) fail to calibrate reliably. Among conformal approaches, Conformalized Quantile Regression (CQR) delivers the best coverage in the bin with the poorest model predictions. More importantly, only the Locally Valid and Discriminative (LVD) framework – particularly when operating on AION-1 embeddings – also provides finite-sample local validity, producing intervals that adapt to each galaxy's local prediction difficulty rather than relying on marginal guarantees alone. These results establish conformal prediction, and LVD in particular, as the preferred UQ framework for uncertainty-aware inference on foundation-model embeddings in astrophysics.
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Earth and Planetary Astrophysics

Towards Instrument-Agnostic Exoplanet Candidate Prioritization

Vivaswan Kopparapu, Sibasish Laha, Brian P. Powell et al. (+3 more)

We have developed a novel machine learning (ML) approach for predicting the likelihood of exoplanet candidate confirmation equally capable of performance on both TESS and Kepler data. From the NASA exoplanet archival post-processed Kepler and TESS databases, we chose six parameters that we assessed to be predictive to the planet transit signature: planet orbital period (P), planet radius ($R_{\rm p}$), stellar temperature ($T_{\rm eff}$), stellar radius ($R_{\rm star}$), planet transit depth ($\delta$), and planet transit duration ($t_{\rm d}$). We used these parameters to evaluate eleven different ML models on all possible train/test combinations of TESS and Kepler data, using the confirmed planet and false positive labels as our training targets. We found that, due to substantially different distributions of our chosen parameters in Kepler and TESS databases, models trained with data from one instrument have difficulty predicting the other. However, models trained jointly with both TESS and Kepler data can perform well on both. We combined our best models into a statistically robust ensemble to evaluate the planet candidates in both Kepler and TESS, and we provide a list of the top candidates predicted by our model for each. Confirmed planets and false positives that have been resolved since the completion of our analysis demonstrate the effectiveness of our model and suggest that our top candidates are likely to be confirmed if they are further analyzed by the community. With the upcoming launch of the Nancy Grace Roman Space Telescope (Roman) and the expected order-of-magnitude increase in planet candidates, we suggest that our method can be extended to Roman data for robust and effective prioritization for analysis.
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All authors Vivaswan Kopparapu, Sibasish Laha, Brian P. Powell, Veselin Kostov, Rajarshi Basak, Samuel Verbrugge

Instrumentation and Methods for Astrophysics

SynIM: a high-performance GPU-accelerated Python library for synthetic interaction and tomographic reconstruction matrices in next-generation adaptive optics

Guido Agapito, Fabio Rossi and Alfio Puglisi

Next-generation Adaptive Optics (AO) systems for 8-40m class telescopes, such as MORFEO (ELT) and MAVIS (VLT), demand high calibration accuracy. Controlling thousands of actuators makes experimental calibration unfeasible due to daytime overheads, environmental disturbances, and opto-mechanical aberrations. Consequently, model-based (synthetic) calibration has become the mandatory standard. We present SynIM, an open-source Python library designed for computing high-fidelity synthetic Interaction, Projection, and Covariance Matrices. SynIM leverages GPU acceleration via CuPy to handle the massive dimensionality of high-order systems. A core innovation is its handling of spatial geometry via composite affine transformations and absolute sub-pixel grid alignment. By merging DM and WFS shifts, rotations, and magnifications into a single operation, SynIM minimizes interpolation artifacts. SynIM introduces an optimized numerical derivative engine for slope computation that mathematically aligns spatial grids at the sub-pixel level, closely mimicking the physical behavior of Shack-Hartmann sensors. It outperforms geometric estimators like the G-tilt telescoping sum at high spatial frequencies, while yielding a substantial computational speed-up. Crucially, end-to-end MCAO simulations demonstrate that reconstructors built with SynIM deliver closed-loop AO performance practically equivalent to full physical optics models. SynIM natively supports SCAO, GLAO, MCAO, and LTAO configurations. It features optimized multi-WFS batch processing, modules for MMSE tomographic reconstructors, and full compatibility with SPRINT for online tracking. Currently driving the design and operational strategies for MORFEO, MAVIS, AOF, KAPA, and WST, SynIM stands as an essential tool for next-generation AO calibration.
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Instrumentation and Methods for Astrophysics

MORFEO wavefront error budget

Guido Agapito, Lorenzo Busoni, Cédric Plantet et al. (+2 more)

MORFEO (Multi-conjugate adaptive Optics Relay For ELT Observations, formerly MAORY) is the multi-conjugate adaptive optics module of the ESO Extremely Large Telescope (ELT), designed to deliver diffraction-limited performance in the near-infrared for its first-light camera MICADO. With its 12 wavefront sensors and three deformable mirrors, MORFEO stands as the largest and most complex adaptive optics system ever developed for astronomical observations. A key aspect of its design and verification is the construction of a comprehensive wavefront error (WFE) budget, which defines the system's expected performance under a range of operating conditions. In this work, we present the structure of the MORFEO WFE budget, detailing the main contributors to the residual error and the methodology adopted to evaluate each term. The analysis includes contributions from atmospheric turbulence, optical surfaces, alignment tolerances, control residuals, and calibration uncertainties. We also discuss the external conditions, system configurations, and key assumptions used in the derivation of the budget, highlighting the interplay between requirements and instrument design choices. Importantly, the resulting error budget is being used to support end-to-end simulations of MORFEO-assisted observations, providing essential input for assessing the scientific capabilities of the system and guiding the definition of future observing strategies.
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All authors Guido Agapito, Lorenzo Busoni, Cédric Plantet, Giulia Carlà, Jean-Pierre Véran

Astrophysics of Galaxies

A Colour-colour Fingerprint Links the UV Upturn in Early-type Galaxies to Second-generation Stars from Dissolved Globular Clusters

Paul Goudfrooij, Andrea Bellini, Thomas M. Brown et al. (+1 more)

We address two mass-dependent properties among early-type galaxies (ETGs): (1) abundance ratios [N/Fe] and [Na/Fe], and (2) the centrally concentrated "UV upturn" at far-UV (FUV) wavelengths, which is likely produced by extreme horizontal branch stars with supersolar helium abundances. Using new HST/WFC3 observations of one FUV-weak and one FUV-bright ETG, we probe the "MP scenario" by Goudfrooij who posited that the UV upturn and the mass-dependent abundance variations of N and Na within and among ETGs are physically connected and produced by dissolution of metal-rich globular clusters, which represent the only galactic environment where mass-dependent enrichment of He, N, and Na is known to occur (i.e., second-generation stars of the "multiple stellar populations" (MPs) phenomenon). We show that passbands F275W and F390W are uniquely sensitive to correlated changes in $Y$ and [N/Fe] in integrated-light photometry when combined with archival data in F475W and F850LP. While F475W-F850LP is found to decrease with increasing radius in both galaxies, consistent with known metallicity gradients, F275W-F390W increases with increasing radius, as expected if the UV upturn is caused by second-generation stars with supersolar $Y$ and [N/Fe]. Furthermore, the radial gradient in F275W-F390W and the implied fractions of He- and N-enhanced stars are found to be significantly larger in the FUV-bright ETG than in the FUV-weak one, consistent with the predictions of the MP scenario.
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All authors Paul Goudfrooij, Andrea Bellini, Thomas M. Brown, Thomas H. Puzia

Astrophysics of Galaxies

Euclid Quick Data Release (Q1): The impact of AGN emission on SED-derived physical properties

Euclid Collaboration: B. Laloux, A. Bongiorno, M. Salvato et al. (+308 more)

The Euclid Quick Data Release (Q1) is a powerful dataset to study active galactic nuclei (AGN) and their host galaxies. Deriving their physical properties through multi-component spectral energy distribution (SED) fitting is a challenging task for AGN, but it is greatly aided by the Euclid near-infrared photometry. Here we present a new method to quantify the reliability of SED-derived parameters, such as AGN bolometric and monochromatic luminosities, host's stellar mass $M_\star$, star-formation rate (SFR) and specific star-formation rate (sSFR), by using mock SEDs of AGN built by combining observed SEDs of QSOs and galaxies. We apply this methodology to the ${\sim}1$ million Q1 AGN candidates, constructing a catalogue of AGN and host galaxy properties, alongside their respective reliability values. With a reliability threshold at 0.5, we find 88% of sources with robust stellar masses and 76% with reliable AGN luminosities. Moreover, through SED fitting we also measure the AGN fraction $f_{\rm AGN}$ of the total mid-infrared flux and we use its lower-limit to select AGN. A $f_{\rm AGN, \, low} > 0.075$ threshold yields 85% completeness and purity. Comparable to colour-colour AGN selections, this method has the advantage of being less affected by redshift evolution and exploring fainter magnitudes. Additionally, by comparing the AGN and host galaxy parameters across different identification methods, we find that the probed range in stellar mass and AGN luminosity can be quite different. This highlights the importance of combining different approaches and accounting for their selection biases when studying AGN and their role in galaxy evolution. Finally, for the X-ray detected sample, we present the X-ray to mid-IR luminosity relation, and the correlation between stellar mass and bolometric luminosity as a function of redshift, in good agreement with previous results.
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All authors Euclid Collaboration: B. Laloux, A. Bongiorno, M. Salvato, V. Allevato, M. Mezcua, W. Roster, T. Matamoro Zatarain, S. Paltani, R. Shirley, F. Tarsitano, C. Saulder, S. Fotopoulou, C. Andonie, J. Buchner, F. La Franca, V. Le Brun, F. Ricci, D. Scott, F. Shankar, M. Siudek, J. G. Sorce, L. Spinoglio, Y. Toba, A. Viitanen, L. Wang, G. Zamorani, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Escoffier, M. Fabricius, M. Farina, R. Farinelli, S. Ferriol, F. Finelli, P. Fosalba, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, L. Gabarra, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. Gwyn, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, N. Mauri, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, P. Monaco, A. Mora, M. Moresco, C. Moretti, L. Moscardini, R. Nakajima, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, C. Porciani, L. Pozzetti, G. D. Racca, F. Raison, A. Renzi, J. Rhodes, G. Riccio, I. Risso, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, G. Seidel, S. Serrano, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, E. Zucca, M. Ballardini, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, T. Castro, J. A. Escartin Vigo, J. García-Bellido, R. Maoli, J. Martín-Fleitas, M. Maturi, R. B. Metcalf, M. Pöntinen, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, L. Bazzanini, D. Bertacca, M. Bethermin, L. Bisigello, A. Blanchard, L. Blot, M. Bonici, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, S. Conseil, A. R. Cooray, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, M. Y. Elkhashab, A. Enia, Y. Fang, A. Finoguenov, F. Fontanot, A. Franco, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, L. K. Hunt, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, M. Lattanzi, L. Legrand, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, L. Leuzzi, T. I. Liaudat, S. J. Liu, X. Lopez Lopez, J. Macias-Perez, E. A. Magnier, C. Mancini, A. Manjón-García, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, A. Montoro, G. Morgante, C. Murray, S. Nadathur, K. Naidoo, P. Natoli, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, G. Rodighiero, K. Rojas, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, D. Sciotti, E. Sellentin, L. C. Smith, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, A. Venhola, D. Vergani, G. Verza, P. Vielzeuf, S. Vinciguerra, N. A. Walton

Cosmology and Nongalactic Astrophysics

CMBolic: Symbolic emulators for the Cosmic Microwave Background. I. Lensing

David M. J. Vokrouhlicky, Constantinos Skordis, Deaglan J. Bartlett et al. (+2 more)

We present the first installment of CMBolic: a suite of symbolic cosmic microwave background (CMB) emulators. In this instance, we emulate the CMB lensing potential power spectrum $C_\ell^{\phi\phi}$ for the widely used extended $\Lambda$CDM model which simultaneously includes massive neutrinos and evolving dark energy modelled using the Chevallier-Polarski-Linder (CPL) parameterization. We achieve comparable precision to existing neural network emulators, with the added benefit of simpler handling as our emulators are analytic functions of the model parameters and multipole $\ell$. On independent validation spectra evaluated in the range $2\leq \ell \leq 5500$, CMBolic achieves mean absolute fractional errors of $0.27\%$ in the $\Lambda$CDM subspace and $0.32\%$ across the full extended parameter space. This emulation error is well below even the most optimistic noise forecasts from CMB Stage 4 experiments. We apply CMBolic to cosmological parameter estimation with Bayesian inference using the lensing-only likelihoods from ACT DR6 and Planck. We show excellent agreement between the posteriors obtained by CMBolic and the Boltzmann code CLASS. This demonstrates the practical use of CMBolic on cosmological parameter estimation, reducing the runtime from 2 weeks to under 3 minutes.
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All authors David M. J. Vokrouhlicky, Constantinos Skordis, Deaglan J. Bartlett, Harry Desmond, Pedro G. Ferreira

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

Core Composition Effects on the QCD Axion Mass Limit from Neutron Star Cooling

Fernando Arias-Aragón and Federico Nola

Neutron stars are very dense media in which axions may be produced. This has been used to set a limit on the QCD axion mass, usually under the assumption that only neutrons, protons, electrons, and muons appear in the star core. Given the extreme conditions reached within neutron stars, it is reasonable to consider that other particles, such as hyperons and $\Delta$ resonances, may appear in the neutron star core. In this work, we study how the limit on the mass of QCD axions, namely KSVZ and DFSZ invisible axions, is altered when different equations of state are used, allowing for heavier particles to appear in the neutron star core. We find that this dependence is in general mild and thus reinforces the reliability of the known limit. Additionally, in the DFSZ scenario, it may drive the limit within the sensitivity window for IAXO. This would allow this experiment to discern the composition of neutron star cores if an axion were to be observed within that window.
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Astrophysics of Galaxies

Clumps in a Cocoon: Geometry and Mixing Set the Universal X-ray to H$\alpha$ Surface Brightness Ratio

Zirui Chen, S. Peng Oh, Drummond B. Fielding et al. (+3 more)

Recent observations reveal a universal X-ray to H$\alpha$ surface-brightness ratio, ${\rm SB}_{\rm X}/{\rm SB}_{\rm H\alpha}\sim 3$, in galactic winds, ram-pressure stripped tails, and cluster filaments. This is surprising because H$\alpha$ traces cold ($\sim 10^4$ K) gas while X-rays trace much hotter ($\sim 10^{6}$–$10^{7}$ K) gas. Plane-parallel mixing-layer models do not recover this ratio, and can be off by orders of magnitude. Motivated by recent work showing that geometry controls the temperature PDF of multiphase gas (Chen & Oh 2026), we run 3D wind-tunnel simulations in the high density contrast ($\chi\sim 10^3$) regime. In this limit, the cold phase shatters into many small H$\alpha$-emitting clumps, while X-ray-emitting gas forms a volume-filling cocoon around them. After smoothing on the tail-width scale, the measured surface-brightness ratio converges to the observed value, which can be understood theoretically. The H$\alpha$ luminosity fraction is set by atomic physics, whereas the X-ray luminosity fraction is set by the residence time of gas in the X-ray-emitting band. This residence time is much shorter than the cooling time at X-ray temperatures, but scales roughly inversely with pressure, suggesting that it is tied to the cooling time at a lower-temperature outlet of the mixing cascade. This framework naturally explains why the observed ratio is order unity, and robust to changes in gas pressure.
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All authors Zirui Chen, S. Peng Oh, Drummond B. Fielding, Lachlan Lancaster, Yuan Li, Brent Tan

High Energy Astrophysical Phenomena

The Effects of Cosmic Ray Protons on Galactic Nonthermal Filaments

Mohan Richter-Addo, Roark Habegger, Ellen Zweibel et al. (+2 more)

The Galactic Center (GC) contains a collection of filaments that are typically tens of parsecs in length, illuminated by synchrotron radiation from cosmic rays (CR). The origin of these nonthermal filaments (NTFs) is unclear. We aim to distinguish two injection mechanisms: the first mechanism posits that NTFs are fueled either by jets from pulsar wind nebulae and are lepton-dominated; the second mechanism posits that NTFs are fueled by accelerated particles from interstellar shocks and are proton-dominated. We explore these mechanisms using the magnetohydrodynamics (MHD) code Athena++, modified to account for radiative and collisional losses, to simulate CR propagation with lepton and proton CR species. We vary parameters such as magnetic field strength, plasma density, and the CR diffusion coefficient to determine how the range of conditions present in the GC can affect CRs' propagation, heating, plasma flow, and the observed synchrotron emission. We find few observable differences between the proton- and lepton-dominated cases, but comparing the models with observed filament properties motivates consideration of a third formation mechanism: the generation of NTFs arise from intermittent structures in Galactic Center turbulence.
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All authors Mohan Richter-Addo, Roark Habegger, Ellen Zweibel, Dylan M. Paré, David T. Chuss

High Energy Astrophysical Phenomena · Cross-listed from nucl-th

NICER constraints on low density matching and high density continuation in neutron star equations of state

Federico Nola

We investigate whether current astrophysical data constrain not only the high-density continuation of the neutron star equation of state, but also the low density matching procedure itself. To this end, we compare two low density branches propagated through a common high density extension and confront them with direct NICER mass-radius posteriors, a lower bound on the maximum mass and an effective constraint on $\Lambda_{1.4}$. We find that the observable predictions of the two branches remain strongly overlapping, while the NICER-informed posterior still induces a nontrivial constraint on the matching parameters. Current data therefore constrain primarily the shared continuation above $n_1$, but also indirectly restrict the low density matching sector.
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High Energy Astrophysical Phenomena

The X-ray-to-UV relation does not evolve in homogeneous quasar samples

G. Risaliti, E. Lusso, E. Nardini et al. (+6 more)

We present a new, highly homogeneous quasar sample with X-ray and UV observations optimized to reliably estimate distances via the non-linear X-ray-to-UV relation. Cross-matching the Sloan Digital Sky Survey DR16 quasar catalog with the XMM-Newton serendipitous catalogue (4XMM–DR14), we employ strict selection criteria to build a robust sample: (1) UV and (2) X-ray colour constraints to avoid, respectively, extinction and absorption; (3) removal of broad absorption line and radio-bright quasars; (4) exclusion of sources at z<0.7 to prevent galactic UV contamination; and (5) rejection of sources with shallow X-ray observations. The latter step, closely related to the Eddington bias, is critical because SDSS data are generally deeper than X-ray data for typical quasar spectral energy distributions: ignoring such a discrepancy introduces a spurious redshift dependence in the X-ray-to-UV relation parameters. Our final sample contains about 2,000 quasars at z=0.7–5. We demonstrate that the X-ray-to-UV relation is constant across this redshift range, with a mean slope of 0.58\,$\pm$\,0.01 and a dispersion of 0.15 dex. Our findings confirm the intrinsic stability of this relation over cosmic time, emphasizing that both homogeneity and robust Eddington bias corrections are vital for flux-limited samples. In fact, the impact of the preferential detection of X-ray brighter-than-average sources near the effective sensitivity limits significantly grows with redshift. Any resulting evolutionary trend in the X-ray-to-UV relation, especially in the form a slope flattening, is therefore either a largely spurious effect, or the result of mixing populations of quasars with intrinsically different spectral properties.
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All authors G. Risaliti, E. Lusso, E. Nardini, C. Niccolai, M. Ralowski, A. Sacchi, A. Shlentsova, M. Signorini, B. Trefoloni

Earth and Planetary Astrophysics

GJ 3929 b as the First Complete Rocky Worlds DDT Data Set

Nicholas J. Connors, Christopher Monaghan, Björn Benneke et al. (+2 more)

Despite their large abundance, it is still unknown whether and under what conditions rocky planets around M dwarf stars can host atmospheres. This open question motivated the on-going Rocky Worlds DDT survey focused on searching for atmospheres on relatively low-temperature rocky exoplanets by systematically probing for the presence of day-night heat redistribution and CO2 absorption through JWST/MIRI 15 $\mu$m eclipse observations. Here we present the analysis of the first full data set from this survey, consisting of four observations of the warm Earth-size exoplanet GJ 3929 b, with a planetary mass of 1.75+0.44-0.45 M$_\oplus$ and instellation flux of 17.3+/-0.7 S$_\oplus$. In our analysis, we include two previously unpublished eclipse observations and find an overall eclipse depth of 118+/-22 ppm and a dayside surface brightness temperature of 641+59-64 K. This is marginally lower than the eclipse depth of 160+26-27 ppm previously reported based on only the first two observations. While the full data set remains consistent with bare rock scenarios, it also leaves more room for thin atmosphere scenarios. Only thick CO2 atmospheres without thermal inversion remain ruled out at greater than 3$\sigma$. We also continue with lessons-learned in robustly analyzing these kind of high-precision JWST/MIRI 15 $\mu$m eclipse observations. Notably, we find that the Frame Normalized Principal Component Analysis (FN-PCA) method appears more robust against the choice of extraction aperture size, which otherwise can have a significant impact on the inferred eclipse depth and scientific conclusions when using a standard polynomial baseline detrending method.
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All authors Nicholas J. Connors, Christopher Monaghan, Björn Benneke, Lisa Dang, Pierre-Alexis Roy

High Energy Astrophysical Phenomena

Primordial Black Hole Triggered Type Ia Supernovae II: Comparison with Supernova Remnants and Galactic Chemical Evolution

Shing-Chi Leung, Seth Walther, Alexander Kusenko et al. (+2 more)

The asteroid-mass class of Primordial Black Holes (PBHs) is one of the candidates for the dark matter in the universe. With a mass between $4 \times 10^{-17} < M_{\rm PBH} < 4 \times 10^{-12}~M_{\odot}$, they could be the major component of dark matter in the cosmic mass budget. The infall of these PBH into a white dwarf could be one triggering mechanism of Type Ia supernovae (SNe Ia). In [Leung et al, ApJ 991, 11 (2025)] (Paper I), we studied the ignition, explosion dynamics, radiative transfer, and post-explosion nucleosynthesis of the PBH-triggered SNe Ia. The diversity of the explosion models can reconcile with the empirical Phillips relation. In this work, we developed the PBH-triggered SN Ia models in various metallicity. We show that models from this channel can explain some recently observed SN Ia light curves and supernova remnants. We further investigate how these supernovae could affect the chemical evolution on the galactic scale by adding the new SN Ia models as a new chemical source. We examine how the observed chemical trends of stars can lead to constraints on the fraction of this explosion channel relative to the canonical binary star channel. Our models suggest that the PBH can be one major SN Ia channel in the early universe. We also include a comparative study to extract the effects of PBH-triggered SN Ia parameters on the actual chemical trends in the galactic chemical evolution model.
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All authors Shing-Chi Leung, Seth Walther, Alexander Kusenko, Ken'ichi Nomoto, Tomoharu Suzuki

Earth and Planetary Astrophysics

The Roasting Marshmallows Program with IGRINS on Gemini South V: Atmosphere of MASCARA-1b is Enriched in Refractory Elements

Krishna Kanumalla, Michael R. Line, Martina Chiarella et al. (+75 more)

Ultra-hot Jupiters (UHJs; $T_{\rm eq} \gtrsim 2000$ K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) species in planetary atmospheres, providing a powerful diagnostic of planet formation and atmospheric processing. We present a comprehensive high-resolution cross-correlation spectroscopy (HRCCS) analysis of the UHJ MASCARA-1b ($T_{\rm eq} \approx 2600$ K) using the IGRINS and IGRINS-2 spectrographs. We detect robust (SNR$>$4) signals from H$_2$O, CO, OH, Fe I, Mg I, Ca I, and Ti I, marking the most complete atmospheric inventory of MASCARA-1b to date. Using a chemically consistent atmospheric inference framework, we constrain elemental abundances to a typical precision of $\approx$0.2 dex, retrieving a solar atmospheric metallicity ([M/H]$_\odot$ $= 0.07^{+0.17}_{-0.13}$ $\approx 1.2\times$ solar), a C/O ratio (C/O $= 0.65^{+0.08}_{-0.08}$) consistent with solar value (C/O $=$ 0.59), an enhanced refractory abundance ([R/H]$_\odot$ $= 0.40^{+0.23}_{-0.17} \approx 2.5\times$ solar; $\approx 3.8\times$ stellar), and a moderately super-solar refractory-to-volatile ratio ([R/V]$_\odot$ $= 0.36^{+0.11}_{-0.09}$ $\approx 2.3\times$ solar). Comparison with formation models suggests that MASCARA-1b most likely accreted material between the soot-H$_2$O or H$_2$O-CO snowlines (at 68$\%$ confidence). We additionally find stellar values for atmospheric Ti/Mg and Ca/Mg ratios (at 68$\%$ confidence). The Mg/Fe is also found to be consistent with stellar value at 95$\%$ confidence. Therefore, we do not find strong indication of nightside cold trapping in MASCARA-1b. As homogeneous refractory-to-volatile measurements expand across the UHJ population, particularly with upcoming Extremely Large Telescopes, these diagnostics will enable statistically robust tests of emerging trends in giant planet formation and atmospheric evolution.
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All authors Krishna Kanumalla, Michael R. Line, Martina Chiarella, Matteo Brogi, Peter C. B. Smith, Jorge A. Sanchez, Yayaati Chachan, Joshua Lothringer, Joost P. Wardenier, Hayley Beltz, Carlos Saffe, Emily K. Deibert, Megan Weiner Mansfield, Stefan Pelletier, Vivien Parmentier, Yeon-ho Choi, Swaetha Ramkumar, Arjun B. Savel, Luis Welbanks, Jacob L. Bean, Vatsal Panwar, Tomás Azevedo Silva, Lorenzo Pino, Yuya Hayashi, Dongwook Lim, Cicero X. Lu, Venu M. Kalari, Teo Močnik, Mark G. Rawlings, Heeyoung Oh, Ruben J. Diaz, Chan Park, Jae-Joon Lee, Sanghyuk Kim, Ueejeong Jeong, Hye-In Lee, Woojin Park, Youngsam Yu, Yunjong Kim, Moo-Young Chun, Jae Sok Oh, Sungho Lee, Jeong-Gyun Jang, Bi-Ho Jang, Hyeon Cheol Seong, Hyun-Jeong Kim, Cynthia B. Brooks, Gregory N. Mace, Hanshin Lee, John M. Good, Daniel T. Jaffe, Kang-Min Kim, In-Soo Yuk, Narae Hwang, Byeong-Gon Park, Hwihyun Kim, Brian Chinn, Francisco Ramos, Pablo Prado, John White, Andres Olivares, Valentina Oyarzun, Emma Kurz, Hawi Stecher, Carlos Quiroz, Ignacio Arriagada, Thomas L. Hayward, Hyewon Suh, Jen Miller, Siyi Xu, Emanuele Paolo Farina, Charlie Figura, Andrew Stephens, Bryan Miller, Kathleen Labrie, Paul Hirst, Edo Tapia, Zachary Hartmann

Earth and Planetary Astrophysics

A New Scaling Law for Non-Dipolar Magnetic Fields in Rapidly Rotating Stars and Planets

Paula N. Wulff, Hao Cao and Jonathan M. Aurnou

Magnetic field generation in giant planets and rapidly rotating stars produces a diverse range of field geometries, from large-scale dipole-dominated configurations to complex, small-scale multipolar structures. Earlier dynamo studies have suggested that multipolar solutions tend to arise when rotational effects become less dominant. We investigate the strength of non-dipolar magnetic fields generated in systems dominated by rotation. 40 three-dimensional, spherical-shell dynamo simulations were carried out using the MagIC code, primarily made up of bistable pairs - simulations with the same control parameters that can settle in both a dipolar and non-dipolar steady-state regime. We use this suite of models to test how their magnetic field strength scales with heat flux and velocity. Our dynamo simulations produce magnetic fields with morphologies that fall on the two distinct branches, dipolar or non-dipolar, yet have very similar convective velocities. The strength of the dipole component differs by an order of magnitude between the two regimes, when scaled as a function of driving power. However, their non-dipolar magnetic field strengths are very similar. We conclude that when attempting to predict the magnetic field strength of rapidly rotating planets and stars, one cannot assume that it will have a dipole-dominated geometry. In particular, the amplitude of the dipole component is expected to be an order of magnitude smaller in the non-dipolar regime.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Stochastic scalar-tensor inflation and beyond

Yoann Launay

During cosmological inflation, inhomogeneities arising from quantum vacuum fluctuations are stretched to become super-Hubble and effectively classical. As many scenarios of the origin involve nonlinearities or a breakdown of perturbativity in the infrared, the limitations of quantum field theory can be addressed using a stochastic description of the dynamics, the so-called stochastic inflation paradigm. However, the stochastic formalism was only recently formulated consistently within full General Relativity and has not yet been extended to more general theories of the early universe, which is the subject of this work. In order to find the stochastic sources for a wide class of fully nonlinear scalar-tensor theories, we apply our gauge-agnostic coarse-graining procedure to the linear equations of the associated effective field theory. Each theory can then be mapped to its own set of stochastic equations of motion by identifying the corresponding coefficients in the former. We illustrate this with a few concrete and, in most cases, unprecedented examples, including Gauss-Bonnet, generalized Brans-Dicke, Horndeski, and braiding theories. Finally, we discuss other natural extensions to provide a phenomenologically complete stochastic framework. For example, we showcase the coarse-graining of multifield inflation in full General Relativity and argue for the generality of our procedure and thus its potential applications beyond the realm of inflation.
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High Energy Astrophysical Phenomena

The Western Jet of SS 433/W50: Hard X-ray Emission, Spectral Evolution, and Comparison to the Eastern Jet

Brydyn Mac Intyre, Samar Safi-Harb, Dmitry Khangulyan et al. (+5 more)

The W50 nebula powered by the microquasar SS 433 is a unique laboratory for exploring several fundamental astrophysical phenomena. This study presents observations from NuSTAR and XMM-Newton, concentrating on the western lobe of W50. Detection of hard non-thermal X-ray emission is reported, extending up to approximately 30 keV. This emission originates from a compact, knotty area referred to as the "Head", located at approximately 17 arcmin (equivalent to 26.5 pc at an assumed distance of 5.5 kpc) to the west of SS 433, and characterized by a power-law spectrum with a hard photon index of 1.55 +/- 0.07 (0.5-30 keV). Moving westward from SS 433, the photon index gradually steepens, ultimately reaching a photon index of 2.10 +/- 0.05 in the "w2" region centered at approximately 35 arcmin or approximately 56 pc from SS 433. The distinct hard X-ray knots observed serve as clear markers for sites of particle acceleration within the western jet. The synchrotron radiation from the "Head" region implies equipartition magnetic field strength B of approximately 15 microG. Notably, these properties (western "Head" location, unusually hard spectral index, inferred magnetic field, and spectral evolution away from SS 433) are very similar to what has been observed in the eastern lobe, supporting a symmetric jet-driven origin. Finally, the broadband spectral energy distribution (SED) and X-ray morphology are modeled using semi-analytic jet models, exploring different jet velocity and magnetic field configurations. The results favor a scenario in which in-situ particle acceleration and synchrotron emission dominate, with implications for understanding particle transport, jet dynamics, and W50's role as a Galactic PeVatron.
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All authors Brydyn Mac Intyre, Samar Safi-Harb, Dmitry Khangulyan, Shuhan Zhang, Kaya Mori, Naomi Tsuji, Felix Aharonian, Laura Olivera-Nieto

Astrophysics of Galaxies

Polarized and unpolarized synchrotron emission from dark matter in extragalactic targets

Javier Reynoso-Cordova, Catherine Gibson and Stefano Profumo

We compute 95% confidence-level upper limits on the dark matter annihilation cross section and decay rate from both total-intensity and polarized synchrotron emission in five extragalactic targets: M31, the Large Magellanic Cloud (LMC), the Draco and Sculptor dwarf spheroidal galaxies, and the Coma cluster. Using Planck maps at 30, 44, and 70 GHz, we solve the diffusion-loss equation for dark-matter-produced electrons and positrons numerically with DRAGON and integrate the resulting synchrotron emission along the line of sight with HERMES, computing both total-intensity and polarized-intensity maps for each target with target-specific magnetic-field, gas, and radiation-field environments. The 30 GHz channel yields the most stringent constraints in all cases, and limits on annihilation or decay into $e^+e^-$ are stronger than those for $b\bar{b}$ due to the harder injected spectrum. For most targets the total-intensity and polarized limits are broadly comparable; the LMC is an exception, where Faraday depolarization in the turbulent disk suppresses the polarized signal relative to total intensity, making total intensity the primary estimator. Our results are robust against the choice of flux estimator and coordinate uncertainty. This work demonstrates that microwave polarimetry provides a complementary and largely independent probe of dark matter synchrotron emission in extragalactic targets.
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Astrophysics of Galaxies

Dust in the very metal-poor galaxy Sextans A with JWST. I: Characterizing the evolved stellar population of Sextans A based on JWST observations and stellar evolution models

C. Gavetti, F. Dell'Agli, E. Tarantino et al. (+22 more)

The nearby star-forming dwarf galaxy Sextans A offers a unique window into galaxy evolution in the early Universe, owing to its extremely low metallicity (about 1-7% Zsun). Recent JWST imaging of Sextans A spanning 1-21 micron enables a detailed characterization of its dusty stellar populations and interstellar medium. In this work, we compare the observed JWST color-magnitude distributions of evolved stars with stellar evolution and dust-formation models to characterize the properties of the asymptotic giant branch (AGB) population, including progenitor mass, formation epoch, metallicity, and dust production. Evolutionary tracks for 0.8-7 Msun stars with metallicity Z=10^-3 provide good agreement with the overall distribution of AGB stars in Sextans A. More than 90% of the AGB population occupies a nearly vertical sequence in the color-magnitude diagrams, corresponding to stars spanning a wide range of masses and ages but exhibiting little or no circumstellar dust. This sequence appears to be dominated by oxygen-rich (M-type) AGB stars and reveals that the F444W flux is a robust luminosity diagnostic. A small subset of sources displays strong infrared excesses and is dominated by carbon stars descending from 1.25-1.5 Msun progenitors that formed about 2-3 Gyr ago and are currently in the final AGB phases. Their MIRI colors imply very low metallicities, consistent with estimates from the red giant branch morphology (about 1-2% Zsun). Finally, we show that the JWST/NIRCam F277W-F444W color serves as an effective proxy for the dust production rate, with models predicting rates up to 10^-7 Msun/yr for the reddest sources in Sextans A.
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All authors C. Gavetti, F. Dell'Agli, E. Tarantino, M.L. Boyer, I. McDonald, J.Th. Van Loon, D.A. Garcia-Hernandez, M.A.T. Groenewegen, A. Nanni, J.A.D.L. Blommaert, R.D. Gehrz, L.M. Gerlach, S. Goldman, M. Marengo, K.B.W. McQuinn, J.M. Oliveira, J. Roman-Duval, R. Sahai, E.D. Skillman, B.F. Williams, A. Javadi, O.C. Jones, F. Kemper, F. La Franca, G. C Sloan