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Physics Astrophysics

astro-ph Watch Astrophysics

Sunday 30 November

High Energy Astrophysical Phenomena

Tidal disruption and evaporation of rubble-pile and monolithic bodies as a source of flaring activity in Sgr A^\star$

Wen-Han Zhou, Yun Zhang, Jiamu Huang et al. (+1 more)

Sgr A*, the supermassive black hole at the center of the Milky Way, exhibits frequent short-duration flares with luminosity greater than 1e34 erg/s across multiple wavelengths. The origin of the flares is still unknown. We revisited the role of small planetary bodies, originally from the stellar disk, and their tidally disrupted fragments as a source of flaring activity in Sgr A*. We refined previous models by incorporating material strength constraints on the tidal disruption limit and by evaluating the evaporation dynamics of the resulting fragments. We analyzed the tidal fragmentation and gas-induced fragmentation of small planetary bodies with rubble-pile and monolithic structures. Using constraints from recent space missions (e.g., NASA OSIRIS-REx and JAXA Hayabusa2), we estimated the survivability of fragments under aerodynamic heating and computed their expected luminosity from ablation, modeled as fireball flares analogous to meteor events. We find that planetary fragments can approach as close as 8 gravitational radii, consistent with observed flare locations. The fireball model yields luminosities from 1e34 to 1e36 erg/s for fragments whose parent bodies are a few kilometers in size. The derived flare frequency vs. luminosity distribution follows a power law with index 1.83, in agreement with observed values (1.65 - 1.9), while the flare duration scales as L^(-1/3), consistent with observations. We consider the young stars around Sgr A* as the planetary reservoir. Given a small-body population analogous in mass to the primordial Kuiper belt and the common existence of close-in super-Earths and long-period Neptunes, we show that this planetary reservoir can supply the observed flares.
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All authors Wen-Han Zhou, Yun Zhang, Jiamu Huang, Douglas N.C. Lin

Astrophysics of Galaxies

Green Bean galaxies and the fading echoes of AGN activity

A. Arshinova, K. Sanderson and A. Moiseev

Green Bean is a rare type of galaxy which represents a short-lived phase in the life cycle of active galactic nuclei (AGN), characterised by large-scale, powerful ionised clouds in the circumgalactic medium. Recent studies demonstrate that these extended ionised structures may reflect fading signatures of past AGN activity, often manifested in the form of large-scale ionisation cones. The analysis of their observational properties provides unique constraints on AGN lifetimes, feedback mechanisms, and transitions between radiative and kinetic modes of activity. In this paper we announce the first results of the project dedicated to the long-slit spectroscopic and scanning Fabry-Perot interferometric observations of Green Bean galaxies at the Russian 6-m telescope with SCORPIO-2 multi-mode instrument. We describe the data reduction and spectral fitting procedures that allow one to characterise ionisation conditions in extended gaseous regions of the galaxy SDSSJ095100.54+051026.7.
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Solar and Stellar Astrophysics

Asteroseismic detection of a predominantly toroidal magnetic field in the deep interior of the main-sequence F star KIC 9244992

Masao Takata, Simon J. Murphy, Donald W. Kurtz et al. (+2 more)

An asteroseismic analysis has revealed a magnetic field in the deep interior of a slowly-rotating main-sequence F star KIC9244992, which was observed by the Kepler spacecraft for four years. The star shows clear asymmetry of frequency splittings of high-order dipolar gravity modes, which cannot be explained by rotation alone, but are fully consistent with a model with rotation, a magnetic field and a discontinuous structure (glitch). Careful examination of the frequency dependence of the asymmetry allows us to put constraints on not only the radial component of the magnetic field, but also its azimuthal (toroidal) component. The lower bounds of the root-mean-squares of the radial and azimuthal components in the radiative region within 50 per cent in radius, which have the highest sensitivity in the layers just outside the convective core with a steep gradient of chemical compositions, are estimated to be $\mathsf{B}_{\mathrm{r}}^{\min}=3.5 \pm 0.1$ kG and $\mathsf{B}_{\phi}^{\min}=92 \pm 7$ kG, respectively. The much stronger azimuthal component than the radial one is consistent with the significant contribution of the differential rotation although the star has almost uniform rotation at present. The estimated field strengths are too strong to be explained by dynamo mechanisms in the radiative zone associated with the magnetic Tayler instability. The aspherical glitch is found to be located in the innermost radiative layers where there is a steep gradient of chemical composition. The first detection of magnetic fields in the deep interior of a main-sequence star sheds new light on the problem of stellar magnetism, for which there remain many uncertainties.
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All authors Masao Takata, Simon J. Murphy, Donald W. Kurtz, Hideyuki Saio, Hiromoto Shibahashi

High Energy Astrophysical Phenomena

Can the Efron-Petrosian Method Recover the Inverse-Square Distance Law for Simulated Radio Pulsar Fluxes?

Sanjith A. and Shantanu Desai

We test whether the Efron-Petrosian (E-P) method can recover the inverse-square law dependence of the radio pulsar flux, using a synthetic catalog generated according to the specifications of the Parkes Multi-beam survey using the PsrPopPy software. We find that the E-P method cannot automatically reproduce the inverse-square scaling law for the radio pulsar flux, even though this scaling is built into the synthetic data by construction, except over a narrow range of flux thresholds, and even here we don't get pristine agreement. The main reason for the deviation is that the synthetic radio pulsar catalog is truncated based on a cut on the pulsar signal to noise ratio (SNR), which has a non-linear dependence on the flux along with considerable scatter. We show that the disagreement is exacerbated as we raise the SNR threshold. We then demonstrate that if we create a synthetic catalog based on a flux cut (instead of an SNR-based threshold), we can recover the true distance exponent, with an accuracy ranging from pristine agreement to within $\pm 1 \sigma$ depending on the chosen flux threshold. Therefore, the E-P method cannot be used to determine the correct scaling of radio pulsar flux with distance. Our results also demonstrate that the E-P method breaks down when the detection threshold scales non-linearly with flux along with scatter.
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Astrophysics of Galaxies · Cross-listed from cs.LG

AI Agent for Source Finding by SoFiA-2 for SKA-SDC2

Xingchen Zhou, Nan Li, Peng Jia et al. (+7 more)

Source extraction is crucial in analyzing data from next-generation, large-scale sky surveys in radio bands, such as the Square Kilometre Array (SKA). Several source extraction programs, including SoFiA and Aegean, have been developed to address this challenge. However, finding optimal parameter configurations when applying these programs to real observations is non-trivial. For example, the outcomes of SoFiA intensely depend on several key parameters across its preconditioning, source-finding, and reliability-filtering modules. To address this issue, we propose a framework to automatically optimize these parameters using an AI agent based on a state-of-the-art reinforcement learning (RL) algorithm, i.e., Soft Actor-Critic (SAC). The SKA Science Data Challenge 2 (SDC2) dataset is utilized to assess the feasibility and reliability of this framework. The AI agent interacts with the environment by adjusting parameters based on the feedback from the SDC2 score defined by the SDC2 Team, progressively learning to select parameter sets that yield improved performance. After sufficient training, the AI agent can automatically identify an optimal parameter configuration that outperform the benchmark set by Team SoFiA within only 100 evaluation steps and with reduced time consumption. Our approach could address similar problems requiring complex parameter tuning, beyond radio band surveys and source extraction. Yet, high-quality training sets containing representative observations and catalogs of ground truth are essential.
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All authors Xingchen Zhou, Nan Li, Peng Jia, Yingfeng Liu, Furen Deng, Shuanghao Shu, Ying Li, Liang Cao, Huanyuan Shan, Ayodeji Ibitoye

High Energy Astrophysical Phenomena

Broadband Spectral Analysis of 1ES2344+514: A Multi-epoch study

Kishor Chaudhury, Abhradeep Roy, Varsha R. Chitnis et al. (+2 more)

We present the results of the multi-epoch broadband spectral study of 1ES 2344+514 and study the evolution of physical parameters. We used nearly simultaneous data obtained from 2017 June 6 to 2022 August 6 (MJD 57910 – 59797) in optical, UV, X-ray and $\gamma$-ray wavebands from various instruments including Swift-UVOT, Swift-XRT, NuSTAR, AstroSat (SXT and LAXPC), Fermi-LAT, and TeV flux from MAGIC. During 2017 July, 1ES 2344+514 appeared to be in the highest flaring state compared to other periods. We used the 0.5 – 7.0 keV and 3.0 – 20.0 keV data, respectively, from SXT and LAXPC of AstroSat and also 0.3 – 8.0 keV and 3.0 – 79.0 keV data, respectively, from Swift-XRT and NuSTAR. A joint fit between SXT and LAXPC, and between Swift-XRT and NuSTAR has been done for constraining the synchrotron peak. A clear shift in the synchrotron peak has been observed, which included 1ES 2344+514 in the HSP BL Lac family. A `harder-when-brighter' trend is observed in X-rays, and the opposite trend, i.e., `softer-when-brighter', is seen in the $\gamma$-rays. The multi-epoch broad-band spectral energy distributions (SEDs) of this source were built and studied to get an idea of the radiation processes. The SEDs were fitted using a steady-state leptonic one-zone synchrotron+SSC model, and the fitted parameters of the emission region are consistent with those of other TeV BL Lacs. In this study, we found a weak correlation tendency between bolometric luminosity and magnetic field (B), as well as between bolometric luminosity and the break Lorentz factor ($\gamma_{break}$).
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All authors Kishor Chaudhury, Abhradeep Roy, Varsha R. Chitnis, Prajval Shastri, Rajat K. Dey

Astrophysics of Galaxies

A source-plane reassessment of the z=6–8 ultraviolet luminosity function behind Abell 2744: no requirement for additional faint-end curvature

Xuheng Ma

We reassess the rest-frame ultraviolet luminosity function (UVLF) at $6\leq z<8$ behind Abell~2744 using public UNCOVER imaging, catalog photometry, and lens products. Observed sources use the released D032 aperture-to-total-corrected photometry; artificial sources use 0.32-arcsec forced apertures with profile- and band-specific corrections to the same total-flux scale. The joint detection and seven-band selection response is calibrated with 1380 artificial sources inside a common $33.36\,\mathrm{arcmin}^{2}$ footprint. Rest-frame $M_{1500}$ is derived from EAZY spectral-energy-distribution fits at eight conditional-redshift-posterior nodes, and the same definition is used to recompute branch-aware source-plane effective volumes. Synthetic F814W flux from the fitted SED and intergalactic absorption is propagated through EAZY and the selector at each volume node. The final sample contains 161 registry-de-duplicated physical sources; 111 and 36 lie in the reliable B6 ($6\leq z<7$) and B7 ($7\leq z<8$) fitting ranges. Bin-integrated Poisson fits give curved-minus-Schechter $\Delta\mathrm{AIC}=+4.00$ and $+2.85$, and $\Delta\mathrm{BIC}=+5.13$ and $+3.82$, respectively. A response-recalibrated stricter posterior subset and a catalog-level aperture-correction bridge do not reverse the ranking. Thus the calibrated data do not require additional faint-end curvature beyond an unrestricted Schechter function; they do not establish that a turnover is absent at fainter luminosities or in the cosmic-mean UVLF.
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Solar and Stellar Astrophysics

SMSS J022423.27$-$573705.1: An Extremely Metal-Poor Star with the Most Pronounced Weak $r$-Process Signature

Hiroko Okada, Wako Aoki, Nozomu Tominaga et al. (+1 more)

We present the measurement of 26 elemental abundances of SMSS J022423.27$-$573705.1 (SMSS 0224$-$5737), an extremely metal-poor (EMP) star with a weak $r$-process signature. We report the measurements of N, O, V, Zn, and Ba, and the upper limits for Mo, Ru, Pd, Ag, and Eu for the first time. SMSS 0224$-$5737 exhibits low C abundance and high N and O abundances suggesting that C is converted to N by the enhanced mixing during the evolution. The abundance pattern up to the Fe-peak elements is generally in good agreement with the average abundance of EMP stars, although a notable feature is the high [Zn/Fe] ratio ([Zn/Fe] $= +0.88$). We confirm the enhancement of the first-peak neutron-capture elements (Sr, Y, and Zr) and determine a low Ba abundance [Ba/H] $= -5.25$, that is, [Ba/Fe] $= -1.45$. The extremely high ratio of [Zr/Ba] $= +2.60$ makes SMSS 0224$-$5737 the EMP star with the most pronounced weak $r$-process signature observed to date. The abundance pattern of the neutron-capture elements is compared with the yields from $r$-process nucleosynthesis models. The sharp decline in abundances beyond Zr disfavors neutron star merger or electron-capture supernova models, but are reproduced either by proto-neutron star wind models or by magneto-rotational supernova models. Considering the high [Zn/Fe] ratio, a magneto-rotational supernova is the most plausible origin of SMSS 0224$-$5737. This study demonstrates that the abundance measurements of both light and neutron-capture elements, even at low abundances, are crucial for unveiling the astrophysical sites of the weak $r$-process.
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All authors Hiroko Okada, Wako Aoki, Nozomu Tominaga, Satoshi Honda

Solar and Stellar Astrophysics

Evolution of Flare Ribbon Bead-like Structures in a Solar Flare

Ryan J. French, Maria D. Kazachenko, David Berghmans et al. (+6 more)

We present fast cadence and high resolution observations of flare ribbons from the Solar Orbiter Extreme Ultraviolet Imager (EUI). Utilizing the short-exposure observations from the EUI High Resolution Imager in EUV (HRIEUV), we find small-scale blob/bead-like kernel structures propagating within a hook at the end of a flare ribbon, during the impulsive phase of a C9.9-class solar flare. These bead structures are dynamic, with well-resolved spatial separations as low as ~420-840 kilometers (3-6 pixels) - below the observable limit of full-disk solar imagers. We analyze the evolution of the plane-of-sky apparent velocity and separation of the flare ribbon structures, finding evidence for multiple processes occurring simultaneously within the flare ribbon. These processes include - quasi-periodic pulsation (QPP)-like brightenings, slow back-and-forth zig-zag motions along the ribbon, rapid apparent motions along the ribbon (600+ km/s), and stationary blob-like structures. Finally, we conduct Fast Fourier Transform analysis and analyze the start times of exponential growth in the power spectrum at different spatial scales across the flare ribbon. Our analysis reveals that the ribbon beads form with a key spatial separation of 1.7-1.9 Mm, before developing into more complex structures at progressively larger and smaller spatial scales. This observation is consistent with predictions of the tearing mode instability.
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All authors Ryan J. French, Maria D. Kazachenko, David Berghmans, Elke D'Huys, Marie Dominique, Ritesh Patel, Dana-Camelia Talpeanu, Cole A. Tamburri, Rahul Yadav

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

Probing a minimal dark gauge sector via microlensing of compact dark objects

Juan Barranco, Argelia Bernal, Víctor Jaramillo et al. (+2 more)

We introduce a minimal Dark Standard Model (DSM) consisting of a single spin-0 particle with dark $U(1)$ gauge symmetry, and completely decoupled from the visible sector. Characterized only by the scalar mass $\mu$ and the dark charge $q$, this framework naturally gives rise to a rich phenomenology, including stable solitonic configurations that behave as dark "mini-MACHOs". We numerically build and evolve these gauged scalar-field solitons, derive their mass-radius relations, and identify a critical charge beyond which no gravitationally bound configurations exist. By combining these results with microlensing surveys that exclude compact objects heavier than the asteroid-mass scale ($M\lesssim 10^{-11}M_\odot$), we obtain the constraint $\mu\gtrsim 10\,\rm eV$ for viable configurations, depending on $q$. Our results represent a step forward in showing that purely gravitational observations can constrain the internal parameters of a dark gauge sector, and provide a framework for exploring broader DSM scenarios through future probes such as gravitational wave detections.
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All authors Juan Barranco, Argelia Bernal, Víctor Jaramillo, Darío Núñez, Milton Ruiz

Saturday 29 November

Cosmology and Nongalactic Astrophysics

How Dark is Dark Energy? A Lightcones Comparison Approach

Mauro Carfora and Francesca Familiari

We present a geometrical approach that provides a non-perturbative technique, allowing the standard FLRW observer to evaluate a measurable, scale-dependent distance functional between her idealized FLRW past light cone and the actual physical past light cone. From the point of view of the FLRW observer, gathering data from sources at cosmological redshift $\widehat{z}$, this functional generates a geometry–structure–growth contribution ${\Omega_\Lambda(\widehat{z})}$ to the FLRW cosmological constant ${\widehat\Omega_\Lambda}$. This redshift–dependent contribution erodes the interpretation of ${\widehat\Omega_\Lambda}$ as representing constant dark energy. In particular, ${\Omega_\Lambda(\widehat{z})}$ becomes significantly large at very low $\widehat{z}$, where structures dominate the cosmological landscape. At the pivotal galaxy cluster scale, where cosmological expansion decouples from the local gravitation dynamics, we get ${\Omega_\Lambda(\widehat{z})/\widehat\Omega_\Lambda}\,=\,\mathscr{O}(1)$, showing that late–epoch structures provide an effective field contribution to the FLRW cosmological constant that is of the same order of magnitude as its assumed value. We prove that ${\Omega_\Lambda(\widehat{z})}$ is generated by a scale-dependent effective field governed by structure formation and related to the comparison between the idealized FLRW past light cone and the actual physical past light cone. These results are naturally framed in the mainstream FLRW cosmology; they do not require exotic fields and provide a natural setting for analyzing the coincidence problem, leading to an interpretative shift in the current understanding of constant dark energy.
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Cosmology and Nongalactic Astrophysics

Controlling weak-lensing shear biases from undetected galaxies in the era of Stage IV Surveys

Lisa M Voigt

Gravitational lensing of background galaxies by intervening matter is a powerful probe of the cosmological model. In the era of Stage IV surveys, contamination from galaxies below the detection threshold has emerged as a significant source of bias. Adopting a noise-bias-free machine-learning method to estimate shear, we quantify the impact of faint galaxies for a Euclid-like survey. In our baseline simulations, faint blends induce a multiplicative shear bias of -0.008, well above Euclid's requirement. Similar to previous studies, we find that calibration simulations must include neighbouring galaxies to AB apparent magnitudes as faint as 27.0 (+2.1, -0.9) and within approximately 1.0 (+0.2, -0.2) arcsec of each bright sample galaxy (BSG; the galaxy for which shear is measured). By varying faint galaxy properties, we identify which ones significantly affect shear biases and quantify how well they must be constrained. Crucially, we find that biases not only depend on the mean projected faint-galaxy density and apparent-magnitude distribution across the sample, but also on how these quantities vary with the observed brightness of the BSG. Furthermore, biases are sensitive to radial and tangential alignments and positional anisotropy of faint galaxies relative to BSGs. By contrast, shear coherence between BSGs and faint galaxies, parallel orientation alignments, and variations in the faint galaxy size-magnitude relation have negligible impact within the parameter ranges explored. Our results guide calibration simulations and highlight the critical role of deep observations in measuring the properties of faint galaxies.
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High Energy Astrophysical Phenomena

Particle Astrophysics with High and Ultrahigh Energy Neutrinos

Ke Fang and Kohta Murase

We summarize recent results of the observations of high (1 TeV-100 PeV) and ultrahigh ($\geq 100$ PeV) energy neutrinos, including the detection of a diffuse cosmic high-energy neutrino background, the identification of the first neutrino source candidates, and the observation of high-energy neutrinos from the Galactic plane. These findings open a new window to the universe by enabling the use of neutrinos to probe the cosmos that are otherwise inaccessible via photons. Although the origins of most detected neutrinos remain uncertain, we highlight several distinctive features of their sources that have emerged from current observations.
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Astrophysics of Galaxies

Uniformly-calibrated VPHAS+ photometry in the third quadrant of the Galactic plane

J. E. Drew, R. Greimel, J. Eislöffel et al. (+2 more)

The southern Galactic plane has been mapped at optical wavelengths and at under one-arcsecond angular resolution by the VST Photometric Ha Survey of the Galactic plane and bulge (VPHAS+). Anticipating the release of a uniform photometric calibration of the entire survey, we examine the properties of VPHAS+ ugriHa photometry of r < 19 mag. point sources in the third Galactic quadrant (longitudes 210^o to 260^o). We compare our interim calibration in gri with that of Pan-STARRS, the DECam Plane Survey (DECaPS-2) and Skymapper. We use the comparisons to identify small gri photometric offsets. Corrections to the Ha and u magnitude scales are determined via comparison with synthetic photometry. VPHAS+ and its northern counterpart, the INT Galactic Plane Survey (IGAPS), are shown to closely align, where they overlap across the celestial equator. Aided by Gaia Data Release 3, SIMBAD, and specialist catalogues, we present selections of: A stars; sub-luminous stars; intrinsically-red luminous stars; young stellar objects; emission-line and OB stars. Attention is drawn to stellar variability as a contaminant in selecting emission line objects via (r - Ha) excess. It is argued the (r - i, r - Ha) plane is the better choice for this selection than (g - i, r - Ha). Using A stars to map extinction, we trace the main run of dust obscuration, situated at mainly negative Galactic latitudes. Like the dust, OB and emission line stars are more frequent below the Galactic equator: at heliocentric distances of up to ~7 kpc, these stars' distribution fit in with the known warping of the Galactic plane. An overdensity of B stars, several degrees across and potentially in the Outer Arm, is found around (l,b) = (212.0, -0.6).
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All authors J. E. Drew, R. Greimel, J. Eislöffel, R. Raddi, N. J. Wright

Earth and Planetary Astrophysics

Rotational Light-curve Recovery and Predictions of the LSST Yield of Hildas

Alexander J. Fleming, Jacob A. Kurlander, Dmitrii E. Vavilov et al. (+4 more)

The Hilda population occupies the stable 3:2 mean-motion resonance of Jupiter and provides a window into solar system evolution, including collisional processes. The National Science Foundation and Department of Energy Vera C. Rubin Observatory will conduct the 10 yr Legacy Survey of Space and Time (LSST). We present a simulation of Rubin's discovery of Hildas with the Sorcha survey simulator and the recovery of their light curves. We constructed a synthetic Hilda population model that includes distributions of orbital properties, sizes, collisional families, and colors. We applied three distinct populations of sinusoidal light curves to this same orbit-size-color model: (1) a Gaussian kernel density estimate fit to rotational periods and amplitudes from the Lightcurve Database (LCDB), (2) a superfast rotator population, and (3) a superslow rotator population. Over the 10 yr simulated survey, we predict LSST will discover ~33,400 Hildas, a fivefold increase over the known population. Using a multiband Lomb-Scargle Periodogram via Astropy we confidently recover ~45.96% of Hildas in our LCDB-based population, higher than typical in observational searches. This suggests our light-curve population model may differ from the intrinsic population. We find strong biases in light-curve amplitude, with recovery efficiency dropping sharply below 0.1 magnitudes, while biases from rotational period are comparatively weak aside from cadence-related features such as LSST's ~36 minute revisit cadence. Our recovery efficiency is likely overestimated due to our assumption of constant sinusoidal light curves, which correspond to optimal pole orientations. These results are the first test of light-curve recovery from simulated LSST observations.
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All authors Alexander J. Fleming, Jacob A. Kurlander, Dmitrii E. Vavilov, David Vokrouhlicky, David Nesvorny, Pedro H. Bernardinelli, Mario Juric

High Energy Astrophysical Phenomena

XRISM Observations of Accretion Disk Corona in Cyg X-2

Misaki Mizumoto, Hiromitsu Takahashi, Ehud Behar et al. (+6 more)

We present the high-resolution X-ray spectrum of the Z-source Cygnus X-2, obtained with X-Ray Imaging and Spectroscopy Mission (XRISM). The observations have enabled a precise characterization of the Fe-K emission lines from the accretion disk corona (ADC) and a possible detection of an ultra-fast outflow (UFO). The ADC component has at least two distinct regions. The Fe-K emission lines are remarkably broad, with a velocity dispersion of $\sigma_v=2300^{+900}_{-700}$~km~s$^{-1}$. This can be larger than what was observed in previous Chandra observations ($1120\pm870$~km~s$^{-1}$) and recent XRISM observations of the similar Z-source GX 340+0 (360–800~km~s$^{-1}$). Furthermore, we marginally detect a blueshifted absorption feature, which we identify as either \ion{Fe}{26} or \ion{Fe}{25}, with outflow velocities of $-0.29c$ or $-0.26c$, respectively. The mass loss rate is $\dot{M}\sim10^{-8}M_\odot\,\mathrm{yr}^{-1}$. Our findings suggest that the ADC in Cyg X-2 has a kinematically active environment with a high degree of turbulence and kinetic energy.
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All authors Misaki Mizumoto, Hiromitsu Takahashi, Ehud Behar, Rozenn Boissay-Malaquin, Lia Corrales, Elisa Costantini, Maria Diaz-Trigo, Eric D. Miller, Jon M. Miller

Cosmology and Nongalactic Astrophysics

Constraints on Chiral-Quintom dark energy after DESI DR2 and impact on unifying dark energy with inflation

Andronikos Paliathanasis, Tommaso Mengoni, Genly Leon et al. (+1 more)

The recent data release DR2 from the Dark Energy Spectroscopic Instrument (DESI) has reinforced compelling evidence supporting the dynamical nature of dark energy. In this respect, we here explore a two-scalar field cosmological model, dubbed Chiral-Quintom paradigm, that allows for a unified description of early- and late-time cosmic accelerations, namely inflation and dark energy, respectively. Moreover, we show that it provides a mechanism to cross the phantom divide without instabilities. To do so, we first focus on scenarios where the scalar fields evolve under an exponential potential, leading to distinct cosmological behaviors, including tracking solutions and slow-roll or hyperbolic inflation. Afterwards, by considering a nonlinear potential and a mixing in the kinetic sector, we show that the model can also describe the matter-dominated era, offering a potential unification of the dark sector. Accordingly, we place bounds on this double-field paradigm by employing recent low-redshift observational data, including supernovae from the Pantheon+ and Union3.0 compilations, observational Hubble parameter measurements, and baryon acoustic oscillation data from the latest DESI release. By means of the Akaike information criterion, the standard $\Lambda$CDM scenario and the $w_0w_a$CDM model are thus compared with the Chiral-Quintom approach, showing that, in principle, multiple-field dynamics does not seem to be ruled out, ultimately providing a flexible framework for describing late-time dynamics.
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All authors Andronikos Paliathanasis, Tommaso Mengoni, Genly Leon, Orlando Luongo

High Energy Astrophysical Phenomena

Normal or transitional? The evolution and properties of two type Ia supernovae in the Virgo cluster

L. Izzo, C. Gall, N. Khetan et al. (+47 more)

Type Ia supernovae (SNe Ia) are among the most precise cosmological distance indicators used to study the expansion history of the Universe. The vast increase of SN Ia data due to large-scale astrophysical surveys has led to the discovery of a wide variety of SN Ia sub-classes, such as transitional and fast-declining SNe Ia. However, their distinct photometric and spectroscopic properties differentiate them from the population of normal SNe Ia such that their use as cosmological tools remains challenged. Here, we present a high-cadenced photometric and spectroscopic dataset of two SNe Ia, SNe 2020ue and 2020nlb, which were discovered in the nearby Virgo cluster of galaxies. Our study shows that SN 2020nlb is a normal SN Ia whose unusually red color is intrinsic, arising from a lower photospheric temperature rather than interstellar reddening, providing clear evidence that color diversity among normal SNe Ia can have a physical origin. In contrast, SN 2020ue has photometric properties, such as color evolution and light-curve decay rate, similar to those of transitional SNe, spectroscopically it is more aligned with normal SNe Ia. This is evident from spectroscopic indicators such as the pseudo-equivalent width of \ion{Si}{II} lines. Thus, such SNe Ia that are photometrically at the edge of the standard normal SNe Ia range may be missed in cosmological SNe Ia samples. Our results highlight that spectroscopic analysis of SNe Ia around peak brightness is crucial for identifying intrinsic color variations and constructing a more complete and physically homogeneous SN Ia sample for precision cosmology.
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All authors L. Izzo, C. Gall, N. Khetan, N. Earl, J. Hjorth, W. B. Hoogendam, Y. Q. Ni, A. Sedgewick, S. M. Ward, Y. Zenati, K. Auchettl, S. Bhattacharjee, S. Benetti, M. Branchesi, E. Cappellaro, A. Catapano, K. C. Chambers, D. A. Coulter, K. W. Davis, M. Della Valle, S. Dhawan, T. de Boer, G. Dimitriadis, R. J. Foley, M. Fulton, H. Gao, W. J. Hon, M. E. Huber, D. O. Jones, C. D. Kilpatrick, C. C. Lin, T. B. Lowe, E. A. Magnier, K. S. Mandel, R. Margutti, G. Narayan, P. Ochner, Y. C. Pan, A. Reguitti, C. Rojas-Bravo, M. Siebert, S. J. Smartt, K. W. Smith, S. Srivastav, J. J. Swift, K. Taggart, G. Terreran, S. Thorp, L. Tomasella, R. J. Wainscoat

Instrumentation and Methods for Astrophysics · Cross-listed from physics.flu-dyn

Large/small eddy simulations: A posteriori analysis in high Reynolds number isotropic turbulence

Chang Hsin Chen, Arnab Moitro and Alexei Y. Poludnenko

While direct numerical simulations (DNS) are the most accurate method for studying turbulence, their large computational cost restricts their use to idealized configurations and to Reynolds numbers well below those found in practical systems. A recently proposed method, Large/Small Eddy Simulation (L/SES), aims to overcome this limitation while still providing the solution fidelity comparable to that of DNS. L/SES represents a pair of coupled calculations: a lower-fidelity Large Eddy Simulation (LES), which captures the large-scale flow structure, and a high-fidelity Small-Eddy Simulation (SES) targeting a sub-region of interest of the LES, in which the small-scale dynamics is fully resolved. In this study, we demonstrate the accuracy and performance of L/SES in large Reynolds-number homogeneous isotropic turbulence (HIT) up to Taylor-scale Reynolds number approximately 600. Turbulence properties obtained with L/SES are shown to be in close agreement with the literature, both in terms of global characteristics, such as kinetic energy spectra and dissipative anomaly, as well as small-scale properties, such as higher-order moments of the velocity gradients up to the 10th order and probability density functions of the intermittent quantities. Also using simulations of HIT, we systematically investigate various method parameters and determine their optimal converged values. Finally, we discuss the computational cost of L/SES and demonstrate that it is approximately 3 orders of magnitude lower than for a traditional DNS at the highest Reynolds number considered here. This highlights the potential of L/SES as a discovery tool, which brings high-fidelity simulations of realistic flows into the realm of feasibility.
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High Energy Astrophysical Phenomena · Cross-listed from physics.ed-ph

Astro-Animation – How Artists and Scientists Envision the Universe

Laurence Arcadias, Robin H.D. Corbet and Emma Booth

For several years, students at an art college, working with NASA astronomers, have produced animations inspired by research on black holes, dark matter and more. They can be whimsical or poetic but still constrained by scientific rigour. The animations are used for scientific outreach and are freely available. Our program received a positive assessment through an evaluation we undertook. We are now planning a mobile STEAM exhibition to engage teenagers from underrepresented communities who may not typically consider STE(A)M for their studies. "Science anxiety" has been reported to be a significant barrier to learning. Mixing animation with astronomy can stimulate interest in STEAM, making science engaging in an unconventional way. One component would be activities where participants create artistic responses to astronomy. We undertook a workshop at a local city-run school, specialising in the arts for ages 14-17, to brainstorm the art/science activities. There we gave short scientific presentations leading to art activities: a giant colouring wall with projected celestial phenomena, a stop-motion station, and colouring images of comet 67P to produce an animation. Surveys before and after the activities showed positive responses. The hand of the artist has long been an important concept in animation (Crafton 1991). In a film entitled "The Movements of the Universe", this concept is adapted to the hands of scientists. Combining animation, filmed interviews at NASA (including a Nobel prize winner), and the scientists' hands, bring unexpected feelings of dream and humour to the audience. In this paper we explore three different viewpoints of these activities from a scientist, an animator, and an animation student.
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Earth and Planetary Astrophysics

Interstellar Ices as Carriers of Supernova Material to the Early Solar System

Martin Bizzarro, Martin Schiller, Jesper Holst et al. (+10 more)

Planetary materials show systematic variations in their nucleosynthetic isotope compositions that resonate with orbital distance. The origin of this pattern remains debated, limiting how these isotopic signatures can be used to trace the precursors of terrestrial planets. Here we test the hypothesis that interstellar ices carried supernova-produced nuclides by searching for a supernova nucleosynthetic fingerprint in aqueous alteration minerals from carbonaceous and non-carbonaceous chondrite meteorites. We focus on zirconium, a refractory element that includes the neutron-rich isotope $^{96}$Zr formed in core-collapse supernovae. Leaching experiments reveal extreme $^{96}$Zr enrichments in alteration minerals, showing that they incorporated supernova material hosted in interstellar ices. We show that the Solar System's zirconium isotope variability reflects mixing between these ices and an ice-free rocky component. Finally, the presence of supernova nuclides in a volatile carrier supports models where the Solar System's nucleosynthetic variability was imparted by thermal processing of material in the protoplanetary disk and during planetary accretion.
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All authors Martin Bizzarro, Martin Schiller, Jesper Holst, Laura Bouvier, Mirek Groen, Frédéric Moynier, Elishevah van Kooten, Maria Schönbächler, Troels Haugbølle, Darach Watson, Anders Johansen, James Connelly, Emil Bizzarro

Cosmology and Nongalactic Astrophysics

The SRG/eROSITA All-Sky Survey: A comprehensive X-ray analysis of the Hydra I galaxy cluster

Alpish Srivastava, Thomas H. Reiprich, Angie Veronica et al. (+4 more)

The Hydra I galaxy cluster (Abell 1060) is a nearby example of a low-temperature cluster that exhibits intermediate cool core and non-cool core properties. Our aims are to extend the characterization of the intracluster medium (ICM) properties at least until $R_{200}$ and study the correlation between the X-ray emission and non-thermal emission within $R=0.15$$R_{500}$, and optical/IR galaxy distribution beyond $R_{200}$. We used data from the first four SRG/eROSITA All-Sky Surveys and an archival Chandra observation to image the X-ray emission from Abell 1060. We also used multiwavelength data from TGSS (radio), 2MASS (IR), and NED (optical) to investigate the non-thermal emission, 2D galaxy distribution, and its redshift evolution, respectively. The surface brightness and spectral analyses are also extended until 3$R_{200}$ and $R_{200}$, respectively, following a detailed cosmic X-ray background (CXB) analysis. Our fully corrected eROSITA image showcases a relaxed ICM morphology within $R_{500}$. We detected two surface brightness discontinuities near the central galaxy NGC~3311 that spatially coincide with diffuse radio emission along the line of sight. Furthermore, we detected two soft X-ray excesses with high spatial correlation with the 2D optical galaxy distribution beyond $R_{200}$. In particular, the excess in the north has a significance of $3.9\sigma$ above the local CXB level. This suggests that Abell 1060's outskirts are actively accreting baryons. We also estimated the average ICM temperature and metallicity of $\langle k_\mathrm{B}T \rangle=2.51\substack{+0.21\\-0.21}\thinspace$ keV and $\langle Z\rangle=0.19\substack{+0.10\\-0.10}\thinspace Z_\odot$, respectively, from the 0.2-0.5$R_{500}$ annulus. Overall, the temperature profile is broadly consistent with the average temperature profiles from hydrodynamical simulation and Suzaku between 0.43$R_{500}$ and $R_{500}$.
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All authors Alpish Srivastava, Thomas H. Reiprich, Angie Veronica, Florian Pacaud, Jakob Dietl, Fiona Knies, Manami Sasaki

Solar and Stellar Astrophysics

Ubiquity of Methanol and its related Chemical Segregation in Orion Starless Cores: the ALMASOP Sample

Shih-Ying Hsu, Sheng-Yuan Liu, Xunchuan Liu et al. (+8 more)

Complex organic molecules (COMs) in starless cores provide critical insights into the early stages of star formation and prebiotic chemistry. We present a chemical survey of 16 starless cores (including five prestellar cores) in the Orion A and B molecular clouds, targeting CH3OH, N2H+, CCS, and c-C3HD, using the Atacama Compact Array (ACA) and the Yebes 40-m telescope. CH3OH was detected toward all targets, confirming its ubiquity in starless cores, consistent with previous surveys in Taurus and Perseus. ACA imaging shows that CH3OH, CCS, and c-C3HD generally trace the outer layers of the dense cores outlined by N2H+, each exhibiting distinct spatial distributions. Meanwhile, Comparison with Yebes data reveals an extended, flattened CH3OH component. CCS and c-C3HD tend to be detected or non-detected together across cores, while cores near dust-rich regions on a large scale often lack both, suggesting environmental influences linked to the interstellar radiation field. Within individual cores, CCS typically resides in an outer layer relative to c-C3HD. Our findings underscore the importance of high-resolution studies for understanding the origins and spatial differentiation of COMs and carbon-chain molecules in cold, quiescent environments.
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All authors Shih-Ying Hsu, Sheng-Yuan Liu, Xunchuan Liu, Pak Shing Li, Ken'ichi Tatematsu, Naomi Hirano, Sheng-Jun Lin, Kee-Tae Kim, Shanghuo Li, Tie Liu, Dipen Sahu

Instrumentation and Methods for Astrophysics

Intercepting Interstellar Objects

Colin Snodgrass, Marina Galand, Arnaud Beth et al. (+3 more)

We describe how the ESA Comet Interceptor mission, which is due to launch in 2028/29 to a yet-to-be-discovered target, can provide a conceptual basis for a future mission to visit an Interstellar Object. Comet Interceptor will wait in space until a suitable long period comet is discovered, allowing rapid response to perform a fast flyby of an object that will be in the inner Solar System for only a few years; an enhanced version of this concept could realistically provide the first in situ investigation of a visitor from another star system.
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All authors Colin Snodgrass, Marina Galand, Arnaud Beth, Charlotte Goetz, Abbie Donaldson, Cyrielle Opitom

High Energy Astrophysical Phenomena

Excitation of molecular hydrogen by cosmic-ray protons

Marco Padovani, Daniele Galli, Corey T. Plowman et al. (+4 more)

Low-energy cosmic rays ($E\lesssim 1$ GeV) are responsible for the ionisation and heating of molecular clouds. While the role of supra-thermal electrons produced in the ionisation process in inducing excitation of the ambient gas (mostly molecular hydrogen) has been studied in detail, the role of primary cosmic-ray nuclei (protons and heavier nuclei) has been generally neglected. Here, we introduce, for the first time, cross sections for proton impact on H$_2$, calculated using the semi-classical implementation of the molecular convergent close-coupling method. Our findings show that proton-induced H$_2$ excitation is comparable in magnitude to that caused by electrons. We discuss the possible implications on the estimate of the cosmic-ray ionisation rate from observations in the near-infrared domain and on the cosmic-ray-induced H$_2$ ultraviolet luminescence. We also derive a new approximated analytical parameterisation of the spectrum of secondary electrons that can be easily incorporated in numerical codes.
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All authors Marco Padovani, Daniele Galli, Corey T. Plowman, Liam H. Scarlett, Mark C. Zammit, Igor Bray, Dmitry V. Fursa

Earth and Planetary Astrophysics

Deep Neural Network-Based High-Precision Identification of Weak Stability Boundary Structures

Shuyue Fu, Ziqi Xu, Di Wu et al. (+1 more)

Weak stability boundary structures have been widely applied to the analysis on ballistic capture and the construction of low-energy transfers. The first step of this application is to compute/identify weak stability boundary structures. Conventional numerical and analytical methods cannot simultaneously achieve computational efficiency and identification precision. In this paper, we propose an efficient and precise method to identify weak stability boundary structures based on deep neural network. The geometric and dynamical properties of weak stability boundary structures are firstly analyzed, which provides further insights into the training of the deep neural network models. Then, the optimal hyperparameter combinations are determined by examining the identification precision of the trained deep neural network models. The performance of the models with the optimal hyperparameter combinations is further validated using the representative test datasets, achieving the precision of 97.26-99.91%. The trained models are also applied to constructing weak stability boundary structures.
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All authors Shuyue Fu, Ziqi Xu, Di Wu, Shengping Gong

Solar and Stellar Astrophysics

Interferometry of Massive Stars: Multiplicity, Magnetism, and Stellar Winds

H. Sana E. Bordier, K.Deshmukh, A.J. Frost et al. (+7 more)

After decades of efforts, optical long-baseline interferometry has become a mainstream observational technique in terms of operation robustness and user friendliness. Interferometry has opened a new observational window, enabling (sub)au-scale resolution of massive stars and direct measurements of orbital parameters, wind structures, and magnetic phenomena. This paper reviews recent advances in interferometric studies of massive stars, focusing on multiplicity, magnetism, and stellar winds.
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All authors H. Sana E. Bordier, K.Deshmukh, A.J. Frost, A. Keskar, C. Lanthermann, R. R. Lefever, L. Mahy, A.A.C. Sander, T. Shenar, F. Tramper

Instrumentation and Methods for Astrophysics

Analysis of Angular-Differential Post-Processing Algorithms for Exoplanet Direct Detection with a Photonic Lantern Nuller

Suvinay Goyal, Yinzi Xin, Nemanja Jovanovic et al. (+2 more)

Exoplanet research is essential for understanding planetary formation and the potential for life beyond our solar system. The direct imaging method captures exoplanet light while minimizing light from the host star. This is conventionally achieved with a coronagraph, which allows detailed characterization of planetary atmospheres and features. The Photonic Lantern Nuller (PLN) is an innovative instrument designed for the direct detection of closely orbiting exoplanets within the inner working angle of standard coronagraphs. Unlike traditional coronagraphs, where the planet's signal is usually rotationally invariant, with the same point-spread-function at different position angles, and which also overlaps minimally with the residual stellar signal, data from a PLN consist of a one-dimensional collection of points that do not have rotational invariance and overlap significantly with the residual starlight arising from wavefront errors. Exploiting angular diversity to subtract these stellar residuals with the PLN thus requires adapting the Angular Differential Imaging (ADI) technique for use with non-rotationally invariant planet signals at close separations, where strong self-subtraction effects occur. We reformulate ADI using principal component analysis to develop a method to extract spatial parameters of exoplanets from simulated one-dimensional PLN data. We test two variations of ADI on simulated data and show that injecting an antiplanet signal before stellar estimation helps localize the planet due to self-subtraction at lower separations.
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All authors Suvinay Goyal, Yinzi Xin, Nemanja Jovanovic, Dimitri Mawet, Michael P. Fitzgerald

Cosmology and Nongalactic Astrophysics

Wavelet-Scattering Signatures of Fuzzy Dark Matter in Simulated 21 cm Brightness-Temperature Maps

Hayato Shimabukuro, Shihang Liu and Bohua Li

We study the effect of fuzzy dark matter (FDM) on the multiscale morphology of simulated redshifted 21\,cm maps during Cosmic Dawn and the Epoch of Reionization. Using FDM-modified 21cmFAST light cones, we apply the two-dimensional wavelet scattering transform (WST) to matched 2\,MHz map products. The first-order coefficients $S_1(j)$ summarize wavelet-band amplitudes, while the normalized second-order ratio $R=S_2/S_1(j_1)$ measures ordered cross-scale modulation. FDM shifts and reshapes both summaries through delayed halo and source formation. We compare a two-dimensional power spectrum (PS), WST, and their combination on the same transferred and noisy maps. In this controlled local Fisher analysis, PS+WST reduces the marginalized errors on the FDM mass, effective X-ray emissivity normalization, and ionizing efficiency by approximately a factor of 1.8 relative to the matched two-dimensional PS baseline, although the dominant mass-heating degeneracy remains. An idealized three-wedge test shows that $R$ is less reshaped at the coefficient level than $S_1$. The covariance includes thermal noise conditional on one fiducial light cone but not cosmic variance or foreground residuals; the results are therefore relative information comparisons, not survey forecasts or a demonstration of superiority over a full three-dimensional PS analysis.
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Earth and Planetary Astrophysics

Physicochemical Controls on the Compositions of the Earth and Planets

Paolo A. Sossi, Remco C. Hin, Thorsten Kleine et al. (+2 more)

Despite the fact that the terrestrial planets formed from the protoplanetary disk, their compositions show marked departures from that of solar nebula condensates. Metallic cores fix oxygen fugacities ($f$O$_2$s) of the planets to 5 (Mercury) to 1 log units below the iron-wüstite (IW) buffer, orders of magnitude higher than the nebular gas. Their oxidised character is coupled with a lack of volatile elements with respect to the solar nebula. Condensates from a solar gas at different temperatures ($T_0$) have Fe/O (by mass) of 0.93 ($T_0$ = 1250 K) to 0.81 ($T_0$ = 400 K), far lower than that of Earth (1.06). Because the reaction Fe(s) + H2O(g) = FeO(s) + H2(g) proceeds <600 K, temperatures at which most moderately volatile elements (MVEs) have condensed, oxidised planets should be volatile-rich, and vice-versa. That this is not observed suggests that planets did not accrete from equilibrium nebular condensates and/or underwent additional volatile depletion/$f$O$_2$ changes. Indeed, MVEs in small telluric bodies (Moon, Vesta) indicate near equilibrium evaporation/condensation at IW-1 and 1400-1800 K. Volatile-depleted elemental yet near-chondritic isotopes of larger telluric bodies (Earth, Mars) reflect mixing of bodies of variable volatile depletion, overprinted by volatile-undepleted material. From the Cr- and Ti isotopes in the BSE, such undepleted matter has been proposed to be CI chondrites. 6% CI added late to an enstatite chondrite-like proto-Earth would match the Earth. However, because Earth is an end-member in isotopic anomalies of heavier elements, no combination of existing meteorites alone can account for its chemical- and isotopic composition. Instead, the Earth is made partially or essentially entirely from an NC-like missing component. If so, the oxidised-, yet volatile-poor nature of inner solar system bodies, including Earth and Mars, is intrinsic to the NC reservoir.
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All authors Paolo A. Sossi, Remco C. Hin, Thorsten Kleine, Alessandro Morbidelli, Francis Nimmo