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Keyword list: ['star formation', 'star-forming', 'molecular cloud', 'interstellar medium', 'cloud', 'clump', 'core', 'filament', 'atomic gas', 'N-PDF']

Excluded: ['galaxies', 'galaxy cluster', ' AGN ', 'standard candle', 'X-ray binar', 'solar corona']

Today: 18papers

Optical Spectroscopy Reveals Hidden Neutron-capture Elemental Abundance Differences among APOGEE-identified Chemical Doppelgängers

• Authors: Catherine Manea, Melissa Ness, Keith Hawkins, Greg Zeimann, David W. Hogg, Carrie Filion, Emily J. Griffith, Kathryn Johnston, Andrew Casey, Zoe Hackshaw, Tyler Nelson, Micah Marks

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2508.16717

• Pdf link: https://arxiv.org/pdf/2508.16717

• Abstract Grouping stars by chemical similarity has the potential to reveal the Milky Way's evolutionary history. The APOGEE stellar spectroscopic survey has the resolution and sensitivity for this task. However, APOGEE lacks access to strong lines of neutron-capture elements ($Z > 28$) which have nucleosynthetic origins that are distinct from those of the lighter elements. We assess whether APOGEE abundances are sufficient for selecting chemically similar disk stars by identifying 25 pairs of chemical ``doppelgangers'' in APOGEE DR17 and following them up with the Tull spectrograph, an optical, $R \sim 60{,}000$ echelle on the McDonald Observatory 2.7-m telescope. Line-by-line differential analyses of pairs' optical spectra reveals neutron-capture (Y, Zr, Ba, La, Ce, Nd, and Eu) elemental abundance differences of $\Delta$[X/Fe] $\rm \sim 0.020 \pm 0.015$ to $0.380 \pm 0.15$ dex (4--140%), and up to 0.05 dex (12%) on average, a factor of 1--2 times higher than intra-cluster pairs. This is despite the pairs sharing nearly identical APOGEE-reported abundances and [C/N] ratios, a tracer of giant-star age. This work illustrates that even when APOGEE abundances derived from SNR $> 300$ spectra are available, optically-measured neutron-capture element abundances contain critical information about composition similarity. These results hold implications for the chemical dimensionality of the disk, mixing within the interstellar medium, and chemical tagging with the neutron-capture elements.

Magnetic interaction analysis of multiple interplanetary coronal mass ejections leading to a historic geomagnetic storm in May 2024

• Authors: Sanchita Pal, Cecilia Mac Cormack, Emilia K. J. Kilpua, Yogesh, Lan K. Jian, Teresa Nieves-Chinchilla

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

• Arxiv link: https://arxiv.org/abs/2508.16780

• Pdf link: https://arxiv.org/pdf/2508.16780

• Abstract Interplanetary coronal mass ejections (ICMEs), the large-scale eruptive phenomena capable of shedding a huge amount of solar magnetic helicity and energy are potential in driving strong geomagnetic storms. They complexly evolve while preceded and followed by other large-scale structures e.g. ICMEs. Magnetic interaction among multiple ICMEs may result intense and long-lived geomagnetic storms. Our aim is to understand the reason of substantial changes in the geoeffectivity of two meso-scale separated counterparts of a complex solar wind structure through investigating their magnetic content e.g. helicity, energy and magnetic interaction among multiple ICMEs. We utilized the insitu observations of solar wind from Wind and Solar Terrestrial Relations Observatory-A (STA) spacecraft during the strongest geomagnetic storm period in past two decades on May 10-11, 2024 and heliospheric imagers onboard STA. Our investigation confirms complex interactions among five ICMEs resulting in distinct counterparts within a coalescing large-scale structure. These counterparts possess substantially different magnetic contents. We conclude that the complex counterpart resulted from the interaction among common-origin ICMEs observed by STA, favorably orientated for magnetic reconnection, had 1.6 and 2.8 times higher total magnetic energy and helicity, respectively, than the counterpart containing a left-handed filament-origin ICME observed by Wind. The left-handed ICME non-favorably oriented for magnetic reconnection with the surrounding right-handed, common-origin ICMEs. Therefore, two medium-separated counterparts despite belonging to a common solar wind structure, were potential to lead different geoeffectivity. This ultimately challenges space weather predictions based on early observations.

The HD 60779 Planetary System: A Transiting Sub-Neptune on a 30-day Orbit and a More Massive Outer World

• Authors: Victoria DiTomasso, David Charbonneau, Andrew Vanderburg, Mercedes López-Morales, Shreyas Vissapragada, Annelies Mortier, Thomas G. Wilson, Elyse Incha, Andrew Collier Cameron, Luca Malavolta, Lars A. Buchhave, David W. Latham, Matteo Pinamonti, Stephanie Striegel, Michael Fausnaugh, Luke Bouma, Ben Falk, Robert Aloisi, Xavier Dumusque, A. Anna John, Ben S. Lakeland, A. F. Martínez Fiorenzano, Luca Naponiello, Belinda Nicholson, Emily K. Pass, Francesco Alfonso Pepe, Federica Rescigno, Alessandro Sozzetti, Daisy A. Turner, Saul A. Rappaport, Mark Omohundro, Brian P. Powell, Robert Gagliano, Thomas L. Jacobs, Veselin B. Kostov, Martti H. Kristiansen, Daryll M. LaCourse, Allan R. Schmitt, Hans Martin Schwengeler, Ivan A. Terentev

• Subjects: Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

• Arxiv link: https://arxiv.org/abs/2508.16805

• Pdf link: https://arxiv.org/pdf/2508.16805

• Abstract We present the discovery of the planetary system orbiting the bright (V = 7.2), nearby (35 pc), Sun-like star HD 60779, which has a mass of 1.050 +/- 0.044 solar masses and a radius of 1.129 +/- 0.013 solar radii. We report two TESS transits and a subsequent CHEOPS transit of HD 60779 b, a sub-Neptune with a radius of 3.250 (+0.100 / -0.098) Earth radii on a 29.986175 (+0.000030 / -0.000033) day orbit. Additionally, 286 HARPS-N radial velocity measurements reveal the mass of planet b (14.7 +1.1 / -1.0 Earth masses) and the presence of an outer planet, HD 60779 c, with an orbital period of 104.25 (+0.30 / -0.29) days and a minimum mass (m sin i) of 27.7 +/- 1.6 Earth masses. Both planets' orbits are consistent with being circular, suggesting that they have a dynamically quiet history. The data are not sufficient to determine whether planet c transits. HD 60779's uniquely high systemic radial velocity (129.75 +/- 0.12 km/s) allows its Lyman-alpha emission to avoid absorption by the interstellar medium, making it a prime candidate for probing atmospheric escape from HD 60779 b. HD 60779 is also the third-brightest host of a sub-Neptune with orbital period greater than 25 days and with both mass and radius measured, distinguishing it in terms of accessibility to spectroscopic characterization.

Modeling Multiphase Galactic Outflows: A Multifluid Moving Mesh Approach

• Authors: Francesco Bollati, Rainer Weinberger

• Subjects: Subjects: Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2508.16971

• Pdf link: https://arxiv.org/pdf/2508.16971

• Abstract Outflows are a key part of the galactic gas cycle and crucial in shaping the star formation activity in their host galaxy. Yet, in simulations of galaxy evolution, modeling these outflows in their multi-phase nature and over the relevant timescales is an unsolved problem. We present a subgrid model for simulating multiphase galactic outflows in efficient, comparatively low-resolution simulations, designed for application in future cosmological simulations. The cold phase (T = 10000 K) is treated as pressureless, and its interaction with the hot phase is captured through source terms representing drag and mixing. These terms are obtained using analytic drag and mixing terms for single clouds and convolving them with a cloud mass distribution consistent with high-resolution simulations. Applied to a setup resembling the starburst galaxy M82, the model reproduces the velocity, density, and mass outflow rates of high-resolution simulations that resolve individual cold clouds. Cold outflows emerge naturally from interactions between the hot wind and cold interstellar clouds, with drag and mixing both contributing to the acceleration. Varying the mixing strength strongly affects outflow properties: stronger mixing enhances mass transfer from hot to cold gas, reduces the hot phase velocity, and accelerates the cold phase, while also influencing the origin and composition of the cold outflow. Weak mixing produces cold gas mostly from preexisting interstellar clouds, whereas stronger mixing leads to substantial cold gas formation from the hot phase. This framework enables efficient simulations of multiphase galactic outflows while retaining key multi-component features of the outflow dynamics.

The Kinematical Behavior of Solar Eruptive Filaments Affected by the Poloidal Magnetic Field

• Authors: Ye Qiu, Yang Guo, Mingde Ding, Chuan Li, Linggao Kong, Zhen Li

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2508.17039

• Pdf link: https://arxiv.org/pdf/2508.17039

• Abstract Kinematics of solar eruptive filaments is one of the important diagnostic parameters for predicting whether solar eruptions would induce geomagnetic storms. Particularly, some geomagnetic storms might be induced by solar filament eruptions originating from unexpected surface source regions because of non-radial ejection. The non-radial ejection of filaments has received widespread attention but remains inconclusive. We select two eruptive filaments, both of which are supported by flux ropes, as indicated by the hot channel structures seen in the 94 Å images and the hook-shaped brightenings where the filament material falls back. We measure the three-dimensional ejection trajectory of the eruptive filaments by integrating the simultaneous observations from SDO and STEREO. Furthermore, we calculate the distribution of the poloidal field along the ejection path and compare it to the ejection acceleration. It is revealed that the reinforcement of the poloidal magnetic field may lead to the suppression of the acceleration, with the acceleration resuming its increase only when the poloidal field diminishes to a certain level. Additionally, we compute the spatial distribution of the poloidal field in various directions and find that the poloidal magnetic field above the filaments is asymmetric. For both investigated events, the filaments appear to eject towards the side where the poloidal magnetic field is weaker, indicating that the eruptive filaments tend to propagate along the side with weaker strapping force. This may provide a new explanation for the inclined ejection of filaments.

On the Spatial Distribution of Luminous Blue Variables, B[e] Supergiants, and Wolf-Rayet stars in the Large Magellanic Cloud

• Authors: John C. Martin, Roberta M. Humphreys, Kris Davidson

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2508.17114

• Pdf link: https://arxiv.org/pdf/2508.17114

• Abstract We examine the spatial distributions of LBV's, B[e] supergiants, and W-R stars in the LMC, to clarify their relative ages, evolutionary states, and relationships. This survey employs a reference catalog that was not available for previous work, comprising more than 3900 of the LMC's most luminous stars. Our analysis shows that LBV's, B[e] supergiants, and WR's have spatial distributions like normal stars with the same spectral types and luminosities. Most LBV's are not isolated, nor do they require binary or multiple status to explain their spatial relationship to other populations. There are two likely exceptions: one lower-luminosity LBV and one LBV candidate are relatively isolated and may have velocities that require additional acceleration. The B[e] supergiants are spatially and kinematically more dispersed than LBV's, suggesting that they belong to an older population. The most luminous early-type WN's are most closely associated with the evolved late O-type supergiants. The high luminosity late WN's, however, are highly concentrated in the 30 Dor region which biases the analysis. The less luminous WN's and WC's are associated with a mix of evolved late B, A-type, and yellow supergiants which may be in a post-red-supergiant phase. Spatial distributions of the less luminous WN, WC, and WN3/O3 stars reinforce proposed evolutionary links among those subtypes. Our analysis also demonstrates the importance of using a comprehensive census, with reference populations clearly defined by spectral type and luminosity, and how small number statistics, especially combined with spatial clustering, can invalidate some commonly-cited statistical tests.

Discovery of the Second Y+Y Dwarf Binary System: CWISEP J193518.59-154620.3

• Authors: Matthew De Furio, Jacqueline Kelly Faherty, Daniella C. Bardalez Gagliuffi, Jonathan Gagné, Eileen C. Gonzales, Rocio Kiman, Marc Kuchner, Federico Marocco, Sherelyn Alejandro Merchan, Melanie Rowland, Adam C. Schneider, Genaro Suárez, Johanna M. Vos

• Subjects: Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2508.17176

• Pdf link: https://arxiv.org/pdf/2508.17176

• Abstract We present the discovery of a companion to the Y-dwarf, CWISEP J193518.59-154620.3, the second Y-Y dwarf binary detected to date. Y-dwarfs are the coldest known free-floating objects ($<$ 500 K) and on average represent the lowest mass objects directly formed through turbulent fragmentation of a molecular cloud. Studying their multiplicity allows us to place strong constraints on the ability to form multiple systems of planetary masses and approaching the opacity limit of fragmentation. Due to their physical properties, Y-dwarfs also serve as analogs to gas giant planets. CWISEP J193518.59-154620.3 has been shown to have a unique methane emission feature in its near infrared spectrum at 3.326 $\mu$m, potentially indicative of auroral processes without a clear origin. CWISEP J193518.59-154620.3 was observed with JWST's MIRI in the F1000W, F1280W, and F1800W filters. We applied a point-spread function (PSF) fitting algorithm using empirically derived PSF models and resolve a companion in the F1000W and F1280W filters separated by 172 milli-arcseconds, 2.48 au assuming the distance of 14.43 pc. Using the ATMO2020 evolutionary models, we estimate a mass of 12-39 $M_{\rm Jup}$ for the primary and 7-24 $M_{\rm Jup}$ for the companion assuming an age of 1-10 Gyr for a mass ratio of 0.55-0.62, resulting in an estimated period of 16-28 years. It is unknown which component of this binary exhibits the methane emission feature. We also resolve known companions WISE J014656.66+423410.0B and WISE J171104.60+350036.8B using MIRI data and present their F1000W and F1280W photometry.

Gravitational Instability and Fragmentation in Collapsar Disks Supports the Formation of Sub-Solar Neutron Stars

• Authors: Yi-Xian Chen, Brian D. Metzger

• Subjects: Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

• Arxiv link: https://arxiv.org/abs/2508.17183

• Pdf link: https://arxiv.org/pdf/2508.17183

• Abstract We perform three-dimensional shearing-box hydrodynamical simulations to explore the outcome of gravitational instability in the outer regions of neutrino-cooled disks such as those formed from the collapse of rotating massive stars ("collapsars''). We employ a physical equation of state, optically-thin neutrino cooling, and assume an electron fraction set by the balance of electron/positron pair-capture reactions. Disks in a marginally stable initial state (Toomre parameter Q~ 1) undergo runaway cooling and fragmentation when the dimensionless cooling timescale obeys tau_cool = t_cool*Omega < 10, where Omega is the orbital frequency; these conditions correspond to accretion rates > Msun/s on the upper end of those achieved by collapsar progenitor stars. Fragmentation leads to the formation of neutron-rich clumps (electron fraction Ye ~ 0.1) spanning a range of masses ~0.01-1 Msun around the local Jeans value. Most clumps exceed the local Chandrasekhar mass M_Ch ~ Ye^2 and hence will continue to collapse to nuclear densities, forming neutron stars (NS) with sub-solar masses otherwise challenging to create through ordinary stellar core-collapse. Even cool disks dominated by alpha-particles (Ye ~ 0.5) can fragment and collapse into neutron-rich clumps capable of forming sub-solar NSs. Although our simulations cannot follow this process directly, if the disk-formed NSs subsequently pair into binaries, the gravitational wave chirps from their rapid mergers are potentially detectable by ground based observatories. The temporal coincidence of such a hierarchical NS merger chain with the collapsar gamma-ray burst and supernova would offer a uniquely spectacular multi-messenger "symphony''.

Rotational Effects on Neutrino Emission in Core-collapse Supernovae

• Authors: Michael A. Pajkos, Siddharth Boyeneni, Oliver Eggenberger Andersen

• Subjects: Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

• Arxiv link: https://arxiv.org/abs/2508.17633

• Pdf link: https://arxiv.org/pdf/2508.17633

• Abstract All stars rotate. While magnetic braking slows massive stars, the effect a stellar companion has on stellar rotation is still being explored. To prepare for future observations from rotating core-collapse supernovae (CCSNe), we analyze a set of 30 2D neutrino radiation-hydrodynamic CCSN simulations for a variety of compactness values, rotation rates, and equations of state. We systematically explore how rotation lowers expected neutrino counts and energies for a realistic detector, while accounting for adiabatic Mikheyev-Smirnov-Wolfenstein matter effects. We quantify the effect of viewing angle for neutrino emission for multiple rotation rates. Using 'multimessenger synthesis', we develop a technique that correlates multimessengers to constrain the neutrino mass ordering for a future supernova event. Likewise, we develop a method to constrain the distance to a rotating or nonrotating CCSN, regardless of explosion outcome.

Core-mantle partitioning and the bulk Earth abundances of hydrogen and carbon: Implications for their origins

• Authors: Yutaro Tsutsumi (1), Naoya Sakamoto (2), Kei Hirose (1 and 3), Shuhei Mita (1), Shunpei Yokoo (1), Han Hsu (4), Hisayoshi Yurimoto (2 and 5) ((1) Department of Earth and Planetary Science, The University of Tokyo, Bunkyo, Tokyo, Japan (2) Institute for Integrated Innovations, Hokkaido University, Sapporo, Hokkaido, Japan (3) Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo, Japan (4) Department of Physics, National Central University, Taoyuan City, Taiwan (5) Department of Natural History Sciences, Hokkaido University, Sapporo, Hokkaido, Japan)

• Subjects: Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Materials Science (cond-mat.mtrl-sci)

• Arxiv link: https://arxiv.org/abs/2508.17740

• Pdf link: https://arxiv.org/pdf/2508.17740

• Abstract We determined the metal/silicate partition coefficients of hydrogen and carbon, DH and DC, simultaneously under typical conditions of Earth's core formation. Experiments demonstrate that both DH and DC diminish in the presence of carbon and hydrogen, respectively, indicating their strong interactions in liquid metal. With these partitioning data, we investigated the core and bulk Earth abundances of hydrogen and carbon based on core formation scenarios that are compatible with the bulk silicate Earth composition and the mass fraction and density deficit of the core. The results of the single-stage core formation modelling are markedly different from those using DH and DC individually determined in earlier experiments, indicating that the Earth building blocks do not match enstatite chondrites in water abundance and require contributions by carbonaceous chondrites. The multi-stage core formation models combined with an Earth accretion scenario accounting for isotopic composition show 0.18-0.49 wt% H and 0.19-1.37 wt% C in the core, leading to 0.53-1.40 wt% H2O (present as H in the core) and 0.07-0.44 wt% C in the bulk Earth. Our modelling also demonstrates that up to 53% and 72% of Earth's water (hydrogen) and carbon, respectively, could have been derived from non-carbonaceous chondritic materials.

Equilibrium Simplified Chemistries for H2O and CO in three-phase astrochemical models

• Authors: Jonathan Rawlings, Eric Keto, Paola Caselli

• Subjects: Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2508.17747

• Pdf link: https://arxiv.org/pdf/2508.17747

• Abstract Astrochemical models can be greatly simplified, with obvious computational advantages, if the reaction networks for key species can be reduced to a bare minimum. In addition, if chemical equilibrium holds, then simple analytical solutions can be formulated. These have particular advantages in the application to complex models evolving over multi-point spatial grids. In this study, the equilibrium solutions to highly simplified chemical networks for CO and H2O have been re-assessed with particular attention to the formulation of the ice desorption rates in the context of 'three-phase' gas-grain astrochemical models. The analytical solutions have also been updated to account for the chemically inert reservoir of molecules below the surface ice layers, and to include the effects of reactive desorption. We find that a very close match is obtained to the results from detailed three-phase models of the time-dependent astrochemistry, and the abundances are typically accurate to within a factor of two over the entire range of densities and extinction that are applicable to dense clouds and young star-forming regions. In addition, these solutions give accurate results over most of the range of conditions even for systems undergoing rapid dynamical evolution. Although there are some caveats of applicability, we therefore recommend that these solutions be used in models of cold molecular environments where the rapid calculation of the abundances of CO, H2O and atomic coolants is helpful.

Sun-as-a-star Analysis of the Solar Eruption Source Region Using Ha Spectroscopic Observations of CHASE

• Authors: Xiaofeng Liu, Yijun Hou, Ying Li, Ye Qiu, Ting Li, Yingjie Cai, Shihao Rao, Junyi Zhang, Chuan Li

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2508.17762

• Pdf link: https://arxiv.org/pdf/2508.17762

• Abstract Sun-as-a-star analyses serve as a bridge for comparative studies on solar and stellar activities. To investigate the typical Sun-as-a-star Ha temporal spectral characteristics in solar eruption source regions, we analyzed five different types of solar eruptions, using spectroscopic data from the Chinese Ha Solar Explorer (CHASE). Because the spatially-integral Ha spectrum of source region is mainly contributed by emission from heated plasma in flare ribbons and absorption from cold plasma in evolving filaments, we separately analyze the sub-regions of the source region dominated by different dynamical processes. It is revealed that filament eruptions show emission near Ha line center, accompanied by blueshifted/redshifted absorption, while flare ribbons show Ha line center emission with red asymmetry and line broadening. Moreover, a special spectral signature likely associated with coronal mass ejections (CMEs) is identified: prominent blueshifted absorption without a clear deceleration phase, along with redshifted absorption, which can be used as a probe when searching stellar CMEs. Furthermore, in the X9.0 flare (SOL2024-10-03T12:18) accompanied by a violent CME, the expected blueshifted signal is not visible in the spatially-integral Ha spectra. This suggests that filament-lifting signals associated with CMEs in the source region can be obscured by the simultaneous dominant flare-ribbon emission within the integration region, which may explain the relatively small number of confirmed stellar CMEs observed in Ha. We also find that comparison between the Ha and UV spectral observations can effectively reveal the velocity evolution of erupting filaments and potential existence of associated CMEs.

The Impact of Axion-Like Particles on Late Stellar Evolution From Intermediate-Mass Stars to core-collapse Supernova Progenitors

• Authors: Inmacolata Domínguez, Oscar Straniero, Luciano Piersanti, Maurizio Giannotti, Alessandro Mirizzi

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

• Arxiv link: https://arxiv.org/abs/2508.17779

• Pdf link: https://arxiv.org/pdf/2508.17779

• Abstract Context. Stars with masses ranging from 3 to 11 M_\odot exhibit multiple evolutionary paths. Less massive stars in this range conclude their evolution as carbon-oxygen (CO) white dwarfs. However, those that achieve carbon ignition before the pressure by degenerate electron halts the core contraction may either form massive CONe/ONe white dwarfs, or undergo an electron-capture supernova, or photo-disintegrate neon and proceed with further thermonuclear burning, ultimately leading to the formation of a gravitationally unstable iron core. Aims. An evaluation of the impact of the energy loss caused by the production of axion-like-particles (ALPs) on evolution and final destiny of these stars is the main objective of this paper. Methods. We compute various sets of stellar models, all with solar initial composition, varying the strengths of the ALP coupling with photons and electrons. Results. As a consequence of an ALP thermal production, the critical masses for off-center C and Ne ignitions are both shifted upward. When the current bounds for the ALP coupling strengths are assumed, the maximum mass for CO WD progenitors is about 1.1 M_\odot heavier than that obtained without the ALP energy loss, while the minimum mass for a core collapse supernova (CCSN) progenitor is 0.7 M_\odot higher. Conclusions. Current constraints from observed Type II-P supernova light curves and pre-explosive luminosity do not exclude an ALP production within the current bounds. However, the maximum age of CCSN progenitors, as deduced from the star formation rate of the parent stellar population, would require a smaller minimum mass. This discrepancy can be explained by assuming a moderate extra mixing (as due to core overshooting or rotational induced mixing) above the fully convective core that develops during the main sequence.

Investigating Optical and Ring-Down Gravitational Wave Properties of a Rotating Black Hole in a Dehnen Galactic Dark Matter Halo

• Authors: Mrinnoy M. Gohain, Dhruba Jyoti Gogoi, Kalyan Bhuyan, Prabwal Phukon

• Subjects: Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

• Arxiv link: https://arxiv.org/abs/2508.18053

• Pdf link: https://arxiv.org/pdf/2508.18053

• Abstract We present a comprehensive study of the optical and dynamical properties of a rotating black hole immersed in a Dehnen-type $(1,4,0)$ galactic dark matter halo, modeled by a double power-law density profile commonly used to describe realistic galactic cores. By extending our previous Schwarzschild-Dehnen solution using a modified Newman-Janis algorithm, we construct a Kerr-like axisymmetric spacetime that smoothly incorporates both black hole rotation and the influence of the surrounding dark matter halo. We systematically investigate the effects of the halo parameters-the central density and halo radius-on horizon structure, the shape and extent of the ergoregion, and the null geodesics associated with black hole shadows. Our results show that the presence of a dense or extended halo expands the event horizon and ergoregion, and significantly alters the size and distortion of the black hole shadow. Furthermore, by applying the WKB approximation to scalar field perturbations, we compute the quasinormal mode (QNM) spectra and demonstrate that the frequencies and damping times of ringdown signals are highly sensitive to the halo profile. These results open promising avenues for probing the dark matter environment of astrophysical black holes through black hole imaging and gravitational wave observations.

Timing Mass of the Local Group

• Authors: Louis E. Strigari

• Subjects: Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)

• Arxiv link: https://arxiv.org/abs/2508.18061

• Pdf link: https://arxiv.org/pdf/2508.18061

• Abstract The classic model of the Local Group (LG) is that of two dominant constituents, the Milky Way and M31, first separating and then detaching from the Hubble flow, leading to a nearly radial approaching orbit. This simple model has been confronted by new measurements of the 3D M31 kinematics, by cosmological simulations, and by theoretical understanding of the impact of massive substructures such as the Large Magellanic Cloud. This article explores the consequences of new observations and theory on the determination of the mass and dynamics of the LG. The M31 tangential velocity measurement and contribution from the cosmological constant both increase the implied timing mass of the LG to be $\sim 5 \times 10^{12}$ M$_\odot$. Timing mass estimates for the LG tend to be larger than the sum of the Milky Way and M31 halo masses, and larger than independent LG mass estimators. Precision future kinematics have the potential to explore the origin of this difference, shed light on dark matter in the LG, the origin of its angular momentum, and possibly even local values of cosmological parameters.

Magnetic structure and asymmetric eruption of a 500 Mm filament rooted in weak-field regions

• Authors: Stefan Purkhart, Astrid M. Veronig, Robert Jarolim, Karin Dissauer, Julia K. Thalmann

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2508.18121

• Pdf link: https://arxiv.org/pdf/2508.18121

• Abstract We performed a detailed analysis of the magnetic structure and asymmetric eruption of a large (about 500 Mm) inverse S-shaped filament partially located in AR 13229 on February 24, 2023. We linked the filament's pre-eruptive magnetic configuration to its highly asymmetric eruption dynamics and the formation of a large-scale coronal dimming in a weak-field region (mean unsigned flux of about 5 G). To reconstruct the coronal magnetic field, we applied a physics-informed neural network (PINN)-based nonlinear force-free field (NLFFF) extrapolation method to a pre-eruption HMI vector magnetogram. The NLFFF extrapolation reveals a large-scale magnetic flux rope (MFR) of about 500 Mm in length, consistent with the filament. We identified an extended MFR footprint to the east that connects to the J-shaped flare ribbon, outlining where the coronal dimming began. Overlying strapping fields connect to the area into which the dimming and flare ribbon later expand. This configuration explains the formation of the dimming as a stationary flux rope and strapping flux dimming, with subsequent expansion driven by the growth of the MFR footprint through strapping-strapping reconnection. Conversely, the western filament leg shows multiple anchor points and strong overlying magnetic fields, which suppressed the dimming and partially confined the eruption on that side. The reconstructed pre-eruptive NLFFF configuration offers a clear physical explanation for the asymmetries seen in the eruption, flare geometry, and coronal dimming. This demonstrates that PINN-based NLFFF extrapolation can effectively model large-scale filaments extending into weak-field regions, enhancing our understanding of complex solar eruptions.

Shocks and complex chemodynamics in the metal-poor starburst galaxy CGCG 007-025 revealed through high-resolution echelle spectroscopy

• Authors: Macarena G. del Valle-Espinosa, Vital Fernández, Rubén Sánchez-Janssen, Ricardo Amorín, Karla Z. Arrellano-Córdova, Konstantina Boutsia

• Subjects: Subjects: Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2508.18160

• Pdf link: https://arxiv.org/pdf/2508.18160

• Abstract We use Magellan/MIKE echelle spectroscopy to conduct an in-depth chemodynamical analysis of the most luminous star-forming region within the metal-poor starburst dwarf galaxy CGCG 007-025. Leveraging the exceptional high resolution (R$\sim$50,000) and broad wavelength coverage, we apply Bayesian inference to simultaneously model the fluxes of 30 emission lines spanning the wavelength range 3400-9200Å. Employing a two-region ionisation model, we characterise various gas properties including electron temperature, electron density, and chemical abundances across different elements. Our direct-method inferred metallicity yields $\rm 12+\log(O/H)=7.77\pm0.03$, placing the galaxy in the metal-poor regime. Furthermore, Metal-to-Oxygen ratios such as log(S/O), log(Ne/O) or log(Ar/O) are in full agreement with the values derived for the Milky Way, consistent with expectations from stellar evolutionary models. The brightest emission lines are kinematically complex, with modelling requiring up to four distinct components. The exceptional resolution and signal-to-noise ratio of the data unveil asymmetric and wide ($\sigma_{HeII} \approx$ 35km/s) HeII$\lambda$4686 emission. The flux ratio of this nebular line, together with the absence of other high ionisation species such as [NeV]$\lambda$3426, indicates the presence of fast radiative shocks. This dataset underscores the capability of echelle spectroscopy in delivering comprehensive chemodynamical analyses of starbursts in the Local Volume.

Far-Infrared Emission from a Late Supernova Remnant in an Inhomogeneous Medium

• Authors: S.A. Drozdov, S. Yu. Dedikov, E.O. Vasiliev

• Subjects: Subjects: Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2508.18215

• Pdf link: https://arxiv.org/pdf/2508.18215

• Abstract The interstellar dust grains are swept up during the expansion of the supernova (SN) remnant, they penetrate behind the shock front, where they are heated and destroyed in the hot gas. This leads to a change in emissivity of such grains. In this work, we consider the evolution of the infrared (IR) luminosity of the SN remnant expanding into an inhomogeneous interstellar medium with lognormal distribution of the density fluctuations. The IR luminosity of the swept-up interstellar dust rapidly increases during the first several thousand years after the SN explosion, and reaches the maximum value. Afterwards, it decreases due to the destruction of the dust grains in hot gas and their declining emissivity in the cooling down gas of the shell. We show how the IR luminosity of dust in the SN remnant depends on the dispersion of the gas density in front of the SN shock front. We find that for the significant period of time (40 - 50 kyr) the maximum of the dust IR luminosity peaks at the range centered at 70$\mu$m. Therefore, this band can be considered as the most optimal range for studying the late SN remnants. We illustrate that during evolution, the dust temperature changes from 70 to 20 K, and only slightly depends on the inhomogeneity of the medium. In the radiative phase, the strong emission lines of metal ions emerge above the dust continuum. Their luminosity rapidly increases and exceeds the dust continuum luminosity by $\sim 10-10^3$ times. The point in time when the high luminosity in the lines is reached strongly depends on the inhomogeneity of the medium. We discuss possibilities for detection of the IR emission both in dust continuum and in lines. We expect that their ratios will allow to estimate the inhomogeneity of the medium, where the remnant is expanding.

by olozhika (Xing Yuchen).

2025-08-26