Peer Revenue Returns subject to peer review

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 28 July

Earth and Planetary Astrophysics

Cloud and ammonia vertical profiles in the equatorial atmosphere of Jupiter determined from visible to near-IR observations made by VLT/MUSE, Cassini/VIMS, IRTF/SpeX and Juno/JIRAM

Patrick G. J. Irwin, Asier Anguiano-Arteaga, Michelle Colantoni et al. (+8 more)

We present a combined cloud/ammonia model for Jupiter's equatorial atmosphere from 0.1 to 10 bar, consistent with observations made at a range of observation geometries from 0.35 to 5.15 $\mu$m by VLT/MUSE, Cassini/VIMS, IRTF/SpeX and Juno/JIRAM. Our cloud model has three components: 1) an optically-thick lower cloud (radius $r$$\sim$$10$ $\mu$m) at 1-2 bar; 2) an optically-thin upper cloud ($r$$\sim$$10$ $\mu$m) at $\sim$0.55 bar; and 3) a layer of blue-absorbing chromophore particles ($r$$\sim$$0.2$ $\mu$m) situated within the main lower cloud. The ammonia profile is intimately linked with the cloud profile with the lower cloud coinciding with an initial drop in ammonia abundance and the upper cloud coinciding with the ammonia condensation level. The large lower cloud particles are highly scattering at visible wavelengths, allowing sunlight to scatter through the clouds and be Rayleigh-scattered from the deep atmosphere. At 5 $\mu$m, the lower cloud particles are found to be more absorbing, with the belt/zone differences mostly accounted for by changes in the single-scattering albedo of these particles and secondarily by changes in the cloud opacity. The spectral properties of these lower cloud particles are possibly consistent with a component of water ice. The upper cloud particles need a distinct absorption band near 3 $\mu$m, possibly consistent with a component of ammonia ice. We note that we do not need a separate upper-level photochemical haze in our model. Instead, we find that the features seen at methane-absorbing wavelengths are caused by variations in the opacity and vertical extent of the upper cloud layer.
Read the full abstract

All authors Patrick G. J. Irwin, Asier Anguiano-Arteaga, Michelle Colantoni, Joseph Penn, Santiago Pérez-Hoyos, Davide Grassi, Alessandro Mura, Charlotte L. B. Alexander, Leigh N. Fletcher, Simon C. A. Toogood, Michael T. Roman

Cosmology and Nongalactic Astrophysics

No preference for generalized emergent dark energy from current cosmological data

Vipin Kumar Sharma, Himanshu Chaudhary, Salvatore Capozziello et al. (+2 more)

In this work, we revisit the generalized emergent dark energy model by confronting it with DESI DR2 baryon acoustic oscillation measurements, in combination with joint CMB data from ACT, SPT, and Planck, as well as Type Ia supernova samples including Pantheon$^+$, DES-Dovekie, and Union3. We find that the GEDE model remains compatible with the $\Lambda$CDM paradigm, with no statistically significant preference for deviations when all datasets are combined. In particular, the key model parameter $\Delta$ is consistent with the $\Lambda$CDM value $\Delta = 0$ within $2\sigma$ once SNe Ia data are included. Despite this overall agreement, the GEDE model does not exhibit the phantom crossing suggested by DESI DR2. Instead, the evolution of the dark energy equation of state $w(z)$ indicates that the model behaves either as a full phantom ($w < -1$) or quintessence ($w > -1$), depending on the dataset combination, without a clear transition across $w = -1$. When Pantheon$^+$ data are included, the model converges closely to $\Lambda$CDM with $w \simeq -1$. The GEDE model does not alleviate the existing cosmological tensions. The inferred values of $H_0$ remain in the range $67.9$-$69.8\ \mathrm{km,s^{-1},Mpc^{-1}}$, while the sound horizon $r_d$ and clustering parameter $S_8$ remain consistent with $\Lambda$CDM, failing to resolve the $H_0$ and $S_8$ tensions. Finally, both Gaussian significance levels ($<2\sigma$) and Bayesian evidence ($\ln B_{i,j} < 1$) indicate no statistically significant preference for GEDE over $\Lambda$CDM. We conclude that, although DESI DR2 hints at dynamical dark energy, the GEDE model remains observationally indistinguishable from $\Lambda$CDM and does not support the Quintom-B-type behavior suggested by DESI DR2.
Read the full abstract

All authors Vipin Kumar Sharma, Himanshu Chaudhary, Salvatore Capozziello, Dhruba Jyoti Gogoi, G. Mustafa

Earth and Planetary Astrophysics · Cross-listed from physics.optics

Geometry resolved atomic oxygen risk assessment for very low earth orbit spacecraft

Gun Hi Won, Hyun Jung Kim, SongYi Park et al. (+3 more)

Atomic oxygen (AO) is a major durability concern for spacecraft in very low Earth orbit (VLEO), yet orbit-averaged fluence does not resolve exposure on individual surfaces and internal components. This study develops a geometry-resolved AO assessment by coupling NRLMSISE-00, HWM07, and SYSTEMA ATOMOX. One-year simulations were performed for a 350 km circular Sun-synchronous orbit at LTAN 06:00 and 12:00 using a baseline spacecraft, a wedge-modified body, and two synthetic aperture radar antenna sub-arrays. The LTAN 12:00 orbit produced 8-10% higher orbit-averaged AO flux than LTAN 06:00. For the baseline geometry, the ram-facing surface accumulated 6.9-7.5 x 10^21 atoms/cm^2, whereas side and zenith/nadir surfaces received only 3-5% of the ram fluence. Material-specific erosion yields changed the component-level risk ranking: the CFRP zenith panel was predicted to erode by 15.1-16.2 um/year despite receiving much lower fluence than the ram-facing multilayer insulation. The wedge generated approximately one order of magnitude spatial variation through local shielding. Housing openings also allowed AO to reach internal printed circuit boards, with maximum annual fluences of 9.5 x 10^16 and 4.0 x 10^19 atoms/cm^2 in the H- and V-polarized antenna models, respectively. HWM07 winds produced 10-20% side-panel asymmetry, which decreased below 1% when winds were disabled. Comparison with MISSE-8 reproduced the measured zenith-to-ram ratio of approximately 4% but underpredicted wake exposure, identifying a limitation of ballistic ray tracing. These results demonstrate that VLEO AO durability requires coupled consideration of orbit, atmospheric winds, geometry, and material response.
Read the full abstract

All authors Gun Hi Won, Hyun Jung Kim, SongYi Park, ChangWon Seo, Eunji Lee, SeongSik Yoon

Astrophysics of Galaxies

Chemistry of Dark Molecular Clouds

Yuri Aikawa, Izaskun Jimenez-Serra and Paola Caselli

Recent molecular line surveys, particularly toward the starless core TMC-1 CP, have greatly expanded the inventory of interstellar molecules, revealing numerous isomers and even aromatic species. Their diverse formation pathways—from ion-molecule reactions to the possible fragmentation of carbonaceous grains—remain under debate, linking chemistry to the life cycle of the interstellar medium. Simple tracers such as carbon chains and deuterated ions are used to probe the physical conditions and evolutionary state of nearby filaments and cores, as well as in massive infrared dark clouds. Ice chemistry has also entered a new era with JWST: spatial distributions of ices indicate a connection between catastrophic freeze-out, established in the prestellar core L1544, and formation of complex organic molecules. Overall, TMC-1 CP and L1544 are not outliers but representative laboratories of molecular cloud physics and chemistry. Extending these findings across diverse environments, from the Central Molecular Zone to low-metallicity galaxies, is essential for a unified picture of how interstellar chemistry regulates the path from clouds to stars and planets.
Read the full abstract

Solar and Stellar Astrophysics

Decay Length of Slow Magnetoacoustic Waves in the Solar Corona using SDO/AIA and SolO/EUI

R. L. Meadowcroft, N. Narang, D. Berghmans et al. (+2 more)

Slow magnetoacoustic waves have been observed in the solar corona for decades; yet, existing theories do not fully explain the wide range of observed decay lengths, and measurements from different instruments frequently disagree. We present two events with simultaneous SDO/AIA and Solar Orbiter/EUI-HRIEUV observations of slow waves in sunspot-anchored coronal fan feathers. In Event 1, the LoS are separated by 16.2 degrees, while in Event 2, they are almost parallel. Using time-distance analysis, we identify waves with periods in the 3-minute band and quantify wave decay using the exponential folding length. When LoS are non-parallel, the ratio of decay lengths measured by the two instruments, $\lambda_\mathrm{ratio} = \lambda_{\mathrm{AIA}} / \lambda_{\mathrm{EUI}}$ varies widely, with both $\lambda_\mathrm{ratio} > 1$ and $\lambda_\mathrm{ratio} < 1$ observed. However, when the LoS are almost parallel, the decay lengths agree with one another, and $\lambda_\mathrm{ratio} \approx 1$. These results show that the angle between the LoS and the wave propagation direction is key to determining the apparent decay of slow waves, a factor that has not yet been systematically accounted for. Since statistical studies of decay lengths constrain coronal energy-loss mechanisms, observational effects beyond simple projection must be corrected to reliably infer the underlying physical dissipation processes.
Read the full abstract

All authors R. L. Meadowcroft, N. Narang, D. Berghmans, M. Dominique, V. M. Nakariakov

High Energy Astrophysical Phenomena

The afterglow of gamma-ray burst - supernova connections

Marco Muccino, Rahim Moradi and Yu Wang

The X-ray afterglow of several long gamma-ray bursts (LGRBs) associated with broad line type Ib/c supernovae (SNe) exhibits a standard non-thermal afterglow, commonly attributed to synchrotron emission from a relativistic jet, and an evolving thermal component whose physical origin is still debated. We investigate whether these thermal and non-thermal components can be described within a common analytical framework and whether their temporal evolution can provide insight into the physical connection between relativistic jets and SN ejecta. We combine a phenomenological description of the synchrotron emission of the non-thermal energy associated with the relativistic jet with a diffusion model describing the thermal evolution of the jet-affected portion of the SN ejecta. The resulting coupled system is solved analytically, leading to closed-form expressions for both non-thermal and thermal luminosities. We apply the model to the following systems: GRB 060218A/SN 2006aj and GRB 171205A/SN 2017iuk. The proposed formalism reproduces the main features of both thermal and non-thermal light curves. In both systems, the thermal luminosity follows a temporal evolution similar to that of the non-thermal component up to the plateau phase. The inferred thermal energy stored in the jet-affected ejecta is found to be a fraction of the energy coupled to the observed non-thermal emission. The characteristic timescales obtained from the fits suggest a direct link between the evolution of the jet and the thermal response of the expanding ejecta. Although simplified, the proposed framework provides a unified analytical description of LGRB afterglows and their thermal counterparts and offers a useful tool for investigating the physical connection between relativistic jets and SNe Ib/c.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Neutrino-electron scattering kernels in isotropic media

Jens Chluba, Bryce Cyr, Michiru Uwabo-Niibo et al. (+1 more)

In the early universe, neutrinos undergo many interactions with the particles in the plasma. Key processes are the scattering of neutrinos by free electrons and positrons. In this paper, we derive general expressions for the electron neutrino-electron scattering kernel in isotropic media, analytically simplifying the 5D collision integral to two dimensions. We follow a procedure that is similar to the derivation of the Compton scattering kernel to reduce the angular integrals, yielding a compact analytic expression in terms of elementary functions that can be easily evaluated. We illustrate the properties of this kernel and also compute its first moments analytically, providing insights into the energetics of the redistribution process. For comparison, we consider the photon-electron scattering kernel, highlighting differences and similarities. We then explain how the obtained expressions can also be applied to the $\nu_{\mu/\tau}$-electron and neutrino-positron scattering processes. The results presented here may be useful in the context of Big Bang Nucleosynthesis and were added as an extension to the Compton scattering library CSpack for more general applications.
Read the full abstract

All authors Jens Chluba, Bryce Cyr, Michiru Uwabo-Niibo, Masahide Yamaguchi

Solar and Stellar Astrophysics

A systematic study of quiescent and outburst properties of X-ray-bright young stellar objects using XMM-Newton

Koki Sakuta, Ikuyuki Mitsuishi, Seiya Sasamata et al. (+6 more)

Young Stellar Objects (YSOs) exhibit strong X-ray emission, widely attributed to magnetic reconnection and magnetospheric accretion; however, owing primarily to limited photon statistics, observational tests of these mechanisms have often relied on simplified analyses, leaving room for more precise constraints on their emission processes. We aim to derive the X-ray properties of X-ray-bright YSOs selected from multiple star clusters and investigate their emission mechanisms through an approach from multiple perspectives based on timing and spectroscopic analysis. We performed a systematic search of XMM-Newton archival observations and constructed a sample of 51 X-ray-bright YSOs for timing and spectroscopic analyses. We identified quiescent and outburst phases through timing analysis, performed phase-resolved multi-temperature spectroscopy. Multi-temperature plasma structures are detected in both quiescent and outburst emission. The relationships among the timing and spectral parameters are broadly consistent with a magnetic-reconnection scenario. Comparison with Gaia DR3 stellar parameters suggests that magnetospheric accretion alone has difficulty explaining most of the fitted X-ray temperatures, although the coolest model components with $kT \lesssim 0.3$ keV may include an accretion-shock contribution. After separating these low-temperature components, the remaining quiescent components show a clearer positive correlation in the $EM$–$kT$ plane, with magnetic-loop lengths distributed around $10^{12}$ cm. Neupert-like behavior, the temporal evolution of temperature and emission measure, the Rossby-number activity relation, and positive correlations between quiescent and outburst properties all suggest that magnetic reconnection plays a key role in both phases.
Read the full abstract

All authors Koki Sakuta, Ikuyuki Mitsuishi, Seiya Sasamata, Daigo Nonaka, Mai Yamashita, Shin Toriumi, Takato Tokuno, Yohko Tsuboi, Hiroshi Kobayashi

Astrophysics of Galaxies

From compact jets to extended lobes: radio morphologies of distant quasars at z > 4

K. É. Gabányi, M. Kunert-Bajraszewska, A. Krauze et al. (+9 more)

High-redshift quasars play an essential role in studying the growth and evolution of supermassive black holes and active galactic nuclei (AGN). Radio-loud quasars additionally enable us to investigate the interactions between the jets and their environment. We aimed to reveal the radio morphology of three radio quasars at redshifts z>4 that contain milliarcsecond (mas) scale compact radio features according to previous very long baseline interferometry (VLBI) observations, but show significant flux density at arcsecond scales, indicating the presence of extended radio structure that cannot be sampled by the highest-resolution observations. We analysed radio interferometric data obtained at various angular resolutions and multiple frequencies, including observations made by the international Low-Frequency Array and the enhanced Multi-Element Remotely-Linked Interferometer Network. We also re-imaged archival European VLBI Network observations of our targets. Two quasars (J0813+3508 and J1231+3816) exhibit complex radio structures with hotspots, extended to tens of kpc. They resemble Fanaroff–Riley II-type radio galaxies with extremely bent jet morphology. The third object (J1548+3335) shows a one-sided structure of $\lesssim 10$ kpc size. There was no sign of relativistic boosting at its previous mas-scale resolution radio observations. Its radio power and (inferred) linear size derived from the lower-resolution observations are similar to the known high-power compact steep-spectrum sources. We found that the previously detected mas-scale compact radio features are related to the centres of the AGN or in one case to one of the hotspots in an extended lobe.
Read the full abstract

All authors K. É. Gabányi, M. Kunert-Bajraszewska, A. Krauze, S. Frey, M. Krezinger, Z. Paragi, H. Cao, T. An, L. I. Gurvits, K. Perger, T. Sbarrato, K. Rozgonyi

High Energy Astrophysical Phenomena

Residual Galactic binary foreground in LISA stochastic gravitational-wave background inference: source power concentration and spectral degeneracy

Ruo-Yu Guan and Yan Wang

Galactic compact binaries are expected to form a dominant foreground in the millihertz band of the Laser Interferometer Space Antenna (LISA). Residual power from injected sources that do not meet the adopted recovery criteria can bias stochastic gravitational-wave background (SGWB) inference or increase its uncertainty. We use LISA Data Challenge 2A Sangria injections and the Erebor comparison table to construct a catalog residual spectrum between 0.4 and 6.0 mHz with orbit-averaged long-wavelength Michelson \(X\) source powers. The source power concentration in each frequency bin determines the excess kurtosis of a random-phase source sum; instrumental noise and fiducial SGWB power strongly reduce the resulting excess kurtosis in most bins. The residual spectrum also overlaps an isotropic power-law SGWB in the mean binned power. We use a fixed covariance obtained by summing independent Fourier-mode power variances. For a frequency-independent SGWB with fiducial amplitude \(\Omega_0=10^{-11}\), marginalizing over the dimensionless residual-power factor \(\beta\) increases the \(\Omega_0\) uncertainty by \(13.6\%\) when the residual power is distributed uniformly over the Fourier frequencies in each bin. The largest Gaussian prior standard deviation on \(\beta\) that limits this increase to \(10\%\) is \(0.0073\). More concentrated distributions of the residual power among Fourier frequencies reduce the increase, reflecting unresolved frequency structure. Omitting the fiducial residual with the covariance held fixed shifts the best-fitting \(\Omega_0\) by \(119.5\) times the uncertainty obtained with \(\beta\) fixed. This projection of the residual spectrum onto the SGWB spectrum is not a posterior detection significance. The numerical values are conditional on the catalog-level scalar power model, fixed instrumental noise, and independent mode-power covariance.
Read the full abstract

Earth and Planetary Astrophysics

GRaTer-JAX: An Accelerated Package for Debris Disk Modeling

Mihir Kondapalli, Briley L. Lewis, Jaren N. Ashcraft et al. (+1 more)

GRaTer-JAX is a Python package for modeling debris disks, disks of dust around stars that pro- vide important clues about the formation, structure, and evolution of planetary systems. GRaTer (Generator of Ring-like, axisymmetric, optically Thin dust disks for regularized fitting) is a debris disk modeling framework originally developed for generating and fitting models of optically thin, ax- isymmetric dust disks. JAX is a Python package for high-performance computing that implements just-in-time compilation and auto-differentiation, enabling significant speedups in forward modeling workflows. GRaTer-JAX delivers a more powerful, efficient, and robust debris disk modeling framework than previous tools. Its JAX-based backend provides orders-of-magnitude speedups and analytic gradients, while its intuitive and extensible API unifies forward modeling, optimization, and inference within a single workflow. Combined with key additions to its disk model, it is capable of more advanced debris disk modeling, enabling research that was previously computationally impractical such as explorations of additional morphological parameters and disk composition via scattering phase functions.
Read the full abstract

All authors Mihir Kondapalli, Briley L. Lewis, Jaren N. Ashcraft, Maxwell A. Millar-Blanchaer

High Energy Astrophysical Phenomena

SN 2022xus: bridging the gap between Type IIP and IIL supernovae

Monalisa Dubey, Kuntal Misra, Naveen Dukiya et al. (+16 more)

We present optical photometric and spectroscopic observations of the Type~II supernova SN~2022xus. The SN reached its peak V band magnitude of $-16.32$ mag within $\sim$7 days of explosion, followed by a plateau phase lasting $\sim$94 days with a declination rate of $\sim$1.2 mag (100 day)$^{-1}$. Early time spectra exhibit broad features that could be caused by the blending of several high-ionisation lines, likely arising from a relatively weak interaction between the SN ejecta and the surrounding circumstellar medium (CSM). Compared to typical Type~IIP SNe, SN~2022xus exhibits a smaller H$\alpha$ absorption-to-emission ratio ($a/e$), indicating a relatively small hydrogen envelope mass at the time of explosion. From nebular-phase spectroscopy and bolometric light curve modelling, the progenitor mass is estimated to be in the range of 12 – 15 M$_\odot$. The multi-band light curve modelling using REDBACK infers a similar progenitor mass, a low mass-loss rate, and a confined CSM. Although several photometric and spectroscopic characteristics place the SN within the Type~IIL population, it displays mixed properties of both Type~IIP and Type~IIL SNe and cannot be cleanly classified into either subclass. We therefore identify SN~2022xus as a transitional event between Type~IIP and Type~IIL SNe, providing further evidence for a continuum between these two classes.
Read the full abstract

All authors Monalisa Dubey, Kuntal Misra, Naveen Dukiya, Kumar Pranshu, Raya Dastidar, K. Azalee Bostroem, Yize Dong, Joseph R. Farah, Estefania Padilla Gonzalez, Emily Hoang, D. Andrew Howell, Curtis McCully, Megan Newsome, Craig Pellegrino, Aravind Pazhayath Ravi, Nicolas Meza Retamal, Ajay Kumar Singh, Giacomo Terreran, Stefano Valenti

Cosmology and Nongalactic Astrophysics

Gravitational Waves from Superconducting Cosmic Strings

Jinyoung Jhun and Takashi Hiramatsu

We study the evolution of superconducting cosmic-string networks in a $U(1)_{\rm local}\times U(1)_{\rm global}$ field-theoretic model using three-dimensional lattice field simulations in an expanding universe. The scalar field charged under $U(1)_{\rm local}$ forms cosmic strings, while the scalar field associated with $U(1)_{\rm global}$ acts as a current carrier and condenses in their vicinity. We investigate the evolution of the string network for several values of the coupling constant between the string-forming and current-carrier fields and estimate the gravitational-wave power spectrum sourced by the resulting superconducting cosmic-string network. We find that the spectral shape depends on the coupling constant: as the interaction strength increases, the spectrum is suppressed on small scales. This feature may be probed by future high-frequency gravitational-wave observations.
Read the full abstract

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Parametrized beyond-Teukolsky framework in the time domain

Ciro De Simone, Sebastian H. Völkel, Kostas D. Kokkotas et al. (+1 more)

Modifications to General Relativity can significantly alter the perturbative response of black holes, leaving imprints on quasinormal-mode spectra, waveform amplitudes and phases, and late-time tails. The parametrized beyond-Teukolsky framework was introduced to capture possible deviations from Kerr dynamics, but the ringdown has so far only been explored as an eigenvalue problem. We present the first time-domain implementation of this framework and perform (2+1)-dimensional scattering experiments with Gaussian wave packets. This approach provides the full linear evolution of the perturbation, from the initial prompt response through the ringdown and into the late-time regime. Using frequency-domain eigenvalue results as benchmarks, we find excellent agreement for low azimuthal numbers, while higher azimuthal numbers are affected by mode mixing, which limits the precision of the extracted modes. We further use the time-domain waveforms to estimate quadratic and mixed coefficients within the linearized modified-potential model, providing a diagnostic for the regime of validity of the linear approximation. Beyond mode frequencies, we show that the deformation parameters can strongly affect the ringdown amplitude and phase, with trends that can be understood from the near-horizon structure of the modified potential. We also analyze the late- time behavior, finding that near-horizon deformations leave the tail exponent unchanged but can substantially shift the onset of the power-law decay. These results demonstrate that time-domain evolutions provide a complementary and flexible framework for testing parametrized deviations from General Relativity in black-hole perturbation theory.
Read the full abstract

All authors Ciro De Simone, Sebastian H. Völkel, Kostas D. Kokkotas, Salvatore Capozziello

Astrophysics of Galaxies

Interferometric molecular line observations toward the 21 {\mu}m protoplanetary nebula IRAS 06530-0213

Hao-Min Sun, Zhuang Zhang, Jun-Yang Liu et al. (+2 more)

The identification of the $21\,\mu\mathrm{m}$ feature in some protoplanetary nebulae remains a longstanding puzzle, whose interpretation requires characterization of the molecular gas environments of associated sources. Here, we present high-resolution interferometric observations from the Northern Extended Millimeter Array toward the $21\,\mu\mathrm{m}$ protoplanetary nebula IRAS 06530-0213. Multiple molecular transitions of $\mathrm{HC_3N}$, $\mathrm{C_4H}$, and $\mathrm{SiC_2}$ are detected and spatially resolved. We analyze these spectral lines alongside previously reported CO and $^{13}\mathrm{CO}$ emission toward this source. Differing from the extended barrel-like molecular structure traced by CO and $^{13}\mathrm{CO}$, $\mathrm{HC_3N}$ and $\mathrm{C_4H}$ are predominantly concentrated in the inner low-latitude equatorial zones. Reproducing the observed morphology requires $\mathrm{HC_3N}$ to possess a more inwardly concentrated abundance distribution compared with CO and $^{13}\mathrm{CO}$, implying that the inner equatorial regions provide favorable conditions for carbon-chain chemistry.
Read the full abstract

All authors Hao-Min Sun, Zhuang Zhang, Jun-Yang Liu, Sheng-Li Qin, Yong Zhang

Astrophysics of Galaxies

From Starburst to Quenching: Physical Properties of Extremely Compact Starbursts at z$\sim$0.1

Can Xu, Mengyuan Xiao, Min Bao et al. (+5 more)

The compaction phase plays a crucial role in galaxy evolution, as it is strongly linked to star formation activities and structural transformation. We have identified a sample of extremely compact starburst galaxies (eCSBs) at low redshift~(z$\sim$0.1), which represent this critical evolutionary stage. These eCSBs are massive outliers with intense star formation and high infrared luminosities comparable to (U)LIRGs, while their structure already resembles quiescent galaxies. To investigate their molecular gas properties, we conducted IRAM 30m observations of $^{12}$CO J = 1–0 and $^{12}$CO J = 2–1 emission lines. Our results indicate that eCSBs exhibit a notably low molecular gas fraction~($\sim3\%$), and short gas depletion time~($\sim$ 20 Myr), suggesting that these galaxies are rapidly exhausting their remaining gas reservoir. Compared to normal (U)LIRGs, eCSBs show systematically lower $^{12}$CO(2-1)/$^{12}$CO(1-0) ratio~($R_{21} \sim 0.65 \pm 0.06$), similar to main sequence galaxies. The relatively low CO excitation may be associated with their high central stellar mass densities. These findings provide new insight into the molecular gas properties of galaxies during the compaction phase, highlighting their unique condition and rapid evolution toward quiescence.
Read the full abstract

All authors Can Xu, Mengyuan Xiao, Min Bao, Qiusheng Gu, Longji Bing, Yong Shi, Yifei Jin, Shiying Lu

Instrumentation and Methods for Astrophysics

LiteBIRD Mission Overview after Mission Reformation

LiteBIRD Collaboration: K. Aizawa, H. Akamatsu, R. Akizawa et al. (+171 more)

LiteBIRD is a JAXA-led space mission designed to produce all-sky microwave polarization maps. Its primary science goal is to test representative inflationary models by measuring the cosmic microwave background $B$-mode polarization generated by primordial gravitational waves, while also providing new insights into cosmology, particle physics, and astrophysics. The mission concept has been updated following the reformation activities initiated after the Mission Definition Review in 2024. The current concept preserves the central scientific objectives, while simplifying the payload configuration: a single telescope covers 12 frequency bands with band centers spanning 40 to 402~GHz, corresponding to an optical coverage of 34–448~GHz. The telescope is a cross-Dragone reflector with a 500~mm aperture diameter, cooled to approximately 5~K and coupled to transition-edge-sensor bolometer arrays operated at 0.1~K. LiteBIRD will observe from a Lissajous orbit around the Sun–Earth L2 point during a nominal 3-year survey. More specifically, the primary scientific objective is to achieve total uncertainty in the tensor-to-scalar ratio of $\delta r < 0.002$ (68% C.L.), including contributions from foreground residuals, statistical uncertainties, instrumental systematics, and margin contingency. The corresponding map-noise requirements are specified separately for the low-, mid-, and high-frequency ranges over the reionization and recombination multipole ranges. This sensitivity makes LiteBIRD unique not only for inflationary science but also for a broad range of scientific investigations probing the history of both the early and late Universe, as well as for astrophysical processes, including Galactic science. This paper summarizes the scientific objectives, updated payload and instrument concepts, observation strategy, and ground segment plans.
Read the full abstract

All authors LiteBIRD Collaboration: K. Aizawa, H. Akamatsu, R. Akizawa, E. Allys, A. Anand, D. Audley, J. Aumont, S. Azzoni, C. Baccigalupi, M. Ballardini, A. J. Banday, G. Barbieri Ripamonti, R. B. Barreiro, N. Bartolo, S. Basak, M. Bersanelli, A. Besnard, D. Blinov, F. Bouchet, F. Boulanger, N. Brancadori, T. Brinckmann, E. Calabrese, P. Campeti, A. Carones, F. Carralot, F. J. Casas, J. Chandran, Y. Chinone, M. Citran, F. Columbro, A. Coppolecchia, F. Cuttaia, P. Dal Bo, P. de Bernardis, T. de Haan, E. de la Hoz, M. De Lucia, M. De Petris, S. Della Torre, C. Dickinson, P. Diego-Palazuelos, J. J. Díaz García, T. Dotani, M. Douspis, K. Ebisawa, H. K. Eriksen, J. Errard, E. Ferreira, F. Finelli, C. Franceschet, R. Fujimoto, U. Fuskeland, G. Galloni, M. Galloway, M. Gerbino, M. Gervasi, R. T. Génova-Santos, T. Ghigna, S. Giardiello, E. Gjerløw, M. Gomes, A. Gruppuso, J. E. Gudmundsson, P. Hargrave, S. E. Harper, M. Hasegawa, M. Hazumi, S. Henrot-Versillé, L. T. Hergt, E. Hivon, K. Ichiki, K. Ikuma, T. L. Irikura, H. Ishino, B. Jost, R. Keskitalo, K. Kikuno, K. Kohri, E. Komatsu, L. Lamagna, M. Lattanzi, C. Leloup, M. Lembo, F. Levrier, J. Liu, A. I. Lonappan, M. López-Caniego, G. Luzzi, J. Macias-Perez, A. Maeda, B. Maffei, D. Maino, V. Maranchery, E. Martínez-González, S. Masi, S. Matarrese, F. T. Matsuda, T. Matsumura, S. Micheli, M. Migliaccio, M. Monelli, L. Montier, L. Mousset, S. Myozen, Y. Nagano, R. Nagata, K. Nagayoshi, M. Najafi, T. Namikawa, P. Natoli, F. Noviello, A. Occhiuzzi, K. Odagiri, S. Oguri, H. Ohsaki, S. Okumura, L. Pagano, A. Paiella, D. Paoletti, S. Paradiso, G. Pascual-Cisneros, G. Patanchon, V. Pavlidou, F. Piacentini, M. Piat, G. Piccirilli, M. Pinchera, G. Pisano, G. Polenta, L. Porcelli, F. S. Porter, M. Reinecke, M. Remazeilles, A. Rizzieri, J. A. Rubiño-Martín, M. Ruiz-Granda, Y. Sakurai, L. Salvati, J. Sanghavi, G. Savini, D. Scott, Y. Sekimoto, M. Shiraishi, G. Signorelli, S. Stellati, R. Stompor, R. M. Sullivan, R. Takahashi, R. Takaku, H. Takakura, Y. Takase, A. Tartari, K. Tassis, K. Tateoka, L. Terenzi, M. Tomasi, M. Tristram, M. Tsujimoto, D. Vaccaro, L. Vacher, B. van Tent, P. Vielva, S. Vinzl, K. Watanuki, D. J. Watts, I. K. Wehus, G. Weymann-Despres, B. Winter, E. J. Wollack, N. Y. Yamasaki, K. Yoshihara, A. Zacchei, M. Zannoni

High Energy Astrophysical Phenomena

Tightening Bounds on Warm Dark Matter with High-Redshift Gamma-Ray Bursts

Jun-Jie Wei, Jing-Meng Hao, Ding-Fang Hu et al. (+4 more)

The cold dark matter paradigm successfully explains large-scale structure but faces persistent tensions on small scales. Warm dark matter (WDM) with $\mathrm{keV}$-scale particles can alleviate these issues by suppressing small-scale structure formation. The presence of collapsed structures at high redshifts places strong lower limits on the WDM particle mass $m_x$. Gamma-ray bursts (GRBs) are ideal high-redshift probes due to their extreme brightness. Using the most recent Swift GRB data accumulated over the past two decades, we derive robust constraints on $m_x$ by conservatively assuming that the comoving GRB formation rate is proportional to the cosmic star formation rate (SFR), with an additional redshift evolution parameterized as $(1+z)^\alpha$. Applying a maximum-likelihood analysis to 118 GRBs with redshift $z<10$ and luminosity $L\ge 4.0\times10^{52}\,\mathrm{erg\,s^{-1}}$, we obtain $m_x \gtrsim 1.23\,\mathrm{keV}$ and $\alpha=1.57^{+1.14}_{-0.57}$ at the 95% confidence level (CL). The no-evolution scenario ($\alpha=0$), in which the GRB rate exactly traces the SFR without additional redshift evolution, is excluded at the $5\sigma$ level. Adopting the best-fit value $\alpha=1.57$ as a prior tightens the lower limit on $m_x$ to $m_x \gtrsim 1.59\,\mathrm{keV}$ at the 95% CL. These robust constraints demonstrate that GRBs are a powerful probe of the early Universe. A better understanding of the relationship between the GRB rate and the SFR would enable even tighter limits on WDM models.
Read the full abstract

All authors Jun-Jie Wei, Jing-Meng Hao, Ding-Fang Hu, Yang Liu, Bao Wang, Xi Kang, Xue-Feng Wu

Earth and Planetary Astrophysics

KMT-2025-BLG-0975Lb and KMT-2025-BLG-1160Lb: Two Uranus-Mass Planets Beyond the Snow Line Discovered by Microlensing

Cheongho Han, Chung-Uk Lee, Andrzej Udalski et al. (+27 more)

We present the analysis of two planetary microlensing events, KMT-2025-BLG-0975 and KMT-2025-BLG-1160, discovered during the 2025 Galactic bulge microlensing season through high-cadence survey observations. In both events, short-duration anomalies near the peaks of the lensing light curves reveal the presence of planetary companions. Light-curve modeling yields planet-to-host mass ratios of $q = 8.6 \times 10^{-4}$ for KMT-2025-BLG-0975 and $1.3 \times 10^{-4}$ for KMT-2025-BLG-1160. For KMT-2025-BLG-0975, finite-source effects are detected, enabling a measurement of the angular Einstein radius, whereas only a lower limit on this quantity is obtained for KMT-2025-BLG-1160. We estimate the physical parameters of the lens systems through Bayesian analyses constrained by the measured microlensing observables. The results indicate that the planetary companions have masses of $M_{\rm p}=29.8^{+50.5}_{-16.0}~M_\oplus$ for KMT-2025-BLG-0975Lb and $25.4^{+15.5}_{-14.1}~M_\oplus$ for KMT-2025-BLG-1160Lb. Both planets have masses comparable to that of Uranus. The host stars are inferred to be a low-mass M dwarf with a mass of $M_{\rm h}=0.10^{+0.18}_{-0.06}~M_\odot$ for KMT-2025-BLG-0975L and a late K dwarf with a mass of $M_{\rm h}=0.58^{+0.35}_{-0.32}~M_\odot$ for KMT-2025-BLG-1160L. The projected planet–host separations are $a_\perp=0.81^{+0.10}_{-0.11}$~au for KMT-2025-BLG-0975Lb and $a_\perp=2.56^{+0.48}_{-0.71}$~au and $3.29^{+0.61}_{-0.92}$~au for the inner and wide solutions, respectively, of KMT-2025-BLG-1160Lb. In both systems, the planets are located beyond the expected snow-line distances of their hosts, placing them in the cold ice-giant regime.
Read the full abstract

All authors Cheongho Han, Chung-Uk Lee, Andrzej Udalski, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Hongjing Yang, Doeon Kim, Dong-Jin Kim, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radosław Poleskim Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

GSpyNetTree-O4: an event validation tool used in the fourth LIGO-Virgo-KAGRA observing run

Sofia Alvarez-Lopez, Man Leong Chan, Franz S. Herbst et al. (+7 more)

The frequent presence of non-Gaussian transient noise, or glitches, in gravitational-wave detector data can affect gravitational-wave searches, parameter estimation, and downstream analyses. To identify and mitigate transient noise near gravitational-wave candidates in a timely manner, the LIGO-Virgo-KAGRA Collaboration employs the Data Quality Report. In the fourth observing run, GSpyNetTree-O4 was deployed within this framework as a tool for glitch classification and event validation. We describe GSpyNetTree-O4 and the main developments relative to its predecessor, GSpyNetTree. The most important update was a new architecture that allowed the simultaneous identification of glitches and gravitational-wave signals when both were present in the same input. We also expanded and augmented the training set with examples in which simulated gravitational-wave signals overlapped with real glitches, and applied $60\,\mathrm{Hz}$ calibration corrections to better match the data expected during the fourth observing run. On test data, the low-mass, high-mass, and extremely high-mass classifiers identified $97.9\%$, $97.7\%$, and $95.4\%$ of glitches, respectively. Among samples without a glitch, including gravitational-wave-only and No Glitch samples, the classifiers correctly reported no data-quality issues in $97.1\%$, $96.6\%$, and $96.0\%$ of cases, respectively. We further assessed the robustness of GSpyNetTree-O4 on unseen glitch morphologies, a small set of Virgo glitches from the fourth observing run, and different choices of the $Q$-value used to construct the time-frequency inputs. GSpyNetTree-O4 was successfully deployed as a Data Quality Report tool and increased automation in gravitational-wave event validation workflows.
Read the full abstract

All authors Sofia Alvarez-Lopez, Man Leong Chan, Franz S. Herbst, Dhatri Raghunathan, Airene Ahuja, Annudesh Liyanage, Julian Ding, Alejandro Garcia-Varela, Raymond Ng, Jess McIver

Monday 27 July

Astrophysics of Galaxies · Cross-listed from gr-qc

Observationally Reconstructed Spacetime of NGC 5907: Dark-Matter-Corrected Black Hole Thermodynamics and Galactic Shadow

Aritra Sanyal Farook Rahaman

We present an observationally guided relativistic framework to investigate the thermodynamic and optical properties of a black hole in the NGC 5907 galaxy. By reconstructing the spacetime directly from the observed rotation curve, we obtain a dark-matter-corrected metric that incorporates both the galactic halo and the central compact object. The reconstructed geometry admits horizon solutions, allowing us to evaluate the Hawking temperature, Bekenstein-Hawking entropy, and heat capacity, which indicate a thermodynamically stable supermassive black hole influenced by its dark matter environment. We further analyze photon motion and the resulting gravitational shadow, deriving the photon sphere, critical impact parameter, and shadow size. Comparison with WISE W1 infrared photometry shows consistency with the predicted suppression of photon escape near the shadow radius. These results establish a unified link between galactic rotation curves, dark matter, black hole thermodynamics, and observable photometric signatures.
Read the full abstract

High Energy Astrophysical Phenomena

Magnus mountains on spinning neutron stars

Yashaswi Gangwar and David Ian Jones

We investigate the formation of a "Magnus mountain” on a neutron star, arising from the non-axisymmetric Magnus force acting on the elastic crust by pinned superfluid vortices. Such a deformed star would act as a source of continuous gravitational waves. We consider a compressible two-component stellar model and solve the coupled equations of motion for the fluid and elastic components self-consistently, allowing the stellar deformation and the resulting mass quadrupole to be determined. For simplicity, we model the star as an infinitely long cylinder, consisting of a fluid region with a thin ocean and crust. We find that the current quadrupole is zero, while the Magnus forces are strong enough to produce (dimensionless) mass quadrupoles as large as $\sim 10^{-5}$, and so would be limited only by the finite strength of the vortex pinning and the breaking strain of the star's elastic crust. Such large deformations are promising from the point of view of the detection of continuous gravitational waves by current and future detectors, and motivate further work on more realistic stellar models.
Read the full abstract

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Phantom-Divide Crossing in Barrow-Tsallis Holographic Dark Energy with a Scale-Dependent Barrow Exponent

D. A. Yerokhin

Phantom-divide crossing is studied in spatially flat cosmologies with standard Friedmann equations, separately conserved holographic dark energy and a barotropic fluid, and the future event horizon as the infrared cutoff. The horizon entropy and dark-energy density are prescribed by $ S_h=S_{\mathrm{BH}}F(L) $ and $ \rho_X\propto F(L)/L^2 $, where $ F(L) $ is smooth, positive and single-valued, with $ \chi=\mathrm{d}\ln F/\mathrm{d}\ln L $. For $ w_b>-1 $, $ 0<\Omega_X<1 $ and $ \chi<2 $ along the trajectory, at most one phantom-divide crossing is possible. If a crossing occurs, dark energy passes from the quintessence regime into the phantom regime at a maximum of the horizon radius. The crossing kinematics determines the local entropy-scaling dimension and the sign of the local Chevallier-Polarski-Linder coefficient. Integrating the locally prescribed scale-dependent Barrow exponent reconstructs the Barrow-Tsallis entropy function. A necessary and sufficient event-horizon consistency criterion selects admissible solutions, whose late-time asymptotics include de Sitter states, Type III and Big Rip singularities, and accelerated power-law expansion under the corresponding parameter conditions. A numerical comparison with a constant Barrow exponent distinguishes the occurrence of a crossing from the effect of exponent variation on late-time evolution. With an adiabatic barotropic fluid, additive total entropy and an equilibrium Gibbs relation for dark energy, the generalized second law fails at the kinematic crossing for positive barotropic-fluid entropy and finite nonzero dark-energy temperature. The divergence of $ c_a^2 $ shows that the purely barotropic adiabatic description of perturbations breaks down. This divergence alone does not establish physical instability.
Read the full abstract

Astrophysics of Galaxies · Cross-listed from gr-qc

Dark Matter Deficient Galaxies as Probes of Dark Matter

Oem Trivedi and Abraham Loeb

Dark matter deficient galaxies provide a direct way to test whether baryons and dark matter can become sufficiently separated during galaxy evolution. We formulate a Dark Matter-Baryon Separability condition based on the relative incorporation efficiencies of the two components, requiring the final dark matter to baryon ratio to fall below an observationally defined threshold. Applied to high speed collisions, this condition constrains dark matter baryon momentum transfer cross section, interacting dark matter fraction and the efficiency of gravitational recapture. The same framework gives us bounds on the abundance and cooling time of dissipative dark matter, and on the integrated escape rate of ultralight fuzzy dark matter from shallow or tidally disturbed potentials. These results show how dark matter deficient galaxies can complement cosmological and laboratory probes by constraining late time dark matter interactions, dissipation and halo stability.
Read the full abstract

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

Emergence and Detection of Electron-Scale Current Sheets in Turbulence with MMS Observations and fully kinetic 3D simulations

Zachary Davis, Alexandros Chasepis, Colby Haggerty et al. (+2 more)

The solar wind is characterized by turbulence, where a cascade produces intermittent current structures called current sheets (CS) that efficiently dissipate energy into the plasma. These have been studied with in situ spacecraft observations, but single-spacecraft techniques such as the partial variance of increments (PVI) are inherently limited since they lack spatial context. A combined analysis of in situ observations and numerical simulations can provide significant insight into the properties of intermittent structures forming in heliospheric turbulence. Understanding the size and distribution of these structures is crucial in tracing the pathways of energy dissipation and particle energization in space plasma. Using 3D fully kinetic simulations of magnetized turbulence, we identify CS via machine learning and find a complex broken-power-law distribution for the CS widths, where the power-law breaks separate ion-scale CS from electron-scale CS. Electron-scale CS dominate, with widths peaking near $2d_e$. Comparing simulations with MMS data, we test PVI as a CS detector and show it can infer CS scale, though oblique crossings inflate inferred sizes. The prevalence of electron-scale sheets suggests they may contribute to plasma heating in aggregate.
Read the full abstract

All authors Zachary Davis, Alexandros Chasepis, Colby Haggerty, Luca Comisso, Derek Sikorski

Solar and Stellar Astrophysics

Magnetic pressure anisotropy in ultra-dense white dwarfs: Landau quantization and neutronization effects

Edson Otoniel, Juan M. Z. Pretel, Victor B. T. Alves et al. (+2 more)

Strong magnetic fields modify the thermodynamics of white dwarf (WD) matter by quantizing the transverse motion of degenerate electrons into Landau levels and splitting the pressure into components parallel and perpendicular to the magnetic field. We investigate how this microscopic pressure anisotropy affects ultra-dense WD sequences when Coulomb lattice contributions, electron capture thresholds, neutron drip limits, and nuclear composition are treated consistently in the equation of state (EoS). The stellar equilibrium structure is obtained by solving an anisotropic extension of the Tolman–Oppenheimer–Volkoff (TOV) equations, where $P_r = P_\parallel$ and $P_t = P_\perp$ denote the radial and tangential pressures, respectively. We compare the post-electron-capture branches with their corresponding pre-capture sequences for pure $^{12}\rm{C}$, $^{16}\rm{O}$, $^{20}\rm{Ne}$, and $^{24}\rm{Mg}$ compositions, as well as for fixed 50/50 C/O, Ne/O, and Mg/Ne mixtures. The EoS predicts $P_\perp < P_\parallel$ in density ranges where only a few Landau levels are occupied. Consequently, pressure anisotropy shifts the stellar sequences toward smaller radii, with only minor changes in the maximum masses. We also find that post-capture configurations cannot be interpreted from the mass–radius plane alone, since the corresponding $M(\rho_c)$ curves reveal unstable portions after the maximum mass is reached. Our results show that strong magnetic fields significantly reduce the radii of low-mass WDs, yielding better agreement with the observational data available in the Montreal White Dwarf Database and suggesting that future high-precision observations of massive magnetic WDs could help assess the role of magnetic pressure anisotropy in determining their masses and radii.
Read the full abstract

All authors Edson Otoniel, Juan M. Z. Pretel, Victor B. T. Alves, César O. V. Flores, Clésio E. Mota

Astrophysics of Galaxies

Radiation-Driven Evolution and Gas Kinematics of the Bright-Rimmed Cloud SFO 25

Puja Porel, Archana Soam, William D. Vacca et al. (+1 more)

Bright-rimmed clouds (BRCs) are valuable laboratories for investigating how ionizing radiation from massive stars reshapes molecular clouds and influences star formation. We present a kinematic and dynamical study of the BRC SFO 25 using archival JCMT-HARP observations of the $^{12}$CO, $^{13}$CO, and C$^{18}$O ($J = 3-2$) transitions at an angular resolution of about 14-15 arcsec (0.051-0.054 pc). Gaia parallaxes of young stellar objects associated with the cloud yield a revised distance placing SFO 25 behind the ionizing O7V star HD 47839, implying that ultraviolet radiation can directly affect both the head and tail. The molecular gas exhibits a pronounced head-tail velocity gradient, with the tail systematically redshifted relative to the head, inconsistent with the expectations of classical radiation-driven implosion (RDI) and suggestive of an evolved phase dominated by radiative dispersal and photoevaporation. The head is moderately denser than the tail, while a compact C$^{18}$O clump associated with IRAS 06382+1017 reaches densities of $10^4~\mathrm{cm}^{-3}$. Virial and energy analyses indicate that the head, tail, and dense clump are gravitationally unbound, with kinetic energy exceeding both the gravitational binding energy and the external ionized gas pressure. Class II young stellar object candidates identified in the tail demonstrate that star formation is not confined to the dense head. Although RDI may have triggered earlier star formation in the head, it cannot readily explain the activity observed in the tail, pointing to a more complex evolutionary history than predicted by the classical RDI scenario.
Read the full abstract

All authors Puja Porel, Archana Soam, William D. Vacca, Janik Karoly

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Fixing IR tail of gravitational waves from domain walls

Ivan Dankovsky and Dmitry Gorbunov

Numerical simulations of gravitational waves (GW) production during violent evolution of matter inhomogeneities in the early Universe yield highly wiggle infrared parts of the spectra. Obtained directly from the two-point correlation function, these wiggles are nonphysical, corresponding to the parasitic, double frequency terms in naively averaged squared oscillation amplitudes of GW, and hence must be washed out. The deep infrared behavior can be predicted on general grounds, e.g. fixed by causality considerations. However, what matters for real observations, e.g. like that of NANOGrav, and what can be only inferred from numerical simulations, is the infrared slope near the maximum of the spectrum. It reflects the dynamics responsible for the GW production in its heyday, and hence must be accurately predicted. We illustrate the problem with numerical simulations of the Domain Wall network performed with the help of code CosmoLattice. We suggest a numerical procedure to smooth out these parasitic wiggles, which allows us to recover the true spectrum. Being quite generic, it may be applied to numerical simulations of other hypothetical sources of GW possibly operating in the early Universe. The procedure requires to extend the simulation by a few Hubble times after termination of the GW production. We checked with numerical simulations, that the technically natural long-time extension of simulations, which becomes available via artificial scaling of different parts in the scalar sector equations provided by PRS prescription, gives wrong GW spectra even if the source terms are properly rescaled.
Read the full abstract

Solar and Stellar Astrophysics

Localized magnetic pressure anisotropy in strange dwarfs with crystalline crusts

Mila Leite Garcia Reis, Daniela Eller Uliana, Jaziel G. Coelho et al. (+1 more)

We study equilibrium sequences of magnetized strange dwarfs composed of a self bound MIT bag strange matter core, with \(B_{\rm bag}^{1/4}=145\,{\rm MeV}\), and an ordinary crystalline crust. The aim is to determine how nuclear composition changes and magnetic pressure anisotropy in the crust modify the mass radius relation. The strange core is kept isotropic, while the crust is described either by pure nuclei stopped at the first inverse beta threshold or by electron capture sequences extended to neutron drip for C, O, Ne, and Mg compositions; selected mixed crusts are also considered up to the first instability. The stellar structure is solved with the radial pressure as the integrated pressure and with the anisotropic contribution \(2(P_t-P_r)/r\) restricted to the crust. This treatment is compared with ordinary white dwarf sequences and with scalar pressure branch calculations. We find that extending the crust to neutron drip produces more compact strange dwarf branches than stopping at the inverse beta threshold, because the evolved crust is softer and the core crust transition occurs at higher pressure. Magnetic anisotropy further shifts the selected branches toward smaller radii, with the effect visible across the compositions studied and clearer at fixed stellar mass. The comparison with compact objects from the Montreal White Dwarf Database is used only as an observational reference plane, but it indicates that compact white dwarf candidates are a relevant region for testing small core strange dwarf scenarios.
Read the full abstract

All authors Mila Leite Garcia Reis, Daniela Eller Uliana, Jaziel G. Coelho, Edson Otoniel

Astrophysics of Galaxies

Linking dynamics and chemistry in barred galaxies through action-space mapping

Tetsuro Asano, Victor P. Debattista and Michiko S. Fujii

We aim to extend the action-based framework, proposed by a previous study, for assigning chemical information to collisionless $N$-body simulations of barred galaxies, enabling more realistic comparisons with observations. We developed a new method to map chemistry of star-forming $N$-body+hydrodynamical simulations (donor models) onto pure $N$-body simulations (target models) using a matching algorithm. We applied the method to two barred $N$-body galaxies, one Milky Way (MW)-like with a classical bulge and another with a strongly buckled bar, combined with two star-forming donor models exhibiting bimodal and unimodal chemical tracks in the [Fe/H]-[$\alpha/$Fe] plane. Our models reproduce key chemo-dynamical trends observed in the MW and external galaxies. Metal-rich populations are more strongly associated with the X-shaped bulge morphology, leading to vertically pinched metallicity maps consistent with observations and chemo-hydrodynamical simulations. The [Fe/H]-[O/Fe] distributions show latitude-dependent bimodality, and the mock magnitude distributions of red clump stars reveal a stronger X-shape for metal-rich populations. In the model with a classical bulge, metal-poor stars exhibit a more spherical morphology on the longitude-latitude plane, while metal-rich stars show a boxy distribution, consistent with observations of the MW bulge. The proposed action-based chemical assignment provides a computationally efficient and flexible approach to link the dynamical and chemical evolution of barred galaxies. It enables realistic chemo-dynamical modelling of the galactic bulges.
Read the full abstract