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Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 21 February

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

Dark Glueball Direct Detection

Ji-Wei Li, Roman Pasechnik, Wei Wang et al. (+1 more)

We consider glueball dark matter (DM) in a Yang-Mills dark sector confined at $\Lambda_D$ scale and coupled to the Standard Model through electrically and dark-color charged vector-like fermion portals, with the mass scale $m_\psi$. In a simple case with two lightest mass-degenerate vector-like fermions with opposite electric charges the effective amplitudes with one $C$-odd glueball (oddball) and odd number of photons vanish, rendering the lightest $C$-odd spin-1 state with mass $m_\chi$ a viable DM candidate provided that $m_\psi\gtrsim 5.5 \Lambda_D$. We develop a controlled effective field theory framework with non-perturbative information supported by QCD phenomenology leading to a quantitative prediction for coherent elastic glueball scattering off nuclei. We find a steep scaling of the spin-independent cross section $\sigma_{\rm SI}\propto \Lambda_D^{2.15} m_\psi^{-8}$. This implies that the sensitivity of the current and next-generation xenon experiments in the range of $\sigma_{\rm SI} \sim 10^{-46} - 10^{-48}$ cm$^2$ corresponds to $m_\psi \simeq 3-30$ GeV, respectively, for $\Lambda_D\simeq 0.55-5.5$ GeV. We provide a minimal UV completion of the portal sector compatible with collider phenomenology. Our results pave a quantitative foundation for testing glueball DM in direct-detection experiments.
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All authors Ji-Wei Li, Roman Pasechnik, Wei Wang, Zhi-Wei Wang

High Energy Astrophysical Phenomena

Diverse properties of electron Forbush decreases revealed by the Dark Matter Particle Explorer

F. Alemanno, Q. An, P. Azzarello et al. (+147 more)

The Forbush decrease (FD) of cosmic rays is an important probe of the interplanetary environment disturbed by solar activities. In this work, we study the properties of 8 FDs electrons (including positrons) between 2 GeV and 20 GeV from January, 2016 to March, 2024, with the Dark Matter Particle Explorer. The maximum decrease amplitudes of these events are about 30% - 15%, and the amplitudes reduce with energy. The recovery time of these events shows diverse behaviors of their energy-dependence. Some of them show strong energy-dependence, while some have a nearly constant recovery time. It has been shown that such diverse behaviors could be related with the geometry of the disturbed regions of the interplanetary space by coronal mass ejections (CME), represented by the combined effect of the CME velocity, angular spread, and ejection direction.
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All authors F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong, G. Donvito, J. L. Duan, K. K. Duan, R. R. Fan, Y. Z. Fan, F. Fang, K. Fang, C. Q. Feng, L. Feng, S. Fogliacco, J. M. Frieden, P. Fusco, M. Gao, F. Gargano, E. Ghose, K. Gong, Y. Z. Gong, D. Y. Guo, J. H. Guo, S. X. Han, Y. M. Hu, G. S. Huang, X. Y. Huang, Y. Y. Huang, M. Ionica, L. Y. Jiang, W. Jiang, Y. Z. Jiang, J. Kong, A. Kotenko, D. Kyratzis, S. J. Lei, B. Li, M. B. Li, W. H. Li, W. L. Li, X. Li, X. Q. Li, Y. M. Liang, C. M. Liu, H. Liu, J. Liu, S. B. Liu, Y. Liu, F. Loparco, M. Ma, P. X. Ma, T. Ma, X. Y. Ma, G. Marsella, M. N. Mazziotta, D. Mo, Y. Nie, X. Y. Niu, A. Parenti, W. X. Peng, X. Y. Peng, C. Perrina, E. Putti-Garcia, R. Qiao, J. N. Rao, Y. Rong, R. Sarkar, P. Savina, A. Serpolla, Z. Shangguan, W. H. Shen, Z. Q. Shen, Z. T. Shen, L. Silveri, J. X. Song, M. Stolpovskiy, H. Su, M. Su, H. R. Sun, Z. Y. Sun, A. Surdo, X. J. Teng, A. Tykhonov, G. F. Wang, J. Z. Wang, L. G. Wang, S. Wang, X. L. Wang, Y. F. Wang, D. M. Wei, J. J. Wei, Y. F. Wei, D. Wu, J. Wu, S. S. Wu, X. Wu, Z. Q. Xia, Z. Xiong, E. H. Xu, H. T. Xu, J. Xu, Z. H. Xu, Z. L. Xu, Z. Z. Xu, G. F. Xue, M. Y. Yan, H. B. Yang, P. Yang, Y. Q. Yang, H. J. Yao, Y. H. Yu, Q. Yuan, C. Yue, J. J. Zang, S. X. Zhang, W. Z. Zhang, Yan Zhang, Yi Zhang, Y. J. Zhang, Y. L. Zhang, Y. P. Zhang, Y. Q. Zhang, Z. Zhang, Z. Y. Zhang, C. Zhao, H. Y. Zhao, X. F. Zhao, C. Y. Zhou, X. Zhu, Y. Zhu, X. Luo

Astrophysics of Galaxies

Massive Black Hole formation in proto-stellar clusters via early gas accretion

Zacharias Roupas

We review our semi-analytic model of stellar black hole (BH) mass growth by gas accretion in gas-rich stellar clusters during their birthstage within the first $\sim 10\,{\rm Myr}$ after the first stellar formation event. Such proto-stellar clusters are massive and compact, with typical masses $\sim 10^6\,{\rm M}_\odot$ and sizes $\sim 1\,{\rm pc}$, suggested by recent James Webb Space Telescope (JWST) observations. We find that the BH masses are shifted by the end of gas depletion to values within and above the BH mass gap, well within the range of components of the recent gravitational-wave (GW) signal GW231123, and up to masses $\sim 10^3\,{\rm M}_\odot$.
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Astrophysics of Galaxies

Assessing Zeeman Measurements of Magnetic Fields in Synthetic HI Observations

Duo Xu, Peter Martin, Stella Offner et al. (+3 more)

Zeeman observations provide the only direct probe of line-of-sight (LOS) magnetic fields in the interstellar medium. To evaluate their accuracy and limitations, we generate synthetic HI Zeeman spectra from magnetohydrodynamic simulations and idealized cloud models, and analyze the resulting Stokes I and V profiles using two complementary methods. Approach I uses the classical relation between Stokes V and dI/d{\nu} to estimate LOS-averaged magnetic fields, achieving an upper-limit relative error of 16% (half-width of 68.27% confidence interval) for a representative noise level of 0.014 K. Approach II applies Gaussian decomposition to Stokes I and V to estimate component-level magnetic fields, yielding a 13% relative error quantifying the same confidence range, reflecting the intrinsic uncertainty of such Zeeman estimates. Both approaches recover the original fields under uniform-field conditions and remain robust in turbulent environments. Approach I provides a simple and reliable LOS-averaged field estimate, while Approach II, although more complex, offers statistical insight into magnetic field variations along the LOS. We further show that joint fitting of Stokes I and V generally outperforms sequential fitting, particularly in the presence of attenuation. Increasing noise eight-fold produces a more modest rise in uncertainty, doubling to a 26% relative error, while substantial optical depth introduces only a minor additional contribution to the overall uncertainty. Applying these methods to FAST observations of the L1544 star-forming region, we confirm the previously reported LOS magnetic field strength, demonstrating the validity of Zeeman analysis in this benchmark core.
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All authors Duo Xu, Peter Martin, Stella Offner, Robert Gutermuth, Michael Grudic, Joshua Speagle

Solar and Stellar Astrophysics

Fast reconnection in a coronal torn plasma sheet

Zehao Tang

Tearing instability, also known as plasmoid instability, is an effective mechanism to speed up magnetic reconnection process, working in a wide range of magnetized plasma systems with different spatial scales, ionization degrees, and collisionality. However, due to observational limitations, observations of {plasma sheet} tearing and the resulting plasmoids are rather scarce. This scarcity significantly hinders our understanding of the role of plasmoids in the reconnection process from an observational perspective. Using high-spatiotemporal multiwavelength observations from the Solar Dynamics Observatory, we traced the entire evolution of a coronal {plasma sheet}. Its formation was driven by the emergence of photospheric magnetic flux, followed by tearing, and eventual decay. The evolution of the {plasma sheet} exhibited two distinct stages. Initially, it rose rapidly, lengthened, and underwent tearing at a low frequency. Subsequently, its ascent slowed, it began to shorten, and the tearing occurred more frequently. Detailed analysis of the reconnecting {plasma sheet} focuses on heating, plasmoid dynamics (formation and ejection), and the resulting reconnection rate change. Two key heating processes are identified: {plasma sheet} tearing and coalescence involving plasmoids and magnetic cusps. More importantly, combining observations with analytical studies suggests that plasmoids are key carriers of magnetic flux fast transferring in the observed torn {plasma sheet}, and their formation and ejection significantly enhance the reconnection rate and facilitate the onset of fast reconnection.
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High Energy Astrophysical Phenomena

Accretion disks in (repeating) partial tidal disruption events: rapid state transitions, UV plateaus and flares from disk-remnant collisions

Andrew Mummery

Tidal disruption events which repeat on timescales of months-to-years represent an unambiguous signature of a partial disruption, with the surviving stellar remnant returning to pericentre to be repeatedly stripped by tidal forces. These systems therefore offer the best laboratories to study the differences between partial and full disruptions. One noteworthy observational difference between the two systems is that all known X-ray bright repeating TDEs show rapid transitions between thermal, non-thermal and completely dim states on timescales much shorter than full (non-repeating) TDEs. We argue this can be simply understood as being due to the reduction in fuel supply available to the disk, and that these systems provide evidence that all tidal disruption events undergo a state transition at Eddington ratios $f_{\rm edd} = L_{\rm bol}/L_{\rm edd} \sim 0.01$, similar to X-ray binaries. {As part of this calculation we derive a general expression for the time taken for a TDE disk to fall to a given Eddington fraction, which will be of use to both full and partial TDE science.} Perhaps surprisingly, the late-time optical/UV plateau luminosity observed from these systems is largely unaffected by this reduction in fuel supply, provided the outer disk remains in a thermal state for long enough for this emission to be detected. We then show that collisions between the returning stellar remnant and the disk formed from the last passage will produce potentially observable X-ray flares ($L_{\rm flare} \simeq 10^{42}$ erg/s), but that they are likely to be very difficult to detect as they are generally short-lived ($t_{\rm flare} \simeq 0.1-1$ hr).
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Friday 20 February

Solar and Stellar Astrophysics

Solar cycle irregularity study

William A. Gardner and Antonio Napolitano

It has recently been discovered that the time phases (time-varying delays) of the irregular periodicities observed in the Sunspot series, consisting of the approximate 27-day latitude-averaged plasma rotation and approximate 11-yr magnetic pole reversal, share a common pattern or cycle of irregularity. Because the method of measurement contains an unknown constant delay of no practical significance, the average of the measured cycle of delay is subtracted out, and the resultant cycle proceeds from zero delay to maximum delay, back to zero delay, then to maximum advance, and finally back to zero advance/delay. The period of this cycle is estimated to be 164 years, which does not allow for even one full repetition of the pattern in the 205-yr data record. So, it may or may not be a segment of an ongoing (pseudo) periodicity. Nevertheless, the fact that this cycle of irregularity in period is shared by two long-recognized genuine irregular periodicities tied to specific activity from two distinct solar phenomena suggests there is a common phenomenon affecting these periodicities. The physics-based link between the rotation speed of the interior of the Sun and the average over latitude of the rotation period of the surface plasma, approximately 27 days on average, suggests the possibility that there may be a single primary phenomenon that is responsible for irregularity of both rotation of the interior of the Sun and the period, approximately 11 yrs on average, of pole-reversal. This is consistent with recently reported (November 2025) results on hypothesized planetary forcing of the Solar dynamo.
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Solar and Stellar Astrophysics

The Physics of Solar Energetic Particles

Donald V Reames

Solar energetic particles (SEPs) are produced in two fundamental ways: at magnetic reconnection sites in solar jets and at collisionless shock waves driven by fast coronal mass ejections (CMEs). "Impulsive" SEP events, on open field lines from jets, have signature abundance enhancements of 3He and of increasingly heavy elements, and their outward streaming electrons drive type-III radio bursts. Similar acceleration for particles trapped on closed loops energizes solar flares. In contrast, fast, wide, CME-driven shocks accelerate seed ions from the ambient corona that grow resonant Alfven waves as they stream outward. These waves can scatter and trap lower-rigidity ions near the shock, limiting outflow, and flattening low-energy spectra upstream at the "streaming limit." Downstream, a spatially-uniform "reservoir" of SEPs is shed by the expanding shock between it and the Sun. These trapped invariant SEP spectra decrease in intensity adiabatically as the volume of the reservoir expands. Ions from the reservoir can seed further acceleration in multi-shock event and energetic proton precipitation can prolong solar gamma-ray emission. Shocks are often additionally seeded by residual impulsive ions which dominate the SEP heavy-ion abundances with their signature enhancements. As samples of the corona, SEP abundances also probe differences with the photosphere that depend upon the first ionization potential (FIP) of the elements.
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Cosmology and Nongalactic Astrophysics

One Halo, Two Boundaries: Relating Accretion Shocks and Splashback Radii in Galaxy Clusters

Siddhant Sen, Susmita Adhikari, Daisuke Nagai et al. (+1 more)

The boundaries of dark matter and gas in clusters are delineated by the splashback radius and the accretion shock, respectively. Theoretically, both of these boundaries are expected to coincide at the outskirts of halos. However, hydrodynamic cosmological simulations have highlighted significant displacement between them. In this study, we utilise the IllustrisTNG simulation suite to investigate the statistical relationship between the splashback and shock surfaces in a sample of 812 cluster-mass halos. We compute the full angular distribution of both boundaries and examine their relationship, also considering how different moments of this distribution correlate with halo properties. We employ a dispersion-based measure for the splashback boundary and the maximum entropy distance for the shock location. Despite examining various boundary definitions, we consistently observe an offset between the splashback and shock boundaries, with $R_{\rm sh}/R_{\rm sp} \sim 1.3-2$, depending on specific methodological choices. This offset predominantly occurs along void directions. We analyse the redshift evolution of these boundaries for a subset of halos and find that splashback and shock boundaries are not necessarily distinct at earlier times. During mergers, gas dissipates energy and resists contraction via pressure, unlike collisionless dark matter, leading to the observed boundary offset. We also find that the feature in pressure profiles arising from the outer accretion shock is sensitive to the exact method of stacking, which has important implications for observations.
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All authors Siddhant Sen, Susmita Adhikari, Daisuke Nagai, Benedikt Diemer

Instrumentation and Methods for Astrophysics

The Impact of Degraded Charge Transfer Efficiency on Extended Sources in ACS/WFC

David V. Stark, M. Chiaberge and N. A. Grogin

Using repeat imaging of a galaxy cluster taken over a seventeen-year baseline, we examine the impact that degraded Charge Transfer Efficiency (CTE) has on photometric measurements of extended sources using the ACS/WFC on HST. We examine how measured brightnesses depend on time since ACS installation, source location on the WFC detectors, source brightness, and local background level in individual exposures. We find that global brightness measurements using large apertures are generally reliable within $\sim$0.05 magnitudes across the WFC detectors if exposure backgrounds are above $20e^-/{pixel}$ and sources are brighter than $\sim300e^-$ in a single exposure. However, brightness measurements on smaller scales can suffer deficiencies in excess of 0.1 mags (sometimes, significantly more) in recent data unless sources are very close to the CCD serial registers ($\lesssim 512$ pixels), or brighter than $\sim3000\,e^-$ in a single exposure. We also show how degraded CTE can result in artificial asymmetries in galaxy light distributions, which are largely mitigated if backgrounds are $>20e^-/{pixel}$ and targets are not far ($>1536$ pixels) from the serial registers. As expected, brightness measurements in later epoch data are best when using CTE-corrected images (FLC/DRC), but our results imply that the pixel-based CTE correction algorithm employed by the ACS reduction pipeline does not necessarily place charge back into its original location within extended sources. Based on this study, users are advised to keep backgrounds above the already recommended $30e^-/\mathrm{pixel}$, ensure targets will have at least $\sim 300e^-$ in a single exposure, and place targets close to the serial registers if analysis of their spatially resolved properties is needed.
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Solar and Stellar Astrophysics

Magnetic structure of coronal dark halos

J. D. Nölke, S. K. Solanki, J. Hirzberger et al. (+5 more)

At low coronal temperatures around or below 1 MK distinct areas in the surroundings of active regions (AR) show emission at a level significantly below the emission coming from the quiet Sun (QS). These areas are referred to as dark halos, dark canopies, or dark moats. To better understand the nature of dark halos we study the connection between the photospheric magnetic field and coronal emission at different temperatures. Combining Solar Orbiter data from the high-resolution Polarimetric and Helioseismic Imager (SO/PHI) and Extreme Ultraviolet Imager (EUI) instruments allows us to identify these areas that are dark in the extreme ultraviolet (EUV) in the immediate vicinity of an AR. We probe both the photospheric magnetic field as well as the coronal intensities as a function of distance to the AR NOAA 12893. The dark halo has an unsigned magnetic flux density similar to the QS, but shows a strong radial dependence with distance from the AR centre. It drops by 38 % from 6.1 G at the inner boundary to 3.8 G at the outer, shifting from above to below QS levels. Coronal emission $\leq$1 MK is $\sim$40 % below QS and shows no dependence on distance to the AR centre. In contrast, at $\geq$1.6 MK, emission exceeds QS levels, but declines outward toward QS values. A few hot loops extend from the AR periphery across the halo, while at lower temperatures no such loops appear and short loops dominate the corona. The reduced unsigned magnetic flux density in the outermost parts of the dark halo, below QS level, suggests that reduced coronal heating due to weak underlying magnetic flux heating could be partially responsible for the reduced emission around 1 MK. Closer to the AR, other mechanisms might lead to reduced heating. The different loops structures detected for hotter and cooler coronal temperatures likely play a crucial role in understanding coronal dark halos.
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All authors J. D. Nölke, S. K. Solanki, J. Hirzberger, H. Peter, L. P. Chitta, K. H. Glassmeier, D. Calchetti, G. Valori

Solar and Stellar Astrophysics

The 2021 Hot-type Symbiotic Outburst of YY Herculis: An Optical Follow-up Study

L. S. Sonith and U. S. Kamath

We have followed up on the hot-type classical symbiotic outburst reported in YY Her using the Himalayan Chandra telescope. The outburst coincides with the secondary minima of the system. Approximately 12 similar brightening events have been reported between 1890 and 2020, with only the 1993 outburst being studied spectroscopically. In our study, we monitored the system from 2021 to 2023, covering $\sim$1.5 orbital cycles, providing an opportunity to understand the spectral evolution of the outburst over a complete orbital period of YY Her. We found that the temperature and luminosity estimations based on emission line fluxes exhibit orbital phase dependence. The values estimated at phase 0.5, corresponding to the secondary minimum, were the most reliable. The temperature of the hot component is $\approx 1.41 \times 10^5 \, \text{K}$, and the luminosity is $\approx 1020 \, L_{\odot}$ during the outburst, reduced to $\approx 1.3 \times 10^5 \, \text{K}$ and $\approx 830 \, L_{\odot}$ after one orbital cycle at phase 0.5. Temperature estimations during the outbursts suggest that YY Her exhibits both hot-type (2021) and cool-type (1993) behavior, similar to another symbiotic star, AG Dra. Using variations of the Ca II absorption lines, we confirmed the contribution of the ellipsoidal effect in secondary minima in the YY Her light curve.
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Earth and Planetary Astrophysics

The impact of electron precipitation on Earth's thermospheric NO production and the drag of LEO satellites

M. Scherf, S. Krauss, G. Tsurikov et al. (+6 more)

We investigate the response of space weather events on Earth's upper atmosphere over the polar regions by studying their effect on the drag of the CHAMP and GRACE satellites. Increasing solar activity that results in heating and the expansion of the upper atmosphere threatens low Earth orbit (LEO) satellites. Auroral events are closely related to the stellar energy deposition of solar EUV radiation and precipitating energetic electrons, which influence photochemical processes such as the production of nitric oxide (NO) in the upper atmosphere. To study the production of NO molecules and their influence on the thermospheric structure and satellite drag, we first model Earth's background thermosphere with the 1D upper atmosphere model Kompot by considering the incident X-ray, EUV, and IR radiation during selected space weather events. To investigate the effect of electron precipitation in the production of NO molecules in the polar thermosphere, we apply a Monte Carlo model accounting for the stochastic nature of collisional scattering of auroral electrons in collisions with the surrounding N$_2$-O$_2$ atmosphere, including the production of suprathermal N atoms. The observed effect of the atmospheric drag on CHAMP and GRACE during the two studied events indicates that a sporadic enhancement of NO molecule production in the polar thermosphere and its IR-cooling capability, which counteracts thermospheric expansion and can lead to an “overcooling” with decreased density after the space weather event, can have a protective effect on LEO satellites. Their production efficiency, however, is highly dependent on the energy flux of the precipitating electrons. Our results have direct implications for empirical satellite orbit prediction models, as our simulations highlight the need to consider precipitation-induced NO production to improve the predictive power of these models.
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All authors M. Scherf, S. Krauss, G. Tsurikov, A. Strasser, V. Shematovich, D. Bisikalo, H. Lammer, M. Güdel, C. Möstl

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

Scaling solutions for varying tension strings

C. S. C. M. Coelho, A.-L. Y. Gschrey and C. J. A. P. Martins

We use the Velocity-dependent One Scale Model for topological defect evolution to explore and classify the possible scaling solutions for string networks with time-varying tension, in cosmological and non-cosmological settings and under two different phenomenological assumptions for the behavior of these variations, which rely on different stretching and damping contributions to the string dynamics. We discuss how these assumptions impact the standard scaling solutions, as well as the evolution of the string network density. In addition to simple power-law cosmological epochs solutions, we also discuss the behavior of the network during the radiation-to-matter and matter-to-acceleration transitions. Overall, our results show that for the same amount of tension variation, a change in the stretching length scale tends to have a more significant impact on the network than a change in the damping length.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Cosmological Constraints on Long-Lived Particles Using Dimension-Six Effective Operators

Mickael V. S. de Farias, Rodrigo Holanda, Matheus M. A. Paixao et al. (+2 more)

Long-lived particles (LLPs) provide an interesting window into physics beyond the Standard Model, offering characteristic signatures at colliders and in cosmology. In this work, we investigate LLPs decays into dark matter. If the lifetime of LLPs are longer than $10^4$ s, the decay products can disrupt the synthesis of light nuclei in the early universe and alter Big Bang Nucleosynthesis (BBN) predictions. If the LLP is much heavier than the dark matter particle, the decay contributes to the number of effective neutrino species, $N_{eff}$. We describe these decays via dimension-six effective operators and outline the parameter space in which such decays obey cosmological bounds stemming from BBN, structure formation, Cosmic Microwave Background, and Baryon Acoustic Oscillation data.
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All authors Mickael V. S. de Farias, Rodrigo Holanda, Matheus M. A. Paixao, Farinaldo S. Queiroz, Priscila V. dos Santos

Solar and Stellar Astrophysics

Abundance Calculations of Neon Isotopes in the Predicted Lifetime of the Sun

Mohamed A. Alkhajeh, Mashhoor A. Al-Wardat, Awni M. Kasawneh et al. (+1 more)

The elemental abundances of neon isotopes provide valuable insights into stellar evolution and nucleosynthesis. In this study, we calculate the abundances of the isotopes 18Ne, 19Ne, 20Ne, 21Ne, and 22Ne across the five principal evolutionary phases of the Sun: hydrogen burning, lively old age, onset of rapid growth and red giant, helium burning and helium exhaustion. The calculations were carried out using the open-source nucnet-tools package, developed by the Webnucleo Group at Clemson University. Initial isotope abundances were adopted from standard proto-solar compositions. Their evolution was computed under static hydrostatic burning conditions, assuming constant temperature and density within each phase. The results show that the stable isotopes 20Ne and 22Ne remain dominant throughout the Sun's lifetime, whereas the short-lived isotopes 18Ne and 19Ne decay rapidly during or shortly after the hydrogen-burning phase. The predictions obtained for the helium burning and exhaustion phases provide quantitative neon-isotope abundances that are not extensively reported in the existing literature. These results offer valuable reference values for future studies of solar and stellar evolution, nucleosynthetic pathways, and isotopic modeling.
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All authors Mohamed A. Alkhajeh, Mashhoor A. Al-Wardat, Awni M. Kasawneh, Mohammed H. Talafha

Earth and Planetary Astrophysics

A dedicated survey of fast-rotating near-Earth asteroids with the Two-meter Twin Telescope. I. Observational strategy and first results

Miguel R. Alarcon, Javier Licandro and Miquel Serra-Ricart

The rotational properties of small near-Earth asteroids (NEAs) provide crucial insights into their internal structure and collisional history. However, systematic surveys targeting metre- to decametre-sized bodies are rare, thus leaving their spin distribution poorly constrained. Our aim was to quantify the prevalence of fast rotation and characterise the spin-rate distribution of small NEAs to constrain their internal strength and evolution. We conducted a dedicated high-cadence photometric survey of 249 NEAs using the Two-meter Twin Telescope (TTT). Rotation periods and amplitudes were derived from dense time series to classify objects as fast or non-fast rotators. We determined the rotation period of 156 new fast rotators (P < 2.2 h), including 87 that rotate faster than 10 min. The prevalence of fast rotators increases with absolute magnitude: from 60.6-80.3 % for 22 < H < 24 to 77.3-89.4 % for 24 < H < 26 and 94.1-96.1 % for H > 26, indicating that fast rotation dominates in the small NEA population. Most objects spin faster than the gravity-defined limit; 98 targets require cohesive strengths exceeding that of weak rubble piles, and 22 are compatible only with compact, high-strength interiors. This is the first systematic survey targeting the rotation of such small NEAs, providing the largest homogeneous sample of fast rotators obtained by a single campaign. Our findings demonstrate that fast rotation is the norm for objects smaller than tens of metres, implying that modest cohesive strength is required to prevent their rotational disruption.
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High Energy Astrophysical Phenomena

Inferring the population properties of galactic binaries from LISA's stochastic foreground

Federico De Santi, Alessandro Santini, Alexandre Toubiana et al. (+2 more)

Galactic binaries are expected to be the most numerous LISA sources and to produce a stochastic gravitational-wave foreground whose spectral shape encodes information about the underlying population. Extracting this information with standard hierarchical methods is challenging due to the high dimensionality of the problem and the computational cost of global-fit analyses. We present a simulation-based inference framework to measure the population properties of galactic binaries directly from the reconstructed foreground. Adopting an astrophysically agnostic parametrization in the observable space – defined by signal amplitude, frequency, and frequency derivative – we generate synthetic catalogs and foreground spectra using a global-fit-inspired subtraction algorithm. We then train a neural posterior estimator to map spectra to population parameters. We validate our method on simulated data and recover population parameters with good accuracy, including the total number of binaries. As a by-product, we present a GPU-accelerated version of the subtraction algorithm, which delivers a ~100X speed-up compared to previous implementations in the literature. Our results demonstrate that LISA's stochastic foreground alone carries significant information about the Galactic binary population and provide a practical step toward joint inference from resolved and unresolved sources.
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All authors Federico De Santi, Alessandro Santini, Alexandre Toubiana, Nikolaos Karnesis, Davide Gerosa

Astrophysics of Galaxies

The ionised interstellar medium of DSFGs revealed by JWST/NIRSpec and ALMA: Super-solar metallicity, low ionisation parameters and, typical electron densities

Steven Gillman, Kei Ito, Francesco Valentino et al. (+24 more)

We present a detailed study of near-infrared (2-4$\rm \mu$m) JWST/NIRSpec spectra of 48 high-redshift ($z=2.53^{+1.32}_{-0.70}$) galaxies detected with ALMA at $>3\sigma$. From a multi-wavelength SED analysis we establish the sample has a a median stellar mass of $\rm\log_{10}(M_\ast/M_\odot)=10.8\pm0.1$ and dust mass of $\rm\log_{10}(M_{\rm d}/M_\odot)=8.7\pm0.1$, covering a broad range of far-infrared luminosity $\rm (\log_{10}(L_{FIR}/L_\odot)=10.9-12.7)$. The majority of sources show no signs of AGN activity, with 40% having either X-ray counterparts $(\rm L_{Xc}>10^{42}erg/s)$, elevated optical line ratios, or broad (FWHM>800 km/s) H$\alpha$ profiles, although we note this is a lower limit due to the stochastic placement of NIRSpec slits. We establish the sample has a median gas-phase metallicity of $12+\log({\rm O/H})=8.71\pm0.02$, as derived from the [NII]/H$\alpha$ ratio, with the most FIR-luminous galaxies ($\rm\log_{10}(L_{\rm FIR}/L_\odot)>12$) falling $0.15\pm0.03$dex above the fundamental metallicity relation. From the [SII] emission-line doublet ratio, we measure a median electron density of $\log_{10}(n_{\rm e}/{\rm cm}^{-3})=2.53\pm0.07$ consistent with less-massive, star-forming, galaxies at the same epoch. For nine galaxies with [OII] and H$\beta$ detections (median $\rm\log_{10}(L_{\rm FIR}/L_\odot)=11.81\pm0.15$), we derive a median observed (dust-uncorrected) ionisation parameter of $\rm\log_{10}(U)=-2.84\pm0.06$. Our results indicate that luminous far-infrared galaxies are massive, chemically evolved systems that appear to deviate from the standard dust and metal production equilibrium observed in less obscured galaxies. This study demonstrates the synergy of JWST and ALMA in unveiling the nature of DSFGs, and highlights the need for a NIRSpec survey of uniformly selected, massive, dust-obscured, galaxies to fully characterise their interstellar medium.
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All authors Steven Gillman, Kei Ito, Francesco Valentino, Gabe Brammer, Pablo Araya Araya, Georgios Magdis, Ugnė Dudzevičiūtė, Aswin P. Vijayan, Minju Lee, Bitten Gullberg, Daniel Ceverino, Andreas L. Faisst, Seiji Fujimoto, Thomas R. Greve, Rashmi Gottumukkala, Chandana Chandrashekhar, Michaela Hirschmann, Shuowen Jin, Christian Kragh Jespersen, Takumi Kakimoto, Mariko Kubo, Peter Laursen, Masato Onodera, Antonio Pensabene, Francesca Rizzo, John R. Weaver, Po-Feng Wu

Astrophysics of Galaxies

Blue Monsters and Dusty Descendants: Reconciling UV and IR Emission from Galaxies from z=7, up to z= 14

Laura Sommovigo, Lachlan Lancaster, Shyam H. Menon et al. (+3 more)

Recent JWST observations reveal massive, UV-bright galaxies at $z > 10$ with little apparent dust attenuation, whereas ALMA detections at $z \simeq 7$ show similarly massive systems that are already dust-rich and IR-luminous. This raises a fundamental question: can a single physical model of star formation and dust production explain both populations across cosmic time? We address this using a minimal framework with only two free parameters–the instantaneous star formation efficiency ($\epsilon_\star$) and the dust yield per Type II supernova ($y_d$)–and predict the rest-frame UV and IR luminosity functions (LFs) from $z \simeq 14$ to 7. For a uniform ISM, we find a UV-IR tension at the bright end of the LFs at $z \ge 7$. The UV LF requires low dust yields ($y_d \lesssim 0.01\,M_\odot$), whereas the $z=7$ IR LF requires higher yields ($y_d \sim 0.1\,M_\odot$) unless the star formation efficiency is boosted above $\epsilon_\star \approx 5$-10%. We show that incorporating a porous, turbulent ISM largely resolves this tension: turbulence opens low-column-density sightlines that enhance the UV escape fraction while leaving the total absorbed energy–and thus the IR luminosity–nearly unchanged once radiative-transfer–induced flattening of the attenuation curve is included. Large-grain dust distributions, while reducing UV opacity, play a secondary role once ISM porosity and radiative transfer are taken into account. At $z > 10$, however, even strong turbulence cannot reproduce the bright end of the UV LF at high dust yield. This could be resolved either by efficient dust removal in early massive systems or by substantial ISM dust growth by $z \simeq 7$. Our results highlight dust physics as a key lever for interpreting the rapidly growing UV and IR constraints within the broader context of early galaxy formation.
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All authors Laura Sommovigo, Lachlan Lancaster, Shyam H. Menon, Joseph A. O'Leary, Rachel S. Somerville, Greg L. Bryan

Cosmology and Nongalactic Astrophysics

Reanalyzing DESI DR1: 5. Cosmological Constraints with Simulation-Based Priors

Anton Chudaykin, Mikhail M. Ivanov and Oliver H. E. Philcox

We analyze the public DESI full-shape clustering data using simulation-based priors (SBPs). Our priors are obtained by fitting normalizing flows to the distribution of EFT parameters measured from field-level simulations, themselves generated using tailored halo occupation distribution (HOD) models for each tracer. Incorporating SBPs in a power spectrum analysis significantly enhances $\Lambda$CDM cosmological parameter constraints; in combination with BAO information from DESI DR2 and a BBN prior on the baryon density, we find the matter density parameter $\Omega_m=0.2987\pm0.0066$, the Hubble constant $H_0=68.80\pm0.35\,\rm{km}\,\rm{s}^{-1}\rm{Mpc}^{-1}$, and the mass fluctuation amplitude $\sigma_8 = 0.766\pm0.015$ (or the lensing parameter $S_8=0.764\pm0.018$), which are $1\%$, $40\%$ and $50\%$ stronger than the baseline results, though with a notable downwards shift in $\sigma_8$, driven by the quasar HOD assumptions. The SBPs also have a significant impact in extended models, with the dark energy figure-of-merit improving by $70\%$ ($20\%$) in a $w_0w_a$CDM analysis when combining with the CMB (and supernovae). In the SBP analysis, we do not find statistically significant evidence for dynamical dark energy: the equation of state parameters are consistent with a cosmological constant within $2.2\sigma$ ($1.4\sigma$) in analyses without (with) supernovae. The neutrino mass constraints are also enhanced, with the $95\%$ limits $M_\nu<0.073\,\rm{eV}$ and $M_\nu<0.090\,\rm{eV}$ in $\Lambda$CDM and $w_0w_a$CDM respectively. The latter is the strongest constraint obtained to date and reinforces the preference for the normal neutrino mass hierarchy, regardless of the background dynamics. While our results are sensitive to HOD modeling assumptions, they clearly demonstrate that the inclusion of small-scale information can significantly sharpen cosmological parameter constraints.
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Earth and Planetary Astrophysics

POSEIDON I: The Dynamical Origins of Transiting Neptunes

Juan I. Espinoza-Retamal, Joshua N. Winn, Rafael Brahm et al. (+17 more)

We present the first results from the POSEIDON survey, aimed at constraining the dynamical origins of transiting Neptunes through stellar obliquity measurements. We report Rossiter-McLaughlin observations of two Neptunes, TOI-181 b and TOI-883 b, obtained with high-resolution spectroscopy from Magellan/PFS and WIYN/NEID. TOI-181 b is on a 4.5-day orbit with a sky-projected spin-orbit misalignment $\lambda = 32.0_{-6.5}^{+6.3}\,^{\circ}$ and a low eccentricity ($e<0.12$ with $2\sigma$ confidence). TOI-883 b has a longer orbital period of 10 days with $\lambda = 22_{-14}^{+15}\,^{\circ}$ and eccentricity $e = 0.16 \pm 0.03$. The significant misalignment of TOI-181 b and the significant eccentricity of TOI-883 b are suggestive of high-eccentricity migration for both systems. After adding these and other new measurements to the sample, we analyze the obliquity distribution of the host stars of transiting Neptunes. Earlier studies had suggested that the obliquity distribution is bimodal, with peaks corresponding to aligned orbits and polar orbits; the addition of more measurements has weakened the evidence for bimodality. The current sample appears to be consistent with a population of well-aligned systems and a smaller population with nearly random obliquities. This distribution resembles that observed for more massive planets, suggesting that transiting Jupiters and Neptunes originate from similar dynamical processes.
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All authors Juan I. Espinoza-Retamal, Joshua N. Winn, Rafael Brahm, Cristobal Petrovich, Gu{\dh}mundur Stefánsson, Hareesh Bhaskar, Elise Koo, Andrés Jordán, Marcelo Tala Pinto, Melissa J. Hobson, Hugo Veldhuis, Felipe I. Rojas, Johanna K. Teske, R. Paul Butler, Jeffrey D. Crane, Stephen Shectman, Shreyas Vissapragada, Gavin Boyle, Rodrigo Leiva, Vincent Suc

Astrophysics of Galaxies

The Chemical Homogeneity of Single-Lined Spectroscopic Binaries in Open Clusters

Amaya Sinha, Gail Zasowski, Natalie R. Myers et al. (+16 more)

Using SDSS-V DR19 Milky Way Mapper APOGEE data, we measure the impact that close binarity has on surface chemistry across the Hertzsprung-Russell diagram in a broad set of abundances by studying single-lined spectroscopic binaries (SB1s) in open clusters. We derive binary membership and orbital parameters for 103 SB1s by analysing APOGEE radial velocities with The Joker and UltraNest. We perform a detailed abundance analysis with BACCHUS to derive abundances in fourteen chemical species: Si, Fe, C, N, O, Na, Mg, Al, Ca, Ti, Cr, Ni, Ce, and Nd. Leveraging the assumptions of chemical homogeneity in open clusters, we compare the surface abundances of SB1s to non-binary stars at similar evolutionary states. We find that a subset of binaries with significant UV excess have a $\Delta$[C/N] that is 0.2–0.5 dex higher than expected, resulting in overestimated [C/N]-based ages for those stars. This points to pollution from an evolved companion and has implications for [C/N]-based age studies of the broader Milky Way. At the population level, we find that SB1s in our sample can be treated as statistically chemically homogeneous with their single-star counterparts, and we find no connection between orbital separation and chemical enrichment or depletion. We show that at separations up to ~5 pc, co-eval stars can be considered chemically homogeneous with one another within current abundance precisions, regardless of multiplicity.
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All authors Amaya Sinha, Gail Zasowski, Natalie R. Myers, Catherine Manea, Peter Frinchaboy, Katia Cunha, Johanna Müller-Horn, Yao-Yuan Mao, Aida Behmard, Joleen Carlberg, Julio Chanamé, Polly Frazer, Emily Griffith, Sarah Loebman, A. Roman-Lopes, Jonah Otto, Diogo Souto, Keivan Staussan, Guy S. Stringfellow

High Energy Astrophysical Phenomena

Chandra Proper Motions and Milliarcsecond Astrometry of Nineteen Pulsars

Jack T. Dinsmore and Roger W. Romani

We present X-ray proper motion (PM) measurements of 19 pulsars using new and archival data from the Chandra X-ray Observatory, including pulsar wind trails and X-ray filaments. Precise X-ray PMs are often limited by uncertainties in aligning observations to a common reference frame. Our analysis uses unresolved X-ray flux from stars in the Gaia catalog in addition to X-ray bright point sources for alignment, improving uncertainties. We obtain absolute positions referenced to Gaia with typical astrometric precision $\sim$10 mas and PM statistical uncertainties down to 1.3 mas yr$^{-1}$, the most precise X-ray PM achieved to date. With our improved frame alignment, PM accuracies are now limited by the pulsar flux in most cases. These results reveal a new X-ray filament and illuminate the wind nebula structures and origins of several of these pulsars.
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Astrophysics of Galaxies

Spatio-Spectroscopic Representation Learning using Unsupervised Convolutional Long-Short Term Memory Networks

Kameswara Bharadwaj Mantha, Lucy Fortson, Ramanakumar Sankar et al. (+8 more)

Integral Field Spectroscopy (IFS) surveys offer a unique new landscape in which to learn in both spatial and spectroscopic dimensions and could help uncover previously unknown insights into galaxy evolution. In this work, we demonstrate a new unsupervised deep learning framework using Convolutional Long-Short Term Memory Network Autoencoders to encode generalized feature representations across both spatial and spectroscopic dimensions spanning $19$ optical emission lines (3800A $< \lambda <$ 8000A) among a sample of $\sim 9000$ galaxies from the MaNGA IFS survey. As a demonstrative exercise, we assess our model on a sample of $290$ Active Galactic Nuclei (AGN) and highlight scientifically interesting characteristics of some highly anomalous AGN.
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All authors Kameswara Bharadwaj Mantha, Lucy Fortson, Ramanakumar Sankar, Claudia Scarlata, Chris Lintott, Sandor Kruk, Mike Walmsley, Hugh Dickinson, Karen Masters, Brooke Simmons, Rebecca Smethurst

2602.18426 · 20 Feb · This manuscript was previously submitted to ICML for peer review. Reviewers noted that while the underlying VAE-based architecture builds on established methods, its application to spatially-resolved IFS data is promising for unsupervised representation learning in astronomy. This version is released for community visibility. Reviewer decisions: Weak accept and Weak reject (Final: Reject)

Abstract PDF $GLXY ×2$MEM ×2$EVO ×1$GALAC ×1 +1

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

Detection prospects of solar $g$-modes with LISA

Aman Awasthi

The possibility of detecting solar oscillation modes using space-based gravitational-wave detectors has been investigated in the context of gravitational-wave interferometry, with Polnarev \cite{Polnarev:2009xf} demonstrating that low-frequency solar modes could, in principle, produce detectable signals in a LISA-type interferometer. Motivated by this work, I revisit the problem using current solar models, updated detector sensitivities, and improved theoretical and observational constraints on mode amplitudes. In this study, I compute the gravitational response of solar oscillation modes using standard solar models generated with MESA, and mode eigenfrequencies and eigenfunctions calculated with GYRE. I focus primarily on solar $g$ modes, evaluating their responses for degree $l=2$ and azimuthal orders $m=0$ and $m=2$. The analysis incorporates both the earlier proposed and the current updated LISA sensitivity curves, and I perform a comparative assessment with the TianQin mission in the relevant low-frequency band. To assess the robustness of the predicted signals, I estimate the gravitational responses using two different standard solar models based on the GS98 and AGSS09 abundance compilations. I find that the resulting signal responses are nearly identical for the two models, indicating that uncertainties in solar metallicity have a negligible impact on the detectability of solar $g$ modes by space-based interferometers.
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High Energy Astrophysical Phenomena

Numerical simulations of cold clumps in the hot accretion flows around black holes

Na-Duo Liu, Yu-Heng Sheng, De-Fu Bu et al. (+3 more)

Previous numerical simulations have shown that cold clumps can form within hot accretion flows, offering insights into the detailed processes of the state transition in black hole X-ray binaries. However, the evolution of the cold clumps has not been investigated in detail yet. In this paper, we conduct hydrodynamic simulations to investigate the evolution of the cold clumps. In addition to previous result that when the accretion rate is high enough the cold clumps emerge within the hot accretion flow, we found that instead of directly moving toward to the black hole, the clumps moves outward when they initially form. The reason should be the combination of viscous torque and the condensation of hot gas from larger radii, which lead to the slightly super-Keplerian angular momentum of the clumps. After reaching the equilibrium position, the clumps begin to fragment at the inner edge with each fragment moving inward sequentially. Generally, the azimuthal movement of the clumps are quasi-Keplerian, being closer to the outer detached Keplerian cold disk rather than the surrounding sub-Keplerian hot accretion flow, which agrees well with the semi-analytical results for weak coupling case in Wang et al. (2012).
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All authors Na-Duo Liu, Yu-Heng Sheng, De-Fu Bu, Xiao-Hong Yang, Mao-Chun Wu, Ren-Yi Ma

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

Constraining the $\Lambda\Lambda$ interaction with terrestrial and astronomical data

Yusuke Tanimura, Chang Ho Hyun and Myung-Ki Cheoun

Terrestrial double-$\Lambda$ hypernuclear data and astronomical observations of neutron stars provide complementary constraints on the $\Lambda\Lambda$ interaction. In this work, we investigate the $\Lambda\Lambda$ interaction within a Skyrme energy density functional framework based on the KIDS (Korea-IBS-Daegu-SKKU) models. We employ a Skyrme-type $\Lambda\Lambda$ interaction that includes the standard $s$- and $p$-wave terms, as well as a density-dependent term that effectively represents an $N\Lambda\Lambda$ three-body force. The $s$-wave terms are constrained using data on double-$\Lambda$ hypernuclei supplemented by pseudodata obtained from core + $2\Lambda$ three-body model calculations including heavier hypernuclei. We show that the data on heavier systems are essential to simultaneously constrain the two $s$-wave parameters. We further explore the impact of the $p$-wave and $N\Lambda\Lambda$ components on the neutron-star properties and find that appropriate repulsive contributions of these terms yield consistency with current neutron-star mass-radius observations. These results indicate that the present framework provides phenomenologically acceptable equations of state for dense $(N,\Lambda)$ matter over a wide range of densities and highlight the importance of future experimental data on heavier double-$\Lambda$ hypernuclei.
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Solar and Stellar Astrophysics

A method to derive self-consistent NLTE astrophysical parameters for 4 million high-resolution 4MOST stellar spectra in half a day with invertible neural networks

Victor F. Ksoll, Nicholas Storm, Maria Bergemann et al. (+5 more)

Modern spectroscopic surveys obtain spectra for millions of stars. However, classical spectroscopic methods can often be computationally expensive, rendering them impractical for the analysis of large datasets. We introduce a novel simulation-based deep-learning approach for the efficient analysis of high-resolution stellar spectra to be obtained with the upcoming high-resolution 4MOST spectrograph. We used a suite of synthetic non-local thermodynamic equilibrium (NLTE) spectra generated with Turbospectrum to mimic 4MOST observations and trained a conditional invertible neural network (cINN) for the purpose of predicting self-consistently stellar surface parameters and chemical abundances. The cINN is a neural network architecture that estimates full posterior distributions for the target stellar properties, providing an intrinsic uncertainty estimate. We evaluated the predictive performance of the trained cINN model on both synthetic data and observed spectra of stars. We found that our new cINN trained on NLTE synthetic spectra is capable of recovering stellar parameters with average errors ($\sigma$) of $33$ K for $T_\mathrm{eff}$, $0.16$ dex for $\log(g)$, and $0.12$ dex for [Fe/H], $0.1$ dex for [Ca/Fe], $0.11$ for [Mg/Fe], and $0.51$ dex for [Li/Fe], respectively, at a signal to noise ratio of 250 per Angstrom. From the analysis of the observed spectra of Gaia-ESO / 4MOST / PLATO benchmark stars, we verified that our NLTE estimates for stellar parameters and abundances are consistent with results obtained with the independent code TSFitPy. We conclude that the NLTE cINN is robust and can, theoretically, evaluate 4 million high-resolution 4MOST spectra in less than a day, using GPU acceleration.
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All authors Victor F. Ksoll, Nicholas Storm, Maria Bergemann, Katherine Lee, Ralf S. Klessen, R. Albarracín, Guillaume Guiglion, Gražina Tautvaišienė

Astrophysics of Galaxies

Linear filament and nested cluster evolution tomography (LANCET) I. Capture the evolution of dense gas in 14-parsec filament G316.8

Fengwei Xu, Ke Wang, Nicola Schneider et al. (+12 more)

A dynamic view of mass assembly is essential for understanding the formation of massive stars and clusters. Interpreting evolutionary diagnostics from Galactic-wide surveys, however, requires careful control of distance and environmental variations. The G316.8 filament provides an ideal laboratory: a 14-pc nearly linear structure composed of three contiguous subregions with comparable molecular gas reservoirs (~10,000 $M_\odot$ each) but spanning a clear evolutionary sequence from an infrared dark cloud (young) through a massive young stellar object (intermediate) to an HII region (evolved). As part of the Linear filament and nested cluster evolution tomography (LANCET) project, we mapped the full filament with the Atacama Compact Array at 1.3 mm, achieving 0.08 pc resolution over 17.1 pc$^2$. Combined with Herschel and APEX/ArTéMiS data, we derived high-resolution temperature and column-density maps. We quantify structural evolution using dense-fragment statistics, column-density PDFs, and $\Delta$-variance analysis. From young to evolved regions, the maximum fragment mass increases from 8 to 490 $M_\odot$, while the dense-gas mass fraction ($>0.5$ g cm$^{-2}$) rises from 0.4% to 9.6%. The N-PDF develops a secondary power-law tail and the $\Delta$-variance slope becomes progressively shallower, indicating ongoing assembly of dense sub-parsec structures. Our further ALMA 12m continuum and spectral line data will extend this dynamic scenarios down to 800 AU scale.
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All authors Fengwei Xu, Ke Wang, Nicola Schneider, Roberto Galván-Madrid, Floris F. S. van der Tak, Adam Ginsburg, Jonathan C. Tan, Hauyu Baobab Liu, Qizhou Zhang, Wenyu Jiao, Guido Garay, Sihan Jiao, Keyun Su, Beth M. Jones, Lei Zhu