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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 6 November

Solar and Stellar Astrophysics

Can MHD Oscillations Modulate Quasi-Periodic Plasma Release from Coronal Streamers?

Olena Podladchikova

Periodic density structures in the slow solar wind are associated with quasi-periodic plasma release from coronal streamer and open-closed boundary regions, but the origin of their organization remains uncertain. We distinguish the process that releases plasma from the process that sets or modifies its cadence. In the proposed source-modulator framework, S-Web, interchange, cusp, or current-sheet reconnection releases the plasma, while structured MHD responses may modulate density or release rate. An observation-informed parameter-space analysis gives compact slow-mode periods of about 22-231 min; reproducing 80-130 min requires an effective path length of 0.35-1.20 solar radii. In a classical top-hat cylinder with L/a = 5-50 and rho_i/rho_e = 1.6-2.5, the fundamental fast sausage mode is not trapped and the minimum trapped harmonic is approximately n = 4-50. A transverse fast-timescale benchmark based on a = 0.10-0.45 solar radii and outer-coronal fast speeds of 250-530 km/s gives 5.7-55 min. A corresponding fast-interface proxy gives 4.4-93 min, but is not a current-sheet eigenmode solution. Kink responses are constrained empirically rather than by inserting observer-frame propagation speeds into a standing-mode formula: one COR1 event showed an approximately 25 min pulse, whereas a LASCO/COR2 survey found global streamer-wave periods of 2-8 hr, observer-frame speeds of 360-740 km/s, and typically only one or two visible cycles. Among the candidates considered here, compact slow modes are the best-constrained stable compressive modulators; confirming their role requires constraints on longitudinal reflection and damping. Surface/current-sheet responses remain high-priority coupling candidates but require a sheet-specific dispersion relation; kink responses are transient geometric candidates; and tearing/plasmoid formation remains a strong intrinsic reconnection-driven alternative.
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Astrophysics of Galaxies

JWST provides a new view of cosmic dawn: latest developments in studies of early galaxies

Jorryt Matthee

Studies of the distant Universe are providing key insights into our understanding of the formation of galaxies. The advent of the James Webb Space Telescope (JWST) has significantly enhanced our observational capabilities, leading to an expanded redshift frontier, providing unprecedented detail in the characterization of early galaxies and enabling the discovery of new populations of accreting black holes. This review aims to provide an introduction to the basic processes and components that shape the observed spectra of galaxies, with a focus on their relevance to techniques with which high-redshift galaxies are selected. The review further introduces specific topics that have attracted significant attention in recent literature, including the discovery of highly efficient galaxy formation in the early Universe, the relation between galaxies and the process of reionization, new insights into the formation of the first stars and the enrichment of interstellar gas with heavy elements, and breakthroughs in our understanding of the origins of supermassive black holes.
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Solar and Stellar Astrophysics

Empirical measures of the largest amounts of magnetically-induced radius inflation in low-mass stars

D. J. Mullan and J. MacDonald

Access to precise empirical estimates of stellar radii in recent decades has revealed that the radii of certain low-mass stars are inflated relative to stellar structure predictions. The largest inflations are found in magnetically active stars. Although various attempts have been made to incorporate magnetic effects into stellar structure codes, a major source of uncertainty is associated with our lack of knowledge as to how the field strength varies inside the star. Here, we point out that a recent study of 44 eclipsing binaries in the Kepler field by Cruz et al. may enable us for the first time to set an upper limit Bc on the field strengths inside the 88 stars in the sample. According to our magneto-convective model, the largest empirical inflations reported by Cruz et al. can be replicated if Bc is about 10 kG inside stars with masses greater than 0.65 MSun. On the other hand, in lower mass stars, especially those with masses less than 0.4 MSun, our model predicts that the largest empirical inflations may require significantly stronger fields, i.e. Bc approximately 100-300 kG.
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Solar and Stellar Astrophysics

Using ML-based Regression Techniques to Mitigate GOES Energetic Proton Flux Data Contamination and Magnetospheric Effects

Aatiya Ali and Viacheslav Sadykov

Positioned at geostationary orbit (GEO) ~36,000 km above Earth, NOAA's GOES series has recorded real-time energetic proton flux measurements crucial for space weather monitoring for over three decades. Although machine learning models have advanced solar energetic particle (SEP) event prediction using GOES data, the sudden yet sparse nature of SEP events necessitates high-quality proton flux measurements. Previous studies have identified contamination issues in GOES data, when the presence of higher-energy protons can cause parasitic signals in lower-energy GOES channels and lead to artificially elevated fluxes in lower energy ranges (e.g., 10 - 50 MeV). As of now, no universal correction method has been implemented for the publicly available NOAA data. In addition, the effects of Earth's magnetosphere on the 10 - 50 MeV particles are not fully understood yet. This study assesses a reconstruction method using concurrent solar proton event (SPE) measurements from SOHO-EPHIN, which align well with GOES measurements of SPEs across solar cycles 23 and the bulk of cycle 24, but represent the off-magnetospheric environment of the Lagrange 1 point. We train regression models on GOES proton fluxes across multiple energy bins, employing EPHIN fluxes as prediction targets. We expect that similar approaches can allow us to derive non-contaminated flux proxies that preserve valuable data and more accurately capture the characteristics of SPEs, providing a more stable dataset for analyzing SEP behavior and potentially improving SEP event prediction models.
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High Energy Astrophysical Phenomena

FermiPhased: A tool for phase-resolved likelihood analysis of Fermi-LAT data

Alexander Lange and B.B. K

The Fermi Large Area Telescope has enabled detailed studies of high-energy astrophysical sources. To support analysis, we present FermiPhased, a flexible, open-source tool for phase-resolved studies of pulsars, binaries, and other periodically variable sources. Built on the Fermipy framework, FermiPhased offers three modes: standard, adaptive (fixed counts), and joint phase-resolved analysis, enabling users to flexibly bin data based on phase, count statistics, or jointly fit different epochs of interest. FermiPhased is optimized for parallel execution and use on computing clusters. It enables parallelized extraction of phase-resolved fluxes, spectra, and intermediary data products, with tutorials and documentation available on GitHub.
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Solar and Stellar Astrophysics

Comparative Analysis of 10 - 50 MeV Solar Proton Events at Lagrange Point 1 and the Geostationary Orbit

Aatiya Ali and Viacheslav Sadykov

Solar proton events (SPEs) pose radiation hazards, disrupt technology, and impact operations on Earth and in space, making continuous monitoring essential. We compare 10-50 MeV proton flux measurements from SOHO/EPHIN at Lagrange Point 1 (L1) with those from NOAA/GOES in geostationary orbit (GEO) during Solar Cycle 23 and most of Cycle 24. We identify 83 >=10 pfu SPEs observed at both locations and classify them into S1-S4 categories (comparable to NOAA's solar radiation storm scales). EPHIN detected earlier onsets and longer durations across all categories, along with earlier peaks and ends for S1-S3, while GOES recorded slightly earlier peak and end times for S4. S1 median timing offsets (EPHIN relative to GOES) were -20 +/- 50 min (onsets), -1.00 +/- 1.42 hr (peaks), and -1.08 +/- 2.21 hr (ends), with similar trends for S2-S3 and near-simultaneity for S4 (peaks ~ -0.17 +/- 1.62 hr; ends ~ +0.04 +/- 3.33 hr). Flux comparisons show that EPHIN measurements modestly exceed GOES for S1 (median ratios ~1.11 for peaks and ~1.06 for fluence) and are lower than GOES for stronger events (peaks ~0.97 +/- 0.29, 0.84 +/- 0.21; fluence ~0.84 +/- 0.16, 0.75 +/- 0.16 for S2-S3). The EPHIN-to-GOES peak flux and fluence ratios reach 0.16 +/- 0.03 and 0.29 +/- 0.07, respectively, for S4 events, originating from contamination of lower-energy GOES channels. Correlation analyses show no significant flux dependence on geomagnetic indices, field strength, or spacecraft position, suggesting minimal near-Earth modulation of >=10 MeV proton access at GEO. These results highlight systematic differences in how SPEs manifest at L1 versus GEO and offer practical guidance for forecasting beyond Earth's magnetosphere, supporting mission planning for near-Earth and cislunar exploration, including Artemis.
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Instrumentation and Methods for Astrophysics

Blind Strong Gravitational Lensing Inversion: Joint Inference of Source and Lens Mass with Score-Based Models

Gabriel Missael Barco, Ronan Legin, Connor Stone et al. (+2 more)

Score-based models can serve as expressive, data-driven priors for scientific inverse problems. In strong gravitational lensing, they enable posterior inference of a background galaxy from its distorted, multiply-imaged observation. Previous work, however, assumes that the lens mass distribution (and thus the forward operator) is known. We relax this assumption by jointly inferring the source and a parametric lens-mass profile, using a sampler based on GibbsDDRM but operating in continuous time. The resulting reconstructions yield residuals consistent with the observational noise, and the marginal posteriors of the lens parameters recover true values without systematic bias. To our knowledge, this is the first successful demonstration of joint source-and-lens inference with a score-based prior.
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All authors Gabriel Missael Barco, Ronan Legin, Connor Stone, Yashar Hezaveh, Laurence Perreault-Levasseur

Solar and Stellar Astrophysics

Comprehensive Listing of 208 Nova White Dwarf Masses As the Primary Determinant of Spectral-Class and Light-Curve-Class

Bradley E. Schaefer

For Galactic novae, I calculate and collect a comprehensive catalog of 208 measures of white dwarf (WD) masses ($M_{\rm WD}$) and 232 measures of average $V$ magnitudes in quiescence ($V_q$). These are collected into a comprehensive catalog of most fundamental properties of all 402 known Galactic novae. The nova light curve and spectral classes are determined primarily by $M_{\rm WD}$. With an apparently clean cutoff, nova with light curve shapes in the S, P, O, and C classes have $>$0.95 $M_{\odot}$, while the J, D, and F class novae have $<$0.95 $M_{\odot}$. The speed class of the light curves is $t_3$=$10^{(-1.73M_{\rm WD})}$$\times$1900 days. The spectral class of novae is Fe II below 1.15 $M_{\odot}$, is He/N above 1.15 $M_{\odot}$, and the Hybrid novae are spread around this division. Neon novae have WD masses ranging from 0.53–1.37 $M_{\odot}$, with 76% being measured to be below their minimum formation mass of 1.2 $M_{\odot}$, demonstrating that most are losing mass over each eruption cycle. The FWHM velocity of the Balmer line profiles is close to 0.23 times the WD escape velocity, or roughly $10^{(M_{\rm WD}/2)}$$\times$500 km s$^{-1}$ for $<$1.3 $M_{\odot}$. And all the known Galactic recurrent novae are $>$1.2 $M_{\odot}$. For issues involving the late expansion of the ejecta, I find that the visibility of shells is strongly biased towards novae with orbital periods $<$0.33 days, and that the visibility of $\gamma$-rays from the shells are strongly biased towards novae with fast declines, with $t_3$ a proxy for the $\gamma$-ray luminosity.
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Cosmology and Nongalactic Astrophysics

How Low Can You Go: Constraining the Effects of Catalog Incompleteness on Dark Siren Cosmology

Madison VanWyngarden, Maya Fishbach, Aditya Vijaykumar et al. (+2 more)

Gravitational waves (GWs) serve as standard sirens by directly encoding the luminosity distance to their source. When the host galaxy redshift is known, for example, through observation of an electromagnetic (EM) counterpart, GW detections can provide an independent measurement of the Hubble constant, $H_0$. However, even in the absence of an EM counterpart, inferring $H_0$ is possible through the dark siren method. In this approach, every galaxy in the GW localization volume is considered a potential host that contributes to a measurement of $H_0$, with redshift information supplied by galaxy catalogs. Using mock galaxy catalogs, we explore the effect of catalog incompleteness on dark siren measurements of $H_0$. We find that in the case of well-localized GW events, if GW hosts are found in all galaxies with host halo masses $M_h > 2 \times10^{11} M_{\odot}h^{-1}$, catalogs only need to be complete down to the 1% brightest magnitude $M_i < -22.43$ to draw an unbiased, informative posterior on H0. We demonstrate that this is a direct result of the clustering of fainter galaxies around brighter and more massive galaxies. For a mock galaxy catalog without clustering, or for GW localization volumes that are too large, using only the brightest galaxies results in a biased $H_0$ posterior. These results are important for informing future dark siren analyses with LIGO-Virgo-KAGRA as well as next-generation detectors.
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All authors Madison VanWyngarden, Maya Fishbach, Aditya Vijaykumar, Alexandra G. Guerrero, Daniel E. Holz

Astrophysics of Galaxies

Synthetic JWST galaxy images in the TNG50 simulation - I. Model validation and comparison to observations

Alejandro Guzmán-Ortega, Gustavo Bruzual, Vicente Rodriguez-Gomez et al. (+1 more)

We use the TNG50 cosmological simulation and three-dimensional radiative transfer post-processing to generate dust-aware synthetic observations of galaxies at $ 3 \leq z \leq 6 $ and $ \log_{10}(M_\ast/\mathrm{M}_\odot) \geq 8.5 $, tailored to match the depth and resolution of current deep JWST surveys (NGDEEP and JADES). We analyse the performance of spectral energy distribution (SED) fitting on the simulated sample, focusing on the recovery of photometric redshift and stellar mass. At $ z \leq 5 $, we find that 90 per cent of redshifts are recovered within $ \pm0.2 $, but performance declines at $ z = 6 $. Stellar masses are generally well-recovered within a factor of 2, but are systematically underestimated regardless of redshift, a trend that is more pronounced at the high-mass end $ ( \log_{10}(M_\ast/\mathrm{M}_\odot) \geq 10 ) $. In addition, we study the observer-frame colours of galaxies in this redshift range as well as the SED-inferred $UVJ$ diagram. We find that TNG50 galaxies broadly follow the tendencies marked by observations, but tend to be slightly redder at lower masses and bluer at higher masses, regardless of redshift. Finally, using a colour-based definition of quiescence, we determine the fraction of quiescent galaxies as a function of stellar mass at $ 3 \leq z \leq 6 $, which we find to be broadly consistent with observations.
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All authors Alejandro Guzmán-Ortega, Gustavo Bruzual, Vicente Rodriguez-Gomez, Lars Hernquist

Astrophysics of Galaxies

Kinematic and extinction analysis of a potential spiral arm beyond the Galactic bar

Simran Joharle, Francisco Nogueras-Lara and Karl Fiteni

Determining the structure of the Milky Way is essential for understanding its morphology, dynamics, and evolution. However, studying its innermost regions is challenging due to high extinction and crowding. The detection of a double red clump (RC; core-helium-burning stars) feature at very low Galactic latitudes suggests the presence of a spiral arm beyond the Galactic bar, providing new insights into the Galaxy's structure along this complex line of sight. We evaluate this possibility by analysing the proper motion and extinction distributions of the detected RC features. We constructed proper motion and extinction difference maps to investigate the kinematic and reddening properties of the RC populations, and the kinematic differences were validated using N-body simulations of a Milky Way-like galaxy. We find that the two RC features are kinematically distinct, with a relative proper motion difference of $-0.16\pm0.02\, mas/yr$ in the component parallel to the Galactic plane. This difference can be explained by Galactic rotation if the two RCs lie at different distances, consistent with the simulations. The extinction towards the secondary RC is also $\sim0.05$ mag higher than that of the primary RC. Additionally, we estimate that the extinction difference between the RC features corresponds to only $\sim5\%$ of the total extinction from Earth to the first RC, suggesting little interstellar material between the farthest edge of the Galactic bar and the kinematically distinct structure traced by the secondary RC. Using $JK_s$ photometry, we derive $A_J/A_{K_s}=3.34\pm0.07$, consistent with previous results and showing no significant variation across fields or along the line of sight. The results support the secondary clump tracing a distant structure, possibly a spiral arm, although we cannot exclude that the population belongs to the disc.
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Astrophysics of Galaxies

ALMA Sub-parsec Resolution Dense Molecular Line Observations of the NGC 1068 Nucleus

Masatoshi Imanishi, Bernd Vollmer, Yoshiaki Hagiwara et al. (+3 more)

We present the results of our ALMA observations of the dense molecular HCN J=4-3 and HCO$^{+}$ J=4-3 lines at $\lesssim$1 pc ($\lesssim$14 mas) resolution in the nuclear region of the nearby ($\sim$14 Mpc) well-studied AGN NGC 1068. Both emission lines are clearly detected around the AGN along an almost east-west direction, which we ascribe to the dusty molecular torus. The HCN J=4-3 emission is brighter than the HCO$^{+}$ J=4-3 emission in the compact ($\lesssim$3-5 pc) torus region. Apparent counter-rotation between the inner ($\lesssim$2 pc) and outer ($\gtrsim$2 pc) parts of the western torus, previously seen in $\sim$1.5 pc-resolution HCN J=3-2 and HCO$^{+}$ J=3-2 data, is also confirmed in our new $\lesssim$1 pc-resolution HCN J=4-3 and HCO$^{+}$ J=4-3 data. We apply a physically counter-rotating torus model, in which a compact dense gas clump collided with the western side of the existing rotating torus from the opposite direction, and we find that this model largely reproduces the observed properties of the combined new $\lesssim$1 pc-resolution HCN J=4-3 and HCO$^{+}$ J=4-3 data, and the previously obtained $\lesssim$1.5 pc-resolution HCN J=3-2 and HCO$^{+}$ J=3-2 data.
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All authors Masatoshi Imanishi, Bernd Vollmer, Yoshiaki Hagiwara, Kouichiro Nakanishi, Takuma Izumi, Nozomu Kawakatu

Cosmology and Nongalactic Astrophysics

Machine Learning-Driven Analysis of kSZ Maps to Predict CMB Optical Depth $\tau$

Farshid Farhadi Khouzani, Abinash Kumar Shaw, Paul La Plante et al. (+2 more)

Upcoming measurements of the kinetic Sunyaev-Zel'dovich (kSZ) effect, which results from Cosmic Microwave Background (CMB) photons scattering off moving electrons, offer a powerful probe of the Epoch of Reionization (EoR). The kSZ signal contains key information about the timing, duration, and spatial structure of the EoR. A precise measurement of the CMB optical depth $\tau$, a key parameter that characterizes the universe's integrated electron density, would significantly constrain models of early structure formation. However, the weak kSZ signal is difficult to extract from CMB observations due to significant contamination from astrophysical foregrounds. We present a machine learning approach to extract $\tau$ from simulated kSZ maps. We train advanced machine learning models, including swin transformers, on high-resolution seminumeric simulations of the kSZ signal. To robustly quantify prediction uncertainties of $\tau$, we employ the Laplace Approximation (LA). This approach provides an efficient and principled Gaussian approximation to the posterior distribution over the model's weights, allowing for reliable error estimation. We investigate and compare two distinct application modes: a post-hoc LA applied to a pre-trained model, and an online LA where model weights and hyperparameters are optimized jointly by maximizing the marginal likelihood. This approach provides a framework for robustly constraining $\tau$ and its associated uncertainty, which can enhance the analysis of upcoming CMB surveys like the Simons Observatory and CMB-S4.
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All authors Farshid Farhadi Khouzani, Abinash Kumar Shaw, Paul La Plante, Bryar Mustafa Shareef, Laxmi Gewali

Solar and Stellar Astrophysics

Secondary small-scale dynamics of a Rayleigh-Taylor unstable solar prominence

Madhurjya Changmai, Jack M. Jenkins and Rony Keppens

Quiescent solar prominences show distinct small-scale dynamics in observations. Their internal density contrasts with the surrounding corona make them susceptible to Rayleigh-Taylor (RT) instabilities, leading to vertically structured prominence morphologies when observed at the solar limb. As a result, prominences develop bubbles and plumes, along with secondary Kelvin-Helmholtz (KH) roll-ups along their edges. Recent observations also suggest magnetic reconnection events within the RT-driven turbulent flows. We perform high-resolution 2.5D resistive magnetohydrodynamic simulations using the open-source MPI-AMRVAC code, reaching a spatial resolution of $\sim 11.7$ km in a 2D domain of size 30 Mm$\times$30 Mm and evolving the system for approximately 10 minutes of solar time. A dense, magnetic pressure supported prominence serves as the initial state, which becomes unstable at the prominence-corona interface. The resulting interaction between RT and KH instabilities leads to the formation of current sheets and localized reconnection events. The reconnection-driven outflows form energetic jets that enhance energy transport and dissipation across the prominence. We analyze our high-resolution prominence simulation using synthetic images of the broadband SDO/AIA 094, 171, and 193 Å and narrowband H$\alpha$ filters, to compare the developing fine-scale structures with their observational counterparts. Most secondary instabilities emerge in the hotter coronal regions surrounding the cooler prominence core. While our simulated features match observed scales, speeds, and duration, the simulated activity remains concentrated in hot, surrounding coronal plasma rather then the cool prominence material, implying that key physical ingredients may be missing. Future 3D studies in more realistic magnetic configurations are required to address these limitations.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Millicharged Particle Production in Pulsars via the Schwinger Effect

Chris Kouvaris and Ian M. Shoemaker

Low mass particles with small electric charges can be produced abundantly in large electric fields via the Schwinger effect. We study the production rate of such particles inside the polar gap of nearby pulsars. After production they are accelerated above MeV energies by the local electric fields. These pulsar-produced millicharged particles can be detected at Earth in low-threshold dark matter direct detection experiments. We find that the current XENONnT data constrains millicharged particles produced in the Crab pulsar to have charges less than $O(10^{-6})$ for sub-eV masses.
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Solar and Stellar Astrophysics

HiSAXy: A fast methodology for solar wind structure identification in millions of time series

Hala Lamdouar, Sairam Sundaresan, Anna Jungbluth et al. (+8 more)

We present a hybridized unsupervised clustering algorithm Hisaxy as a novel way to identify frequently occurring magnetic structures embedded in the interplanetary magnetic field (IMF) carried by the solar wind. The Hisaxy algorithm utilizes a combination of indexable Symbolic Aggregate approXimation (iSAX) and Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) to efficiently identify clusters of patterns embedded in time series data. We utilized Hisaxy to identify small-scale structures, known as discontinuities, embedded in time series measurements of the IMF. In doing so, we demonstrate the capability of the algorithm to significantly reduce the amount of human analysis hours required to identify these structures, all the while maintaining a high degree of self similarity within a given cluster of time series data.
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All authors Hala Lamdouar, Sairam Sundaresan, Anna Jungbluth, Sudeshna Boro Saikia, Amanda Joy Camarata, Nathan Miles, Marcella Scoczynski, Mavis Stone, Andrés Muñoz-Jaramillo, Ayris Narock, Adam Szabo

Astrophysics of Galaxies

The essential elements of dust evolution: a-C(:H) nanoparticle sub-structures and photo-fragmentation

A.P. Jones and N. Ysard

Hydrogenated amorphous carbon materials, a-C(:H), are heterogeneous structures consisting of carbon atoms in different hybridisation states and bonding configurations and are thought to constitute a significant and observationally important fraction of the interstellar dust material. This work aims to characterise semi-conducting a-C(:H) nanoparticle structures and, in particular, their property-characterising aromatic domain size distribution and so predict how they will behave in intense UV radiation fields that can fragment them through dissociative and charge effects as a result of carbon-carbon bond-breaking. Using a statistical approach we determine the typical sizes of the aromatic domains, their size distribution, how they are network-bonded, and where they are to be found within the structure. We consider the effects of thermal excitation, photo-dissociation and charging of a-C(:H) nanoparticles, and the products of their fragmentation. The derived UV photon-induced fragmentation lifetimes for nanometre-sized a-C(:H) nanoparticles, with radii ~0.4-0.5nm radius and containing ~40-60 carbon atoms, are of the order of 10^6-10^7yr in the diffuse interstellar medium and likely 10^2-10^4 times shorter in photodissociation regions, depending on the local radiation field intensity. Grains larger than this are stable against photodissociation. In H{\footnotesize II} regions only a-C(:H) nanoparticles with radii greater than 0.7nm (> 150 carbon atoms) are likely to survive. The photon-driven fragmentation of sub-nanometre a-C(:H) particles was determined to be important in the diffuse interstellar medium and also in high excitation regions, such as photodissociation and HII regions. However, in these same regions Coulomb fragmentation is unlikely to be an important dust destruction process.
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Cosmology and Nongalactic Astrophysics

Dents in the Mirror: A Novel Probe of Dark Matter Substructure in Galaxy Clusters from the Astrometric Asymmetry of Lensed Arcs

Derek Perera, Daniel Gilman, Liliya L. R. Williams et al. (+5 more)

Astrometric perturbations of lensed arcs behind galaxy clusters have been recently suggested as promising probes of small-scale ($\lesssim10^9 M_{\odot}$) dark matter substructure. Populations of cold dark matter (CDM) subhalos, predicted in hierarchical structure formation theory, can break the symmetry of arcs near the critical curve, leading to positional shifts in the observed images. We present a novel statistical method to constrain the average subhalo mass fraction ($f_{\rm sub}$) in clusters that takes advantage of this induced positional asymmetry. Focusing on CDM, we extend a recent semi-analytic model of subhalo tidal evolution to accurately simulate realistic subhalos within a cluster-scale host. We simulate the asymmetry of lensed arcs from these subhalo populations using Approximate Bayesian Computation. Using mock data, we demonstrate that our method can reliably recover the simulated $f_{\rm sub}$ to within 68% CI in 73% of cases, regardless of the lens model, astrometric precision, and image morphology. We show that the constraining power of our method is optimized for larger samples of well observed arcs, ideal for recent JWST observations of cluster lenses. As a preliminary test, we apply our method to the MACSJ0416 Warhol arc and AS1063 System 1. For Warhol we constrain the upper limit on $\log f_{\rm sub} < -3.48^{+1.00}_{-0.91}$, while for AS1063 System 1 we constrain $\log f_{\rm sub} = -2.44^{+0.61}_{-0.86}$ (both at 68% CI), consistent with CDM predictions. We elaborate on our method's limitations and its future potential to place stringent constraints on dark matter properties in cluster environments.
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All authors Derek Perera, Daniel Gilman, Liliya L. R. Williams, Liang Dai, Xiaolong Du, Gregor Rihtarsic, Joaquin Becerra-Espinoza, Allison Keen

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

Fast and Flexible Neutrino Decoupling Part I: The Standard Model

M. Escudero, G. Jackson, M. Laine et al. (+1 more)

Cosmological determinations of the number of relativistic neutrino species, $N^{ }_{\rm eff}$, are becoming increasingly accurate, and further improvements are expected both from CMB and BBN data. Given this context, we update the evaluation of $N^{ }_{\rm eff}$ and the current entropy density via the momentum-averaged approach. This allows for a numerically fast description of neutrino decoupling, easily portable to an array of new physics scenarios. We revisit all aspects of this approach, including collision terms with full electron mass dependence, finite temperature QED corrections to the equation of state, neutrino oscillations, and the modelling of neutrino ensembles with effective chemical potentials. For integrated observables, our results differ by less than $0.04\%$ from the solution of the momentum-dependent evolution equation. We outline how to extend the approach to BSM settings, and will highlight its power in Part II. To facilitate the practical implementation, we release a Mathematica and Python code within nudec_BSM_v2, easily linkable to BBN codes.
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All authors M. Escudero, G. Jackson, M. Laine, S. Sandner

Astrophysics of Galaxies

Sub-Gyr variability around the SFMS and its contribution to the scatter

A. Camps-Fariña, M. Chamorro-Cazorla and S. F. Sánchez

We aim to measure the evolution of individual galaxies around the Star Formation Main Sequence (SFMS) during the last Gyr as a function of their stellar mass to quantify how much of its scatter is due to short-term variability.We derived star formation histories using full spectral fitting for a sample of 8,960 galaxies from the MaNGA survey to track the position of the galaxies in the SFMS during the last Gyr.The variability correlates with both the stellar mass of the galaxies and their current position in both the SFMS and the mass-metallicity relation (MZR), with the position in the latter strongly affecting variability in SFR. While most of the fluctuations are compatible with stochasticity, there is a very weak but statistically significant preference for $\sim135-150$ Myr time-scales. These results support a strong self-regulation of SFR within galaxies, establishing characteristic intensities and time-scales for bursts of star formation and quenching episodes. We also find that short-term variability cannot account for the entirety of the scatter in the SFMS. It appears to originate to a similar degree in short-term variability and long-term (halo-level) differentiation and fits predictions from models.
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Earth and Planetary Astrophysics

Micrometeoroid Impact Rate Analysis for an Artemis-Era Lunar Base

Daniel A. Yahalomi, Matthew T. Scoggins, Nasiah Anderson et al. (+5 more)

NASA's Artemis Mission aims to return astronauts to the Moon and establish a base at the lunar south pole. A key challenge is understanding the threat from micrometeoroid impacts, which are too small to monitor directly. Using NASA's Meteoroid Engineering Model 3 (MEM~3), we estimate micrometeoroid impact rates on a base comparable in size to the International Space Station (100\,m $\times$ 100\,m $\times$ 10\,m). We find that a lunar base would experience $\sim$15,000–23,000 incident impacts per year by micrometeoroids with a mass range of $10^{-6}$–$10^{1}$~g, depending on location – with minima at the lunar poles, a maximum near the sub-Earth longitude, and a factor of $\sim$1.6 variation between the two. To assess the mitigating effect of protection systems, we present a functional relationship describing the number of impacts that penetrate the shielding as a function of the minimum meteoroid mass capable of penetrating the shield – the “critical mass.” We estimate that state-of-the-art Whipple shields protect against $\sim$99.9997% of micrometeoroids. By re-running MEM~3 with a minimum mass equal to the critical mass of modern Whipple shields, we determine that a shielded lunar base would experience $\sim$0.024–0.037 penetrating impacts per year – again with minima at the poles and a maximum near the sub-Earth longitude. These results indicate that (1) the lunar poles are optimal for sustained habitation, (2) gravitational focusing by Earth dominates over its geometric shielding for this micrometeoroid flux, and (3) current shielding technology can reduce micrometeoroid threats by nearly five orders of magnitude, making long-duration lunar habitation feasible.
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All authors Daniel A. Yahalomi, Matthew T. Scoggins, Nasiah Anderson, Mark Driker, Kokoro Onuma, Kwamena T. Awotwi, Justin M. Donovan, Priyan Sathianathan

High Energy Astrophysical Phenomena

Confirmation of SRGt 062340.2-265751 as a nova-like cataclysmic variable with a possible magnetic nature

V. A. Cúneo, A. D. Schwope, J. Kurpas et al. (+5 more)

SRGt 062340.2-265751, a cataclysmic variable identified by SRG/eROSITA thanks to its significant X-ray variability, remains poorly characterised despite the multi-wavelength follow-up. We present spectral and timing analyses from the first dedicated X-ray and ultraviolet observations with XMM-Newton, complemented by SRG/eROSITA data from four all-sky surveys (eRASS1-4) and ASAS-SN optical photometry. Our timing analysis reveals a >8$\sigma$ significant modulation at 3.6 $\pm$ 0.5 hours, likely representing the orbital period. Long-term ASAS-SN monitoring confirms the source as a VY Sculptoris-type nova-like system, while short-timescale X-ray and ultraviolet variability, down to a few minutes, suggests a possible underlying magnetic white dwarf. Two additional significant X-ray modulations at 43 $\pm$ 1 min and 36.0 $\pm$ 0.7 min tentatively point to the spin period of an intermediate polar. The best-fit XMM-Newton energy spectra reveal a multi-temperature thermal plasma ($kT$ = 0.23, 0.94, and 5.2 keV), while the SRG/eROSITA spectra are consistent with a single-temperature thermal plasma of a few keV. We estimate unabsorbed X-ray luminosities of $\gtrsim$$10^{32}$ erg s$^{-1}$ (0.2-12 keV). Broadband spectral energy distribution modelling, from near-ultraviolet to infrared, indicates a disc-dominated system consistent with a nova-like classification. We discuss these results in the context of the source's confirmed nova-like classification and its possible magnetic nature, a scenario increasingly supported by discoveries of intermediate polars exhibiting VY Sculptoris-type nova-like features.
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All authors V. A. Cúneo, A. D. Schwope, J. Kurpas, A. Avakyan, J. Brink, D. A. H. Buckley, C. Maitra, M. Veresvarska

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

Effective Field Theories for Neutron Stars Physics

J. M. Alarcón, E. Lope-Oter and Y. Cano

There is an increasing interest in the community for the Neutron Stars and what we can learn from them. In this review we show how chiral effective field theory, combined with many-body methods, can provide important results that connect Neutron Star properties at zero temperature to nuclear physics and allows to use these compact objects as laboratories of new physics.
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Astrophysics of Galaxies

Heavy black hole seed survivors in dwarf galaxies: a case study of Leo I

Matthew T. Scoggins, Zoltan Haiman and Fabio Pacucci

The supermassive black holes (SMBHs) with mass $M_\bullet > 10^9 \, \rm M_\odot$ hosted by high-redshift galaxies have challenged our understanding of black hole formation and growth, as several pathways have emerged attempting to explain their existence. The "heavy-seed" pathway eases the problem with the progenitors of these SMBHs having birth masses up to ${\sim} 10^5~{\rm M_\odot}$. Here, we investigate the possibility that a local dwarf galaxy, Leo I, harbors a heavy-seed descendant. Using Monte-Carlo merger trees to generate the merger histories of 1,000 dark matter halos similar to the Milky Way (MW; with a mass of ${\sim} 10^{12}~{\rm M_\odot}$ at redshift $z{=}0$). We search for Leo-like satellite halos among these merger trees, and investigate the probability that the progenitors of some of these satellites formed a heavy seed. We derive the likelihood of such "heavy seed survivors" (HSSs) across various formation and survival criteria as well as Leo-similarity criteria. We find that the virial temperature for the onset of atomic cooling and rapid gas infall that yields heavy seeds, $T_{\rm act}$, has the largest impact on the number of HSSs. We find HSSs in a fraction $0.7\%$, $18.1\%$, and $96.5\%$ of MW-like halos when $T_{\rm act}$ is set to $9,000$K, $7,000$K, and $5,000$K respectively. This suggests that Leo I could be hosting a heavy seed and could provide an opportunity to disentangle heavy seeds from other SMBH formation mechanisms.
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Cosmology and Nongalactic Astrophysics

Large-Scale Structure Probes of the Post-Inflationary Axiverse

Marco Gorghetto, Sokratis Trifinopoulos and Georgios Valogiannis

We study the cosmology of axions in the post-inflationary scenario, where random initial conditions and the ensuing string-domain-wall network generate an isocurvature power spectrum. Axions radiated from strings behave as warm, wave-like dark matter: when they constitute the full dark matter abundance, free streaming sets the strongest bounds on their mass. For subdominant fractions, despite being warm, they still lead to an overall enhancement of structure growth in the dominant component, seeded by the axion white-noise fluctuations. We search for this effect using the ultraviolet luminosity function (UVLF) of galaxies at $z=4$-$10$, probing $k\simeq0.5$-$10\,\mathrm{Mpc}^{-1}$. Combining the UVLF analysis with Lyman-$\alpha$ and CMB data yields the leading cosmological limits on post-inflationary axion dark matter, sensitive to tiny fractions for $m_a\lesssim10^{-21}\,\mathrm{eV}$. As a byproduct, we obtain new constraints on generic white-noise power spectra from the UVLF. These results apply broadly to scenarios that generate similar isocurvature perturbations, linking early-universe field dynamics to high-redshift structure formation.
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Cosmology and Nongalactic Astrophysics

Combining CMB datasets with consistent foreground modelling

M. Tristram, M. Douspis, A. Gorce et al. (+7 more)

We present a joint cosmological analysis combining data from the Planck satellite, the Atacama Cosmology Telescope, and the South Pole Telescope. We construct a unified likelihood that reproduces the measured temperature and polarisation power spectra by jointly modelling the cosmic microwave background (CMB) signal, Galactic and extragalactic foregrounds, and instrumental systematics across all datasets. We reduce reliance by combining datasets and improve the robustness of parameter estimation by marginalising over the choice of foreground templates. Within this joint analysis, $\Lambda$CDM parameters exhibit remarkable stability with respect to variations in foreground modelling. Parameters for cosmological extensions are more sensitive to these assumptions, with uncertainties increasing by up to 35% in the neutrino sector after marginalising over foreground models. In contrast, the determination of foreground parameters depends more strongly on the assumptions made about the underlying foreground models. Overall, this work demonstrates the feasibility and reliability of a fully joint analysis of current CMB experiments and emphasizes the importance of consistent and accurate foreground modelling for the scientific goals of next-generation, high-sensitivity CMB surveys.
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All authors M. Tristram, M. Douspis, A. Gorce, S. Henrot-Versillé, L. T. Hergt, S. Ilic, L. McBride, M. Muñoz-Echeverría, E. Pointecouteau, L. Salvati

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

Higgs inflation in Weyl-invariant Einstein-Cartan gravity

Georgios K. Karananas and Mikhail Shaposhnikov

In this short note we analyze the inflationary dynamics in Weyl-invariant Einstein-Cartan gravity coupled to the Standard Model of particle physics. We take the axion-like particle of gravitational origin to be approximately massless in the early Universe and show how inflation with the Higgs field materializes.
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Instrumentation and Methods for Astrophysics

SGNL: Scalable Low-Latency Gravitational Wave Detection Pipeline for Compact Binary Mergers

Yun-Jing Huang, Chad Hanna, Leo Tsukada et al. (+8 more)

We present SGNL, a scalable, low-latency gravitational-wave search pipeline. It reimplements the core matched-filtering principles of the GstLAL pipeline within a modernized framework. The Stream Graph Navigator library, a lightweight Python streaming framework, replaces GstLAL's GStreamer infrastructure, simplifying pipeline construction and enabling flexible, modular graph design. The filtering core is reimplemented in PyTorch, allowing SGNL to leverage GPU acceleration for improved computational scalability. We describe the pipeline architecture and introduce a novel implementation of the Low-Latency Online Inspiral Detection algorithm in which components are pre-synchronized to reduce latency. Results from 40 days of data show that SGNL's event recovery and sensitivity are consistent with GstLAL's within statistical and systematic uncertainties. Notably, SGNL achieves a median latency of 4.7 seconds, compared to 9.0 seconds for GstLAL.
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All authors Yun-Jing Huang, Chad Hanna, Leo Tsukada, Amanda Baylor, Olivia Godwin, Prathamesh Joshi, James Kennington, Cody Messick, Surabhi Sachdev, Ron Tapia, Zach Yarbrough

Instrumentation and Methods for Astrophysics · Cross-listed from physics.ed-ph

CATS: Empowering the next generation of rocket scientists through educational flight computers

Jonas Binz, Nemanja Stojoski and Luca Jost

This paper presents an in-depth analysis of the Vega flight computer, and its corresponding ground station developed by CATS, a company producing open-source flight computers and tracking systems tailored for student-made rockets. These flight computers, designed to support rockets reaching altitudes of up to 30 km and possibly higher, play a crucial role in advancing educational rocketry and facilitating hands-on learning experiences in aerospace engineering. As the official sponsor of the European Rocketry Challenge (EuRoC), these flight computers have become integral to the competition, providing reliable and sophisticated telemetry and control capabilities that enhance both safety and performance. The paper delves into the technical specifications and educational impact of these systems, highlighting their contribution to the broader European rocketry programmes. Through comprehensive field data and case studies from the recent European Rocketry Challenge, this study underscores the potential of open-source flight computers to inspire the next generation of aerospace professionals.
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Cosmology and Nongalactic Astrophysics

Dark Energy Survey Year 3 results: Simulation-based $w$CDM inference from weak lensing and galaxy clustering maps with deep learning: Analysis design

A. Thomsen, J. Bucko, T. Kacprzak et al. (+99 more)

Data-driven approaches using deep learning are emerging as powerful techniques to extract non-Gaussian information from cosmological large-scale structure. This work presents the first simulation-based inference (SBI) pipeline that combines weak lensing and galaxy clustering maps in a realistic Dark Energy Survey Year 3 (DES Y3) configuration and serves as preparation for a forthcoming analysis of the survey data. We develop a scalable forward model based on the CosmoGridV1 suite of N-body simulations to generate over one million self-consistent mock realizations of DES Y3 at the map level. Leveraging this large dataset, we train deep graph convolutional neural networks on the full survey footprint in spherical geometry to learn low-dimensional features that approximately maximize mutual information with target parameters. These learned compressions enable neural density estimation of the implicit likelihood via normalizing flows in a ten-dimensional parameter space spanning cosmological $w$CDM, intrinsic alignment, and linear galaxy bias parameters, while marginalizing over baryonic, photometric redshift, and shear bias nuisances. To ensure robustness, we extensively validate our inference pipeline using synthetic observations derived from both systematic contaminations in our forward model and independent Buzzard galaxy catalogs. Our forecasts yield significant improvements in cosmological parameter constraints, achieving $2-3\times$ higher figures of merit in the $\Omega_m - S_8$ plane relative to our implementation of baseline two-point statistics and effectively breaking parameter degeneracies through probe combination. These results demonstrate the potential of SBI analyses powered by deep learning for upcoming Stage-IV wide-field imaging surveys.
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All authors A. Thomsen, J. Bucko, T. Kacprzak, V. Ajani, J. Fluri, A. Refregier, D. Anbajagane, F. J. Castander, A. Ferté, M. Gatti, N. Jeffrey, A. Alarcon, A. Amon, K. Bechtol, M. R. Becker, G. M. Bernstein, A. Campos, A. Carnero Rosell, C. Chang, R. Chen, A. Choi, M. Crocce, C. Davis, J. DeRose, S. Dodelson, C. Doux, K. Eckert, J. Elvin-Poole, S. Everett, P. Fosalba, D. Gruen, I. Harrison, K. Herner, E. M. Huff, M. Jarvis, N. Kuropatkin, P.-F. Leget, N. MacCrann, J. McCullough, J. Myles, A. Navarro-Alsina, S. Pandey, A. Porredon, J. Prat, M. Raveri, M. Rodriguez-Monroy, R. P. Rollins, A. Roodman, E. S. Rykoff, C. Sánchez, L. F. Secco, E. Sheldon, T. Shin, M. A. Troxel, I. Tutusaus, T. N. Varga, N. Weaverdyck, R. H. Wechsler, B. Yanny, B. Yin, Y. Zhang, J. Zuntz, M. Aguena, S. Allam, F. Andrade-Oliveira, D. Bacon, J. Blazek, D. Brooks, R. Camilleri, J. Carretero, R. Cawthon, L. N. da Costa, M. E. da Silva Pereira, T. M. Davis, J. De Vicente, S. Desai, P. Doel, J. García-Bellido, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. J. James, K. Kuehn, O. Lahav, S. Lee, J. L. Marshall, J. Mena-Fernández, F. Menanteau, R. Miquel, J. Muir, R. L. C. Ogando, A. A. Plazas Malagón, E. Sanchez, D. Sanchez Cid, I. Sevilla-Noarbe, M. Smith, E. Suchyta, M. E. C. Swanson, D. Thomas, C. To, D. L. Tucker