Instrumentation and Methods for Astrophysics
A numerical framework for Newtonian-noise estimation at the Einstein Telescope: 2-D simulations beyond the plane-wave approximation
Patrick Schillings, Shi Yao, Johannes Erdmann et al. (+1 more)
The Einstein
Telescope (ET) is a third-generation underground gravitational-wave observatory designed to extend the detection sensitivity down to a few Hertz. Newtonian noise is expected to limit the low-frequency sensitivity of ET, particularly in the 3-15 Hz band. Most existing estimates rely on analytical or semi-analytical models assuming homogeneous or layered media, neglecting geological heterogeneity and complex wave interactions. In this work, we present a numerical framework for Newtonian-noise estimation based on spectral-element simulations of a seismic wave field. As a proof of concept, we first
benchmark the numerical results against analytical plane-wave predictions in a two-dimensional homogeneous medium with a single surface source, demonstrating excellent agreement for both bulk and cavern contributions. We then extend the model to an array of 30
stochastic surface sources to approximate stationary ambient seismic excitation. The P-wave fraction inferred from the simulated wave field is, in this simple homogeneous case, significantly lower than commonly assumed, indicating enhanced prospects for Newtonian-noise mitigation. The framework is readily applicable to three-dimensional simulations and to integration of detailed local seismic models and topography, offering strong potential for site-specific Newtonian-noise estimation.
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All authors Patrick Schillings, Shi Yao, Johannes Erdmann, Andreas Rietbrock
Cosmology and Nongalactic Astrophysics
When One-Parameter Dark Energy Makes Neutrinos Physical Again
Weiqiang Yang, Eleonora Di Valentino, Eric V. Linder et al. (+2 more)
A puzzling implication of current data interpreted in the $\Lambda$-Cold Dark Matter cosmology is the preference for a negative sum of
neutrino masses. Moving to $w_0w_a$CDM brings an appreciable fraction of the
neutrino mass posterior back to positive values, while the constant equation-of-state dark energy case $w$CDM does not. We investigate a variety of one-parameter dynamical dark energy equations of state (DE EoS) whose
redshift evolution is controlled by a single free parameter, each representing distinct physical properties, to understand whether a two-parameter DE EoS is required to bring the
neutrino mass into the positive region. The conclusion is that certain one-parameter DE EoS can suffice, implying that the data are pointing toward physical characteristics rather than a broad degeneracy. This behavior effectively lowers the dark energy density at high
redshift, allowing the sum of
neutrino masses to shift toward the physical region. The required characteristics are identified as phantom dark energy at high
redshift, crossing $w=-1$ at lower
redshift.
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All authors Weiqiang Yang, Eleonora Di Valentino, Eric V. Linder, Sibo Zhang, Supriya Pan
Earth and Planetary Astrophysics
A Panchromatic JWST Spectrum of a Giant Starspot on the Fully Convective M-dwarf TOI-3884
C. A. Murray, L. Garcia, B. V. Rackham et al. (+18 more)
TOI-3884 b is a rare super-Neptune transiting a fully convective M
dwarf that hosts a persistent
giant polar spot. Because the
planet occults this active region during every transit, the system offers a unique laboratory to directly probe the
stellar surface and spot properties. We present seven James Webb Space
Telescope (JWST) transits of TOI-3884 b observed with NIRISS and NIRSpec (spanning 0.6–5.3$\mu$m). While all visits show a recurring spot-crossing signature, each transit exhibits a distinct spot-crossing morphology, enabling us to infer a
stellar rotation period of $P$=11.102$\pm$0.003d and tightly constrain the pole-on
stellar orientation ($i_{*}$=139.2$\pm$0.3$^{\circ}$, $\lambda_{*}$=31.1$\pm$0.4$^{\circ}$) and spot properties ($R_{\rm{spot}}=0.576^{+0.006}_{-0.005}$R$_{*}$, $\phi_{\rm{spot}}$=-84.69$\pm$0.12$^{\circ}$).We leverage this orbital configuration to measure the first empirical panchromatic spectrum of an M
dwarf starspot with JWST, establishing a direct observational
benchmark for
stellar atmosphere models in the fully convective regime. Comparison with 1D NewEra and SPHINX atmosphere models indicates that the spot is 183$\pm$1K cooler than the photosphere, consistent with previous ground-based measurements and expectations for mid M
dwarf spot contrasts. While the models reproduce the observed contrasts at wavelengths longer than 1$\mu$m, they significantly underpredict the contrasts at shorter wavelengths. These results demonstrate that M
dwarf stellar atmosphere models may not fully capture the wavelength dependence of
stellar contamination in transmission spectra and highlight the importance of empirical spot spectra for robust interpretation of planetary atmospheres, particularly in the optical.
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All authors C. A. Murray, L. Garcia, B. V. Rackham, Z. Berta-Thompson, A. D. Feinstein, S. J. Mercier, B. Charnay, L. Hebb, J. E. Libby-Roberts, Y. Rotman, A. Stephens, M. Timmermans, L. Welbanks, K. Barkaoui, Caleb I. Canas, M. Delamer, E. Ducrot, S. Kanodia, S. Mahadevan, J. P. Ninan, J. de Wit
Cosmology and Nongalactic Astrophysics
Wasserstein Distance in Cosmological Structure Formation: An Optimal Transport Perspective
Tsutomu T. Takeuchi
Cosmological large-scale structure is usually characterized by statistics such as the power spectrum and correlation function, which describe fluctuation amplitudes but not the spatial redistribution of matter. We formulate structure formation as a transport problem between mass distributions using the Wasserstein distance of optimal transport theory. The generative process from the initial linear density field to an observed
galaxy catalog is represented as a hierarchical mapping from a continuous matter field to a
galaxy point process. Under the small-fluctuation approximation, we derive an approximate Wasserstein distance that decomposes into three physically distinct contributions: gravitational mass transport,
galaxy formation bias, and shot noise from discrete
galaxy sampling. The gravitational term is expressed as an integral of the matter power spectrum, whereas the
galaxy formation term is given by a transport-weighted integral of the
galaxy correlation function. The sampling term reduces to Poisson shot noise. Unlike conventional volume-weighted clustering statistics, the correlation contribution measures cumulative matter displacements and is naturally connected to
baryon acoustic oscillation smearing. This framework provides a transport-
geometric description of large-scale structure formation and introduces the Wasserstein distance as a statistical link between continuous density fields and observed
galaxy catalogs.(abridged)
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Cosmology and Nongalactic Astrophysics
Calibrating spectral siren cosmology with synthetic catalogs of binary black hole mergers
Arianna Scarpa, Simone Mastrogiovanni, Filippo Santoliquido et al. (+2 more)
Binary black hole (BBH) mergers detected through Gravitational Waves (GWs) are a promising probe for the
cosmic expansion. These sources are standard sirens for which we can directly measure the luminosity distance, but their
redshift is degenerate with the determination of their source masses. In analogy to standard candles, the
redshift of standard sirens can be obtained using a calibration based on the source mass spectrum, but without the need for a cosmological ladder. The modelling of the BBH mass spectrum is crucial for GW cosmology. In this paper, we propose a new pipeline based on Normalizing Flows to calibrate population models on synthetic BBH catalogs generated from astrophysical prescriptions. Although these models are less flexible than the current parametric models used in the literature, they have the advantage of directly capturing the correlations between BBH mass and
redshift and provide a direct link between different formation channels and cosmological parameter inference. We discuss potential applications and limitations of this method using the B-POP code to generate a mock catalog that contains BBH formed by isolated
stellar binaries and in dense
stellar environments via dynamical interactions. Using this methodology, we show that B-POP provides a good fit for the mass and
redshift distributions of the GW events in GWTC-4.0 data for a flat $\Lambda$CDM cosmology with $H_0 \sim 70 km/s/Mpc$ and $\Omega_m=0.308$. We also find a correlation between $H_0$ and the fraction of binaries produced by the dynamical and isolated formation channels arising from the fact that dynamically formed binaries populate the higher side of the mass spectrum.
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All authors Arianna Scarpa, Simone Mastrogiovanni, Filippo Santoliquido, Manuel Arca-Sedda, Giovanni Antinozzi
Solar and Stellar Astrophysics
IRAM 04191+1522: a compact proto-brown dwarf binary candidate
N. Huélamo, I. de Gregorio-Monsalvo, Aina Palau et al. (+12 more)
Very low-luminosity objects in nearby
star-forming regions have been identified as promising proto-brown
dwarf candidates. The study of their multiplicity can shed light on the dominant formation mechanism of these substellar objects. We aim at studying the multiplicity of the very low luminosity object IRAM 04191+1522. To do so, we have obtained 0.89mm ALMA observations with a very extended configuration, achieving an angular resolution of ~0.04 arcsec (6 au at 140 pc). We have complemented our data with new VLA observations, and ALMA archival data at 1.3mm. As a result, we resolve IRAM04191+1522 into a close binary candidate for the first time. The binary is detected in the ALMA continuum data with a projected separation of ~80 mas, or 11 au at a distance of 140 pc. The two sources are oriented in the East-West direction, with the eastern component being brighter and more extended than the western one, which is marginally resolved. The analysis of C18O(2-1) archival data reveals gaseous material in rotation around the binary, presumably from a circumbinary disk with ~27 au of radius centered on the faintest ALMA component. A fit of the position-velocity diagram allows us to estimate a total dynamical mass for the system of 50+-40 MJup. Therefore, we classify IRAM04191 as a tight proto-brown
dwarf binary candidate. The VLA data reveals the detection of a single object closer to the western ALMA source, and with a spectral index consistent with a
radio jet.
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All authors N. Huélamo, I. de Gregorio-Monsalvo, Aina Palau, C. Carrasco-González, A. Ribas, H. Bouy, R. Pandey, D. Barrado, N. Otten, V.D. Ivanov, M.F. Sterzik, M. Dunham, L. A. Zapata, E. Pantin, E. Macías
High Energy Astrophysical Phenomena
Cosmic rays: constraints from future MeV detectors
Giada Peron, Sarah Recchia, Stefano Menchiari et al. (+4 more)
Cosmic rays are charged energetic particles that permeate the interstellar medium. Their sizeable energy share and penetration power makes them essential players in the dynamical and chemical processes that rule
Galactic evolution, such as the launching of
outflows and the formation of
star and
planets. For these processes low-energy (MeV-GeV) CRs are particularly important, both because they are the most abundant and because they have the largest cross-section for ionization. The study of
cosmic rays naturally connects with gamma-ray astronomy, as high-energy
photons are the principal products of their interaction with the interstellar
plasma. In this article, after reviewing our current understanding of
Galactic cosmic rays as derived from direct measurements, we present the state of the art regarding
Galactic cosmic rays covering their direct observables, their acceleration processes and models for their propagation in the
Galactic Disk. We present then an excursus on the current state of gamma-ray observations, and propose new prospects for investigating the physical properties of
Galactic cosmic rays, exploiting the observational capability of future MeV missions.
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All authors Giada Peron, Sarah Recchia, Stefano Menchiari, Alexandre Marcowith, Andrei Bykov, Martin Pohl, Elena Amato
Astrophysics of Galaxies
Molecular gas and star formation in GASP jellyfish galaxies
A. Moretti, R. Paladino, C. Bacchini et al. (+13 more)
Several studies have reported a nearly linear correlation between the molecular gas and
star formation rate surface density, the so-called Kennicutt-Schmidt (KS) law. We aim to retrieve the KS relation for a sample of four
star-forming
galaxies located in nearby clusters, disturbed by the effects of the ram pressure stripping, as testing this law in
galaxies subject to different environmental conditions can provide key information on the physics of
star formation. To perform our analysis, we used ALMA band 6 and band 3 data coupled with MUSE data at spatial resolution of ~1 kpc. Moreover, we analyzed data of
star-forming complexes detected through their H\alpha ionized gas emission. We also derived the
star formation efficiencies of the
star-forming regions nested in these big complexes using the
star formation rates derived from spatially resolved HST images and various recipes for the corresponding cold gas phase. We find that ram-pressure-stripped
galaxies show normal-to-low
star formation efficiencies, depending on the position within the
galaxy and on the local gas density: the inner dense regions in the disk show higher efficiencies with respect to the outer regions, including the gaseous tails. The global relation between the
star formation rate density and the molecular gas surface density is superlinear, likely suggesting the shortening of the depletion times at high gas mass densities caused by the ram pressure. Within the
star-forming complexes, the
star formation efficiency is very similar to the one observed at 1 kpc scale in undisturbed
star-forming disks. Interestingly, this result holds also for the
star-forming complexes located in the stripped gas tails. The analysis of HST resolved clumps suggests that the molecular gas is not uniformly distributed within the
star-forming complexes, but its density distribution follows a steeper profile.
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All authors A. Moretti, R. Paladino, C. Bacchini, A. Marasco, E. Giunchi, B. M. Poggianti, L. K. Hunt, T. Deb, B. Vulcani, M. Gullieuszik, A. Lassen, A. Wolter, M. Gitti, M. Radovich, J. Fritz, N. Tomicic
Astrophysics of Galaxies
Towards physically more comprehensive AGN modelling in cosmological simulations: A MACER-based modification of IllustrisTNG
Bocheng Zhu, Volker Springel and Feng Yuan
Active
galactic nuclei (AGN) feedback plays a significant role in many aspects of
galaxy formation and
evolution and has become a key ingredient in cosmological simulations. However, the subgrid models of AGN feedback in cosmological simulations such as IllustrisTNG (hereafter TNG) often overlook recent progress in the small-scale modelling of black hole (BH)
accretion and AGN physics. In this study, we improve on this by incorporating central aspects of the MACER model, a framework that treats AGN physics in greater detail, into the TNG feedback implementation. Specifically, we adopt MACER-prescriptions for feedback output for high and low
accretion rates in a new model while the estimation of the
accretion rate remains unchanged. We test this updated scenario both for idealized elliptical
galaxies and for a cosmological box. Compared to the original TNG model, the MACER-based simulation leads to a higher
star formation rate (SFR) and BH
accretion rate in ellipticals, yielding a gas density profile in better agreement with observations. In the cosmological simulations, the time
evolution of the SFR density,
galaxy stellar mass function at $z=0$, and $M_{\star}-M_{\rm BH}$ relation at $M_{\star}>10^{10.5}\,{\rm M_{\odot}}$ are similar in both models. The MACER model better reproduces low-mass BHs in low-mass
galaxies, and yields milder quenching in massive
galaxies, although this is accompanied by the absence of a pronounced colour bimodality. Still, the similarity of the outcomes underlines the self-regulated nature of BH feedback: for different feedback energetics, the
accretion rate tends to adjust such that a similar total AGN feedback energy is released.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.app-ph
An efficient finite element formulation for Newtonian noise analysis
Pieter Reumers, Xhorxha Kuci, Stijn François et al. (+1 more)
The Einstein
Telescope is a third-generation underground gravitational wave observatory designed to achieve an unprecedented sensitivity down to 3 Hz. Waves propagating in the soil due to anthropogenic or natural vibration sources generate density fluctuations which cause gravitational attraction, resulting in motion of the mirrors of the
laser interferometer known as Newtonian noise. A finite element formulation is presented, which evaluates the total Newtonian noise, as well as the bulk and surface contributions, from a seismic wave field defined on a finite element mesh, using Gaussian quadrature. Linear and quadratic tetrahedral (4-node and 10-node) and brick (8-node and 20-node) finite elements are supported. The corresponding volume and surface integrals are expressed in terms of finite element coupling
matrices that depend only on the geometry and material properties. The formulation is verified for plane P- and S-waves propagating in an elastic homogeneous full space with a mirror suspended in a spherical cavity, assuming that the wavelength is much larger than the radius of the cavity, so that wave scattering can be ignored. Excellent agreement with analytical solutions is obtained. Similar good agreement is reported for the Newtonian noise on a test mass suspended at a finite distance above the free surface of a homogeneous elastic halfspace in which a Rayleigh wave propagates. The methodology has been implemented in the ANNA Newtonian Noise Analysis toolbox which runs in the MATLAB programming and numeric computing platform and is compatible with the open-source GNU Octave Scientific Programming
Language; a Python version is also available. The proposed finite element framework provides a physically consistent and computationally efficient approach for computing gravitational-seismic coupling in heterogeneous media.
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All authors Pieter Reumers, Xhorxha Kuci, Stijn François, Geert Degrande
Astrophysics of Galaxies
The extinction distances for over a thousand planetary nebulae with Gaia measurements
Juan Deng, Shu Wang, Biwei Jiang et al. (+1 more)
Although
Gaia has identified the central
stars of planetary nebulae (CSPNe) for about 70% of known
Galactic planetary nebulae (PNe), reliable distance estimates remain incomplete, with fewer than one quarter having accurate parallaxes. Meanwhile, classical extinction-distance samples include only about 70 objects, corresponding to 1.8% of the
Galactic PN population. We aim to construct a large and homogeneous catalogue of PN distances by refining extinction-distance measurements with
Gaia DR3, providing an independent complement to CSPN parallax-based distances. We develop a
Gaia-based extinction-distance method by combining an improved blue-edge approach with an extinction-jump model. PN distances are derived from
stellar extinction jumps in line-of-sight extinction-distance profiles and are further constrained by comparisons with published distances, the spatial distribution of
stars relative to the PN centre, and the PN radius-distance relation. We obtain distances for 1,066 PNe with a median relative uncertainty of 13%, with about 87% of the sample having uncertainties below 20%. The catalogue includes 765 PNe whose CSPN parallaxes have uncertainties greater than 20% and 128 PNe without CSPN parallaxes. This method complements CSPN parallax-based approaches and extends the traditional extinction-based method to higher
Galactic latitudes. For PNe with discrepant literature distances, it helps identify the more reliable estimates and assess CSPN identifications. We find a likely misidentification of the reported CSPN for Fr2-36 and analyse 33 PNe with two CSPN candidates, suggesting improved identifications for 15 objects. This catalogue represents the largest homogeneous set of extinction-based PN distances to date and provides a robust
benchmark for studies of
Galactic structure, PN populations, and interstellar extinction.
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All authors Juan Deng, Shu Wang, Biwei Jiang, Licai Deng
Astrophysics of Galaxies
Can cyanide radicals drive molecular backbone growth on interstellar icy grains?
Germán Molpeceres and Joan Enrique-Romero
Motivated by the value of CN-bearing molecules as tracers of interstellar physical conditions, we investigate the reactions of adsorbed CN radicals with acetylene and ethylene (C2H2 and C2H4) on interstellar
dust-grain analogues using
quantum chemical calculations. We find that reactivity is strongly controlled by the relative orientation of the reactants, with specific geometries either promoting or inhibiting reaction. We further show that, on ice, these reactions differ qualitatively from their gas-phase counterparts, stalling at the formation of the adduct complexes C2H2CN and C2H4CN and exhibiting newly emerged kinetic barriers for the neutral-radical association. We contextualize our calculations in the same reaction-
diffusion framework that would be employed in astrochemical models, finding that, depending on the
diffusion energy of the hydrocarbons, these reactions can be either negligible or efficient, highlighting the importance of the local ice structure in interstellar grain chemistry. These findings caution against the use of CN-based tracers that assume barrierless, bimolecular surface reactions involving CN radicals.
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Solar and Stellar Astrophysics
A New Catalogue of Galactic Red Supergiants for direct detection of episodic mass-loss events
M. Lauriano, F. Bocchino, M. Miceli et al. (+5 more)
We present GalRSG, a new catalogue of 227
Galactic Red Supergiants in the Scutum-Crux region, which provides a nearly coeval and co-distant sample, target of a long-term, panchromatic, high-cadence photometric monitoring campaign aimed at detecting pre-
supernova variability and luminous eruptively driven mass-loss events.
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All authors M. Lauriano, F. Bocchino, M. Miceli, S. Orlando, O. Petruk, A. Pastorello, M. Limongi, A. Chieffi
Astrophysics of Galaxies
Path Measures for Stochastic Galaxy Formation on Layered Halo Graphs
Daneng Yang
Galaxy formation, viewed as an inference problem from incomplete information, is inherently
stochastic. Reducing the full simulation state to a coarse-grained set of variables integrates out unresolved degrees of freedom, motivating an effective
stochastic description of
galaxy formation in reduced variables. Existing approaches have achieved substantial predictive success, but generally lack a unified statistical framework for trajectory-level
galaxy assembly and history-conditioned fluctuations. We introduce a Graph Path Likelihood Model that formulates
galaxy assembly histories as
stochastic dynamical trajectories on hierarchical
halo merger graphs, where temporal edges encode causal transport and coeval host edges encode environmental conditioning. Within this formulation,
galaxy evolution is described by graph-conditioned path measures and effective actions, from which observables, likelihoods, and response diagnostics emerge from a common probabilistic description. As a first realization, we train a graph neural likelihood model for
stellar and gas mass assembly histories on layered
halo graphs extracted from hydrodynamic simulations. We show that it reproduces the main statistics of these histories while capturing environmentally conditioned correlated fluctuations. The path measure formulation also provides a natural setting for example fixed-graph applications, which we illustrate with the fraction of dark-matter-deficient
galaxies, controlled gas-response deformations, and nonequilibrium diagnostics of environmentally dependent
evolution. In particular, the present construction also admits extensions in which merger-history statistics and baryonic
evolution are treated within a unified probabilistic description, potentially enabling studies of how graph structure, assembly histories, and
galaxy observables respond jointly to variations in the underlying theory.
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High Energy Astrophysical Phenomena
Do the sources of the 511 keV excess explain the anomalous CMZ ionization?
Pedro De la Torre Luque and Francesca Calore
The anomalous rate of molecules ionization observed at the Central Molecular zone (CMZ) challenges known mechanisms of ionization observed in molecular clouds across the
Galaxy, due to the exceptionally high levels of ionization measured (orders of magnitude above what
cosmic rays can explain) and its uniform spatial distribution within the CMZ. Recent studies suggest that the source of the $511$~keV excess can be correlated with this anomalous ionization rate or contribute significantly to the ionization in the
Galactic Centre (GC). One of the leading hypotheses attributes the $511$~keV signal to positron injection from radionuclides or
pulsars distributed following the
stellar bulge, which is rather flat around the GC and, hence, could help explaining the uniform ionization profile. In this work, we investigate whether such a population of sources, injecting MeV positrons at rates consistent with the $511$~keV observations, can account for the ionization levels and distribution observed in the CMZ. Our results indicate that positron injection alone falls short at explaining the anomaly, although their expected ionization is larger than expected from any previously studied candidates.
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Instrumentation and Methods for Astrophysics
Combining data and metadata: hybrid tabular file formats
Mark Taylor
When working with astronomical data, metadata is also important. A general-purpose file format for transmission, processing and archiving large
datasets should facilitate, among other things, both efficient processing of bulk data and encoding of rich semantic metadata. When choosing a format for a particular purpose sometimes no existing format satisfies both these requirements adequately, but combining one data-efficient and one metadata-rich format can be made to do so. This paper discusses considerations for designing such hybrid data/metadata formats, and reviews some examples such as VOParquet, FITS-plus and ECSV. We focus on tabular data, but some of the considerations may apply to other datatypes such as arrays as well.
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Cosmology and Nongalactic Astrophysics
Luminosity-Temperature Relation as a Probe for Modified Gravity
Antonino Del Popolo, Saeed Fakhry and David F. Mota
We investigate the luminosity-temperature ($L$-$T$) relation of
galaxy clusters as a probe for testing modified
gravity (MG) theories, focusing on $f(R)$
gravity and symmetron models. Using an improved semi-analytic framework that incorporates angular momentum acquisition, dynamical friction, and shock heating within the modified punctuated
equilibrium model, we compare predictions against hydrodynamical simulations and observational data. While massive clusters remain largely screened and follow standard $\Lambda$CDM predictions, low-mass systems ($kT \lesssim 1-2$ keV) exhibit systematic deviations characterized by steeper $L$-$T$ slopes in MG scenarios. Crucially, we demonstrate that these signatures cannot be mimicked by conventional astrophysical processes such as feedback or angular momentum effects, which primarily affect normalization rather than
curvature. Our results establish the $L$-$T$ relation as a robust diagnostic tool for distinguishing general relativity from screened MG theories, with the strongest discriminatory power emerging at group scales accessible to current and future X-ray surveys. Moreover, a normalized reduced $\chi^2$ analysis of the $L$-$T$ relation shows that MG models provide significantly better agreement with observational data than $\Lambda$CDM, with several realizations achieving excellent fits while the $\Lambda$CDM model consistently performs worst.
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Astrophysics of Galaxies
CIV wind properties of the SDSS-V X-ray selected quasars: strong optical-to-UV emission is key regardless of X-ray strength
Amy L. Rankine, David Homan, James Aird et al. (+25 more)
We present an investigation of the rest-frame optical/UV and X-ray properties for a sample of 3027 X-ray selected
quasars between $1.5 \leq z \leq 3.5$ detected in the deepest Spectrum Roentgen Gamma/eROSITA data available and observed by the fifth iteration of the Sloan Digital Sky Survey (SDSS-V). We parametrize the CIV$\lambda1549$ emission line to infer the strength of
accretion disc winds and perform X-ray spectral fitting. The X-ray spectral properties – namely, the 2keV monochromatic luminosity (L$_\text{2keV}$) and spectral slope – are not strongly correlated with wind strength. Despite this result, the X-ray selected sample is shifted towards lower CIV blueshifts and higher equivalent widths than the optically selected sample observed in previous SDSS surveys, and matching in optical luminosity,
redshift, and Eddington ratio does not reduce these differences. We estimate the far-UV luminosity using the HeII$\lambda1640$ line luminosity and define the slopes between this and the 2500A monochromatic luminosity ($L_{2500}$) and L$_\text{2keV}$ ($\alpha_\text{ouv}$ and $\alpha_\text{uvx}$, respectively) in a similar manner to the familiar $\alpha_\text{ox}$ parameter, which tracks the spectral slope between $L_{2500}$ and L$_\text{2keV}$. The quantity $\alpha_\text{ouv}$ is more strongly correlated with wind strength in our sample than $\alpha_\text{ox}$. We show that the correlation between $\alpha_\text{ox}$ and wind strength is driven by the relationship between the optical luminosity and wind strength. Our results are consistent with a radiation line-driven wind, whereby the ionising far-UV
photons must not over-ionise the gas. The hard X-ray
photons are few enough in number to have a negligible effect on the ionisation state of the material.
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All authors Amy L. Rankine, David Homan, James Aird, Pranavi Hiremath, Scott F. Anderson, Roberto J. Assef, Franz E. Bauer, W. N. Brandt, Marcella Brusa, Johannes Buchner, Maria Chira, Yaherlyn Díaz, Patrick B. Hall, Anton M. Koekemoer, Mirko Krumpe, Georg Lamer, Teng Liu, Sean Morrison, Blessing Musiimenta, C. A. Negrete, Qingling Ni, Paola Rodríguez Hidalgo, Mara Salvato, Donald P. Schneider, Yue Shen, Matthew J. Temple, Dusán Tubín-Arenas, Dominika Wylezalek
Instrumentation and Methods for Astrophysics
Circuit Modeling for In Situ 21 cm Radiometer Calibration
Gary Vincent Charles Allen, Saurabh Pegwal, Dirk de Villiers et al. (+42 more)
Recent experiments in cosmology, particularly those aimed at detecting the faint, redshifted, global 21 cm hydrogen line (depth < ~200 mK, z > 7.5), have imposed stringent new requirements on radiometer calibration. In this work, we present a framework for
circuit modeling and parameter inference to strengthen these calibration pipelines. This new approach enables in situ characterization of otherwise immeasurable systematics using physically motivated models. A combination of frequentist and
Bayesian techniques are employed in a pipeline that supports iterative modeling, robust parameter estimation, and detailed uncertainty quantification. The framework is applied to the REACH
telescope, where the precise correction of variations in the
radio signal paths arising from component aging or environmental effects is critical.
Circuit models of REACH's calibration sources are developed, with the goal of predicting source temperature corrections that are conventionally obtained from laboratory measurements. By fitting the models to measured data using a convolutional cost function, a strong agreement with RMS residuals no worse than -37 dB is obtained. However,
Bayesian inference reveals that the resulting temperature corrections can have uncertainties on the order of 1 to 2 K, caused by reflection coefficient degeneracies, measurement noise, and errors in the models. To combat this, posteriors obtained from laboratory measurements are employed as updated priors, reducing correction uncertainties down to 75 mK. Ultimately, the framework provides a means of dynamically accounting for drift in system non-idealities over time, addressing the increasing precision demands of global 21 cm
radio astronomy.
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All authors Gary Vincent Charles Allen, Saurabh Pegwal, Dirk de Villiers, Dominic Anstey, Kaan Artuc, Harry Bevins, Gianni Bernardi, Martin Bucher, Steve Carey, Jean Cavillot, Ricardo Chiello, Adele Chu, Wessel Croukamp, John Cumner, Ardash Dash, Saswata Dasgupta, Eloy de Lera Acedo, Jiten Dhandha, Aleksandra Dragovic, John Ely, Anastasia Fialkov, Thomas Gessey-Jones, Will Handley, Christian Kirkham, Girish Kulkarny, Samuel Leeney, Alessio Magro, Daan Meerburg, Shikhar Mittal, Daniel Molnar, Rohan Patel, Joe Pattison, Carla Pieterse, Jonathan Pritchard, Gabriella Rajpoot, Nima Razavi-Ghods, Daniel Robins, Ian Roque, Anchal Saxena, Killian Scheutwinkel, Paul Scott, Emma Shen, Peter Sims, Marta Spinelli, Jiacong Zhu
Solar and Stellar Astrophysics
The Chandrasekhar's Conditions as Equilibrium and Stability of Stars in a Universal Three-Parameter Non-Maxwell Distribution
Wei Hu and Jiulin Du
The idea of the Chandrasekhar's conditions as
equilibrium and stability of
stars is revisited with a new universal three-parameter non-Maxwell distribution. We derive the maximum radiation pressures in the non-Maxwell distribution for a gas
star and a centrally-condensed
star, respectively, and thus we generalize the Chandrasekhar's conditions in a Maxwellian sense. By numerical analyses, we find that the non-Maxwellian distribution usually reduces the maximum radiation pressures in both a gas
star and a central condensed
star as compared with that cases if the gas is assumed to be a Maxwellian distribution.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Parametrizing superfluid dark matter with rational approximations
Francesco Lottatori
We investigate how a spatially modulated real scalar background $\phi(\vec{x})$ can modify
phonon propagation in the context of Superfluid dark matter (SFDM). Using a simple toy model with quartic condensate and coupling $-g\phi^2|\Psi|^2$, we derive the local equation of state and the effective sound velocity $c_s(\vec{x})$. For $g>0$, modulation tends to increase the effective mass of the condensate and make the medium less rigid, suppressing $c_s^2\propto m_{\Psi,\mathrm{eff}}^{-4}$ up to a “
dust-like” regime, $c_s^2\to 0$. We implement this modulation for the background scalar field by imposing rational profiles, through Padé radial profiles, and show the corresponding variation of $c_s^2(r)$ for different $g$, discussing implications for the structure of SFDM cores and the possible formation of inhomogeneous regions of dark matter.
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Earth and Planetary Astrophysics
Predictions of Stellar Occultations by Haumea and the Event of 4 May 2026
José Luis Ortiz, Nicolas Morales, Antonio Ocaña-Pastor et al. (+8 more)
Haumea is the third-largest of the five officially recognized
dwarf planets and one of the four that reside in the trans-Neptunian region. It is among the most exotic bodies in the
Solar System, with an exceptionally rapid rotation, a highly elongated triaxial shape, and a ring that orbits about three times more slowly than Haumea itself. Because of its large heliocentric distance, direct exploration by dedicated space missions is not feasible in the short term, so progress must rely on ground- and near-Earth facilities.
Stellar occultations are among the most powerful tools to investigate trans-Neptunian objects. We present new predictions of
stellar occultations by Haumea and its ring for
stars down to
Gaia G = 21, and assess their scientific potential, with special emphasis on the 4 May 2026 event. We computed occultation opportunities for the coming years and evaluated the 4 May 2026 geometry in detail, including Haumea's rotation phase, known 3D shape, pole orientation, and sky-plane motion, to estimate the expected shadow-path width. Because the target
star has a very large
Gaia RUWE, we also carried out a dedicated reliability analysis, including speckle observations. We identify eleven valuable events through 2030. For 4 May 2026, we derive an expected sky-plane shadow width of $2224 \pm 30$ km, substantially larger than conservative nominal assumptions and therefore highly favorable for observations. Speckle imaging reveals a companion at $\sim 0.12$ arcsec and $\Delta m \sim 3.1$; this companion is also expected to be occulted and shifts the nominal main-
star path prediction on Earth by about 8 mas. These results confirm the strong scientific return expected from coordinated observations of upcoming Haumea occultations, especially the 4 May 2026 event, and provide an updated framework to improve constraints on Haumea's shape, density, ring properties, and environment.
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All authors José Luis Ortiz, Nicolas Morales, Antonio Ocaña-Pastor, José María Gómez-Limón, Steve B. Howell, Francisco J. Pozuelos, Pablo Santos-Sanz, Yucel Kilic, Gökhan Yücel, Rafael Morales, Mike Kretlow
Astrophysics of Galaxies
The ALMA-QUARKS Survey: Evidence of an Explosive Molecular Outflow in IRAS 15520–5234
Ariful Hoque, Tapas Baug, Estrella Guzman et al. (+25 more)
We present a study of the massive protocluster IRAS 15520$-$5234, which displays evidence of an explosive molecular
outflow that unleashed a kinetic energy of at least 10$^{48}$ erg. The protocluster contains 16 dense cores detected in the ALMA band 6 continuum emission maps, having masses in the range from 0.2 to 11.0 M$_{\odot}$. Our analysis of CO $(2-1)$ emission reveals 28 well collimated
outflow fingers, the majority of which follow a Hubble-Lemaître velocity law. The
outflow fingers show no preferred orientation in the plane of sky and emerge from a common center of origin. We estimate the total mass, momentum, and kinetic energy of the
outflow fingers and find that the values are at least one order of magnitude higher than the typical bipolar
outflows associated with massive protostars. The morphology and kinematics of the
outflow fingers suggest that the
outflow associated with IRAS 15520$-$5234 is explosive in nature. We calculate the dynamical age of the explosive event to be approximately 6550 years. Additionally, we estimate the frequency of such explosive
outflows in the
Galaxy, which is one event every 83 years. Finally, we speculate that the rearrangement of masses within the massive protocluster and the dynamical interaction among the massive cores may result in the formation of such an energetic event.
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All authors Ariful Hoque, Tapas Baug, Estrella Guzman, Manuel Fernandez Lopez, Tie Liu, Guido Garay, Paul F. Goldsmith, Fengwei Xu, Xindi Tang, Patricio Sanhueza, Lokesh K. Dewangan, Shivani Gupta, Sami Dib, Luis A. Zapata, Jihye Hwang, N. K. Bhadari, John Bally, Swagat Ranjan Das, Aiyuan Yang, Prasanta Gorai, Arup Kumar Maity, James O. Chibueze, Pablo García, Leonardo Bronfman, Xunchuan Liu, L. Viktor Tóth, Shehu Muhammad Usman, Kee-Tae Kim
Cosmology and Nongalactic Astrophysics
Inflation without an Inflaton III: non-Gaussian signatures
Mariam Abdelaziz, Marisol Traforetti, Daniele Bertacca et al. (+3 more)
We investigate
primordial non-Gaussianity in the Inflation without an Inflaton (IWI) framework, where scalar perturbations are generated at second order by
primordial gravitational waves in Einstein
gravity on an exact de Sitter (dS) background. Since scalar modes are produced nonlinearly from tensor modes, non-Gaussianity is an intrinsic prediction of the mechanism. We compute the corresponding scalar bispectrum, derive the relevant contribution to the three-point function of the scalar potential, and evaluate its shape numerically. We find that, unlike the scalar power spectrum, the bispectrum depends logarithmically on the ultraviolet cutoff set by the end of inflation, indicating a structural difference between the two- and three-point statistics in this scenario. Its shape is enhanced toward squeezed configurations, but its amplitude becomes strongly suppressed once the scalar power spectrum is normalized to the observed value. The resulting non-Gaussianity at CMB scales is therefore negligibly small, well below present observational sensitivity.
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All authors Mariam Abdelaziz, Marisol Traforetti, Daniele Bertacca, Raul Jimenez, Sabino Matarrese, Angelo Ricciardone
High Energy Astrophysical Phenomena
Investigating the Temporal Evolution of Gamma-Ray Burst Central Engine Parameters Based on Numerical Simulations
Wei-Hua Lei
A hyperaccreting
stellar-mass black hole (BH) has been proposed as the candidate central engine of gamma-ray bursts (GRBs). Comparing the predictions from the central engine models with the temporal behavior of GRBs is of great interest. In this paper, using the open-source GRMHD HARM-COOL code, we evolve several 2D magnetized hyperaccreting BH models with realistic equation of state in a fixed curved space-time background. We extend the code to include the calculation of
neutrino annihilation power. We then study the time
evolution of BH central engine parameters, i.e., the
neutrino annihilation power, the Blandford-Znajke (BZ) power, and the initial magnetization $\sigma_0$. We find that the
neutrino power is generally consistent with previous analytical results. Usually, the
neutrino annihilation process tends to launch a thermal “fireball”, while the BZ jet is Poynting-flux-dominated. Our results, especially the
evolution characteristics of $\sigma_0$ may help to understand the complex GRB spectral behavior.
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Solar and Stellar Astrophysics · Cross-listed from cond-mat.other
Measuring impurity-induced shifts in Coulomb crystallization
Mingyao Xu, Aaron A. Smith, Leonid Prokhorov et al. (+2 more)
We report a laboratory measurement of how
impurities shift Coulomb crystallization in a strongly interacting ionic system. This is achieved by using
laser cooled Ca$^+$
crystals doped with a controlled number of Xe$^{12+}$ highly charged ions. We find that the crystallization threshold is unchanged at low
impurity concentration, but shows a clear crossover once the
impurity content becomes sufficiently large, after which the shift grows approximately linearly. Complementary measurements reveal that this global effect originates from a local pinning of the
crystal around the
impurities. We further show how the measured shift could impact standard models of crystallization in white
dwarfs and
neutron stars. Our results provide an experimental route to incorporating
impurity effects into models of multicomponent Coulomb matter, relevant to
stellar crystallization and strongly coupled
plasmas.
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All authors Mingyao Xu, Aaron A. Smith, Leonid Prokhorov, Vera Guarrera, Giovanni Barontini
Earth and Planetary Astrophysics
Gravity from surface triangulation: convergence acceleration with nested grids
Jean-Marc Huré
The determination of the gravitational potential by the polyhedral method is revisited in the case where the surface of a body is composed of triangular facets. Based upon six test-shapes of astrophysical interest (sphere, spheroid, triaxial, lemon-shape, dumbell and
torus) projected on nested grids, we verify that the convergence toward reference values is second-order in the step size of the grid, inside the body, at the surface and outside. We then show that the accuracy or computing time can be drastically enhanced by implementing the Repeated Richardson Extrapolation. This technique is especially efficient when the body's surface is smooth enough, and is therefore well adapted to the theory of figures (single and multi-layer fluids) and to dynamical studies (test-particle and mutual interactions), which require a large number of field evaluations. For real objects like asteroids that have very irregular terrains at small scales, the gain is modest. In that context, we estimate the discretization level beyond which the typical error in potential values due to altimetric uncertainties dominates over the contribution of sub-grid cavities and bumps. For bodies close to spherical, the criterion reads $T \gtrsim \frac{64 D}{3 \lambda},$ where $D$ is the diameter of the body, $\lambda$ the typical shape error and $T$ the number of triangular facets involved. The case of 433 Eros is considered as an example.
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Astrophysics of Galaxies
Mapping of the Cold Neutral Medium via HI Phase Separation in an Atomic Cloud Undergoing Molecular Cloud Formation
Yamato Matsuzuki, Hiroaki Yamamoto and Kengo Tachihara
We investigate the atomic-to-molecular gas transition in the molecular cloud formation region HLCG 92-35 using GALFA-H I and NANTEN 12CO(J=1-0) observations. The HI spectra were decomposed into Cold Neutral Medium (CNM), Lukewarm Neutral Medium (LNM), and Warm Neutral Medium (WNM) components with the ROHSA
algorithm, and CNM structures were identified using Astrodendro. The derived HI mass ratio is CNM:LNM:WNM = 43:47:10, indicating that a substantial fraction of the gas resides in the intermediate-temperature phase. We identify 1792 CNM clumps with characteristic sizes of ~1-2 pc and average densities of ~ 80 cm^{-3}, broadly consistent with theoretical predictions for CNM structures formed through thermal instability. The CNM mass spectrum exhibits a power-law slope similar to that of CO clumps, suggesting that molecular clouds inherit the hierarchical structure established in the atomic phase. Significant non-thermal linewidths and localized CNM-CO velocity offsets imply that the CNM consists of small-scale cloudlets with distinct kinematic properties. These results provide observational support for a scenario in which small-scale CNM structures produced by thermal instability and turbulent flows represent an early stage of molecular cloud formation.
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Solar and Stellar Astrophysics
Probing the first generations of massive stars through fluorine in CEMP-no stars
Arthur Choplin and Georges Meynet
We investigate whether the first discovered fluorine-rich CEMP-no
star, CS 29498$-$043, can be explained by a very metal-poor rotating massive
star. We consider single rotating
stellar models of 20 $M_{\odot}$ at a
metallicity of $Z = 10^{-5}$, exploring initial rotation rates from $\upsilon_{\rm ini}/\upsilon_{\rm crit} = 0$ to $0.7$ in increments of $0.1$ ($0<\upsilon_{\rm ini}<644$ km s$^{-1}$). Rotational mixing enhances the production of light elements in the H–He layers, including fluorine. The ejected material can be nitrogen-rich without being fluorine-rich, whereas fluorine-rich ejecta are always predicted to be nitrogen-rich. The model providing the best fit to the abundances of CS 29498$-$043 is the $\upsilon_{\rm ini}/\upsilon_{\rm crit} = 0.6$ model ($\upsilon_{\rm ini} = 547$ km s$^{-1}$), which reproduces C, N, O, Na, Mg, and Al within the observational uncertainties. However, the predicted [F/Fe] $=2.8$ exceeds the observed value of [F/Fe] $=2.0 \pm 0.4$. By simultaneously varying the $^{15}$N($\alpha,\gamma$)$^{19}$F and $^{19}$F($\alpha,p$)$^{22}$Ne reaction rates within their acceptable ranges, the [F/Fe] ratio in the $\upsilon_{\rm ini}/\upsilon_{\rm crit} = 0.6$ model can be reduced to 2.2, providing a plausible solution to the abundance pattern of CS 29498$-$043. Our results support the hypothesis that fluorine-rich CEMP-no
stars may originate from material enriched by a single, metal-poor, rotating massive
star. A potential observational test of this scenario may be to check whether the nitrogen and fluorine abundances observed at the surface of CEMP-no
stars are correlated.
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High Energy Astrophysical Phenomena
Spectral Variations of $\gamma$-rays in Mrk 421
Rui-Qi Huang, Xin-Ke Hu, Yu-Wei Yu et al. (+2 more)
We present a comprehensive analysis of the 17-year
Fermi-LAT observational data of Mrk 421 to investigate the spectral variations in the $\gamma$-ray bands. The light curve of the source in the 0.1–1000 GeV band with a 14-day time bin exhibits significant variability at a confidence level exceeding 5$\sigma$, which is accompanied by spectral variation, displaying a harder-when-brighter behavior. Moreover, its flux variation can reach up to one order of magnitude within one day, with a daily flux up to $(1.19\pm0.84)\times10^{-8}~{\rm erg~cm^{-2}~s^{-1}}$ on MJD 56152. The 17-year integrated spectrum of Mrk 421 necessitates a complex model for explanation, whereas its time-resolved spectra over one-day or several-day time intervals can be well fitted by a power-law model. We propose that the complex spectral shape of the 17-year integrated spectrum stems from the superposition of different spectral shapes in different flux states. By generating the GeV spectra that are simultaneously observed with the archived TeV observations and constructing the combined GeV–TeV spectra, we find that some combined GeV–TeV spectral shapes clearly imply different radiation origins for the GeV and TeV emissions, challenging the one-zone leptonic model. It is found that the flux follows a lognormal distribution, while the
photon spectral index distributions can be well fitted by either a lognormal or a Gaussian functions. The possible nature of the $\gamma$-ray variability in Mrk 421 is discussed.
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All authors Rui-Qi Huang, Xin-Ke Hu, Yu-Wei Yu, Ji-Shun Lian, Jin Zhang