Solar and Stellar Astrophysics
Recovering Electron-Distribution Information from the Quiet-Sun Temperature Discrepancy
Victor Edmonds
Temperature diagnostics compress an electron distribution into a scalar. If two diagnostics weight different velocity ranges, their disagreement can retain information either discards. We develop this measurement for the quiet Sun, where
radio brightness and scale-height/ionization diagnostics read about 0.6 and 1.5 MK, a ratio of $2.4 \pm 0.3$ stable across eight years. For specified projections, an exact relative-
entropy identity partitions the discrepancy: the ratio fixes a family-independent temperature component; residual shape requires a family. Under the $\kappa$ family and stated projection assignments, the ratio gives $\kappa \approx 2.5$ and a free-energy equivalent of 10–20% of the electron thermal energy. An independent EIS within-ion Fe IX test is consistent with $\kappa = 2.5$–3, not confirmed; its confirm condition fired under neither calibration treatment. Under narrow-DEM conditioning, the Maxwellian residual is 2.8 times the conservative systematic floor. A published broad Maxwellian DEM restores spectroscopic consistency, but its material gives a class-level
radio-to-EUV cap of 1.21 against the measured class value $2.4 \pm 0.3$. Across all stated treatments, the Maxwellian fails at least one constraint in this class-level joint comparison; the records are neither co-temporal nor co-spatial. Conditional tests, not further evidence, find that the local Coulomb/runaway channel falls 39–56 times short and that a 1.8–3.5 keV stopping-column scale overlaps the inferred 1.7–3 keV sharp-edge bracket. Termination there remains a working hypothesis. The central result is the measurement construction: information lost to either temperature alone becomes recoverable from their disagreement. Direct shape confirmation requires a cross-class or distribution-resolving measurement.
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High Energy Astrophysical Phenomena
Same explosion, many faces: numerical modeling reveals viewing angle as a driver of diversity for core-collapse SNe in binary systems
Soham Mandal, Raphael Baer-way, Shazrene Mohamed et al. (+3 more)
Observable properties of core-collapse
supernovae (CCSNe) depend sensitively on the circumstellar material (CSM) formed by pre-explosion mass loss from the progenitor
star. Since a large fraction of CCSN progenitors reside in binaries, both the progenitor structure and surrounding CSM can be significantly impacted by binary interaction. Yet, its impact on the observed CCSN landscape remains poorly constrained. In this work, we investigate CCSNe from binary systems undergoing stable Roche lobe overflow. We construct a suite of binary
evolution models in MESA with a fixed initial primary mass ($16M_{\odot}$), exploring secondary masses in the range $12-15M_{\odot}$ and initial orbital periods $>500$ days. We generate three-dimensional (3D) CSM structures from the resulting mass-loss histories and orbital dynamics, extract angle-dependent density profiles along three lines of sight, and compute multi-band light curves with the radiation-hydrodynamics code Stella. We find that binary-driven CSM develops highly aspherical morphologies, governed by the orbital period and the mass ratio. Interaction between SN ejecta and this structured medium produces pronounced viewing-angle dependence in the light curves, with peak luminosities differing by factors of $\sim5$ and late-time $B-V$ colors varying by $\sim1.5$ mag depending on observer orientation. We further show that interpreting such events with one-dimensional frameworks assuming isolated progenitors and spherical winds can introduce biases up to $50\%$ for inferred explosion properties and $>200\%$ for inferred mass-loss rates. Our results are consistent with a substantial fraction of interacting Type II SN diversity arising from binary-shaped asymmetric CSM and viewing-angle effects, motivating multidimensional approaches to interpreting these transients.
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All authors Soham Mandal, Raphael Baer-way, Shazrene Mohamed, Irene Salmaso, Poonam Chandra, Maryam Modjaz
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Dynamical flattening of halo density cusps by Q-ball dark matter
Alexander Libanov and Sergey Troitsky
Cold, collisionless dark matter successfully explains a wide range of observations, including the formation of large-scale structure. Nevertheless, tensions remain on small,
galactic scales, most notably the cusp-core, or inner-mass-deficit, problem and the diversity of inner rotation-curve shapes and central densities at fixed
halo mass. These observations suggest that additional dark-sector physics may affect the inner structure of
halos, although no generally accepted explanation has yet emerged. Here, making use of a toy but representative model, we show that interacting dark-matter Q-balls – non-topological
solitons stabilized by a conserved charge – can provide a natural mechanism for
halo cusp flattening and may contribute to observed diversity of inner
halo profiles. Produced in the early Universe in the dark sector, these Q-balls grow in the dense central regions of
halos, while their interaction cross section decreases as the
soliton mass increases. This process operates preferentially in
halo centers, converting part of the rest-mass energy stored in massive Q-balls into relativistic dark-sector particles and thereby modifying the inner mass-density profile. The resulting density-dependent, self-regulating energy loss provides a dynamical mechanism for flattening
halo cusps while leaving the outer
halo largely unaffected.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.hist-ph
De mora luminis: Roemer's discovery 350 years later
Fabio Falchi, Riccardo Furgoni, Paolo Gattillo et al. (+1 more)
350 years from the 1676 announcement of the Roemer's discovery that light propagates with finite speed, we present our observations using eyes with
telescopes having similar resolution compared to those in the late 17th century. We confirmed that Roemer's method is valid and gives reasonable values for the speed of light c, within about 10 per cent of the modern value for our measurements, even with the simplest modelling technique, using uniform circular motions. We found that increasing the complexity of the model, e.g., by taking into account the elliptical orbit of Jupiter, does not necessarily bring the results closer to the value of c due to the influence of other perturbations. Using modern ephemerides yields a noticeably accurate result of c=(298200+-1900) km/s. This experience can have great didactic value by showing the interconnections between formulation of hypotheses and the consequent predictions, making observations, reducing data, and searching for alternative explanations for the same phenomenon. Lastly, we also found, in the correspondence between Roemer and Huygens, that Roemer in 1677 searched for an independent confirmation of what he found during previous years observing Io's eclipses by making observations and reducing the data of the meridian transits of the Great Red Spot on Jupiter.
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All authors Fabio Falchi, Riccardo Furgoni, Paolo Gattillo, Maurizio Francesio
High Energy Astrophysical Phenomena
Uncertainty-Aware Tidal Disruption Event Classification : A Host-Agnostic Probabilistic Random Forest Approach
Vysakh Anilkumar, Sjoert van Velzen, Marek Kowalski et al. (+1 more)
The classification of
Tidal Disruption Events in large-scale photometric surveys is challenging because deterministic machine learning models produce overconfident misclassifications under varying data quality and low signal-to-noise conditions. Existing lightcurve-based approaches fail to incorporate measurement uncertainties, consequently generating brittle outputs. We present a host-agnostic, uncertainty-aware classification framework using a Probabilistic Random Forest (PRF). Our pipeline extracts 11 characteristic features from
nuclear transients in the ZTF alert stream, including rise and decay timescales, blackbody temperature
evolution, and pre-transient variability metrics. Relying exclusively on photometric data without host
galaxy information ensures effectiveness for the faint transient population expected from the Rubin Observatory. The PRF, which treats feature measurements as distributions, was evaluated against XGBoost through Leave-One-Out Cross-Validation. It yields higher stability and robustness for ambiguous candidates than XGBoost. The two classifiers occupy complementary regimes. XGBoost achieves higher recall in balanced and high-precision scenarios, where its rigid decision boundaries efficiently isolate TDE-like sources, while PRF rejects more false positives by penalizing sources with large feature uncertainties. Applying this framework to archival data identified 11 new candidate TDEs from the unclassified population and 3 potential photometric TDEs within existing training labels previously misclassified as
supernovae or active
galactic nuclei. This work demonstrates that TDEs can be reliably identified using photometric lightcurve features, providing a host-independent framework. Uncertainty-aware, probabilistic classifiers are essential for the Rubin era to prevent the overconfident misclassifications inherent in deterministic models at low signal-to-noise.
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All authors Vysakh Anilkumar, Sjoert van Velzen, Marek Kowalski, Simeon Reusch
Solar and Stellar Astrophysics
PRICM3: A novel Polarization Ratio framework for three-dimensional CME reconstruction
Yara De Leo, Manuela Temmer, Fernando M. López et al. (+15 more)
Coronal mass ejections (CMEs) are inherently three-dimensional (3D), but traditional white-light coronagraphs provide only two-dimensional (2D) projections. While the Polarization Ratio Technique (PRT) utilizes Thomson scattering to infer proxy 3D
plasma locations, its results are typically limited to 2D topographical maps, hindering
geometric interpretation. To address this, we introduce PRICM3 (Polarization Ratio Integrated CME Mapper in 3D), a framework that converts PRT-derived maps into explicit 3D point-cloud reconstructions. This tool enables intuitive visualization, multi-viewpoint comparison, and direct validation against
geometric models such as the Graduated Cylindrical Shell (GCS). As a proof-of-concept, we analyzed a limb CME observed on 28 October 2021 using data from
Solar Orbiter/Metis, SOHO/LASCO, and STEREO-A/COR2. The independent reconstructions converged into a consistent 3D volume that aligned remarkably well with the corresponding GCS geometry. These results prove that the 3D information embedded in PRT topographical maps can be successfully recovered through spatial reconstruction. PRICM3 offers a powerful, intuitive method for interpreting polarimetric coronagraph observations, providing a vital tool for current and future
solar missions such as Proba-3/ASPIICS and PUNCH.
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All authors Yara De Leo, Manuela Temmer, Fernando M. López, Sarah E. Gibson, Hebe Cremades, Leonardo Di Lorenzo, Roberto Susino, Marco Romoli, Lucia Abbo, Aleksandr Burtovoi, Chiara Casini, Michele Fabi, Federica Frassati, Giovanna Jerse, Federico Landini, Maurizio Pancrazzi, Giuliana Russano, Clementina Sasso
Cosmology and Nongalactic Astrophysics
Beyond monomial $\alpha$-attractors
Laura Iacconi
Recent small-scale CMB data show a preference for larger scalar spectral index, $n_s$, when combined with DESI data. Monomial $\alpha$-attractor T-models can be reconciled with the new observations if the power of the
hyperbolic tangent function is $p\geq 6$, where $p$ is even. The supergravity construction of monomial T-models with $p>2$ relies on the assumption that lower powers remain negligible over the whole field range explored during inflation and reheating. What would be the consequences of going beyond the monomial formulation? As a first step in this direction, we consider the case of a binomial potential, given by the sum of quadratic and quartic terms. When the quartic coefficient, $c$, is $0< c+1/2 \ll 1$, we find that the new model displays non-universal behavior for $n_s$, leading to values as large as $0.965$ and with an $\alpha$-dependence that is qualitatively different from that of monomial potentials. By solving the background dynamics during the first few e-folds of perturbative reheating we show that the quartic term might dominate before the quadratic one eventually takes over as the inflaton oscillations decrease in amplitude. This leads to a time-dependent equation of state, with $\bar w\sim 1/3$ initially before ultimately $\bar w\to 0$. Obtaining a quartic-dominated reheating stage lasting $\sim4$ e-folds requires a substantial hierarchy between the quartic and quadratic terms, $c\sim 10^5$ for $\alpha\gtrsim 0.1$. Our study highlights that models beyond the monomial form can lead to non-trivial deviations of $n_s$ from the predictions of monomial potentials. Furthermore our results for $\bar w$ during reheating call into question the use of monomial models with large $p$; assuming that $\bar w$ is uniquely determined by the $p$-th power relies on substantial fine-tuning of the underlying supergravity potential.
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Astrophysics of Galaxies
X-ray Absorption Variability in NGC 1142: Another Constraint on the Nature of the Torus/Broad-Line Region in Active Galactic Nuclei
Isaiah S. Cox, Núria Torres-Albà, Stefano Marchesi et al. (+5 more)
The physics, geometry, and kinematics of the gas and
dust surrounding the central engine of active
galactic nuclei (AGN) are not well understood. In some sources, this material obscures the coronal X-ray emission, allowing its line-of-sight column density ($N_H$) to be measured. Many sources display $N_H$ variability across multiple epochs. Studying this variability can provide information about the distribution and dynamics of the obscuring material. Particularly, previous works have shown that the probability of observing $N_H$ variability increases with the number of observations available. Additionally, the observed magnitudes of the $N_H$ variability depend on the timescale between observations. In this work, we present the $N_H$ variability analysis of NGC 1142, which has a total of nine X-ray observations over $\sim20$ years, including five from a NuSTAR+XMM-Newton monitoring campaign performed in 2024-2025 and reported here for the first time. We use the physically-motivated
torus models UXCLUMPY, XSKIRTor, and RXTorusD to model the spectra. Our results confirm the previously observed trends, and we compare these trends to simulated obscuration curves assuming different locations and distributions of obscuring clouds.
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All authors Isaiah S. Cox, Núria Torres-Albà, Stefano Marchesi, Vittoria E. Gianolli, Xiurui Zhao, Marco Ajello, Indrani Pal, Andrealuna Pizzetti
Instrumentation and Methods for Astrophysics
DB-Bench: Benchmarking Deblenders for LSST DESC Using the Blending ToolKit
Aidan Berres, Grant Merz, Xin Liu et al. (+3 more)
Blending will be a major source of systematic uncertainty in downstream science analyses of LSST data. We
benchmark the performance of several deblenders, leveraging the Blending ToolKit (BTK) to perform rigorous, end-to-end testing. This
benchmark incorporates key deblending
algorithms, including SourceExtractor, SCARLET, and DeepDISC, with the goal of comparing their effectiveness in handling blended
galaxy images from LSST/Rubin simulations. A key focus is characterizing
algorithm performance in the regime of unrecognized blends, where multiple
galaxies are misidentified as a single object, as these cases introduce systematic biases that propagate into downstream cosmological analyses for
galaxy surveys. By utilizing BTK's ability to create customized, reproducible blends, we systematically test these deblenders against different blending conditions, such as source separation and brightness. The toolkit's standardized evaluation metrics, including detection precision,
segmentation accuracy, and source reconstruction, are comprehensive assessments of each
algorithm's strengths and limitations. Each deblender has performance caveats that may impact their true performance in real survey conditions. We find that SCARLET has high
segmentation and reconstruction performance, whereas DeepDISC has strong detection recall for faint and low-SNR sources, and SourceExtractor has accurate peak finding abilities but low
segmentation and reconstruction performance. This
benchmark provides valuable insights into the performance of existing deblenders and highlights areas for future development.
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All authors Aidan Berres, Grant Merz, Xin Liu, Éric Aubourg, Cécile Roucelle, the LSST Dark Energy Science Collaboration
Instrumentation and Methods for Astrophysics
Statistical treatment of searches for counterparts of positionally-uncertain astrophysical sources: from flux upper limits to detection
Julian Sitarek, Abelardo Moralejo, Juan Jiménez Quiles et al. (+3 more)
Rapid growth of the multimessenger and multiwavelength astrophysics had led to an increasing number of observations of the same events with instruments with different point spread functions. In particular pointing instruments with good angular resolution are used to pin-point the source of poorly-localized alert. In case no clear detection of the source counterpart is reached, the interpretation of the results requires statistical analysis. We investigate two approaches using the probability density function of the alert: frequentist and
Bayesian, as well as agnostic approach not using this information. We discuss the advantages and problems of all the methods, and compare their reliability and performance. We consider both a simple one-dimensional toy simulations and a realistic use case of full simulations of the follow-up of a gravitational wave event with gamma-ray
telescopes. The performance of both frequentist and
Bayesian approaches for weak signals is comparable and superior to the agnostic one.
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All authors Julian Sitarek, Abelardo Moralejo, Juan Jiménez Quiles, Giacomo D'Amico, Andrea Simongini, Antonio Stamerra
Solar and Stellar Astrophysics
Magnetic Reconnection Process in Partially Ionized Fluids: Insights from the Solar Chromosphere
Adrian R. Montañez-Lobo and Fabio D. Lora-Clavijo
Magnetic reconnection converts stored
magnetic energy into kinetic energy, heat, and radiation. While extensively studied in fully ionized
plasmas, observations show that ionization and recombination also play a role by modifying the local
plasma resistivity and enabling additional heating channels. This study examines
magnetic reconnection in the partially ionized
solar chromosphere, analyzing its morphology and energy releases with
attention to elastic collisions, ionization, and recombination. The MAGNUS code, originally built for ohmic resistivity and heat transfer, was modified to handle elastic and inelastic collisions. The simulations are 2.5D resistive MHD with two-fluid effects (charged + neutrals), adapted to handle interactions via these collision terms. A mixed explicit-implicit scheme was implemented to manage the stiffness of these terms. Simulations were carried out for three
magnetic field strengths: 100~G, 110~G, and 120~G. These values correspond to the low- to mid-chromosphere under quiet-Sun conditions. We found that reconnection heats the
plasma components by 18% to 110%. Although
plasma beta rises only slightly, the energy release grows far more, indicating that charged–neutral collisions, not just beta or available
magnetic energy, drive the enhanced reconnection. Furthermore, ionization and recombination become most significant in regions of peak temperature, particularly where particles are accelerated. Maximum reconnection rates from temporal analysis are 0.226, 0.253, and 0.279, respectively. Finally, in terms of energy, our results show that in a chromospheric volume of $0.4 \times 0.01 \times 0.4$~Mm$^{3}$, the energy released ranges from $10^{22}$ to $10^{23}$.
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Cosmology and Nongalactic Astrophysics
Inflation, Open Universes, and Dark Energy
Anton Chudaykin, Mikhail M. Ivanov, Renata Kallosh et al. (+3 more)
We study the impact of spatial
curvature ($\Omega_k$) and dynamical dark energy (parametrized by $w_0$ and $w_a$) on the spectral index $n_s$ using a combination of
cosmic microwave background
datasets (Planck, SPT, and ACT), and spectroscopic
galaxy samples from DESI, including both BAO and full-shape clustering measurements. We show that a small negative
curvature, $\Omega_k\simeq 3\times 10^{-3}$, lowers the value of $n_s$, bringing it closer to predictions of the Starobinsky,
Higgs, and simplest $\alpha$-attractor inflationary models. In particular, we find $n_s= 0.9667\pm0.0041$ (using Planck and DESI data) or $n_s= 0.9692\pm0.0035$ (adding ACT and SPT). Allowing for time-evolving dark energy also reduces the spectral index, leading to $n_s=0.9716\pm0.0032$ (from the combined
dataset), or $n_s=0.9694\pm0.0035$ in combination with a small negative
curvature. Our results demonstrate that the tension between current observational data and the Starobinsky,
Higgs, and simplest $\alpha$-attractor models holds only for $\Lambda$CDM, and can be mitigated in extended cosmological models. We discuss implications of these findings for inflationary models in an open universe and/or with dynamical dark energy, including scenarios with
quantum tunneling and non-standard
topology. Furthermore, we briefly describe a special class of $\alpha$-attractor models, where one can make $n_s$ arbitrarily large, and we describe the $\alpha$-attractor quintessence model. Such models may be of particular relevance when future data from DESI, as well as DESI-II, SPHEREx, Euclid, Rubin, and Roman, becomes available.
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All authors Anton Chudaykin, Mikhail M. Ivanov, Renata Kallosh, Andrei Linde, Oliver H. E. Philcox, Yusuke Yamada
High Energy Astrophysical Phenomena
Binary neutron stars in the next-generation era: Multi-messenger detection prospects and constraints on the equation of state, mass distribution, and cosmology
Hauke Koehn, Thibeau Wouters, Gilad Sadeh et al. (+5 more)
Next-generation gravitational-wave (GW) observatories will provide crucial insights into the nature of
neutron star (NS) matter and the cosmological expansion history. We estimate the number of multi-messenger detections from binary
neutron stars (BNS) with the Einstein
Telescope (ET) and
Cosmic Explorer (CE), and project the resulting constraints on the equation of state (EOS), BNS mass distribution, and cosmology via joint hierarchical
Bayesian inference. Assuming a local merger rate of 106.6 Gpc$^{-3}$ yr$^{-1}$ and considering two different mass functions, a narrow one centred around 1.4 $M_\odot$ and a wide one ranging between 1.1–2 $M_\odot$, we find that for ET, our mock follow-up
algorithm results in at least $\sim40$ and up to $\sim100$ successfully identified electromagnetic counterparts per year, depending on the detector layout and mass distribution. In a joint network with CE, the number of multi-messenger detections can range from $\sim 200$ to $\sim500$. Additionally, several more afterglows from gamma-ray bursts or KNe could be found with dedicated late-time observations. Based on the identified multi-messenger events, we perform an injection campaign to hierarchically constrain the EOS, mass distribution, and cosmology in a fully
Bayesian framework. Focussing on ET alone, we show how in an ideal scenario, GW signals, KNe, and host
galaxy redshifts can constrain the canonical NS radius $R_{1.4}$ within $\sim 0.2$ km and the Hubble constant $H_0$ within $\sim 1$ km s$^{-1}$ Mpc$^{-1}$, while recovering the essential features of the mass distribution. By comparing inference results that rely solely on GW data and those that incorporate light curve information, we find that while KN light-curve posteriors have a negligible impact on the EOS constraints, they can benefit the inference of cosmological parameters.
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All authors Hauke Koehn, Thibeau Wouters, Gilad Sadeh, Peter T.H. Pang, Mattia Bulla, Chris Van Den Broeck, Michael W. Coughlin, Tim Dietrich
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
The BGV Theorem and the Null Convergence Condition
William H. Kinney
We examine the relationship between the Null Convergence Condition (NCC) and the Borde-Guth-Vilenkin (BGV)
Theorem. We first show that, for an expanding spacetime foliated orthogonally to a timelike geodesic congruence with vanishing shear and vorticity, the BGV
Theorem follows when the NCC holds and the spatial
curvature is non-positive, ${}^3\mathcal{R} \leq 0$. The situation becomes more complex in the presence of shear, or non-geodesic threading of the spacetime. In these cases, the local expansion that enters the BGV construction depends not only on the local scalar expansion, but acquires terms given by the contraction of the shear and acceleration with locally defined spatial unit vectors. In the general case, null convergence and non-positive
curvature are no longer sufficient to guarantee that the BGV
Theorem holds. We discuss the result in the context of eternal inflation in the presence of comoving
curvature perturbations and state a more general version of the BGV condition relevant to asymptotically past-de Sitter eternal inflation.
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High Energy Astrophysical Phenomena
Estimating amplitude of matter density fluctuations in solar and supernova models using neutrino flavor evolution
Caroline Laber-Smith, Hansen Torres, Lily Newkirk et al. (+3 more)
Neutrinos can undergo substantial
flavor evolution between their production in astrophysical sources-such as the Sun and core-collapse
supernovae-and their subsequent detection in terrestrial detectors. This
flavor evolution is strongly influenced by the environment that the
neutrinos interact with, making them useful astrophysical messengers capable of potentially carrying information about the properties of the source wherein they are produced. In this work, we apply the framework of statistical data assimilation (SDA) in order to ascertain the extent to which a
neutrino signal at detection may contain information about matter density fluctuations along their path from the source. Using simplified models of
neutrino flavor evolution and propagation in the sun and in a core-collapse
supernova (CCSN), we find that the SDA method is able to extract information about the amplitude of density fluctuations in both the
solar and CCSN scenarios, with the method showing relatively greater reliability in the
solar neutrino case. Nonetheless, even in the CCSN
neutrino model, the method proved effective at high fluctuation amplitudes
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All authors Caroline Laber-Smith, Hansen Torres, Lily Newkirk, Dhriti Rathod, A. Baha Balantekin, Amol V. Patwardhan
Instrumentation and Methods for Astrophysics
Segment-level thermal sensitivity analysis for exo-Earth coronagraphy with segmented space telescopes
Ananya Sahoo, Laurent Pueyo, Iva Laginja et al. (+5 more)
Direct imaging and characterization of Earth-like
planets require ultra-stable wavefronts to achieve a starlight suppression level of 100 parts per trillion (ppt) in the coronagraphic dark region of the host
star. Thermal drifts in the
telescope may affect the wavefront stability. In this context, we present a segment-level thermal stability error budget for segmented space
telescopes crucial to Earth-like
planet detection and specify requirements for an ultra-stable
telescope. Our study utilizes multiple segmented primary mirror architectures, each with their respective apodizer solution developed by the Segmented Coronagraph Design & Analysis research team at the Space
Telescope Science Institute, tailored to an off-axis ~6 m-aperture space
telescope design. Using a detailed finite element model provided by L3Harris Technologies, we relate the temperature gradient at the location of the primary mirror to wavefront variations on each segment. We allocate both static and dynamic thermal tolerances for each segment using the Pair-based Analytical model for Segmented
Telescope Imaging from Space sensitivity approach, and a batch-estimation
algorithm respectively. Our analysis shows a non-uniform tolerance allocation across all segments of the primary mirror, as a result of apodization, and generally, with an increase in segment numbers, the tolerances for outer segments become less stringent. We observe trade-offs between segment size, tolerance relaxation and optimal wavefront sensing time to achieve a desired dark-hole contrast.
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All authors Ananya Sahoo, Laurent Pueyo, Iva Laginja, Bryony F. Nickson, Leonid Pogorelyuk, Laura E. Coyle, Rémi Soummer, Matthew East
Earth and Planetary Astrophysics
Kilometre-scale Jovian moon characterized for a potential JUICE flyby
Juan Luis Rizos, Jose Maria Gomez-Limon, Yucel Kilic et al. (+51 more)
Jupiter's irregular satellites are thought to be relics of early
Solar System planetesimals. However, their small sizes, large distances from Earth and close angular proximity to Jupiter make them difficult to characterize remotely. Here we report multi-instrument observations of kilometre-sized Kallichore, the only irregular moon of Jupiter amenable to a close flyby by ESA's Jupiter Icy Moons Explorer (JUICE), whose astrometric and physical properties were still poorly constrained. We used Hubble photometry and astrometry, followed by a ground-based, multi-site
stellar occultation campaign and astrometric and photometric observations with the 10.4-m Gran Telescopio Canarias. We reduced Kallichore's orbital uncertainty by up to approximately 80% and determined its shape: an elongated object with a minimum semi-axis ratio of a/b = 1.53 +/- 0.10, an area-equivalent diameter of 3.8 (+2.3/-0.3) km and a dark surface with a
geometric albedo of 3.7% (+0.7/-2.2). No close companions were detected. These new constraints provide a viable pathway towards a JUICE flyby once the spacecraft arrives in the Jupiter system in 2031.
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All authors Juan Luis Rizos, Jose Maria Gomez-Limon, Yucel Kilic, Altair R. Gomes-Junior, Jose Luis Ortiz, Nicolas Morales, Alvaro Alvarez-Candal, Pasquale Palumbo, Luisa M. Lara, Simon Porter, Benjamin Proudfoot, Evelyn Christiny M. Prais, Jean Marc Christille, Stefano Sartor, Antonio Cabrera, Stefan Geier, Alessia Spolon, Alice Lucchetti, Andrea Soffiantini, Anne Verbiscer, Armin Behrend, Elena Mazzotta Epifani, Jean-Louis Dumont, Luca Zampieri, Mike Skrutskie, Maurizio Pajola, Michel Boutet, Michele Fiori, Raoul Behrend, Stefano Sposetti, Vadim Nikitin, Fabien Cavaille, Jocelyn Serot, Laurent Miralabe, Marc Buie, Mehmed Naim Bagiran, Metin Altan, Mohammad Niaei, Noel Robichon, Orhan Erece, Pierre-Louis Phan, Raphael Lallemand, Suleyman Fisek, Valentin Etienne, Valery Lainey, Yavuz Guney, Yusuf Avcioglu, Francois Poulet, Paul Hartogh, Oliver Witasse, Pablo Santos-Sanz, Julia de Leon, Flavia L. Rommel, Fernando Tinaut-Ruano
Cosmology and Nongalactic Astrophysics
Multi-branch classification of diffuse cluster radio emission from the LOFAR two-metre sky survey
Markus Bredberg and Emma Tolley
Context.
Galaxy clusters sometimes host synchrotron radiation on scales of approximately 100 kpc to approximately 1 Mpc, with a surface brightness only a few times the image noise. This diffuse cluster
radio emission is a sensitive probe of
magnetic fields and intracluster medium dynamics, but disentangling the underlying physical processes requires statistically large samples spanning a wide range of cluster masses, dynamical states, and
redshifts, together with a sufficient sensitivity to low-surface-brightness emission. Aims. We explore two techniques for improving the detection of diffuse emission in
galaxy cluster images, relative to a baseline classifier: the scattering transform (ST) and squeeze-excitation (SE)
attention. Methods. We integrated an ST encoder into a dual-branch classifier (DualSSN) and a scattering network (ScatterNet). We incorporated SE
attention into the DualSSN and dual-branch convolutional neural network (DualCSN). These classifiers were then benchmarked against a simple convolutional neural network (CNN), across ten image pre-processing configurations and three cropping strategies. Performance was evaluated on small labelled
datasets from the second data release of the LOFAR Two-metre Sky Survey overlapping with the Second Planck catalogue of Sunyaev-Zel'dovich sources (LoTSS-DR2/PSZ2). Results. Alongside the multi-branch approach with SE and ST, cropping the image to a fixed number of
telescope beams and uv tapering (smoothing to a coarser angular resolution) improve classification performance, while tacking multiple pre-processed versions of an image does not. Conclusions. Scattering-transform-based multi-branch architectures with beam-normalised cropping are a promising direction for diffuse emission classification in the SKA era.
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Cosmology and Nongalactic Astrophysics
Growth, geometry, and early-universe split of the matter density parameter $\Omega_{\rm m}$
Felicitas Keil, Isaac Tutusaus and Alain Blanchard
While the $\Lambda$ cold dark matter ($\Lambda$CDM) model can successfully reproduce the measurements of many cosmological probes, some discrepancies have recently emerged. It is therefore necessary to test the standard cosmological model for consistency. An important stress test is to separate the effect of different cosmological regimes on the parameter inference. We treat three regimes separately here: geometry, growth, and the early Universe. The
geometric regime concerns the expansion and
curvature history, the growth regime governs structure formation, and the early-universe regime affects physics prior to recombination. Previous analyses have performed the split between geometry and growth, whereas we also consider the influence of the early Universe separately. We performed this split for the present-day matter density parameter $\Omega_{\rm m}$ using multiple cosmological observables. The data we used are
galaxy clustering and weak-
lensing statistics (3x2pt) from the Dark Energy Survey,
cosmic microwave background data from Planck,
baryon acoustic oscillations from the Dark Energy Spectroscopic Instrument, type Ia
supernovae samples from Pantheon+, and
redshift-space distortions from a collection of
galaxy surveys. For each of these probes, we introduced a phenomenological split into these three regimes. The correlation between the
geometric and the early regime for the matter density is strong, but that between the growth regime and the others is not. All regimes are compatible in the posterior distribution, but the difference between the geometry and the early regimes, $\Delta\Omega_{\rm m}^{\rm geo,early}$, has a 2$\sigma$ discrepancy with 0.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Systematic derivation of the Boltzmann equation for electroweak baryogenesis
Motoi Endo, Yushi Mura and Tenta Tsuji
We derive the Boltzmann equation for electroweak baryogenesis within a field-theoretical framework. We first algebraically solve the Kadanoff–Baym equations by incorporating the effects of gradients of the CP-violating bubble-wall background order by order. We then apply approximations and assumptions appropriate for electroweak baryogenesis and identify the on-shell parts of the solutions, which describe quasiparticle states propagating in a
plasma. Using these on-shell solutions, we derive the Boltzmann equations for
flavor-diagonal quasiparticle modes, while neglecting the off-diagonal components describing
quantum coherence between different
flavor modes. Our derivation generalizes previous field-theoretical treatments by retaining self-energy corrections, and our results are consistent with the known Boltzmann equations when these corrections are neglected. This framework provides a systematic and transparent derivation applicable to multi-
flavor bosonic and fermionic systems.
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Cosmology and Nongalactic Astrophysics
GGI Lectures on Large-Scale Structure Perturbation Theory (Effective Field Theory)
Mikhail M. Ivanov
These notes are an introduction to non-linear perturbation theory for cosmological large-scale structure. They are aimed at undergraduate and beginning graduate students and do not require any cosmology or
quantum field theory background. All necessary concepts are developed from scratch. The lectures are intended to explain all key ingredients needed to model the observed clustering of
galaxies in real and
redshift spaces. After a brief pedagogical introduction to the ideas of effective field theory (EFT), we develop large-scale structure EFT in the context of Newtonian cosmology using
symmetry principles. We discuss in detail the shortcomings of Standard Perturbation Theory, the non-linear
evolution of
baryon acoustic oscillations and its relation to the equivalence principle, counterterms and renormalization of the loop diagrams, and
stochastic effects. Then we develop EFT for
galaxy bias and
redshift space distortions. We also highlight some important facts about
redshift-space stochasticity, relevant for ongoing and future
galaxy surveys. Finally, we introduce Lagrangian Perturbation Theory.
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Astrophysics of Galaxies
JWST's Constraints on the Substellar IMF in NGC 2024
K.L. Luhman
A recent study has reported the detection of a turnover in the initial mass function (IMF) below 12 Mjup and the possible detection of a minimum mass near 3 Mjup in the heavily embedded cluster NGC 2024 (<1 Myr), which was based on a sample of brown
dwarf candidates in NIRCam images from the James Webb Space
Telescope (JWST). I have used those NIRCam data in conjunction with archival spectra from JWST's Near-Infrared Spectrograph (NIRSpec) to constrain the substellar IMF in NGC 2024. I present NIRSpec data for 87 sources, 67 of which are within the NIRCam field. Based on those spectra and data from previous studies (e.g., X-ray emission), I have classified 45 of the NIRSpec targets as members of NGC 2024, 17 of which have spectral types indicative of brown
dwarfs (M6.5-L; 13 are within NIRCam). The latter have mass estimates as low as 4 Mjup according to theoretical evolutionary models. There remain a few photometric candidates lacking spectra that extend down to the completeness limit of the images (>=2 Mjup for Ak>=1), so the minimum mass of the IMF has not been detected. It is not possible to measure a reliable substellar IMF from the NIRCam images because of the small number of brown
dwarfs encompassed by them, a bias against objects at lower masses due to the high extinctions, and incompleteness at >=10 Mjup due to the saturation limit. Thus, there is no evidence in the JWST data for a turnover below 12jup.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Ab Initio Real-Time Gravitational-Wave Parameter Estimation
David Yallup, Metha Prathaban, James Alvey et al. (+4 more)
We present a specialised GPU-native nested sampling kernel targeting rapid parameter estimation for gravitational wave inference problems. Building upon a Slice-within-Gibbs (SwiG) structure for rapid mixing, we investigate how far we can push baseline
stochastic sampling techniques on modern GPU hardware. We demonstrate that for typical long-duration binary
neutron star signals observed by the LIGO and Virgo detectors, we can achieve well calibrated posterior inference on the full uncompressed data of a three detector network in a median of twelve minutes on a single GPU. This falls to five minutes when sharded across four devices. Utilising heterodyning to compress the data reduces the median wall time across an injection campaign to 89 seconds – less than the length of the segment itself – and enables inference with precessing
spin,
tidal waveforms on GW170817 in around two minutes. This pushes
stochastic sampling techniques using full physical waveform calculations, launched from an uninformed prior state, towards real-time gravitational wave parameter estimation.
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All authors David Yallup, Metha Prathaban, James Alvey, Thomas C. K. Ng, Thibeau Wouters, Nikhil Sarin, Will Handley
Instrumentation and Methods for Astrophysics
Exploring generative design AI tools for astronomical instrumentation: a CubeSat chassis case study
Younes Chahid, Tassos Aretos, Will Cochrane et al. (+12 more)
Generative design artificial intelligence (AI) tools are currently used in multiple scientific fields, yet their adoption in mechanical engineering computer-aided design (CAD) remains limited due to a lack of disseminated case studies, limited availability of accessible tools, insufficient training in CAD data, the absence of universal editable file formats and more. Mechanical design for astronomical instrumentation faces increasing complexity in thermal, vibrational, and mechanical requirements alongside tight project deadlines. This paper presents a practical evaluation of an AI and FEA based generative design tool applied to chassis design for the Active Deployable Optical
Telescope (ADOT) CubeSat mission. Our analysis showcases the workflow steps including the setting of design, manufacturing and objective constraints. This study also shows the clear benefits of these types of tools, especially in the early brainstorming stages of multi-constrained mechanical structures, while also highlighting clear limitations like their black-box nature, the non-manufacturing-ready state of the results, and the time-consuming setup, limiting the tangible gain of these tools to high-value mechanical components.
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All authors Younes Chahid, Tassos Aretos, Will Cochrane, Katherine Morris, David Isherwood, Zeshan Ali, Graham Wilks, Noah Schwartz, Anmol Goyal, Marcell Westsik, Alastair Macleod, Steve Watson, Anjali Bhatt, David Lunney, Bradley Frank
Cosmology and Nongalactic Astrophysics
Domain walls through different cosmologies
I. Dankovsky, D. Gorbunov, S. Ramazanov et al. (+1 more)
We study properties of domain walls (DWs) arising in the model with a double well potential assuming different early universe cosmologies: from
dust through stiff matter domination to the limit of effective Minkowski space. Using
lattice simulations we demonstrate that
evolution of DW networks exhibits an approximate universality with respect to the cosmological equation of state (EoS). Namely, the wall area inside a given large volume is mainly determined by the particle horizon, while details of
cosmic expansion play a subdominant role. As it follows, particle horizon rather than the inverse Hubble rate is pivotal in DW
evolution defining the network correlation length and hence its phenomenology, e.g., the characteristic wavelength of emitted gravitational waves (GWs). Formation of closed DWs is shown to be very sensitive to the cosmological EoS and hence violate the universality, but their contribution to the total network is too small to change the overall picture. The universality breaking is also observed in the spectral properties of GWs from annihilating (biased) DWs: i) the IR slope of the spectrum depends on the EoS parameter; ii) there is a plateau in the UV part of the spectrum, which gets more pronounced as one stiffens the EoS. However, the dependence on the EoS is rather weak in the near peak region, which is most relevant from the viewpoint of
pulsar timing arrays and other searches for the
stochastic GW background. For a selection of
primordial cosmologies, we provide fitting formulae for the spectra near the peak.
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All authors I. Dankovsky, D. Gorbunov, S. Ramazanov, A. Vikman
Cosmology and Nongalactic Astrophysics
Signatures of kinetic gravity braiding in cosmological probes of the gravitational field
Ahmad Nouri-Zonoz, Farbod Hassani, Julian Adamek et al. (+2 more)
We study the observational signatures of kinetic
gravity braiding (KGB) models in relativistic cosmological probes constructed along the past light cone. Using the relativistic $N$-body code KGB-
evolution, we generate light-cone outputs and compute several observables that directly probe the gravitational field, including weak gravitational
lensing convergence, Shapiro time delay, the integrated Sachs-Wolfe and Rees-Sciama (ISW-RS) effects, and gravitational
redshift. Full-sky maps and angular power spectra of these quantities are constructed and compared with $k$-essence models and predictions from linear perturbation theory. We find that the derivative coupling between the scalar field and the metric modifies both the amplitude and the time
evolution of the gravitational potentials, producing scale-dependent deviations ranging from a few percent to tens of percent. In particular, the ISW-RS signal exhibits the largest fractional response, as the slower decay of the Weyl potential suppresses the KGB signal in the ISW-dominated regime, whereas nonlinear
evolution reverses this trend at higher multipoles, producing differences of tens of percent relative to $k$-essence. Weak gravitational
lensing also provides a strong complementary probe and, for the model considered here, exhibits clear deviations from the $k$-essence prediction at small scales with enhancements up to $\sim 10$-$12\%$ at multipoles $\ell \sim 10^2$-$10^3$. Our results show that linear perturbation theory accurately describes the large-scale behaviour, while nonlinear effects become important at smaller scales, particularly for the ISW-RS signal and, more moderately, for the convergence, and must therefore be included for reliable theoretical predictions.
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All authors Ahmad Nouri-Zonoz, Farbod Hassani, Julian Adamek, Emilio Bellini, Martin Kunz
Earth and Planetary Astrophysics · Cross-listed from physics.geo-ph
Calibrated uncertainty for wide-angle crustal models: how firmly is the Dharwar Craton Moho actually constrained?
Deepak Kumar, Laxmidhar Behera and Wojciech Czuba
Depth uncertainties for wide-angle crustal models are usually obtained by propagating an assumed picking error, yet picks from one shot gather are mutually dependent and velocity-depth trade-offs act at the level of the model class. We revisit the 210-km Perur-Chikmagalur profile across the Dharwar Craton using a permanently identified ledger of 2,000 primary P1-P2 first arrivals and 9,919 reflections from seven shots, with 852 later-turning P4 observations held aside for a conditional test. At fixed production velocity, a reciprocity-based fast-marching table makes it affordable to refit all six reflectors inside nested complete-shot validation and a receiver-coordinate block bootstrap. Withheld reflections are predicted to 68 ms RMS with standardized mean-squared residual 2.07 and 85 per cent coverage inside nominal 95 per cent limits; calibration is strongly phase-dependent, the Moho reflection specifically giving 73 ms and 2.12. First arrivals degrade from a 17 ms all-data RMS to 103 ms on untouched shots, driven by aperture extrapolation and a parameterization blind to the weathered near-surface. Exact window means place the Moho at 46.9 km beneath the western block and 39.4 km beneath the central block, a raw contrast of 7.47 km. Resampling receivers within shots gives a +/-0.10 km conditional spread; deleting whole shots gives +/-0.40 km, and two independent experiments agree the raw contrast is biased low by 0.36-0.48 km. Admissible velocity models span 6.46-8.64 km. Paired LVL-boundary reflections at 1,260 receivers separate beyond uncertainty everywhere, though the internal velocity shape stays unresolved. Sampling uncertainty and model-class uncertainty must be reported apart.
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High Energy Astrophysical Phenomena
Multiwavelength study of supernova remnants in the Circinus constellation with SRG/eROSITA
A. Khokhriakova and W. Becker
Supernova remnants (SNRs) are key tracers of
stellar feedback and the chemical and dynamical
evolution of the interstellar medium. However, identifying SNRs in complex regions remains challenging, particularly when only archival multi-wavelength data are available. We aim to search for previously unrecognized SNR candidates in the Circinus constellation by combining optical imaging,
radio continuum data, and available SRG/eROSITA all-sky survey X-ray observations, to provide a prioritized list of targets for future confirmation. Candidate remnants were classified according to the strength of the combined diagnostics. This joint analysis yields improved constraints on the morphology and spectral properties of known remnants in the region, including MSH 15-52 and G320.6- 1.6. In addition, we identify a new promising SNR candidate, G320.2-3.6. Our study provides a first multi-wavelength search of SNR candidates in the Circinus region. In addition to G320.2-3.6, three objects (G319.8-2.0, G321.8-1.1, and G320.5-1.8) emerge as promising targets for follow-up
radio, spectroscopic optical, and deeper, spatially resolved X-ray observations to confirm their nature.
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Astrophysics of Galaxies
Searching in HI for Massive Low Surface Brightness Galaxies: II. Completing the UGC Sample
Karen O'Neil, Wim van Driel and Stephan Schneider
Although Low Surface Brightness (LSB)
galaxies are increasingly well studied, considerable uncertainty still exists as to both their range in properties and their evolutionary history. LSB
galaxies provide a fascinating extreme in
galaxy formation and
evolution, allowing excellent tests of
galaxy formation and
evolution theories. Previously, our group successfully measured the HI gas and dynamical mass properties of 350 LSB
galaxies, significantly increasing the number of known extreme LSB
galaxies (massive, gas rich, etc.) in the process. Here we oresent 100-m Robert C. Byrd Green Bank
Telescope 21-cm HI line observations of a further 35 LBG
galaxies, only two of which have previously published data. Of the 35, 19 were detected. This paper also includes the HI information for five additional
galaxies detected accidentally (in the blank sky region or at alternative velocities), none of which has previously published HI results.
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Astrophysics of Galaxies
Bipolar HII regions Produced by Cloud-Cloud Collisions
Theotokis Georgatos, Anthony P. Whitworth, Richard Wünsch et al. (+1 more)
We use numerical experiments to explore two possibilities: (i) that Bipolar H II Regions are the result of Cloud-Cloud Collisions (CCCs), and (ii) that – when allowance is made for the chaotic nature of such collisions, the short duration of the bipolar phase, and different viewing angles – a large proportion of all H II Regions might be the aftermath of CCCs. To reduce the parameter space, our experiments only consider head-on collisions between two $500$ M$_\odot$ clouds, with three different levels of
turbulence, and two different collision velocities; the collision velocities define the `collision axis'. In all experiments, OB
stars only condense out after a Shock-Compressed Layer has formed (perpendicular to the collision axis), and fragmented to produce a Hub Filament System, with the OB
stars forming in the Hub. Ionising radiation from the OB
stars excites an H II Region, which tends to expand more rapidly in directions close to the collision axis, and more slowly in directions orthogonal to the collision axis, where it encounters the dense gas of the Shock-Compressed Layer. Consequently, the H II Region may appear bipolar, for a short period during its
evolution, if observed at sufficiently large angle to the collision axis. Viewed from smaller angles, the waist appears as a Bright-Rim, similar to conventional approximately spherical H II Regions. Under this circumstance, there are other metrics – based on the extent of diffuse freefree emission, the velocity dispersion of
Radio Recombination Lines,
dust emission at mid-infrared wavelengths – that might indicate the aftermath of a CCC, and establish CCCs as a dominant trigger for high-mass
star formation.
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All authors Theotokis Georgatos, Anthony P. Whitworth, Richard Wünsch, Annie Zavagno