Instrumentation and Methods for Astrophysics
Design and development of the PRIMAger instrument for PRIMA
Anne Costille, Fabrice Madec, Johan Floriot et al. (+11 more)
PRIMA (PRobe far-Infrared Mission for Astrophysics) is an infrared space observatory designed to operate over the next decade. Equipped with a 1.8 m
telescope actively cooled to 4.5 K, the project is currently in the concept study phase as part of the NASA Probe Explorers program. PRIMA will carry two instruments: FIRESS and PRIMAger. PRIMAger will offer two observation modes: hyperspectral imaging and polarimetric imaging. Both channels will use ultra-sensitive kinetic inductance detector (KID) arrays, covering wavelengths from mid-infrared to far-infrared. A European consortium will develop the cold unit of the PRIMAger instrument while the Readout Electronics and Continuous Adiabatic Demagnetization Refrigerator (CADR) will be provided by Goddard Space Flight Center (GSFC) and shared between the 2 instruments. The hyperspectral mode will cover the 24-84 $\mu$m range with a spectral resolution of R $\ge$ 8, ensured by a linear variable filter placed in front of the detector. The polarimetric mode will provide polarimetric imaging in four broad bands from 92 to 235 $\mu$m, using KIDs with three polarization orientations. The main structure of the instrument is the optomechanical assembly, cooled at 1K. It supports at first the two focal plane array assemblies incorporating 0.125K detector stages. In addition, the main structure is providing the interfaces for the 0.125K thermal link, the readout cables and the filters. This paper presents the technical requirements and expected performance of the instrument, as well as the associated design of the sub-systems ensuring compliance. A major challenge will be in-flight performance verification. We will also detail the development strategy, including the planned verification and test program.
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All authors Anne Costille, Fabrice Madec, Johan Floriot, Tony Pamplona, Thomas Prouvé, Laure Ciesla, Marc Sauvage, Willem Jellema, Lorenza Ferrari, Jochem Baselmans, Florent Canourgues, Renaud Goullioud, Carole Tucker, C. Darren Dowell
Astrophysics of Galaxies
Water Abundance and Ortho-Para Ratio in the S140 Photon Dominated Region
Dariusz C. Lis, Sofia Lawsky, Emeric Bron et al. (+2 more)
We analyzed archival far-infrared to submillimeter Herschel PACS, SPIRE, and HIFI spectroscopic observations of the S140
photon dominated region (PDR) to constrain the water vapor abundance and ortho-para ratio in this region. Toward the high-mass protostar IRS1, 52 spectral lines, including 15 water lines, are detected with the PACS and SPIRE instruments. PDR modeling suggests a UV radiation field G0 ~ 1 x 10^3 Habing units, and a thermal gas pressure of 5 x 10^8 K cm^-3 in this region. The models strongly underestimate intensities of high-J CO lines, which may indicate the presence of hot shocked gas associated with outflows along the line of sight, in addition to the UV irradiated gas. The spectral resolution of the PACS and SPIRE spectrometers is insufficient to separate the PDR and shock contributions. The PDR models further suggest that optically thick ground-state water lines trace primarily surface layers of the PDR. The gas temperature in this region is predicted to be ~ 800 K and the water abundance with respect to hydrogen
nuclei reaches ~ 10^-5. However, the bulk of gas-phase water is located in a more shielded region, deeper inside the PDR, with a gas temperature ~ 24 K, and a gas-phase H_2O abundance of ~ 10^-7. A comparison of the observed water line fluxes toward IRS1 with PDR model predictions shows no evidence for departures from the LTE ortho-para ratio at the local gas temperature, which is assumed in the models. The sensitivity of the Herschel instruments was insufficient to measure the water ortho-para ratio toward the externally illuminated edge-on PDR at the surface of the S140 molecular cloud. Such observations will be possible with the next generation far-infrared spectroscopic space missions currently in development.
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All authors Dariusz C. Lis, Sofia Lawsky, Emeric Bron, Franck Le Petit, Javier R. Goicoechea
Earth and Planetary Astrophysics · Cross-listed from eess.SY
Fast and Stable Nonlinear Emulation of TIEGCM Using an Autoregressive SINDy Framework
Daniele Sicoli, Sriram Narayanan and Piyush M. Mehta
The ever-growing number of satellites and resident space objects in low Earth orbit keeps increasing the risk of collision between these objects. To mitigate this risk, the development of new space situational awareness tools and a new generation of probabilistic emulators of the thermosphere is increasingly felt by the community of operators and scientists. We previously built a Reduced Order Probabilistic Emulator based on 3 steps: dimensionality reduction, dynamic modeling, and uncertainty quantification. Here we further develop the dynamic modeling side within ROPE using a class of stable and autoregressive nonlinear models inspired by SINDy, a framework for the identification of the nonlinear dynamics. We use this framework, which we call SINDy-AR, to emulate the thermospheric density simulated by TIEGCM. This is also the first time a SINDy-AR framework is applied to such a high dimensional system as the thermospheric emulation because of its complexity. The dynamical emulators are selected on stability and accuracy criteria, so that they can be relied on in operations and space situational awareness applications. Building surrogate models with SINDy-AR can show dynamical differences between the learned emulations. The state-dependent structure of the TIEGCM emulation shows compatibility with the presence of terdiurnal, 27-day linked to solar rotation, semiannual, and annual tidal waves. The execution speedup of the whole SINDy-AR pipeline with respect to TIEGCM 2.0 is about 90,000 times, which makes the new framework capable of being deployed on board a satellite given the low computational constraints it would be subjected to.
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Solar and Stellar Astrophysics
Magnetohydrodynamic coronal modelling with high-fidelity magnetograms
Haopeng Wang, Stefaan Poedts, Wensi Wang et al. (+16 more)
To resolve coronal structures in detail, it is essential to constrain the coronal model using high-fidelity magnetograms with minimal smoothing. In this paper, we improve the numerical stability of COCONUT to enable efficient coronal MHD simulations driven directly by photospheric magnetograms, including
magnetic field strengths exceeding 1000 Gauss (G), and then use it to investigate the impact of small-scale
magnetic field structures that are typically filtered out of photospheric magnetograms on the coronal simulation results. We constrain this model with two types of magnetograms: the high-fidelity HMI photospheric magnetogram with only minor preprocessing through Gaussian smoothing, which preserves
magnetic field strengths reaching 1500 G, and one processed using 50th-order filtered spherical harmonics, where the
magnetic field strength is limited to below 100 G. The results demonstrate that the COCONUT can reproduce the large-scale coronal structures revealed by pB and EUV observations. Compared with the coronal MHD simulation constrained by a conventionally filtered magnetogram, the simulation constrained by the high-fidelity magnetogram yields approximately $50\%$ more OMF and produces EUV images that are more consistent with the observations. Moreover, the results show that when viewed from low latitudes in certain EUV passbands, such as the 193~Å channel, open-field regions near the solar poles may appear as bright structures that are typically associated with closed-field regions. This finding highlights the need for solar polar-orbiting missions to overcome the limitations and ambiguities arising from the restricted view of the polar regions from the ecliptic plane and to provide more complete full-Sun observations.
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All authors Haopeng Wang, Stefaan Poedts, Wensi Wang, Rayan Dhib, Andrea Lani, Martina Condoluci, Tinatin Baratashvili, Quentin Noraz, Luis Linan, Hyun-Jin Jeong, Junyan Liu, Zhenguang Huang, Rui Liu, Lingyu Dong, Rui Zhuo, Liping Yang, Giovanni Alejandro Pinzón Estrada, Jasmina M. Magdalenić Zhukov, Brigitte Schmieder
Astrophysics of Galaxies · Cross-listed from gr-qc
Black Hole Horizon Fluctuations from Unruh Quantum Noise
Kashif Ammar Yasir
The mean Hawking flux does not determine how
quantum stress fluctuations perturb a black-hole geometry. That information resides in field correlations, including
vacuum contributions absent from the outgoing luminosity. Here we connect the complete exterior Unruh Wightman function to a finite-band
stochastic reconstruction of Schwarzschild geometry. We retain the incoming
vacuum and both outgoing frequency branches, form the connected stress covariance before angular projection, and propagate its monopole through a density-driven radial response. A shared Gaussian reconstruction then resolves how the value and derivative of the lapse control different
geometric observables. For the specified covariance and noise amplitude, 2,200 realizations give relative widths of 0.0185 for the local horizon radius and 0.0483 for the surface-
gravity temperature parameter, consistently across histograms and reconstruction checks. Covariance derivatives explain this unequal sensitivity. The construction separates the
quantum-state input from the gravitational closure and spatial sampling assumptions, providing a reproducible finite-resolution description of how Hawking-field correlations affect horizon positions and surface-
gravity statistics.
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Astrophysics of Galaxies
Broadband radio continuum and host galaxy properties of extremely inverted spectrum compact radio galaxies
Mukul Mhaskey, Barenya Dev, Aritra Basu et al. (+3 more)
We present broadband
radio continuum spectra spanning 0.15-8 GHz for a sample of ten Extremely Inverted Spectrum Extragalactic
Radio Sources (EISERS), selected from narrowband, low-frequency surveys below 1.4 GHz. In these surveys, EISERS show unusually steep low-frequency spectral indices, approaching or exceeding the synchrotron self-absorption (SSA) limit of $\alpha$= +2.5, expected for homogeneous synchrotron sources. We have performed follow-up quasi-simultaneous
radio observations of these sources using uGMRT (0.150-1.4 GHz) and VLA (1.0-8.0 GHz). The new observations provide improved frequency coverage and consistent flux calibration across both the optically thick and optically thin spectral regimes. We find that the spectral slopes of EISERS in optically thick regime are flatter than the two frequency spectral indices obtained using TGSS and WENSS and lie in the range +1.6 to +3, suggesting that heterogeneous survey data can introduce biases through flux-scale offsets, intrinsic variability of these compact sources and diverse angular resolutions between surveys. We modelled the broadband
radio spectra as synchrotron emission affected by synchrotron self-absorption and subsequently modified by free-free absorption in an external ionised medium. The estimated physical parameters based on the best-fits indicate that the
magnetic fields and thermal electron densities are similar to the general class of peak spectrum sources, with $B_{SSA}$ spanning over a large range of values from 20 mG to 8 G and $n_{e} \sim 29-128{cm}^{-3}$. Optical and infrared analysis further indicates that the EISERS are preferentially associated with dusty starburst
galaxies, composite starburst-AGN systems, or obscured AGN embedded in dense circumnuclear environments, supporting a scenario in which at least a fraction of these sources represent young or environmentally confined
radio AGN.
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All authors Mukul Mhaskey, Barenya Dev, Aritra Basu, Helmut Meusinger, Surajit Paul, Matthias Hoeft
Cosmology and Nongalactic Astrophysics
Gravitational-wave background from supermassive black holes without merger trees: Tidally regulated mergers and direct inference from the NANOGrav 15 yr data
Shin'ichiro Ando
We present a semi-analytic framework that computes the gravitational-wave background (GWB) from supermassive black hole (SMBH) binaries by direct integration of an $N$-body-recalibrated extended Press-Schechter
accretion kernel, bypassing Monte Carlo merger trees entirely. The calculation is resolution-free and fast enough to be sampled directly against
pulsar-timing data with no emulator or precomputed model bank. Between
halo accretion and black-hole binary formation, we couple the satellite's simulation-calibrated tidal mass loss continuously to Chandrasekhar dynamical friction. Satellites below a sharp, nearly
redshift-independent mass-ratio threshold, $\xi \simeq 0.04$, are stripped faster than they sink and stall: their drag collapses onto the stellar core, and 38% of accreted satellites are unmerged by $z=0$. Combining this population model with per-binary stellar-hardening turnovers and eccentric spectra, we sample the five-parameter posterior directly against the NANOGrav 15 yr Hellings-Downs-correlated free spectrum, excluding the $15.8$ nHz bin, whose excess power a subsequent chromatic-noise reanalysis attributes to
pulsar noise. The data prefer a black-hole mass normalization $+0.31^{+0.20}_{-0.23}$ dex above the locally calibrated black-hole-bulge mass relation, consistent with earlier indications that the nanohertz background is loud relative to local SMBH calibrations and robust to the delay model, merger kernel, local mass calibration, and its
redshift evolution. The spectrum is compatible with, but does not require, eccentric binaries or dense stellar environments.
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High Energy Astrophysical Phenomena
Energy-independent X-Ray Polarization in 4U 1630-47 in the Intermediate State from Spectroscopy and Polarimetry
Elena Seifina, Lev Titarchuk, Paolo Soffitta et al. (+4 more)
The IXPE mission enabled measurements of X-ray polarization in accreting binaries. The dependence of the X-ray polarization degree on the binary inclination and the optical depth of the emitting medium $\tau_0$ are the new important tools in X-ray Astronomy. We analyzed the black hole X-ray binary 4U~1630–47 as an example of one of the enigmatic sources in our
Galaxy. We consider spectral and polarimetric observations of outburst episodes from 4U~1630–47 observed with the IXPE and the NICER. We carefully investigated a time interval of the IXPE observations during which 4U~1630–47 was in a single spectral state (the intermediate state) and found that the polarization degree did not change significantly during this time interval with the
photon energy in the 2–8 keV range ($P\sim$ 6%). We interpreted this energy independence behavior in $P(E)$ as a result of the Comptonization (up-scattering) of soft
photons in the flat Compton cloud. We argued that the X-ray source broadband energy spectra can be reproduced by a physical model composed of the Comptonized component and iron-line (Gaussian) component. Spectral analysis using this model shows that during the intermediate state the 4U~1630–47 spectrum was characterized by a
photon index $\Gamma\sim 2.5$ and the electron temperature $kT_e\sim ~9 ~{\rm keV}$. In fact, this approach allows one to easily find the half-optical depth $\tau_0\sim 1.8$ of the Compton cloud in 4U~1630–47 applying the inclination $69\pm1^\circ$ and using the relation $(P,\cos(i),\tau_0)$ when solving the full radiative transfer equation for a flat Compton cloud by an iterative method. This approach is also accompanied by the fact that the polarization degree is independent of the
photon energy, which we demonstrate observationally, at least for 4U~1630–47 in the 2–8 keV range.
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All authors Elena Seifina, Lev Titarchuk, Paolo Soffitta, Lorenzo Marra, Fiamma Capitanio, Fabio Muleri, Anastasiia Emelianova
Cosmology and Nongalactic Astrophysics
JESSNet: Joint dEconvolution and Sparse Separation Network for HI 21 cm foreground cleaning
Athanasia Gkogkou, Victor Bonjean, Jean-Luc Starck et al. (+3 more)
Foreground cleaning is a major challenge for H\,i 21 cm intensity mapping, particularly in the presence of a chromatic instrumental beam that couples angular foreground structure into the frequency direction and under incomplete sky coverage. We introduce JESSNet, a beam-aware, mask-compatible foreground-cleaning framework for single-dish intensity mapping. Building on SDecGMCA, JESSNet introduces three main extensions: a multiscale angular decomposition with scale-dependent mixing
matrices and channel selection, a learned spherical-wavelet ”learnlet” sparse regularization operator, and a mask-constrained reconstruction applicable to Galactic masks and survey footprints. We test JESSNet on simulated SKA-MID-like observations over $900\text{-}1300\,{\rm MHz}$ ($z\simeq0.09\text{-}0.58$), including H\,i emission, Galactic and extragalactic foregrounds, thermal noise, and an oscillating MeerKAT-inspired chromatic beam. The multiscale reconstruction accurately recovers the angular and frequency power spectra of the input H\,i signal, improves the recovery at low and intermediate angular scales relative to a single-scale implementation, and reduces residual beam-induced spectral features. JESSNet also remains effective for a synthetic survey footprint, preserving the H\,i power spectra under incomplete sky coverage. The code and analysis pipeline are publicly released to facilitate reproducibility and future applications to simulated and observational data.
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All authors Athanasia Gkogkou, Victor Bonjean, Jean-Luc Starck, Pauline Gorbatchev, Marta Spinelli, Panagiotis Tsakalides
Instrumentation and Methods for Astrophysics
Technological maturation of a Gigapixels Astrometry instrument for the Habitable World Observatory.
Florence Ardellier-Desages, Jerôme Amiaux, Jérôme Bobin et al. (+12 more)
This paper presents the development strategy for HWO-AGATE (Accurate Guiding and Astrometry Targeting Exoearths), a high-precision relative astrometry instrument concept designed for the future Habitable Worlds Observatory (HWO). The instrument is based on a gigapixel-class focal plane that incorporates the new generation of large-format GigaPyx CMOS sensors developed by Pyxalis. The proposed architecture relies on four 220-megapixel sensors assembled into a focal plane array and coupled with a dedicated calibration system to achieve the astrometric precision required for
exoplanet detection and characterization. Preliminary study identified three major technological challenges. First, the performance of the 220-MP detectors must be validated against HWO's astrometric requirements. Second, the development of space-qualified packaging and integration solutions is required for a multi-sensor focal plane, while addressing the electrical and thermal constraints associated with the fast readout of large-format CMOS detectors. Third, an onboard calibration data-processing architecture must be implemented to reduce the raw data volume by approximately two orders of magnitude, enabling efficient operation within spacecraft resource limits. To address these challenges, we propose a comprehensive technology maturation program based on the construction of a representative end-to-end detection chain. The demonstration setup will include a partial focal plane equipped with 220-MP sensors, front-end electronics, a dedicated processing unit, and the calibration subsystem. The objective is to demonstrate compliance with HWO-AGATE requirements and to raise the maturity of large-format CMOS detector technology to Technology Readiness Level 5 (TRL 5). Detector validation and space-qualified packaging activities are already supported through institutional funding and the French national PEPR ORIGINS program in the RETINA (Researching
Exoplanets Through Imaging for Narrow-angle Astrometry) project.
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All authors Florence Ardellier-Desages, Jerôme Amiaux, Jérôme Bobin, Stéphane Chevobbe, Eric Doumayrou, Pierre-Antoine Frugier, Pierre-Olivier Lagage, Manon Lizzana, Fabien Malbet, Jerôme Martignac, Julien Michelot, Fabrice Pancher, Pichon Thibault, Samuel Ronayette, Hugo Rousset
Instrumentation and Methods for Astrophysics
Not just a phase: detecting nanohertz gravitational waves from phase alone
Kathrin Grunthal, Eric Thrane, Rutger van Haasteren et al. (+2 more)
Unambiguously detecting a gravitational-wave background (GWB) in
pulsar-timing data requires a robust detection statistic. The
pulsar timing community currently relies heavily on the cross-correlation-based "optimal statistic." Its design was motivated to avoid false-positive detections from unmodeled
pulsar red noise. However, recent work by van Haasteren (2025) suggests that the optimal statistic is not, in fact, optimal. Moreover, the optimal statistic is still susceptible to false positives from misspecified noise. To guard against this, analysts employ quasi-resampling methods such as phase shifts, in which complex phases are randomly assigned to each
pulsar strain measurement, thereby destroying any gravitational-wave-induced correlations. Inspired by the concept of phase shifts, we introduce a formalism in which the GWB is measured entirely from phase measurements. We argue that this approach is robust against false positive detections without the need for ad hoc quasi-resampling methods. We demonstrate the feasibility of this formalism by measuring the amplitude and spectral index of a simulated GWB, injected to a simplified mock representation of a
pulsar timing array data set. For this example, we use simulation-based-inference and model the phase-based likelihood using a neural circular spline flow. We show that it is possible to adequately recover the spectral parameters of the gravitational wave background signal using the phase-based likelihood. By comparing our results to ones obtained with the optimal statistic, we show how much resolving power comes from amplitude versus phase.
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All authors Kathrin Grunthal, Eric Thrane, Rutger van Haasteren, David J. Champion, Michael Kramer
Astrophysics of Galaxies
Linking simulations and observations of star-forming regions I. Masses and temperatures of ALMAGAL-like cores
Birka Zimmermann, Álvaro Sánchez-Monge, Stefanie Walch et al. (+1 more)
Dense cores and clumps in massive
star-forming regions are studied through (sub-)millimetre continuum observations, but inferred masses and temperatures can be biased by limited resolution, interferometric filtering, projection, and uncertain dust temperatures. We quantify how reliably core masses and temperatures can be inferred from ALMA-like continuum data using synthetic observations of such clumps. We post-processed radiation-hydrodynamic simulations of collapsing 1000 M$_\odot$ clumps with RADMC-3D and CASA to generate synthetic ALMAGAL-like images. Cores were defined around sink particles, enabling comparison of masses from the 3D simulations, idealised RADMC-3D maps, and synthetic ALMA images. We quantified how resolution, projection, and viewing angle affect core masses, and tested three dust-temperature
estimators (clump-scale L/M, a L/M+flux model, and a supervised machine-learning estimate). Projection effects cause line-of-sight integrated core masses within 1500 au to exceed spherical masses by factors of two to three. The empirical L/M temperature prescription follows the global thermal
evolution but misses the core-to-core scatter, producing core-mass errors of a factor of a few. Including local flux improves temperature and mass estimates, while a gradient-boosting machine-learning model suggests further improvement. Synthetic ALMAGAL-like images recover the global core structure, but flux-reconstruction uncertainties introduce mass errors up to a factor of three and limit reliable core-mass recovery to $\gtrsim 0.3$ M$_\odot$, comparable to the ALMAGAL completeness limit. Individual core masses are typically uncertain by a factor of three to five, mainly due to dust-temperature assumptions and flux reconstruction. Reducing these biases requires temperature estimates that include local core information rather than a single clump-scale L/M-based prescription.
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All authors Birka Zimmermann, Álvaro Sánchez-Monge, Stefanie Walch, Gary A. Fuller
Earth and Planetary Astrophysics
Spins and shapes of asteroids reconstructed from photometry from surveys
Josef Ďurech and Josef Hanuš
Modern asteroid surveys routinely acquire sparse photometric measurements for hundreds of thousands of asteroids. These data can be exploited to reconstruct asteroid
spin states and shapes, providing statistical constraints on the rotational
evolution of different dynamical populations.Our goal is to derive
spin-state and shape models from publicly available survey photometry and use the enlarged sample to investigate the distributions of asteroid physical properties across the Solar System. We combined sparse photometry from Catalina, Mt. Lemmon, Pan-STARRS, ZTF, USNO, ATLAS, ASAS-SN, TESS, and Gaia and applied convex light-curve inversion to determine sidereal rotation periods,
spin-axis orientations, convex shapes, phase-function parameters, and colors. The extensive parameter-space search was performed using the distributed-computing project Asteroids@home.We derived approximately 30000 asteroid models, including about 22000 unique
spin-state solutions and almost 10000 partial pole solutions, tripling the number of available asteroid models. The enlarged sample confirms the dependence of the rotation-period distribution on taxonomic class, reveals a pronounced lack of elongated asteroids near the
spin barrier, and shows that slow rotators exhibit systematically larger photometric residuals, supporting the interpretation that many are in non-principal-axis rotation. We derived
spin-state distributions for 47 near-Earth asteroids, 247 Jupiter Trojans, and 157 Hildas. The expanded Trojan sample no longer shows a statistically significant excess of prograde rotators. The combination of modern survey photometry and large-scale light-curve inversion enables population studies based on tens of thousands of asteroid models. The resulting database provides improved constraints on the rotational
evolution of asteroids
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Earth and Planetary Astrophysics
Giant impacts preferentially remove low-mass atmospheres: a generalised scaling law for impact-driven atmospheric loss
Matthew J. Roche, Simon J. Lock, Philip J. Carter et al. (+1 more)
Impact-driven atmospheric loss plays a key role in shaping the diversity of planetary atmospheres. However, existing prescriptions for calculating loss from a given impact neglect the critical role of atmospheric mass on loss, and thus often severely miscalculate the extent of loss. Using 3D smoothed particle hydrodynamics simulations, we quantify atmospheric loss during giant impacts onto
planets with 1-20% mass fraction atmospheres and show that less massive (lower-pressure) atmospheres are significantly easier to remove. We derive a new scaling law for atmospheric loss that includes the effects of atmospheric mass and is applicable to collisions between volatile-poor planetary embryos through to super-Earths and sub-Neptunes. Applying our scaling law to $N$-body simulations of solar system formation, we show that including the coupling between atmospheric mass and loss efficiency results in significantly more atmosphere removal. Substantial atmospheric loss events are common for smaller
planets ($\lesssim$0.6 M$_{\oplus}$), whilst even roughly Earth mass bodies lose 30-100% of their atmospheres through multiple impacts. We also show that atmospheric loss during the Moon-forming impact strongly depends on both the pre-impact atmospheric mass and impact style. For a representative $\sim$100 bar pre-impact atmosphere, Earth could have lost between 20-80% of its atmosphere. In any system that undergoes a phase of giant impacts, the atmospheres of its host
planets will be unavoidably shaped by the stochasticity of impacts. Our new scaling law can be readily incorporated into models of
planet formation and system-wide
evolution, offering new insights into the origins of planetary diversity.
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All authors Matthew J. Roche, Simon J. Lock, Philip J. Carter, Zoë M. Leinhardt
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Investigating Optical Coupling Material Candidates in NaI(Tl) Detectors for the SABRE-North Dark Matter Experiment
Chemseddine Ananna, Gabriella Cataldi, Davide D'Angelo et al. (+21 more)
Direct dark matter detection with NaI(Tl) scintillators requires ultra-low-background materials. Silicone optical pads can couple NaI(Tl)
crystals to photomultiplier tubes (PMTs) if they provide adequate optical transmission and radiopurity. We characterize four candidate materials for the SABRE-North experiment: commercial EJ-560, used as a reference, and three materials produced at the University of Salento (SYLGARD 184, EGel 3002 A/B, and a hybrid formulation) using different catalyst ratios and curing conditions, yielding ten samples in total. Optical transmittance was measured from 310 to 850 nm by UV/Vis/NIR spectrophotometry. Radiopurity was assessed at the STELLA facility at LNGS using high-purity germanium (HPGe) $\gamma$-ray spectrometry and, for EJ-560, high-resolution ICP-MS. At the 410 nm NaI(Tl) emission peak, EJ-560 shows an absorbance coefficient of $0.064\pm0.017$ mm$^{-1}$. The best locally produced samples reach $0.097\pm0.015$ and $0.093\pm0.014$ mm$^{-1}$ for SYLGARD 184 with a 10:2 base-to-catalyst ratio cured at room temperature and at $40^\circ$C, respectively, $0.125\pm0.015$ mm$^{-1}$ for EGel 3002 with a 2B:A ratio cured at $40^\circ$C, and $0.106\pm0.014$ mm$^{-1}$ for the hybrid 10:1 EGel A:CataSYL formulation cured at room temperature. EJ-560 exhibits detectable $^{232}$Th-chain activity at about 1.8 mBq/kg and the highest $^{40}$K activity, $(120\pm20)$ mBq/kg. The locally produced materials show no detectable Th-chain contamination but exhibit $^{226}$Ra activities of about 2.3 mBq/kg and lower $^{40}$K levels. No single material is optimal across all criteria. Additional ICP-MS screening, HPGe measurements of cured pads, and direct NaI(Tl)-PMT light-yield tests are required for a conclusive SABRE-North material selection.
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All authors Chemseddine Ananna, Gabriella Cataldi, Davide D'Angelo, Giulia D'Imperio, Maria Luisa De Giorgi, Giuseppe Di Carlo, Attilio Di Giacinto, Marcella Diemoz, Aldo Ianni, Sana Gul Khattak, Edoardo Martinenghi, Alessandro Miccoli, Marcin Misiaszek, Daniele Montanino, Valerio Pettinacci, Lidio Pietrofaccia, Shahram Rahatlou, Krzysztof Szczepaniec, Claudia Tomei, Valerio Toso, Chiara Vignoli, Samina Zuhra, Francesco Ferella, Stefano Nisi
Cosmology and Nongalactic Astrophysics
Limited Impact of CMB B-mode Polarization on Constraints on Cosmic Topology
Ryota Himeno, Atsushi J. Nishizawa and Kiyotomo Ichiki
The global spatial structure of the universe is a fundamental question in cosmology. Although the standard model usually assumes a trivial
topology, a multiply connected universe can break statistical isotropy and generate off-diagonal covariance between the spherical-harmonic coefficients of
cosmic microwave background fluctuations. In this work, we investigate whether CMB B-mode polarization improves constraints on the cubic three-
torus, or $E_1$
topology. We construct the full harmonic-space covariance
matrices of the temperature, E-mode, and primordial B-mode anisotropies, including correlations between different $(\ell,m)$ modes, and evaluate Gaussian likelihoods using random realizations generated from a statistically isotropic $\Lambda$CDM model with trivial
topology. To isolate the intrinsic topological information carried by each CMB observable, we consider the ideal
cosmic-variance-limited case, neglecting instrumental noise and gravitational
lensing. We find that adding primordial B-mode polarization yields only a marginal improvement in the ability to distinguish the $E_1$
topology from the trivial
topology, even under these ideal conditions. The different constraining powers of the temperature, E-mode, and B-mode anisotropies can be understood through the combined effects of their transfer-function responses and the
topology-induced off-diagonal correlations in harmonic space. }
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Solar and Stellar Astrophysics
Coherent radio bursts, polarity reversal, and quiescent emission from the M4V dwarf WW PsA
Jackson Mitchell-Bolton, Laura Driessen, Tara Murphy et al. (+6 more)
Coherent
radio emission from magnetically active M dwarfs is largely observed in two varieties:
stochastic solar-like bursts and beamed, rotationally modulated emission including auroral pulses. Detailed monitoring of these
stars is critical for probing the
plasmas and
magnetic fields driving the emission. We conducted a search for polarised
radio emission from
stars within 85 pc, covering $2.2\times10^4$ h of stellar dynamic spectra from the ASKAP Deep Investigation of Neutral Gas Origins (DINGO) survey. We report the discovery of coherent
radio bursts from the M4V dwarf WW PsA. In addition to quiescent emission, we detect three long-duration ($\gtrsim$30 min) bursts, each ~100% circularly polarised, in 283.3 h of data. We also report a fourth burst in an epoch not covered by our search, detected using the VASTER pipeline. One of the bursts features a polarity reversal midway through, based on which we favour the electron cyclotron maser (ECM) mechanism over
plasma emission. We tentatively propose the bursts are due to rotationally modulated ECM pulses of variable intensity. We infer the required physical properties of WW PsA, including a high obliquity $\beta = 74^{+6}_{-22}$ deg under an oblique rotator model.
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All authors Jackson Mitchell-Bolton, Laura Driessen, Tara Murphy, Joshua Pritchard, Barnali Das, Richard Dodson, Martin Meyer, Jonghwan Rhee, Yuanming Wang
Earth and Planetary Astrophysics
SPIRou near-infrared spectropolarimetry of the ultra-hot Jupiter KELT-9b: tentative detection of the planet magnetic field
Alexis Lavail, Florian Debras, David Rogé Royo et al. (+23 more)
Exoplanetary
magnetic fields govern atmospheric escape and circulation but have eluded detection in close-in
planets. In the ultra-hot Jupiter KELT-9b, atmospheric dynamo is predicted to generate atmospheric fields of 400–4000 G. We search for the circular polarization in atomic lines that a
magnetic field would imprint, through the Zeeman effect, on the transmission spectrum of KELT-9b. We observed three transits with SPIRou at the CFHT, on 07 September 2025 and 03 and 06 July 2026, and applied least squares deconvolution to 1398 atomic lines to map the transit-averaged Stokes $V$ and null spectra against orbital semi-amplitude $K_{\rm p}$ and systemic velocity $v_{\rm sys}$. The 2025 transit shows a Stokes $V$ signature of $V/I_c = 9.3 \times 10^{-5}$ at $K_{\rm p} = 219 \pm 11$ km s$^{-1}$, $v = -34.0 \pm 1.2$ km s$^{-1}$, close to the expected planetary velocity. Its false-alarm probability is $1.9 \times 10^{-4}$, formally a marginal detection. Both 2026 transits are of comparable sensitivity but neither exhibits a signal at that location, setting $3\sigma$ limits of $4.9$ and $6.0 \times 10^{-5}$; the 2025 amplitude would have been recovered at $4.9\sigma$ and $4.0\sigma$. The 2025 signature is robust to the tests we applied to it, but qualifies as a marginal detection at best. Spurious signals of comparable strengths occur elsewhere in our Stokes $V$ and null maps, and we cannot exclude that our marginal detection is excess noise. It is not reproduced ten months later.
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All authors Alexis Lavail, Florian Debras, David Rogé Royo, Arturo López Ariste, Nicholas W. Borsato, Jean-François Donati, Pascal Petit, Julian D. Alvarado Gómez, Laurène Jouve, Claire Moutou, Andres Carmona, Baptiste Klein, Julia V. Seidel, Luc Arnold, Etienne Artigau, Clément Baruteau, Estelle Chabrol, Ryan Cloutier, Neil J. Cook, Nicolas B. Cowan, Xavier Delfosse, Neda Heidari, Eder Martioli, Adrien Masson, Joost P. Wardenier, Vincent Yariv
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Gravitational-wave Echoes Beyond the Hubble Time from Quantum Black Holes
Che-Yu Chen, Naritaka Oshita and Yuki Yokokura
We investigate gravitational-wave echoes in a horizonless compact object model, a non-perturbative solution of the semi-classical Einstein equation that reproduces the
entropy-area law from the bulk structure. By employing a model of anisotropic fluids in classical general relativity (GR), we show that odd-parity gravitational waves are not reflected at the object's surface but are trapped inside due to the exponentially strong
redshift, and that the echo-delay time extremely exceeds the age of the Universe. Consequently, the echo signals are effectively unobservable, which is consistent with current null results from echo searches. We finally discuss how this
quantum black hole and the conventional classical black hole could be distinguished observationally.
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Astrophysics of Galaxies
Cusps, cores, and one acceleration: dark-matter haloes versus modified dynamics across the full SPARC sample
Mikhael Da Silva
The rotation curves of the 175 disk
galaxies in the SPARC database are confronted, one by one and under identical conditions, with the two mass models that have dominated the missing-mass debate for four decades: a cold dark-matter
halo of Navarro-Frenk-White (NFW) form, and Milgromian dynamics (MOND) with the acceleration constant held at $a_0=1.2\times10^{-10}$ m s$^{-2}$. Stellar mass-to-light ratios, distances and inclinations are treated as nuisance parameters with priors set by the 3.6 $\mu$m photometry and by the SPARC error budget, and every
galaxy is sampled with a Markov-chain Monte Carlo. Three findings emerge. (i) Judged by the
Bayesian information criterion, the free NFW
halo is preferred in 96
galaxies and MOND in 79; once the
halo is required to obey the $\Lambda$CDM concentration-mass relation the score becomes 86 to 89, i.e. a draw. The two theories fail in different places: MOND loses in massive, high-surface-brightness, bulge-dominated systems, NFW loses in slowly rising dwarf rotation curves. (ii) The NFW concentrations demanded by the data sit a median 0.24 dex below the $\Lambda$CDM expectation, and 53% of the sample lies more than $2\sigma$ below it, independent of
halo mass; this is the core-cusp problem expressed as a scaling-relation offset rather than as a handful of anecdotes. (iii) The radial acceleration relation built from the full sample has $a_0=(1.13\pm0.02)\times10^{-10}$ m s$^{-2}$ and an observed scatter of 0.14 dex, yet the value of $a_0$ preferred by individual
galaxies spans more than a decade and correlates with surface brightness. The two statements are not in contradiction: the population-level relation is tight because it averages over exactly the degeneracies with mass-to-light ratio and distance that make $a_0$ ill-determined
galaxy by
galaxy. The full table of fits is provided.
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Solar and Stellar Astrophysics
From the Milky Way to the Early Universe: How Metallicity Shapes the Formation of Double Neutron Stars
Abhishek Chattaraj, Jeff J. Andrews, Monica Gallegos-Garcia et al. (+9 more)
Among the compact binaries detected through gravitational wave (GW) emission, double
neutron stars (DNSs) hold the unique distinction of having well-characterized local analogs in the Milky Way. However, understanding their broader cosmological population remains challenging due to the complex
metallicity-dependent
evolution of their progenitors. Using the detailed binary population synthesis code POSYDON, we model DNS formation across a cosmological range of
metallicities. We find that while DNSs are predominantly formed through common envelope
evolution,
metallicity-dependent radial expansion and stellar wind mass loss bifurcates the pathway into distinct subchannels, producing systematically distinct merging populations at different
metallicities. Notably, our best representative Galactic models predict local merger rates in broad agreement with the latest GWTC-5 constraints, suggesting that the populations observed via
radio pulsar surveys and through GW emission need not be in tension. Contrary to previous studies, we demonstrate that the intrinsic merger efficiency increases toward low
metallicities, a trend robust across varying binary
evolution assumptions, although the magnitude and the underlying stellar processes driving this enhancement vary across
metallicity regimes. When convolved with the
cosmic star formation history, our models reveal that the majority of merging DNSs originate from progenitors in the range $\sim 0.1\,Z_\odot - Z_\odot$, with significant supersolar contributions. Furthermore, we show that weaker stellar winds at low
metallicities produce DNS mergers with systematically more symmetric mass ratios ($q \gtrsim0.9$). Additionally, we assess detectability within proposed configurations for third-generation GW observatories. Our study provides a framework for interpreting the cosmological DNS population in the upcoming multi-messenger era.
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All authors Abhishek Chattaraj, Jeff J. Andrews, Monica Gallegos-Garcia, Max M. Briel, Michael Zevin, Tassos Fragos, Emmanouil Zapartas, David R. Aguilera-Dena, Seth Gossage, Anarya Ray, Philipp M. Srivastava, Zepei Xing
Solar and Stellar Astrophysics
Unravelling the Nature of AT 2025abao: From Precursor to Final Fate
Zhuo Chen, Yingzhen Cui, Tianshu Wu et al. (+9 more)
Luminous red novae (LRNe) are potential signatures of common envelope
evolution (CEE), a critical yet poorly understood phase in compact binary formation. AT 2025abao, an LRN in the Andromeda
galaxy, originated from an asymptotic giant branch (AGB) progenitor and exhibited a prolonged pre-outburst transient. Lacking direct constraints on the companion, however, the system's evolutionary fate remains unclear. Here, we unravel the binary nature of AT 2025abao by modeling its complete
evolution, from precursor to final outcome. We show that the eight-year infrared precursor arises from a $\approx1.4^{+0.2}_{-0.3}\,M_{\odot}$ main-sequence companion inspiralling through the wind of a $\approx 6.9\,M_{\odot}$ AGB
star. As CEE commences, the companion plunges into the envelope and launches a shock. Radiation hydrodynamic modeling of this outburst constrains the total ejecta mass to $\approx 0.92\,M_{\odot}$ and energy to $\approx 1.25\times 10^{47}\,$erg, revealing that only $\approx 0.57\,M_{\odot}$ becomes unbound. Subsequent radiative transfer simulations successfully reproduce the evolving spectral energy distribution. Crucially, our models indicate the main-sequence companion and AGB core survive in an eccentric orbit without merging at least 400 days after CEE onset. AT 2025abao may therefore be the first observed CEE event caught forming a close compact binary, bridging a long-standing observational gap in compact binary formation.
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All authors Zhuo Chen, Yingzhen Cui, Tianshu Wu, Yongzhi Cai, Hongwei Ge, Andrea Reguitti, Minxuan Cai, Lulu Fan, Ji-An Jiang, Tinggui Wang, Zelin Xu, Jie Lin
Cosmology and Nongalactic Astrophysics
Testing $\Lambda$LTB as an alternative to dynamical dark energy
Yukang Zhang and Pengjie Zhang
A cosmological constant $\Lambda$ in a universe weakly violating the cosmological principle (CP) can mimic a dynamical dark energy (DDE) in a FRW universe, and therefore challenging the recently reported DDE evidences. We test this scenario in the form of $\Lambda$LTB cosmology, against two data combinations. (1) DESI DR2 BAO, Planck CMB, together with any of the four SNe Ia compilations (UNION3, Pantheon+, DES SN5YR, and DES Dovekie) show no preference over DDE or $\Lambda$LTB. (2) The inclusion of the kinematic Sunyaev Zel'dovich (kSZ) effect rules out a large portion of the CP violation parameter space allowed by (1). However, the existence of a $\sim 300$ Mpc$/h$ region with $\sim 10\%$ matter density excess is still allowed by the current data, and therefore remains a viable alternative to DDE. To facilitate further tests, we present analytical expressions of the distance-
redshift relation and the kSZ effect in a universe with weak CP violation.
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High Energy Astrophysical Phenomena
A Physically Motivated Compact Parameterization of Neutron Star Atmosphere Emission for Thermal X-ray Pulse-Profile Modeling
Tong Zhao and Renxin Xu
Thermal X-ray pulse-profile modeling depends on the angular and spectral properties of
neutron star atmosphere emission. We construct a compact empirical approximation to the specific intensity using eight coefficients for the angular dependence and five for a normalized spectral kernel. The angular prescription is motivated by the formal solution of the radiative-transfer equation, while the spectral normalization preserves a specified bolometric flux. We calibrate this family to numerical atmosphere tables, focusing on return-current-heated and fully ionized hydrogen atmospheres. When incorporated into a semi-analytic pulse-profile model, the approximation reproduces profiles normalized by their phase-averaged flux to within approximately $4\%$ for antipodal hot spots and $5\%$ for non-antipodal hot spots in the tested heated-atmosphere configurations. We also analyze synthetic eXTP observations using different beaming prescriptions to test the conclusion in our previous work based on a linear description of the angular dependence of the emission. The comparisons suggest that the angular dependence of the intensity cannot be simply characterized by a linear function of the cosine value of the emission angle, because its detailed shape and energy dependence will affect the parameter inference. This parameterization can significantly increase the efficiency for analytic and numerical models, and provide a compact framework for examining how atmosphere assumptions affect
neutron star pulse profiles and the inferred stellar properties.
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Cosmology and Nongalactic Astrophysics
Constraints on Nonlinearity of the Mass-Concentration Relation
Nobuhiro Okabe
We develop a
Bayesian generalization of the previous method to constrain a wide variety of mass-concentration (M-C) relations motivated by both theoretical and observational studies. The framework incorporates the intrinsic scatter in concentration, nonlinear weak-
lensing (WL) calibration relations, the WL measurement-error covariance, and the underlying parent mass distribution. We employ
Hamiltonian Monte Carlo for computational efficiency. Our sample consists of 213 X-ray-selected clusters with WL measurements for the eRASS1, XXL, LoCuSS, and MCXC catalogs at 0<z< 0.9. For each subsample, we account for its specific WL calibration relation and underlying population distribution. We consider a conventional single power-law model, an empirical double power-law model, and four theoretical models calibrated against numerical simulations. The four theoretical M-C models comprise two in which concentration decreases with mass, distinguished by the sign of d^2ln c/d(ln M)^2, and two in which the concentration decreases with increasing mass before turning upward at high masses. Because the mass and
redshift ranges of our cluster sample do not extend into the upturn regime predicted by numerical simulations, we distinguish among the models primarily through the
curvature of their M-C relations. Regardless of which model is adopted, the inferred M-C relation is in good agreement with the results of recent numerical simulations. We find no statistically significant differences among the models above the $4\sigma$ level. However, the result shows a tendency toward a gradual flattening of the mass dependence toward higher masses. Specifically, a monotonically decreasing model with positive
curvature is preferred over the single power-law relation and a monotonically decreasing model with negative
curvature at the $2\sigma$ level and over three double power-law models at the $0.5-1\sigma$ level.
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Solar and Stellar Astrophysics
Fast and Differentiable MHD Surrogate for Solar Wind using Neural Operator
Prateek Mayank, Enrico Camporeale, Thomas E. Berger et al. (+2 more)
Global magnetohydrodynamic (MHD) simulations provide the complete
plasma state of the heliosphere, but their computational cost limits applications requiring repeated model evaluations. We introduce SNOW (Solar Neural Operator for Wind), a fast and differentiable surrogate for global MHD solar wind. SNOW combines a rotational ballistic approximation, a spherical harmonic neural operator, and causal radial context to autoregressively propagate all eight MHD variables from 20 to 240 Rs through consecutive shell to shell transitions. Trained and evaluated using AWSoM simulations spanning a solar cycle, SNOW remains stable across the complete rollout. The model successfully reproduces the large scale
plasma and
magnetic field structures, including fast and slow wind streams,
magnetic polarity sectors, vector orientations, fieldline connectivity, and bulk-flow structures. Additionally, the
magnetic divergence and induction diagnostics remain comparable to the reference MHD solutions. The complete three-dimensional solution is generated in less than one second on a single GPU. These results demonstrate the feasibility of fast neural emulation of global MHD solar wind solutions while retaining physically meaningful
plasma and
magnetic field structure.
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All authors Prateek Mayank, Enrico Camporeale, Thomas E. Berger, Zhenguang Huang, Gabor Toth