Earth and Planetary Astrophysics
Gardening on the Moon: An Advection-Diffusion Model to Guide the Search for Supernova Debris in the Lunar Regolith
Emily S. Costello, John Ellis, Brian D. Fields et al. (+2 more)
The vertical redistribution of materials in the lunar regolith - ranging from continuously produced space-weathering products to sporadic pulses of
supernova- or kilonova-derived isotopes - remains a fundamental problem in planetary science. We present a unified
stochastic model of regolith gardening induced by the impact flux. Treating gardening as a competition between impact-driven advection and
diffusion predicts the maturity profiles of Apollo cores over more than two orders of magnitude in time ($1.4 \times 10^7$ to $4.5 \times 10^8$ years). This model describes well the depth profiles of live Fe60 in Apollo regolith samples, suggesting that
supernova dust capture is independent of native iron abundance, and is consistent with a uniform influx at the latitudes of the Apollo landing sites. We extend our model to predict lunar signals for live r-process species that might originate from
supernovae or kilonovae: Pu244 tied to terrestrial detections, and I129, Hf182, and Cm247 based on r-process calculations. The Pu244/Fe60 depth profile can probe the origin of Pu244, motivating searches in Artemis regolith samples down to depths O(100) cm.
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All authors Emily S. Costello, John Ellis, Brian D. Fields, Rebecca Surman, Xilu Wang
Astrophysics of Galaxies
The k-MENDEL sample of local analogs to reionization galaxies. Spectral identification of EELGs and properties of green peas in DESI
L. Bonatto, R. Amorín, A. Giménez-Alcázar et al. (+7 more)
Low-mass
galaxies with intense starbursts exhibit spectra dominated by extreme nebular emission and faint
stellar continua. These extreme emission-line
galaxies (EELGs) are key laboratories to study
star formation, feedback, and ionizing
photon escape in low-
metallicity environments. We exploit the DESI survey to assemble the k-Means of Extreme Nebulae from DEsi outLiers (k-MENDEL), a statistically robust sample of ~16,000 EELGs at 0.01 < z < 0.96 selected via automatic k-means classification. Using SED fitting and Te-based
metallicities, we characterize EELGs including "blueberry" and "green pea"
galaxies, spanning
stellar masses of 10^6-10^10 Msun and SFRs of 0.1-100 Msun/yr. k-MENDEL extends previous SDSS samples toward higher
redshifts and lower
metallicities (12+log(O/H) ~ 7.0-8.5). EELGs lie systematically above the
star-forming main sequence, with sSFRs up to ~100 Gyr^-1. They follow a shallower mass-
metallicity relation offset by 0.3-0.5 dex from local relations, closely resembling young
galaxies observed with JWST at z > 3-10. The large intrinsic
metallicity scatter, even after projecting along the fundamental
metallicity relation, indicates strong departures from simple "bathtub" models, suggesting massive inflows of metal-poor gas followed by strong feedback. While ~6% of the sample shows AGN-like signatures, the most extreme
star-forming systems reach high ionization (O32 ~ 5-60) comparable to confirmed Lyman-continuum emitters. Our results support the interpretation of EELGs as short-lived, non-
equilibrium phases in the
evolution of low-mass
galaxies and highlight their importance as nearby analogs of
galaxies likely driving
cosmic reionization (Abridged).
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All authors L. Bonatto, R. Amorín, A. Giménez-Alcázar, J.A. Fernández-Ontiveros, A. Hernán-Caballero, S. Suárez, J.M. Vílchez, E. Pérez-Montero, M. Llerena, J. Sánchez Almeida
Instrumentation and Methods for Astrophysics
IFS spectrograph designs for the Wide-field Spectroscopic Telescope: Architecture and performance gains from curved sensors
Corentin Cudennec, Alexandre Jeanneau, Roland Bacon et al. (+2 more)
The Wide-field Spectroscopic
Telescope (WST) is a proposed 12-meter segmented facility optimized for seeing limited observations in the visible and designed to operate both a high-multiplex multi-object spectrograph and a panoramic integral field spectrograph (IFS). The WST IFS concept builds on instruments such as MUSE at the VLT (Very Large
Telescope), using field splitters and image slicers to reformat a large field into pseudo-slits feeding spectrographs with two optimized spectral channels. This paper presents the spectrograph architecture developed for the WST IFS, aiming to achieve high through put and image quality over a wide wavelength range in a cost-effective manner. We investigate the use of curved detectors as a means to simplify the spectrograph layout, reduce aberrations, and potentially improve efficiency. This study establishes a promising baseline for the IFS spectrographs and assesses the benefits of incorporating curved sensors that can guide the development of future large-scale integral field spectrographs.
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All authors Corentin Cudennec, Alexandre Jeanneau, Roland Bacon, Thierry Lépine, Matthew Lehnert
Earth and Planetary Astrophysics
Finding Circumbinary Planets: A Semi-Automated Transit Search of TESS Eclipsing Binaries
Benjamin D. R. Davies, David J. A. Brown, Samuel Gill et al. (+1 more)
The discovery of circumbinary
planets (CBPs) has advanced our understanding of
planet formation and dynamical
evolution in complex environments. However, the population of such
planets remains small, leading their underlying physical properties to be loosely constrained. In this work, we have developed a semi-automated framework to identify planetary transit events in light curves of eclipsing binaries observed by the Transiting
Exoplanet Survey Satellite (TESS). Our search method, ${\tt mono-cbp}$, removes
stellar eclipses and applies a custom detrending procedure, searching for individual transit events and applying automated vetting procedures to filter false positive signals. We searched a sample of binaries from the TESS Eclipsing Binary Catalogue, yielding one candidate transit event. ${\tt mono-cbp}$ was also tested on the known population of transiting CBPs, using the Kepler long-cadence photometry for the Kepler transiting CBPs and the TESS Full Frame Image photometry for the TESS CBPs. Excluding transits that are shallower than the intrinsic noise of the Kepler/TESS data, ${\tt mono-cbp}$ achieved a recovery rate of $\geq50$ per cent for each
planet, reaching >75 per cent for 9 of the 14
planets. To test the limits of our framework, we injected simulated transit profiles with varying depth and duration into our sample of TESS light curves, finding that our recovery rate is a strong function of transit duration and the metrics used to filter false positive signals. This framework may be applied to large samples of TESS eclipsing binaries with little computational burden and to photometry from future space-based photometric surveys.
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All authors Benjamin D. R. Davies, David J. A. Brown, Samuel Gill, Jenni R. French
High Energy Astrophysical Phenomena
Blueshifted lines from the inner accretion disc's rotation can explain quasar absorption "forests”
Amelia M. Hankla, Fergus J. E. Baker, Daniel R. Wilkins et al. (+1 more)
Recent XRISM observations of active
galactic nuclei such as PDS 456 have revealed “forests” of absorption lines best modeled by five distinct absorption zones with varying large blueshifts. We propose a model in which these relativistic blueshifts originate from the motion of the
accretion disc itself, rather than from a clumpy super-Eddington
outflow at hundreds of gravitational radii $r_g\equiv GM/c^2$. We demonstrate that thin rings of absorbing material lying just above the
accretion disc at varying radii can produce the observed energy shifts and separations of the absorption zones. In this model, the PDS 456 transmission spectrum is well reproduced by rings with widths $\Delta r\lesssim1r_g$ at locations between the black hole's innermost stable circular orbit (ISCO) and $\approx15r_g$. This model suggests that the absorption forests seen in XRISM observations can probe the surface structure of the innermost ($\lesssim15r_g$) regions of
quasar accretion discs.
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All authors Amelia M. Hankla, Fergus J. E. Baker, Daniel R. Wilkins, Andrew C. Fabian
Instrumentation and Methods for Astrophysics
Large or bright satellite constellations: Effects on observations, including on the background sky brightness
Olivier R. Hainaut
This study evaluates the effect of proposed constellations – ranging from current deployments to mega-constellations and very bright reflector concepts – on direct trail losses, diffuse background, and scattered sky brightness. We use a numerical model for Mie and Rayleigh scattering in the V band, adapted from moonlight sky-brightness calculations and validated against observations of moonlight and
stellar background light. This is combined with the SatConAnalytic package to quantify scattered light, diffuse light from undetected satellites, and direct losses from detected trails. Constellations comprising approximately 60,000 satellites that adhere to the V_550km > 7 recommendation exert a negligible effect on sky brightness, contributing only about 10^-4 of the natural dark sky. Conversely, mega-constellations with 10^6 satellites render trails pervasive. Bright satellites, such those from AST SpaceMobile, significantly impact saturating detectors even when their number is moderate. Extremely bright satellites pose a far more severe threat: a 5000-satellite Reflect Orbital-like constellation elevates the scattered sky background by 20%-30%, and a population of 50,000 increases it by 200%-300%. The constellations currently proposed for launch, over 1,700,000 objects and including satellites brighter than V_550km = 7, would substantially degrade observations. Maintaining satellite brightness below V_550km = 7 is important for all instruments, but critical for safeguarding saturating instruments, such as the VRO LSST camera and for limiting sky-background pollution. Even under this constraint, the total satellite population must remain below ~100,000 satellites to ensure that field-of-view losses do not exceed typical technical downtime.
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Cosmology and Nongalactic Astrophysics
Analytic compression of the effective field theory of the Lyman-alpha forest
N. G. Karaçayl{\i}, M. Ivanov, R. de Belsunce et al. (+3 more)
The 1D flux power spectrum ($P_{\mathrm{1D}}$) of the Ly$\alpha$ forest provides an exceptionally high-resolution probe of structure formation down to small scales ($k\approx1-10~\text{$h~$Mpc$^{-1}$}$). These scales carry the imprints of massive
neutrinos, warm dark matter, and the running of the
primordial power spectrum spectral index. The effective field theory (EFT) is a promising perturbative approach to systematically and efficiently describe the Ly$\alpha$ forest, but it faces challenges in its application to $P_{\mathrm{1D}}$, as many EFT parameters become degenerate when projected along the line of sight. In addition, this projection generates new
stochastic terms from the integration over small-scale modes. In this work, we address these issues by compressing the EFT model space using the Fisher
matrix formalism and linearizing the resulting compression directions, enabling analytic template marginalization and significantly reducing the computational cost of likelihood evaluation. We use hydrodynamical simulations to obtain a baseline estimate of EFT parameters, and use the DESI DR1 $P_{\mathrm{1D}}$ measurements to derive compression directions. We then marginalize over deviations from the baseline using these compression directions and forecast the constraining power of our formalism. We find that even in conservative scenarios where each data
redshift bin requires its own set of EFT parameters, the cosmological constraints saturate with the linear bias, two leading-order 1D
stochastic terms, and three principal combinations of the remaining EFT templates. In this case, our forecasted precision of the amplitude ($\Delta^2_p$) and the logarithmic slope ($n_p$) of the linear matter power spectrum at the pivot scale ($k_p=0.7~\text{Mpc}^{-1}$) is $10\%$ and $2.0\%$, respectively, which is similar to emulator-based analyses that include observational data systematics.
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All authors N. G. Karaçayl{\i}, M. Ivanov, R. de Belsunce, C. Ravoux, J. M. Sexton, Z. Lukić
Instrumentation and Methods for Astrophysics
Enhancing event reconstruction for $\gamma$-ray particle detector arrays using transformers
Markus Pirke, Youngwan Son, Jonas Glombitza et al. (+3 more)
Gamma-ray astronomy from hundreds of GeV to PeV is confined to ground-based experiments that detect air showers induced by $\gamma$-rays entering Earth's atmosphere. While particle detector arrays feature huge detection areas, accurately reconstructing the primary particle properties is difficult due to the sparse sampling of the air shower and its intrinsic fluctuations. In this work, using simulations of a future water-Cherenkov array, we investigate two end-to-end deep learning approaches based on the
transformer architecture with different computational complexities that utilize calibrated raw data. We
benchmark both methods against well-established methods in the field in terms of $\gamma$-
hadron separation, angular, core, and energy reconstruction. Our results show significant improvements across the whole energy range, particularly at low and intermediate energies. This work is the first to consistently demonstrate improved performance in both event reconstruction and $\gamma$-
hadron separation using a single architecture.
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All authors Markus Pirke, Youngwan Son, Jonas Glombitza, Martin Schneider, Ian James Watson, Christopher van Eldik
Astrophysics of Galaxies
Paschen Jumps in Little Red Dots: Evidence for Nebular Continua
Albert Sneppen, James H. Matthews, Darach Watson et al. (+6 more)
”Little Red Dots” (LRDs) are broad-line sources at high
redshift, initially identified by their compact morphologies, red colours and prominent Balmer breaks. The origin of their optical-to-near-infrared continua is debated, with proposed explanations ranging from direct recombination emission to thermalised blackbodies from
stellar-like atmospheres. Here we report evidence for Paschen jumps in a subset of LRDs, consistent with free-bound recombination to hydrogen $n=3$. The Paschen and Brackett continuum shapes across the sample are consistent with minimally reddened emission from low-temperature gas with $T_e\lesssim10\,000$ K, while the presence of Paschen jump signatures limits scenarios in which the emission is thermalised. Further, the extreme H$\alpha$ equivalent widths and the tight observed correlation between H$\alpha$ and the continuum follow naturally if both originate in recombination emission. This provides an observational upper limit on the contribution of any direct AGN
accretion component and any
stellar-atmosphere-like component, as well as on the fraction of line emission that can be thermalised as it traverses the cocoon. Ultimately, nebular radiative-transfer models provide a self-consistent explanation of the continuum, line strengths and line profiles without requiring multiple separately fitted components.
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All authors Albert Sneppen, James H. Matthews, Darach Watson, Alex J. Cameron, Stuart A. Sim, Joris Witstok, Gabriel B. Brammer, Kasper E. Heintz, Georgios Nikopoulos
High Energy Astrophysical Phenomena
A TeV-based Determination of the Local Extragalactic Background Light and its Consistency with Galaxy Counts and Direct Measurements
J. Baxter, A. Dominguez, J. D. Finke et al. (+5 more)
The extragalactic background light (EBL), the cumulative radiation from all extragalactic sources, traces
galaxy formation and
cosmic evolution. High-energy $\gamma$ rays attenuated via pair production with EBL
photons are a powerful probe of the EBL. In this work, we use very-high-energy (VHE; $E_\gamma > 100\,\mathrm{GeV}$) $\gamma$ rays to measure the local EBL intensity and test its consistency with
galaxy counts and direct measurements. Our analysis employs a sample of 268 spectra from 45 sources observed with Imaging Atmospheric Cherenkov
telescopes. A model-dependent study shows seven EBL templates require only $\le 10\%$ rescaling to fit the observed $\gamma$-ray attenuation. The
galaxy-count-anchored model gives the closest match. We then derive template-marginalized TeV optical depths from a representative model subset. We combine them with
Fermi-LAT GeV measurements to reconstruct the EBL at $z = 0$ using empirical and physically motivated models. The two reconstructions agree and follow the integrated
galaxy light to within $2$–$3\,\mathrm{nW\,m^{-2}\,sr^{-1}}$ (typically $<25\%$) over $0.5$–$30\,\mu$m. Both are consistent with low-zodiacal-light observations, including outer
solar system and dark cloud measurements. In contrast, the near-IR excess reported by IRTS and CIBER exceeds our reconstructed intensity by $3$–$5\sigma$, implying an additional $\gtrsim 5$–$10\,\mathrm{nW\,m^{-2}\,sr^{-1}}$ incompatible with the $\gamma$-ray optical depths. Combined with GeV constraints on EBL
evolution to $z \simeq 4$, these TeV optical depths provide a VHE-anchored determination of the local EBL intensity. The agreement with
galaxy counts and deep-space measurements indicates that known
galaxy populations account for most of the optical and near-IR background, leaving limited room for an additional diffuse component.
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All authors J. Baxter, A. Dominguez, J. D. Finke, A. Desai, M. Ajello, A. Banerjee, Dieter Hartmann, Vaidehi S. Paliya
Earth and Planetary Astrophysics
NCCR PlanetS: Observational and computational characterization of exoplanet atmospheres
Daniel Kitzmann, Elspeth K. H. Lee, Jens Hoeijmakers et al. (+1 more)
This chapter reviews the current state of observational and theoretical efforts in the characterization of
exoplanet atmospheres, with a focus on developments enabled through the Swiss National Centre for Competence in Research (NCCR)
PlanetS. It covers the essential physical and chemical processes that govern atmospheric dynamics, radiative transfer, chemistry, and cloud formation in
exoplanets and brown
dwarfs. The review discusses the modeling approaches used to simulate these processes, ranging from simplified 1D models to fully coupled 3D general circulation models. Atmospheric
retrieval frameworks are presented as tools for inferring atmospheric properties from observational data, highlighting both classical
Bayesian techniques and emerging machine learning methods. Observational strategies using instruments like HST, JWST, and ground-based high-resolution spectrographs are also examined. Special emphasis is placed on the interplay between theory and observation, and how developments in modeling, data analysis, and instrumentation collectively advance our understanding of planetary atmospheres beyond the
Solar System.
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All authors Daniel Kitzmann, Elspeth K. H. Lee, Jens Hoeijmakers, Kevin Heng
Earth and Planetary Astrophysics
Nii-body: Bayesian Inference of Multiplanet Dynamics via N-body Simulations
Hong-Fei Jia, Sheng Jin, Dong-Hong Wu et al. (+1 more)
Many exoplanetary systems are multiplanet configurations whose long-term dynamics are governed by N-body gravitational interactions. Consequently, their detection signatures cannot be adequately described by Keplerian orbits. Accurately interpreting the observational data of these systems – including radial velocity (RV), astrometry, and transit timing variations (TTVs) – requires N-body integration. Motivated by this need, we developed a
Bayesian fitting framework that couples N-body integration with Markov chain Monte Carlo (MCMC) to retrieve the system parameters of multiplanet systems. The code, named Nii-body, integrates an adaptive Runge–Kutta–Fehlberg 7(8) (RKF78) solver with an automated parallel tempering MCMC
algorithm. Using simplified synthetic astrometric observations, we evaluated the efficiency and robustness of Nii-body's N-body orbit
retrieval on an idealized two-
planet model, demonstrating its potential for future application to real observational data. The N-body fitting workflow can be readily extended to RV, TTVs, or combined
datasets, providing a versatile engine for high-precision orbital inference in multiplanet systems.
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All authors Hong-Fei Jia, Sheng Jin, Dong-Hong Wu, Shang-Fei Liu
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
CMB signatures of gravity-mediated dark radiation in $\mathbf{\Delta N_{\rm eff}}$
Anish Ghoshal, Sk Jeesun and Kazunori Kohri
Measurement of $N_{\rm eff}$ in the CMB (
Cosmic Microwave Background) observations, like Planck 2018 and BBN (Big Bang Nucleosynthesis) has already set stringent constraints on the interaction strength of light particles beyond the Standard Model (BSM). Despite such negligible couplings of such BSM particles to the visible sector, they are inevitably produced in the early universe through
gravity-mediated processes. If a sizable density of light particles survives around CMB formation, they may act as dark radiation (DR) contributing to $N_{\rm eff}$ at CMB epoch. In this work, we study the production of such light BSM particles through the
gravity-mediated scatterings in an effective field theory (EFT) setup assuming that all non-gravitational couplings of the BSM particle are negligible. Since the production is sensitive to the
spin of the produced particle, we perform a concrete analysis for two representative cases: scalar dark
Higgs DR and vector dark
photons DR.Using the Planck 2018 observations, we find constraints on the reheating temperature ($T_{\rm RH}$) and background equation of state ($w_\Phi$) during reheating in such scenarios featuring dark
Higgs and dark
photon. A comparative discussion involving
gravity-mediated production of Dirac right-handed
neutrinos ($\nu_R$) and light
axion-like particles (ALP) is also presented. Finally, for completeness, we also analyze the scenario where the production occurs through a generic
spin-2 mediator characterized by an effective scale $\Lambda$ delineating the parameter space that is currently ruled out from Planck-2018 and can be probed by the future CMB experiments like LiteBird, Simon Observatory, CMB-S4, CMB-HD.
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Astrophysics of Galaxies
Constraining the Molecular Kennicutt-Schmidt Relation with Multi-Transition CO Observations of Nearby Galaxies
Victoria G. G. Samboco and Ryan P. Keenan
The relationship between the
star formation rate surface density and the molecular gas surface density in
galaxies is key to understanding
galaxy evolution. To investigate the molecular Kennicutt-Schmidt (K-S) relation and its dependence on gas density, we analyze a uniform sample of 36 nearby
galaxies from the AMISS survey, focusing on the CO(1-0), CO(2-1), and CO(3-2) transitions, which trace progressively denser and warmer molecular gas. Using statistical methods that combine binning with Markov Chain Monte Carlo (MCMC) fitting, we derive the slope, scatter, and intercept of the $\Sigma_{\mathrm{SFR}}$-$\Sigma_{\mathrm{CO}}$ relation for each transition. We find power-law slopes of 1.26, 1.14, and 1.07 for CO(1-0), CO(2-1), and CO(3-2), respectively, consistent with a trend toward increasingly linear
star formation relations at higher-J transitions. This behavior supports the idea that denser gas is more directly linked to ongoing
star formation and is consistent with previous findings of near-linear correlations between HCN or high-J CO luminosities and global SFR. The observed trend suggests an underlying relation between gas and SFR volume densities with a power-law index of $\sim$1.5, indicating enhanced
star formation efficiency in denser environments. These findings underscore the critical role of dense gas in regulating
star formation and highlight the importance of tracer selection and excitation conditions when interpreting the K-S relation across different environments.
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Astrophysics of Galaxies
A first [CII] view of high-z quiescent galaxies
C. D'Eugenio, E. Daddi, R. Gobat et al. (+10 more)
We present ALMA detections (or stringent upper limits) of the [CII] 158 $\mu m$ emission line and underlying
dust continuum from five massive quenched
galaxies (QGs) at 2<z<4.7. We find extreme variations in the molecular gas fractions ($\rm{f_g=M_{mol}/M_{\star}}$), spanning 0.1%-25%, if a standard $\rm{\alpha_{[CII]}}$ applies. We attempt a first empirical calibration of $\rm{\alpha_{[CII]}}$ with respect to
dust continuum in a $z=2$ lensed QG and with respect to CO(3-2) in a $z=3.1$ QG, finding no evidence of strong deviations from the standard value.
Dust continuum measurements, coupled with JWST/MIRI fluxes, suggest higher
dust temperatures compared to expectations from $z<2$ QGs, reaching $T_{d}\sim40-50 \,K$ in two
galaxies. Coupled with remarkably high total infrared luminosities (LIR) not explained by observed JWST colors not by energy balance based on literature
dust extinction measurements, and with [CII] deficits down to $\rm{[CII]/LIR\sim 2\times10^{-4}}$ typical of (Ultra)Luminous Infrared
Galaxies, our findings point to additional
dust-heating mechanisms other than
dust-absorbed
stellar radiation. Surprisingly, JWST/NIRCam and ALMA imaging reveal widespread disturbed
stellar morphologies and offsets/tails in
dust and gas, indicative of ongoing interactions. While larger samples are needed to assess how common these features are in high-z QGs, these findings support a merger-driven origin for the phenomenology observed in these systems, with key similarities with respect to local post-starburst
galaxies where low-velocity shocks and
turbulence also inject energy into the residual ISM.
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All authors C. D'Eugenio, E. Daddi, R. Gobat, S. Jin, D. Liu, H. Sun, F. Gentile, F. Bruckmann, Z. Liu, I. Delvecchio, L. Vallini, B. Magnelli, A. Zanella
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Probing Solar Symmetrons with Direct Detection
Hannah Banks, Anne-Christine Davis and Luca Visinelli
We provide the first investigation of the
solar production of symmetrons, a well-motivated class of screened scalar fields with density dependent couplings to the Standard Model, and their subsequent absorption in underground direct detection experiments. We compute the flux of symmetrons produced through
photon conversion in the
magnetic field of the
solar tachocline, and constrain the resulting luminosity to not exceed 3% of the observed
solar output. Even under the conservative assumption that production occurs only in the tachocline, this criterion yields robust astrophysical bounds on previously uncharted regions of symmetron parameter space, and predicts a keV-scale symmetron spectrum at Earth. We then derive the corresponding absorption signal in
liquid xenon detectors, where symmetrons can interact with electrons through both conformal and disformal couplings. Using binned data from XENONnT, we obtain new direct-detection limits that are complementary to the
solar luminosity constraint, further tightening the viable symmetron parameter space. Our results demonstrate that the Sun provides a testable, previously unexploited, source of symmetrons, and highlight that the interplay of astrophysical and laboratory searches offers a powerful strategy for probing screened scalar theories.
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Earth and Planetary Astrophysics
Detecting nitrogen-carriers in the inner regions of protoplanetary disks
Marissa Vlasblom, Aditya M. Arabhavi, Niels de Klerk et al. (+3 more)
Nitrogen is a key element for building habitable worlds, yet only a small fraction of the available N-budget of
planet-forming disks has been detected. In particular, the lack of any IR NH$_3$ detection is striking, as this molecule is predicted to be rather abundant in the warm, inner regions of protoplanetary disks, and therefore potentially readily incorporated into (
giant)
planets' atmospheres. We present a combined modeling and observational study of N-bearing molecules in
planet-forming disks, using detailed thermo-chemical disk models that investigate the sensitivity of N-containing molecules to the bulk elemental composition of the disk. Our models predict a strong increase in HCN flux with high C/H, and conversely a strong increase in flux from NO when O/H is high. The flux from NH$_3$ is not very sensitive to O/H, but does decrease at high C/H due to competition with HCN. However, the absolute NH$_3$ flux predicted by our model is not large enough to be detected with JWST-MIRI, even when N/H is enhanced by an order of magnitude. The flux from NO, on the other hand, is potentially detectable, and could therefore provide further insights into the N-budget of the inner disk. Using a cross-correlation technique, we search for NH$_3$ and NO detections in three disks, GW Lup, Sz 98, and V1094 Sco. We do not find any NH$_3$ detections, and only one tentative NO detection in V1094 Sco, though this needs further study to be confirmed. Additionally, we demonstrate that future facilities in the FIR may provide a better opportunity to detect NH$_3$ and thereby draw a comparison to the NH$_3$ budget known to be present in interstellar ices.
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All authors Marissa Vlasblom, Aditya M. Arabhavi, Niels de Klerk, Inga Kamp, Benoît Tabone, Ewine F. van Dishoeck
Earth and Planetary Astrophysics
The Illusory Precision of TTV Masses: Hidden Solutions Behind Kepler-9's Tight Mass Ratio
Sheng Jin, Dong-Hong Wu, Xiao-Ling Xu et al. (+1 more)
Transit timing variations (TTV) are considered a tool for constraining the masses of transiting
planets in the absence of radial-velocity data. Although theoretical studies have long revealed that TTV mass determinations intrinsically suffer from degeneracies, existing analyses of TTV data typically report a single-mode solution under a model with a specified number of
planets. This is because fitting TTV curves in the high-dimensional solution space of TTV posterior is extremely challenging; even locating a single solution requires substantial computational resources. We developed an efficient mode-first searching
algorithm that can locate multiple solutions in a single MCMC run. We applied this
algorithm to Kepler-9 b and c, which have the highest-quality TTV data. We found that the observed TTV can be reproduced by many combinations of planetary masses spanning a broad range, rather than the previously assumed precise determination. The mass of Kepler-9 b can range from 31.6 to 47.1 $M_{\oplus}$, while that of Kepler-9 c can range from 21.8 to 32.3 $M_{\oplus}$, and even more broadly under looser constraints. These degenerate solutions follow a linear relationship under a tight mass ratio between the two
planets, consistent with previous theoretical predictions. Furthermore, we demonstrate that achieving a globally converged posterior distribution for Kepler-9's TTV is impossible using a sampling
algorithm that preserves the Markovian property. This underscores the need for caution when interpreting results from sampling
algorithms that lack mathematical guarantees of global convergence.
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All authors Sheng Jin, Dong-Hong Wu, Xiao-Ling Xu, Jianghui Ji
Earth and Planetary Astrophysics
Long-period transiting exoplanets: advances in detection and characterization
Solène Ulmer-Moll, Babatunde Akinsanmi and Simon Müller
Most detected transiting
planets have orbits which would fit within the one of Mercury, exposing them to intense
stellar irradiation and interactions that significantly alter their properties. In contrast, colder
planets with longer orbital periods are less affected, offering crucial insights into their formation and migration histories. Characterizing transiting warm and temperate
planets is a key missing piece in the
exoplanet puzzle. Dedicated photometric and spectroscopic follow-up of transiting events detected in space-based photometric data opened the way to detecting long-period transiting
exoplanets. The wealth of information available for these transiting
planets makes them golden targets for in-depth characterization. For
giant planets, combining precise masses, radii, and ages with state-of-the-art planetary
evolution models allows the estimation of their planetary bulk compositions, a crucial element to explore their formation and
evolution pathways. Furthermore, these
planets are compelling candidates for hosting moons and circumplanetary rings-features that could illuminate dynamical histories, satellite formation processes, and even potential habitable environments.
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Instrumentation and Methods for Astrophysics
Unseen Astronomy
Dr James W. Trayford
The 2025 UK National Astronomy Meeting (NAM) in Durham played host to a session titled "Unseen Astronomy", involving a variety of astronomy researchers in diverse fields. This unique meeting focussed on a number of novel projects exploring alternatives to purely visual means of display in Astronomy, encompassing spheres of education, communication and research, and straddling both accessible and general use applications. The successful inclusion of such a session at a major conference reflects the explosion of interest in
multimodal astronomy in recent years, and hints at its transformative potential. Here, I aim to outline and motivate the topic of multi-modal science and consider its exciting potential. I will discuss this in the context of our own work in the area, the community building being undertaken to bring together researchers considering multi-modality, and efforts to impact astronomy at large.
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Astrophysics of Galaxies
Methanimine as a sink in the HCN and HNC solid state hydrogenation network
Joan Enrique-Romero and Thanja Lamberts
We aim to provide a systematic and quantitative description of the hydrogenation network connecting HCN and HNC to methylamine on interstellar water ices, while identifying dominant pathways and bottlenecks. To this end, we performed a comprehensive
quantum-chemical investigation of H-addition, H-abstraction, reactions with H2, and water-assisted H-transfer isomerization, covering intermediates linking HCN and HNC to CH3NH2. Calculations were carried out on amorphous solid water clusters of 14 molecules. Using benchmarked density functional theory, we derived activation barriers, elucidated mechanisms, and determined the binding energy distribution of H2CN and CNH2, also assessing deuterium substitution effects. H-addition reactions generally involve activation barriers, except for radical species. Considering both barrier heights and tunneling crossover temperatures, the most favorable sequence originates from HNC rather than HCN. The network evolves toward methanimine (H2CNH), the central species, or the singlet carbene HC:NH2, from which further hydrogenation leads to methylamine. Along these paths, several reactions are barrierless, while some H-abstraction processes compete with addition. Reactions involving H2 are uncommon, as most are endoergic. Deuterium substitution weakly affects classical barriers but significantly influences tunneling efficiencies. Our results support efficient formation of methanimine and methylamine from HNC on cold interstellar ices, with methanimine acting as a chemical sink, whereas HCN is less reactive and more likely to persist. These findings provide quantitative constraints for astrochemical models.
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High Energy Astrophysical Phenomena
The evolution of the mid-infrared spectrum of SN 1987A observed with the JWST/MIRI-MRS
P. J. Kavanagh, M. J. Barlow, C. Fransson et al. (+19 more)
Supernova (SN) 1987A provides a unique laboratory for investigating many aspects of SN physics and
evolution. An observation at Day 12927 (35.4 yr) since the explosion with the Mid-Infrared Instrument (MIRI) Medium Resolution Spectrometer (MRS) on the James Webb Space
Telescope (JWST) provided the first spatially resolved spectroscopic study of SN 1987A in the mid-IR, yielding insights into the
evolution of
dust, the ejecta, the equatorial ring (ER), and shocks in the system. Here we present a second epoch with MIRI/MRS at Day 13311 (36.4 yr) allowing the mid-IR spatially resolved spectroscopic temporal
evolution of SN 1987A to be probed for the first time. Analysis of the ER-dominated
dust continuum showed little
evolution between Days 12927 and 13311. However, a spatial analysis reveals the inner ER to be fading while the outermost regions are brightening. Broad ejecta emission lines detected at Day 12927 are evolving rapidly, driven by the recent onset of the ejecta/equatorial ring interaction in the northeast and southwest of the ER. Most lines from the ER show no change during the 384 days between the epochs, though some such as [Ne II] and [Ar II] have faded. We identify mid-IR H2 emission associated with the ejecta for the first time. Using the near- and mid-IR [Fe II] lines as density and temperature diagnostics of the ejecta in the interaction region we find it likely that the dense inner Fe-rich ejecta has now reached the reverse shock. Continued monitoring of SN 1987A is essential to observe the evolving ejecta/ER interaction and
dust components.
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All authors P. J. Kavanagh, M. J. Barlow, C. Fransson, J. Larsson, M. Matsuura, B. Sargent, O. C. Jones, M. Meixner, R. Wesson, J. A. D. L. Blommaert, P. Bouchet, A. Coulais, R. Gastaud, R. D. Gehrz, N. Habel, A. S. Hirschauer, J. Jaspers, R. P. Kirschner, L. Lenkic, O. Nayak, S. Rosu, T. Temim
Astrophysics of Galaxies
An automated method for planetary nebula detection with SIGNALS: first applications to NGC 4214 and NGC 4449
Nancy Yang, Johanna Hartke, Martin Bureau et al. (+11 more)
Utilising the optical imaging
Fourier transform spectrograph SITELLE, the
Star-formation, Ionized Gas and Nebular Abundances Legacy Survey (SIGNALS) is designed to study the connection between
star-forming regions and their environments. Targeting $31$ local
star-forming
galaxies, its data products also lend themselves to planetary nebula (PN) surveys. We present here a new pipeline to find PNe using automated emission-line diagnostics and morphology tests, that is able to distinguish PNe from contaminants with an accuracy similar to that of past visual methods. We also perform thorough completeness tests using mock PNe inserted into the data cubes with full spectra. We apply these tools to a pilot sample of two
dwarf irregular
galaxies from the SIGNALS survey, NGC 4214 and NGC 4449, with other
galaxies to follow. For these two
galaxies, we identify $25$ PNe (including $6$ new discoveries) and $23$ PNe (including $13$ new discoveries), respectively, and calculate PN luminosity function distances of $3.09^{+0.25}_{-0.46}$ and $3.91^{+0.33}_{-0.52}$ Mpc, respectively, the latter consistent with previous estimates. We also calculate the bolometric PN specific frequency of our
galaxies ($\alpha_\mathrm{bol}$), as well as a newly defined $V$-band PN specific frequency ($\alpha_\mathrm{V}$) based solely on the
galaxies' total luminosities in that band.
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All authors Nancy Yang, Johanna Hartke, Martin Bureau, Chiara Spiniello, Louis-Simon Guité, Guy Flint, Magda Arnaboldi, Ana Inés Ennis, R. Pierre Martin, Thomas Martin, Carmelle Robert, Laurie Rousseau-Nepton, Lucas M. Valenzuela, Sébastien Vicens-Mouret
Solar and Stellar Astrophysics
Tracing the s-Process: Spectroscopic Insights into Chemical Abundances in O- and C-rich Evolved Stars
Sophie Van Eck, Carlos Abia and Inma Dominguez
Oxygen and carbon-rich AGB
stars - and objects directly polluted by them - are excellent laboratories to investigate the nucleosynthesis and mixing processes occurring during the later phases of the of low- and intermediate-mass
star evolution. The determination of the abundances of several s-elements is a key tool for constraining theoretical AGB models. This contribution discusses the main results, recent advances, and current problems on this subject.
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Astrophysics of Galaxies · Cross-listed from physics.plasm-ph
Pressure gradient-driven plasma flows and magnetogenesis
Zain H. Saleem and Hamid Saleem
We present a self-consistent two-fluid theory demonstrating that pressure gradients simultaneously generate
plasma flows and
magnetic fields. We show that compatibility between ion momentum balance and mass conservation imposes a previously unrecognized constraint on
plasma evolution: the total pressure must satisfy the Laplace equation, $\nabla^2 p = 0$. This condition yields a class of exact analytical solutions in which pressure-driven flows and Biermann-type
magnetic fields emerge together. Application of the model to a
galactic gas clump reveals that, under thermal pressure, electrons and ions move almost together, giving rise to weak currents and consequently very small seed
magnetic fields. Ion dynamics are also important for determining the seed
magnetic-field generation time $\tau_B$ and for estimating the ion flow velocity. The model is further applied to
laser-produced
plasma to describe its short-time
evolution. The present theory provides a unified, self-consistent description of pressure-driven flow generation and magnetogenesis in both astrophysical and laboratory
plasmas.
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Earth and Planetary Astrophysics
Terrestrial planet formation in the era of GPU computing
Simon L. Grimm and Joachim G. Stadel
In this chapter, we summarize the underlying numerical methods needed for efficient $N$-body integration of planetary systems. We discuss how
symplectic integrators have been developed to tackle the complementary problems of long-term orbital integration and short-term collisional interactions. The public code GENGA, a parallel GPU/CPU
planet formation and orbital dynamics simulation code, was developed to unify these methods and take full advantage of the newest available computing hardware. We present state-of-the-art N-body simulations performed with GENGA in a comparative study regarding the basic properties that emerge during the late stages of the terrestrial
planet formation process. We show that in modern N-body simulations the commonly used acceleration factor f, used to speed up the collisional growth of
planets in simulations, should be avoided since it can lead to distorted chemical composition of the
planets. We make a detailed comparison of low to high-resolution simulations, showing that the formation time scale depends on the size of the initial planetesimals. These simulations also show that terrestrial
planets can form resonant chains without the need of orbital migration due to gas effects.
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Instrumentation and Methods for Astrophysics
Fast and Scalable Production of Stacked Prism X-ray Lenses for Astrophysics Using Two-Photon Polymerization
Filip af Malmborg, Chloé Delmotte, Kian Shaker et al. (+1 more)
Stacked prism lenses (SPLs) are a type of refractive X-ray optics currently under development with the potential to greatly improve on current X-ray
telescope optics in terms of focal length, angular resolution, efficiency and scalability. For this work, SPLs are manufactured using two-
photon polymerization (2PP), with production being significantly faster and with higher
geometric fidelity than previous methods. Preliminary laboratory tests show improved efficiency compared to previous manufacturing methods and promising optical capabilities. Two-
photon polymerization is shown to be a reliable method for producing SPLs, and when challenges around printing time and assembly are addressed, the path towards an SPL X-ray
telescope lies open.
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All authors Filip af Malmborg, Chloé Delmotte, Kian Shaker, Mark Pearce
Astrophysics of Galaxies
The Cliff: A Metal-Poor Little Red Dot Hosting an Overmassive Black Hole at $z = 3.55$
Lucy R. Ivey, Francesco D'Eugenio, Roberto Maiolino et al. (+18 more)
JWST has revealed a large population of massive black holes (BHs) in the early Universe with unusual properties which mark them as distinct from low-
redshift active
galactic nuclei. Such findings have prompted the development of new models of BH formation and growth, and of their co-
evolution with host
galaxies. Linking the gas-phase
metallicity of BH environments to seed masses is key to understanding which evolutionary pathways could explain the population of JWST-discovered BHs. We present new high-resolution JWST NIRSpec/IFU observations covering the rest-frame optical emission lines of a Little Red Dot (LRD) at $z=3.55$, known as The Cliff, from the `Red Unknowns: Bright Infrared Extragalactic Survey' (RUBIES). We find evidence for low
metallicity ($Z=0.017\pm0.004 \ Z_\odot$) based on the low narrow-line [OIII]$\lambda5007$/H$\beta$ ratio, supported by the non-detection of low-ionisation emission lines such as [OII]$\lambda\lambda3727,3729$ and [NII]$\lambda\lambda6548,6583$. We find that the observed properties of The Cliff, including its overmassive BH, can be reproduced by some simulations of black hole growth and
evolution down to $z\sim3.5$. However, these simulation runs require high seed masses ($10^4 - 10^5\ M_\odot$) and appear as rarely in the simulation volume as in the RUBIES survey volume over
redshifts $3<z<4$, highlighting the unusual nature of The Cliff. Future simulations and numerical models will help to uncover how such a metal poor system managed to develop a massive black hole and persist to such low
redshift.
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All authors Lucy R. Ivey, Francesco D'Eugenio, Roberto Maiolino, Yuki Isobe, Ignas Juodžbalis, Sophie Koudmani, Michele Perna, Saiyang Zhang, Volker Bromm, Andrew J. Bunker, Stefano Carniani, Andrew C. Fabian, Kohei Inayoshi, Xihan Ji, Gareth C. Jones, Boyuan Liu, Robert Pascalau, Pierluigi Rinaldi, Brant Robertson, Jan Scholtz, Sandro Tacchella
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Covariant scalar-tensor theories beyond second derivatives
Mohammad Ali Gorji, Pavel Petrov and Karim Noui
We propose a covariant, gauge-independent construction of foliation-based scalar-tensor theories, yielding diffeomorphism-invariant operators involving only gradients on the hypersurfaces where the scalar field is constant, assumed to be spacelike. This defines a basis of independent invariants up to four derivatives of $\phi$, including the first nontrivial parity-odd pseudoscalar at this order, with a straightforward extension to higher derivatives. Our framework goes beyond degenerate higher-order scalar-tensor (DHOST) theories and provides a nonlinear extension of U-DHOST (where $\nabla_\mu\phi$ is supposed to be timelike) directly in covariant form, without using
unitary gauge as a starting point or imposing degeneracy a priori. After minimal coupling to
gravity, we analyze the theory through its
Hamiltonian constraint structure and linear cosmological perturbations about an FLRW background, and show that it propagates three physical degrees of freedom.
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Astrophysics of Galaxies
Joining forces: 30 years of optical monitoring of the Einstein Cross
V. N. Shalyapin, L. J. Goicoechea, R. Gil-Merino et al. (+5 more)
We present an extended optical monitoring of the quadruply-imaged gravitationally lensed
quasar QSO 2237+0305, the Einstein Cross, including observations from different observatories in both hemispheres and using a new photometric technique. This technique uses a region far enough from the lens system to determine accurately the sky background level, and minimises contamination from the
lensing galaxy by combining analytical and numerical modeling of its structure. The resulting light curves of the four
quasar images describe variations across practically the entire optical spectrum and span about 9000 days in the $VRI$ bands. The multi-band microlensing variability is captured with an unprecedented level of detail, and a preliminary microlensing analysis reveals an almost linear scaling of source radius with wavelength, providing direct evidence for the wavelength-dependent structure of the region contributing to optical passband fluxes. Specifically, assuming a mean microlens mass $\langle M \rangle$ = 0.3 $\rm{M_{\odot}}$ and concentric Gaussian sources that move according to the velocity distribution peaks (speed and direction) reported in a previous microlensing analysis, we find that the half-light radius of the $g$-band source is 9.6 $\pm$ 2.7 lt-day and the size of the sources grows with wavelength with a power-law index of $\alpha$ = 0.94 $\pm$ 0.05. We conclude that these long-term light curves set stringent empirical constraints on models of
quasar emission and microlensing physics.
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All authors V. N. Shalyapin, L. J. Goicoechea, R. Gil-Merino, A. Esteban-Gutiérrez, C. W. Morgan, E. Mediavilla, A. Yonehara, A. Sergeyev