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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 31 July

High Energy Astrophysical Phenomena

Joint X-ray and gamma-ray analysis at the photon level: Application to MSH 15-52

Katharina Egg and Alison M. W. Mitchell

Joint analysis of multi-wavelength (MWL) data at the level of photon events is challenging, but it provides a statistically preferable method of fitting the data, in contrast to fitting derived flux points. Data from X-ray and gamma-ray instruments are well-suited for a joint description, due to their common physical origin (same particle population and non-thermal processes) and incidentally also due to the high similarity of their formats. Such a description is especially desirable for objects such as pulsar wind nebulae (PWNe), diffuse sources that originate from outflows of particles that have been accelerated by pulsars. Photon emission is generated by particle interactions with the surrounding magnetic and radiation fields. The rich MWL emission from PWNe renders MWL studies essential to obtain a comprehensive picture of their physical properties. We demonstrate a joint MWL analysis of 3D X-ray and gamma-ray data at the photon event level by importing eROSITA X-ray data into the Gammapy software framework. We present our pipeline for converting eROSITA 3D (two spatial and one spectral dimension) event data into a Gammapy-readable format. We validated the approach through comparison with standard X-ray data products and analysis. Furthermore a 3D eROSITA data analysis as well as a joint fit with 3D H.E.S.S. data and Fermi 4FGL catalogue flux points was performed. We show through the analysis of data from the PWN MSH\,15-52 that 1D fits of Gammapy-extracted eROSITA spectra agree with the results of the native X-ray tool PyXspec. We demonstrate that 3D analyses on X-ray data can be conducted, with both background subtraction and background modelling. Furthermore, we show that joint analyses at event level between 3D X-ray and gamma-ray data can be conducted in Gammapy. This opens up exciting new possibilities for joint analyses of PWNe and other objects.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Dark Photon Dark Matter from Quantum Fluctuations during Starobinsky Inflation

Taiyo Kasamaki and Takeo Moroi

We present a detailed investigation of scenarios in which dark-photon dark matter is produced from quantum fluctuations during inflation. In particular, we focus on inflationary models that necessarily involve a Weyl transformation, dependent on the inflaton amplitude, in order to move to the Einstein frame. In such models, the kinetic function of the longitudinal mode of the dark photon varies throughout, and even after, the inflationary period. We show that this variation of the kinetic function has a substantial impact on the resulting relic abundance of dark photons. As a representative and phenomenologically important example, we analyze the Starobinsky inflation model, for which we perform an accurate computation of the relic dark-photon abundance. By imposing the relevant observational constraints, we find that, in order to reproduce the observed dark-matter density in the present Universe, the dark-photon mass must lie in the range $5.6 < m < 7.4\,\mu\mathrm{eV}$ within the framework considered in this work.
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Earth and Planetary Astrophysics

Tidal dissipation in magnetised, rotating stars and planets: linear calculations exploring various magnetic field configurations

Shijun Chu, Zhao Guo, Aurélie Astoul et al. (+2 more)

We study tidal flows in the convective envelopes of rotating, magnetised fluid bodies, such as low-mass stars and giant planets. In well-mixed convective regions, (magneto-)inertial waves are linearly excited by tidal forcing, and their dissipation can dominantly drive spin and orbital evolution in many close star-planet and binary star systems. We perform linear magnetohydrodynamic calculations of wavelike tides in spherical-shell geometry of a tidally-forced, rotating, incompressible, viscous and non-ideal magnetised fluid. Our calculations consider the widest range of magnetic field configurations to date (including both aligned and misaligned dipole fields, free-decay dipole and quadrupole fields, azimuthal "Malkus fields" and mixed poloidal-toroidal "Prendergast fields") to analyse the effects of magnetic fields on the wavelike response and dissipation. We find that the tidal response at a given frequency depends strongly on both magnetic field strength and geometry. Magnetic fields with strong poloidal components modify the flow more efficiently and introduce high-frequency Alfvénic resonances associated with weakly damped eigenmodes. When an enhanced (turbulent) viscosity is adopted, we find that viscous dissipation remains comparable to Ohmic dissipation for strong fields, in contrast to previous studies in which Ohmic dissipation was argued to dominate. We also explore the variation in magnetic effects as the shell thickness, magnetic Prandtl and Ekman numbers are varied. Finally, the frequency-averaged tidal power is found to be largely insensitive to the magnetic field in most cases, though significant deviations are found for free-decay fields. Our results have important implications for the tidal evolution of magnetised, rotating stars and planets.
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All authors Shijun Chu, Zhao Guo, Aurélie Astoul, Adrian J. Barker, Rainer Hollerbach

Cosmology and Nongalactic Astrophysics

Cosmological constraining power of the redshifts, heights, and angular clustering of weak gravitational lensing peaks

Jeger C. Broxterman, Matthieu Schaller, Ian G. McCarthy et al. (+8 more)

Weak gravitational lensing (WL) peaks probe non-Gaussian information of the large-scale distribution of matter that is not captured by two-point lensing statistics. We study the cosmological potential of the height distribution, redshift distribution, and angular clustering of high-valued WL peaks using a Bayesian inference approach that mimics a $\textit{Euclid}$ analysis. We use a forthcoming dark-matter-only hypercube, which varies cosmology in a ten-dimensional space, including evolving dark energy, neutrino mass, decaying dark matter, and the running of the scalar spectral index. We find the individual WL peak statistics to be complementary, as the redshift distribution best constrains the matter density, $\Omega_\mathrm{m}$, and the dark energy equation-of-state parameters, $w_0$, and $w_a$; the height distribution and angular clustering are most sensitive to the amplitude of the primordial power spectrum, $\ln(10^{10}A_\mathrm{s})$; while combining the three statistics allows us to also probe the baryon density, $\Omega_\mathrm{b}$, and the Hubble parameter, $h$. A comparison to the shear two-point correlation function demonstrates that WL peaks alone outperform the commonly used statistics, while even tighter constraints are obtained when combining all. Considering the 2-dimensional $\Omega_\mathrm{m}-\ln(10^{10}A_\mathrm{s})$ and $w_0-w_a$ parameter planes, we find that the redshift distribution outperforms the angular clustering and peak-height distributions. We study the impact of the smoothing scale and find that, typically, the smallest scales yield the best results and the figure of merit improves by a factor $\approx2$ when combining multiple scales.
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All authors Jeger C. Broxterman, Matthieu Schaller, Ian G. McCarthy, Willem Elbers, John Helly, Henk Hoekstra, Konrad Kuijken, Jaime Salcido, Joop Schaye, Naomi Schutte, Elena Sellentin

High Energy Astrophysical Phenomena

Polar cap plasma loading and the morphology of pulsar $\gamma$-ray light curves

Jérôme Pétri

The discovery of more than 300 $\gamma$-ray pulsars by the Fermi Large Area Telescope (Fermi-LAT) has revealed a rich diversity of light-curve morphologies that remains challenging to reproduce within purely magnetospheric emission models, suggesting that particle acceleration and radiation may occur, at least in part, in the striped-wind current sheet. We compute a comprehensive atlas of pulsar $\gamma$-ray light curves based on the split-monopole current sheet geometry, with the goal of quantifying the role of pair plasma loading in shaping the observed pulse morphology. The current-sheet surface is described analytically and assumed to be the dominant site of high-energy photon emission. Spatially dependent emissivity prescriptions are introduced through a minimal set of parameters that explicitly break the north-south and azimuthal symmetries of the emitting plasma. With only a few physically motivated parameters, the model is able to reproduce a broad range of the observed $\gamma$-ray light-curve morphologies, including asymmetric, multi-peaked, and highly structured profiles. The results show that asymmetric emissivity, possibly related to pair-plasma loading, provides a natural and economical mechanism capable of reproducing a substantial fraction of the observed diversity of $\gamma$-ray pulse profiles. The current-sheet scenario therefore appears to provide a promising and physically motivated framework for high-energy pulsar emission.
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High Energy Astrophysical Phenomena

Optical Images of the Braneworld Black Hole Surrounded by an Optically Thin Accretion Disk

Wen-Hao Deng, Sen Guo, Qing-Quan Jiang et al. (+2 more)

This work examines the observational signatures of rotating black holes with tidal charge in the Randall–Sundrum braneworld scenario. Combining an elliptic-integral-based analytical treatment with numerical ray tracing, we characterize photon motion around braneworld black holes in detail. For small observer inclinations, secondary images remain embedded inside the primary emission rings. As the inclination becomes larger, the primary and secondary images gradually separate and produce a strongly asymmetric image morphology. We show that the image asymmetry and the deformation of the inner shadow are jointly controlled by the black hole spin, the tidal charge, and the observer inclination. To analyze the frequency shifts across the accretion disk, we extend the emitting region from the ISCO down to the event horizon by including the plunging flow. The results indicate that the observer inclination is the dominant factor governing the frequency-shift distribution. In addition, we reconstruct braneworld black hole images using a fisheye-lens ray-tracing model. The optical morphology and brightness distribution show a clear dependence on the observing frequency, especially when comparing 230~GHz with 86~GHz. We also contrast the brightness distributions of prograde and retrograde disks, finding that both the total intensity and the peak intensity at 86~GHz are higher than those at 230~GHz. For negative values of the tidal charge, we further investigate the corresponding frequency-shift behavior and 230~GHz intensity profiles, which may provide useful theoretical guidance for future studies of extra-dimensional gravity models.
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All authors Wen-Hao Deng, Sen Guo, Qing-Quan Jiang, Kai Lin, Pei Wang

Instrumentation and Methods for Astrophysics

HARMONI at ELT: Developing a Modular Review Process using TRIZ

Amelia Calderhead, Anna MacIver, David Isherwood et al. (+2 more)

HARMONI is the first light, adaptive optics assisted, near-IR integral field spectrograph for the ELT. It covers a spectral range from 800nm to 2450nm with resolving powers from 3000 to 7000 and spatial sampling of 25mas and 6mas. It can operate in two adaptive optics modes - SCAO (including a high contrast capability) and MCAO. The project is resuming its final design phase after a rescope design phase in 2025. The HARMONI team at UKATC have been pioneering the use of TRIZ by managing monthly TRIZ workshops to tackle significant project problems that arise. This TRIZ case study investigates how design changes of HARMONI can be reviewed effectively and efficiently. It draws on how the review process of Ground Based Astronomy projects can be improved to add quality to the successful creation of an instrument while reducing strain on designers and reviewer's time. To address resource-intensive and document-driven review processes, the case study utilised TRIZ techniques including: thinking in time and scale technique: the 40 inventive principles to tackle design contradiction: function analysis and size, time, cost analysis. The solution developed considered a modular, continuous review process focusing on specific subsystems or technical topics as they mature while encouraging a live review culture, where stakeholders and expert reviewers are engaged continuously through informal check-ins rather than infrequent formal meetings.
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All authors Amelia Calderhead, Anna MacIver, David Isherwood, Andy Born, James Stevenson

Cosmology and Nongalactic Astrophysics

Direct shear $\times$ kSZ correlation: controlling baryons without modeling galaxies

Anoma Ganguly, Emmanuel Schaan, Elisabeth Krause et al. (+1 more)

Baryonic feedback redistributes gas within and around dark matter haloes, suppressing the small-scale matter power spectrum at a level that is now the leading systematic for upcoming weak-lensing surveys. The kinetic Sunyaev-Zeldovich (kSZ) effect directly probes this redistributed gas, but existing measurements around galaxies are either tied to the properties of the chosen galaxy sample or are susceptible to biases from other extragalactic foregrounds. We address both by cross-correlating a kSZ template constructed from the tomographic weak-lensing convergence maps and the radial velocity maps reconstructed from galaxy surveys via the continuity equation, with the observed CMB temperature. We forecast the detectability for Rubin LSST Y10 and Roman kinematic lensing samples combined with ACT, SO, and CMB-HD, finding signal-to-noise ratios of $\sim$ 5-15 for current and upcoming CMB data and $\gtrsim 100$ for CMB-HD, corresponding to few-per-cent and sub-per-cent constraints, respectively, on the baryonic suppression of the matter power spectrum. This method should thus achieve sufficient statistical precision to model baryonic feedback effects for Rubin, without the systematic challenge of modeling any galaxy-matter connection.
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All authors Anoma Ganguly, Emmanuel Schaan, Elisabeth Krause, Tim Eifler

Astrophysics of Galaxies

Reincarnations of massive stars in active galactic nucleus discs

Jing-Tong Xing, Tong Liu and Jiao-Zhen She

The origin and evolution of massive stars in active galactic nucleus (AGN) discs remain uncertain. We develop a semi-analytical model that follows the evolution of an embedded core-collapse supernova (CCSN) remnant and the subsequent formation and growth of a compact gas cloud. In the dense disc environment, efficient radiative cooling can strongly compress or bypass the Sedov-Taylor stage and drive the remnant rapidly into radiative snowplow evolution. After the remnant loses its interior pressure support, partial backflow of cooled shell fragments and refilling gas may initialize a pressure-confined and tidally limited seed cloud. The cloud then grows through shear-limited Hill capture until the gravitational, tidal, shear, photoionization, and magnetic conditions for collapse are simultaneously satisfied. The outcome depends strongly on the supermassive black-hole (SMBH) mass and explosion radius. Models with the lowest SMBH mass yield fewer than one massive star per event on average, whereas the most massive SMBH models can produce from several to several hundred. For a top-heavy initial mass function, massive stars dominate the resulting stellar mass and feedback budget. Embedded supernovae may therefore provide a localized gas-recycling channel for second-generation massive-star formation in AGN discs.
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Earth and Planetary Astrophysics

A Physically Driven Parameterisation of Multidimensional Atmospheres: Application to the JWST Phase Curve of WASP-121b

Yuanheng Yang, Guo Chen, Xianyu Tan et al. (+6 more)

Understanding the multidimensional structure of strongly irradiated exoplanets is essential for interpreting their atmospheric dynamics, chemistry and energy transport, yet current analyses remain limited by the difficulty of extracting reliable phase-resolved spectra and by the lack of physically interpretable parameterisations for retrievals. We combine a data-driven eclipse-normalisation method with an analytical three-dimensional temperature parameterisation derived from radiative, advective and diffusive energy balance and controlled by a few characteristic timescales. Applied to JWST/NIRSpec G395H observations of WASP-121b, the method yields spectra consistent with conventional phase-curve fitting, while the parameterisation reproduces the large-scale thermal structures predicted by general circulation models. The preferred retrieval reveals a pronounced day–night contrast, a dayside thermal inversion extending to both limbs, an inversion over part of the nightside, and limb temperatures differing by several hundred kelvin. Dynamical transport strengthens with pressure, and the hotspot offset increases from $\sim4^\circ$ to $\sim9^\circ$ across the pressures probed by G395H. The confined dayside hot region and the small, pressure-dependent offsets lie closer to the $\sim$3~G GCM than to its non-magnetic counterpart, although Rayleigh drag cannot be excluded. The spectra also favour distinct dayside and nightside chemical states, with more nightside CH$_4$ than the cooler temperatures alone can explain, pointing to disequilibrium chemistry. The retrieved thermal structure further implies an inhomogeneous cloud distribution, with condensation favoured on the nightside and cooler morning limb. The framework provides a computationally efficient, physically interpretable path from spectroscopic phase curves to multidimensional atmospheric structure.
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All authors Yuanheng Yang, Guo Chen, Xianyu Tan, Thaddeus D. Komacek, Xi Zhang, Thomas M. Evans-Soma, Fei Yan, Chengzi Jiang, Fei Dai

Astrophysics of Galaxies

The Open Cluster Chemical Abundances and Mapping Survey XI. First Gradients from SDSS/MWM BOSS Determined Clusters

Jonah M. Otto, Peter M. Frinchaboy, John Donor et al. (+13 more)

The Milky Way Mapper program in the fifth generation of the Sloan Digital Sky Survey (SDSS-V/MWM) has observed millions of stars, thousands of them in open clusters. The Open Cluster Chemical Abundances and Mapping (OCCAM) survey continues to create comprehensive datasets of open clusters and their members in order to constrain Galactic parameters. This eleventh contribution from the OCCAM survey is the first to use stellar parameters from stars observed with the optical Baryon Oscillation Spectroscopic Survey (BOSS) spectrograph to determine cluster membership. We use data from SDSS-V/MWM's 20th Data Release (DR20) and curate a sample of 1883 stars in 111 open clusters, including 95 not in previous OCCAM samples based on infrared data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectrograph. The sample includes 16 clusters with stars observed using both the BOSS and APOGEE spectrographs, and we find consistent agreement in measurements of both [Fe/H] and [$\alpha/M$]. The BOSS sample includes the majority of the clusters at young ages (Age $< 150$ Myr) that complement the APOGEE sample of primarily older clusters. We use the combined BOSS+APOGEE OCCAM sample to constrain the radial metallicity gradient with respect to $R_{guide}$ ($-0.079 \pm 0.005 \text{ dex kpc}^{-1}$) and $R_{gc}$ ($-0.082 \pm 0.006 \text{ dex kpc}^{-1}$), which agree well with results from previous OCCAM papers using only APOGEE data. Finally, the inclusion of the primarily young BOSS clusters has not changed that the OCCAM open cluster sample indicates no significant evolution of this gradient in different mono-age populations.
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All authors Jonah M. Otto, Peter M. Frinchaboy, John Donor, Ilija Medan, Natalie R. Myers, Audrey Hauck, Katia Cunha, Gail Zasowski, Madeleine McKenzie, Jingkun Zhao, Jose Eduardo Mendez-Delgado, Amaya Sinha, Zachary Way, Dmitry Bizyaev, Andrew R. Casey, Jose G. Fernandez-Trincado

Cosmology and Nongalactic Astrophysics

Gravitational waves from oscillons in a generalized exponential plateau potential

Peter Lott and Tuan Q. Do

We study oscillon formation and gravitational wave production in a generalized exponential plateau inflationary potential. Using Floquet analysis, we identify parametric instability bands consistent with oscillon formation, and solve numerically for the oscillon profile, finding quasi-breather solutions with lifetimes $\tau_{\rm osc} \cdot m_{\rm eff} \sim 10^3$ — $6\times10^4$. Applying the poltergeist mechanism, we compute the induced gravitational wave spectrum and find a peak at $f_{\rm peak} \approx 2.5\times10^{10}$~Hz with amplitude $\Omega_{\rm GW,0}\,h^2 \sim 10^{-9}$–$10^{-8}$ for the benchmark parameter $\beta_{\rm pot} = 5\times10^{-6}$. This is far below the region forbidden by big bang nucleosynthesis. For $\beta_{\rm pot} = 5\times10^{-5}$ the signal exceeds the big bang nucleosynthesis bound for all considered oscillon energy fractions, constraining the parameter space of the model. The signal falls in the GHz regime, potentially accessible to future resonant cavity experiments.
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Earth and Planetary Astrophysics

Asymmetric, variable H$\alpha$ line profile in planetary mass object SR 12 c

Jun Hashimoto, Yuhiko Aoyama, Michihiro Takami et al. (+1 more)

Young, forming planetary-mass objects often exhibit clear signatures of ongoing mass accretion and are thought to accrete material through processes analogous to those operating in young stars. In this study, we present high-spectral-resolution observations of asymmetric and time-variable H$\alpha$ line profiles from the planetary-mass companion SR~12~c. The H$\alpha$ line was observed at a resolving power of $R \sim 49,000$–40{,}000 (corresponding to 6.1–7.5~km~s$^{-1}$) using the High Dispersion Spectrograph (HDS) on the 8.2 m Subaru Telescope. Strong H$\alpha$ emission is clearly detected, while higher-order Balmer lines (H$\beta$, H$\gamma$, and H$\delta$) are not detected due to their faintness. The H$\alpha$ line profiles are well spectrally resolved and exhibit blueshifted emission peaks, which can be interpreted as arising from either (a) emission partially absorbed by redshifted accreting material along the line of sight and/or (b) geometric occultation by the inner circumplanetary disk. Moreover, the H$\alpha$ flux shows significant variability at 43.6~$\pm$~6.4~% relative to the peak flux on hourly timescales. During a continuous 2.5-hour observing sequence, the emission component peaking at approximately $-30$~km~s$^{-1}$ weakened over the first hour. Subsequently, an emission component centered near $-10$~km~s$^{-1}$ became dominant and remained stable for the remaining 1.5 hours. We discuss possible interpretations of this behavior. Overall, these results support that magnetospheric accretion is operating in the planetary-mass object SR~12~c while a scenario combining boundary-layer accretion with a failed wind cannot be ruled out.
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All authors Jun Hashimoto, Yuhiko Aoyama, Michihiro Takami, Shinsuke Takasao

Solar and Stellar Astrophysics

A New Approach to Modeling Line Shapes with Quasi-H$_2^+$ Satellites in Stellar Atmospheres

Jackson R. White, Thomas A. Gomez, Mark C. Zammit et al. (+6 more)

Theoretical spectral line shapes describe the distribution of opacity due to bound electronic transitions in hot dense plasmas and are used to fit emergent spectra from many astrophysical sources. Deficiencies in line broadening theory have been proposed as a possible explanation for unresolved discrepancies between theoretical and observed spectra in white dwarf star atmospheres and laboratory experiments at white dwarf star photosphere conditions. One possible source of these discrepancies is the formation of quasi-molecules. Quasi-molecules are close (unbound) collisions between atoms, which broaden line shapes and create additional satellite lines. Quasi-molecules are challenging to implement into traditional line shape codes and have historically required a number of physical approximations beyond what is used in standard Stark broadening models. Here we present a new approach to calculating line shapes with quasi-molecular resonances, using a novel multiple-basis method that considers both atomic and molecular states. We implement this approach into a simulation line shape code, present hydrogen Lyman-series line shapes with quasi-H$_2^+$ resonances, and demonstrate the impact our new line shapes have on hydrogen-atmosphere white dwarf star model spectra. We find that our new approach leads to broader quasi-molecular features that agree well with observed spectra in initial comparisons.
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All authors Jackson R. White, Thomas A. Gomez, Mark C. Zammit, Michael H. Montgomery, Bart H. Dunlap, Ivan Hubeny, Dmitry V. Fursa, Igor Bray, Don E. Winget

High Energy Astrophysical Phenomena

Strongly Magnetized Super-Eddington Accretion: How Spin and Accretion Rate Regulate Energy Output and Mass Loss

Tom Man Kwan, Lixin Dai, Cheuk Kwan Kan et al. (+5 more)

Strongly magnetized super-Eddington accretion flows power many important astrophysical systems, but how black hole parameters control their output is unclear. We present 32 general relativistic radiation magnetohydrodynamics simulations of super-Eddington magnetically arrested disks onto stellar-mass black holes, varying mass ($M_{\rm BH}= 5, 15, 30\,M_{\odot}$), spin ($a=0,0.9$), and accretion rate ($\dot{M}_{\rm acc} \approx 1-2000\,\dot{M}_{\rm Edd}$). We find that black hole spin and accretion rate jointly regulate wind loss rates and energy output efficiencies, while black hole mass has no effect over the mass range studied here. The BH accretes only $10-40\%$ of the mass supplied to the accretion flow, while the rest is expelled in winds. This accretion fraction decreases with mass supply rate and is lower for high-spin systems. Both spin states produce strong magnetically driven outflows. For $a = 0$, the wind kinetic, radiative, and electromagnetic efficiencies are modest and show little variation across the full simulated range of accretion rates. For $a = 0.9$, both wind power and jet power increase super-linearly with $\dot{M}_{\rm acc}$, with the jet power saturating beyond $\dot{M}_{\rm acc} \sim 100\,\dot{M}_{\rm Edd}$. Radiation is strongly beamed along the funnel, with inverse beaming factors exceeding $100$ for high-spin, high-$\dot{m}$ models viewed face-on. Our results establish that rapid BH spin boosts energy-extraction efficiency, while high accretion rate amplifies total power. We provide scaling relations for luminosities, jet power, accretion ratio, and beaming, offering a framework for interpreting observations of ULXs and other super-Eddington systems.
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All authors Tom Man Kwan, Lixin Dai, Cheuk Kwan Kan, Zepei Xing, Tassos Fragos, Matthew Middleton, Tao Ji, Feng Yuan

Cosmology and Nongalactic Astrophysics

A Sequentially-Valid Reanalysis of DESI's Dynamical Dark Energy Signal

Jinyoung Kim, David F. Mota and Andrius Tamosiunas

Surveys such as DESI release data in stages, and each release invites a fresh assessment of whether dark energy is consistent with a cosmological constant. Standard Wilks-based $\sigma$ values are interpreted as if the test were performed only once, yet revisiting the same question at DR1, DR2, DR3, and beyond inflates the chance of an apparently significant fluctuation. We reanalyse the DESI BAO evidence for dynamical dark energy using an e-process, a likelihood-ratio-based measure of evidence that remains valid under repeated looks at accumulating data: it controls the false-detection probability under continued testing across releases with no trials-factor penalty. Applied to the DESI DR1$\to$DR2 BAO sequence, the result depends strongly on which departures from $\Lambda$CDM the test is designed to detect. For a pre-specified alternative aligned with the DR2-preferred direction, the running evidence reaches $M_{DR2} = 33.97$, crossing an illustrative 5% threshold of 20. The evidence is concentrated almost entirely in the LRG2 redshift bin, and removing that bin reduces the running e-value to $M = 0.49$, mildly favouring $\Lambda$CDM. When allowing any of the seven bins to have produced the excess, the signal does not survive a look-elsewhere correction. Other physically agnostic alternatives also fail to reject $\Lambda$CDM, while a physically motivated thawing-quintessence alternative rejects more strongly than any agnostic choice. The concentration of evidence in LRG2 specifically is difficult to reconcile with a smoothly evolving equation of state. The data therefore points to a fragile, single-bin, specification-dependent signal rather than robust evidence for dynamical dark energy. We recommend that future DESI, Euclid, Roman, and LSST data releases report an anytime-valid e-process value with its test specification stated alongside conventional $\sigma$ significances.
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Instrumentation and Methods for Astrophysics

On-sky results from REDWOODS, a platform at Lick/ShaneAO for testing second stage AO technologies

Benjamin L. Gerard, Dominic F. Sanchez, Aditya R. Sengupta et al. (+11 more)

REDWOODS is a new sub-testbed within the Shane Adaptive Optics (AO) system at Lick observatory, developed to test second stage AO wavefront sensing and control technologies, including a Self-Coherent Camera with optional broadband Wynne corrector, two different three-sided fully reflective highly broadband pyramid wavefront sensor modes, and multi-wavefront sensor single conjugate AO control. We present project results to date, including on-sky data.
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All authors Benjamin L. Gerard, Dominic F. Sanchez, Aditya R. Sengupta, Chris Ratliff, Sylvain Cetre, Elinor Gates, Daren Dillon, Bautista Fernandez, Brian Bauman, Lisa Poyneer, Aaron Lemmer, Rebecca Jensen-Clem, Phillip Hinz, Bruce Macintosh

Thursday 30 July

Astrophysics of Galaxies

Broad Paschen lines as black hole mass tracers: A reverberation mapping calibration

Shengxiu Sun, Sarah E. I. Bosman, Frederick B. Davies et al. (+4 more)

Single-epoch (SE) black hole mass estimators based on rest-frame ultraviolet or optical broad lines can be limited by dust attenuation or wavelength coverage. We calibrate estimators based on broad Paschen P$\alpha$ and P$\beta$ directly against reverberation mapping (RM) masses. We obtained LBT/LUCI near-infrared spectra of 27 SDSS-RM quasars and combined them with archival Paschen measurements for AGNs with RM masses. After continuum subtraction, we measured line luminosities and full widths at half maximum (FWHMs) using multi-component and single-Gaussian profile models. We fitted $\log(M_{\rm BH}/M_\odot)=a+b\log(L/10^{41}\,{\rm erg\,s^{-1}})+c\log({\rm FWHM}/10^3\,{\rm km\,s^{-1}})$, including intrinsic scatter. The fiducial relations use photometrically corrected line luminosities and FWHMs of the combined broad profiles. For P$\alpha$, we obtain $(a,b,c)=(6.86^{+0.24}_{-0.25},0.47^{+0.11}_{-0.10},1.24^{+0.49}_{-0.48})$ with an intrinsic scatter of $0.28^{+0.08}_{-0.06}$ dex. For P$\beta$, we obtain $(7.00\pm0.24,0.48^{+0.10}_{-0.09},0.91^{+0.46}_{-0.47})$ with a scatter of $0.32^{+0.08}_{-0.06}$ dex. Relations using single-Gaussian widths, 5100 Å continuum luminosities, or fixed virial slopes have scatters consistent within the uncertainties. These relations provide complementary mass estimators when ultraviolet or optical broad lines are attenuated or unavailable. They should be applied within the parameter ranges of the calibration sample and remain subject to the systematic uncertainty associated with the RM virial factor.
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All authors Shengxiu Sun, Sarah E. I. Bosman, Frederick B. Davies, Klaudia Protušová, Benedetta Spina, Linhua Jiang, Danyang Jiang

High Energy Astrophysical Phenomena

Arcminute Microkelvin Imager observations at 15.5 GHz of the tidal disruption event Swift J164449.3+573451 from 2011 Mar to 2014 Mar

David A. Green

Radio monitoring of the tidal disruption event Swift J164449.3+573451 at 15.5 GHz with the Arcminute Microkelvin Imager is reported. The results from 308 observations made from 2011 Mar to 2014 Mar are presented. These show a steady rise in flux density from $\approx$3 mJy (three days after the initial $\gamma$-ray detection of Swift J164449.3+573451), to a peak of nearly 30 mJy $\approx$140 days later, followed by a steady decline.
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Instrumentation and Methods for Astrophysics

Cassiopee: Defining the next-generation deformable mirror and high-speed SWIR camera for adaptive optics applications

B. Neichel, T. Fusco, F. Oyarzun et al. (+14 more)

Future adaptive optics (AO) systems for astronomy, optical communications, space situational awareness, and laser-based defense require a new generation of components operating at unprecedented speed, sensitivity, and precision. We present a systematic approach to defining the specifications of two key technologies: a large-format, high-cadence SWIR camera and a high-order deformable mirror (DM). Starting from four representative use-cases, high-contrast exoplanet imaging, free-space optical communications, satellite observation, and laser focusing, we derive detailed AO error budgets to identify the dominant performance drivers. This analysis defines quantitative requirements for the DM (actuator count, stroke, bandwidth, electronics) and the camera (read noise, quantum efficiency, frame rate, latency, and dark current), developed in close collaboration with industrial partners. We then describe an integrated experimental testbed designed to validate both components in a closed AO loop under atmospheric and system-level disturbances representative of astronomical and telecom applications. Finally, we outline the roadmap toward on-sky validation with EKARUS, the new AO facility at Asiago Observatory, bridging the gap between component qualification and deployment in future extremely large telescopes and ground-to-space optical links.
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All authors B. Neichel, T. Fusco, F. Oyarzun, V. Chambouleyron, J.-F. Sauvage, C.-T. Héritier, J. Charton, C. Pravert, F. Clop, L. Maillet, M. Laslandes, J.-L. Gach, D. Boutolleau, P. Feautrier, P. Bruno, Y. Wanwanscappel, C. Bremond

Solar and Stellar Astrophysics

JW-FD: A 15-Year Multimodal Dataset for Solar Flare Forecasting

Shao Mingfu, Lin Jiaben, Wang Hui et al. (+4 more)

Solar flares drive severe space weather hazards, and forecasting their occurrence remains a central challenge for both heliophysics and operational space weather services. Data driven methods require long horizon datasets in which images, magnetic features, and flare labels are coregistered in space and time. We present JW-FD (JW-Flare Dataset), a 15 year multimodal release spanning 1~January~2011 through 31~December~2025, constructed from SDO/HMI line of sight magnetograms, NOAA Solar Region Summary reports, and NOAA X-ray flare event lists. The dataset comprises 3{,}064 independent active regions and 1{,}991{,}247 coregistered magnetogram crops, together with FITS, PNG, CSV, and MP4 modalities. Each sample provides 29 magnetic features linked to configurable flare labels under a strict pre-eruption window spanning seven forecast horizons and four GOES intensity thresholds. An 8:1:1 split at the active region level is adopted to prevent temporal leakage between partitions. PNG branches are released at six magnetic saturation thresholds, and internal Transformer experiments on $\geq$C1.0 forecasting suggest $B_{\mathrm{th}}=1000$~G as a preliminary default, although the optimal saturation is model and task dependent. The open source construction pipeline is available at https://github.com/Xiaoxuan-1/JW-FD.
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All authors Shao Mingfu, Lin Jiaben, Wang Hui, Tong Liyue, Yang Chen, Zhang Yin, Li Yuyang

High Energy Astrophysical Phenomena

Microscopic Interaction versus Purely Gravitational Coupling in Strange Quark Stars Admixed with Dark Matter: A One-Fluid and Two-Fluid Comparison

J. Sedaghat, G. H. Bordbar, M. Haghighat et al. (+1 more)

In this study, we investigate strange quark stars (SQSs) admixed with scalar dark matter (DM), focusing on the role of microscopic interactions versus purely gravitational coupling. Our results demonstrate that while the interacting one-fluid model yields viable configurations with M_TOV > 2M_sun that satisfy current pulsar M-R measurements alongside the tidal deformability (Lambda) constraints from GW170817, the noninteracting two-fluid model more robustly meets both existing GW170817 limits and the tighter Lambda bounds anticipated from next-generation gravitational-wave detectors.
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All authors J. Sedaghat, G. H. Bordbar, M. Haghighat, S. M. Zebarjad

Astrophysics of Galaxies

Determining Total Infrared Luminosities from Submm Measurements of High Redshift Galaxies

Maria Emilia De Rossi, George H. Rieke, Christina C. Williams et al. (+6 more)

Determining total infrared luminosities for very high redshift galaxies is important to estimate the rate of star formation in heavily dust-embedded environments. It is also challenging because the most sensitive far infrared observatory, Herschel, was limited in sensitivity and its deepest measurements are subject to confusion noise. Thus, these determinations largely depend on ALMA, observing in the mm- and/or submm-wavelengths, which sample only the long-wavelength part of the spectral energy distributions (SEDs). Luminosities are conventionally estimated with modified blackbody fits to these measurements, but do not include the emission in the mid-infrared by warmer dust; there is evidence that this mid-IR component may be relatively strong in very high-redshift galaxies compared with local ones. A correction factor must be applied to the modified black body luminosities to derive the total infrared luminosity. We study infrared SEDs using simulations tuned to galactic conditions typical of high-z galaxies. We find that the different behaviors of infrared SEDs are dominated by a single key physical parameter, the luminosity density. This allows us to estimate the corrections for the missing mid-infrared luminosity in a general way. We find that a factor of ~ 1.6 - 1.7 (0.2 dex) is appropriate in most circumstances, with a larger factor of ~ 1.75 - 1.85 (~ 0.25 dex) up to 2 (0.3 dex) necessary for high redshift (z > 4) galaxies at the highest luminosities, > 10^{12} Lsun. These corrections are needed to estimate star formation rates based on total infrared luminosity.
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All authors Maria Emilia De Rossi, George H. Rieke, Christina C. Williams, Volker Bromm, Jianwei Lyu, Meredith A. Stone, Yang Sun, Christopher N. A. Willmer, Yongda Zhu

Solar and Stellar Astrophysics

Quasi-Keplerian Be-Star Disks with Mimicking Viscosity

Michel Cure, Ignacio Araya, Rodrigo Meneses et al. (+5 more)

Classical Be stars are fast-rotating B-type stars with gaseous quasi-Keplerian disks formed by equatorial ejection of material. While the viscous decretion disk (VDD) model reproduces many observed properties, the role of radiative line driving in shaping these disks remains unclear. We investigated the combined influence of viscosity and radiative acceleration on the hydrodynamic structure of Be star disks by coupling the m-CAK theory of line-driven winds with a mimicking viscous prescription governed by the parameter $\gamma_{\rm vis}$. We solved the steady-state hydrodynamic equation of motion using Hydwind for typical B-type stellar parameters in transonic $\Omega$-slow outflows. We analyzed the velocity and density structures and derived the mass-loss rates and radial velocities at the adopted outer integration radius, $r=50\,R_\ast$. The combined action of line driving and viscosity yields regular m-CAK $\Omega$-slow solutions for equatorial outflow with a VDD-inspired rotational prescription. For quasi-Keplerian exponents ($\gamma_{\rm vis} \simeq 0.5$) and near-critical rotation ($\Omega \approx 0.96$–$0.99$), the models produce an outflowing disk with an m-CAK-type critical point at $r_{\rm c} \lesssim 20$–$30\,R_\ast$. At $50\,R_\ast$, these quasi-Keplerian solutions reach radial velocities of $76.9$–$139.2\,\mathrm{km\,s^{-1}}$. Within the present 1D parameterized framework, the m-CAK line force yields stationary solutions without imposing an outer boundary condition. Our results provide a controlled 1D test of how a VDD-inspired rotational prescription modifies the topology of stationary m-CAK $\Omega$-slow solutions. The model is an exploratory bridge toward future non-Sobolev multidimensional radiation-hydrodynamic treatments that recover quasi-Keplerian rotation and modest outflow velocities of Be disks.
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All authors Michel Cure, Ignacio Araya, Rodrigo Meneses, Matias Montesinos, Roberto O. J. Venero, Catalina Arcos, Abigali Rodriguez, Lydia S. Cidale

High Energy Astrophysical Phenomena

Energy-dependent Optical/Near-infrared and X-ray Correlations in Swift J1727.8-1613

Ruican Ma, Federico Vincentelli, Diego Altamirano et al. (+5 more)

We present a timing analysis of the black hole transient Swift J1727.8-1613 during its intermediate state. We use coordinated broadband X-ray observations from Insight-HXMT (2-150 keV), together with optical data from ULTRACAM (g_s and i_s bands) and near-infrared data from HAWK-I (K_s band), obtained on 2023 September 9. As shown by previous studies, the Fourier power spectrum shows a strong quasi-periodic oscillation (QPO) in the K_s, i_s and X-ray bands. Cross-correlation analysis reveals a complex coupling between the optical/near-infrared (OIR) and X-ray emission, including a delayed optical anti-correlation, a strong infrared correlation, and a pronounced dependence of these features on X-ray energy, suggesting multiple Comptonisation regions. In contrast, the lag properties do not change at the QPO frequency, displaying an OIR lag of ~60-80 ms up to 150 keV. We discuss these results in the context of small-scale jet and hot accretion flow scenarios.
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All authors Ruican Ma, Federico Vincentelli, Diego Altamirano, Alexandra Veledina, Poshak Gandhi, Piergiorgio Casella, Tariq Shahbaz, Sian Woahene-Demehin

Earth and Planetary Astrophysics

Optical and acoustic ground effects simulations from terminal defense asteroid disruption via the PI method

Brin Bailey, Alexander N. Cohen, Philip Lubin et al. (+5 more)

Our simulations suggest that PI ("Pulverize It"), a NASA Phase II NIAC study, is an effective multi-modal approach for planetary defense that can operate in extremely short interdiction modes (with intercepts as short as hours prior to atmospheric entry) as well as long interdiction time scales with months to years of warning. The basic process is complete disruption of the threat via fragmentation. In scenarios with sufficiently long warning time, the fragment cloud spreads enough to miss Earth, resulting in no ground effects. In "worst-case" scenarios, when the warning time is short, the fragments (typically <10 m in diameter) will enter Earth's atmosphere, where their energy is dissipated in a series of ground-level optical pulses and de-correlated shock waves, mitigating any significant damage. We investigate the optical and acoustic ground effects through a set of simulation codes that model the interaction of asteroid fragments with Earth's atmosphere following terminal threat interception. Even in short-warning time cases where fragments enter the atmosphere, our simulations suggest that threats mitigated by the PI method produce vastly less damage on the ground when compared to the same unfragmented case, yielding optical energy deposition below 200 kJ/m$^2$ and shock wave over-pressures under 3 kPa. Our simulations support the proposition that threats like 2023 PDC, the hypothetical 800 m diameter asteroid from the 2023 Planetary Defense Conference impact exercise, can be effectively mitigated through fragmentation. We find that a terminal defense mitigation scenario that disrupts 2023 PDC into 1 million fragments with an intercept of 60 days before ground impact results in minimal ground effects.
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All authors Brin Bailey, Alexander N. Cohen, Philip Lubin, Darrel K. Robertson, Mark Boslough, Sasha Egan, Elizabeth A. Silber, Dharv Patel

Astrophysics of Galaxies

EWOCS-VIII: Internal kinematics and expansion of Westerlund 1 from VVVX proper motions

C. Ordenes-Huanca, A. Bayo, M. Guarcello et al. (+12 more)

Westerlund 1 (Wd1) is the most massive young star cluster known in the Milky Way and a key laboratory for studying the early dynamical evolution of massive clusters. Owing to its high extinction, the internal kinematics of its intermediate-mass stellar population remain largely unexplored. We aim to characterize the internal kinematic properties of Wd1 using a homogeneous census of near-infrared (NIR) selected cluster members and their proper motions (PMs). We considered PMs from the VIRAC2 catalog, based on multi-epoch VVV/VVVX observations. For $1286$ candidate members previously identified through NIR photometry and astrometry (Paper I), we computed their PMs relative to the cluster mean motion and analyzed them as a function of position and radius. We also investigate radial trends, test the robustness of the results against the assumed cluster center, and search for preferred directions of motion. We detect a statistically significant signature of expansion in the outer regions of Wd1, with the radial component of the relative PMs increasing with distance from the cluster center. The expansion appears asymmetric, with the strongest gradient detected along a PA$=84\degree \pm 8\degree$ in the plane of the sky and with $5.9\sigma$ significance. We also find hints for inward radial motions in the central region, consistent with ongoing mass segregation, but only at $\approx 2\sigma$ significance. Taken together, these results are consistent with a nearly monolithic formation scenario.
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All authors C. Ordenes-Huanca, A. Bayo, M. Guarcello, M. Zoccali, A. Rojas-Arriagada, Nicholas J. Wright, S. Sciortino, F. Damiani, K. Muzic, V. Almendros-Abad, M. Andersen, R. Bonito, M. Haberle, T. J. Haworth, L. Prisinzano L. Prisinzano

Instrumentation and Methods for Astrophysics

LUVCam: A high-performance, low-cost, UV/optical camera for the future of astronomy in space

Aaron Tohuvavohu, Suresh Sivanandam, Jean-Christophe Fronteddu et al. (+23 more)

Astronomy-grade cameras with robust performance and heritage in the space environment have long been costly, substantially limiting capacity for space-based astronomy and creating a resource barrier to access. Additionally, ultraviolet observations have historically been limited by the low quantum efficiency of most sensors in this wavelength range. The LUVCam program is designed to address both issues by providing a high-performance, low-cost, UV/optical camera system sufficiently capable to support a wide-array of space-based astronomy missions. LUVCam features a large format, low-noise, large pixel, and high quantum efficiency, commercial-off-the-shelf back(front)-side illuminated CMOS sensor, packaged with custom built readout electronics, firmware, and thermomechanical structure to provide both superlative science capability and precision on-sensor guidance at fast cadence to allow for stable high-resolution imaging. LUVCam is ITAR-free and cheap to fabricate, opening up new opportunities for access to space telescopes. Here we introduce LUVCam, describe its performance characteristics, and the rapid implementation of a technology demonstration for flight. LUVCam, coupled with a small aperture custom-built UV telescope, has been on orbit since July 2024 and has achieved Technology Readiness Level (TRL) 7. LUVCam is manifested for several more near-term orbital missions, including a second technology demonstration CubeSat for launch in 2026, and will provide both focal plane cameras for QUVIK, a two-channel UV transient astronomy mission.
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All authors Aaron Tohuvavohu, Suresh Sivanandam, Jean-Christophe Fronteddu, Patrick Nkwaria, Gavin Hay, Shaojie Chen, Sarik Jeram, Albert Lau, Jacob Taylor, Mark Barnet, Andras Pal, Mohamed Shaaban, Ajay S. Gill, Julia Empey, Emma Seabrook, Coby Silayan, Dhwanil Patel, Braden Seefeldt-Gail, Phil R. Van-Lane, Scott Christie, Christopher D. Matzner, Chris Damaren, Maria Drout, Filip Munz, Jakub Řípa, Norbert Werner

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

Galactic cold clouds constraints on sub-GeV DM and asteroid-mass PBHs

Asier Salces Pérez and Pedro de la Torre Luque

We show that the ionization of molecular and atomic clouds provides a novel probe of dark matter scenarios producing low-energy $e^+e^-$ pairs through annihilation, decay, or Hawking evaporation of primordial black holes. We derive constraints on MeV-scale dark matter with masses between $\sim1$ and $100$ MeV, as well as on primordial black holes in the mass range $10^{14}$–$3\times10^{17}$g. By modeling the propagation of electrons and positrons inside these clouds, we show that uncertainties in charged-particle transport constitute the main limitation of this method. Nevertheless, for the most physically motivated propagation scenarios, the resulting constraints remain competitive with the strongest bounds currently available. We also identify the cloud properties that maximize the sensitivity to dark matter-induced ionization and discuss how larger samples of clouds, together with improved modeling of cosmic-ray ionization and cloud structure, could substantially enhance the reach of this technique. Our results establish molecular and atomic cloud ionization as a promising and complementary probe of sub-GeV dark matter and evaporating primordial black holes.
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Instrumentation and Methods for Astrophysics

Multi-sensor fusion for fine-guidance and milliarcsecond-level attitude estimation of balloon-borne telescope

Philippe Voyer, Maya Amit, Steven J. Benton et al. (+44 more)

Balloon-borne telescopes rely on fine-guidance systems to achieve milliarcsecond image stability despite residual disturbances from the balloon environment. In these systems, the Fast Steering Mirror (FSM) stabilizes the image in two focal-plane axes, but leaves systematic, field-dependent residual motion induced by boresight roll. This effect, referred to as roll leakage, becomes more important for wider fields of view. In this work, roll leakage is characterized using data from the 2023 Superpressure Balloon-borne Imaging Telescope (SuperBIT) science flight. SuperBIT is a 0.5-m near-ultraviolet to near-infrared telescope that demonstrated milliarcsecond-level image stability during its 45-night science flight. We find that passive focal-plane star-camera measurements correlate strongly with independent roll measurements across a large set of science exposures, showing that boresight roll frequently drives residual focal-plane motion. We then develop a simulation framework combining optical ray tracing, asynchronous guide-star measurements, estimation, and FSM control to study this behavior. The framework is used to compare single-star and multi-star guidance architectures under realistic flight disturbances. For the SuperBIT geometry, we find that multi-star estimation reduces average roll-induced science-field image motion by 31.8%, increasing to 77.4% for a representative geometry of GigaBIT, SuperBIT's planned larger-aperture successor. These results motivate further investigation of multi-star fine-guidance architectures for GigaBIT.
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All authors Philippe Voyer, Maya Amit, Steven J. Benton, Benjamin E. Boyd, Anthony M. Brown, Giulia Cerini, Paul Clark, Matthew Craigie, Christopher J. Damaren, Tim Eifler, Spencer W. Everett, Aurelien A. Fraisse, Leo W. H. Fung, Ajay S. Gill, Suren Gourapura, Eric Habjan, John W. Hartley, David Harvey, Bradley Holder, Eric M. Huff, Mathilde Jauzac, William C. Jones, David Lagattuta, Gavin Leroy, Jason S.-Y. Leung, Lun Li, Thuy Vy T. Luu, Richard Massey, Jacqueline E. McCleary, Adyn Miles, Johanna M. Nagy, C. Barth Netterfield, Emaad Paracha, Susan F. Redmond, Jason D. Rhodes, Andrew Robertson, L. Javier Romualdez, Sayan Saha, Jürgen Schmoll, Mohamed M. Shaaban, Ellen Sirks, Sut Ieng Tam, Simon Tartakovsky, Georgios N. Vassilakis, André Z. Vitorelli, Bryce Warren, Alfredo Zenteno