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Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 25 July

High Energy Astrophysical Phenomena

Diverse Morphologies of GRB X-Ray Plateaus within a Common Magnetar Framework

Xiao-Fei Dong, Yong-Feng Huang, Nurimangul Nurmamat et al. (+7 more)

The origin of the X-ray plateau phase in gamma-ray bursts (GRBs) remains an open problem. In particular, it is unclear whether GRBs with different temporal morphologies (i.e., with a rising, flat, or decaying plateau) arise from a common underlying mechanism. Although magnetar energy injection is a leading explanation, previous studies have primarily inferred magnetar properties on a burst-by-burst basis and have not tested the model at the population level. Here we perform the first hierarchical population inference of magnetar parameters for a uniform sample of 185 long GRBs with X-ray plateaus within a conditional Poisson point-process framework. It is found that the observed plateau population is well reproduced by physically plausible magnetar populations. The inferred parameter distributions show no strong statistical separation among subclasses with different plateau morphologies. Nevertheless, all subclasses show a substantial intrinsic luminosity scatter, $\sigma_{L,\rm int}\sim0.5$–1.0 dex, whereas the intrinsic duration scatter remains considerably smaller. The results provide a population-level test of the magnetar interpretation of GRB X-ray plateaus, showing that the observed diversity of plateau morphologies does not require distinct magnetar populations.
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All authors Xiao-Fei Dong, Yong-Feng Huang, Nurimangul Nurmamat, Chen Deng, Ze-Cheng Zou, Fan Xu, Abdusattar Kurban, Chen Du, Chen-Ran Hu, Jin-Jun Geng

High Energy Astrophysical Phenomena

Constraining cosmological parameters from very-high-energy $\gamma$-ray attenuation in blazar spectra: Bayesian inference and systematic uncertainties

Patryk Liniewicz and Emmanuel Moulin

Very-high-energy $\gamma$ rays from active galactic nuclei are attenuated through pair production on the extragalactic background light (EBL), providing a probe of cosmic expansion. We develop a Bayesian inference analysis framework that uses an observationally driven, redshift-dependent EBL model and anchors intrinsic source spectra to the Fermi-LAT 3FHL catalogue while marginalising spectral-shape departures and dataset normalisations. The method is validated on realistic mock observations and applied to 241 archival H.E.S.S., MAGIC and VERITAS spectra of 50 AGN compiled in STeVECat. Because the leading opacity depends on the ratio of the EBL normalisation to the reduced Hubble constant, the gamma-ray data primarily constrain this ratio rather than $H_0$ alone. We measure $r=1.723^{+0.096}_{-0.095}$. For a fixed EBL scale, this gives $H_0=58.3^{+3.4}_{-3.0},\mathrm{km,s^{-1},Mpc^{-1}}$; allowing an 18% EBL-scale uncertainty gives $H_0=60.5^{+10.8}_{-10.0},\mathrm{km,s^{-1},Mpc^{-1}}$. Matched injections recover the input opacity without appreciable bias, and the tested intrinsic-spectrum and EBL-shape perturbations are subdominant except for large infrared-background mismodelling. The predominantly low-redshift sample leaves $\Omega\mathrm{M}$ weakly constrained. The measurement is therefore limited by the EBL normalisation rather than statistics; reducing its uncertainty to a few per cent would make gamma-ray opacity a competitive, distance-ladder-independent probe of $H_0$.
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Instrumentation and Methods for Astrophysics

Output-Stage Design Optimization for High-Sensitivity SiSeRO CCDs and SiSeRO Active Pixel Sensors

Tanmoy Chattopadhyay, Sven Herrmann, Kevan Donlon et al. (+16 more)

The Single electron Sensitive Read Out (SiSeRO) technology is a new device class designed to support the needs of future X-ray and optical astronomical telescopes that will require fast, low-noise, megapixel spectro-imagers. Developed at MIT Lincoln Laboratory, in collaboration with Stanford University and MIT, the first generation SiSeRO-CCD (charge-coupled device) prototypes achieved a charge/current conversion gain of 700$-$800 pA per electron, an equivalent noise charge (ENC) of around 3.5 electrons root mean square (RMS), and a full width half maximum (FWHM) energy resolution of approximately 130 eV at 5.9 keV at a readout speed of 625 kpix/s. Utilizing Repetitive Non-Destructive Readout (RNDR), these same devices also demonstrated sub-electron noise performance (ENC$<$0.5 electrons RMS) at a readout speed of 10 kpix/s. We present the results of device simulations for next-generation SiSeRO CCD output stages that optimize the sensing transistor and its internal gate geometry to enhance noise and speed performance. Further, the goal is to develop a SiSeRO active pixel sensor (APS) that combines the proven X-ray performance of CCDs with the architectural advantages of an APS. Enabling this requires substantial design updates, for example, incorporating two SiSeRO amplifiers side by side on each pixel and shuffling the charge between them to support RNDR. We discuss our device simulation framework and design parameter optimization in the first-generation SiSeRO devices.
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All authors Tanmoy Chattopadhyay, Sven Herrmann, Kevan Donlon, Ilya Prigozhin, Peter Orel, Steven W. Allen, Marshall W. Bautz, Michael Cooper, Catherine E. Grant, Beverly LaMarr, Christopher Leitz, Eric D. Miller, R. Glenn Morris, Abigail Y. Pan, Tonya L. Peshel, Artem Poliszczuk, Gregory Prigozhin, Haley R. Stueber, Keith Warner

Astrophysics of Galaxies

HETDEX: Star Formation Stochasticity Diagram of Lyman Alpha Emitting Galaxies at Cosmic Noon Confirms Three Archetypes

Nicole Firestone, Eric Gawiser, Kartheik G. Iyer et al. (+14 more)

In this work, we aim to measure the star formation stochasticity of Lyman Alpha Emitting Galaxies (LAEs) at Cosmic Noon. We identify 270 LAEs from the HETDEX Survey in the COSMOS field with rest-UV-through-NIR photometry from CANDELS\null. For each LAE, we perform non-parametric gaussian-process star formation history (SFH) reconstruction using the Dense Basis method. Our HETDEX LAE sample is described well by the three SFH archetypes defined for ODIN LAEs in Firestone et al. 2025 with comparable frequency: First Burst, Dominant Burst, and Nondominant Burst. The rapidly rising Star Formation Rates (SFRs) of First Burst LAEs are not adequately represented in traditional SFR$_{100}-M_*$ diagrams, where SFR$_{100}$ is averaged over the most recent 100Myr. This motivates the usage of SFR$_{10}-M_*$, where SFR$_{10}$ is averaged over the most recent 10Myr. We introduce the Star Formation Stochasticity Diagram, a diagnostic tool that probes variations in galaxies' SFRs across cosmic time. By eliminating the confounding factor of redshift evolution, we are able to employ a gaussian mixture model to decompose our ratio of short- vs.long-term SFR into statistically motivated sub-populations. This agnostic component decomposition reveals three populations consistent with the empirical LAE SFH archetypes. We can, therefore, summarize the overall stellar mass assembly of LAEs with this ratio, even without viewing their full star formation histories.
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All authors Nicole Firestone, Eric Gawiser, Kartheik G. Iyer, Charlotte Olsen, Antara Basu-Zych, Adam Broussard, Peter Kurczynski, Kyoung-Soo Lee, Erin Mentuch Cooper, Robin Ciardullo, Daniel J. Farrow, Steven L. Finkelstein, Caryl Gronwall, Ho Seong Hwang, Byeongha Moon, Shun Saito, Donald P. Schneider

Solar and Stellar Astrophysics

High-resolution spectroscopy of the bipolar proto-planetary nebula Hen 3-1475, the Garden Sprinkler Nebula

Ana Valeria Beltrán-Sánchez, Miriam Peña and Mudumba Parthasarathy

A detailed analysis of high-resolution spectra in the optical and near-infrared range of the central zone of the proto-planetary nebula Hen 3-1475, obtained in 2006 and 2024, is conducted. The spectrum primarily revealed stellar emission of H Balmer and Paschen series, lines of iron (Fe I, Fe II, and [Fe II]), and other significant lines of He I, Ca II, [Ca II], and O I. Several multiplets of Fe II, the H Balmer series, Ca II H and K, Na I D and He I lines exhibit P-Cygni profiles and bump-like features, which are clear indicators of strong stellar winds. The terminal velocity of the winds was calculated, reaching values up to ~ 800 km/s. [Fe II] and Fe I lines were used as gas density indicators. In these observations, no photoionized nebular lines of planetary nebulae were identified, suggesting that the central star has not reached the temperature required to photoionize the nebula. A comparison between the observations from 2006 and 2024 reveals some few significant differences, being the most important the probably ejection of a new jet emerging from the central zone and the detection of a broad component adjacent to H \alpha, probably originating from emission associated with a jet at 700 km/s. High-spectral resolution observations of the knot NW1 obtained on August 2024, are also presented. This knot shows a typical spectrum of shocked gas. The emission of this knot has changed, presently not showing [O III] 5007 and other ionized lines that were reported in 2006.
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Earth and Planetary Astrophysics

Asymmetrical shape of the Near-Infrared K 4p-5s doublet perturbed by He and H2

N.F. Allard and J.F. Kielkopf

The goal of this paper is to provide an exhaustive study of the K 4p-5s doublet at 1.243/1.252~$\mu$m perturbed by He and H$_2$ in physical conditions of brown dwarfs. This work is applicable to analysis of the ESO SupJup Survey's J-band spectra such as for Luhman~16. Line profiles of this doublet computed within a unified line-shape theory exhibit a blue asymmetrical behavior. This effect is of increasing importance with He and H2 density, and as a result, the full treatment of the infrared K doublet reveals strong effects on its opacity outside the impact approximation. For a He and H2 perturber density larger than $10^{19}$~cm$^{-3}$ (0.4 bar) the impact approximation breaks down and is not applicable to calculate the shape of the line profiles and their line core parameters.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.space-ph

For SIRs, CIRs, and Beyond: Polarization Ratio to Feature Location

Curt A. de Koning, Dusan Odstrcil, Sarah Gibson et al. (+3 more)

The Polarimeter to UNify the Corona and Heliosphere (PUNCH) mission will remotely observe solar wind transients with high signal-to-noise ratio, high-cadence, high-resolution polarized white-light images. Using different polarization states, an important PUNCH data product will be polarization ratio images. In the small-Sun limit, and using two simple line-of-sight density distributions with a finite angular width that can approximate a stream or corotating interaction region (SIR/CIR), we analytically investigate how the polarization ratio will provide three-dimensional location information and what the uncertainty in this estimated location is.
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All authors Curt A. de Koning, Dusan Odstrcil, Sarah Gibson, Craig DeForest, Vic Pizzo, Christopher J. Scott

Earth and Planetary Astrophysics

Metal-Silicate Segregation During Planetary Accretion: Limited Iron Emulsification through intermediate Impacts

L. Honarbakhsh, G. Morra, P. Mora et al. (+1 more)

In this study, we investigate the post-collisional evolution of an impactor's iron core within a fully molten magma ocean using 2D numerical simulations with a novel Rothmann-Keller multiphase Lattice Boltzmann Method. The impactor's core diameter ranges from $152\;\text{km}$ to $552\;\text{km}$, with aspect ratios from $0.75$ to $5$. At Reynolds numbers up to $10^4$, our models reveal significant deformation and progressive fragmentation of the impactor into an iron cloud down to the smallest scale (several kilometers) that our method allows, which is then dispersed throughout the magma ocean by turbulent flow. We determined entrainment coefficients for a range of intermediate impactor sizes with various shapes, finding that larger impactors consistently exhibit higher entrainment coefficients. By extrapolating our mixing data, we anticipate incomplete iron-silicate mixing for kilometer-scale impactors in a real magma ocean, qualitatively consistent with previous predictions of partial equilibration. Additionally, our models highlight the mid- to lower magma ocean depths as critical zones for further iron fragment breakups and material transfer in the magma ocean.
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All authors L. Honarbakhsh, G. Morra, P. Mora, CRM. Jackson

Astrophysics of Galaxies

PhotoIFU: NIRCam as a Photometric Integral Field Unit for Mapping Feedback in Galaxies

Yongda Zhu, Marcia J. Rieke, Courtney Carreira et al. (+25 more)

We present PhotoIFU, a workflow that uses deep multi-band imaging as a low-resolution photometric integral field unit. Applied to PSF-matched JWST/NIRCam imaging, PhotoIFU treats each spatial pixel as a coarse SED element and fits the pixel SEDs with Prospector to map resolved stellar-population and ISM-related properties. We apply this approach to three galaxies at $z=1.3$–3.7 in JADES: two systems with extended ionized line emission and one post-starburst galaxy with an exceptionally strong neutral outflow. Pixel-by-pixel SED fitting gives maps of stellar-mass surface density, specific star formation rate, dust attenuation, gas-phase metallicity, and recent star-formation history. We find that regions selected from the extended-emission or outflow geometry occupy distinct parts of the resolved SED-property distribution compared with the full host. In the systems with extended ionized emission, these regions are generally less dusty, consistent with ionized emission being observed along dust-poor, low-column-density pathways through the host. In the neutral-outflow system, the selected regions show enhanced recent star formation, suggesting that compact rejuvenation may mark the aftermath of an earlier energetic phase. These results show that galactic outflows and extended emission-line structures can be spatially associated with measurable differences in resolved host-galaxy stellar populations and ISM-related properties. PhotoIFU provides an imaging-based method for resolved SED mapping of feedback-related structures in larger galaxy samples where full spectroscopic integral-field mapping is unavailable.
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All authors Yongda Zhu, Marcia J. Rieke, Courtney Carreira, Yang Sun, Zhiyuan Ji, Jianwei Lyu, Christina C. Williams, Stacey Alberts, Feng Yuan, Yuxuan Zou, Yurina Nakazato, Andrew J. Bunker, Sandro Tacchella, Fengwu Sun, George H. Rieke, Eiichi Egami, Jacopo Chevallard, Kevin Hainline, Zheng Ma, Pablo G. Pérez-González, Pierluigi Rinaldi, Bruno Rodríguez Del Pino, Tristen Shields, Meredith Stone, Christopher N. A. Willmer, Zihao Wu, Minghao Yue, Junyu Zhang

Earth and Planetary Astrophysics · Cross-listed from eess.SY

Drift-Aware Multi-Target Space Tug Logistics Using Natural Orbital Precession

Omer Burak Iskender, Leonard Felicetti, Kaan Gokturk et al. (+2 more)

Multi-rendezvous missions for active debris removal and in-orbit servicing incur prohibitive propellant costs when their targets differ in the orientation of their orbital planes, and classical mission design treats the nodal precession induced by Earth's oblateness as a perturbation to be cancelled. This paper presents a drift-aware trajectory optimisation framework that instead exploits that precession as a mission-design resource, benchmarked against the published winning solution to the European Space Agency's Kessler Run trajectory-optimisation competition as a trusted reference. Three methodological contributions are made. First, an enhanced drift orbit shapes the size, shape, and inclination of an intermediate orbit to tune the differential precession rate, substantially cheaper than the altitude-only designs of prior work in the Sun-synchronous regime, where inclination is the dominant lever. Second, a global per-leg time-budget optimiser makes explicit and resolves the coupling between drift-time allocation and downstream nodal geometry that defeats greedy allocation. Third, a sequence-recovery test independently re-derives a removal order consistent with the published reference from the debris catalogue alone. Applied to the full debris campaign on the published mission partition under the competition's transfer-time rules, the framework closely matches the published benchmark cost using only analytical transfer models and minutes of single-core computation. A cross-validation anchored to a widely used flight-dynamics tool quantifies the fidelity limits of the analytic model and bounds the cost of literal execution, and the constructive nature of the algorithm supports rapid in-orbit replanning after a missed manoeuvre.
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All authors Omer Burak Iskender, Leonard Felicetti, Kaan Gokturk, David Tellett, Adam Baker

Astrophysics of Galaxies

A quasar hatching from a buried red phase at z = 3.7

Zheng Ma, Yongda Zhu, Zhiyuan Ji et al. (+21 more)

We present JADES-GS 209777, previously cataloged as CANDELS J033238.02-274626.2, hereafter "the Hatchling," a red quasar at $z=3.711$. While the source has been reported in earlier deep-field catalogs, our multiwavelength analysis reveals a visible active nucleus still embedded in a dense gas- and dust-rich environment. Red quasar continua are often attributed to dust attenuation, including non-standard extinction curves, but the highly comprehensive multiwavelength data for this source provide direct constraints on the material being cleared. Using JWST/NIRSpec, NIRCam, MIRI, HST, MUSE, Chandra, ALMA, and VLA data, we detect broad emission lines and strong X-ray emission, showing that the active nucleus is at least partially exposed. We also detect H$\alpha$ and He I absorption, indicating dense gas close to the nucleus. Kinematically disturbed O I, Mg II, Na D, and [O III] features, together with extended Ly$\alpha$ emission over $\gtrsim 20$ kpc, further show that multiphase gas is being accelerated from the nuclear region into the host-galaxy environment. The ALMA detection reveals strong dust emission, with the inferred infrared luminosity placing the system in the ULIRG regime. The continuum is red and sharply declining toward the rest-frame UV, resembling compact red AGNs, and may reflect extreme dust attenuation, gas reprocessing, possible BAL-like absorption, or a combination of these effects. Regardless of which mechanism dominates the continuum shape, the line diagnostics show that the visible nucleus remains partially obscured by nearby material. The Hatchling therefore represents a unique opportunity to explore a poorly known transition phase in which feedback is likely clearing an enshrouded quasar and allowing it to emerge toward a more unobscured active nucleus.
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All authors Zheng Ma, Yongda Zhu, Zhiyuan Ji, Eiichi Egami, Marcia J. Rieke, Xiaohui Fan, Jianwei Lyu, George H. Rieke, Fengwu Sun, Yang Sun, George D. Becker, Andrew J. Bunker, Francesco D'Eugenio, Xiangyu Jin, Ignas Juodžbalis, Weizhe Liu, Roberto Maiolino, Pierluigi Rinaldi, Feige Wang, Christopher N. A. Willmer, Yunjing Wu, Jinyi Yang, Junyu Zhang, Peixin Zhu

Friday 24 July

High Energy Astrophysical Phenomena

Verifying Gamma-Ray Burst Duration Analysis Using the Compton Gamma-Ray Observatory T50 Data

Istvan Horvath

Several authors have shown in the literature that a third type of gamma-ray burst class can be detected in the Compton Gamma-Ray Observatory data using T90. In this paper, I examine whether this can also be found in the T50 variable data from the Compton Gamma-Ray Observatory Burst And Transient Source Experiment observation. According to my calculations, the third group detected in T90 can also be detected in the T50 data.
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Earth and Planetary Astrophysics · Cross-listed from physics.geo-ph

Revisiting a historically suspected impact structure in the Venezuelan Guiana Shield using SRTM topography

Miriam Rengel and Ekko Krumstroh

During the 1980s, aerial observations over the Venezuelan Guiana Shield led to the hypothesis that a circular geomorphological feature might represent an impact structure. Radar imagery was subsequently requested and circulated among researchers, but the interpretation remained unresolved. Recently rediscovered correspondence and imagery enabled a re-evaluation using modern digital elevation models from the Shuttle Radar Topography Mission (SRTM). The higher-resolution topographic data indicate that the structure lacks diagnostic morphologies of impact craters and is consistent with the Nuria ring dike intrusive complex. Comparison with analogous circular intrusive complexes, including the Kondyor massif, illustrates how circular morphology alone is insufficient for impact identification. This study documents a historical episode of geomorphological interpretation prior to the availability of modern digital elevation datasets and illustrates how improved topographic information and geological context can clarify the origin of ambiguous circular landforms relevant to planetary surface analysis.
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Solar and Stellar Astrophysics

SMDET-1: a Nearby Y Dwarf Candidate

Aaron M. Meisner, Dan Caselden, Federico Marocco et al. (+11 more)

We present the discovery of SMDET-1, a red, fast-moving object ($\mu \approx 1.3$"/yr) identified in time-resolved unWISE coadds using a pixel-level deep learning methodology called SMDET. Despite being relatively bright at 4.5 microns compared to many other recent WISE-based brown dwarf discoveries ($m_{[4.5]} \approx 14.6$ mag Vega), SMDET-1 had remained overlooked due to its location in a very crowded Galactic plane field ($b \approx 2.25^{\circ}$) and contamination from brighter background objects. SMDET-1 is also serendipitously detected at 4.5 microns in late-2012 Spitzer Deep GLIMPSE survey imaging. SMDET-1 is undetected in UKIDSS and Palomar/WIRC near-infrared imaging, with the strongest constraint on its temperature ($T_{\rm eff}$ < 391 K) arising from its Deep GLIMPSE color limit of $m_{[3.6]} - m_{[4.5]} > 2.81$ mag, which also implies a very nearby photometric distance < 7.4 pc. The Spitzer color bound corresponds to a Y dwarf phototype. SMDET-1 illustrates the importance of continued searches for nearby brown dwarfs within archival datasets like WISE and Spitzer, as well as the potential of pixel-level deep learning to discover astronomical moving objects that challenge traditional data analysis approaches.
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All authors Aaron M. Meisner, Dan Caselden, Federico Marocco, J. Davy Kirkpatrick, Jonathan Gagné, Adam C. Schneider, Samuel A. Beiler, Sergio B. Fajardo-Acosta, Jacqueline K. Faherty, Stanimir A. Metchev, Sam Barber, Marc J. Kuchner, Thomas P. Bickle, Zafar Rustamkulov

Instrumentation and Methods for Astrophysics

SuperFIRE: Concept evolution of a seeing-limited broadband spectrograph for the GMT

Gustav M. Pettersson, Gábor Fűrész, Nathan P. Lourie et al. (+4 more)

We are developing the SuperFIRE concept, which builds on the heritage of the FIRE spectrograph at Magellan, as a broadband (about 340 nm to 2.5 um) intermediate resolution (R=10,000) single-shot natural seeing spectrograph for the Giant Magellan Telescope (GMT) with support from the Kavli Foundation. This single-object spectrograph is envisioned as a first-light instrument that can operate in natural seeing and grow in long-term capability as the telescope and adaptive optics systems mature. Here we discuss how the science cases and design have evolved since the concept was initially conceived and presented at SPIE in Edinburgh ten years ago. The primary drivers for the design changes are fast follow-up of faint transients and multi-messenger events, and complementarity to JWST observations in the infrared. By leveraging fast low-noise detectors and modern fabrication techniques we expect high throughput and low scatter that delivers sky limited performance in a few minutes of integration time for fast response and deep integrations. SuperFIRE will operate as a practical point-and-shoot follow-up spectrograph thanks to a versatile standard configuration that needs minimal observing or planning overheads and is insensitive to atmospheric conditions.
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All authors Gustav M. Pettersson, Gábor Fűrész, Nathan P. Lourie, F. Elio Angile, Jill Juneau, Gerardo Berlanga Molina, Robert A. Simcoe

Earth and Planetary Astrophysics

Tracing outer planetary systems through white dwarf pollution in wide binaries

Carolina Lizana-Vidal, Claudia Aguilera-Gómez, Laura K. Rogers et al. (+5 more)

White dwarf (WD) atmospheric metal pollution provides strong evidence for the presence of remnant planetary material and it can be used as an indirect tracer of outer planetary systems. We analyze whether the presence of a wide stellar companion affects the occurrence of outer planetary systems by comparing the incidence of calcium (Ca) pollution in hydrogen-atmosphere WDs in wide binaries and in apparently single stars. We construct two sample pairs: a large homogeneous SDSS low-resolution spectroscopic set and a smaller high-resolution sample. For each WD, we measure Ca abundances or upper limits and compute detectability-corrected cumulative pollution fractions that account for variations in effective temperature, signal-to-noise ratio, and spectral resolution. In the SDSS-based samples, we find pollution fractions <1%, defined as the fraction of WDs with detected Ca, for both single WDs and WDs in wide binaries. After correcting for detectability, the cumulative abundance distributions of the two populations are statistically consistent. The same conclusion is obtained for the higher-resolution samples, despite their different raw detection fractions. Our results indicate no statistically significant difference in the occurrence rate of remnant outer planetary systems between single stars and stars with wide (~200 au) companions, within the current uncertainties. These uncertainties are significant because the samples contain only a small number of polluted WDs. The corrected detectability cumulative fraction approach used here provides a framework for comparing samples with different detection sensitivities and can be extended to larger spectroscopic datasets. Such samples will be required to determine whether wide stellar companions affect the survival and delivery of planetary material and to search for more subtle trends, for example, as a function of companion separation.
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All authors Carolina Lizana-Vidal, Claudia Aguilera-Gómez, Laura K. Rogers, Amy Bonsor, María Ignacia Muñoz-Arriagada, Patrick Dufour, Constanza Bravo-Parra, Ema Salugova

Cosmology and Nongalactic Astrophysics

Stability in Axion Inflation with Strong Backreaction from a Massive Vector Boson

Michael J. Baker, Joaquim Iguaz Juan and Lorenzo Sorbo

We study a modification of the model of axion inflation coupled to a $U(1)$ gauge field where the vector field is massive. In the conventional scenario with a massless gauge field, the onset of the regime where the gauge field strongly backreacts on the inflaton displays an instability whose nonlinear evolution and endpoint remain poorly understood. We argue that, if the gauge field is massive enough, the transition to the strong backreaction regime instead occurs smoothly, avoiding this instability. This observation suggests that axion inflation with massive gauge fields admits a controllable strong backreaction regime, so that a phenomenologically viable realization of inflation might be possible in this class of models.
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Earth and Planetary Astrophysics

The JDISC Survey: Inner Disk Chemistry of Class I/FS Disks and Tentative Evidence for Early Pebble Drift

Ke Zhang, Andrea Banzatti, Colette Salyk et al. (+22 more)

We present the first chemical survey of Class I and Flat-Spectrum (I/FS) disks using JWST MIRI/MRS, targeting sixteen sources in the Ophiuchus star-forming region. Through empirical line luminosity measurements and multi-component slab modeling, we characterize the molecular reservoir of these young systems and compare them to twelve Class II disks of similar stellar mass. Water, HCN, C$_2$H$_2$, and CO$_2$ are frequently detected in I/FS sources with inclinations $i < 70^{\circ}$, whereas edge-on systems show significantly suppressed emission. Compared to Class II disks, I/FS sources show suggestive—though not yet statistically significant—evidence for elevated cold water ($\sim$200\,K) mass and lower CO$_2$ excitation temperatures. Statistical analyses identify accretion luminosity as the primary correlate of molecular mass across both evolutionary stages. Once this dependence is removed, cold water and CO$_2$ masses anti-correlate with mm-dust disk radius, while hot water remains insensitive to disk size. These patterns are qualitatively consistent with pebble drift models that predict early water enrichment followed by delayed CO$_2$ delivery, suggesting an evolutionary progression from molecular-poor Class 0 sources, through water-rich Class I/FS disks, to Class II disks with reduced cold water excess. This work provides an initial evolutionary framework for disk chemistry that requires larger, multi-region samples to confirm.
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All authors Ke Zhang, Andrea Banzatti, Colette Salyk, Abygail Waggoner, Klaus Pontoppidan, María José Colmenares, Ilaria Pascucci, Lucas A. Cieza, Miguel Vioque, Paola Pinilla, Geoffrey A. Blake, Joan Najita, Joe Williams, Sebastiaan Krijt, Till Kaeufer, Jane Huang, Feng Long, Chengyan Xie, Minjae Kim, Eshan Raul, Dary A. Ruíz-Rodríguez, Nicole Arulanantham, Benoît Tabone, Mayank Narang, Karina Mauco

Astrophysics of Galaxies

The role of filaments in the large-scale conformity signal

Daniela Palma, Ivan Lacerna, Noelia Pérez et al. (+8 more)

We investigate the large-scale conformity signal and its connection with the large-scale structure, focusing on low-mass central galaxies, after excluding galaxies that were satellites in the past. We measure the signal across different environments identified with the DisPerSE algorithm, including group outskirts, cluster outskirts, filaments, filament outskirts, and other environments (voids and walls) in order to assess how each population contributes to the large-scale conformity signal. We use the galaxy catalogs from the IllustrisTNG300 simulation and the semi-analytic model MDPL2-SAG. In SAG, galaxies embedded in filamentary regions emerge as the primary contributors to the large-scale conformity signal, closely reproducing its overall shape and amplitude. In TNG300, galaxies located in filamentary regions also exhibit a coherent, albeit weaker, conformity signal once galaxies that were satellites in the past are excluded. We also examine whether the signal depends on the adopted filament definition. We find no substantial differences when varying the filament thickness or considering galaxies in overlapping regions. Instead, the signal remains strong and largely insensitive to these differences. We then investigate the dependence of the conformity signal on filament linear density, length, and mass. The signal is enhanced in high-linear density, short, and high-mass filaments, but remains present in low-linear density, long, and low-mass filaments, although with a slightly lower amplitude. Finally, we find that low-mass central galaxies located in close proximity to interacting massive systems show an amplified conformity signal extending up to 4 Mpc/h. Overall, our results indicate that filamentary regions, and the tidal forces from neighboring massive systems play a fundamental role in shaping the large-scale conformity signal.
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All authors Daniela Palma, Ivan Lacerna, Noelia Pérez, Luis Pereyra, Antonio D. Montero-Dorta, Constanza A. Soto-Suárez, Laerte Sodré Jr., M. Celeste Artale, Amrutha Belwadi, Facundo Rodriguez, Nelvy Choque-Challapa

Solar and Stellar Astrophysics

1000 cataclysmic variables identified from DESI spectroscopy

K. Inight, B. T. Gänsicke, A. Aungwerojwit et al. (+41 more)

Most cataclysmic variables (CVs) are discovered when they have an outburst generating an inherent selection bias against CVs that rarely, or never, outburst. CVs discovered by virtue of their spectroscopic characteristics are particularly valuable to offset this bias and we have used an established machine-learning technique to assist in searching 98 966 000 spectra obtained by the Dark Energy Spectroscopic Survey (DESI) to find such CVs. DESI observations are much deeper than previous spectroscopic surveys and we have identified 1029 CVs, 221 of which are new including ten of the AM CVn subtype. We have spectroscopically confirmed 441 CV candidates and obtained 84 new or improved orbital periods. We present revised space density estimates based upon this new data. We have also added ten more to the eight known examples of an intriguing class of CVs which exhibit peculiar changes in accretion.
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All authors K. Inight, B. T. Gänsicke, A. Aungwerojwit, P. Izquierdo, C. J. Manser, A. D. Myers, A. Swan, J. R. Thorstensen, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, Biprateep Dey, P. Doel, A. Font-Ribera, J. E. Forero-Romero, Satya Gontcho A Gontcho, G. Gutierrez, J. Guy, R. Joyce, S. Juneau, S. E. Koposov, A. Kremin, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, J. Najita, I. Pérez-Ràfols, W. J. Percival, F. Prada, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, H. Seo, J. Silber, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou

Astrophysics of Galaxies

Unsupervised selection and characterisation of Little Red Dots in JWST surveys with manifold learning

Michele Ginolfi, Filippo Mannucci, Alessandro Marconi et al. (+9 more)

Little Red Dots (LRDs) are compact, red sources discovered at high redshift by JWST whose physical nature and selection function remain debated. We investigate whether an unsupervised machine-learning approach applied to multi-band photometry can identify LRD-like objects, and other populations, without relying on predefined colour cuts. Using UMAP, a manifold-learning (dimensionality-reduction) method, we place ~242,000 isolated, well-measured sources from the ASTRODEEP-JWST catalogue on a two-dimensional map, where objects with similar broadband colours, morphology, and photometric redshift lie close together. We then use spectroscopically confirmed LRDs to identify where LRD-like objects lie within this map, compare the resulting areas with published colour cuts, and validate our data-driven selection against archival NIRSpec spectra from the DJA. We find that the spectroscopically selected LRDs concentrate in two well-defined regions with no colour cut imposed, tracing populations that differ mainly in redshift, a difference imprinted in their broadband colours. The main region reaches a purity of ~0.78 at ~0.82 completeness on the spectroscopically classified subset, competitive with, or cleaner than, literature colour cuts, and yields ~100 additional candidates. We also test the method as a general tool for population discovery: the manifold recovers the locations of brown dwarfs and broad-line AGN with no explicit criterion, and isolates rare pathological outliers. Overall, unsupervised manifolds, anchored by sparse high-confidence spectroscopic labels, provide an efficient, assumption-light framework for characterising populations, comparing selection methods on a common basis, and discovering rare objects in large photometric datasets.
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All authors Michele Ginolfi, Filippo Mannucci, Alessandro Marconi, Francesco D'Eugenio, Giacomo Venturi, Francesco Belfiore, Giovanni Cresci, Caterina Bracci, Stefano Carniani, Alessandra Cozzi, Roberto Maiolino, Guido Risaliti

Astrophysics of Galaxies

Reionization driven by the few: the ionizing budget of galaxies at z=5-10 from JWST/NIRSpec

Emma Giovinazzo, Pascal A. Oesch, Anne Verhamme et al. (+5 more)

The sources responsible for the Epoch of Reionization (EoR), the last major phase transition of the Universe, remain highly elusive. While JWST has begun to illuminate the properties of early galaxies, the direct detection of their ionizing photons is virtually impossible due to the neutral intergalactic medium (IGM) at z>6. A direct estimate of the escape fraction of ionizing photons (fesc) is thus not possible. However, the escape fraction is encoded in spectral features that trace a low opacity to ionizing photons, namely the reduction of nebular emission with increasing fesc. Here, we exploit the large archive of JWST/NIRSpec spectra at 5<z<10 from the DAWN JWST Archive to provide new constraints on the ionizing emissivity of EoR galaxies and on the timeline of reionization. Through detailed spectral fitting of 1428 galaxies with a picket-fence model for the escape of ionizing photons, we derive posteriors of fesc together with the effective ionizing output. This approach yields the escaping ionizing output of each galaxy while bypassing the usual decomposition into the ionizing photon production efficiency and fesc. Combining these measurements with UV luminosity functions (LFs), we derive the hydrogen ionizing LFs, resulting in an observationally-derived ionizing photon budget at 5<z<15, integrated down to MUV=-13. Under standard assumptions, our budget yields an evolution of the IGM neutral fraction consistent with independent probes, with reionization ending at z~5.8. Given the evolving shape of the ionizing LF, bright sources (MUV ~ -20) dominate the cosmic ionizing emissivity nion at lower redshift (z=5-6), whereas at z>6 faint galaxies (MUV > -18) contribute roughly equally. Remarkably, a mere ~20% of sources, those with fesc>10%, produce ~87% of the ionizing photons. Overall, our results support a picture in which a few strongly leaking galaxies drive most of reionization.
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All authors Emma Giovinazzo, Pascal A. Oesch, Anne Verhamme, Romain A. Meyer, Callum Witten, John Chisholm, Rui Marques-Chaves, Charlotte Simmonds

Solar and Stellar Astrophysics

BOSS-CLAM: Utilizing a Constrained Linear Absorption Model to Infer Stellar Parameters from BOSS Spectra

Ilija Medan, Andrew R. Casey, Alexander P. Ji et al. (+13 more)

Large spectroscopic surveys require robust pipelines capable of inferring stellar parameters over a wide range of the Hertzsprung-Russell (HR) diagram from data of varying quality. SDSS-V is one such survey, where the data from the lower-resolution, optical BOSS spectrograph will provide a large dataset covering a wide range of Galactic stellar populations. To better analyze these data, we present BOSS-CLAM, a generative, forward modeling pipeline for inferring effective temperature ($T_\mathrm{eff}$), surface gravity ($\log g$), metallicity ($[\mathrm{Fe/H}]$), and $\alpha-$abundance ($[\alpha/\mathrm{M}]$) from continuum-normalized BOSS spectra. BOSS-CLAM maps stellar labels to Non-negative Matrix Factorization (NMF) basis vector weights via a polynomial mapping jointly optimized with the spectral decomposition, which provides a more flexible framework for working with the lower-resolution BOSS data. Additionally, training labels are drawn from four complementary sources (ASPCAP, BOSS-MINESweeper, wide binaries, and a hot star validation sample), which enables coverage from cool M dwarfs through hot OB stars, and across a wide range of metallicity. We infer parameters for 1,708,214 BOSS spectra, with a recommended clean catalog of 915,514 sources. Validation against open and globular clusters demonstrates homogeneous, accurate abundances across a wide range of metallicity. Wide binary tests yield abundance uncertainties of $\sigma_{[\mathrm{Fe/H}]} \approx 0.15$ dex and $\sigma_{[\alpha/\mathrm{M}]} \approx 0.06$ dex at SNR = 10. Finally, we demonstrate that the BOSS-CLAM catalog recovers known chemical structure of the Milky Way disk and is well-suited for Galactic archaeology, chemical tagging, and stellar population modeling. The pipeline, trained model, and catalog are publicly released as part of SDSS-V DR20.
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All authors Ilija Medan, Andrew R. Casey, Alexander P. Ji, Jonah M. Otto, Kayvon Sharifi, Zachary Way, Madeleine McKenzie, Natalie R. Myers, Keivan G. Stassun, Peter J. Smith, Andrew Tkachenko, Vedant Chandra, Michael R. Blanton, Peter M. Frinchaboy, Guy S. Stringfellow, Sean Morrison

Earth and Planetary Astrophysics

SCoRE: the Surface Composition of Rocky Exoplanets

Leon Sereinig and Oliver Herbort

Context. The crust composition of rocky exoplanets with a substantial atmosphere can not be observed directly. However, recent developments are starting to allow for the observation and characterisation of their atmospheres. Understanding the link between atmospheres and crusts could allow for constraints on the crusts' composition based on atmospheric observations. Aims. We aim to understand the link between the thermal stability of specific condensates and atmospheric compositions. This allows constraints on the mineralogical composition of the surface by potentially observable atmospheric features. In order to achieve this, a grid study of atmospheric and crustal compositions is conducted. Methods. We use a diverse range of total element abundances inspired by various rock compositions as the compositional base for our crust-atmosphere models, for which thermo-chemical and phase equilibrium is assumed. In this work, we investigate a temperature range of 500 K to 1000 K and a surface pressure of 1 bar. The resulting atmospheric compositions are classified using atmospheric types based on the most abundant gas-phase elements C, H, N, O, and S. Results. Some of the changes in surface mineralogy coincide with changes in atmospheric type, independent of the given total elemental abundances. In total, a link has been revealed between 23 thermally stable minerals and their corresponding atmospheric types, which is independent of the ratio of the refractory elements present. Especially, the sulphur chemistry of the minerals and the average iron oxidation state can be constrained by the corresponding atmospheric type.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

$\texttt{SNuDD}$: Solar Neutrinos for Direct Detection

Dorian W. P. Amaral, David Cerdeño, Andrew Cheek et al. (+2 more)

We introduce Solar Neutrinos for Direct Detection ($\texttt{SNuDD}$): an open-source Python package that enables the computation of the solar neutrino rate spectrum at direct detection experiments. $\texttt{SNuDD}$ can be used to determine the differential rate for both nuclear and electron recoils within the Standard Model and in the presence of beyond Standard Model physics effects, such as those arising from neutral-current non-standard interactions (NSI). The package accounts for matter effects during neutrino propagation through both the Sun and the Earth and for modifications to the scattering cross sections at the interaction site. We employ $\texttt{SNuDD}$ to place new limits on the effective NSI couplings using results from the xenon-based direct detection experiments LZ, XENONnT, and PandaX-4T, and we project the sensitivity of a future xenon detector based on the planned XLZD and PandaX-xT observatories. We find that current direct detection experiments are rapidly approaching sensitivities comparable to those of dedicated neutrino experiments and that future xenon detectors can provide leading constraints. We recommend that $\texttt{SNuDD}$ be used to combine incoming direct detection data with those from neutrino experiments in future global fits, placing direct detection within the broader landscape of neutrino physics.
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All authors Dorian W. P. Amaral, David Cerdeño, Andrew Cheek, Valeria Costa, Patrick Foldenauer

Cosmology and Nongalactic Astrophysics

Relativistic Chiral MHD with application to the early Universe

Deepen Garg and Jennifer Schober

We present a systematic derivation of the equations of relativistic chiral magnetohydrodynamics (MHD) for a plasma of charged fermions in an expanding universe. Through a combination of a coordinate transformation and a rescaling of the dynamical variables, we bring the full system to the same form as in the Minkowski metric, with the Hubble expansion surviving only in the chirality-flipping rate and the kinematic viscosity. Retaining all four contributions to both the electric and the axial current yields terms absent from standard chiral MHD: charge-density corrections to the evolution equations for the chemical potentials, and an electric current proportional to the charge chemical potential $\mu$ and the bulk velocity. The latter is mandated by current conservation, requires no chirality imbalance, and drives the charge-flow instability studied in a companion paper. For the radiation-dominated era, we evaluate all the coefficients in physical units and use them to estimate the magnetic Reynolds number, the attainable magnetic field strength, and the minimum temperature at which the chiral dynamo can operate. The resulting equations are cast in a form ready for direct numerical implementation.
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Cosmology and Nongalactic Astrophysics

A charge-flow instability in plasmas with charge fluctuations

Deepen Garg and Jennifer Schober

We present a linear instability in magnetized plasmas with charge fluctuations. It is driven by an electric current proportional to the charge chemical potential $\mu$ and the bulk velocity. This charge-flow (C-flow) instability has hitherto not been considered in standard magnetohydrodynamics or its chiral extensions. We derive its dispersion relation and maximum growth rate, and confirm them with direct numerical simulations. We also show that the C-flow instability persists even for zero-mean fluctuations of $\mu$, vanishing resistivity, and a magnetic Prandtl number of unity.
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Astrophysics of Galaxies

Charting the Galactic Underworld I: Comprehensive simulations of the kinematics, rates, and demographics of Milky Way black holes

Tom Wagg, Katelyn Breivik, Adrian M. Price-Whelan et al. (+3 more)

With upcoming data from Roman, Gaia DR4, and spectroscopic surveys, we will soon have an unprecedented dataset of Milky Way black holes (BHs) to constrain their formation and evolution. To prepare, we simulate the intrinsic population of Milky Way BHs with cogsworth, self-consistently accounting for their binary evolution and trajectories through the Galactic potential. We report the rate, demographics, and kinematics of these BHs, and their sensitivity to 32 variations in binary evolution, supernova physics, and Galactic potentials. In the fiducial model, ~$1.7 \times 10^8$ BHs have formed in the Milky Way (though this total spans an order of magnitude across our variations), where the vast majority (~91%) are currently isolated and ~3% have escaped the Galaxy. Most of the ~$10^7$ BHs in binaries have another BH or a white dwarf companion, but ~$10^5$ retain a luminous stellar companion. BHs are distributed more diffusely than visible stars, with a scale height around ~$2.5\times$ larger. BH masses correlate with present-day location: the most massive BHs are preferentially close to the Galactic plane. This correlation is especially strong for BH-star binaries, which separate into tight, low-mass post-common-envelope systems and wide, high-mass non-interacting ones. The BH mass distribution and kinematics are highly sensitive to the remnant mass prescription and natal kick model, so observations could constrain explodability criteria and BH kicks. Accounting for the time-evolution of the Galactic potential more than doubles the escape fraction and increases the bound population's scale height by ~20%, whilst neglecting binary interactions overestimates it by 30%.
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All authors Tom Wagg, Katelyn Breivik, Adrian M. Price-Whelan, Mathieu Renzo, Julianne J. Dalcanton, Natasha S. Abrams

Astrophysics of Galaxies

Speeding up Gravitational Lens Mass Models with Machine Learning: Applications in X-ray Astronomy

Alex Ostridge, Rafael Martínez-Galarza, Júlia M. Sisk-Reynés et al. (+2 more)

Multi-wavelength observations of quadruply lensed quasars constitute a powerful probe of cosmology, dark matter substructure along the line of sight, and the structure of X-ray emitting regions in high-redshift quasars. These investigations are conditional on acquiring an accurate model for the surface mass density of matter lensing these quasars. We propose a simulation-based machine learning method to accelerate parameter inference in real quadruply lensed systems by several orders of magnitude. We simulate a grid of quadruply lensed sources with Singular Isothermal Ellipsoid (SIE) lenses and use the projected positions of the four lensed images to train two fully connected neural networks that predict the mass parameter and ellipticity. For a large fraction of simulated systems, the neural network-initialised mass models converge in time-scales of a few minutes and recover the source position at the <0.”005 level for a broad range of lens masses and ellipticities. We apply our neural networks to seven quadruply lensed quasars, lensed by isolated galaxies or a galaxy-perturber pair, which have archival Chandra observations. The final optimised mass models for each quasar predict the observed lensed image positions in Gaia Data Release 3. These mass models enable the caustic method, which locates the X-ray-to-optical emission regions to milliarcsecond precision in these otherwise unresolvable systems, improving the effective angular resolution of Chandra at high-z by up to two orders of magnitude. Our approach accelerates this mass modelling by supplying informed initial parameters, enabling application to the many new quadruply lensed systems expected from forthcoming surveys.
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All authors Alex Ostridge, Rafael Martínez-Galarza, Júlia M. Sisk-Reynés, Daniel A. Schwartz, Anna Barnacka

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Axion isocurvature and the model-building problem of low-scale inflation

Sarunas Verner

The pre-inflationary QCD axion is often said to require low-scale inflation. We derive a general isocurvature bound for a light axion with a scale-invariant spectrum, treating its inflationary normalization $f_I$ independently of the late-time decay constant $f_a$ and allowing for an arbitrary axion dark matter fraction, nontrivial perturbation transfer, and the full anharmonic abundance response. In the minimal benchmark, where axions constitute all of the dark matter, $f_I=f_a\leq M_{\rm Pl}$, and the angular perturbation is conserved, the least restrictive CMB limit considered gives the 95% C.L. upper bound $H_I<1.25\times10^{10}\,\mathrm{GeV}$ on the inflationary Hubble scale. For an initial misalignment angle $\theta_i=1$, the bound strengthens to $H_I<2.2\times10^7\,\mathrm{GeV}$, with still stronger constraints near the hilltop. Combining the isocurvature and tensor spectra yields axion-tensor and axion-conditioned Lyth bounds. If the observed curvature perturbation is generated by a canonical cold single-field slow-roll inflaton and the tensor amplitude varies slowly across the observable CMB window, these relations limit the inflaton excursion to $\Delta\phi_{\rm CMB}/M_{\rm Pl}\lesssim10^{-7}\text{-}10^{-4}$ and require $|M_{\rm Pl}V'/V|\sim10^{-8}\text{-}10^{-5}$ while $M_{\rm Pl}^2V''/V\sim-10^{-2}$. This hierarchy favors models with independent control of the inflationary scale, potential derivatives, exit, and reheating, including hybrid, running-mass, and inflection-point models. Reheating and the requirement of Peccei-Quinn non-restoration sharpen these conditions, while nonminimal scenarios can relax them by modifying the primordial fluctuation, its transfer, or the relic abundance.
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