Peer Revenue Impact factor: volatile

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 29 August

Solar and Stellar Astrophysics

On the Effect of Large Scale Structures and Turbulence on Solar Eruptive Events: The Cross-Scale Challenge for Space Weather

Alessandro Ippolito, Giuseppe Prete, Nicolas Wijsen et al. (+4 more)

Coronal Mass Ejections (CMEs) are among the most powerful drivers of space weather, yet their prediction remains elusive. A fundamental obstacle is the problem's multiscale nature: large-scale magnetohydrodynamic models do not resolve the turbulent fluctuations that govern particle transport and magnetic connectivity. We present a new model that combines a MICroscopic diffusion approach of turbulence with MACroscopic EUHFORIA simulations (MICMAC) to address the cross-scale challenge of space weather. By incorporating turbulence properties into such small-scale Monte Carlo simulations, we describe an extreme CME event, tracing both magnetic field lines and 100 MeV protons from the CME-driven shock to 1 AU. We find that turbulence dramatically broadens and distorts the magnetic connection between the CME nose and Earth, producing footpoint distributions that are highly non-Gaussian, anisotropic, and patchy. MICMAC suggests that the distribution's enstrophy (non-Gaussianity) grows as the CME approaches Earth, signaling anomalous diffusive behavior. A simple shear-layer toy model reproduces the observed in-plane anisotropy, suggesting that local current sheet geometry imprints a persistent memory on the turbulent field. Our results demonstrate that cross-scale coupling between the CME's large-scale structure and ambient turbulence must be accounted for in space weather models. We discuss implications for SEP forecasting and interpreting multi-spacecraft observations.
Read the full abstract

All authors Alessandro Ippolito, Giuseppe Prete, Nicolas Wijsen, Gaetano Zimbardo, Anwesha Maharana, Stefaan Poedts, Sergio Servidio

Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

Automated identification and subtraction of gravitational-wave glitches using boundary refinement

Mohammad Abu Thaher Chowdhury and Soumya D Mohanty

Transient noise artifacts, or glitches, in gravitational wave strain data elevate the false alarm rate of astrophysical searches and degrade parameter estimation when overlapping a signal. No method previously identified a glitch's time boundary: existing detection and classification tools flag and label glitches without resolving their extent, forcing subtraction to run over padded windows that cost time and erase signal beyond the glitch itself. We present three boundary identification methods, AMPS (Amplitude-based Multi-glitch Pulse Segmenter), FLARE (Fitness-based Localization And Refinement Extractor), and CRISP (connected-region identification via spectrogram power), paired with three subtraction techniques, adaptive spline fitting, wavelet shrinkage, and their combination, across five glitches from the GravitySpy database spanning Advanced LIGO's first three observing runs. AMPS sets a boundary from a robust amplitude threshold, FLARE from the best fitness of a segmented spline fit, and CRISP from spectrogram power. Injecting a chirp signal on four broadband glitches, the combined technique recovers 95 to 97 percent of the injected signal-to-noise ratio, against roughly 64 percent for wavelet shrinkage alone. CRISP gives the most uniform boundary width across glitches; AMPS and CRISP both identify a boundary in a fraction of a second, two to three orders of magnitude faster than FLARE. For the glitch overlapping GW170817, a low-frequency residual persists under the default boundary, a deliberate tradeoff against removing signal power. Scattered light glitches remain untested and are the primary direction for future work.
Read the full abstract

Earth and Planetary Astrophysics

The refractory fraction of phosphorus in planet-forming discs

Sandipan P. D. Borthakur, Mihkel Kama, Luca Fossati et al. (+3 more)

Context. Phosphorus (P) is an essential element for life on Earth and a potential tracer of planet formation history. However, there has been no detection of P-bearing molecules in protoplanetary discs so far. Herbig Ae/Be stars constantly accrete matter from their pro- toplanetary disc, which alters the composition of the stellar photosphere due to their shallow convective, or fully radiative, envelope. The altered surface composition reflects the composition of the accreting matter, and thus that of the inner protoplanetary disc. This accretion contamination of stellar photosphere can persist after accretion has ended in young A and B-type stars (age < 50 Myr). Aims. We aim to quantify the fraction of P locked in dust (the refractory fraction of P) compared to gas in the inner protoplanetary disc around Herbig Ae/Be stars. Methods. We measure the stellar parameters and abundance of 5 Herbig Ae/Be stars using optical and UV spectra, to compare their P and Fe abundances. We also used a 20 Myrs old main sequence B-type star, which has P and Fe abundance estimated from optical spectrum. Fe is assumed to be completely locked in refractory reservoirs in the inner disc. A parameterised relationship between the stellar P and Fe abundance gives the fraction of P locked in refractory reservoirs. Results. We find the refractory fraction of P in the inner protoplanetary disc to be > 96 % within 95th percentile of the posterior distribution. Conclusions. Consistent with a previous finding in the HD 100546 system, we conclude most of the P in the inner protoplanetary disc is locked in dust, likely in refractory minerals like schreibersite or apatite. Our result, combined with the low cosmic abundance of P, is also consistent with the lack of infrared and mm-wavelength observations of P-bearing molecules in protoplanetary discs to date.
Read the full abstract

All authors Sandipan P. D. Borthakur, Mihkel Kama, Luca Fossati, Colin P. Folsom, Anna Aret, Christiane Helling

Solar and Stellar Astrophysics

Evolution of Stellar Activity and Habitable Zone (EATEN): III. X-ray Activity of Dwarfs in Open Clusters and Field Stars

Xue Li, Song Wang, Henggeng Han et al. (+3 more)

Stellar X-ray emission serves as a direct diagnostic of coronal activity, which is fundamentally linked to coronal heating processes. It also strongly influences the atmospheres and long-term habitability of orbiting exoplanets. Investigating how this high-energy emission evolves is therefore essential for understanding the evolution of stellar magnetic dynamos and planetary atmospheres and habitability. In this work, we investigate the evolution of X-ray activity and XUV irradiation for a sample of F-M dwarf stars based on Chandra and XMM-Newton observations. We find that F- and G-type stars broadly follow the traditional evolutionary picture of an early saturated (or weakly declining) phase followed by a modest decline, whereas K- and M-type stars exhibit a clear three-phase evolution of a saturated phase, an intermediate phase of rapid decay, and a final modest decline phase. By combining X-ray, ultraviolet, and Ca II H&K bands, we show that coronal emission becomes increasingly dominant toward lower-mass stars. Based on the cumulative XUV emission calculated from our fitted relation, planets around F- and G-type stars experience relatively moderate XUV environments, while those around K- and M-type stars may exceed the empirical cosmic shoreline shortly after reaching the main sequence, though this conclusion depends on the adopted shoreline value.
Read the full abstract

All authors Xue Li, Song Wang, Henggeng Han, Jun Ma, Yang Huang, Jifeng Liu

Cosmology and Nongalactic Astrophysics

The onset of the strong backreaction regime in axion inflation, an analytical study

Aditya Kulkarni and Lorenzo Sorbo

Models where an axion-like inflaton is coupled to a $U(1)$ gauge field are theoretically well motivated and can display a rich phenomenology. The regime in which the quanta of the gauge field strongly backreact on the rolling inflaton has been studied for well more than a decade, and yet we cannot say that it is fully understood. In this paper we present an analytical study of the onset of the strong backreaction regime. Our formalism relies on a Laplace transform to convert a complicated integro-differential equation into the search of the poles of an analytic function. We confirm the existence, previously observed using a completely different formalism, of a stable region of strong backreaction. Our work provides, for the first time, analytical formulae that allow to study the evolution of the system as it transitions from the weak to the strong backreaction regime.
Read the full abstract

Astrophysics of Galaxies

The Cygnus Allscale Survey of Chemistry and Dynamical Environments: CASCADE: VI. Molecular outflows in the DR21 ridge

I. M. Skretas, A. Karska, F. Wyrowski et al. (+8 more)

Star formation takes place in varied environments, from isolated clumps to massive molecular cloud complexes. However, whether the environment in which a star forms has any effect on the formation process remains a matter of debate. The molecular outflows, launched during the formation of protostars present a more easily accessible way to study star formation in different environments. The DR21 ridge, in the Cygnus-X high-mass star-forming complex, hosts a high number of massive dense cores and embedded protostars with outflows. We aim to identify molecular outflows associated with dense molecular cores along the DR21 ridge, and investigate whether the extended environment impacts the formation process of stars within it. We identified molecular outflows along the DR21 ridge using HCO+ J=1-0, H13CO+ J=1-0, and SiO J=2-1 observations obtained with the IRAM 30m telescope and NOEMA as part of the CASCADE program. We calculated outflow properties and performed statistical comparisons between the DR21 ridge sources and a literature sample of low- to high-mass outflow sources. Based on the morphology of HCO+, H13CO+ and SiO, we identify molecular outflows in 14 out of 34 dense cores (41%) along the DR21 ridge. Despite the high density of star formation in DR21, the resulting outflow properties are found to be in good agreement with the established correlations between outflow and source properties. Little variation is seen in the outflow properties of sources along the ridge, with the exception of sources located at the intersection of the DR21 ridge with large-scale (~1 pc) accretion filaments. These sources are found to drive the most powerful outflows. Overall, our results indicate that protostellar outflow properties, even when driven by sources forming in an extreme and clustered region, such as the DR21 ridge, remain largely unaffected.
Read the full abstract

All authors I. M. Skretas, A. Karska, F. Wyrowski, H. Beuther, W.-J. Kim, C. Gieser, D. A. Semenov, A. Hernández-Gómez, N. Schneider, T. Csengeri, A. Hacar

Instrumentation and Methods for Astrophysics

How nanoscale physics shapes ice formation in the Universe: Rethinking gas freeze-out on dust grains

Philippe Parent, Carine Laffon, Stefano Curiotto et al. (+3 more)

In cold molecular clouds, gas freeze-out onto dust grains initiates interstellar ice formation, yet sticking probabilities of heavy species are often assumed to be near unity at low temperature. Recent laboratory measurements on realistic grain analogues show that this assumption can fail. Using CO as a prototype, we investigate how nanoscale surface morphology controls adsorption and ice growth at 10 K on highly oriented pyrolytic graphite and carbon soot. X-ray photoelectron spectroscopy, low-temperature scanning tunneling microscopy, kinetic Monte Carlo simulations, and a thermodynamic description are combined to relate molecular retention to local surface structure. CO does not adsorb with unit sticking on graphite: adsorption proceeds through monolayer growth, a reduced-retention crossover near monolayer completion, and delayed multilayer growth. STM shows that CO remains highly mobile on graphite terraces and is stabilized mainly at island edges and terrace steps. On soot, the same sequence occurs at much higher exposures and with substantially lower sticking coefficients, while simulations show preferential retention in concave regions and poor wetting of convex asperities. These results indicate that low-temperature sticking is governed by post-impact exploration and competition between stabilization and escape. Nanoscale morphology amplifies this mechanism, reducing effective sticking probabilities and delaying gas freeze-out on realistic dust grains.
Read the full abstract

All authors Philippe Parent, Carine Laffon, Stefano Curiotto, Daniel Ferry, Caroline Stadler, Frederik Granzow Doktor

Earth and Planetary Astrophysics

Dynamical Mass Demography of Single S-type Planets Shaped by Stellar Companions

Xiumin Huang and Jianghui Ji

More than 700 S-type planets have been identified from Gaia and TESS observations, including over 150 transiting targets, enabling the precise dynamical orbits and planetary mass characterization in binary environments. Here we present the first systematic N-body dynamical mass determination for 40 single S-type (Satellite-type orbit) planets in close binaries using an improved Markov Chain Monte Carlo (MCMC) framework with Gaussian priors to model stellar companion perturbations. {For binary systems with $a_\mathrm{B}<100$ au, companion-induced perturbations can bias the RV semi-amplitude and consequently the inferred planetary masses. The impact is strongest for short-period sub-Jovian planets, whose masses decrease by up to 20% when transitioning from Keplerian to N-body modeling, while massive Jovian planets with $M_{\mathrm{Jup}} < M_{\mathrm{p}} < 5$ $M_{\mathrm{Jup}}$ show only a 7.2% reduction.} Applying the NAFF stability criterion to TOI-4633, $i_{\mathrm{mut}} = 70^{\circ}$ is the upper limit for the fast rejection of unstable orbital solutions. Our results reveal that intermediate-mass planets exhibit both positive or negative biases in the inferred masses and influence the observed population of the sub-Jovian desert.
Read the full abstract

High Energy Astrophysical Phenomena

Evidence for an accretion-driven subpopulation of black holes in GWTC-5.0

Zacharias Roupas

We report Bayesian evidence for a subpopulation of black holes, grown via accretion during the gaseous birth-stage of star clusters, in the cumulative GWTC-5.0 released by the LIGO-Virgo-KAGRA collaboration. This accretion channel predicts a saturating spin–mass relation, with low spins at low masses, rising continuously with mass through all intermediate spin values, to high spins at high masses. We test this prediction directly against the component spins of the catalogue. We single out 10 events with positive support and many others with weaker support across the whole component-mass range of the catalogue. We identify a preferred mass scale $m^t=20.7^{+11.6}_{-1.2}\,M_\odot$ (90% credibility) separating regimes with different accretion-mixture fractions, with $\ln B=5.5$. Above this inferred scale, the evidence for an accretion-driven subpopulation is strongly concentrated, reaching a natural log Bayes factor of $16.6$ against the LVK fiducial spin population.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Primordial black holes and induced gravitational waves from localized features in DBI inflation

Narges Rashidi

We investigate primordial black hole formation in a Dirac-Born-Infeld inflationary framework in which the background dynamics are determined by explicit functional forms of the inflaton potential $V(\phi)$ and the warp factor $f(\phi)$. The background equations are solved numerically to obtain the evolution of the slow-roll parameters. We show that a localized feature in the potential, accompanied by a correlated structure in the warp factor, dynamically induces a transient suppression of the slow-roll parameter, leading to a short-lived non-attractor phase. This behavior generates an enhancement of the curvature power spectrum on small scales, while preserving consistency with CMB-scale observables. The Mukhanov-Sasaki equation is then solved numerically to compute the resulting power spectrum, which exhibits narrow and localized peaks in the PBH abundance across different mass ranges. We also evaluate the associated stochastic background of induced gravitational waves and find that the predicted signal can fall within the sensitivity bands of future pulsar timing arrays and space-based interferometers, depending on the scale of the inflationary feature. A parameter scan in the $(r,n_s)$ plane shows that the large-scale predictions remain consistent with current observational constraints.
Read the full abstract

Instrumentation and Methods for Astrophysics

First overnight balloon flight of the GRAINE 2023 emulsion gamma-ray telescope enabled by a large-scale pressure-vessel gondola

Hiroki Rokujo, Shigeki Aoki, Takashi Azuma et al. (+34 more)

The Gamma-Ray Astro Imager with Nuclear Emulsion (GRAINE) project conducts precision observations of sub-GeV–GeV cosmic gamma rays using a balloon-borne nuclear-emulsion telescope with high angular resolution. In GRAINE 2023, a 2.5-m$^{2}$ telescope was flown in the project's first overnight balloon flight, including observation periods for the Vela pulsar and Galactic center region. To operate the telescope under the low-pressure and low-temperature stratospheric environment, the balloon-style pressure-vessel concept was scaled up to a lightweight gondola with an internal length of 4.9 m. A new aluminum-alloy ring structure and a lightweight membranous-shell material, SHL-300MDL, were developed. While the telescope aperture was increased by a factor of 6.6 over GRAINE 2018, the pressure-vessel gondola mass was limited to 179 kg. Ground tests of the completed flight assembly demonstrated a differential pressure above 100 hPa at room temperature and at a mean temperature of $-66.0^{\circ}$C. The payload was launched from Alice Springs, Australia, in April 2023 and achieved a total flight duration of approximately 27 h, including 24.3 h of level flight. Although the upper membranous shell reached approximately $-60^{\circ}$C at night, the vessel internal pressure remained above the required 100 hPa throughout level flight. These results demonstrate that the developed gondola can accommodate a 2.5-m$^{2}$ emulsion gamma-ray telescope and maintain the required pressure during overnight stratospheric flight. Scientific analyses of astrophysical and atmospheric gamma rays, including dedicated analysis of the Galactic center region, are ongoing using the recovered emulsion data. This development provides a technical basis for repeated observations with future large-area GRAINE telescopes.
Read the full abstract

All authors Hiroki Rokujo, Shigeki Aoki, Takashi Azuma, Hirotaka Hayashi, Yudai Isayama, Atsushi Iyono, Takumi Kato, Tsuyoshi Kawahara, Koichi Kodama, Ryosuke Komatani, Masahiro Komatsu, Masahiro Komiyama, Hideyuki Minami, Kunihiro Morishima, Fumiya Murakami, Shogo Nagahara, Naotaka Naganawa, Mitsuhiro Nakamura, Tomoaki Nakamura, Yuya Nakamura, Noboru Nakano, Toshiyuki Nakano, Kazuma Nakazawa, Miyuki Oda, Kazuhiro Okamoto, Osamu Sato, Kai Shimizu, Amon Suganami, Yuki Sugi, Kou Sugimura, Satoru Takahashi, Ikuya Usuda, Saya Yamamoto, Jun Yamashita, Mayu Yamashita, Shoma Yoneno, Masahiro Yoshimoto

Astrophysics of Galaxies

Can Little Red Dots Contribute To The Early Universe Cosmic Dust Budget?

Chris Ashall, Rohan P. Naidu, Alberto Torralba et al. (+11 more)

The origin of dust in the early Universe remains uncertain. We explore whether Little Red Dots (LRDs) could provide a high-redshift dust-production channel. Motivated by an analogy with Type IIn supernovae, we investigate whether LRDs may share the efficient dust-forming conditions. We consider dust formation in outer winds and later in a shielded cold dense shell after the central source fades. Such dust may avoid a global remnant-phase reverse shock, while longer LRD lifetimes may promote grain growth. We model the SEDs of two low-redshift LRD analogs as a thermal pseudo-photosphere plus optically thin dust components, obtaining dust reservoirs of order $10^{2}$-$10^{3}\,M_{\odot}$. Although photometry cannot exclude pre-existing dust, the narrow Balmer components of both analogs are close to the Case B ratio and their narrow-line environments are metal-poor, disfavoring a dominant diffuse host-ISM origin for the inferred reservoir. Formation within the LRD outflow is consistent with our optical-depth, sublimation, and energy-balance checks. In this scenario, the large dust masses do not produce a strong optical attenuation because a clumpy or asymmetric distribution can leave the dominant optical sightlines relatively unobscured. Our population calculation shows that the LRD contribution to early-Universe dust production can range from negligible to dominant. At higher efficiencies, LRDs can approach or exceed the lower CCSN contribution above $z\approx5$, whereas less favorable assumptions yield a minor contribution. We therefore propose that LRDs can act as early-Universe dust factories and, under some conditions, may dominate over CCSNe or provide seed grains for subsequent growth in the early ISM.
Read the full abstract

All authors Chris Ashall, Rohan P. Naidu, Alberto Torralba, Irene Shivaei, John Chisholm, Hanpu Liu, Zhaoran Liu, Jorryt Matthee, Kyle Medler, Tyco Mera, Takashi J. Moriya, Devesh Nandal, Robert A. Simcoe, Wendy Q. Sun

Astrophysics of Galaxies

Estimation of Dust Mass from Infrared Emission and Extinction of Supernova Remnants: G93.7-0.2, G109.1-1.0, G156.2+5.7, and G166.0+4.3

Zhe Zhang, Jun Li, Biwei Jiang et al. (+1 more)

Supernova remnants (SNRs) are major sites for both the production and destruction of interstellar dust, and quantifying their dust budget is essential for understanding the life cycle of cosmic dust. In this work, the dust masses of four Galactic SNRs (G93.7$-$0.2, G109.1$-$1.0, G156.2+5.7, and G166.0+4.3) are estimated using two complementary methods: the three-dimensional (3D) interstellar extinction map and infrared (IR) spectral energy distribution (SED) fitting based on photometry from WISE, IRAS, AKARI, and Planck. The extinction masses, derived from the differential extinction within each SNR's distance interval, are 108.3, 82.0, 48.8, and 119.2 $M_\odot$, respectively. A two-component (“warm + cold") modified blackbody fitting yields warm dust temperatures of 43–74\,K and cold dust temperatures of 13–16\,K, with the cold dust component dominating the total IR-emission mass ($\sim$90–400 $M_\odot$). The extinction masses and IR emission masses show systematic differences, likely caused by sightline contamination from unrelated foreground/background material and uncertainties in dust temperatures and opacities.
Read the full abstract

All authors Zhe Zhang, Jun Li, Biwei Jiang, He Zhao

High Energy Astrophysical Phenomena

Little Red Dots as Shock-Powered High-Energy Neutrino Sources

Tyco Mera, Chris Ashall, Shunsaku Horiuchi et al. (+3 more)

Little Red Dots (LRDs) are compact, high-redshift sources whose physical nature remains uncertain. Their optical spectra bear many similarities to Type IIn supernovae (SNe IIn), motivating a scenario in which their emission is powered by shocks interacting with dense surrounding material. We investigate whether such interactions can power LRDs and contribute to the diffuse high-energy neutrino intensity measured by IceCube. In our simplified model, a fast central-engine outflow drives a shock through dense surrounding material before stalling near the LRD photosphere, while some material continues to flow through the shock. We explore parameter ranges motivated by SNe IIn and the observed and inferred properties of LRDs, finding solutions with shock luminosities from 2.2e43 to 3.5e44 erg/s. Using an analytical framework for cosmic-ray acceleration and hadronic interactions in dense shock environments, we calculate the resulting high-energy neutrino emission and integrate it over the cosmological LRD population. For our fiducial SNe IIn-based cosmic-ray parameters, the average predicted contribution below 2e5 GeV increases from about 0.2% for the lowest-luminosity quintile to about 2% for the highest-luminosity quintile, while an illustrative higher-efficiency case reaches about 13% of the IceCube diffuse neutrino intensity. The incompleteness of the current LRD census and uncertainties in their physical nature limit constraints on the cosmic-ray parameters and the distribution of L_s. Larger LRD samples, together with improved physical models and a full population-synthesis study, will be required to constrain the total LRD contribution to the diffuse neutrino background.
Read the full abstract

All authors Tyco Mera, Chris Ashall, Shunsaku Horiuchi, Rohan Naidu, Kyle Medler, Peter Hoeflich

Friday 28 August

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

A Unified Treatment of the Self-Force Problem

Beka Modrekiladze, Ira Z. Rothstein and Jordan Wilson-Gerow

This paper introduces formalism, based on worldline effective field theory, which allows one to systematically calculate the gravitational self-force on a compact object immersed in an environment with non-vanishing stress energy. Using the closed time path integral we present a universal effective action that can be used to calculate the equations of motion of a compact object due to its interaction with the environment to any order in the relevant expansion parameters, the relative importance of which depends upon the choice of environment. We show that the leading order equations of motion can be universally written in terms of the retarded two-point function of the stress-energy tensor for the environment. The resulting action can be used to calculate both dissipative (dynamical friction) and conservative forces in a completely relativistic fashion. We demonstrate the utility of the result by calculating the dissipative force due to dust, an inviscid fluid, and a coherent field. Our results agree with those previously derived in the literature. We furthermore show that the famous “Coulomb Log" found by Chandrasekhar should be interpreted as a renormalization group log due to a UV divergence that renormalizes the dissipative part of the in-in action. We then prove that this log is universal in the Newtonian limit in that its value is universal, for a generic class of environments and trajectories. This log is the leading log in an RG flow in the dissipative action that has yet to be explored.
Read the full abstract

Instrumentation and Methods for Astrophysics

Lynx2030 Science Analysis Group: Final Report

Lynx2030 Science Analysis Group: Simon R. Bandler, Laura W. Brenneman, Nico Cappelluti et al. (+50 more)

The Lynx2030 Science Analysis Group (SAG) was convened to reassess the scientific goals and technical drivers of the Lynx mission concept amid a rapidly evolving astrophysics landscape. Building on the original Lynx Concept Study, the SAG examined how recent discoveries, emerging facilities, and advances in instrumentation influence the scientific opportunities for a next-generation flagship X-ray observatory. Through focused working groups, the SAG investigated the scientific impact of enhanced capabilities: (i) improved angular resolution, (ii) broader bandpass coverage, (iii) an enhanced microcalorimeter, (iv) new capabilities and observing modes, and (v) larger fields of view. Across a broad range of topics, from the formation of the first black holes and the evolution of galaxies to the baryon cycle, compact objects, stellar explosions, multi-messenger astrophysics, and the dynamic high-energy Universe, the SAG finds that the scientific motivation for a Lynx-class observatory remains compelling and, in many areas, has significantly strengthened over the past decade, prominently through JWST's discovery of the "Little Red Dots", likely massive accreting black holes in infant galaxies whose nature is fundamentally an X-ray question. This report shows that modest extensions beyond the original Lynx design reference mission can unlock transformative science while preserving the observatory's core architecture. Powerful current and future facilities such as Roman, Rubin, JWST, SKA, ngVLA, LISA, and NewAthena highlight the unique role a high-angular-resolution, high-throughput X-ray observatory would play in the multi-wavelength and multi-messenger ecosystem of the 2030s and beyond. The findings of the Lynx2030 SAG confirm Lynx's central vision: an unprecedented view of the hot and energetic Universe, enabling discoveries that will define high-energy astrophysics in the coming decades.
Read the full abstract

All authors Lynx2030 Science Analysis Group: Simon R. Bandler, Laura W. Brenneman, Nico Cappelluti, Daniel Castro, Steven R. Ehlert, W. Peter Maksym, Fabio Pacucci, Scott W. Randall, Grant R. Tremblay, John ZuHone, Steven W. Allen, Antara R. Basu-Zych, Akos Bogdan, Joel N. Bregman, Tamta Burduli, Thomas Connor, Sanskriti Das, Casey DeRoo, Stephen DiKerby, Paul A. Draghis, Martin Elvis, Giuseppina Fabbiano, Ralf K. Heilmann, Jimmy A. Irwin, Amruta Jaodand, Margarita Karovska, Vinay L. Kashyap, Anthony A. Kerr, Caroline Kilbourne, Ralph Kraft, Jiangtao Li, Labani Mallick, Herman L. Marshall, Michael L. McCollough, Anna Ogorzałek, Frederik Paerels, Daniel Patnaude, Paul Plucinsky, David Pooley, Frederick S. Porter, Daniele Rogantini, Roger Romani, Helen R. Russell, Kazuhiro Sakai, Mark Schattenburg, Dan A. Schwartz, Malgorzata Sobolewska, Paolo Soffitta, Alexey Vikhlinin, Daniel R. Wilkins, Scott Wolk, Ka-Wah Wong, Irina Zhuravleva

High Energy Astrophysical Phenomena

Anomalous horizontal track-like events at the HAWC observatory: candidate neutrino-induced charged leptons from the Pico de Orizaba volcano

Hermes León Vargas and Andrés Sandoval

Two track-like events with exceptionally large charge deposits, pointing back to the region of maximum overburden ($>18$ km.w.e.) of the Pico de Orizaba volcano, were reported by the HAWC Collaboration in a search for Earth-skimming neutrinos. Using exclusively published information, including the published Monte Carlo charge distributions and the scattered-muon background model, we show that these events are kinematically inconsistent with all identified backgrounds. A conservative energy-conservation bound places the in-tank energy deposit of the candidates above $\approx$190–210~GeV, with a worst-case minimum of 122–136~GeV, in either case exceeding the 100~GeV maximum of the scattered-muon background model. Calibration systematics derived from the published simulations act unidirectionally, pushing the implied deposits into the multi-TeV regime. Direct atmospheric muons require $E_\mu \gtrsim 0.67$~PeV to penetrate the overburden and contribute $4.5\times10^{-5}$ expected events ($\lesssim 10^{-3}$ under the largest possible prompt-charm flux); collinear muon bundles are excluded by five independent arguments. Conversely, the neutrino hypothesis predicts identifiable events precisely in the observed charge window ($10^{3}$–$10^{4}$ photoelectrons) and in the highest-overburden analysis region, both observed. The two track-like events imply a rate that exceeds the conventional atmospheric neutrino flux expectation at the 2.1–2.5$\sigma$ level. The charges of the observed candidates require an emerging lepton above about 20~TeV; the published calibration does not bound the energy from above. These would constitute the first neutrino candidates detected in Mexico and the first obtained with the Earth-skimming volcano technique.
Read the full abstract

High Energy Astrophysical Phenomena

A Self-Sustaining Black Hole Engine Powered by the Tidal Disruptions of Stars

James Guillochon and Avi Loeb

Tidal disruption events (TDEs) strongly prefer host galaxies undergoing, or recovering from, a burst of star formation, implying that a rare minority of galaxy types produces most events. The required per-galaxy rates, as high as $10^{-2}$ gal$^{-1}$ yr$^{-1}$, are hard to achieve through stellar relaxation alone. Molecular clouds surrounding nuclear clusters help set the relaxation rate, offering a path to higher rates. We show that (post-)starburst galaxies, whose nearby prototypes contain large molecular gas reservoirs, are likely in a self-sustaining cycle: an enhanced disruption rate compresses the surrounding clouds through momentum injected by the unbound debris, the denser clouds compress the cluster, and the cluster disrupts stars faster still. The runaway is arrested only when stars begin to collide. Solving for the steady state, the rate saturates at $1.4\times10^{-2}(M_{\rm h}/10^{6}M_\odot)^{-0.84}$ yr$^{-1}$, two orders of magnitude above the canonical rate at $10^{6}M_\odot$, with a normalization uncertain by a further two orders of magnitude through the stellar collision rate. Three independent requirements — that tidal debris outweigh AGN feedback, that the molecular clouds fit within the disk that holds them, and that the cusp be no denser than observed nuclei — bound the flattening of the stellar cusp to $0.18 \lesssim f_\ast \lesssim 0.25$. Because no engine can run below a threshold black hole mass, holes seeded beneath it stay dark until accretion carries them across, switching on after $\sim 1$ Gyr and offering a natural explanation for the late peak recently measured in the TDE delay time distribution. The nucleus is buried under $A_V \simeq 50$ whatever its geometry, so most such disruptions should be hidden from optical surveys and emerge instead in the infrared.
Read the full abstract

Earth and Planetary Astrophysics

Magnitude of stable iron isotope fractionation limited by multiple stages of terrestrial core formation

Gabriel Nathan and Seth A. Jacobson

One proposed mechanism for generating iron isotopic differences between planetary mantles and chondrites is metal-silicate equilibration during terrestrial core formation. Prior studies of this isotopic fractionation effect employ single-stage core formation models that are inconsistent with reproducing the siderophile element budget of the Earth's mantle. Here, we model iron isotopic evolution of the Earth's mantle in a multistage core formation scenario that is consistent with dynamic models of planet formation and reproduces the geochemistry of the bulk silicate Earth, specifically the refractory moderately siderophile elements. We find that multiple stages of core formation rebalance the fractionating effect of metal-silicate equilibration for the iron isotopic system, comparable to or smaller than typical analytical uncertainties in mantle rocks. Ultimately, this rebalancing effect - coupled with stochastic accretion and differentiation histories which further complicate planetary formation processes - makes it unlikely that isotopic fractionation during metal-silicate equilibration is the primary mechanism responsible for the iron isotopic composition of the Earth's mantle.
Read the full abstract

Instrumentation and Methods for Astrophysics

Pre-shipment optical characterization of the SCALES instrument

Isabel J. Kain, Reni Kupke, Daren Dillon et al. (+31 more)

The Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy (SCALES) instrument is a 1-5 micron imager and 2-5 micron integral field spectrograph, currently being commissioned on the Keck II Telescope. SCALES is optimized for exoplanet high-contrast imaging and spectroscopic characterization, and will be sensitive to older, colder exoplanets than existing instrumentation. The 12.3" x 12.3" imaging channel is designed to replicate the capabilities of NIRC2, and the low (R~35-200, 2.2" x 2.2" FOV) and medium (R~2500-5000, 0.36" x 0.34" FOV) spectral resolution modes offer new capabilities compared to existing Keck instrumentation. We present preliminary optical performance results from laboratory testing and commissioning of SCALES.
Read the full abstract

All authors Isabel J. Kain, Reni Kupke, Daren Dillon, R. Deno Stelter, Rosalie McGurk, Gwendolin Weber-Stover, Athira Unni, Marc Kassis, Scott Lilley, Peyton Benac, Mackenzie Lach, Arun Surya, Amirul Hasan, Ravinder Banyal, Raquel Martinez, Nicholas MacDonald, Will Deich, Aaron Hunter, Emily Plume, Michael Gonzales, Cristian Rodriguez, Arjun Kumar, Cyril Bourgenot, Paul Whiteg, Juergen Schmollg, James Wells, Spencer Davies, David Bramall, Dimitri Mawet, Olivier Absil, Michael Fitzgerald, Eric Wang, Steph Sallum, Andrew Skemer

High Energy Astrophysical Phenomena

A Terrestrial Gamma-ray Flash with an Asymmetric Footprint Observed at the Pierre Auger Observatory

The Pierre Auger Collaboration, John Ortberg, David M. Smith et al. (+1 more)

The Pierre Auger Observatory, a $3000km^2$ detector array that sits 1400m above sea level in Argentina, has the ability to map the entire footprint of Terrestrial Gamma-ray Flashes (TGFs), which are short, intense bursts of gamma rays associated with lightning. This is in contrast to the vast majority of TGF detections that only occur in a single detector in space. In this paper we leverage this capability to perform two important analyses on an event from 2007, chosen for its large footprint and high signal quality. First, we triangulate the source of the TGF to $2.3\pm0.5$km height above ground level using the arrival time of the gamma rays themselves at the detector array, independently of any information regarding the lightning channel. With the source position established, we can analyze the spatial distribution of the TGF on the ground with respect to that source. Not only do we find that one side of the TGF footprint shows an order of magnitude higher flux than the other, but we also find an asymmetric azimuthal structure consisting of two clear peaks in intensity. These peaks are offset by about $120^o$ from each other. This azimuthal structure is not possible under the traditional uniform electric-field model of a TGF. Using Geant4 simulations of collimated beams of the relativistic runaway electron-avalanche spectrum, we attempt to reconstruct the source geometry of the TGF and find that it likely had significant components in the $\theta > 75^o$ range, where $\theta$ is the off-nadir angle.
Read the full abstract

All authors The Pierre Auger Collaboration, John Ortberg, David M. Smith, Joseph Dwyer

High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Strongly coupled quark matter in neutron stars and their mergers

Konstantin Maslov, Ralf Rapp, Joaquin Grefa et al. (+2 more)

The discovery of the strongly-coupled quark-gluon plasma (sQGP) in high-energy heavy-ion collisions has revealed remarkable properties of matter at high temperature, with transport coefficients close to conjectured bounds from quantum field theory at strong coupling. The high sQGP collision rates imply very large energy uncertainties and the melting of quasiparticle structures. Deploying quantum many-body theory based on the self-consistent $T$-matrix approach for the sQGP at high temperature, we investigate its manifestation at high baryon density and low temperature, as present in neutron stars and their mergers. We constrain the chemical-potential dependence of the quark interaction kernel using first-principles information from Quantum Chromodynamics on baryon-number susceptibilities. Very large collisional widths persist at large density and are found to relegate superconducting phases to rather small temperatures. Instead, a strongly coupled diquark liquid prevails in the thermodynamics under the conditions relevant to neutron-star mergers. At lower densities, the diquarks take over from the single-quark contributions, suggesting a pathway toward hadronization. Our results are consistent with observational constraints on the equation of state of neutron stars, corroborating the presence of strongly coupled quark matter in the interior of these objects.
Read the full abstract

All authors Konstantin Maslov, Ralf Rapp, Joaquin Grefa, Veronica Dexheimer, Claudia Ratti

Solar and Stellar Astrophysics

Statistical Energy Budget of the Solar Wind with Parker Solar Probe and Solar Orbiter : 1 - Unbalanced Total Energy Radial Evolution

Jean-Baptiste Dakeyo, Pascal Démoulin, Victor Réville et al. (+9 more)

The magneto-hydrodynamic (MHD) description of the solar wind has long been regarded as one of the most successful frameworks for investigating solar wind heating and acceleration. Under a set of simplifying assumptions, it provides a reduced large-scale description that is widely used to study the energetic role of electromagnetic fluctuations in the solar wind energy budget. In practice, applying simplification to MHD can result in the loss of some physics compared to an exact set of equations. However, an observational energy budget can help us to verify whether any energetic information has been lost in the process of simplification. To do so, we directly test the validity of the large-scale non-linear ideal MHD energy budget with solar wind observations from Parker Solar Probe (PSP) and Solar Orbiter (SO). After verifying the reliability of the measurements through comparison with previous studies of similar solar wind properties, we test the conservation of the total energy predicted by the MHD theory. We find that the average total energy increases with radial distance by $56\%$ ($\pm9\%$) between 14 and 203 solar radii. The increase in kinetic energy is not sufficiently compensated by the decrease of the thermal and electromagnetic contributions. We investigate the major sources of observational uncertainty and find that they cannot account for the observed energy increase. These results suggest that the large-scale theoretical description may neglect an energetically significant contribution to solar wind acceleration. Assuming that such a contribution exists, we predict that this extra energy would scale with radial distance as $r^{-0.54\pm0.38}$.
Read the full abstract

All authors Jean-Baptiste Dakeyo, Pascal Démoulin, Victor Réville, Stuart Bale, Tamar Ervin, Milan Maksimovic, Olga Alexandrova, Mingzhe Liu, Roberto Livi, Nikos Sioulas, Orlando Romeo, Alexis Rouillard

Instrumentation and Methods for Astrophysics

96 kHz on-sky imaging on an adaptive optics system with a single-photon avalanche diode

Theodore A. Grosson, Maaike A. M. van Kooten, Kathryn Jackson et al. (+2 more)

Astronomical observations requiring extremely high angular resolution necessitate advanced adaptive optics (AO) systems to overcome blurring caused by the atmosphere. In addition to obtaining much sharper point-spread functions (PSFs) with these systems, it is beneficial to be able to characterize the behaviour of the resulting PSF across time and wavelength. We have installed a commercially-available Single-photon avalanche diode (SPAD) array on the focal plane of the REVOLT AO testbench at the Dominion Astrophysical Observatory, allowing us to observe the visible PSF of the system at rates up to 96 kHz. This provides a time-resolved view of the PSF at $\sim$100 times the frequency of the AO system itself. We use this detector to analyze the high-frequency behaviour of the PSF of the AO system, including residual tip/tilt and deformable mirror response. We also explore the performance of AO-assisted lucky imaging, in which we average together only the frames which result in the best image quality. We find that high-framerate imaging can significantly improve the PSF beyond the native capabilities of the AO system.
Read the full abstract

All authors Theodore A. Grosson, Maaike A. M. van Kooten, Kathryn Jackson, Jean-Pierre Veran, Simon Carrier

Instrumentation and Methods for Astrophysics

Exploring the trade-space of distributed aperture telescopes for faint-object spectroscopy

Theodore A. Grosson, Deborah M. Lokhorst and Alan W. McConnachie

Scientific programs targeting the faintest objects push modern telescopes to increasingly large sizes, high costs and complex designs. Obtaining spectra of low surface brightness galaxies, for example, requires hours of observations on state-of-the art instruments. Increasing telescope diameters beyond 40 m raises potentially insurmountable challenges for design and funding. An innovative strategy for combating these costs is to use many small telescopes in place of a single large aperture. For observations in which high angular resolution is not necessary, this can be equivalent to a large diameter telescope in terms of sensitivity, while diffraction limited by the individual aperture. Improvements in commercial off-the-shelf (COTS) components have made this concept a possibility, as demonstrated by instruments such as the Dragonfly Telephoto Array, the Huntsman Telescope, and the Argus Array. In this work, we discuss the merits of "distributed aperture telescopes" as applied to the use case of spectroscopic observations of ultra-diffuse galaxies (UDGs). We compare the cost and simulated scientific performance of different configurations of apertures, detectors, and other components for this purpose, finding that an array of half-metre telescopes can obtain comparable observations to large telescopes for a fraction of the cost. Finally, we discuss the path to prototyping an array which will enable a spectroscopic survey of UDGs.
Read the full abstract

Solar and Stellar Astrophysics

The Hot, Continuum-compact State of the Yellow Hypergiant V509 Cassiopeiae: CHARA Diameters, CO-band Angular-extension Constraints, and Companion Limits

Narsireddy Anugu, Gail H. Schaefer, Douglas R. Gies et al. (+4 more)

Yellow hypergiants are rare, evolved massive stars generally interpreted as post-red-supergiant objects evolving blueward through or near the dynamically unstable Yellow Evolutionary Void. V509~Cassiopeiae is a remarkable example: its spectroscopically inferred effective temperature increased from approximately 5000~K in the mid-1980s to about 7900~K by the late 1990s and has since remained near this value during its post-heating state. We use simultaneous six-telescope CHARA observations obtained in 2023 with MIRC-X in the $H$ band and MYSTIC in the $K$ band to measure its photospheric diameter, search for a luminous companion, and constrain any spatially extended CO atmosphere. Interferometric data fitting with fixed atmosphere-model center-to-limb variation profiles yield limb-darkened angular diameters of $1.1840$–$1.1950$~mas. Although nominally about 5% smaller than the previous Palomar Testbed Interferometer measurement, the difference is only $1.8\sigma$, indicating no significant secular change over 17–21~yr. The closure phases are consistent with a centrosymmetric brightness distribution, and no near-infrared-bright companion is detected over the sampled separations. The median $3\sigma$ limits are $\Delta H=5.28$~mag and $\Delta K=6.48$~mag. The B1~V companion proposed from ultraviolet spectroscopy is expected to lie below these limits and is not excluded. The CO first-overtone channels give a weighted mean CO-to-continuum diameter ratio of $1.011\pm0.004$, below the adopted $3\sigma$ detection criterion. We find no significant CO-band angular extension. V509~Cas is thus hot and molecularly compact despite retaining spectroscopically visible atomic circumstellar gas.
Read the full abstract

All authors Narsireddy Anugu, Gail H. Schaefer, Douglas R. Gies, Anni Kasikov, John D. Monnier, Stefan Kraus, Karolina Kubiak

Earth and Planetary Astrophysics · Cross-listed from q-bio.OT

Geochemical Hazard Assessment of Martian Regolith for Future Human Exploration

Mavia Anjum and Gwendolyn D. Bart

As human missions to Mars move from concept to planning to reality, a systematic quantitative health risk assessment of martian regolith exposure has become critically important. This study presents a comprehensive multi-element, multi-pathway health hazard analysis of martian regolith for a 70 kg adult astronaut on an 18-month surface mission, using bulk silicate Mars geochemical data and Earth Upper Continental Crust reference values as baseline comparators. We computed Average Daily Dose, Hazard Quotient, Hazard Index, Enrichment Factor, Ecological Risk Factor, and Incremental Lifetime Cancer Risk across all three exposure pathways (oral ingestion, inhalation, and dermal contact) for toxic and heavy metals, under four filtration scenarios (0%, 25%, 50%, 95%). Results demonstrate that Cr and Co represent the most critical non-carcinogenic hazards, exceeding the regulatory threshold (HI > 1) even at 50% filtration, while Cr also poses the most significant carcinogenic risk, near the $10^{-4}$ regulatory threshold level. At least 92% regolith filtration efficiency is required to reduce Cr to acceptable non-cancer hazard levels. Nickel exceeds the acceptable cancer risk threshold of $10^{-6}$ at all filtration levels below 95%. No element other than Cr and Co exceeds HI = 1 in the unfiltered scenario, although Fe, Ni and Mn approach concerning levels. These results establish that a minimum 95% High-Efficiency Particulate Air (HEPA)-grade filtration efficiency combined with active chemical sorption is required for acceptable Cr and Co short term exposure and Cr, Ni long term exposure management. This study provides a pathway-specific quantitative risk framework applicable to habitat air quality standards and EVA suit specifications for Mars surface operations
Read the full abstract

Instrumentation and Methods for Astrophysics

X-ray grating spectroscopy as a mission enhancement

Hans Moritz Guenther, Ehud Behar, Joel N. Bregman et al. (+27 more)

We propose to add instruments to any potential future X-ray mission with focussing optics that is considered in NASA's ASTRA framework. Such an instrument is a necessity to study AGN wind outflows and feedback, find the missing baryons, study the intergalactic medium, and analyze abundances and chemical bonds in dust grains throughout the Milky Way. We conclude that those science goals can be achieved with a spectral resolving power > 3000 in the soft X-ray band (about 10-40 Ang) and an effective area a few times larger than current instruments. We describe a possible mission implementation for a soft X-ray grating spectrometer that can be folded in and out or be mounted permanently in the beam. Such an instrument can reach the requirements for a wide variety of host mission properties. A small UV imager and a UV spectrograph can be mounted on the same platform with independent optics. These added instruments vastly enhance the science capabilities of the host mission for a modest cost (100-200 million $) and with weight and power needs that can be easily accommodated in any major mission.
Read the full abstract

All authors Hans Moritz Guenther, Ehud Behar, Joel N. Bregman, Laura W. Brenneman, Alexander R. Bruccoleri, Lía Corrales, Elisa Costantini, Thomas Dauser, Casey T. DeRoo, Abraham D. Falcone, Adam R. Foster, Luigi Gallo, Catherine E. Grant, Sean J. Gunderson, Ralf K. Heilmann, David P. Huenemoerder, Maurice Leutenegger, Eric D. Miller, Michael Nowak, Frits Paerels, David A. Principe, Ioanna Psaradaki, Andrew Ptak, Agata Rozanska, Randall K. Smith, Pasquale Temi, Todd M. Tripp, Lynne Valencic, Joern Wilms, Scott J. Wolk

Cosmology and Nongalactic Astrophysics

Reconstructing stochastic gravitational-wave signals from flavour deconstruction with LISA

Noemi Fabri, Raphael Bertrand-Delgado, Danny Laghi et al. (+1 more)

We investigate the reconstruction of a stochastic gravitational-wave background generated by a first-order phase transition in flavour-deconstruction models using the Laser Interferometer Space Antenna (LISA). In these scenarios, the spontaneous breaking of an extended flavour-non-universal gauge symmetry at the TeV scale can both generate the observed hierarchies of Standard Model fermion masses and mixing angles and induce a strong first-order phase transition. We consider representative benchmark points of the model, compute the corresponding thermodynamic transition parameters, and construct the resulting gravitational-wave spectra using a state-of-the-art sound-wave template. We then inject these spectra into simulated LISA data and perform Bayesian inference with SGWBinner, jointly reconstructing the cosmological signal, instrumental noise, and astrophysical foregrounds. We find that the strongest benchmark signal can be successfully reconstructed, whereas weaker signals are substantially degenerate with the unresolved extragalactic compact-binary foreground. We further show that tighter prior information on this foreground, motivated by observations with ground-based detectors, can reduce this degeneracy and improve signal reconstruction. Our results demonstrate that flavour-deconstruction models can produce signals accessible to LISA, while highlighting the importance of astrophysical-foreground modelling for their identification and characterization.
Read the full abstract

All authors Noemi Fabri, Raphael Bertrand-Delgado, Danny Laghi, Lucio Mayer

Earth and Planetary Astrophysics

Probing the Taxonomic Diversity of the Small Near-Earth Object Population

Andy J. López-Oquendo, David E. Trilling, Michael Mommert et al. (+1 more)

Small near-Earth objects (NEOs) represent the immediate source population of meteors and meteorites and provide a direct window into the compositional and dynamical evolution of the inner Solar System. However, their small sizes, rapid rotation rates, and short observability windows have historically limited systematic compositional characterization. We present results from a multi-year rapid-response near-infrared spectrophotometric survey of recently discovered NEOs conducted with the UKIRT-WFCAM instrument between 2016 and 2024. Our campaign obtained 371 observation sequences, yielding reliable color measurements and probabilistic taxonomic classifications for 122 NEOs, with diameters ranging from 5 m to 150 m and a median size of 60 m. We employed lightcurve-corrected Z, J, H, and K photometry and a machine-learning-based classification framework to derive both observed and debiased taxonomic distributions as a function of object size. The observed taxonomic fractions show a population of small NEOs dominated by S-complex and CX-complex objects in nearly equal proportions. After accounting for observational selection biases, however, the inferred intrinsic population is instead dominated by dark, carbonaceous (CX-complex) bodies, with important implications for the intrinsic composition of the small NEO population. We further explore the relationship between small NEOs, meteorite fall statistics, and atmospheric filtering effects, finding that a substantial fraction of carbonaceous material likely does not survive atmospheric entry. These results highlight the importance of debiased surveys of small NEOs for interpreting the meteorite record, refining delivery models from the main belt, and informing the selection of future mission targets and planetary defense strategies.
Read the full abstract

All authors Andy J. López-Oquendo, David E. Trilling, Michael Mommert, Michaël Marsset