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Physics Astrophysics

astro-ph Watch Astrophysics

Sunday 9 August

High Energy Astrophysical Phenomena

Slow Cosmic-Ray Diffusion in Supersonic and Super-Alfvénic Turbulence

Yue Hu

Extended TeV-PeV gamma-ray halo observations imply cosmic-ray (CR) diffusion that is both substantially slower than the Galactic mean and only weakly anisotropic, despite the presence of a large-scale Galactic magnetic field. We investigate whether such transport can arise in partially ionized source environments, where ion-neutral damping removes the small-scale fluctuations responsible for gyroresonant scattering. Using two-fluid magnetohydrodynamic turbulence simulations with relativistic test-particle tracking, we find that damping increases the parallel diffusion coefficient by approximately two orders of magnitude in trans-sonic turbulence, thereby strongly enhancing field-aligned transport. In supersonic turbulence, shock-associated magnetic fluctuations survive the damping and sustain non-resonant pitch-angle scattering, limiting the increase in parallel diffusion to a factor of a few to ten. At high Alfvénic Mach numbers, $M_A\gtrsim5$, the magnetic-field direction decorrelates over the Alfvén scale, driving parallel diffusion coefficient $D_\parallel$ and perpendicular diffusion coefficient $D_\perp$ toward equality. For $M_s\simeq10$, $M_A\simeq5$-$10$, and representative parameters for hundred-TeV gamma-ray source environments, we obtain comparable $D_\parallel$ and $D_\perp$, within the observationally inferred range of $\sim10^{27}$-$10^{28}\,\mathrm{cm^2\,s^{-1}}$. These results show that strongly supersonic, highly super-Alfvénic turbulence in source environments can sustain slow, nearly isotropic CR transport even when the ion-neutral damping effect is important.
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High Energy Astrophysical Phenomena

Plasmoid-Mediated 2D Magnetic Reconnection in Partially Ionized Plasmas

Yue Hu, Siyao Xu, Grzegorz Kowal et al. (+3 more)

Magnetic reconnection in partially ionized plasmas is an important channel for energy release. While the plasmoid instability is well characterized in 2D fully ionized plasmas, its behavior in the presence of neutral-dominated plasma remains poorly understood in the nonlinear, high-Lundquist-number ($S = 10^5$) regime. We present high-resolution ($16384 \times 4096$ cells) two-dimensional two-fluid (ion $+$ neutral) simulations of Harris-sheet reconnection with upstream plasma beta $\beta = 2$, comparing fully ionized and partially ionized (ionization fraction $\xi = 10^{-1}$ and $10^{-2}$) regimes. Neutral-ion decoupling accelerates the linear tearing stage and alters the plasmoid hierarchy: the large-scale “monster” plasmoid that dominates the fully ionized case is suppressed, and the sheet instead fragments into a dense chain of sub-scale plasmoids. Below the neutral-ion decoupling scale $\ell_{\rm dec}$, ions concentrate into the plasmoids, reaching peak overdensities $\rho_i/\rho_{i,0} \approx 10$ ($\xi = 10^{-1}$) and $3-5\times10^{3}$ ($\xi = 10^{-2}$), while the neutrals remain comparatively smooth. This local pile-up raises the ionization fraction and recouples the two fluids within the plasmoids. Measured from the out-of-plane electric field at the reconnection sites, the reconnection rate in the $\xi = 10^{-2}$ case achieves $R_{\rm rec}\approx0.01$, whereas the $\xi = 10^{-1}$ case rises to a rate $\approx0.02$ and further $0.035$ when apparent coalescence occurs. In the $\xi = 10^{-2}$ case, the ambipolar drift drives a rapid ion inflow $\sim0.5\,v_{A,0}$ into the layer at the same reconnection sites, far above the neutral inflow velocity $\sim0.1\,v_{A,0}$. Here, $v_{A,0}$ is the upstream total Alfvén speed.
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All authors Yue Hu, Siyao Xu, Grzegorz Kowal, James M. Stone, Alex Lazarian, Hui Li

Solar and Stellar Astrophysics

FORTVSH: A Fortran Library For Vector Spherical Harmonics Computations

Justin G. Elfritz

The vector spherical harmonics (VSH) are crucial ingredients for representation of arbitrary vector fields in curvilinear coordinate systems throughout mathematical physics. Performant, efficient computations of the VSH are essential to high-performance computing applications that utilize spectral analysis, including magnetohydrodynamics (MHD) simulations for geophysics and astrophysics. The free open-source FORTVSH library provides a catalog of numerical routines for evaluating various VSH forms and related mathematical functions. This manuscript establishes the theoretical basis, addresses the computational need for efficient VSH solvers, and presents a comprehensive overview of the FORTVSH routines.
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High Energy Astrophysical Phenomena

Three-Dimensional Expansion of Iron Ejecta in Cassiopeia A with Chandra and XRISM

Aya Bamba, Tomoki Kadoya, Kouichi Hagino et al. (+4 more)

Measurement of the expansion structure of ejecta in supernova remnants (SNRs) provides important information about their explosion mechanism. We combine Chandra proper-motion measurements with XRISM Doppler measurements to derive an approximate, region-averaged three-dimensional velocity map of the Fe-K-emitting ejecta in Cassiopeia A (Cas A), one of the youngest Galactic core-collapse SNRs. Proper motions were measured using the optical flow method. We find that the Fe-K-emitting ejecta expand predominantly outward, except in the western region, with projected velocities of up to ~4580 km/s. The southeastern ejecta exhibit the highest three-dimensional velocity, reaching 5160+-320 km/s, based on the combined proper-motion and Doppler measurements. This velocity exceeds those measured for intermediate-mass elements (IMEs) such as Si and S, and the corresponding ejecta exhibit a relatively small line-of-sight velocity dispersion. These results are broadly consistent with the previously suggested inversion between the Fe-rich and IME-rich ejecta layers. The apparent inward motion or emergence of a new Fe-K emission component in the western region may reflect interaction with dense surrounding material, although the present data do not allow us to distinguish uniquely between these possibilities or to determine their physical origin.
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All authors Aya Bamba, Tomoki Kadoya, Kouichi Hagino, Jacco Vink, Manan Agarwal, Masahiro Ichihashi, Paul Plucinsky

Astrophysics of Galaxies

A Catalog of Giant Radio Source Candidates from TGSS ADR1 Using a Deep Learning–based Pipeline

Baoqiang Lao, Binghua Liang, Shaoguang Guo et al. (+4 more)

We present a catalog of 5,595 giant radio source (GRS) candidates, defined by a largest (projected) linear size (LLS) exceeding 0.7 Mpc. Of these, 4,566 would be new discoveries if confirmed. These candidates were identified through a systematic and automated search of the first Alternative Data Release of the TIFR GMRT Sky Survey (TGSS ADR1) using a deep learning–based pipeline that incorporates a radio sources detection model and the likelihood ratio method. Across the full sample, the LLS reaches up to $\sim$4.5~Mpc, with redshifts ranging from $z=0.056$ to at least $z=2.385$. The catalog comprises 4,210 giant radio galaxies and 1,030 giant radio quasars, with the remaining 355 candidates currently unclassified. We systematically analyze the distributions of their key physical properties, including spectral index, bending angle (BA), radio power ($P_{150}$), and $r$-band absolute magnitude. Our results show that GRS candidates are predominantly straight (a median BA of $11.0^\circ$) and follow an “L-shaped" BA–LLS distribution. The radio power vs. LLS ($P_{150}$–$D$) diagram reveals a concentration at $P_{150} < 10^{28}$ W Hz$^{-1}$, while rare high-power outliers ($>10^{28.5}$ W Hz$^{-1}$) with LLS $>$ 1 Mpc challenge self-similar evolutionary models. Additionally, 286 GRS candidates are found to be associated with cataloged galaxy clusters.
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All authors Baoqiang Lao, Binghua Liang, Shaoguang Guo, Junxiu Liu, Xiaolong Yang, Rushuang Zhao, Yang Kun

Instrumentation and Methods for Astrophysics · Cross-listed from cs.AI

Estimating Uncertainty in Galaxy Morphology Classification

Kai Cheng, Ruoqi Wang and Qiong Luo

Astronomers classify galaxy morphology to investigate cosmic evolution. While deep foundation models are increasingly utilized in Galaxy Morphology Classification (GMC), little work has been done on evaluating the uncertainty of GMC results. Uncertainty evaluation is important because astronomical data are inherently noisy due to instrumental and environmental limitations. Also, the continuous evolution of galaxies creates intrinsic morphological ambiguity. However, current foundation models operate as deterministic point estimators, failing to quantify the uncertainty. To overcome this limitation, we propose UEGMC, a post-hoc framework of Uncertainty Estimation for Galaxy Morphology Classification. It categorizes uncertainty in GMC into distinct types by model parameters, astronomical data, reference standards, or intrinsic physical ambiguities, thereby facilitating better classification. Our framework can directly predict uncertainties from representations extracted from the frozen backbones of foundation models, without computationally expensive sampling, therefore enabling fine-grained uncertainty evaluations. Our experimental results demonstrate that UEGMC provides competitive uncertainty quantification performance compared with previous methods.
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Astrophysics of Galaxies

Constructing a Hydrogen Line Library for Ly{\alpha} Emitters at Low Redshifts (z < 0.4): Estimating Dust Extinction and Assessing Paschen line Detectability with SPHEREx

Junho Song, Hyunmi Song and Hyunjin Shim

Hydrogen recombination lines, one of the strongest emission lines from star-forming galaxies, are used to probe the early Universe as indicators of star formation rates and ionizing photon production rates. Ratios between different recombination lines provide clues to estimate dust attenuation, in addition to the H II region physical diagnostics. To prepare for future near-infrared spectral surveys and optical narrow-band imaging surveys aiming for hydrogen lines in different redshifts, we construct hydrogen recombination line libraries by compiling data from published literature. Our compilation includes 260 galaxies mostly at z < 0.4, of which at least one hydrogen recombination line is observed. The specific hydrogen emission lines under investigation encompass three Balmer lines (H{\alpha}, He̱ta} and H{\gamma}) and Ly{\alpha} line. Of the compiled galaxies, we estimated dust extinction for 85 galaxies that have detections of at least two Balmer lines, by assuming the Case B recombination and Calzetti extinction curve, based on which Ly{\alpha} escape fraction is also inferred. For each of the 14 galaxies with detections of all three Balmer lines, we optimized the extinction curve so that it yields consistent E(B-V) values across the three possible Balmer line ratios, showing the variety in the slope of the dust attenuation curve. We further evaluated the feasibility of studying hydrogen emission line-selected galaxies with future spectral surveys such as SPHEREx by modeling the Paschen lines of our galaxy sample.
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Astrophysics of Galaxies

The ALMA carbon monoxide supernova (ACOS) survey II. Turbulent giant molecular clouds at the positions of core-collapse supernovae

M. Solar, M. J. Michałowski, J. Nadolny et al. (+11 more)

Context. Study of cold molecular hydrogen gas (hereafter molecular gas) provides crucial insights into its interplay with star-forming regions. However, the connection between molecular gas turbulence and the sites of massive star ($> 8~\rm{M}_{\odot}$) explosions as core-collapse supernovae (CCSNe) remains unexplored. Aims. We measure for the first time the turbulence of molecular gas in environments of CCSNe, with the aim to constrain the nature of their progenitors. Methods. In order to reach spatial resolutions of giant molecular cloud (GMC) sizes ($\sim 100~\rm{pc}$), we collected ALMA carbon monoxide $J = 2 \rightarrow 1$ spectral line ($\sim 230.54~\rm{GHz}$) observations (as a tracer of molecular gas) at the locations of 33 nearby CCSNe ($< 100~\rm{Mpc}$). Results. We found that CCSNe prefer molecular gas regions with high velocity dispersion compared to the average of their host galaxies. Conclusions. For CCSN progenitors, this observational evidence supports their increased formation in regions of high densities and/or their binary nature.
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All authors M. Solar, M. J. Michałowski, J. Nadolny, J. Sollerman, E. Zapartas, A. Oliva, L. Galbany, J. Hjorth, B. Ayala, M. Koprowski, A. Leśniewska, P. Nowaczyk, O. Ryzhov, B. Šlaus

Saturday 8 August

Instrumentation and Methods for Astrophysics

Efficient searches of small signals across two-channel noisy data: a challenge in Big Data observations

Maryam Aghaei Abchouyeh and Maurice H.P.M. van Putten

Searching for novel small signals in noisy data is preferably pursued by correlation in two or more independently operating channels. Signals of potential interest exist in tails beyond $\kappa\sigma$, where $\kappa$ denotes a multiple of the standard deviation $\sigma$ of the data. Since moving data is a major cost factor in Big Data analysis and heterogeneous computing more generally, efficiency may be optimized by restricting the correlations computation to the tails of two-channel data exceeding $\kappa\sigma$. Already, a moderate value $\kappa\gtrsim2$ realizes a data-reduction by at least an order of magnitude. Here, we study this approach using a novel Excess Probability Ratio (EPR), correlating Boolean data resulting from tails beyond a cut-off $\kappa\sigma$. We compare and rank EPR performance against conventional direct cross-correlation (DCC) and Pearson coefficient (PC), applicable to the original data with no cut-off. This benchmark is performed over different combinations of background noise Gaussian, Poisson and Uniform and signals Gaussian, Poisson, Uniform, Chirps and Sine waves. Results show performance of EPR to be comparable to that of PC, providing a new approach for significant improvements in efficiency with essentially no loss of sensitivity, relevant to the present era of Big Data observatories.
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Earth and Planetary Astrophysics · Cross-listed from physics.plasm-ph

Dipole-Field Magnetic Windows for Radio-Frequency Transmission Through Hypersonic Plasma Sheaths: A Reduced-Order Scaling Model

Richard Lieu

Hypersonic vehicles and atmospheric-entry bodies can experience radio-frequency communication blackout when shock-heated gas surrounding the vehicle becomes sufficiently ionized that plasma cutoff and collisional attenuation restrict electromagnetic transmission. Magnetic-window approaches attempt to reduce this loss by exploiting the anisotropic dispersion of a magnetized plasma, in which selected right-hand or whistler-like modes may propagate along preferred directions. This paper develops a reduced-order scaling model for magnetic-window transmission through a finite-thickness hypersonic plasma sheath when the magnetic source is represented as an onboard axial dipole. The model gives a closed-form estimate of the collisionless angular aperture, compares the underlying projected-cyclotron criterion with full cold-plasma dispersion roots, and extends the aperture estimate to a loss-limited cone using a collisional optical-depth approximation. A simplified neutral-density, speed, and ionization closure is used only to generate qualitative parametric maps and sensitivity trends. The results clarify how dipole-field decay, sheath thickness, radio frequency, vehicle scale, electron density, and collisions jointly constrain the candidate transmission window. The contribution is intended as a screening framework for selecting cases for full-wave electromagnetic simulation, nonequilibrium aerothermochemistry, antenna-coupling analysis, and laboratory validation, rather than as a demonstrated engineering solution to plasma blackout.
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Instrumentation and Methods for Astrophysics

Multi-night photometric repeatability of STDWeb: an empirical error budget from a 14-night campaign on a single field

Pierre-Yves Lechapelain

Web-based photometric pipelines such as STDWeb are routinely used by small observatories and professional-amateur networks across the full range of photometric science: variable stars, supernovae, exoplanet transits, transient follow-up. The formal magnitude uncertainty they report describes a single reduction of a single frame; campaign science instead requires the scatter of the same star, same field, night after night. We measure this empirically on the field of the Einstein Probe trigger EP-WXT 01709274151, observed on 14 nights in 2026 July: 157 Gaia-like G exposures reduced homogeneously with STDWeb, analysed through 101 constant field stars (10.5<G<14.5). The median formal error is 8.1 mmag (6.7 mmag for the bright half), and within a single night the empirical differential scatter matches it ($\chi_{\rm within}\simeq1$). Used naively - taking the pipeline's mag_calib, which lives in the instrumental pseudo-band - each star acquires a night-level offset of 7-9 mmag, the campaign scatter grows to 11-12 mmag, and the formal error is roughly half of the true one ($\chi_{\rm camp}=1.5$-$1.7$). We show that this entire excess is the epoch-dependent colour term: analysing the catalogue-system magnitude $m_{\rm sys}$ = mag_calib + colour term x (BP-RP) collapses the night term to 3.4 mmag, restores $\chi_{\rm camp}=1.0$-$1.1$, and improves the absolute Gaia-anchored per-star repeatability from 43 to 9.5 mmag, with the nightly zero-point peak-to-peak shrinking from 130 to 11 mmag and the airmass and colour correlations of the residuals vanishing. Stellar colours fitted from the light curves themselves reproduce Gaia BP-RP to 0.027 mag (r=0.98) and yield an identical budget: the correction needs no external colour catalogue. We provide the closed variance decomposition, practical recommendations, and a cautionary note on re-deriving zero points outside the pipeline.
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Astrophysics of Galaxies

GATOS: Distinct Feedback Modes in AGN Central Regions Revealed by Spatially Resolved JWST Spectroscopy

Lulu Zhang, Chris Packham, Erin K. S. Hicks et al. (+25 more)

This manuscript presents JWST MIRI/MRS observations of the central $r \approx 40-240$ pc regions of five active galactic nuclei (AGN) spanning a wide range of luminosities (${\rm log}\,L_{\rm bol}/{\rm erg\,s^{-1}} \approx 39.8-43.8$). Combining multiphase diagnostics from polycyclic aromatic hydrocarbons (PAHs), molecular hydrogen (H$_2$), and ionized gas at spatial scales of $\sim 4-24$ pc, this study presents a spatially resolved investigation into the effects of the two distinct AGN feedback modes–radiative and kinetic–on the surrounding medium. The results indicate that these two feedback modes, associated with AGN irradiation and shock processing, respectively, collectively drive the relative suppression of PAH emission in the nuclear regions of the targets studied here. Moreover, the coexistence of these two AGN feedback modes, especially the shock processing associated with either jets or outflows, in the central regions of AGN naturally explains both the bimodal distribution of PAH band ratios observed in the targets studied here and the seemingly disparate results reported in the literature. Although based on a limited sample, these findings provide new insights into calibrating star-formation rates (SFRs) from PAH emission in AGN, and more importantly, lay the groundwork for a practical framework to diagnose and quantify AGN feedback in the JWST era.
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All authors Lulu Zhang, Chris Packham, Erin K. S. Hicks, Ismael García-Bernete, Almudena Alonso-Herrero, Ric I. Davies, Martin J. Ward, Daniel E. Delaney, Takuma Izumi, Dimitra Rigopoulou, Cristina Ramos Almeida, Omaira González-Martín, Rogemar A. Riffel, Claudio Ricci, Montserrat Villar-Martín, Francoise Combes, Miguel Pereira-Santaella, Sebastian F. Hoenig, Andrew J. Bunker, Peter G. Boorman, Enrica Bellocchi, Nancy A. Levenson, Santiago García-Burillo, Fergus R. Donnan, Anelise Audibert, Lindsay Fuller, Tanio Díaz-Santos, David J. Rosario

Solar and Stellar Astrophysics · Cross-listed from math.AP

On the nonlinear instability of nonrotating Stars

Zhiwu Lin and Xinlin Wu

We study radial nonlinear instability of compactly supported nonrotating equilibria of the three-dimensional Euler–Poisson system with a physical-vacuum boundary. Let $n^u(\mu)$ denote the radial instability index furnished by the turning-point theory of Lin and Zeng. Under general structural assumptions on the pressure law, suppose that $n^u(\mu)>0$ and that the equilibrium is not a mass extremum, $M'(\mu)\neq0$. Conditional on the existence of a sufficiently regular radial solution on the relevant time interval, we establish two nonlinear escape criteria. First, every perturbation with Hamiltonian strictly below that of the equilibrium exits a fixed neighborhood on a logarithmic time scale controlled by the least unstable linear growth rate. For the subclass of data for which the associated Lyapunov functional is initially nonnegative, we also obtain an explicit exponential lower bound in the weighted displacement norm. Second, sufficiently small perturbations whose Riesz projection onto the finite-dimensional unstable subspace is not too small escape on a logarithmic time scale. The second argument uses the exponential trichotomy of the linearized Hamiltonian flow and an invariant-cone estimate. In the polytropic class, the conditional estimates combine with the radial physical-vacuum local theory to yield unconditional nonlinear instability in the corresponding classical-solution topology. The results complement Jang's nonlinear instability theorem for Lane–Emden stars by treating mechanisms that do not require initial alignment with a leading growing eigenmode and by applying, conditionally, to unstable branches for general equations of state.
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Astrophysics of Galaxies

KCWI Discovery of a Spatially Resolved Kpc-Scale Ionized Outflow in NGC 1275

Kylie Yui Dan, Hanae Inami, Thomas Bohn et al. (+5 more)

We present new Keck Cosmic Web Imager observations of the central few kiloparsecs of NGC 1275, the brightest cluster galaxy of the Perseus Cluster. These integral field spectroscopic data reveal a warm-ionized outflow traced by H$\beta$ and the [O III] doublet extending out to $\sim2.5$ kpc from the nucleus. The warm-ionized outflow has an [O III]-derived $v_{50}$ of up to $\sim570$ km/s, $w_{80}$ of up to $3780$ km/s, and H$\beta$-derived outflowing mass of $(2.7 \pm 0.3)\times 10^6$ M$_\odot$. Our H$\beta$-derived warm-ionized outflowing mass rate of 2.7$\pm$0.7 M$_\odot$ yr$^{-1}$ is comparable to the estimated cold molecular disk accretion rate of 1$-$10 M$_\odot$ yr$^{-1}$, which could be a sign of self-regulation between the pc-scale cold gas feeding the active galactic nucleus (AGN) and the warm wind accelerated out to kpc scales. In the host galaxy, we detect an enhancement in the [O III] / H$\beta$ ratio in the direction of the receding jet, which may imply jet interaction with the host interstellar medium. The outflow component also shows a clear enhancement of [O III] / H$\beta$ that positively correlates with $w_{80}$ and $v_{50}$, indicative of AGN influence and/or fast shocks. Both the outflow and host galaxy [O III] / H$\beta$ ratio decrease with increasing distance from the center, showing that the influence of the AGN is confined to the central $\sim2$ kpc. These results are the first resolved measurements of a kpc-scale ionized wind in NGC 1275 and provide a view into how both jets and winds contribute to the feedback cycles in complex cool core cluster systems.
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All authors Kylie Yui Dan, Hanae Inami, Thomas Bohn, Sylvain Veilleux, Vivian U, Tianmu Gao, Justin Kader, Rosalie McGurk

Instrumentation and Methods for Astrophysics

Design and simulation of a photonic lantern-inspired astrophotonic chip for spectral sensing

Avi Patel, Kevin A. Bundy, Aditya Sengupta et al. (+10 more)

Compact astrophotonic sensors can trade general-purpose spectral coverage for task-specific wavelength discrimination in a small integrated footprint. Developed with the Mazin Lab at UC Santa Barbara, this chip couples a single-mode input into a multimode interference region and seven-port fanout, producing wavelength-dependent output power fingerprints for spectral retrieval. Using ANSYS Lumerical FDTD simulations in silicon nitride, we compare symmetric and staggered-release geometries and quantify throughput, wavelength-dependent changes in the seven-port output distribution, and sensitivity near a 745 nm design point. We optimize over the tested geometric parameter space and identify designs with improved throughput and wavelength discrimination, including increased throughput-weighted Fisher information relative to the baseline. These results suggest that lantern-inspired integrated photonics can enable compact, task-specific spectral sensors for astrophotonic applications.
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All authors Avi Patel, Kevin A. Bundy, Aditya Sengupta, Matthew C. DeMartino, Anna Gagnebin, Emiel Por, Majid Mohammad, Michael Arena, Aled Cuda, Kiana Ejercito, Stephen Eikenberry, Ben Mazin, Holger Schmidt

Instrumentation and Methods for Astrophysics

Design evolution for the Wide-field Spectroscopic Telescope

Will Saunders, Corentin Cudennec, Roland Bacon et al. (+4 more)

WST is proposed as the next large ESO project to follow ELT, combining Multi-Object Spectroscopy and Integral Field Spectroscopy. Each mode offers order-of-magnitude gains over current systems, and each also presents unprecedented design challenges, both separately and in combination. For large MOS systems, both science performance and spectrograph costs vary steeply with the delivered image quality, so exceptional delivered image quality is paramount. But the 12m aperture and 2 degree field give WST an etendue larger than Rubin, larger that LAMOST, and larger than all other existing MOS telescopes combined; while the IFS, segmented primary and windy site all add additional constraints. Hence finding designs with good image quality is challenging. Eventually, 3-lens Forward Cassegrain designs with loss-less ADC were developed in variants mostly differentiated by M2 diameter. The lowest technical risk design, with the smallest M2, was selected as the baseline, with wind-shake control a primary driver. However, other designs have better as-designed image quality, and their perceived risks may diminish as the system design and underlying technologies mature. For IFS mode, delivered image quality is just as crucial, but this is achieved through additional optics and NGS GLAO over the 3'x3' field. The challenges come from (a) transferring the F/3.4 Forward Cassegrain focus to a fixed focus under the telescope; (b) a requirement that the 3'x3' field be selectable from a 13' diameter FoV without repointing the telescope; (c) including a suitably conjugated mirror for GLAO correction; (d) doing all this with minimised vignetting and surface count. Various designs were explored; the baseline design has a field-selecting pick-off at telescope focus, combined with large reimaging optics at Nasmyth, giving an F/28.5 fixed IFS focus.
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All authors Will Saunders, Corentin Cudennec, Roland Bacon, Philippe Dierickx, Roelof de Jong, David Lee, Gaston Gausachs

Astrophysics of Galaxies

The Quasar Feedback Survey: Ionised Outflows in type 2 QSOs with MUSE data

M. Bianchin, C. M. Harrison, T. Costa et al. (+13 more)

We study ionised gas properties in a sample of 18 luminous (log L$_{\rm bol}\geq45$ erg/s) obscured QSOs at 0.085<z<0.2 observed with VLT/MUSE as part of the multi-wavelength Quasar Feedback Survey (QFeedS) and with VLA at low- and high-resolution data. We compare the outflow-related quantities with values reported in the literature and investigate possible correlations between the outflows and other properties of the ionised gas such as the electron density. We adopt a non-parametric approach to characterise the ionised gas kinematics, traced by the [O III]5007 emission line, and use $W_{80}$ measured from the unresolved nuclear spectra as a threshold to identify outflow-dominated spaxels. A qualitative comparison between the radio and the $W_{80}$ maps shows that, in general, the peak of the radio coincides with the peak of the $W_{80}$. The [O III]5007 is used as a proxy for the ionised gas mass, and the outflow-related properties are obtained in two different ways: the global, which uses flux-weighted velocities and radii; and the peak, relying on radial profiles. We correct the [O III]5007 flux for extinction using the Balmer decrement. We take advantage of the MUSE sensitivity and use the [Ar IV]4711,4740 doublet, only observable in the integrated r=1.5” spectra, to measure the electron density in each galaxy. We obtain $500<n_{e}{\rm[ cm^{-3}]}<27700$, leading to 0.03$<\dot{M}_{\rm out}/{\rm (M_{\odot} yr^{-1})}<$4.17 and $39<\dot{E}_{\rm kin}/{\rm [erg/s]}<42$. Our results emphasise the importance of accurate n$_e$ determination, leading to a difference of ~1 dex in the outflow rates and kinetic powers. We observe a positive correlation between $n_e$ and $V_{\rm out}$, interpreted as compression of the gas at higher velocities. This correlation should be further investigated at other luminosity and redshift ranges, but it can inform future outflow simulation studies.
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All authors M. Bianchin, C. M. Harrison, T. Costa, V. Mainieri, R. A. Riffel, G. Venturi, D. Kakkad, C. Ramos Almeida, P. H. Cezar, S. Ward, A. Girdhar, S. Molyneux, L. Ulivi, E. P. Farina, J. Mullaney, F. Arrigoni Battaia

Solar and Stellar Astrophysics

From Light to Sound: Spectroscopic Evolution & Sonification of the flaring Nova V612 Scuti

Pragati Acharya, Elias Aydi, Kirill V. Sokolovsky et al. (+17 more)

We present photometric and spectroscopic observations of the 2017 Galactic nova V612 Sct, whose optical evolution was marked by multiple unusually large maxima. The eruption included two prominent flares lasting around a month each and reaching amplitudes of about 2.5 mag, followed by a series of smaller flares. Extensive spectroscopic monitoring reveals a striking pattern: with each flare, new absorption systems emerge at progressively higher velocities. This behavior, also seen in other flaring novae, provides evidence for repeated episodes of mass ejection or outflow at increasing velocities. V612 Sct also alternated between Fe II and He/N spectral phases during different stages of the eruption, establishing a clear connection between the photometric flares and major spectral transitions. We present two-dimensional dynamic spectra that directly trace the appearance of new absorption features contemporaneous with the light-curve flares. We also introduce a sonification of the spectroscopic sequence, offering an alternative representation of the temporal evolution of the eruption. These results support a picture in which repeated ejection episodes and shock formation play a central role in powering the multiple maxima observed in flaring novae.
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All authors Pragati Acharya, Elias Aydi, Kirill V. Sokolovsky, Brian D. Metzger, Laura Chomiuk, Peter Craig, Luca Izzo, Justin D. Linford, Shazrene Mohamed, Isabella Molina, Koji Mukai, Ken J. Shen, Jennifer L. Sokoloski, Paul Luckas, Terry Bohlsen, Olivier Garde, Joan G. Flo, Paolo Bellavista, Umberto Sollecchia, Forrest Sims

High Energy Astrophysical Phenomena

On the Physical Origins of Long Period Radio Transients

Yuanhong Qu and Bing Zhang

Long-period radio transients (LPRTs) are a rapidly growing class of coherent radio sources with periods ranging from minutes to hours, whose central engines and emission mechanisms remain unclear. Motivated by the detection of red dwarf (RD) companions in several LPRTs and by generic period constraints from the Roche limit and the mass transfer limit, we argue that LPRTs naturally separate into two broad classes: shorter-period sources that are likely isolated compact objects and longer-period sources that are compact objects in binary systems that are likely detached. For isolated objects, we find that isolated white dwarfs (WDs) generally have difficulty sustaining pair production and coherent radio emission unless the surface temperature is extremely high, while slow rotating neutron stars (NSs) can remain marginally active through inverse-Compton-driven pair cascades. For binary systems, asynchronous WD / NS + RD systems can power coherent radio emission through unipolar induction when the WD / NS magnetic field dominates the companion surface field, with relativistic electron cyclotron maser emission as the radiation mechanism, while at larger separations the system enters the magnetospheric interaction regime, possibly powered by magnetic reconnection. Bright X-ray counterparts favor magnetar-related systems and undetected X-ray emission is expected from WD-related channels. We propose a diagnostic flow chart that uses observational criteria to classify LPRTs and identify their central engines. These criteria lead to a physically motivated classification framework for LPRTs.
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Astrophysics of Galaxies

Kings of the Milky Way: A Homogeneous Gaia DR3 Analysis of King Open Clusters and the Galactic Disc Metallicity Gradient

Talar Yontan, Selçuk Bilir, Hikmet Çakmak et al. (+11 more)

This study aims to establish an internally homogeneous set of structural, astrophysical, and kinematical parameters for King open clusters and to assess their role as tracers of the Galactic thin disc. We present a homogeneous structural, astrophysical, and kinematical analysis of 27 King open clusters using high-precision Gaia DR3 astrometry, photometry, and spectroscopy. Cluster reddenings, distances, metallicities, and ages are determined via a homogeneous Markov Chain Monte Carlo isochrone-fitting approach applied to Gaia colour-magnitude diagrams. The derived parameters span E(G_BP-G_RP) = 0.113-1.933 mag, metallicities of [Fe/H] = -0.40 to +0.28 dex, ages from 17 to 6166 Myr, and heliocentric distances between 739 and 6272 pc. A comparison between astrometric and isochrone-based distances yields a median parallax difference of $-13\mu$as, indicating a good level of internal consistency between the photometric and astrometric distance scales within the adopted homogeneous framework. The radial metallicity behaviour of the King clusters is also examined using three complementary Galactic distance definitions and compared with the metallicity-radius relations obtained independently from 164 spectroscopically analysed open clusters from the literature. The King-cluster gradients are close to $-0.060$ dex kpc$^{-1}$ and are broadly consistent with those of the external reference sample, indicating that the homogeneously analysed King clusters follow the negative metallicity-radius trend traced by the broader thin-disc open-cluster population. Flatter gradients are found for young clusters, suggesting more homogeneous chemical enrichment at recent epochs. When dynamical constraints are applied to reduce the effects of radial migration and orbital blurring, the inferred gradient remains close to $-0.059$ dex kpc$^{-1}$.
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All authors Talar Yontan, Selçuk Bilir, Hikmet Çakmak, Olcay Plevne, Esin Soydugan, Seval Taşdemir, Remziye Canbay, Deniz Cennet Ç{\i}nar, Seliz Koç, Hülya Karagöz, Burçin Tan{\i}k Öztürk, Furkan Akbaba, Özcan Çal{\i}şkan, Timothy Banks

Astrophysics of Galaxies

A New Window on the H{\alpha} Luminosity Function and Star Formation Rate Density from 1.2 < z < 6.6 from JWST Medium-Band Photometry

Nicholas S. Martis, Chris Willott, Gregor Rihtaršič et al. (+23 more)

We present the first self-consistent measurement of the H{\alpha} luminosity function over a wide redshift range, covering cosmic noon into the epoch of reionization. Our analysis utilizes a novel method based on James Webb Space Telescope (JWST) NIRCam medium-band imaging. We combine data from the CANUCS, JWST in Technicolor, and JUMPS surveys which offer deep, uniform imaging (29.5-30 AB, 3{\sigma}) with extensive NIRCam medium-band coverage, reaching up to 29 total filters (up to 20 JWST) when including ancillary Hubble Space Telescope (HST) ACS and WFC3/UVIS data. The superb spectral energy distribution (SED) sampling enables precise, reliable photometric redshift estimation (outlier fraction 1.7%, {\sigma} N_MAD = 0.039 for this sample) as well as accurate continuum subtraction and line flux measurement verified by spectroscopic follow-up (no systematic offset, 0.23 dex scatter). We measure the H{\alpha} luminosity function (LF) from 1.25 < z < 6.6 by tracing the H{\alpha} emission line in 11 medium-band filters. The combination of depth, redshift coverage, and statistical power is unique, providing strong constraints on the shape of the LF over almost three orders of magnitude in luminosity. Our dense SED sampling enables us to reliably correct for dust attenuation and derive dust-corrected star formation rate functions as well as the evolution of the cosmic star formation rate density over the full redshift range. We recover the peak at z ~ 2 and a decrease toward z = 6, though with a higher normalization more in line with recent IR measurements than UV, though eclipsing both. This potential tension will be addressed in future work utilizing larger surveys with MIR coverage to better constrain the bright end of the luminosity function and the effects of dust.
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All authors Nicholas S. Martis, Chris Willott, Gregor Rihtaršič, Vesna Pirc Jevšenak, Roberto Abraham, Yoshihisa Asada, Maruša Bradač, Gabriel Brammer, Guillaume Desprez, Vicente Estrada-Carpenter, Kartheik Iyer, Lamiya Mowla, Adam Muzzin, Gaël Noirot, Ghassan T. E. Sarrouh, Marcin Sawicki, Sunna Withers, Giordano Felicioni, Jon Judež, Danilo Marchesini, Vladan Markov, Katherine Myers, Luke Robbins, Visal Sok, Wren Suess, Roberta Tripodi

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

Probing Memory-Burdened Primordial Black Holes with High-Energy Neutrinos

Arian Moradi Asl, Sandhya Choubey and Andreas Lund

The memory-burden effect can suppress the late-time evaporation of primordial black holes (PBHs), allowing those that would otherwise have evaporated via Hawking radiation to survive until the present epoch. These lighter PBHs emit high-energy and ultra-high-energy neutrinos, opening the tentalizing possibility of discovery via neutrino telescopes. We study the constraints on memory-burdened PBHs from current IceCube HESE, MESE, and EHE data; and forecast the sensitivity reach of IceCube-Gen2 radio and GRAND200k. In particular, we study how this signal depends on whether the initial PBH population is described by a log-normal mass function or by a monochromatic one. We find that log-normally distributed populations can be more strongly constrained than monochromatic populations with the same median mass primarily because their low-mass tails enhance the high-energy neutrino flux. We show that current IceCube data provide the leading limits for a lower memory burden parameter $k$, whereas the projected radio detectors become substantially more sensitive for higher values of $k$. We also study a scenario where future experiments would see a positive signal coming from PBHs. We consider a representative 30-event signal in IceCube-Gen2 radio and GRAND200k and study how well one could distinguish the two mass-function hypotheses. We find that it is easier to disfavor the monochromatic distribution when the log-normal distribution is assumed to be true. Finally, we study how well the parameters of the memory-burdened PBHs can be estimated in these future experiments.
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Astrophysics of Galaxies

Diagnosing the Fe line complex of the intracluster medium by XRISM high-resolution spectroscopy

K. Fukushima, L. Hirata, N. Y. Yamasaki et al. (+17 more)

We aim to test the validity of the CIE framework in the ICM by performing line diagnostics based mainly on resolved Fe-K emission lines. Methods. We analyse Resolve full-array spectra of 17 galaxy clusters. Prominent Fe-K line components (the Fe xxv w, x, y, z, and Fe xxvi Ly{\alpha}1,2 lines) are removed from plasma emission models and instead fitted with Gaussian profiles, enabling direct measurements of line fluxes without relying on synthetic spectral models. Some cool-core systems show w/z ratios lower than predicted by about 20 per cent, and a broader w than z, consistent with resonant scattering effects. The y/x ratios exhibit marginal deviations from model predictions for some objects, suggesting possible origins of cascade process due to electron recombination and contribution from low-ionised Fe. The Fe Ly{\alpha}2/Ly{\alpha}1 ratios are globally close to the expected value of about 0.5, and the samples with good photon statistics prefer 0.55. This subtle excess is consistent with an unresolved contribution to Ly{\alpha}2 from the magnetic-dipole (M1) transition, which is absent from one of the atomic codes considered here. More interestingly, systems at around 7 keV preferentially exhibit Ly{\alpha}2/Ly{\alpha}1 ratios above 0.55. Although the statistical significance of this trend is limited, it suggests that resolved Fe Ly{\alpha} spectroscopy may provide a sensitive probe of additional atomic processes to collisional excitation, including dielectronic and radiative recombination and polarisation effects.
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All authors K. Fukushima, L. Hirata, N. Y. Yamasaki, P. Chakraborty, S. Dupourqué, Y. Fujita, L. Gu, C. Kilbourne, K. Matsushita, F. Mernier, E. D. Miller, K. Nakazawa, Y. Omiya, N. Ota, A. Sarkar, K. Sato, M. Sun, Y. Uchida, I. Zhuravleva, H. Yamaguchi

Astrophysics of Galaxies

Breathing Fire: Hot Dust in the Big Three Dragons at z = 7.15

Gitanjali Rajulal, Hiddo S. B. Algera, Yuma Sugahara et al. (+25 more)

We present new Atacama Large Millimeter/submillimeter Array (ALMA) Band 9 ($\lambda_\mathrm{obs} = 0.45\,\mathrm{mm}$) and 4 ($\lambda_\mathrm{obs} = 2.2\,\mathrm{mm}$) observations towards the Big Three Dragons, a pair of merging Lyman-break galaxies (LBGs) at $z=7.15$. The system was previously detected in ALMA Bands 6, 7 and 8 ($\lambda_\mathrm{obs} = 0.73 - 1.32\,\mathrm{mm}$), which, combined with our new observations, allows us to robustly constrain its dust temperature and obscured SFR. The unresolved Band 4 observations yield a $3.5\sigma$ detection, and the $0.4''$ Band 9 observations detect the Eastern and Western LBGs at $3.7$ and $3.5\sigma$, respectively. Through modified blackbody fitting, we infer a global dust temperature of $T_d = 78_{-23}^{+35}\,\mathrm{K}$ for the system, which implies a high IR luminosity of $\log(L_\mathrm{IR}/L_\odot) = 12.32_{-0.41}^{+0.43}$. This makes the Big Three Dragons one of the most IR-luminous systems known at $z>7$, with a total $\mathrm{SFR}_\mathrm{UV+IR} = 267_{-153}^{+418}\,M_\odot\,\mathrm{yr}^{-1}$ that is almost completely obscured ($f_\mathrm{obs} = 0.94_{-0.09}^{+0.04}$). Using resolved ALMA observations in Bands 6, 8 and 9, we confirm both LBGs have hot dust temperatures ($T_d \approx 67 - 84\,\mathrm{K}$) and correspondingly high obscured fractions ($f_\mathrm{obs} \approx 0.88 -0.95$). We find the Western LBG to fall $\sim1\,\mathrm{dex}$ above the canonical IRX-$\beta_\mathrm{UV}$ relation, suggesting patchy dust obscuration. The compact Eastern component, on the other hand, is consistent with a Calzetti- or SMC-like dust screen within the uncertainties. Together with the similarly hot dust temperature recently reported for the $z=8.31$ galaxy MACS0416-Y1, our results suggest a non-negligible fraction of star formation at the bright end of the UV luminosity function is highly dust-obscured, even at $z\gtrsim7$.
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All authors Gitanjali Rajulal, Hiddo S. B. Algera, Yuma Sugahara, Tom J. L. C. Bakx, Takuya Hashimoto, Suzuka Arai, Akio K. Inoue, Ikki Mitsuhashi, Manuel Aravena, Karin Cescon, Chian-Chou Chen, Elisabete da Cunha, Pratika Dayal, Ilse De Looze, Andreas Faisst, Yoshinobu Fudamoto, Rodrigo Herrera-Camus, Hanae Inami, Anton M. Koekemoer, Shoichiro Mizukoshi, Michael Romano, Lucie Rowland, Sander Schouws, Renske Smit, Livia Vallini, Wei-Hao Wang, Giovanni Zamorani, Anita Zanella

Astrophysics of Galaxies

First detection of C2H+ in the interstellar medium

Arshia M. Jacob, Karl M. Menten, Sandra Brünken et al. (+10 more)

Despite the detection of nearly 350 molecules in the interstellar medium, almost half of which are carbon chains, the pathways that build molecular complexity remain poorly understood. Observed abundances of carbon-chain and aromatic species are difficult to reconcile with existing top-down or bottom-up formation scenarios, due in part to limited observational constraints and incomplete theoretical understanding. In particular, small intermediary ions, key drivers of ion-molecule reactions capable of seeding larger hydrocarbons and aromatic rings, could provide critical support for the bottom-up formation scenario. Constraining the abundance and chemistry of these ions is therefore essential to test whether bottom-up growth can operate efficiently under interstellar conditions. Here, we report the first detection of the small hydrocarbon cation ethynylium, C2H+, toward the Orion Bar, based on observations with the APEX 12m sub-mm telescope of its lowest-lying J=3-2 rotational transition near 211GHz, which exhibits a unique spectroscopic fingerprint through resolved Lambda-doubling and hyperfine splitting components, as recently measured in the laboratory. Meudon PDR models successfully reproduce these values, placing C2H+ formation at the outer edges of PDR fronts. Our results link C2H+ production to CH+ and CH3+ within a network of ion-molecule reactions driven by vibrationally excited H2, a scenario now further supported by recent detections of these species in PDRs like the Orion Bar with JWST observations. The importance of C2H+ lies in its role as a key intermediate: it produces C2H2+ and subsequently C2H3+, effectively channelling small C2 building blocks toward larger hydrocarbons and facilitating bottom-up growth at the PDR surface. Targeted searches for C2H+ in other regions promise to provide a potentially decisive probe of ion-driven bottom-up chemistry in the ISM.
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All authors Arshia M. Jacob, Karl M. Menten, Sandra Brünken, Arnaud Belloche, Friedrich Wyrowski, Weslley G. D. P. Silva, Oskar Asvany, Sarwar Khan, Slawa Kabanovic, Kim Steenbakkers, Gerrit C. Groenenboom, Britta Redlich, Stephan Schlemmer

Cosmology and Nongalactic Astrophysics

Implicit Likelihood Inference and $z$-Binned Reconstruction of Dark Energy $w(z)$

Ke Wang, Jia-Yi Feng and Jianbo Lu

In this paper, to reconstruct the equation of state (EOS) of dark energy (DE) $w(z)$ with the redshift binning method, we first introduce a $w_i$CDM model with a piecewise-constant EOS in $7$ redshift bins. Then, we turn to the Learning the Universe Implicit Likelihood Inference (LtU-ILI) pipeline to perform a multi-round ILI of $w_i$ from the cosmological data combination, including $TT$, $TE$, $EE$ and lensing power spectra of Planck 2018, distance ratios of DESI DR2 and corrected apparent magnitudes of SNIa from Pantheon+ sample. More precisely, we build the Cosmic Microwave Background (CMB) power spectrum, Baryon Acoustic Oscillation (BAO) distance ratio and Type Ia Supernovae (SNIa) apparent magnitude simulators by $\mathtt{CLASS}$ and embed them into the LtU-ILI pipeline. And, using Sequential Neural Likelihood Estimation (SNLE), we sequentially train neural networks with $6$ rounds of total $6\times20000$ simulations to target a “black box” likelihood of our forward model $w_i$CDM. Finally, with the estimated posteriors of $w_i$, we find that except for the unconstrained $w_5$ and $w_6$ (the last two bins), our reconstruction of $w(z)$ marginally favors dynamical DE in the first bin and is consistent with the cosmological constant at $68\%$ C.L. in the other bins.
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Solar and Stellar Astrophysics

JWST Reveals a Galaxy-Wide Association of Red Supergiants with OB Stars in NGC 5584

Min Dai, Shu Wang and Biwei Jiang

The spatial relationship between young and evolved massive-star tracers offers a means of probing recent star formation across galactic disks. We combine JWST/NIRCam, $Swift$/UVOT UVW2, and GALEX FUV/NUV images to investigate the spatial association between red-supergiant (RSG) candidates and UV-selected star-forming complexes (SFCs) in the spiral galaxy NGC 5584. We identify 5,310 RSG candidates using colour–magnitude criteria and define 106 UV-selected SFCs from the UVOT/UVW2 morphology, with their FUV and NUV luminosities measured independently using the GALEX images. We find that 82% of the UV-selected SFCs overlap significant RSG overdensities, indicating a galaxy-wide statistical association between UV-bright SFCs and the evolved massive-star population. Among the 93 SFCs with reliable JWST coverage, the UV-$\beta$-corrected FUV and NUV luminosities correlate tightly with the JWST/NIRCam luminosities, with Pearson correlation coefficients of $r=0.962$–$0.971$. MIST isochrone comparisons for 43 RSG-rich SFCs indicate a characteristic age of $\log(\mathrm{age/yr})\simeq 7.16$. These results show that RSG overdensities and UV-selected SFCs trace related but distinct phases of recent massive-star formation. Their spatial correspondence is statistical rather than one-to-one and likely reflects differences in stellar age, dust extinction, spatial resolution, aperture coverage, and local star-formation history.
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Astrophysics of Galaxies

A Two-level Radial-velocity Zero-point Calibration for LAMOST MRS with Gaia and APOGEE and a Value-added RV Catalogue

Jinming Zhang and Haibo Yuan

The LAMOST Medium-Resolution Survey (MRS) provides a large stellar spectroscopic data set for Galactic kinematics and time-domain radial-velocity (RV) studies. However, the multi-spectrograph, multi-exposure, multi-fiber observing strategy can imprint RV zero-point (RVZP) systematics that vary across instrumental and temporal hierarchies. We construct a two-level empirical RVZP correction to LAMOST DR12 MRS using Gaia DR3 magnitude-colour-corrected RVs and APOGEE DR17 RVs as external references: a spectrograph-exposure correction in (lmjm, planid, spid) units, followed by a fiber-time correction in (spid, fiberid, time_tag) units. Within each unit, RVZPs are estimated from Gaia and APOGEE residuals using a weighted-median estimator, and are subtracted from the pipeline RVs to obtain corrected velocities. For high-S/N spectra, the scatter relative to APOGEE DR17 decreases from ~1.1 km/s to ~0.52 km/s after the full two-level correction, implying a ~2x improvement in RV precision. We release a value-added catalogue of two-level-corrected RVs for 11,129,477 blue-arm spectra, including 8,158,271 single-exposure spectra and 2,971,206 coadded spectra, enabling consistent RV analyses across exposures, spectrographs, fibers, and time.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Gravitational radiation from binary systems with time varying masses

Teodora M. Matei, Cristian A. Croitoru and Tiberiu Harko

We consider the properties of the gravitational radiation emitted by massive stars in binary systems with time varying mass, orbiting around each other in Keplerian orbits under the influence of the gravitational force. When this effect is combined to the quadrupole expression of the gravitational radiation, some supplementary terms in the standard formulae describing radiative effects do appear. By using the generalized quadrupole formalism, with time dependent masses, we obtain the expressions describing the time variation of the angular momentum, semimajor axis, eccentricity and periastron shift of the binary system. As a simple application of the developed formalism we consider in detail two cases of the mass variation, by assuming a linear and an exponential time dependence, respectively. The gravitational radiation characteristics corresponding to these models are fully investigated numerically with the help of a dedicated software package \href{https://github.com/croi900/GRAV-T}{GRAV-T}, specifically developed for the study of the gravitational radiation of the mass varying systems. The impact of the gravitational wave emission on the merger of two magnetars losing mass due to neutrino heated winds is also investigated in detail. The obtained results could be important for the understanding of general relativistic effects in the case of the variation of the gravitational mass with time, which sensitively influences the properties of the gravitational radiation emission.
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Instrumentation and Methods for Astrophysics

Spec-S5: A Next-Generation All-Sky Spectroscopic Facility Enabling Large-Scale Surveys for Cosmology and Astrophysics

Claire Poppett, David J. Schlegel, Arjun Dey et al. (+8 more)

The Stage-5 Spectroscopic Experiment (Spec-S5) is a next-generation, all-sky spectroscopic facility designed to address fundamental questions in cosmology and astrophysics. Building on the legacy of the Dark Energy Spectroscopic Instrument (DESI), Spec-S5 will upgrade two existing 4-m telescopes into 6-m, wide-field observatories, each equipped with a highly multiplexed spectrograph capable of measuring 13,000 spectra simultaneously. This overview paper summarizes the science motivation, system architecture, and integration strategy of the project. Spec-S5 will deliver a more than tenfold increase in spectroscopic capability, enabling transformative surveys in the post-Rubin, post-DESI era and advancing our understanding of dark matter, dark energy, and cosmic structure formation.
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All authors Claire Poppett, David J. Schlegel, Arjun Dey, Klaus Honscheid, Paul Martini, Alex Drlica-Wagner, Pat Jelinsky, Chang-Jin Oh, Konstantina Boutsia, Joseph H. Silber, Nicholas R. Wenner