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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 25 June

Instrumentation and Methods for Astrophysics

Interferometric Analysis of Air-shower Radio Emission in the Near Field with an Information Field Theory Approach

Keito Watanabe, Karen Terveer, Sjoerd Bouma et al. (+29 more)

Current reconstruction techniques for air-shower radio emission generated by cosmic rays have shown great success, having been applied to several radio detectors over the last decade. Nevertheless, they are limited by their high computational cost, simplified approximations, and signal information used for reconstruction. As such, advanced analyses are required to not only be able to perform a holistic reconstruction of all parameters, but also to conduct near-field interferometry of the air shower. This can be achieved through Information Field Theory (IFT), an imaging reconstruction framework based on Bayesian inference that can extract all available information within the signal to infer distributions of field-like quantities. In this chapter, we highlight current novel approaches that use IFT for air shower reconstruction, and the potential of their applicability towards SKA-Low.
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All authors Keito Watanabe, Karen Terveer, Sjoerd Bouma, Justin Bray, Stijn Buitink, Arthur Corstanje, Vital De Henau, Tim Huege, Edwin Dickinson, Vincent Eberle, Torsten Enßlin, Brian Hare, Haoning He, Jörg Hörandel, Clancy James, Philipp Laub, Xingyu Li, Hermann-Josef Mathes, Katharine Mulrey, Anna Nelles, Subhadip Saha, Felix Schlüter, Olaf Scholten, Ralph Spencer, Christopher Sterpka, Satyendra Thoudam, Gia Trinh, Paulina Turekova, Darko Veberic, Chao Zhang, Pengfei Zhang, Yi Zhang

Astrophysics of Galaxies

Search for Seeds of The Cradle of Stars: Study of The Evolution From Atomic to Molecular Hydrogen Clouds with 1000 AU Scale Resolution

Hiroaki Yamamoto, Yamato Matsuzuki and Kengo Tachihara

The aim of this science case for SKA1-Mid is to elucidate the spatial and velocity structure of the Cold Neutral Medium (CNM) on scales below the Field length, thereby elucidating the physical processes that govern CNM structure formation and its role in the earliest stages of molecular cloud formation. This goal will be achieved through a unique observational combination of several-arcsecond angular resolution, high velocity resolution, and unprecedented surface-brightness sensitivity. These observations will reveal the characteristic size, morphology, velocity structure, and internal dynamics of CNM clumps, and will directly connect such structures to the earliest phases of the atomic to molecular transition. Full-polarization observations with SKA1-Mid will also enable emission-based Zeeman measurements of the CNM, allowing the magnetic field strength to be mapped and opening a new window on the role of magnetic fields in CNM formation and evolution. In particular, this will make it possible to determine whether magnetic fields primarily inhibit fragmentation by supporting the gas against compression, or instead guide anisotropic condensation and promote the development of small-scale CNM structure through thermal instability. In combination with interferometric spatial filtering and high spectral resolution, SKA1-Mid will selectively trace the CNM and robustly identify individual clumps in both position and velocity space. These capabilities will provide decisive tests of thermal instability and the two-phase turbulence model, and will establish a new observational foundation for understanding how molecular clouds emerge from the multi-phase atomic interstellar medium.
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Astrophysics of Galaxies

Cm-wavelength Studies of Molecular Gas and Star Formation at High Redshift with the SKA

Ran Wang, Jeff Wagg, Mark T. Sargent et al. (+6 more)

The Square Kilometre Array will be a revolutionary instrument for the study of gas in the distant Universe. At frequencies below ~50 GHz, observations of redshifted emission from low-J transitions of CO, HCN, HCO+, and HNC, etc. provide insight into the kinematics and mass budget of the cold, dense star-forming gas in galaxies. Over the past decade, sensitive imaging using ALMA has detected and resolved the redshifted high-J molecular CO line emission and far-infrared fine structure lines in samples of galaxies over a wide redshift range, shedding light on active star-formation processes at the early epoch of galaxy evolution. In recent years, increasing numbers of young galaxies at high redshift are discovered by JWST, which significantly improved our knowledge of different galaxy populations across cosmic time. In this updated chapter of the SKA science book, we would like to highlight the importance of studies of the low-J molecular lines in high-z galaxies using SKA toward high frequencies, discussing the request of frequency coverage beyond 15 GHz and emphasizing its crucial role in exploring the cold molecular gas content in the young galaxy populations in the early universe and investigating the regions of active-star formation using molecular CO and various dense gas tracers.
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All authors Ran Wang, Jeff Wagg, Mark T. Sargent, Manuel Aravena, Mamta Pandey-Pommier, Elisabete da Cunha, Eric Murphy, Dominik Riechers, Jacqueline Hodge

Instrumentation and Methods for Astrophysics

Single object observations: Large telescopes vs. multiple small telescopes

Sagi Ben-Ami and Eran Oded Ofek

A significant fraction of large-telescope observing time is devoted to single-object spectroscopy and photometry. We compare the cost-effectiveness of different telescope architectures, including single seeing- and diffraction-limited telescopes and arrays of seeing-limited or diffraction-limited telescopes. We use the survey speed per unit cost as the performance metric. For single telescopes with equal collecting area, diffraction-limited operation becomes more cost-effective once seeing-limited observations enter the background-dominated regime, typically at visible magnitudes of $\sim20$. For unresolved single-object observations, arrays of seeing-limited telescopes are generally more cost-effective than a single seeing-limited telescope. When matched in survey speed, a single diffraction-limited telescope outperforms an array of small seeing-limited telescopes only for targets fainter than $\sim20$–$24\,$mag, while a single large diffraction-limited telescope becomes more cost-effective than an array of smaller diffraction-limited telescopes only for targets fainter than $\sim26$–$28\,$mag. We conclude with a discussion on aspects related to the minimum telescope size and maintenance of telescope arrays. These conclusions are sensitive to the specific assumptions and system parameters adopted for each architecture and should therefore be interpreted with appropriate caution. Our results motivate the development of telescope arrays such as MAST and LFAST and may inform the design of future optical facilities.
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High Energy Astrophysical Phenomena

A Boundary-Consistent Two-Zone Electron Kernel for Distant Pulsar Contributions to Positron Flux and Anisotropy

Yiwei Bao, Jie-Shuang Wang and Hao Zhou

We present a semi-analytical series solution for electron and positron propagation in a spherical two-zone diffusion model. The solution treats slow diffusion inside a near-source region and standard interstellar diffusion outside it, while synchrotron and Klein–Nishina inverse-Compton cooling are included through energy characteristics. The formulation avoids the oscillatory cancellations of direct two-zone integral evaluations and preserves the sharp radiative cooling boundary seen in finite-volume checks. We apply the kernel to pulsar contributions to the local cosmic-ray lepton flux. Nearby pulsars remain natural candidates near the TeV cutoff, but at tens to hundreds of GeV the larger source volume allows more distant pulsars to contribute collectively: for a disk half-thickness of $0.2\,{\rm kpc}$, sources beyond $1\,{\rm kpc}$ can still provide $37$–$47\%$ of the $10$–$100\,{\rm GeV}$ flux. Comparing with AMS-02 positron data and all-electron anisotropy limits, and imposing an inner $100\,{\rm pc}$ cavity motivated by the Local Bubble and pulsar proper motions, we find that Geminga-scale slow-diffusion halos remain compatible with current data. The fitted pulsar component is dominated by sources beyond $0.3\,{\rm kpc}$, but flux and anisotropy data alone do not uniquely determine the halo size; external information such as TeV halo morphology is still required.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.AI

A Multi-Level Validation and Traceability Framework for AI-Generated Telescope Scheduling Decisions

Hengchu Xiao and Chuanjun Wang

With the gradual introduction of AI into telescope scheduling, AI-based decision-making has shown advantages in handling complex multi-constraint problems. However, its outputs often suffer from inconsistent data references, reasoning errors, and non-executable decisions, limiting applicability in high-reliability observational tasks. In this work, we propose a multi-level validation and traceable reasoning framework that performs systematic reliability verification of AI-generated decisions prior to execution, and enables explicit representation of the reasoning process to support traceable decision-making. The framework integrates data reference validation, logical consistency checks, and observational and instrumental constraint verification to filter and correct invalid decisions. It also introduces atomic reasoning units and their dependency relationships, representing scheduling decisions as a sequence of interconnected reasoning steps that support error localization and post hoc analysis. Experiments show that the framework improves executability and reliability of AI scheduling and reduces loss of transient opportunities. In particular, feedback correction and structured validation of reasoning steps enhance the ability to repair and block erroneous decisions, especially in complex scenarios. Compared with pure AI methods, the framework-enhanced approach maintains flexibility while substantially improving reliability and executability. These results demonstrate a feasible and verifiable pathway for applying AI to high-reliability astronomical observation scheduling.
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Instrumentation and Methods for Astrophysics

Detectors for CLASS-W2: The second 90 GHz telescope of the Cosmology Large Angular Scale Surveyor

John W. Appel, Kyuyoung Bae, Charles L. Bennett et al. (+26 more)

The Cosmology Large Angular Scale Surveyor (CLASS) is measuring the Cosmic Microwave Background (CMB) polarization anisotropy on the largest angular scales (>1 degree) to probe the epochs of inflation and reionization. To enhance the CMB mapping speed, we have built, tested, and commissioned in August 2025 a second 90 GHz receiver (CLASS-W2) with a detector focal plane composed of feedhorn-coupled Transition Edge Sensor (TES) bolometers fabricated at NIST-Boulder. The focal plane consists of four modules, each containing 37 feedhorns coupling orthogonal polarizations onto two TES bolometers, for a total of 296 optically sensitive detectors. Laboratory tests show highly uniform TES properties with an array average critical temperature of 184+-3 mK, a thermal conductance of 460+-47 pW/K, and a normal resistance of 7.8+-0.3 mOhms. The detector array has an average band center frequency of 95.2 GHz with 28.3 GHz bandwidth, and achieves a detector yield of 94%. On-sky measurements indicate a mean detector optical load of 3.3 pW, corresponding to an antenna temperature of ~23 K. The array's average beam solid angle is 124 $\mu$sr, with a full width at half maximum of 0.592 degrees, and the end-to-end average optical efficiency is 0.37. We find that high-frequency 'blue-leak' radiation couples directly to the TES bolometer islands; adding a metal-mesh low-pass filter with cutoff frequency of 157 GHz in front of the focal plane suppresses the 'blue-leak' power by 0.9 pW. The four-module array achieves a noise-equivalent temperature of NET= 16 uKrtS. Adding this array has boosted the CLASS 90 GHz mapping speed by 41%.
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All authors John W. Appel, Kyuyoung Bae, Charles L. Bennett, Michael K. Brewer, Sarah Marie Bruno, Carol Yan Yan Chan, Joseph Cleary, Sumit Dahal, Jullianna Denes Couto, Kevin L. Denis, Shannon M. Duff, Joseph R. Eimer, Thomas Essinger-Hileman, Naina Gupta, Johannes Hubmayr, Gregory Jaehnig, John Karakla, Matthew Koc, Jeff Van Lanen, Yunyang Li, Michael J. Link, Tammy Lucas, Tobias Marriage, Carolina Morales Perez, Matthew A. Petroff, Caleigh Ryan, Rui Shi, Deniz A. N. Valle, Edward J. Wollack

High Energy Astrophysical Phenomena

Long-Period Transients as a new frontier in time-domain astronomy

Manisha Caleb, Dougal Dobie, Natasha Hurley-Walker et al. (+8 more)

Long-period radio transients (LPTs) are relatively new astrophysical objects occupying the observational gap between canonical pulsars and slowly varying radio variables. They emit coherent, highly polarised radio bursts with periods from minutes to hours, often exhibiting millisecond- to minute-scale substructure, short duty cycles, and broadband emission. Their radio luminosities typically exceed what rotational energy alone can power, necessitating alternative energy sources such as magnetic field decay, magnetospheric reconnection, or binary interactions. As multiwavelength counterparts in X-ray, optical, and infrared bands provide key constraints on progenitors and emission mechanisms, observational evidence points to a diverse progenitor population including ultra-long period magnetars and magnetic white dwarf binaries. Fast imaging surveys with SKAO and its precursors are opening a new discovery space, enabling systematic detection, high-cadence monitoring, and detailed follow-up. Despite the challenges of high extinction, intermittent emission, and computational demands for discovery, the expanding LPT population provides a new laboratory for studying coherent radio emission in a range of compact-object systems, from pulsars to white dwarf binaries. This diversity allows us to test how the emission processes depend on magnetic field strength, rotation, and binary interaction.
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All authors Manisha Caleb, Dougal Dobie, Natasha Hurley-Walker, Yogesh Maan, Yuan Mao, Hao Qiu, Nanda Rea, Kovi Rose, Iris de Ruiter, Ben Stappers, Ziteng Wang

Earth and Planetary Astrophysics

Ring Spacing from a Fourth-Order Radial Feedback Green Function in a Keplerian Accretion Disk

Yiwei Bao and Can Cui

ALMA observations of protoplanetary disks reveal ubiquitous concentric ring structures whose origin remains debated. We present an exactly solvable local model for ring spacing in a Keplerian disk. The passive advection–diffusion problem with a general vertical diffusivity profile separates into a vertical Sturm–Liouville spectrum and a radial modified-Bessel Green function. This passive kernel is smooth and does not by itself generate a periodic ring train. We therefore introduce a minimal fourth-order radial feedback closure for the ring-averaged surface density. For a localized steady ring source, the resulting Green function has a damped oscillatory exterior branch whenever the decaying spatial roots are complex. Under an observationally motivated AU scaling, the same dimensionless solution gives an illustrative spacing of order $12$~AU, distinct from the fastest-growing temporal wavelength. The model separates the passive transport kernel from the feedback mechanism that selects the observable radial scale. Because this mechanism is internal to the disk, it does not require pre-existing planets. The vertical diffusivity profile affects the background kernel but is not the source of the Green-function oscillation.
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Cosmology and Nongalactic Astrophysics

The SKA View of the Sunyaev-Zeldovich Effect from Massive Cosmic Halos

Yvette C. Perrott, Luca Di Mascolo, Rémi Adam et al. (+4 more)

The thermal intracluster medium (ICM) can be observed via its interaction with Cosmic Microwave Background photons, known as the Sunyaev-Zeldovich (SZ) effect. This effect produces an observable signal at radio to sub-mm wavelengths which probes the pressure of the ICM. The SKA will be sensitive to the thermal SZ effect in its highest frequency band, 5b. In this Chapter, we show that the SKA will provide a high-resolution, high-sensitivity view of the thermal SZ effect, allowing detailed observations of pressure substructures in clusters while retaining sensitivity to the large-scale global ICM emission.
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All authors Yvette C. Perrott, Luca Di Mascolo, Rémi Adam, Chiara Ferrari, Keith J. B. Grainge, Matthias Hoeft, Mamta Pandey-Pommier

Astrophysics of Galaxies

Predicted Capabilities of the SPRITE SmallSat for a Low-Redshift Lyman Continuum Emission Survey

Yi Hang Valerie Wong, Brian Fleming, Elena Carlson et al. (+13 more)

Ionizing Lyman continuum (LyC; $\lambda < 912~\rm{\mathring{A}}$) radiation from low-redshift ($z \sim 0.3$) galaxies provides crucial insight into the processes that contributed to cosmic reionization. While the James Webb Space Telescope has observed galaxies at redshifts as high as $z \sim 14$, detecting LyC beyond $z \sim 3$ is challenging due to absorption by neutral hydrogen in the intergalactic medium (IGM). Low-redshift LyC emitters (LCEs), therefore, act as proxies for their high-redshift counterparts, enabling direct measurements of LyC escape fractions with reduced IGM interference. These observations allow detailed ancillary studies of galaxy properties and the mechanisms driving ionizing photon escape, which cannot be directly observed at the Epoch of Reionization. This paper examines the capabilities of the Supernova remnants and Proxies for Re-Ionization Testbed Experiment (SPRITE) SmallSat, designed to study LyC emission from star-forming galaxies at $0.16 < z < 0.4$. SPRITE uses advanced mirror coatings and a highly sensitive far-ultraviolet imaging spectrograph, enabling it to probe LyC from galaxies that have been difficult to study with prior and existing instruments. To assess SPRITE's predicted performance in LyC studies, we select eight previously confirmed LCEs from the Low-redshift Lyman Continuum Survey as commissioning targets. Observations of these commissioning LCEs will validate SPRITE's LyC sensitivity and characterize its detection limits. This will enable the broader SPRITE low-redshift LCE survey, which will provide new constraints on the physics of LyC escape and help bridge the gap between low- and high-redshift LyC studies. SPRITE will also inform the design and scientific potential of future Lyman-UV missions, including the Habitable Worlds Observatory.
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All authors Yi Hang Valerie Wong, Brian Fleming, Elena Carlson, Briana Indahl, Dmitry Vorobiev, Sebastian Escobar, Kevin France, Maitland Bowen, Dónal O'Sullivan, Anne E. Jaskot, Jason Tumlinson, Sanchayeeta Borthakur, Michael J. Rutkowski, Stephan McCandliss, Ravi Sankrit, John O'Meara

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Primordial black hole formation in bulk-viscous cosmology

Zi-Yan Yuwen, Cristian Joana, Shao-Jiang Wang et al. (+1 more)

We investigate primordial black hole (PBH) formation in a cosmological background with bulk viscosity. Using numerical simulations, we determine the collapse threshold and the resulting PBH mass. We find that the critical threshold $\mu_c$ retains a dependence on the equation-of-state parameter $w$ similar to that in the inviscid case, but is enhanced by an amount comparable to the bulk-viscosity strength $\epsilon$. For fixed $w$, the increase in $\mu_c$ is approximately linear in $\epsilon$. By fitting the standard critical-scaling law for near-threshold collapse, we find that the bulk viscosity leads to an enhancement in the resulting PBH mass. These results indicate that bulk viscosity can systematically modify both the PBH threshold and PBH mass scaling law in the early Universe.
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All authors Zi-Yan Yuwen, Cristian Joana, Shao-Jiang Wang, Rong-Gen Cai

Astrophysics of Galaxies

UV Star-Formation Rates of the SHIELD Dwarf Galaxies

David G. Gormanous, Anjali S. Dziarski, John J. Salzer et al. (+11 more)

The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) is a multi-wavelength observational project targeting gas-rich, star-forming dwarf galaxies at the faint end of the HI mass function. We present near-ultraviolet (NUV) and far-ultraviolet (FUV) flux measurements obtained from GALEX survey images and use these fluxes to derive FUV star-formation rates (SFRs) for all 75 SHIELD galaxies with GALEX data. This paper represents the first published analysis that makes use of the full SHIELD sample. We compare the FUV SFRs to a variety of physical quantities to better understand the nature of SHIELD galaxies. When comparing the H$\alpha$ SFRs to the FUV SFRs for SHIELD and other local galaxy surveys, we confirm and solidify previous results that show that H$\alpha$-based SFRs for dwarf galaxies can grossly underestimate the true rate of star formation, emphasizing the highly stochastic nature of star formation in extremely low-mass galaxies. We further show that FUV SFRs appear to be robust tracers of star formation down to the very lowest galaxy masses included in this study. We show that baryonic mass is the best mass-related tracer for the prediction of the FUV SFR of the galaxies in our sample. Not surprisingly, the SHIELD dwarf galaxies exhibit long gas-depletion timescales and large gas mass fractions: fully 68% of the SHIELD galaxies have gas masses that are larger than their stellar masses.
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All authors David G. Gormanous, Anjali S. Dziarski, John J. Salzer, John M. Cannon, Steven Janowiecki, Nathalie Haurberg, April Horton, Elizabeth A. K. Adams, Martha P. Haynes, Myles J. Klapkowski, Joshua R. Marine, Kristen B. W. McQuinn, Katherine L. Rhode, Evan D. Skillman

Solar and Stellar Astrophysics

Dust Formation in Common Envelope Binary Interactions – III. Lightcurves

Chunliang Mu, Orsola De Marco, Luis C. Bermúdez-Bustamante et al. (+6 more)

Luminous red novae are transient events thought to arise from common envelope binary interactions. In this paper, we perform post-processing light-curve calculations for two, 3D hydrodynamic simulations of common envelope events. These simulations model interactions between 1.7 $M_\odot$ and 3.7 $M_\odot$ asymptotic giant branch stars and a 0.6 $M_\odot$ compact companion, including dust nucleation. In both our simulations, which are carried out for 44 years under adiabatic conditions, we observe a bright, hot peak lasting $3-5$ years, primarily due to the expansion of the photosphere before and during inspiral. Additional peaks can be seen appearing at different times and for different viewing angles, due to the asymmetry of the interaction. Dust forms about $1-3$ years after the beginning of the simulated interaction and shortly afterwards we witness a sharp decline in the bolometric luminosity, followed by a partial recovery and a plateau with an effective temperature of $\sim$400 K. The dust photosphere reaches a size of $\sim$250 au by the end of the simulations, but we predict that between 100 and 200 years, the dust will become optically thin at visible wavelengths, revealing an inner, warmer photosphere. The lightcurves obtained have two, well-quantified, but large uncertainties: insufficient surface resolution primarily affecting the first 1-2 years of the simulated lightcurves and the adiabatic assumption that affects primarily the later years. We finally contextualise our simulations within a group of observed luminous red nova transients, drawing particular attention to the outburst of OGLE-2002-BLG-360 and AT 2025abao, which are the closest match to our simulation.
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All authors Chunliang Mu, Orsola De Marco, Luis C. Bermúdez-Bustamante, Ryosuke Hirai, Daniel J. Price, Lionel Siess, Miguel González-Bolívar, Mike Y. M. Lau, Nadejda Blagorodnova

Earth and Planetary Astrophysics

A semi-analytic model of the bouncing barrier for protoplanetary dust aggregates

Sota Arakawa, Haruto Oshiro, Yuki Yoshida et al. (+1 more)

Collisional bouncing limits the growth of dust aggregates in protoplanetary disks, but its dependence on aggregate size, collision velocity, and filling factor remains poorly understood. Here we develop a semi-analytic model for the sticking probability of colliding dust aggregates. We divide each aggregate collision into two phases: a compression phase and a separation phase. The compression phase is described with an elastoplastic contact model, which determines the maximum contact radius and repulsive energy after compression. The separation phase is treated as fracture of a stochastic network of interparticle bonds, whose fracture energy is evaluated using weakest-link statistics. The model naturally predicts that larger aggregates bounce more readily because larger contact regions are more likely to contain weak bonds. Comparison with distinct element method simulations shows that the model reproduces the simulated sticking–bouncing boundary. Furthermore, applying the calibrated model to moderately porous aggregates inferred from ALMA observations of protoplanetary disks, we find that the predicted bouncing barrier passes through the observationally inferred size–velocity range. Thus, our semi-analytic model provides a useful framework for predicting the collisional evolution of protoplanetary dust aggregates.
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All authors Sota Arakawa, Haruto Oshiro, Yuki Yoshida, Kiwamu Yoshii

High Energy Astrophysical Phenomena

Hunting for extreme high-energy-peaked BL Lacs: Rare to find and difficult to classify

Loredana Bassani, Raffaella Landi and Nicola Masetti

We explore the possible existence of a new population of BL Lacs, called ultra extreme high-energy-peaked BL Lacs (UEHBLs), whose synchrotron emission component peaks in the MeV band. In particular, we analysed Swift/XRT follow-up observations of a set of 10 hard X-ray sources from the Swift/BAT catalogues which were suggested to represent the first observational hints of this new blazar population on the basis of their spectral properties. We find that 6 of these candidate UEHBLs can be classified as line-emitting active galactic nuclei (AGNs), 4 of which are of type 2 and X-ray absorbed objects, while 2 are type 1 AGN and X-ray unabsorbed sources. In one more case, we find that the hard X-ray emission is probably the contribution of two line-emitting AGN, i.e. a Seyfert of type 1.9 and another of type 2. All these 7 classifications exclude the possibility that these hard X-ray sources are extreme BL Lacs. Of the remaining 3 UEHBL candidates, only 2 objects are found to have a spectral energy distribution (SED) compatible with those expected by MeV-peaked BL Lacs: however, in one of these 2 cases, an alternative Galactic association is also possible. The third source is instead likely associated with a more classical quasi-stellar object. Overall, we find that UEHBLs are extremely rare to find and probably very difficult to classify. Nevertheless, they represent a viable alternative classification for hard X-ray sources displaying no obvious or very weak counterparts.
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Wednesday 24 June

Solar and Stellar Astrophysics

Nautilus: Fast Time-Resolved Spectroscopy of GKM Stellar Flares and Their Implications for Planetary Habitability

Chia-Lung Lin, Adina D. Feinstein, Jeff Valenti et al. (+10 more)

Low-mass GKM dwarfs are prime targets for finding habitable-zone Earth-sized planets, but their frequent flares, especially on M~dwarfs, can strongly affect planetary atmospheres through enhanced UV/XUV radiation and stellar proton events, which can drive complex photochemistry and accelerate atmospheric escape. Current atmospheric and habitability models of planets around low-mass stars often rely on simplified flare inputs, such as fixed-temperature blackbodies or approximate optical-to-UV/XUV conversions. However, recent observations show that M~dwarfs' flare temperatures and spectral shapes can vary significantly with flare energy, phase, and stellar type, and that optical-based flare observations may underestimate the flare energy in the UV. Time-resolved spectroscopic flare observations of G- and K-dwarfs also remain rare compared to those of M dwarfs. Here, we propose that the Nautilus Space Observatory concept can provide a unique opportunity to obtain fast-cadence, precisely flux-calibrated, moderate-resolution NUV-to-NIR spectroscopy of flares across a large sample of GKM dwarfs. These observations will measure the time-dependent flare energy budget from the near-UV/blue continuum to the optical and near-infrared continuum, while resolving key chromospheric lines that trace the underlying flare physics. We aim to construct a statistical library of empirical flare spectral templates organized by flare and stellar properties, including flare energy, flare phase, and host-star spectral type. This library will provide a practical bridge between observed stellar flare properties and the radiation inputs required for planetary atmospheric evolution and habitability simulations.
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All authors Chia-Lung Lin, Adina D. Feinstein, Jeff Valenti, Mark S. Giampapa, Dániel Apai, Julien de Wit, Valeriy Vasilyev, Alexander Shapiro, Prajwal Niraula, Benjamin V. Rackham, Noah Tuchow, Ana Glidden, Nadiia Kostogryz

High Energy Astrophysical Phenomena

Nuclear Isomers and Their Impact on Gamma-Ray Emission in Binary Neutron Star Mergers

M. C. Babiuc Hamilton, A. P. Gross and O. T. Odney

The multi-messenger observations of GW170817 have provided strong evidence that binary neutron star mergers are a site of heavy-element production through the rapid neutron capture process. The decay of unstable $r$-process nuclei produces a significant number of $\gamma$-rays, which not only power the associated kilonova, but may also be observable in current and future $\gamma$-ray observatories, providing a direct probe of the nuclei synthesized. Current models of the emitted $\gamma$-rays link a nuclear reaction network with individual decay spectra. Typically, only the population of the ground state of the nuclei is tracked in the reaction network, and rapid de-excitation of the daughter nuclei is assumed when calculating the decay spectra. This may not be accurate in nuclei where there are longer-lived, high-energy nuclear isomers. In this work, we relax these assumptions, modeling the dynamic behavior of nuclear isomers for a select list of nuclei. These isomers are included as independent states in the network, with temperature-dependent effective transition rates between ground and isomeric states and $\beta$-feeding probabilities calculated using the nuclear level structure. We estimate the $\gamma$-ray flux from isomeric transitions, finding that the 743.3 keV line of Nb-97m and the 555.6 keV line of Y-91m may be detectable in $\gamma$-ray observatories such as COSI, AMEGO, and LOX at galactic distances. These results, calculated for a small fraction of nuclei with isomers, highlight the need for the robust inclusion of nuclear isomers in nuclear reaction networks, as well as careful modeling of the resultant $\gamma$-ray spectroscopy to characterize observational signals.
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Astrophysics of Galaxies

Columba: isolated dwarf galaxy populations in diverse cosmological environments simulated with a cold interstellar medium

Jemima M. Briggs, Azadeh Fattahi, Robert A. Crain et al. (+7 more)

We introduce a suite of LambdaCDM cosmological, hydrodynamical simulations that track the evolution of a large population of dwarf galaxies. The suite comprises zoom-in simulations of 25 spherical, under-dense regions of r=5cMpc, selected to span $\approx1.5$ dex in mean enclosed density, covering voids to filamentary structures, whilst excluding haloes of Milky Way-mass or larger. The simulations achieve a mass resolution of $\sim 10^5$ solar masses with a galaxy formation model including cold, dense interstellar gas and whose subgrid stellar feedback efficiency reproduces the z=0 galaxy stellar mass function. We investigate the impact of the cosmic environment on dwarf galaxy formation and evolution. We find that the 5 cMpc environment influences the normalisation of the halo and galaxy mass functions, but does not significantly affect the stellar mass - halo mass (SMHM) relation and halo occupation fraction for galaxies with $M_{\star}=10^6-10^9$ solar masses. Instead, host halo concentration, estimated from DM-only counterparts, is more important: both the fraction of haloes hosting a resolved galaxy and the scatter about the SMHM relation correlate positively with concentration. Owing to halo assembly bias, concentration also influences galaxy formation times, such that at fixed halo mass more concentrated haloes host galaxies that are both older and more massive. The offset from the mean SMHM relation also anti-correlates with $t_{90}$, the time at which 90 percent of a galaxy's stellar mass has assembled. These correlations between halo properties and galaxy star formation histories present testable predictions for forthcoming observational surveys.
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All authors Jemima M. Briggs, Azadeh Fattahi, Robert A. Crain, Yannick M. Bahe, Sylvia Ploeckinger, Matthieu Schaller, Alejandro Benítez-Llambay, Evgenii Chaikin, Alexander J. Richings, Joop Schaye

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

Massive boson stars: Waveform-based branch diagnosis with neural reconstruction

Bo-Xuan Ge

We investigate whether the dynamical merger branch of massive boson-star collisions can be inferred from the gravitational waveform without supplying the intrinsic source parameters. Using an existing equal-mass, head-on numerical-relativity catalogue, we construct branch-conditioned reduced-basis surrogates for the real $(2,0)$ and $(4,0)$ modes and perform parameter-blind waveform inference. On a frozen test set of 60 held-out samples, the correct branch is recovered for all samples using either mode, showing that the branch information is not confined to the dominant $(2,0)$ channel. The inference also recovers $|\phi_c|$ with a mean relative error of $4.30\%$ and selects the correct $\lambda$ from $\{10,50,100,300\}$ in $68.3\%$ of the test samples. These results demonstrate waveform-based branch and source-parameter inference within the present noiseless numerical-relativity catalogue.
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Cosmology and Nongalactic Astrophysics

Overview of 21cm Experiments at high redshift with SKAO

EoR/CD Science Working Group, Gianni Bernardi, Daniela Breitman et al. (+81 more)

We provide an overview of the eight SKAO Science Book chapters that motivate the Epoch of Reionisation and Cosmic Dawn experiments with SKA-Low. We describe the individual SKA-Low experiments and expected sensitivity - power spectrum, tomography, 21-cm forest, cross-correlations, building on the broad observational plan laid out in the 2015 SKA Science Book. Finally, we outline features of the telescope that will be critical for the success of EoR/CD science, e.g., beam apodization, substations, and multi-beaming.
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All authors EoR/CD Science Working Group, Gianni Bernardi, Daniela Breitman, Abhirup Datta, Anastasia Fialkov, Leon V.E. Koopmans, Adrian Liu, Yi Mao, Garrelt Mellema, Florent Mertens, Andrei Mesinger, Jonathan Pritchard, Aurel Schneider, Cathryn M. Trott, Yidong Xu, Anshuman Acharya, Satadru Bag, Rennan Barkana, Nichole Barry, Oliver Basquette, Michele Bianco, Stefanie A. Brackenhoff, Carlo Burigana, Isabella P. Carucci, Emilio Ceccotti, Arnab Chakraborty, Samir Choudhuri, Tirthankar Roy Choudhury, Benedetta Ciardi, Hector Afonso G. Cruz, Saswata Dasgupta, Kanan K. Datta, Pratika Dayal, Eloy de Lera Acedo, Khandakar Md Asif Elahi, Ivelin Georgiev, Sukhdeep Singh Gill, Sambit K. Giri, Adelie Gorce, Quan Guo, Caroline Heneka, Ian Hothi, Anne Hutter, Piyanat Kittiwisit, Bohua Li, Yashrajsinh Mahida, Barun Maity, Suman Majumdar, Avery Meiksin, Romain Meriot, Arnab Mishra, Shikhar Mittal, Rajesh Mondal, Lauro Moscardini, Julian Munoz, Satyapan Munshi, Pravin Kumar Natwariya, Leon Noble, Oscar Sage David O'Hara, Pierre Ocvirk, Samit Kumar Pal, Yannic Pietschke, Steven G. Piyanat, Rashmi Sagar, Rasha M. Samir, Mario G. Santos, Benoit Semelin, Rahul Shah, Yali Shao, Abinash Kumar Shaw, Hayato Shimabukuro, Peter H. Sims, Tomas Soltinsky, Guochao Sun, Anshuman Tripathi, Tiziana Trombetti, Ceren Ulusoy, Maio Umberto, Jochen Weller, Sarod Yatawatta, Shintaro Yoshiura, Bin Yue, Saleem Zaroubi, Qian Zheng

Solar and Stellar Astrophysics

A Spitzer Space Telescope Exploration Science Program to Search for Y Dwarf Variability

Michael C. Cushing, Jesica L. Trucks, Kevin K. Hardegree-Ullman et al. (+10 more)

We present the results of a Spitzer Space Telescope Exploration Science Program to search for and characterize variability in Y dwarfs. We observed 14 Y dwarfs over a 24 hr period at [3.6] and [4.5] and then repeated the observations a few months later. We add two Y dwarfs, WD 0806-661B and WISE J085510.83-071442.5, that were also observed with Spitzer so that our sample includes all Y dwarfs observed for variability with Spitzer. We infer variability fractions of 59%+-15% and 64%+10%-13% for [3.6], and [4.5], in the first epoch, and 35%+17% -11% and 75%+8% -15% in the second epoch. We also find that Y dwarf Spitzer light curves are generally stable over timescales of months, but in some cases can show clear changes in amplitude. Combining our results with a similar Spitzer survey of L and T dwarfs by Metchev et al. (2015), we find the mid-infrared variability fraction of L, T, and Y dwarfs weakly supports the hypothesis that brown dwarf variability is caused by variations in the horizontal and/or vertical structure of condensate clouds.
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All authors Michael C. Cushing, Jesica L. Trucks, Kevin K. Hardegree-Ullman, Adam J. Burgasser, Sean J. Carey, Jonathan J. Fortney, Christopher R. Gelino, John E. Gizis, J. Davy Kirkpatrick, Sandy Leggett, Gregory N. Mace, Mark S. Marley, Caroline V. Morley

Instrumentation and Methods for Astrophysics

In situ cryogenic characterization of proton damage in thick p-channel skipper CCDs

Brandon M. Roach, Brenda Cervantes Vergara, Alex Drlica-Wagner et al. (+14 more)

Skipper charge-coupled devices (CCDs) are an offshoot of standard silicon pixel detectors and are capable of performing repeated non-destructive charge measurements, enabling deeply sub-electron readout noise. This capability has opened the door to single-photon counting from the near-infrared ($\sim$1.1\,$\mu$m) to the soft X-ray (several keV), making these devices strong candidates for future astronomical instruments operating in the photon-starved limit. Furthermore, the p-channel architecture used to fabricate Skipper CCDs on n-type silicon has been demonstrated to have an increased hardness to the intense radiation environment of space. Building upon previous irradiation campaigns on room-temperature sensors, here we describe the first radiation-hardness tests of p-channel skipper CCDs at their cryogenic operating temperatures. We assess the performance of the floating-gate output stage and global CCD parameters (charge transfer inefficiency, dark current, hot pixels, and charge traps). We find that these devices maintain excellent performance after displacement damage doses equivalent to ${\sim}$10 years at the Earth/Sun L2 Lagrange point, demonstrating for the first time that these sensors remain radiation-hard in realistic deep-space thermal and radiation environments.
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All authors Brandon M. Roach, Brenda Cervantes Vergara, Alex Drlica-Wagner, Phoenix Alpine, Ana Martina Botti, Claudio Chavez, Julian Cuevas-Zepeda, Juan Estrada, Guillermo Fernandez Moroni, Nora Hoch, Stephen E. Holland, Blas Irigoyen Gimenez, Agustin Lapi, Santiago Perez, Nathan Saffold, Javier Tiffenberg, Yikai Wu

High Energy Astrophysical Phenomena

A Census of Variable and Transient Radio Sources Within High-Energy Neutrino Fields

Florian Rösch, Matthias Kadler, Roger P. Deane et al. (+3 more)

The origin of high-energy cosmic neutrinos detected by the IceCube observatory is a hotly debated topic in astroparticle physics. Neutrinos can be produced via interactions of high-energy protons with photons. There are multiple candidate source classes which can accelerate cosmic particles to the energies required to emit high-energy cosmic neutrinos and which have in common that they lead to variable/transient radio emissions. However, so far only a few active galactic nuclei (AGNs) could be associated with high confidence with IceCube neutrinos. The bulk of the diffuse neutrino flux might be emitted from a rather faint and numerous source population. The sub-mJy low-frequency radio sky may harbor these neutrino emitters that have gone unnoticed in previous searches. SKA-Mid continuum observations of high-energy neutrino fields will yield the most complete census of coincident transient and variable radio sources that might be associated with the neutrino emission. In previous MeerKAT observations of the IceCube gold alert IC240929A at 815 MHz, we detect about 550 faint radio sources inside the 90% uncertainty region of this neutrino field with flux densities between $169\,\mathrm{\mu Jy}$ and $140\,\mathrm{mJy}$. In its AA4 configuration, SKA-Mid will achieve about four times the sensitivity of MeerKAT, allowing for the detection of even fainter radio sources within such neutrino fields. By adding wide-field VLBI analysis of the fields under consideration, all neutrino-candidate radio sources can be tested for high brightness-temperature compact emission (indicative of an AGN classification) and milliarcsecond-scale resolved structures.
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All authors Florian Rösch, Matthias Kadler, Roger P. Deane, Philip G. Edwards, Karl Mannheim, Jack F. Radcliffe

Earth and Planetary Astrophysics

Two inner dust clumps in PDS 70. A third protoplanet traced by trojan material or a substructured inner disk?

O. Balsalobre-Ruza, V. Christiaens, N. Huélamo et al. (+18 more)

The PDS 70 cavity hosts two confirmed directly imaged protoplanets and a third inner planet candidate at 13au, labeled PDS 70 d. Despite its Keplerian motion, its unusually blue spectrum challenges a planetary interpretation. We further investigate the presence and nature of a third inner planet using new SPHERE and GRAVITY+ observations. Using the star-hopping strategy, we obtained coronagraphic IRDIS polarimetric observations in the H-band, and non-coronagraphic observations with IRDIFS in the YJHK-bands. We also searched for a planetary signal with GRAVITY in the 4UT configuration. We consistently detect two elongated inner emissions with SPHERE: the previously proposed planet candidate and another feature that appears to share the same orbit while leading it by ~120$^\circ$. Both features show dust-scattered-light spectra but different colors, possibly indicating different grain sizes. Such configuration is consistent with co-orbital dust accumulated at the stable Lagrangian regions of a distinct and yet undetected planet. GRAVITY yields a marginal (3$\sigma$) detection at the predicted location along the same orbit ($\rho=76.2\pm0.29$mas, PA=$226.50\pm0.21^\circ$), and consistent with a ~3$M_{\rm Jup}$ planet. This planet-like signal is aligned with a narrow shadow that we detect in the outer disk. We also detect polarized emission very close to the star likely arising from the inner disk. The apparent embedding of the two dust clumps within it motivates an inner-disk origin as an alternative scenario. We conclude that the previously reported third planet candidate traces a dust clump either trailing an unseen planet on the same orbit or a rotating substructure within the inner disk. Further observations are needed to test these scenarios. Confirming the new GRAVITY planet-like signal would support co-orbital substructures as indirect tracers of protoplanets.
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All authors O. Balsalobre-Ruza, V. Christiaens, N. Huélamo, I. Hammond, M. Benisty, S. Lacour, D. Blakely, R.G. van Holstein, J. Latour, J. Lillo-Box, Z. Wahhaj, D. Trevascus, O. Absil, J. Bae, C. Charalambous, I. de Gregorio-Monsalvo, A. Leleu, I. Mendigutía, C. Petrovich, Á. Ribas, S. Juillard

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

Thermodynamics of thin-shell wormholes

Francisco S. N. Lobo and Manuel E. Rodrigues

We develop a unified thermodynamic description of dynamic thin-shell wormholes, starting from the transparent (vacuum bulk) case and then relaxing the transparency condition to include bulk matter crossing the throat. For isolated shells, we show that the entropy is conserved under transparent evolution, $TdS=0$, which holds for arbitrary dynamical motion of the throat within the assumptions of the thin-shell formalism. When bulk matter is present, the generalised first law becomes $T\dot{S}=A\Phi$, where $\Phi$ is the net energy flux; entropy increases (decreases) when matter flows into (out of) the shell. Explicit expressions for the flux are provided for null dust and massless scalar fields, and quantum pair production (Hawking-like emission) is also discussed. A formulation of the generalised second law is presented, and it is consistent with standard thermodynamic expectations under conditions where heat flows from hotter to colder regions. As a concrete astrophysical application, we study accretion of null dust: the critical accretion rate above which the throat becomes dynamically unstable depends sensitively on the spacetime geometry and the shell equation of state, highlighting the environmental dependence of these configurations. Fluctuations in the energy flux induce a stochastic force on the throat dynamics, leading to a Langevin description with an associated fluctuation-dissipation relation. This results in diffusion of the throat radius and additional entropy production. The framework applies to a broad class of spherically symmetric thin-shell constructions within general relativity. Our results provide evidence that thin-shell wormholes admit a consistent thermodynamic description, quantify their sensitivity to accretion processes, and suggest possible avenues for probing exotic compact objects with future gravitational wave observations.
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Earth and Planetary Astrophysics

The Astrodynamics Primer on Cislunar and Translunar Space

Aaron J. Rosengren, Anjali Rawat, Bhanu Kumar et al. (+1 more)

The Earth-Moon environment is multiscale and strongly nonuniform, yet it is often discussed as a single cislunar regime. In reality, circumterrestrial space is partitioned by changes in perturbation hierarchy, by gateway topology, and secular and resonant structures that differ qualitatively across the domain. This paper develops a unified spatiographic description of that structure, combining perturbative theory, semi-analytical resonance cartography, restricted multi-body dynamics, and direct numerical mapping. The terrestrial-cislunar transition is sharpened through the Laplace radius, beyond which lunisolar torques overtake the classical oblateness-dominated picture. Earthward of the Moon, cislunar space divides into a secularly dominated inner zone and an outer zone structured by interior lunar mean-motion resonances. Near the Moon, circumlunar space forms a distinct dynamical enclave organized by the EM gateway geometry and the lunar SOI. Beyond the Moon, translunar space forms an outer circumterrestrial province in which the Moon acts as an interior perturber, the Sun remains an exterior perturber, and the resulting dynamics acquire a mixed lunisolar secular and resonant architecture before weakening outward toward heliocentric behavior. These results are synthesized through MEGNO and fate-class cartographies across six numerical map domains. The maps reveal where quasiperiodic confinement survives, where resonance overlap and gateway transport produce sticky residence and organized escape, and where solar forcing becomes a qualitative architectural ingredient. Placed alongside a curated catalog of satellites and debris, the framework provides a dynamical geography of this environments that clarifies the transitions among cislunar, circumlunar, and translunar motion and offers a more precise basis for interpreting stability, transport, and long-term Earth-bound behavior.
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All authors Aaron J. Rosengren, Anjali Rawat, Bhanu Kumar, Shane D. Ross

Instrumentation and Methods for Astrophysics

Extending the SKA Across Africa: The Case for a Continental African VLBI Network

Emmanuel K. Bempong-Manful, Jompoj Wongphechauxsorn, Jack Radcliffe et al. (+31 more)

The African continent holds the key to unlocking the full potential of global Very Long Baseline Interferometry (VLBI). Strategic placement of radio telescopes across Africa provides the crucial north-south and intermediate baselines that are currently missing from the global VLBI network. This expansion will dramatically enhance imaging fidelity and resolution. In this chapter, we propose a vision for a continental African VLBI Network (AVN) that will operate in close synergy with SKA-Mid, enabling transformational science across all cosmic scales. While only the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa and the Ghana Radio Astronomy Observatory (GRAO) are currently operational, several partner countries are in the process of refurbishing or converting existing antennas. Here, we advocate for the expansion of this network through the deployment of a limited number of SKA-Mid-type telescopes across the continent, creating an "African arm" of SKA-VLBI. With a maximum baseline of ~ 9000 km (from Rabat, Morocco to Cassis, Mauritius), the proposed continental facility will surpass for example, the resolution that will be achieved by the next generation Very Large Array (ngVLA) by ~ 10 % at similar observing frequencies and significantly enhance global VLBI coverage. Beyond the scientific and technical gains, the AVN represents a unique opportunity for sustainable growth in human capital, education, and innovation across Africa. Developing and operating a continental VLBI array will train the next generation of engineers, data scientists, and astronomers, stimulate local industry, and inspire public engagement in science and technology. We outline the current status, challenges, and potential roadmap towards realizing this vision, and we highlight how a continental African VLBI network will position Africa at the forefront of global radio astronomy.
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All authors Emmanuel K. Bempong-Manful, Jompoj Wongphechauxsorn, Jack Radcliffe, Melvin Hoare, Olga Bayandina, Pfesesani V. van Zyl, Cristina García-Miró, Candela Chico, Naomi Asabre Frimpong, Hans-Rainer Klöckner, Valente Cuambe, Carla S. Mitchell, Saul P. Phiri, Benedicta Woode, Emmanuel Proven-Adzri, Willice Obonyo, Tyler L. Bourke, Cristiana Spingola, Matthias Kadler, Ailing Wang, Roger P. Deane, Isabella Prandoni, Rocco Lico, James O. Chibueze, Robert Beswick, Simon Garrington, Benito Marcote, Tao An, Marcello Giroletti, Isaac M. Mutie, Anne-Kathrin Baczko, Johannes Allotey, Stefano Giarratana, Rasha M. Samir

Earth and Planetary Astrophysics

Predictions of Transiting Exoplanet Confirmations from Rubin LSST Surveys

Suber Corley, Eric Feigelson, Claudio Caceres et al. (+2 more)

We assess the prospects for exoplanet transit observations in the 10-year Wide Fast Deep (WFD) and Deep Drilling Field (DDF) surveys within the Legacy Survey of Space and Time (LSST) mission of the Vera C. Rubin Observatory. We construct a framework for systematic assessment of expected exoplanet yields, highlighting the principal limitations imposed by the survey observing strategy and cadence. We simulate light curves with a wide range of exoplanetary system models derived from planet occurrence rates developed with data from the Kepler mission. Transit counts for the stellar population are calculated using the TRILEGAL Galactic structure model, incorporating telescope sensitivity and survey cadences. We apply the constraints that the full duration of at least three transits must be observed and that the signal-to-noise ratio will support detectability. The observations were then validated using the Transit Least Squares periodogram. Our findings indicate a limited potential for exoplanet confirmations under the current survey design. Only a small number of hot planets orbiting faint M class main sequence stars will be confirmed in the DDF fields. The WFD survey is projected to produce no confirmations. These findings underscore the constraints imposed by the sparse, multi-band observing strategy, which prioritizes cosmology and extragalactic science over the continuous photometric coverage required for confirmations.
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All authors Suber Corley, Eric Feigelson, Claudio Caceres, Bolivia Cuevas-Otahola, Andjelka Kovacevic

Astrophysics of Galaxies

Probing the Nature of Lyman Continuum Emitting and Low-metallicity Galaxies Using the SKA

Omkar Bait, Daniel Schaerer and Mark Sargent

The sources responsible for cosmic reionization remain a key open question in observational cosmology. Recent JWST results increasingly suggest that low-mass star-forming galaxies (e.g., compact starbursts and strong emission-line systems) dominated the ionizing photon budget. The physical mechanisms driving Lyman continuum (LyC) photon escape, including supernova, radiative, and cosmic-ray feedback, and the origin of extreme ionization conditions, remain poorly understood. Radio continuum (RC) emission, a well-established star-formation tracer in normal galaxies, is not yet well characterized in such extreme systems, which exhibit high star-formation rate densities, young stellar populations, low metallicity, and hard ionizing spectra. Targeted mid-frequency ($1-15$,GHz) observations with SKA precursors have begun probing low-redshift LyC emitters (LCEs), revealing links between RC spectral index, LyC escape fraction, ionization conditions, metallicity, and SFR surface density, alongwith deviations from the canonical RC$-$SFR relation. The higher sensitivity of the SKA Array Assemblies across Bands $\sim 1-5$ will enable systematic studies of fainter LCEs and low-mass, metal-poor galaxies. We present number density predictions for LCE candidates at $z \sim 1$-$3$, showing that SKA-Mid surveys can assemble samples of $\sim10-100$ candidates per square degree over a star-formation rate range of $1-100$,$M_{\odot}$yr$^{-1}$, making a dedicated SKA Large Programme scientifically feasible. With the full SKA, in synergy with JWST and next generation telescopes, multi-wavelength analyses will robustly constrain the thermal and non-thermal RC components and cosmic-ray energy spectra, providing critical insights into the feedback processes governing LyC escape and star formation in the early universe.
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