Instrumentation and Methods for Astrophysics
The influence of standard relativistic effects on Gaia-like astrometric catalogs
Gabriel Rodríguez-Moris and Sergei A. Klioner
With the observational accuracy of astrometric space
telescopes such as Gaia, the Newtonian theoretical framework for positional astronomy is no longer appropriate. To model all effects relevant at the corresponding levels of accuracy, a more sophisticated description in the framework of General Relativity is required. It is generally known how various relativistic effects affect a given astrometric observation. In particular, the maximal light deflection of a given Solar System body can be easily estimated for a given observer. However, astrometric parameters for a given source are computed from a series of observations of that source. Depending on the relativistic effect, the fraction of observations affected, at some given level of accuracy, by that relativistic effect can vary and also be very small. Our goal is to investigate the impact of unaccounted relativistic effects on the astrometric parameters of a source observed by a Gaia-like astrometric
telescope. The standard relativistic framework for Gaia is used to highlight such effects in some cases where they are most significant. Then, using the simulation tool AGISLab, we fit a set of Gaia-like observations of a given number of sources to the standard Gaia-like astrometric model for astrometric source parameters, but using different incomplete relativistic models. In this way we obtain the errors of the astrometric parameters if one were to drop different elements of the relativity model. A simplified analytical description of the errors is also provided and discussed. We demonstrate that, due to averaging over many observations per source, the errors in the astrometric parameters are drastically smaller than the corresponding relativistic effects in individual observations. This opens a way to potentially simplify the relativistic model for future astrometric projects aiming for higher accuracy than Gaia.
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Cosmology and Nongalactic Astrophysics
Simulation Tests of PSF Modeling for Cosmic Shear with the Vera C. Rubin Observatory
Claire-Alice Hébert, Erin S. Sheldon, Tianqing Zhang et al. (+3 more)
Exceptional control of systematic effects is required in order to achieve unbiased
cosmic shear two-point correlation function measurements with the next generation of
galaxy imaging surveys, such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). One critical challenge is accurately modeling the point-spread function (PSF), as errors in PSF estimation can introduce spatially correlated biases in
galaxy shape measurements. The LSST Science Pipelines, which will be used to process Rubin data, include an implementation of the PIFF (PSFs in the Full Field of View) package originally developed for, and demonstrated to perform well on, DES-Y3 and Y6 data. In this work we use semi-realistic image simulations, mimicking LSST observing conditions in $i$-band over 100 square degrees, to perform an end-to-end test of the Rubin PSF modeling pipeline. PSF model residuals are quantified using both second- and fourth-order moment parameters and performance is evaluated, for both LSST year 1 and year 10 depth, with a series of diagnostic tests. We find that the additive bias contribution from PSF modeling errors to the non-tomographic
cosmic shear data vector is well below 30% of the
cosmic shear uncertainty estimated from our analytic covariance
matrix. Though our simulations exclude several known effects that may further challenge PSF modeling, these results demonstrate promising performance from PIFF on LSST-like data and provide an early
benchmark for ongoing PSF validation efforts for LSST weak
lensing analyses.
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All authors Claire-Alice Hébert, Erin S. Sheldon, Tianqing Zhang, Joachim Harnois-Déraps, Mike Jarvis, the LSST Dark Energy Science Collaboration
High Energy Astrophysical Phenomena
Galactic Electron-Positron Annihilation Emission from X-Ray Binaries with Transient and Persistent Jets
Argen Gian Detoito and Henric Krawczynski
The Galactic Center exhibits a persistent 0.511 MeV emission characteristic of electron-positron annihilation. Various astrophysical sources may be responsible for supplying the positrons, yet their contributions with respect to the total annihilation rate is uncertain. X-ray binaries have historically been a primary candidate, possibly contributing a significant fraction of the Galactic positrons. X-ray binaries can produce positrons through the Blandford-Znajek mechanism, two-
photon pair production in the corona, and/or one-
photon pair production for strongly-magnetized compact objects. These positrons may then be channeled into the Interstellar Medium through jets or winds. In this work, we argue that X-ray binaries cannot contribute to the electron-positron annihilation flux alone. We present 0.511 MeV line fluxes and all-sky maps produced by X-ray binaries and stellar
flares from the Galactic stellar population, along with the gamma-ray continuum from positrons produced by X-ray binaries. To do so, we solve the particle transfer equation using Green's functions. The total morphology is slightly asymmetric towards negative longitudes and positive latitudes. We find five 0.511 MeV flux hotspots in the generated all sky maps and scrutinize the contribution of individual sources to these hotspots. Observations of these hotspots can reveal the contribution of X-ray binaries to the Galactic positrons. The upcoming Compton Spectrometer and Imager (COSI) mission could image a hotspot near Cygnus X-1. The detection of the other hotspots requires a
telescope with improved arcminute angular resolution.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Kerr-Newman and genuine Kerr black holes in the Bertotti-Robinson magnetic field
Hryhorii Ovcharenko and Jiri Podolsky
We present a spacetime that describes a rotating and charged black hole immersed in an external
magnetic field. This exact solution to the Einstein-Maxwell equations has a surprisingly simple form which reduces to standard Kerr-Newman metric, and to the uniform Bertotti-Robinson
magnetic universe. We show that the Kerr-BR solution presented in [Phys. Rev. Lett. 135, 181401 (2025)] has a special charge, and we identify a genuine Kerr black hole without any charge, in the
magnetic field. In the weak-field limit it gives the Wald solution. We analyze main physical properties of the new family, namely singularities, horizons, regularity of axes, charges,
entropy and temperature.
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Instrumentation and Methods for Astrophysics
Image persistence flagging for SPHEREx
Candice Fazar, C. Darren Dowell, Brendan P. Crill et al. (+3 more)
Image persistence in HAWAII-2RG HgCdTe detectors has been observed by multiple parties. Also known as latent signal, this effect occurs when sensor images following an illumination show a decayed form of the illuminated image even though the source has been removed and the detector has been reset. Using data from an engineering grade detector array delivered for SPHEREx testing illuminated with a wide range of fluxes, we demonstrate an interpretation and a working model from which the decaying signal can be estimated, providing the ability to flag pixels subject to excess persistence current beyond a specified threshold. Simulated persistence images allow validation of the module and prediction of its effect in flight data.
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All authors Candice Fazar, C. Darren Dowell, Brendan P. Crill, Phil Korngut, Chi Nguyen, Howard Hui
High Energy Astrophysical Phenomena
When the stars don't align: Investigating inconsistencies in binary black hole formation across population synthesis codes
Alexandra G. Guerrero, Michael Zevin, Duncan B. Maclean et al. (+4 more)
Binary population synthesis (BPS) codes are valuable tools for investigating the end-to-end lives of binary
stars as well as a myriad of observed astrophysical phenomena. Many “rapid" BPS codes rely on semi-analytical single-
star evolutionary tracks and disjointed prescriptions for binary physics. Updated “hybrid" or “detailed" BPS codes incorporate improved methodologies, but at a steeper computational cost that may limit broad exploration of physical uncertainties. Given the widespread use of BPS in modern astrophysical research, it is imperative to systematically compare BPS codes across the spectrum of computational efficiency, flexibility, and physical realism to gauge their consistency and robustness. In this work, we perform BPS on three single-
metallicity populations of identical initial binaries using three modern codes — the rapid code $\texttt{COSMIC}$, the hybrid code $\texttt{METISSE}$ integrated into $\texttt{COSMIC}$, and the detailed code $\texttt{POSYDON}$ — ensuring consistent physical parameterizations where possible. We find stark differences in the properties, formation pathways, and progenitors of binary black hole (BBH) merger populations across the three codes. In a population of one million binaries at $0.01 Z_\odot$, each code results in $\sim 5,000\mbox{--}9,000$ BBHs that merge within a Hubble time. However, $\lesssim 14\%$ of progenitors overlap between two codes, and only $\textit{one}$ initial binary becomes a BBH merger across all three codes. Identical progenitors often follow different evolutionary pathways in each code and result in inconsistent BBH properties. Our results highlight the need for a deeper understanding of physical and computational differences between BPS codes and caution against over-interpreting results from any individual BPS code.
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All authors Alexandra G. Guerrero, Michael Zevin, Duncan B. Maclean, Katelyn Breivik, Carl L. Rodriguez, Max M. Briel, Daniel E. Holz
Astrophysics of Galaxies
Supernovae Ia ejecta velocities and host galaxy environments: the role of survey-selection effects
L. V. Barkhudaryan, A. A. Hakobyan, M. H. Gevorgyan et al. (+6 more)
The origin of the near-maximum-light Si II $\lambda$6355 velocity diversity among
supernovae Ia (SNe Ia) remains uncertain. Previous studies have suggested that high-velocity (HV) and normal-velocity (NV) SNe Ia occupy systematically different host
galaxy environments, implying differences in their progenitor populations. We re-examine this hypothesis using a sample of 354 nearby ($z\leq0.04$) spectroscopically normal SNe Ia, comprising 239 NV and 115 HV events, identified in targeted and untargeted surveys. For each SN, we determine the host
galaxy morphology, galactocentric distance, and physical size, and obtain homogeneous stellar mass estimates while assessing the influence of survey-selection effects. The Si II velocity distribution is well described by two Gaussian components, confirming the NV and HV populations. We find no statistically significant differences between the galactocentric distance, host
galaxy size, or stellar mass distributions of the two velocity subgroups. The environmental trends reported in previous studies are recovered only with marginal statistical significance in the targeted subsample, whereas they disappear almost entirely in the untargeted subsample, consistent with survey-selection effects playing a major role in the previously inferred environmental differences between the NV and HV events. Our results weaken the interpretation that the observed Si II velocity diversity is primarily driven by systematic differences in the global host properties examined here. Instead, they favour a scenario in which intrinsic explosion asymmetries and viewing-angle effects account for a substantial fraction of the observed velocity diversity, without excluding a possible contribution from local environmental conditions or progenitor properties.
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All authors L. V. Barkhudaryan, A. A. Hakobyan, M. H. Gevorgyan, D. Kunth, G. A. Mamon, U. Burgaz, V. Adibekyan, Zh. R. Martirosyan, A. G. Karapetyan
High Energy Astrophysical Phenomena
Relativistic blob signatures in the M87 jet at sub-parsec scales
Donaldo Mora, Alejandro Cruz-Osorio, Erika Benítez et al. (+1 more)
In this work, we present results from general-relativistic radiative-transfer calculations of black hole
accretion and jet launching to reproduce the observed properties of the M\,87 jet at sub-parsec scales. For the first time, in the simulations we have included a blob component at the launching region of the jet that allowed us to reproduce the quasi-simultaneous low-energy spectral energy distribution ($10^{10} \text{ Hz} \leq \nu \leq 10^{16} \text{ Hz}$). Moreover, we obtain a better fit of the synchrotron emission in the self-absorption region ($\nu \leq 10^{11} \text{ Hz}$), showing that the inclusion of a blob component in our radiative transfer calculations results in a flatter spectrum ($\alpha_{22-86\ \text{GHz}}=0.08$). Additionally, our simulations improved the accuracy of the observed morphology of M\,87's jet, matching the data up to a distance of 0.6 mas from the core at 86 GHz. Our results reproduce the edge-brightened structure up to $\sim1.3$ mas, i.e., in a more extended region compared with previous studies, with a brighter southern edge. The obtained synthetic image of the jet reproduces additional observed
knots along the southern edge.
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All authors Donaldo Mora, Alejandro Cruz-Osorio, Erika Benítez, Yosuke Mizuno
Earth and Planetary Astrophysics
Assessing the Impact of High-Resolution Imaging on Statistical Validation of TESS Planet Candidates
Michael Collier, Steven Giacalone, Brian Derfer et al. (+38 more)
High-resolution imaging is widely used to constrain false-positive scenarios in
exoplanet validation, but it is a finite follow-up resource that reaches only a subset of candidates, and its population-level impact on validation outcomes has not been quantified through controlled removal experiments. Using an automated pipeline built on TRICERATOPS, we compute the false-positive probability (FPP) of 443 TESS
planet candidates. For the 264
planet candidates with high-resolution imaging observations, we compute FPP with and without the corresponding contrast curves, allowing us to quantify the impact of the additional data. We find that 72% of 68 contrast-curve bearing validated
planets would fail validation without their adopted contrast curves. The fraction requiring imaging decreases with increasing
planet size, from 100% below $1.7~R_\oplus$ to $33\%$ above $4~R_\oplus$: within our sample and TRICERATOPS-based analysis, the availability of high-resolution imaging directly limits the yield of small-
planet validation and the supply of validated targets for atmospheric characterization. Our analysis statistically validates 64 new TESS
planets with sizes spanning 0.94 to 7.83 $R_\oplus$ across hosts of spectral type M through F. Four of these are highly amenable to JWST observations based on the transmission and emission spectroscopy metrics, and each achieves validation only with its imaging constraint.
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All authors Michael Collier, Steven Giacalone, Brian Derfer, David R. Ciardi, Catherine A. Clark, Ian J. M. Crossfield, Sarah Deveny, Sergio B. Fajardo-Acosta, Elise Furlan, Emily A. Gilbert, Steve B. Howell, Adam L. Kraus, Rachel A. Matson, Joshua E. Schlieder, Julian C. van Eyken, David Baker, Khalid Barkaoui, Özgür Baştürk, Mario Basilicata, Izuru Fukuda, Akihiko Fukui, Mourad Ghachoui, Michaël Gillon, Emmanuel Jehin, Jerome de Leon, Luigi Mancini, Francesca Manni, Gabriel Murawski, Bob Massey, Luca Naponiello, Norio Narita, Justus Randolph, Roberto Zambelli, Richard P. Schwarz, Abderahmane Soubkiou, Gregor Srdoc, Chris Stockdale, Toshi Suganuma, Jiaqi Wang, Francis P. Wilkin, Selçuk Yalç{\i}nkaya
Astrophysics of Galaxies
The Milky Way Joins the Extragalactic World: I. PHANGS
Neal J. Evans II, Davide Elia, Jiayi Sun et al. (+2 more)
Complete catalogs of molecular clouds in the Milky Way allow analysis of the molecular medium and the
star formation properties of the Milky Way that closely follows the method used for nearby
galaxies, in particular in the PHANGS project. The dependencies of the depletion time on other properties of molecular gas in the Milky Way are similar to those of other
galaxies when analyzed in an analogous way. They exhibit a large scatter and relatively weak correlations. The strongest correlation is a decrease in depletion time with increasing velocity dispersion. We explore the effects of spatial resolution, sensitivity, cloud identificaton method, averaging method, and tracer choice on our results.
Metallicity effects in converting observations to mass can have a substantial impact. Somewhat fortuitously, differences in conversion methods between PHANGS and the Milky Way do not affect the current comparison. Inadequate spatial resolution, resulting in unresolved cloud structure, has the most important effect on interpretation of both extragalactic observations and existing catalogs of Milky Way clouds.
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All authors Neal J. Evans II, Davide Elia, Jiayi Sun, Sophia Stuber, Adam K. Leroy
Astrophysics of Galaxies
Beyond orientation: Evidence for distinct physical regimes among Little Red Dots and Little Blue Dots
L. Barrufet, J. S. Dunlop, M. L. Hamadouche et al. (+6 more)
Little Red Dots (LRDs) and Little Blue Dots (LBDs) may represent the same population of compact active galactic
nuclei (AGN) observed along different lines of sight. We test this scenario using a spectroscopic sample from the DAWN JWST Archive, selected based on common criteria for H$\alpha$ equivalent width, UV continuum slope, and compactness. We use the optical continuum slope to distinguish between samples of 89 LRDs and 191 LBDs spanning $1 \lesssim z \lesssim 7.5$, and compare their continuum properties, H$\alpha$ emission, and Balmer decrements. Consistent with previous studies, we find that LRDs exhibit broader H$\alpha$ profiles than LBDs systematically (with median FWHM values of $2319^{+71}_{-64}$ and $1424^{+56}_{-43}~\mathrm{km\,s^{-1}}$, respectively). We also confirm that LRDs show larger Balmer decrements, with median $\log_{10}(F_{\rm H\alpha}/F_{\rm H\beta})=1.01\pm0.03$, compared with $0.47\pm0.01$ for LBDs. Line-of-sight effects could explain both results. However, most significantly, we find that the LRD fraction increases strongly with H$\alpha$ line luminosity: LRDs are approximately six times more luminous in H$\alpha$ than LBDs. This robust finding is much harder to explain through unification with LBDs by orientation. Despite their higher line luminosities, LRDs have a moderately lower median H$\alpha$ equivalent width than LBDs, consistent with more of the raw emission being reprocessed into the rest-frame optical continuum in LRDs. These results, coupled with the systematically lower [O III]/H$\beta$ ratios found in LRDs and the decline of H$\alpha$ equivalent width towards the reddest optical slopes, disfavour a simple orientation-based link between LRDs and LBDs, and are instead more consistent with the predictions of gas-cocoon models in which increasing gas column density explains the apparent transition from LBDs to LRDs.
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All authors L. Barrufet, J. S. Dunlop, M. L. Hamadouche, M. Mezcua, D. Herrero-Carrion, M. Santos-Lleo, R. Gottumukkala, D. Spinoso, C. T. Donnan
Instrumentation and Methods for Astrophysics
On the performance of pre-trained vision transformers for supernova spectral classification using different spectral representations
J. Serrano Bell, P. Gálvez Molina, V. Contreras Rojas et al. (+4 more)
The spectroscopic classification of
supernovae is a key component of time-domain astronomy and plays an important role in the identification of Type Ia events. The increasing volume and diversity of spectroscopic data motivate the development of automated classification approaches. In this work, we explore the use of
Transformer-based
vision models for
supernova spectral classification, focusing on how different visual representations of spectra and fine-tuning strategies affect classification performance when image-based architectures are applied to intrinsically one-dimensional data. We consider a
dataset of 4,011
supernova spectra, augmented and rebalanced into three astrophysically motivated classes: normal Type Ia, other Type Ia subtypes, and core-collapse
supernovae. Spectra are encoded as line-plot images using direct flux-wavelength visualizations as well as alternative flux-difference versus wavelength-difference heatmap representations designed to emphasize differential spectral structure. We evaluate several pre-trained
Transformer architectures, including
Vision Transformers (ViT), Swin
Transformers, and a DINOv3-pretrained ViT, and examine the effects of fine-tuning depth, visual representation, and hyperparameter choices. We find that a plain flux-wavelength line plot outperforms the purpose-built maps on average, though log-scale maps remain competitive for specific architecture and fine-tuning combinations. On the held-out test set, our best model (vitb-p16) reaches a macro-F1 score of 86.3%, with per-class F1 scores of 94% for normal Ia, 77% for other Ia subtypes, and 88% for core-collapse
supernovae. The dominant misclassification arises from confusion between Ia-91T and normal Ia spectra. These results demonstrate that
Transformer-based
vision models can provide competitive performance for single-spectrum
supernova spectral classification.
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All authors J. Serrano Bell, P. Gálvez Molina, V. Contreras Rojas, W. Fox Fortino, M. Rojas, P. Protopapas, F. Bianco
Earth and Planetary Astrophysics
A Highly Reflective Atmosphere on the Lava World TOI-561b Revealed by JWST/NIRSpec Phase Curve
Samuel Boucher, Lisa Dang, Alex McGinty et al. (+15 more)
Ultra-short period (USP) rocky
planets are expected to be depleted of any substantial gaseous envelope due to the intense irradiation they receive from their host
star, making the recent detection of an atmosphere around TOI-561~b particularly surprising. That finding was based on the
planet's bulk density and dayside emission spectrum, but full-orbit phase curve observations offer a more comprehensive way to constrain the presence and characteristics of a
planet's atmosphere. In this paper, we map TOI-561~b's 3-5~$\mu$m emission using JWST/NIRSpec multi-orbit spectroscopic phase curves, explicitly accounting for the
curvature of the out-of-eclipse baseline and possible hotspot offsets. From a simple energy balance argument as well as comparing to general circulation models, we find the phase curve observations are best explained with high Bond albedo and moderate global heat transfer. Our 37-hour continuous observation provides a long baseline that allows us to model stellar granulation, the planetary phase curve, and dayside emission simultaneously, effectively disentangling these signals and yielding a dayside emission spectrum that is more robust against stellar variability and consistent with previous eclipse-only fits. Using general circulation model outputs, we constrain where clouds can plausibly form and test candidate compositions, finding that silicate clouds, such as SiO$_2$ and MgSiO$_3$, can form on the dayside near the terminator and explain the observed albedo. Our findings confirm that TOI-561~b appears to have a global reflective atmosphere, suggesting exchange of volatiles with the interior to maintain it.
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All authors Samuel Boucher, Lisa Dang, Alex McGinty, Johanna K. Teske, Raymond Pierrehumbert, Anjali A. A. Piette, Nicole L. Wallack, Angharad Weeks, Neil T. Lewis, Tim Lichtenberg, Mykhaylo Plotnykov, Emma Postolec, Daniel Huber, Timothy R. Bedding, Harrison Nicholls, Bo Peng, Mark Hammond, Diana Valencia
Astrophysics of Galaxies
EROSE: An algorithm searching for resolved Local Group satellites. The impact of combining different photometric bands on the detectability of Milky Way satellites in the LSST
Samuel Rusterucci, Nicolas F. Martin and Else Starkenburg
Systematic searches for ultra-faint Milky Way satellite
galaxies typically combine local density
estimators with colour-magnitude cuts, which are usually performed in 2D and have rarely, if ever, been extended to higher-dimensional spaces. These studies generally rely on $gri$ photometry, overlooking the shallower but metal-sensitive $u$ band. Entering the era of LSST, our study explores different $ugri$ combinations to determine which provides the best performance. We injected 36,000 dwarf
galaxies into the simulated data from the LSST Data Challenge 2 (DC2) and attempted to recover them using EROSE, a new fast multi-band search
algorithm designed to be easily applied to any survey and combination of photometric bands. We find that a multi-colour-magnitude space combining all three $gri$ photometric bands slightly outperforms, on average, the more commonly used colour-magnitude spaces combining only $gr$ or $ri$. The highest recovery fraction is achieved using a colour-magnitude space combining the $u$ and $g$ bands, recovering, on average, $64.1^{+6.3}_{-6.0}\%$ of the injected satellites. This improvement is particularly evident for the most extended systems, for which the additional colour information provided by the $u$ band improves our ability to isolate metal-poor member
stars from contaminating foreground populations. We estimate that the LSST will discover $\sim 50$ new Milky Way dwarf
galaxies, more than doubling the currently known number of satellites within its footprint. Combining the LSST photometric bands with a space-based
star/
galaxy separation could further improve these results, enabling the discovery of satellites at the low-mass end of the Milky Way's satellite
galaxy luminosity function and providing valuable constraints on dark matter models.
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Astrophysics of Galaxies
On the importance of the IGM/CGM enrichment in determining chemical abundances during the first 600 Myr
Annalisa Citro, Yong-Zhong Qian and Claudia Scarlata
JWST observations show that
galaxies at $z>8$ exhibit a wide range of carbon-to-oxygen (C/O) ratios at fixed
metallicity and systematically elevated nitrogen-to-oxygen (N/O) ratios compared to local
galaxies. Proposed explanations include finely tuned
star-formation histories (SFHs), differential or pristine inflows, top- or bottom-heavy initial mass functions, or enrichment from Wolf-Rayet
stars, supermassive
stars (SMSs), or Population III
stars. The observed abundances reflect both in situ production tied to the SFHs and earlier pre-enrichment of the intergalactic and circumgalactic medium (IGM/CGM), which supply the gas inflow that fuels
star formation. At such early epochs, SFHs are necessarily brief, and sustained
star formation requires inflows to dominate over outflows, making the chemical state of the IGM/CGM especially important. We develop a chemical
evolution model that incorporates (1) enrichment of the IGM/CGM by multiple sources and (2) the observed SFHs of high-
redshift galaxies. Applying this model to eight
galaxies at $z>8$, we find that only specific pre-enrichment scenarios reproduce their observed abundance ratios. For example, the low C/O and high N/O ratios measured in GN-z11 and CEERS-1019 require an IGM/CGM enriched by SMSs and pre-enriched to an oxygen
metallicity of $\sim10^{-5}$ of the solar value. We also find that the log(N/O) vs. 12 + log(O/H) plane provides more stringent constraints on enrichment pathways than the log(C/O) vs. 12 + log(O/H) plane. Overall, our results highlight the crucial role of IGM/CGM chemical composition in chemical
evolution models at $z>8$ and underscore the significant influence of SMSs on early carbon, nitrogen, and oxygen abundances.
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Instrumentation and Methods for Astrophysics
NestyNet. IV. Laws Chosen by Nothing in Advance
Rodrigo Ibata, Wassim Tenachi, Foivos Diakogiannis et al. (+2 more)
Differential-equation (DE) discovery tends to break down precisely where much of physics begins. Fields are coupled, governing laws are nonlinear in the state, amplitudes, coordinates, or operators of interest, yet derivatives must remain consistent across fields, channels, and differentiation orders. NestyNet-DE addresses this via two complementary DE search strategies, both employing analytic derivatives from segmented neural surrogates: a sparse-library route linear in the outer coefficients, and a new operator-factorized route that searches directly over equation structure rather than a fixed library, recovering compositional laws the sparse route misses. The recovered laws can be strongly nonlinear in states, fields, coordinates, and their couplings. The framework also handles multi-
dataset shared-support discovery, complex and vector laws, and
Hamiltonian discovery from phase-space trajectories. Beyond a law's form, the same data yield its geometry, the Lie point
symmetries of the recovered equation. We apply the pipeline to 30 years of daily ephemerides of $308$ main-belt asteroids and recover the reduced-Kepler hierarchy (areal law, inverse-square force, and reduced
Hamiltonian), where a discovered rotational
symmetry fixes the centrifugal coefficient rather than fitting it. We also present a
benchmark of 57 real-valued ODEs and 26 complex-valued systems, including the Schrödinger and Dirac equations, with Maxwell's equations as a coupled vector-PDE case study. Here, discovery is not shackled to a fixed library, nor does it end at the equation. It composes laws that no dictionary anticipated, and closes the loop from data, to a law chosen by nothing in advance, to the geometry that explains and integrates it.
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All authors Rodrigo Ibata, Wassim Tenachi, Foivos Diakogiannis, Neil Ibata, Anirudh Shankar
Instrumentation and Methods for Astrophysics
Radio Galaxies detection and characterization using deep learning techniques
Sanjay Khatik, Rohit Sharma and Pankaj Jain
Future
radio telescopes will generate data volumes that are increasingly difficult to analyse using traditional statistical methods, motivating the adoption of machine-learning techniques. In this work, we present YOLO-Chars (YOLO-based Detection and Characterisation of
Radio Sources), a two-stage deep-learning framework for the automated detection and characterisation of
radio galaxies in survey images. The framework is developed and evaluated using the Square Kilometre Array Science Data Challenge 1 (SKA SDC1)
dataset. In the first stage, customised YOLO-based multi-scale detection models are used to localise compact and extended sources across large sky maps. In the second stage, a dedicated source-characterisation network estimates the physical properties of the detected sources. We focus on three key parameters: flux density, angular size, and position angle. Our results show that YOLO-Chars achieves competitive detection and characterisation performance on the SKA SDC1
benchmark, demonstrating its potential as a scalable framework for next-generation
radio continuum surveys.
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Cosmology and Nongalactic Astrophysics
High-Energy Neutrino Constraints on memory burdened Bardeen and Kerr Primordial Black Holes
Md Riajul Haque and Suvashis Maity
The
quantum memory burden effect can suppress the late-time Hawking evaporation of primordial black holes (PBHs), allowing PBHs below the standard evaporation threshold of approximately $10^{15}\,\mathrm{g}$ to survive until the present epoch and potentially contribute to the dark matter abundance. We investigate primary and secondary
neutrino emission from
memory burdened Bardeen and Kerr PBHs, including Galactic and extragalactic fluxes and the effects of
memory suppression, Bardeen regularization, and Kerr rotation. We constrain their abundance using observations from IceCube, Super-Kamiokande, and ANTARES, together with the projected sensitivities of IceCube-Gen2, GRAND200k, and Hyper-Kamiokande. We find that Bardeen regularization and Kerr rotation produce qualitatively different effects. Increasing the Bardeen parameter suppresses the Hawking temperature and
neutrino flux, thereby weakening the abundance constraints. In contrast, rapidly rotating Kerr PBHs that retain a significant residual
spin at the onset of the
memory burdened phase can exhibit enhanced
neutrino emission and substantially stronger constraints. Increasing the
memory burden suppression index $k$ reduces the flux normalization but also allows lighter and hotter PBHs to survive, shifting the relevant signal toward higher energies. Consequently, HESE provides the leading sensitivity for weak suppression, whereas IceCube-Gen2 and GRAND200k become particularly important for stronger suppression. These results demonstrate the complementarity of current and future
neutrino observations in probing
memory burdened PBHs and the effects of regular geometry and rotation on their evaporation.
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Cosmology and Nongalactic Astrophysics
Diversity of Galaxy Centers from Small-Scale Isocurvature
Jessica N. Lopez-Sanchez and Wen Yin
The observed diversity of
galaxy centers motivates the possibility that the local dark matter composition may vary among
galaxies. In conventional multicomponent dark matter scenarios, however, large
stochastic variations in the relative abundances are not generically expected, with the cold component typically remaining dominant. We perform $N$-body simulations with a subdominant ultralight dark matter component carrying significant large-amplitude small-scale isocurvature perturbations. We find that although nonlinear
evolution largely homogenizes its fraction on galactic scales,ultralight dark matter can still be enhanced and even dominate the centers of small
halos because large initial ultralight dark matter fluctuations seed early potential wells that later form
halo centers. The ultralight-dominated region can extend beyond $0.01R_{\rm vir}$ and account for more than half of the central dark matter density, even for a cosmological ultralight dark matter fraction below $O(10\%)$. This central segregation provides a possible route to
stochastic cusp–core diversity, potentially explaining the observed diversity of
galaxy centers.
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High Energy Astrophysical Phenomena
VLASS Discovery of a Luminous Galactic Radio Transient Evolving on Decade Timescales
Jessie M. Miller, Gregg Hallinan, Dillon Dong et al. (+10 more)
We present a multiwavelength analysis of the
radio transient VT J1906+0849, discovered as a 70 mJy source in Epoch 1 of the Very Large Array Sky Survey (VLASS), 21 yr after an NRAO VLA Sky Survey (NVSS) non-detection.
Radio observations reveal the source was first detected in 2005, peaking at $\gtrsim200$ mJy in 2014, then declining until a late 2025 rebrightening. The transient sits at a Galactic latitude of $\approx0.74^\circ$ and the properties of its optical-infrared counterpart support a Galactic origin. At $d\gtrsim15$ kpc, the extreme
radio luminosity is likely powered by sustained
accretion onto a compact object. However, a Swift-XRT non-detection shows it is X-ray faint relative to the Galactic X-ray binary population, and the
radio emission is distinct from X-ray binaries in its temporal and spectral behavior. Broadband
radio spectra suggest synchrotron self-absorption, but size constraints from equipartition and very long baseline interferometry show little to no expansion in the
radio-emitting region over 5+ yr, despite significant spectral
evolution. Near-infrared spectroscopy reveals a single broad emission line with a stable centroid but variable width and luminosity. We attribute this feature to blueshifted Br$\gamma$ tracing a persistent asymmetric $\approx2000$ km s$^{-1}$ outflow. These properties are unlike any previously identified Galactic
radio source. One possible interpretation is that VT J1906+0849 is a young analog of the microquasar SS 433, with a dense disk wind confining a continuously powered synchrotron outflow. This jet-wind interaction explains the compact, slowly expanding
radio source and may contribute to the absence of bright X-ray emission.
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All authors Jessie M. Miller, Gregg Hallinan, Dillon Dong, Adolfo S. Carvalho, S. T. Myers, Jean Somalwar, Casey Law, B. M. Gaensler, Vikram Ravi, Laura Chomiuk, Assaf Horesh, Delina Levine, Yuyang Chen
Astrophysics of Galaxies
The Random Magnetic Field of the Milky Way
Michael Unger and Glennys R. Farrar
We constrain the large-scale isotropic random component of the Galactic
magnetic field using the Planck reconstruction of the 408 MHz synchrotron sky. Our analysis simultaneously fits the random-field structure, the synchrotron contributions of the coherent field and local foregrounds, and isotropic and dipolar offsets. A new element of the analysis is the use of excess polarized emission at 30 GHz to model local foregrounds, allowing us to retain 97% of the sky without absorbing these structures into
Galaxy-wide features of the
magnetic field. Across variations in the coherent-field model,
cosmic-ray electron distribution, sky mask, and field profile, we consistently find that the dominant random-field component is a vertically compact disk with a local rms strength of about 4 $\mu$G and a 1/e scale height of approximately 1 kpc, substantially thinner than in most previous models. An annular enhancement in the inner
Galaxy improves the fit to the data, whereas we find no evidence for either a large-scale spiral pattern or a thick random-field disk. The fits also yield an intensity monopole of 4-7 K, whose possible origin we discuss. We quantify the implications of the inferred random field for the angular smearing of ultrahigh-energy
cosmic rays. Compared with previous models, the sky-median smearing angle is smaller by up to a factor of 1.7, and by up to 2.4 in individual directions.
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Earth and Planetary Astrophysics
Does Cumulative XUV Unify the Neptunian Desert?
Qunfeng Jiang
The Neptunian desert is the scarcity of roughly $2$-$10\,R_{\oplus}$
planets on orbits of a few days. Atmospheric escape driven by stellar X-rays and extreme-ultraviolet (XUV) radiation may shape its lower boundary by stripping hydrogen-helium envelopes. Because M dwarfs and F-, G-, and K-type
stars have different activity histories, present bolometric irradiation may not trace the cumulative high-energy dose that drives escape. We ask whether cumulative XUV yields a common boundary across spectral type and whether the convergence survives
star-to-
star variation in age and rotation. Using 1850 Kepler and TESS
planets, Model for Rotation of
Stars (MORS) activity tracks, and a global boundary model, we find that the offset between M dwarfs and FGK
stars shrinks from $-1.065$ dex in bolometric flux to $-0.369$ dex for a common 5 Gyr median-rotation XUV history. Assigning plausible ages and initial rotations to individual hosts preserves the smaller XUV offset in every trial, with a median reduction of 69.1%. A common-period null yields comparable
alignment. Cumulative XUV therefore substantially reduces the host-type dependence, but the present data do not establish a universal XUV threshold independent of orbital period.
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Astrophysics of Galaxies
The [Ne V] AGN Diagnostic in SDSS-IV/eBOSS: An Anticorrelation Between Ionization State and AGN Luminosity in Low-Redshift Coronal-Line Galaxies
Owen S. Matthews Acuña, Christy A. Tremonti, Nikko J. Cleri et al. (+6 more)
Traditional narrow-line diagnostics fail at high
redshift, where low
metallicity drives
star-forming
galaxies and Active Galactic
Nuclei (AGN) into overlapping regions of the Baldwin-Phillips-Terlevich (BPT) diagram. Coronal lines, with ionization potentials exceeding 100 eV, offer a robust alternative: they cannot be produced by normal stellar populations, arise almost exclusively from AGN or fast shocks, and are insensitive to abundance
evolution. Among these, the [Ne V] doublet is the brightest optical coronal line tracer of AGN activity. Existing coronal line catalogs contain only about 1750 objects, too few to statistically assess the completeness and purity of [Ne V]-selected AGN samples. We identify 33,817
galaxies with [Ne V] S/N > 5 at z = 0.147-1.12 in the Sloan Digital Sky Survey IV extended Baryon Oscillations Spectroscopic Survey (SDSS-IV/eBOSS), exceeding the combined literature total by more than an order of magnitude. [Ne V] preferentially selects rapidly accreting, relatively unobscured AGN; only 41.5% of BPT AGN show detectable emission. By stacking spectra that lack [Ne V] on a grid of black hole mass and [O III] luminosity, we recover [Ne V] in the majority of bins, implying that non-detections reflect limited survey sensitivity rather than a deficit of coronal emission. We find [Ne V]/[Ne III] is only weakly correlated with [O III]/[O II].
Galaxies with high [Ne V]/[Ne III] for their [O III]/[O II] ratio have lower Eddington ratios and are more likely classified as LIERs or Composites. The [Ne V]/[O III] ratio shows a strong anticorrelation with [O III] luminosity, with the most extreme coronal-line strengths found among the lowest-luminosity AGN, in analogy with the
accretion states of stellar-mass black holes. Comparison with a sample of z=2-9 [Ne V]-detected
galaxies suggests some, but not all, high-
redshift AGN follow the same relations.
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All authors Owen S. Matthews Acuña, Christy A. Tremonti, Nikko J. Cleri, Kyle B. Westfall, Bee R. Erena, Jacob B. Stimac, Britt Lundgren, Drake Miller III, Aleksandar M. Diamond-Stanic
High Energy Astrophysical Phenomena
Generation of TeV Photons by PeV Neutrinos in Dense Astrophysical Environments
Jun-Chen Wang, Hanlin Song, Hao Li et al. (+2 more)
Recent observations by IceCube and KM3Net of PeV-scale ultra-high-energy (UHE)
neutrinos, together with detections of TeV-PeV
photons from various sources such as the Crab Nebula, the Galactic Center, and gamma-ray burst by ground-based observatories including Tibet AS$\gamma$, MAGIC, Carpet-3, and LHAASO, point to the existence of extreme astrophysical environments capable of accelerating particles to ultra-high energies. These findings motivate investigations of possible connections between UHE
neutrinos and
photons in such environments. Theoretically, dense regions surrounding compact objects can efficiently produce UHE
neutrinos. In this work, we calculate the production of UHE
photons from
neutrino-nucleon interactions, and note that if these interactions occur in the outer, optically thin regions of dense environments, the resulting
photons could potentially be observed. In our model, an incident
neutrino scatters off a nucleon, generating secondary partons that hadronize into pions and subsequently decay into UHE
photons. We calculate the resulting
photon energy spectra and find that for incident (anti)
neutrinos with energies above 1 PeV, the probability of producing
photons with energies exceeding 1 TeV is greater than 13%. As a concrete application, we show that this mechanism can quantitatively account for the preburst TeV
photons observed in GRB 221009A, providing a natural explanation for both their energies and lead times. These findings establish a plausible mechanism linking UHE
neutrino events to gamma-ray observations, providing new insights into hadronic processes in extreme astrophysical environments and supporting multi-messenger astronomy studies.
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All authors Jun-Chen Wang, Hanlin Song, Hao Li, Jie Zhu, Bo-Qiang Ma
Cosmology and Nongalactic Astrophysics
Model independent lensing sub-structure detection with multiply-imaged star clusters constellations
Leo W.H. Fung, Tom Broadhurst, Sung Kei Li et al. (+3 more)
A broad class of dark matter (DM) models predicts the existence of sub-structures residing in DM
haloes on sub-resolvable angular scales. Techniques to extract such a generic feature from diffraction-limited observations are lacking. In this work, we propose a model-independent 'super-resolving' method applicable to strong gravitational lens systems that is fully data-driven, without reference to any lens models. This method relies on a specific way of applying the optical Liouville
theorem across multiple scales in the imaging data, a technique we refer to as geometrical-duality. We test this method using realistic simulations and apply it to a 'constellation' consists of 11 compact
star clusters seen in two giant arcs in the
lensing cluster SMACS0723 imaged by JWST as a proof-of-concept. We find reasonable self-consistency with the expectation of non-detection given the statistical sensitivity, except for one pair of
star clusters. Such an outlier can be explained in the context of CDM as sub-
haloes lensing in the mass range $M_{\rm sub} = 10^8 - 10^9\,M_\odot$, for which the corresponding Einstein radius is smaller than the diffraction limit of JWST.
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All authors Leo W.H. Fung, Tom Broadhurst, Sung Kei Li, Jeremy Lim, Giorgio Manzoni, George F. Smoot