Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
Earth-Projected Clustering of Historical Optical Transients in the Palomar Observatory Sky Survey-I (POSS-I)
Stephen Bruehl, Beatriz Villarroel, Hichem Guergouri et al. (+2 more)
Palomar Observatory Sky Survey-I (POSS-I) images obtained before the launch of Sputnik contain
star-like point sources consistent with sub-second flashes that are absent from all subsequent observations. The nature and origin of these transients remain poorly understood. Based on models suggesting they are in geosynchronous orbit, we estimated the latitude/longitude over which POSS-I transients appeared. From a
dataset of 107,875 POSS-I transients, we selected a subset with high probability of representing real objects based on a machine learning model. Two independent approaches were used to test whether transients non-randomly grouped over specific locations (hotspots). Based on comparing transient numbers in discrete 5{\deg} x 5{\deg} Earth-projected regions to numbers randomly expected in these same regions, 16 statistically-significant hotspots were identified. Separately, two-step cluster analysis identified 6 highly-distinct hotspots (silhouette value = 0.70). The two methods identified several similar hotspots not attributable to POSS-I survey biases: 1) Pacific ocean west of southern Mexico/Central America, 2) southern Gulf of Mexico, 3) southwestern US (Sedona, AZ, White Sands, NM regions). Transients accounting for reported transient-nuclear testing associations displayed location specificity, with exclusively Pacific transient locations during Pacific nuclear testing and primarily southwestern US locations during Nevada testing. Findings hint at intriguing POSS-I transient characteristics.
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All authors Stephen Bruehl, Beatriz Villarroel, Hichem Guergouri, Brian Doherty, Alina Streblyanska
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA
JWST Spectra Conclusively Show an Excess of Neutral Gas Outflows in Quiescent Galaxies at z=2-5
Rion Oh, Gourav Khullar, Arianna S. Long et al. (+15 more)
Galaxies exhibit a broad range of
star formation activity, from actively
star-forming to quiescent systems. Yet, the mechanisms responsible for the rapid shutdown and continued suppression of
star formation remain poorly understood, particularly for the quiescent
galaxies recently uncovered by JWST at $z>3$. Neutral gas outflows provide a direct tracer of gas removal and regulation in quiescent
galaxies. We therefore present a NaID $\lambda\lambda5891,5897$ absorption–line stacking analysis of 274
galaxies at $z=2$–5 drawn from the DAWN JWST Archive (DJA) and the EMBER JWST program, using JWST/NIRSpec medium-resolution grating spectroscopy and NIRCam photometry. NaID absorption is detected in all quiescent
galaxy stacks spanning $z=2$–5, providing the first statistical evidence that neutral gas outflows are a ubiquitous feature of quiescent
galaxies in the early Universe. Compared to the non-quiescent
galaxy stacks, the quiescent stacks show mass loading factors higher by 2–4 dex, with mass outflow rates $\dot{M}_{\rm out} \sim 9$–$30\,M_\odot\,{\rm yr}^{-1}$ elevated by $\sim0.5$–$1$ dex and outflow velocities $v_{\rm out} \sim 310$–$570\,{\rm km\,s}^{-1}$ higher by a factor of $\sim2$. The extreme mass loading factor values and declining
star formation histories strongly indicate that these outflows cannot be driven by current
star formation alone. In the statistically reliable quiescent
redshift bins at $2 \leq z < 3$ and $3 \leq z < 4$, the elevated $[\mathrm{N\,II}]/\mathrm{H}\alpha$ and $[\mathrm{O\,III}]/\mathrm{H}\beta$ ratios are consistent with a possible AGN contribution, suggesting that non-stellar feedback may play a role in sustaining quiescence in
galaxies at these epochs.
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All authors Rion Oh, Gourav Khullar, Arianna S. Long, Julissa Sarmiento, Hollis B. Akins, Caitlin M. Casey, Yingjie Cheng, Andreas L. Faisst, Maximilien Franco, Ghassem Gozaliasl, Micheaela Hirschmann, Erini Lambrides, Jacqueline E. McCleary, Tiara Anderson, David C. Andrews, Dylan Berry, Nguyen Binh, Elaine Gammon
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA
TDCOSMO XXX: Spatially resolved kinematics of the deflectors in time-delay lens systems B1608+656 and SDSSJ1206+4332 from JWST-NIRSpec observation
Pritom Mozumdar, Shawn Knabel, Anowar J. Shajib et al. (+3 more)
We present spatially resolved stellar kinematics of the deflector
galaxies in two time-delay lens systems, B1608+656 and SDSS J1206+4332, measured from JWST NIRSpec integral field spectroscopy. B1608+656 is a quadruply imaged
quasar lensed by a pair of tidally interacting
galaxies, the primary deflector (G1) and a close companion (G2), for which we quantified G2's tidal influence on G1 and define a criterion identifying the region where this perturbation is negligible and standard Jeans-equation modeling remains valid. SDSS J1206+4332 is a doubly imaged
quasar whose extended host
galaxy is itself quadruply imaged by a foreground massive
galaxy (G0), accompanied by a fainter perturber (G1). For both systems, we report the first spectroscopic
redshift and velocity dispersion measurements of the perturber
galaxies. For G2 in B1608+656, we measure {\sigma}_v = 188 +/- 7 (stat.) +/- 2 (sys.) km/s at z = 0.6307, identical to the
redshift of the main deflector G1. For G1 in SDSS J1206+4332, we find {\sigma}_v = 100 +/- 21 (stat.) +/- 2 (sys.) km/s at z = 0.7403, slightly lower than the primary deflector G0. The resolved velocity maps of both primary deflectors show clear rotation signatures and we visually classify them as fast or regular rotators. The data products will be made publicly available and will be combined with time delays, lens models, and line-of-sight convergence to measure cosmological parameters in the upcoming TDCOSMO 2026 milestone publication.
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All authors Pritom Mozumdar, Shawn Knabel, Anowar J. Shajib, Tommaso Treu, Michele Cappellari, Aymeric Galan
Instrumentation and Methods for Astrophysics
The future of high-resolution UV spectroscopy: Science with a UV Échelle spectrograph on the Habitable Worlds Observatory, or a dedicated mission
Annalisa De Cia, David Cont, Kevin Heng et al. (+39 more)
High-resolution UV spectroscopy serves a diversity of science cases, from small bodies to
planets,
stars, and
galaxies, but is currently limited to the Hubble Space
Telescope and bright targets. Major advances require increasing sensitivity by at least one order of magnitude. Here we present the UV science cases for PEGASUS (
Planets, Earths,
Galaxies, And
Stars UV Spectrograph), a UV Échelle high-resolution spectrograph concept, with $R = \lambda/\delta\lambda \sim 100\,000$ (full range 10 000-140 000) and covering 90–400 nm, with a foreseen extension to at least 800 nm. PEGASUS is ideally suited for the Habitable Worlds Observatory (HWO), enabling transformative science across the UV/optical wavelength ranges. PEGASUS will be unique in high sensitivity (effective area) and high spectral resolution – an uncharted territory – as well as robustness, thanks to the simplicity of its design. Its UV science cases include: I) Formation and
evolution of
planets and their habitability: properties of
exoplanets and atmospheres, protoplanetary disks, Solar System bodies; II) Stellar lives and deaths at their extremes: the first
stars and the origin of the elements, compact and massive
stars,
Supernovae; III) Gas and metals in the baryon cycle of
galaxies: the interstellar, circumgalactic, and intergalactic medium and their roles in
galaxy growth. These are essential for the Astro Decadal 2020 Survey, Voyage 2050, and HWO. While this paper focuses on high-impact science enabled by UV high-resolution spectroscopy, PEGASUS will extend into the optical regime and lower spectral resolution, making it a multi-purpose, widely used, workhorse spectrograph for HWO.
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All authors Annalisa De Cia, David Cont, Kevin Heng, Boris Gänsicke, Frank Grupp, Ralf Bender, Helena Lamprecht, Frances H. Cashman, Hsiao-Wen Chen, Valentina D'Odorico, Kevin France, Andrew Fox, Jens Hoeijmakers, Masahiro Ikoma, Wynn Jacobson-Galán, Sean D. Johnson, Mansi Kasliwal, Shingo Kameda, Varsha Kulkarni, Carlo F. Manara, Antonija Oklopčić, Cyrielle Opitom, Lidia Oskinova, Anna F. Pala, Ian U. Roederer, P. Christian Schneider, Peter Scicluna, Daniel E. Welty, Sascha Zeegers, Abel de Burgos Sierra, Miriam García, Avery Kim, Christina Konstantopoulou, Roberto Maiolino, Daniel Pauli, Tanita Ramburuth-Hurt, Philipp Richter, Andreas A.C. Sander, Tomer Shenar, Sergio Simón-Díaz, O. Grace Telford, Anna Velichko
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE
cuDART: a GPU-accelerated ray tracing code for generating synthetic observations of relativistic astrophysical sources
Henry Whitehead, Emma L. Elley and Christoper N. Everett
The generation of synthetic observations is required to compare simulations of astrophysical phenomena with real sources. We present a new open-source toolkit cuDART which allows meshed simulation data to be rapidly rendered into synthetic observations of optically thin emission, automatically accounting for a range of relativistic and
geometric effects such as Doppler boosting. Unlike previous visualisation schemes which generally consider a single snapshot in time, cuDART is capable of accounting for the finite time delay across astrophysical distances by rendering data from multiple simulation epochs simultaneously. We demonstrate how failing to account for a finite light time delay can result in synthetic observations with incorrect observed motion, morphologies and fluxes. The code does not require a static pattern frame for integration, relaxing standard assumptions required for analytical observational estimates. The rendering processes is accelerated through hardware (using GPUs) and software (using the 3D differential digital analyser
algorithm), allowing for rapid generation of observations from a large number of viewing orientations. In this paper we describe the physical motivation, document the code operation and test the output against theoretical relativistic and
geometric expectations. cuDART is publicly available via GitHub and documented using ReadTheDocs.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.CO
Differential Polarization Calibration: A Consistency Test for Cosmic Birefringence
Anto I. Lonappan, Brian Keating and Kam Arnold
The
cosmic microwave background birefringence angle $\beta$ is exactly degenerate with a common instrumental polarization-angle offset. The Minami–Komatsu(MK) likelihood separates these quantities using Galactic foreground polarization, so its inferred detector angles merit a diagnostic that does not reuse the foreground-$EB$ model. We develop a birefringence-blind differential
estimator from antisymmetric and symmetric cross-spectra and apply it for the first time as an explicit consistency test of a foreground-assisted birefringence analysis. For a map pair, the common rotation cancels identically and the
estimator measures $\Delta\alpha_{ij}=\alpha_i-\alpha_j$; combining all pairs in a gauge-fixed network reconstructs the observable detector-dependent calibration pattern. Applied to eight Planck NPIPE detector-set maps, the differential reconstruction agrees with the MK pattern, giving $\chi^2=8.18$ for seven degrees of freedom (PTE=0.32), with all shared-data residuals below $1.8\sigma$. Because both reconstructions use the same maps, this is an independent
estimator and modeling route rather than an independent-data confirmation. The agreement therefore strengthens confidence in the calibration foundation of the MK-inferred $\beta$ without providing an independent absolute measurement of it. A conditional common-mode reconstruction gives $\beta=0.37\pm0.12^\circ$. The differential test uses existing data and can serve as a validation layer for future $EB$-based birefringence analyses.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
NRHJSur3dq8: a spectral numerical-relativity surrogate family for non-eccentric aligned-spin binary-black-hole waveforms
Vaishak Prasad
We present NRHJSur3dq8, a family of numerical-relativity (NR) surrogates for non-eccentric aligned-
spin binary-black-hole waveforms inspired by an action-angle parameterization. The model provides both the dynamics: the
Hamiltonian values, azimuthal action $J_\phi(\Phi)$, the orbital clock $\tau(\Phi)$ as functions of its phasing, and the radiative pieces: the waveforms, their near-analytic derivatives, and modeling errors associated with each. The surrogated variables are conditioned into pieces that vary slowly on the radiation-reaction timescale, represented on shared $hp$-adaptive Chebyshev elements, and regressed across the intrinsic parameters with a Gaussian-process model. A time-parameterized merger-ringdown set of elements is attached where the adiabatic description breaks down. Leave-one-out validation of the central NRHJSur3dq8_AA flavor against NR reaches a $(2,2)$ unweighted mismatch of $1.3^{+32}_{-1.2}\times10^{-6}$ and an all-mode mismatch of $2.3^{+59}_{-2.2}\times10^{-6}$ over the full inspiral-merger-ringdown span. Sky-averaged and SNR-weighted over $32$ orientations per simulation, the released model's full-IMR in-sample mismatch against the NR simulations used for training is $8.9\times10^{-7}$ to $2.8\times10^{-5}$ across total masses $40$-$120\,M_\odot$. Waveforms are hybridized using post-Newtonian waveforms. Beyond accuracy, NRHJSur3dq8 provides two capabilities uncommon in NR surrogates: nearly analytic derivatives of the strain with respect to the physical parameters, and a calibrated Gaussian-process predictive uncertainty of the model. A full non-hybridized inspiral-merger-ringdown waveform evaluates in $12$ ms on a single CPU call. Batched evaluation amortizes this to $0.39$ ms per waveform at a batch of $4096$, measured at a starting frequency of $20$ Hz.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE
Hierarchical Inference of the Supermassive Black Hole Binary Merger Rates from Joint Searches using Pulsar Timing Arrays
Sharon Mary Tomson, Rutger van Haasteren and Boris Goncharov
Gravitational-wave searches do more than identify individual sources - they provide a way to infer the underlying astrophysical populations that produce them. Currently,
Pulsar Timing Arrays (PTAs) constrain the supermassive black-hole binary (SMBHB) merger-rate density through both the
stochastic gravitational-wave background (SGWB) and searches for individual SMBHB signals. The latter implies converting source upper limits into rate upper limits using detection efficiencies estimated empirically. We instead develop a hierarchical
Bayesian framework that places the SMBHB merger-rate density model directly inside the PTA likelihood. The unknown catalog of individual SMBHB merger signals is modeled as a Poisson point process on source-parameter space, so that the number of merger signals is inferred from the data rather than imposed by a detection threshold. We describe two computational routes: a catalog-marginal likelihood based on analyses with fixed numbers of candidate sources, and an explicit transdimensional sampling approach that jointly samples population hyperparameters, latent merger signals, and noise. We validate the method with a toy merger-only population model and then apply it to an astrophysical SMBHB merger-rate density model that jointly predicts the SGWB amplitude and the expected merger-catalog size. In simulations, an individual merger signal adds complementary information to the SGWB and can tighten constraints on the merger-rate population.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA
Closed-Form of the Local Galactic Potential and Stellar Distribution Function from Gaia DR3
Indranil Das, Adam Kamoski, Dora Demiri et al. (+3 more)
The local dark matter density determines the strength of the signal expected in direct-detection experiments, yet published estimates from stellar motions disagree by more than their errors, and the most recent machine-learning analysis of Gaia data finds a local density consistent with zero. According to Jeans'
theorem, a distribution function built from integrals of motion satisfies the collisionless Boltzmann equation (CBE) trivially for any choice of potential, so a search that simultaneously fits the distribution function and the potential to the CBE identifies neither. Our pipeline instead estimates the distribution function in isolation, linearizing the equation in terms of accelerations and allowing for direct measurement of the local force field, and then fits closed forms to that field via symbolic regression. Throughout, we find that the usable information lies not in the CBE residual but in the stellar number counts, the observable most distorted by survey selection. Along the vertical profile, our recovered potential agrees with the classical self-gravitating isothermal disc.
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All authors Indranil Das, Adam Kamoski, Dora Demiri, Brianna Isola, Hanieh Karimi, Dmitrii S. Zagorulia
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
TARTARUS: A High-Performance Python Code for Ray Tracing in Curved Spacetimes
David F. Bambague and Alexis Larrañaga
The recent observations of the supermassive black holes M87* and Sagittarius A* by the Event Horizon
Telescope collaboration (EHT) have shown the need for robust, efficient, and accessible numerical tools to model light propagation in strongly curved spacetimes. Comparing theoretical
accretion models with observational data relies heavily on ray-tracing
algorithms that calculate the trajectories of
photons traveling from a source
plasma to a distant observer. In this paper, we present TARTARUS (Tracer for Astrophysical Ray Trajectories Around Relativistic Ultra-compact Sources), a new, highly modular, and extensible Python-based framework for computing null geodesics around compact objects. By leveraging Just-In-Time (JIT) compilation via Numba, TARTARUS bridges the gap between Python's high-level accessibility and the execution speed of compiled
languages like C++ or FORTRAN. The code supports multiple native solvers (including adaptive embedded Runge-Kutta pairs, a Bulirsch-Stoer extrapolator, and a Verlet scheme), event-detection mechanics for handling structural intersections (e.g. event horizons and
accretion disks), and support for both analytical and numerically generated background metrics. We demonstrate the code's physical accuracy and computational efficiency through some tests, including the evaluation of the
Hamiltonian constraint conservation and ray-tracing of the shadow and the Novikov-Thorne thin
accretion disks around a Kerr black hole.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE
Enabling new sampling strategies for continuous-wave analyses by integrating Bilby into PyFstat
Maria-Antonia Ferrer-Martinez and David Keitel
Continuous-wave searches for rotating
neutron stars usually cover wide parameter spaces and produce a large number of candidate signals.
Stochastic sampling methods therefore play an important role in candidate follow-up and parameter estimation. We present the integration of the
Bayesian inference library BILBY into the open-source continuous-wave analysis package PyFstat, enabling access to the broad range of
stochastic samplers available through BILBY while preserving the existing PyFstat analysis infrastructure. The implementation is validated through injection studies in Gaussian noise for two representative single-stage follow-up configurations: candidates from a directed search and candidates from an all-sky search. Using the nested sampler DYNESTY, we obtain detection efficiencies consistent with the theoretical sensitivity predictions. In this setup, DYNESTY performs comparably to the existing PTEMCEE-based implementation of PyFstat for the directed case, and also provides an effective single-stage approach for the all-sky candidate follow-up considered here, where we did not identify a PTEMCEE setup with similar recovery performance. Percentile-percentile tests for DYNESTY further show well-calibrated credible intervals, demonstrating reliable parameter estimation. While a full exploration of DYNESTY settings, multi-stage setups, and other samplers is left for future work, these results demonstrate that this flexible and publicly available framework opens useful new possibilities for
Bayesian continuous-wave analyses.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE
Supermassive black hole binaries in the multi-messenger context of ground and spaceborne VLBI
B. Hudson, L. I. Gurvits, D. J. D'Orazio et al. (+3 more)
Evidence of a gravitational wave background suggests the existence of a population of sub-parsec supermassive black hole binaries (SMBHBs), with characteristic angular separations on the order of 1-10 $\mu$as. Spaceborne extensions of Very Long Baseline Interferometry (VLBI) and the next generation ground arrays introduce the possibility of directly imaging these SMBHBs. In this work, a binary spectral energy distribution model is used to predict the detectability of SMBHBs with ground and spaceborne VLBI. We consider the Black Hole Explorer (BHEX), a proposed spaceborne VLBI mission, as our primary case study. We explore the detectable SMBHB parameter space and identify distinguishable binary signatures in the visibility domain. We find that for a flux-density-limited sample, ground array observations are more effective at detecting a wider region of the binary parameter space, with $M_\mathrm{tot} \gtrsim 10^9$ solar mass systems detectable out to
redshift $z=0.075$ and beyond, depending on mass ratio. Conversely, inclusion of a spaceborne element such as BHEX, offering finer angular resolution ($\sim6\,\mu$as) and sampling of the (u,v) plane not limited by Earth rotation synthesis, will provide significant benefits in constraining binary properties. An illustrative Fisher analysis shows improvements in characterisation of the separation and position angle of SMBHBs by a factor of $\sim4$. Near-future ground and/or spaceborne VLBI may achieve the first direct observation of a SMBHB, contributing significantly to multi-messenger studies of such systems with
pulsar timing arrays and observations across the electromagnetic spectrum.
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All authors B. Hudson, L. I. Gurvits, D. J. D'Orazio, C. Tiede, T. M. Eubanks, E. Mooij
Instrumentation and Methods for Astrophysics
Full Characterisation of the Polarisation Primary Beam of the GRAO 32-m Telescope
Theophilus Ansah-Narh, Nia Imara, Benedicta Woode et al. (+4 more)
Direction-dependent instrumental polarisation is a major systematic limitation in high-fidelity single-dish
radio polarimetry, yet a unified characterisation of beam leakage and the conditioning of polarisation recovery is lacking for the Ghana
Radio Astronomy Observatory (GRAO) 32-m
telescope. We aim to establish a quantitative, direction-dependent polarimetric beam model at 5.0 and 6.7 GHz. High-resolution GRASP electromagnetic simulations of the nominal
telescope configuration are used to derive the full complex Jones response and corresponding Mueller
matrices, from which beam shape, beam squint, instrumental Stokes leakage, and intrinsic cross-polarisation ratio (IXR) are evaluated across the primary beam. The Stokes $I$ beams have half-power beam widths of $396.4$ and $295.3$ arcsec at 5.0 and 6.7 GHz, respectively, with main-beam efficiencies of $56.4$ and $55.6$ per cent. At 5.0 GHz, the circular-polarisation beam squint is $9.96$ arcsec ($2.5$ per cent of the HPBW), whereas no statistically significant squint is detected at 6.7 GHz. Leakage from Stokes $I$ into linear polarisation remains below $0.1$ per cent within the half-power beam but increases substantially towards the sidelobes. IXR reaches approximately $80$ dB on axis and decreases with angular offset. These results establish the intrinsic electromagnetic polarimetric response of the GRAO 32-m
telescope and provide a quantitative baseline for direction-dependent calibration and subsequent observational validation.
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All authors Theophilus Ansah-Narh, Nia Imara, Benedicta Woode, Joseph Bremang Tandoh, Emmanuel Proven Adzri, Diana Klutse, Evaristus Uzochukwu Iyida
Instrumentation and Methods for Astrophysics
A Content-Addressed Workflow for Reproducible DANTE Gravitational-Wave Anomaly Analysis
Luca Cirfeta
Unsupervised analysis of gravitational-wave detector data combines expensive scientific stages with data acquisition, provenance checks, statistical calibration, follow-up products, and reporting. Reproducing such an analysis requires more than preserving model weights or a final candidate table: the execution graph, scientific contracts, retry semantics, and verification boundary must also be explicit. We present a local workflow layer for the Domain-Adaptive Network for Transient Evaluation (DANTE) that represents a corrected O4a analysis as a content-addressed, 15-stage directed acyclic graph. The architecture separates immutable stage evidence from mutable operational progress, binds command-line and browser interfaces to the same run identity, and resumes only work compatible with the frozen contract. The tagged v1 release records all 15 stages as verified in a machine-readable receipt and passed a documented human usability gate. The release verifies adopted scientific artifacts rather than recomputing them, and therefore makes no new claim of global significance, astrophysical discovery, or public real-time operation. This paper describes the architecture, its fail-closed controls, and the bounded evidence supporting reproducible local use.
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Instrumentation and Methods for Astrophysics
A Missing Tool for Calculating Auto/Cross-correlation Function under Nonuniform Sampling Observations
Chen-Ran Hu, Yong-Feng Huang, Jin-Jun Geng et al. (+10 more)
Nonuniform sampling presents a long-standing challenge in astrophysical time-domain analysis, invalidating the standard autocorrelation and cross-correlation functions and forcing researchers to adopt ad-hoc methods like interpolation or binning, which introduce unquantified biases and lack rigorous error estimation. Here we introduce a new method for calculating the nonuniform autocorrelation function (NUACF) and nonuniform cross-correlation function (NUCCF) for irregularly sampled time series. Instead of relying on interpolation, it naturally evaluates the correlation function by incorporating time-interval weights and misalignment penalties. Monte Carlo simulations provide confidence bands for significance assessment and a complete error budget for the time delays that accounts for both flux uncertainties and sampling irregularity (essential but generally absent from existing methods). Through extensive simulations, we demonstrate our method outperforms traditional methods across various conditions, from strictly periodic to complex repeating variability patterns (e.g., intermittent but aperiodic). Its effectiveness is demonstrated via various real astrophysical data sets, revealing repetitive variability in stellar light curves, measuring time delays for multi-band disc reverberation in the AGN Fairall 9, and providing model-independent validation of time delays for the gravitationally lensed
quasar HE 0435-1223. The method provides a rigorous and general solution to the ubiquitous problem of nonuniform sampling, positioning it as a useful tool for large-scale time-domain survey data analysis. The framework is also directly applicable to emerging time-domain phenomena such as fast
radio bursts (FRBs), enabling, e.g., the study of correlations between persistent
radio source luminosity and repeating FRB activity, or among the multi-parameter variability curves of FRB emission itself.
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All authors Chen-Ran Hu, Yong-Feng Huang, Jin-Jun Geng, Orkash Amat, Ze-Cheng Zou, Chen Deng, Fan Xu, Xiao-Fei Dong, Chen Du, Nurimangul Nurmamat, Pei Wang, Lang Cui, Cheng-Ming Li
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
MAD-LEO: A Maneuver-Annotated Orbital Dataset for LEO Satellites with Tiered Multi-Source Evidence
Zhixin Guo, Qi Shi, Xiaofan Xu et al. (+6 more)
With the rapid development of aerospace technology and the large-scale deployment of low Earth orbit (LEO) constellations, the risk of orbital collisions has increased, creating a growing demand for reliable observations of satellite maneuvers. However, public
datasets containing real maneuver records remain scarce. We present MAD-LEO, a Maneuver-Annotated orbital
Dataset for LEO satellites. The mission-reported subset contains 1,134 maneuver events from eleven geodetic and altimetry satellites spanning 1992 to 2026, with labels taken directly from mission-published maneuver histories. Each event is checked against two-line element (TLE) data, precise orbit products, and satellite
laser ranging (SLR) observations, with evidence tiers assigned according to data availability. The operational subset pairs operator-published ephemerides for 6,785 Starlink satellites with cataloged TLE records over a continuous 107-hour period. Technical validation across seven machine-readable experiment suites confirms the cross-source consistency of the labels and the evidence products.
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All authors Zhixin Guo, Qi Shi, Xiaofan Xu, Linqiang Ge, Hua Zhu, Liyan Ben, Bendian Nie, Yuanrui Zhao, Xiaohan Li
Instrumentation and Methods for Astrophysics
CTree: Branch-wise compatible merger tree builder
Jinsu Rhee, Christophe Pichon and Yohan Dubois
We introduce a merger tree builder, CTree. Its key feature is the identification of progenitors using the evolutionary information encoded in object branches, rather than relying solely on the instantaneous particle membership in a single snapshot. In this sense, CTree can be described as a branch-wise merger tree builder. Specifically, CTree extracts particles associated with objects over a defined timescale and uses this information to compute the merit functions employed in the progenitor search across multiple snapshots. During this process, CTree requires only the identifiers of particles and objects. This ensures high compatibility with different
halo and
galaxy catalogues and also with pre-existing merger trees. To identify `core' particles that remain bound to the host
halo over extended physical timescales, CTree employs a simple and efficient
algorithm that does not rely on explicit radial or binding-energy information. The timescale adopted for core particle extraction and the number of snapshots used in the progenitor search can be user-configured. Basic validation tests using suites of dark matter-only simulations demonstrate that CTree produces stable and physically consistent
halo merger trees, particularly in high-density regions or in simulations with high output cadence. The code is written in C++ and employs a hybrid message passing interface and OpenMP parallelization, making it well-suited for high-resolution cosmological simulations. The code is publicly available and actively maintained to improve performance, reliability, and compatibility.
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