Instrumentation and Methods for Astrophysics
Diffusion Models for Polarimetric Reconstruction of Circumstellar Environments in Correlated Speckle Noise
Quentin Villegas, Laurence Denneulin, Simon Prunet et al. (+3 more)
High-contrast polarimetric imaging of circumstellar disks is severely limited by stellar leakage and speckle noise. Building upon the RHAPSODIE framework for polarimetric inverse problems,
diffusion-based methods have shown promising results by replacing classical regularization with learned priors. However, RHAPSODIE's white noise assumption fails to capture the spatial correlation structure of atmospheric and instrumental speckles. We extend this framework to handle speckle fluctuations, which are modeled as a Gaussian field with a stationary covariance
matrix with a Gaussian spectral density. To efficiently apply the dense precision
matrix that includes correlated speckle and heteroskedastic
photon noise, we develop a dedicated preconditioner for conjugate gradient iterations. The
diffusion prior is trained exclusively on disk-only data. While limitations remain at very low SNRs, our method significantly outperforms Tikhonov regularization and competes favorably with a Plug-and-Play baseline in realistic regimes, successfully recovering morphological features masked by correlated noise.
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All authors Quentin Villegas, Laurence Denneulin, Simon Prunet, André Ferrari, Éric Thiébaut, Maud Langlois
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR
Properties of Circumfacular Regions derived from H$\alpha$ and Ca II K synoptic observations of the Sun
Serena Criscuoli and Andrea Diercke
Circumfacular regions are dark chromospheric structures surrounding
magnetic regions whose properties and contribution to solar activity diagnostics remain poorly understood. We investigate their photometric and
geometric properties using full-disk H$\alpha$ and Ca II K observations acquired by the Chromospheric
Telescope (ChroTel) from 2012 to 2020, spanning the maximum and declining phases of solar cycle 24 and the beginning of cycle 25. We develop an automated segmentation
algorithm to identify circumfacular regions and define a photometric index analogous to existing excess and deficit indices. We compare their temporal
evolution with those of plages, dark features, and filaments on solar-cycle and Carrington-rotation timescales. Circumfacular regions develop after the H$\alpha$ plage brightening become visible and persist into the decay phase of active regions. At activity maximum, they are the most extended chromospheric structures, covering more than half of the visible solar disk. Their mean intensity varies only weakly throughout the solar cycle; consequently, their index variability, as well as that of the other photometric indices, is driven primarily by changes in area coverage. H$\alpha$ and Ca II~K indices are strongly correlated, although their correlations weaken toward solar minimum. This activity-dependent relationship is primarily driven by the decline of the area of H$\alpha$ excess regions during periods of low activity, and the increasing relative contributions of deficit and circumfacular regions. Our results therefore suggest that circumfacular regions should be considered when interpreting disk-integrated chromospheric observations of the Sun and solar-type
stars.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE
Assessing the detectability and identification of pulsar halos with H.E.S.S. and CTAO
Karim Sabri, Yves Gallant and Justine Devin
Pulsar halos are a class of extended gamma-ray sources, resulting from inverse Compton scattering of ambient
photons by electrons and positrons believed to have escaped confinement in a
pulsar wind nebula. First identified by HAWC towards PSR J0633+1746 and PSR B0656+14, a growing number of
pulsar-powered gamma-ray sources is proposed as candidate
halos. Using a model of isotropic
diffusion, we assessed the ability of current-and-future generation imaging atmospheric Cherenkov
telescopes to characterize the physical properties of such sources in the inner
Galaxy. We constructed template-based
pulsar halo models in the Gammapy library and fitted them to simulated H.E.S.S. and CTAO data of
halos with different physical parameters. The sources were characterized spectro-morphologically using 2D Gaussian components. We assessed the statistical preference between the
halo and 2D Gaussian hypotheses by the simulated data and quantified the impact of the diffuse Galactic emission. A multitude of the
halos' parameters can be constrained simultaneously, including the
pulsar's true age, its proper motion, the
diffusion coefficient, the index of the injected particle spectrum and the injection efficiency. In some cases, the H.E.S.S. array can statistically distinguish between the
halo model and a model containing 2D Gaussian components, while a significant improvement is seen with CTAO. The source's detection significance is drastically reduced with increasing intensity of the Galactic diffuse emission. If the latter is not modeled using the data-generating model, the
halo parameter estimation is biased. A physically-motivated model of
pulsar halos can facilitate the identification and characterization of this class of sources in high-level data analyses. The simulated
halos exhibit properties that may already be found in surveys of current-generation
telescopes with only a modest observation time.
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Instrumentation and Methods for Astrophysics
Comparing Active Anomaly Detection Frameworks: From Light Curves to Images
Sreevarsha Sreejith and Robert C. Nichol
The increasing volume and complexity of data from modern astronomical surveys are making comprehensive visual inspection increasingly impractical, motivating automated methods for identifying rare and unusual objects. Active anomaly detection (A-AD) combines unsupervised anomaly detection with iterative user feedback, allowing searches to adapt to scientific interests while retaining sensitivity to unexpected objects. We systematically compare three A-AD frameworks, Astronomaly, Protege, and PineForest, across Zwicky Transient Facility light curves and Euclid
galaxy images. In baseline experiments, Protege, PineForest, and Astronomaly recovered 83, 78, and 38 variable
stars, respectively, within the first 100 light-curve objects inspected, while PineForest recovered 70 merging or morphologically disturbed
galaxies within the first 100 Euclid images, compared with 29 and 19 for Astronomaly and Protege. Experiments using prior labels show that their effectiveness depends on the composition of the prior sample and varies between A-AD methods. Finally, we combine the complementary behaviour of Protege and PineForest in a hybrid search of 10,000 Euclid images, recovering 799 morphologically unusual objects. These include 29 retained strong lens systems and candidates, of which 9 candidates have no counterparts in the published Euclid Q1 strong lens catalogues searched, and 202 visually classified ring
galaxies. These results highlight the importance of selecting A-AD strategies according to both the scientific objective and
dataset properties, and demonstrate their potential for efficient, discovery-driven exploration of forthcoming astronomical surveys.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE
First Detection of the Doppler Shift of X-ray Photons Due to a Telescope's Orbital Motion
Stephen DiKerby and Shuo Zhang
We have detected for the first time the redshifting and blueshifting of X-ray
photons due to the orbital motion of an X-ray
telescope around the Earth. Current and planned X-ray
telescopes like XRISM/Resolve and NewAthena can achieve energy resolutions $R = E / \Delta E \approx 1000$, requiring spectroscopic calibration of physical effects such as the local standard of rest and the orbit of the Earth around the Sun. We construct an a priori method for detecting a heretofore unexamined effect: the modulation of
redshift due to the motion of an X-ray
telescope around the Earth. We apply this pipeline to several XRISM/Resolve observations of narrow iron K$\alpha$ emission lines from galactic center molecular clouds, and we detect evidence of orbital
redshift modulation in the K$\alpha$ emission at the 95% confidence level. Our findings suggest that orbital
redshift modulation is already present and detectable in X-ray data and motivates reexamination of how X-ray
photon data is packaged in the emerging era of high-resolution X-ray spectroscopy.
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Instrumentation and Methods for Astrophysics
Divergence-free magnetohydrodynamics on a moving mesh
Volker Springel, Alexander C. Mayer and Rüdiger Pakmor
Magnetic fields are ubiquitous in the Universe and play an important role in many astrophysical processes, such as
star formation and the
evolution of
galaxies. Hydrodynamical simulation methods that account for ideal magnetohydrodynamics (MHD) are however challenged by the need to achieve numerical stability and physical consistency. Both can be compromised by the occurrence of non-vanishing local divergence errors in the
magnetic field. Different approaches to either eliminate or reduce these discretization errors are in widespread use, including constrained transport or divergence cleaning techniques. However, thus far a divergence-free Galilean invariant formulation of MHD that can be readily applied in Lagrangian codes has been an elusive goal. Here we revisit the use of the vector potential for evolving the
magnetic field on an unstructured moving-mesh and show how a particular gauge choice combined with a suitably discretized integration scheme provides a stable and accurate formulation of MHD. Our method combines a finite-difference
evolution of a
cell-centred vector potential with a finite volume representation of the other fluid quantities, and is realized in the moving-mesh code AREPO. The new approach is fully Galilean invariant and therefore shows vanishing errors for classic problems such as field loop advection. We demonstrate good accuracy and stability when our scheme is applied to various test problems and to practical applications in 3D, including when local timesteps and adaptive mesh refinement and derefinement are used.
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Instrumentation and Methods for Astrophysics
Improved Modeling for Moving Sources of Radio Frequency Interference and Impact on Flagging Strategies
Jade M. Ducharme, Jonathan C. Pober and Michael J. Wilensky
Radio frequency interference (RFI) is a major challenge for low-frequency
radio experiments targeting the redshifted 21-cm signal from the Epoch of Reionization. Many important RFI sources, including aircraft and satellites, move across the sky during an observation. The averaging of visibilities for such moving sources over a finite correlator integration produces a distinct sinc-like pattern in the interferometric uv-plane, causing the RFI to appear bright on some baselines and strongly suppressed on others. Here, we develop an analytical model for this effect and validate its qualitative behavior against real MWA observations and numerical simulations. Controlled RFI injections into clean MWA data are then used to compare several flagging treatments in the context of EoR power spectrum recovery. These treatments explore the trade-off between per-baseline flagging, which can miss weak but potentially non-negligible contamination on baselines where the integration effect leads to strong suppression, and baseline-aggregated flagging, which removes more faint residual contamination but reduces the total number of usable uv-modes. We find that the preferred strategy depends on RFI brightness and occupancy, but that flagging all frequencies at contaminated time-steps most consistently minimizes excess power for bright or frequent events. However, none of the tested flagging treatments fully recovers the uncontaminated reference spectrum, motivating future work on direct modeling and subtraction of moving RFI sources.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
GameDev: GPU-accelerated model for dust evolution
Jiaqing Bi
Grain growth and fragmentation through dust collisions in protoplanetary disks are strongly coupled with dust dynamics. This is because the spatial and velocity distributions of dust set the collision rates and outcomes, while dust grain sizes set the aerodynamic coupling with gas. However, existing dust
evolution codes often rely on prescribed dust velocities and are mostly restricted to one or two spatial dimensions. In this work, we present GameDev, a dust
evolution model accelerated by graphics processing units (GPUs) that couples independently evolved three-dimensional dust dynamics with Monte Carlo collisional
evolution of dust. In GameDev, we model dust as Lagrangian representative particles in a prescribed gas disk. We integrate particle trajectories with the staggered semi-analytic method, which remains accurate for both tightly and weakly coupled dust grains. We estimate collision rates from each particle's nearest neighbors rather than on a grid, preventing physically close particles from being excluded from collision sampling because they lie across a grid boundary. Most importantly, we sample collision events against neighborhoods that remain frozen over adaptive intervals, enabling massive parallelization across particles. These implementations make GameDev an accurate and efficient tool for studying dust
evolution in protoplanetary disks. GameDev supports both NVIDIA CUDA and AMD ROCm platforms, provides a smaller-scale standalone Eulerian dust fluid model, and is publicly available on GitHub.
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Instrumentation and Methods for Astrophysics
SIFARI: Self-Supervised Interferometric Fitting for Astronomical Radio Imaging
Shunyuan Mao, Andrea Isella, Paris Perdikaris et al. (+2 more)
Radio-interferometric images are reconstructed from sparsely sampled visibilities, and CLEAN-based imaging can struggle with spatial filtering, complex morphologies, and uncertainty quantification. Alternative methods that fit visibilities directly can address some of these limitations but often require manual choices of image priors and model hyperparameters. We present SIFARI (Self-Supervised Interferometric Fitting for Astronomical
Radio Imaging), a self-supervised neural network workflow that represents sky brightness as a continuous function of position and fits measured visibilities without an external image training set or explicit spatial regularizer. An empirical rule sets the
Fourier feature scale from the visibilities before training, controlling how readily the network fits fine structure. Sampling network weights with
Stochastic Weight Averaging-Gaussian (SWAG) gives approximate brightness uncertainty estimates, which we combine with a thermal-noise floor to construct spatially resolved signal-to-noise maps. In synthetic ALMA tests, SIFARI yields an effective point-source response about eight times narrower than the natural-weighting CLEAN restoring beam and recovers more extended flux than CLEAN when short baselines are missing. It also achieves higher image fidelity than the restored CLEAN images in all three morphology
benchmarks. Applied to ALMA observations of PDS 70, SIFARI recovers the bright outer ring together with faint compact emission in the central cavity. For long-baseline-only WISPIT 2 data, SIFARI supplies a sky model for phase self-calibration where the CLEAN model is inadequate. The restored, self-calibrated SIFARI image has approximately 30% lower RMS noise than the CLEAN image made from the original visibilities without self-calibration.
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All authors Shunyuan Mao, Andrea Isella, Paris Perdikaris, Li-Ta Lo, Hui Li
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Low Frequency Gravitational Wave Detection with Gravito-Magnetism
Reza Ebadi and Surjeet Rajendran
The detection of gravitational waves in the low-frequency band (10 nHz to 1 micro-Hz) using inner solar system proof masses is severely limited by Newtonian
gravity gradient noise (GGN) sourced by the asteroid belt. In this paper, we propose a novel detection concept that exploits the relativistic nature of gravitational waves to break the degeneracy between the signal and the asteroid GGN background. The non-relativistic motion of asteroids dominantly sources gravito-electric fields, with velocity suppressed gravito-
magnetic components. Relativistic gravitational waves produce gravito-electric and gravito-
magnetic components of equal magnitude. We propose detecting the gravito-
magnetic component of low frequency gravitational waves using the Lorentz acceleration of test bodies. The measurement of this Lorentz acceleration is metrologically possible due to the fact that expected astrophysical sources of low frequency gravitational waves have considerably higher characteristic strains than the strains typically expected at higher frequencies. We show that this measurement allows for unambiguous extraction of the gravitational wave signal from the
gravity gradient noise in a three satellite constellation. The gravito-
magnetic measurement still requires a proof mass that is well isolated from non-gravitational noise. We propose the use of atom interferometers to serve as such a pristine inertial reference.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR
Discovery of over a thousand variable stars in Terzan 5 and Liller 1 with JWST
Kevin B. Burdge, Ilaria Caiazzo, Malina M. Desai et al. (+18 more)
The Bulge Fossil Fragments Terzan 5 and Liller 1 host some of the densest stellar environments in the
Galaxy, yet their variable
star populations have remained largely unexplored due to crowding and heavy obscuration. Here, we identify 1,315 variable sources in these two systems in what is to our knowledge the first JWST time-series variability census of a globular cluster-like object. By differencing consecutive non-destructive reads within each NIRCam integration, we transform sample-up-the-ramp imaging into an infrared movie sampled every 21 seconds. More than a century of observations has cataloged 5,604 variables, the majority of them pulsating
stars, across 151 Galactic globular clusters. Our census alone amounts to 23 percent of that total and contains more photometrically variable binaries than had previously been cataloged in all globular clusters combined. The field of Liller 1, with zero previously known variables, now hosts 915, nearly double the count in the runner-up $\omega$ Centauri. We detect dramatic infrared variability from the Rapid Burster, revealing the counterpart sought since 1976 (see Desai et al. 2026), and blindly recover a signal coincident with the prototype redback
pulsar PSR J1748-2446A at its
radio-timed orbital period, identifying the first optical or infrared counterpart to any of Terzan 5's
pulsars. More broadly, we present a technique that recovers group-level time-series photometry from JWST observations, enabling time-domain studies with an observatory whose field of view is naturally matched to the
Galaxy's densest stellar systems.
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All authors Kevin B. Burdge, Ilaria Caiazzo, Malina M. Desai, Cristina Pallanca, Vera L. Berger, Kaley Brauer, Matteo Correnti, Paul Draghis, Kareem El-Badry, Francesco R. Ferraro, Denis González-Caniulef, Kyle Kremer, Barbara Lanzoni, Dongzi Li, Jessica R. Lu, Geoffrey Mo, Mason Ng, Roger W. Romani, Kaitlyn Shin, Daniel R. Weisz, Giorgia Zullo
Instrumentation and Methods for Astrophysics
Reconstructing Implicit Scientific Knowledge: Evaluating LLM Agents through End-to-End Reproduction of Astronomy
Yuehui Wang, Xinyu Qi, Guirong Xue et al. (+4 more)
The integration of large
language models (LLMs) into scientific workflows is accelerating, yet their ability to reconstruct the
reasoning underlying published research remains unexplored. Papers specify explicit procedures while leaving many methodological dependencies-data selection, calibration corrections, priors, and domain assumptions-implicit. This ambiguity complicates the evaluation of LLM-based
agents, since a failure to reproduce a result may reflect either limitations of the
agent or underspecification in the source. We present a framework that evaluates
agents through end-to-end reproduction, separating execution from verification and computational failure from methodological ambiguity. We apply it to fourteen astronomy studies: a case study from The Astrophysical Journal and thirteen papers published in Nature. Eleven of the thirteen contained an ambiguity preventing a uniquely specified reproduction path. In a controlled case study, twelve predefined paths, a 3x2x2 sensitivity analysis over sample definition, sky masking, and parallax zero-point treatment-gave estimates from 2.16 to 3.53 kpc for the same quantity, with only one recovering the published value (about 2.70 kpc). The published value was never used as an optimization target, selection criterion, or stopping condition; the matching path was found only after all twelve had run. Crucially, the decisive information (a +0.02 mas parallax zero-point correction) was already in the paper, but the
agents did not recognize its causal relevance until the analysis made the effect visible. Matching a published outcome therefore does not validate reconstruction of the underlying
reasoning, and the bottleneck is as often a failure to connect relevant information as to retrieve it. End-to-end reproduction thus serves both as a test of reproducibility and as a framework for evaluating implicit scientific knowledge in AI systems.
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All authors Yuehui Wang, Xinyu Qi, Guirong Xue, Cheng Wang, Yangbin Xie, Xiaoyu Tang, Cong Sun
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
Correcting stellar contamination in transmission spectroscopy with contemporaneous monitoring: Application to GJ 1214 b
Ò. Porqueras-León, M. Perger, J. C. Morales et al. (+19 more)
Transmission spectroscopy has emerged as an essential tool for characterising the atmospheres of transiting
exoplanets. However, stellar surface inhomogeneities contaminate transmission spectra, posing a major challenge to high-precision observations such as those from the James Webb Space
Telescope (JWST). We develop and apply methods to correct for stellar contamination, improving the accuracy of
exoplanet atmospheric characterisation. We obtained coordinated multi-band photometry and high-resolution spectroscopy around JWST observations of GJ 1214 b and applied two frameworks: (i) a StarSim inversion, which infers stellar activity parameters from the monitoring data and propagates them to corrections; and (ii) UnSPOTTER, in which neural networks trained on StarSim simulations learn the mapping from monitoring data to corrections. Both frameworks agree within uncertainties and indicate that the JWST observations of GJ 1214 occurred at a favourable rotation phase with low stellar contamination. For UnSPOTTER, the inferred corrections can be constrained at approximately 15 ppm across the JWST wavelength range, implying post-correction residuals of the same order. If the same system were observed near activity maximum, the predicted contamination would be strongly chromatic and affect atmospheric
retrievals, highlighting the importance of coordinated monitoring and robust activity correction techniques. The two approaches are complementary but serve different roles. The inversion yields physically interpretable parameters and surface maps, whereas UnSPOTTER marginalises over surface-configuration degeneracies and provides tighter predictive corrections within its validated simulation domain. Our pipeline can be generalised to other active
stars: with multi-band and multi-technique monitoring around JWST visits, it can provide activity forecasts for scheduling and activity corrections.
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All authors Ò. Porqueras-León, M. Perger, J. C. Morales, I. Ribas, J. Blanco-Pozo, H. Tabernero, E. Herrero, E. Pallé, H. Parviainen, F. Murgas, C. Rodríguez-López, P. H. Hauschildt, A. Schweitzer, N.-E. Nèmec, D. Baroch, N. R. C. Gomes, G. Anglada-Escudé, J. Aceituno, N. Narita, A. Fukui, M. Mori, Y. Smolyarova
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
K-dwarf starspot hunters: how to directly characterize spot and faculae properties with UV-IR panchromatic transit spectra
Joanna K. Barstow, Caitlyn Cullen, Yvonne Unruh et al. (+7 more)
Transmission spectroscopy of
exoplanets provides an important window into their atmospheric composition, structure and dynamics, especially in the JWST era. As the quality of the observational data and therefore the precision of our constraints improves, we become increasingly sensitive to sources of systematic bias in our models and observations. One significant example of this is the Transit Light Source Effect, in which heterogeneous features in the stellar photosphere - spots and faculae - imprint additional spectral signatures onto
exoplanet transmission spectra. The effects of this stellar contamination must be accounted for or removed in order to accurately recover the
planet's atmospheric properties. Including parameterized models of spots and faculae within spectral
retrieval analysis is increasingly adopted as a solution to this problem, but is limited by the accuracy of models of stellar spectra. In this paper, we outline an observational strategy combining simultaneous data from JWST and the Hubble Space
Telescope that would enable us to further constrain these models. We perform synthetic
retrievals to demonstrate how we could constrain starspot and faculae parameters; we test the impact of using different model spectra in the
retrieval; and we consider the impact of variable stellar activity on coadding transits to achieve the desired signal-to-noise. We find that ultraviolet and optical wavelengths are key for breaking degeneracies between stellar contamination and planetary parameters.
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All authors Joanna K. Barstow, Caitlyn Cullen, Yvonne Unruh, Hannah Wakeford, Eva-Maria Ahrer, Lili Alderson, Charlotte Fairman, Ulrich Kolb, Nikole Lewis, Cinta Vidante
Instrumentation and Methods for Astrophysics
Accelerating massive ensembles of ordinary differential equations
Lawrence Berry, Will Handley, Oliver Hahn et al. (+1 more)
Solving large ensembles of small, independent ordinary differential equations (ODEs) is a common task in computational science and engineering, arising for example in
Bayesian parameter estimation, Monte Carlo uncertainty quantification, and the integration of uncoupled physical systems such as the linearised Einstein-Boltzmann equations of cosmology. Modern graphics processing units (GPUs) with thousands of cores are well suited to such parallel workloads, but realising this potential requires careful
attention to GPU-specific architectural constraints. We present modax, a Python library of GPU-accelerated ODE solvers specifically optimised for solving large ensembles of low-dimensional, independent problems. Our solvers are compatible with the JAX ecosystem but are written in a low-level, thread-based programming paradigm better suited to ensembles of highly divergent trajectories than their pure-JAX counterparts.
Benchmarks on the Lorenz, Robertson and van der Pol
lattice systems compare modax against diffrax, DiffEqGPU$.$jl and torchdiffeq across ensemble size, dimensionality, and trajectory divergence. Our explicit Tsit5 solver achieves 30x speed-up over diffrax on Lorenz systems, and our implicit Rodas5P solver achieves over 700x speed-up on Robertson systems, demonstrating the superiority of linearly implicit Rosenbrock-Wanner methods on GPUs. Our implicit solver scales well to higher dimensions thanks to the use of sparsity-exploiting techniques and data structures. We conclude by applying modax to three examples from the field of cosmology -
Bayesian parameter estimation from primordial abundances, Monte Carlo uncertainty quantification of the global 21cm signal, and the computation of uncoupled
Fourier modes in the primordial power spectrum - and demonstrate significant efficiency improvements in our ability to model physical phenomena described by low-dimensional (<200D) ODEs.
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All authors Lawrence Berry, Will Handley, Oliver Hahn, Nils Schöneberg
Instrumentation and Methods for Astrophysics
Refactoring the SIXTE simulator: Towards a more modular code base
Christian Kirsch, Maximilian Lorenz, Lea Dauner et al. (+7 more)
The SIXTE (SImulation of X-ray
TElescopes) software is a general end-to-end simulation toolkit for X-ray observations, covering the full observation process from source
photon generation to detector readout and the production of high-level output files. It is the official simulator for existing and future X-ray missions, such as eROSITA, NewAthena, THESEUS and AXIS. Originally being designed as a simulator for eROSITA, the addition of new instrument and
telescope types over several years has made the original code base increasingly difficult to maintain. As such, we have refactored the code, changing
languages from C to C++ and switching to a more modular software design to facilitate the implementation of new models. This proceeding highlights some of the design choices used during the refactoring as well as its effects on maintenance and new feature development one year after release of the refactored code base.
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All authors Christian Kirsch, Maximilian Lorenz, Lea Dauner, Esin G. Gülbahar, Karan Pal, Neo Reinmann, Jakob Stierhof, Philipp Thalhammer, Thomas Dauser, Jörn Wilms
Instrumentation and Methods for Astrophysics
Source–Line Associations in JWST/NIRSpec Dense-Shutter Spectroscopy
Zihao Wu, Daniel J. Eisenstein, Francesco D'Eugenio et al. (+9 more)
We demonstrate the feasibility of source–line association in JWST/NIRSpec dense-shutter spectroscopy, with $\sim$2000 sources observed simultaneously per pointing regardless of spectral overlap. While JWST wide-field slitless spectroscopy (WFSS) can disentangle overlapping spectra using two grisms with perpendicular dispersion directions, NIRSpec can achieve this using gratings with different dispersions. Compared with WFSS, NIRSpec dense-shutter spectroscopy offers substantially higher sensitivity and broader wavelength coverage. We develop a
Bayesian framework that combines cross-dispersion offsets, wavelength consistency, and changes in relative line positions between gratings to jointly determine source associations and
redshifts. We test the method using mock observations based on the observed source distribution and emission-line fluxes from the JWST Advanced Deep Extragalactic Survey (JADES), accounting for the NIRSpec optical model, MSA operability, measurement noise, false-positive detections, and bad pixels. Although the spectral traces overlap extensively, fewer than 0.5% of the simulated emission lines are blended with another line on the detectors in NIRSpec grating spectroscopy. Applying our method to these simulations, we obtain
redshifts, at an accuracy of 98%, for the $\sim$1800 sources that have detectable emission lines, of which $\sim$1500 are classified as confident and are 99.9% accurate. We further investigate how the association accuracy depends on the number of grating configurations. By combining high multiplexing, high sensitivity, and broad wavelength coverage, NIRSpec dense-shutter spectroscopy enables efficient, highly complete spectroscopic surveys for the high-
redshift Universe.
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All authors Zihao Wu, Daniel J. Eisenstein, Francesco D'Eugenio, Erica Nelson, Benjamin D. Johnson, Andrew J. Bunker, Zhiyuan Ji, Pierluigi Rinaldi, Brant Robertson, Sandro Tacchella, Christopher N. A. Willmer, Joris Witstok
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA
The 2MIG isolated AGNs – 4. Linking hot-dust reverberation to spectroscopically predicted BLR scales in IC~5287 and Mrk~845
I.O. Izviekova, I.B. Vavilova, O.V. Kompaniiets et al. (+2 more)
We investigate the relation between directly measured hot-dust reverberation scales and spectroscopically predicted broad-line region (BLR) scales in the isolated Seyfert
galaxies IC~5287 and Mrk~845 (MCG+09-25-022), combining ZTF optical light curves, WISE/NEOWISE monitoring, and archival SDSS spectroscopy. Both
nuclei show BWB optical variability, RWB MIR behaviour, and delayed MIR responses consistent with circumnuclear dust reprocessing. For IC~5287, interpolated cross-correlation function analysis with flux-randomisation/random-subset-selection uncertainties yields a rest-frame W1 delay of $106_{-39}^{+24}$~d, corresponding to $0.089_{-0.033}^{+0.020}$~pc. The median W2 response occurs at a longer delay, but the lag distributions overlap substantially. The SDSS decomposition reveals strong host dilution and BLR reddening, $E(B-V)_{\rm BLR}=0.612_{-0.066}^{+0.067}$~mag. Applying the same colour excess to the AGN continuum as an illustrative scenario increases the predicted H$\beta$ BLR lag from approximately 4.8 to 11.7~d and reduces the dust-to-predicted-BLR radius ratios from approximately 20–25 to 8–10. For Mrk~845, transfer-function modelling gives a rest-frame W1 delay of $157_{-8}^{+19}$~d, corresponding to $0.132_{-0.007}^{+0.016}$~pc. Its W2 response occurs at a longer delay, with $P(\tau_{\rm W2}>\tau_{\rm W1})=0.963$, supporting wavelength-dependent hot-dust structure. The SDSS spectrum shows more moderate BLR reddening, $E(B-V)_{\rm BLR}=0.197_{-0.039}^{+0.046}$~mag. The comparatively large dust-to-predicted-BLR radius ratios in both
galaxies therefore primarily reflect the spectroscopically predicted BLR scales. These results emphasise the need to distinguish directly measured dust reverberation radii from BLR radii inferred from single-epoch spectroscopy when interpreting the BLR–dust hierarchy.
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All authors I.O. Izviekova, I.B. Vavilova, O.V. Kompaniiets, O. Zamora, R. Clavero
Instrumentation and Methods for Astrophysics
Stellar interferometry with a K-band integrated optics beam combiner instrument at the CHARA Array - I. First on-sky fringes for CHARIOT
Aline N. Dinkelaker, Kévin Barjot, Nic Scott et al. (+8 more)
We present the instrument description and the first on-sky observations for the new CHara ARray Integrated Optics Testbench (CHARIOT) at the CHARA Array. CHARIOT is a 2-
telescope proof-of-concept instrument that utilises a fibre-connectorised beam combiner fabricated by ultrafast
laser-inscription in Infrasil quartz glass, which presents low-OH contamination and high transparency over the whole K-band. With its fibre-connected architecture, CHARIOT is designed as a plug-and-play testbed instrument to test and validate fibred astrophotonic components on-sky. At this point, CHARIOT is able to measure raw fringe squared visibilities with a sub-1% precision for
stars with K-mag<2. Under poor to moderate seeing conditions, the current limiting magnitude for fringe detection is K-mag = 5.212 (HD210824). These results demonstrate that CHARIOT's performance is already comparable to the former JouFLU instrument. With additional improvements, the limiting magnitude could be extended and the precision for fainter
stars improved. The successful on-sky demonstration paves the way for a new high precision K-band beam combiner instrument at the CHARA array.
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All authors Aline N. Dinkelaker, Kévin Barjot, Nic Scott, Aurélien Benoît, Narsireddy Anugu, Alyssa V. Mayer, Jacopo Siliprandi, Robert R. Thomson, Kalaga Madhav, Gail Schaefer, Lucas Labadie
Instrumentation and Methods for Astrophysics
I2C@2024: an interferometric imaging contest in 2024
Florentin Millour, Mathis Houllé, Jeremy Perdigon et al. (+6 more)
Images in optical long-baseline interferometry have seen a boost in the recent years thanks to new techniques and recipes invented by the community. These images are more and more used for science interpretation and not only illustration, and their fidelity has improved significantly, thanks mainly to the increase in the number of
telescopes used in interferometers. The focus today is to improve their reliability and dynamic range. With this contest, we follow up the quest introduced in 2004 of comparing the state of the art image reconstruction software for long-baseline interferometry. This is done in a festive way in the form of an imaging contest, where the organizers propose simulated
datasets of targets, whose brightness distributions are meant to be blindly retrieved using various
algorithms by the contestants. A prize is offered to the winner of the contest. This year is not different from previous ones and we proposed to the contestants tools to compare their reconstructed images with original images. These tools are now distributed, together with example
datasets and images, enabling further tests at home of any image reconstruction tool.
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All authors Florentin Millour, Mathis Houllé, Jeremy Perdigon, Julien Drevon, Ryan Norris, Rebecca Proni, Alexis Matter, Ferreol Soulez, Eric Thiebaut
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.CO
MATISSE in the era of GRAVITY+
Florentin Millour, Anthony Soulain, Stéphane Lagarde et al. (+28 more)
MATISSE, the mid-infrared spectro-interferometric imager of the Very Large
Telescope Interferometer (VLTI), has been feeding on the light corrected by the
GRAVITY+ Adaptive Optics (GPAO) systems since the retirement of MACAO on the four Unit
Telescopes in 2024. We report the assessment of the new MATISSE performance with GPAO, based on commissioning observations obtained in 2024 and 2025 and compared with archival MACAO observations of the same stellar sources. The instrumental visibility transfer function is more stable in the L band, while its typical value in the L and N bands is unchanged; the visibility signal-to-noise ratio is consistent with, or better than, the values reported at the initial MATISSE commissioning. The correlated flux increases by 20–30% in GRA4MAT mode thanks to a better fringe tracking performance, and the total flux injected into the instrument increases by a factor of 1.3 to 1.4 (up to 1.7) in the L band at low spectral resolution, with no measurable loss in the N band. Combined with the new K-band fringe-tracking limits enabled by GPAO, this translates into a sensitivity gain of a factor 2 to 6 in the L and M bands, a confirmation of the N-band limits similar to the MACAO era. We then report the performances of MATISSE with the GPAO's
laser guide
stars in November and December 2025. The updated noise figures follow the exposure time calculator predictions in LM LOW and MED and come out better than them in N LOW, the L-band transfer function is stable at the few percent level between observing blocks an hour apart, and correlated fluxes, differential phases and closure phases are recovered down to a 10\,mJy target. Embedded young stellar objects and AGN are now within reach, thanks to the better performances on red targets brought by the
lasers. We finally discuss the science cases opened by this gain and the case for a future upgrade of the instrument.
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All authors Florentin Millour, Anthony Soulain, Stéphane Lagarde, Alexis Matter, Valentin Fleury, Farin Drewes, Mathis Houllé, Jules Scigliuto, Bruno Lopez, Anthony Meilland, G. Petrov Romain, Philippe Berio, Anthony Berdeu, Guillaume Bourdarot, Sylvestre Lacour, Mathias Nowak, Jean-Baptiste Le Bouquin, Antoine Mérand, Frank Eisenhauer, Julien Woillez, Miguel Montargès, Diogo Ribeiro, Taro Shimizu, Jens Kammerer, Xavier Haubois, Stefan Gillessen, Pierre Cruzalèbes, Frédéric Gonté, Walter Jaffe, James Leftley, Nicole Nesvadba
Instrumentation and Methods for Astrophysics
The best of all worlds: gravitational-wave transient detection with multiple pipelines
Nikolas Moustakidis, Theofilos Moustakidis, Deep Chatterjee et al. (+2 more)
The search for gravitational-wave transients (modeled and unmodeled) as performed by the LIGO-Virgo-KAGRA collaborations and the broader community typically involves multiple detection
algorithms, often redundant and sometimes complementary. We here address the problem of combining such detection
algorithms in order to maximize the noise vs signal discrimination power of such an astrophysical search that utilizes multiple analysis pipelines. Using a machine learning approach, we construct a neural network-based classifier that utilizes information (or lack thereof) from all participating pipelines in the search for compact binary coalescences in LIGO-Virgo-KAGRA's realtime (and offline) processing of gravitational-wave data. We
benchmark the method with simulated (astrophysical) signals and real noise from the instruments and obtain receiver operating characteristic curves to quantify its performance. We show how this leads to an effectively new, combined pipeline that outperforms any single pipeline alone or other logical combinations of them. This is particularly critical for real-time operations of the LIGO-Virgo-KAGRA detectors as such combination of detection methods can lead to increased robustness in identifying astrophysical sources and to reduction of the number of false alerts that may otherwise be sent out as astronomical telegrams. Our method also aims in simplifying the presentation of astrophysical results out of the LIGO-Virgo-KAGRA detectors by combining all participating pipelines in the astrophysical searches as well as optimizing resources by the broader multi-messenger astrophysics community in following up astronomical alerts for gravitational-wave transient events.
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All authors Nikolas Moustakidis, Theofilos Moustakidis, Deep Chatterjee, Anastasios Tefas, Erik Katsavounidis
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA
Improving Lens Modelling from Ground-Based Imaging with Deconvolution
Eric Paic, Kenneth C. Wong, Anupreeta More et al. (+1 more)
Accurate and precise mass modelling of strong
lensing systems is essential for extracting insights into cosmology,
galaxy environments, and the nature of dark matter. The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), which has mapped $\sim$1000 square degrees of the sky, discovered over 1000 definite or probable
galaxy-scale gravitational lens candidates. As the resolution of ground-based imaging poses challenges for accurate lens modelling, high-resolution imaging is traditionally sought after for detailed analyses of these systems. In this work, we instead propose applying the STARRED
algorithm, which leverages starlet wavelet regularisation, as a preprocessing step before lens modelling to maximise the scientific output of the large HSC-SSP sample. We test this approach on seven HSC-like mock
lensing systems with different
lensing configurations. Our results show that the resolution boost from $\sim$0.6" to $\sim$0.15" enables improved accuracy and sub-3% precision measurements of key
lensing parameters such as the Einstein radius and the mass axis ratio for ground-based images. These results pave the way for accurate measurements of key strong
lensing quantities from a large sample of ground-based observations.
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All authors Eric Paic, Kenneth C. Wong, Anupreeta More, Anton T. Jaelani