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Physics Astrophysics Instrumentation and Methods for Astrophysics

astro-ph.IM Watch Instrumentation and Methods for Astrophysics

Tuesday 18 August

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE

A deep learning algorithm for black hole spin estimation using hot-spot secondary images

Aristomenis I. Yfantis and Rami Al-Belmpeisi

Sagittarius A* exhibits frequent flaring activity across the electromagnetic spectrum that is often associated with a localized region of strong emission known as a hot spot. We aim to train a deep learning model to provide a link between key parameters of this phenomenon - hot-spot emission radius, and black hole inclination and spin - to the observed angle difference between the primary and secondary image ($\Delta PA$) that present and future interferometric arrays could resolve. Using the general relativistic radiative transfer code IPOLE, we generated a library of $\sim100.000$ models with varying system parameters and computed the position angle difference on the image plane between the primary and secondary images of the hot spot. We explore equatorial and non-equatorial circular orbits and evaluate our models against approximate observational constraints, including partial-orbit visibility and observational errors. Our algorithm STIHOS shows remarkable accuracy in calculating spin and inclination from the majority of the observational tests we perform ($\sigma_{a_*}=0.04,\,\sigma_i=2^{\circ}$), even in extreme conditions where only half of the orbit is visible. The off-equatorial estimation provides softer constraints in the absence of prior information. Our results demonstrate the importance of hot-spot observations for spacetime estimations. Given the increasing efforts to detect the photon-ring, our framework could prove valuable in interpreting the first observations of lensed emission.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.LG

Safe Domain Adaptation for Physics: Overcoming Nuisances, Label Shifts, and Simulation Priors

Ivan Kharuk

Domain adaptation is widely used to make neural networks trained on simulations applicable to experimental data. Its premise is that the two domains differ only in nuisances, and that the quantity of interest is distributed identically in both. In physics neither assumption holds: simulations can be wrong about the physics, and the distribution of the target quantity - an energy spectrum, a redshift distribution - is often the measurement itself. We study the consequences of such mismatches on a toy air-shower benchmark in which a detector-response nuisance, a physical simulation shift, and an energy-spectrum shift can be switched on separately or together. Standard adversarial adaptation handles the conditional shifts, but once the two spectra differ it aligns them, replacing an uncontrolled bias by one anchored on the simulation prior. We present adaptive domain adaptation, which reweights the simulated events so as to focus domain adaptation on the genuine physical mismatch alone. Since the predicted spectrum depends on model training configuration, we provide a label-free model selection rule for selecting the near-the-best operation point.
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Instrumentation and Methods for Astrophysics

Variable Star Polarimetry with PICSARR-2

Daniel V. Cotton, Jeremy Bailey, Logan Barrett et al. (+3 more)

We describe the upgraded Polarimeter using Imaging CMOS Sensor and Rotating Retarder 2 (PICSARR-2), describe its applications, and characterize its performance for stellar polarimetry on a 36-inch and 14-inch telescope. On the larger telescope in the SDSS $g^\prime$, $r^\prime$ and $i^\prime$ filters a precision of $\sigma_p=$ 5.7 ppm on bright stars is recorded using a fast modulation rate corresponding to frame exposures of 12 ms; accounting for the internal errors in the individual observations gives a limiting precision of $e_p=$ 1.3 ppm. Longer frame rates are required for stars with $m > 5$, but the recorded errors only underperform a photon shot noise derived extrapolation for $m > 8$, when even longer frame exposures are required. Stars as faint as $m = 11$ were observed. The position angle precision is measured as 0.0845 degrees, and there is very good agreement between observations made by both the PICSARR-2 and HIPPI-2 polarimeters. On the smaller telescope the instrument's performance approaches similar levels, and there is good cross-platform stability in the observation of standard stars. PICSARR-2 is therefore an excellent instrument to explore stellar variability due to a range of phenomena; examples from our ongoing pulsating star campaign and other variable star programs are presented.
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All authors Daniel V. Cotton, Jeremy Bailey, Logan Barrett, Glenn Henderson, Kim Sumagang, Eric C. Haase

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: data reduction pipeline astrometric calibration

Amanda Chavez, Jason Wang, Vanessa P. Bailey et al. (+5 more)

The Nancy Grace Roman Space Telescope will be equipped with a Technology Demonstration Coronagraph Instrument that will push the current limits of high contrast imaging for exoplanets ($10^{-9}$ contrast). The Roman Coronagraph Community Participation Program has developed corgidrp, a python-based data reduction pipeline for the Roman Coronagraph Instrument that will perform essential data processing and calibration steps for coronagraphic observations. The astrometric calibration function within corgidrp allows us to understand the on-sky angular size and distance scale of science observations by characterizing essential detector parameters: boresight, plate scale, north angle, and optical distortion. Measuring these astrometric calibration products not only helps us understand the science output of our data, but it is what allows us to point the Roman coronagraph accurately at our science target in the first place. Here, we describe the techniques used within the astrometric calibration and demonstrate that our algorithm meets Technology Demonstration Threshold Requirements: (1) compute the on-sky location of the center of CGI EXCAM detector to better than 30 [mas] and (2) compute the on-sky position angles of the camera axes to within 0.3 [deg].
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All authors Amanda Chavez, Jason Wang, Vanessa P. Bailey, Maxwell Millar-Blanchaer, Julien Girard, John Krist, Julia Milton, Marie Ygouf

Instrumentation and Methods for Astrophysics

Vera C. Rubin LSST Synthetic Magnitudes derived from Gaia XP Spectra

Oleksandra Razim, Krešimir Tisanič and Lovro Palaversa

Context. In the context of Milky Way studies, the Vera C. Rubin Observatory's Legacy Survey of Space and Time is often described as a deep extension of the Gaia survey. In the future, joint analysis of the Gaia and LSST data promises to bring new insights into our understanding of the Galaxy's structure and formation history. However, the relatively small overlap in the magnitude ranges of the two surveys raises the question of how to perform a joint calibration of these datasets. Aims. In this paper, we produce high-quality synthetic LSST photometry from Gaia XP low-resolution spectra, using SDSS and DES observed photometry to calibrate the spectra. Methods. We develop a method of empirical correction of Gaia XP spectra using SDSS Stripe 82 photometry. We project sources for which Gaia XP data are available onto a magnitude-magnitude grid and calculate residuals between uncorrected synthetic and observed SDSS magnitudes, which are then used to derive correction coefficients across spectral regions corresponding to each photometric band. Results. The correction significantly reduces systematic trends and scatter in the synthetic magnitudes: the median residuals decrease by an order of magnitude (e.g., for the u band the improvement is from 0.038 to 0.002 mag), and the standard deviation of residuals typically becomes up to factor of two smaller (e.g., for the u band from 0.2 to 0.07 mag). Conclusions. Our correction approach improves the reliability of synthetic photometry derived from Gaia XP spectra and enables joint analysis of Gaia and LSST data for studies of Galactic structure and stellar populations.
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Instrumentation and Methods for Astrophysics

Accurately simulating gain and clock-induced charge production in the EMCCD gain register

Kevin J. Ludwick

An electron-multiplying charge-coupled device (EMCCD) is capable of precise detections in low-signal environments, able to detect a single photon through electron multiplication. It has many applications, such as faint-target astronomy, quantum optics, molecule tracing, and others, and it will be used for faint companion detection in the Roman Telescope's coronagraph instrument. In an EMCCD, photons hit the pixels, and photo-electrons are created; these are multiplied via impact ionization as they travel through the gain register from one gain stage to the next. A high gain means a high multiplication factor, and this is achieved through a high voltage difference across a gain stage. If the gain is high enough, the chance of clock-induced charge (CIC) production in the gain register increases. The probability distribution function governing the gain process typically used only accounts for charge multiplication if one or more electrons enter the gain register. I discuss my implementation of the simulation of this effect and its customization in emccd_detect, the EMCCD detector simulator used for the Roman Telescope. In addition, the simulator has been updated to use the exact binomial distribution for EM gain instead of the approximate Gamma distribution usually used in the literature, which is only valid for large counts. I also examine some EMCCD data and show through maximum likelihood estimation with CIC_gain_register that the data conform better to the binomial distribution versus the approximate Gamma/Erlang distribution. The use of the modified distribution would in principle improve the fidelity of Roman's testing and lead to better EMCCD calibration and more accurate signal extraction from a frame.
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Instrumentation and Methods for Astrophysics

Simulation tools for realistic high-order wavefront correction with the Roman Coronagraph

A. Lau, A. J. Riggs, S. F. Redmond et al. (+9 more)

The Roman Space Telescope Coronagraph Instrument (Roman CGI) will demonstrate high-contrast imaging from space using coronagraphic masks, deformable mirrors, and high-order wavefront sensing and control (HOWFSC). After the baseline technology demonstration, the Roman Coronagraph Community Participation Program (CPP) will pursue science and engineering studies that require realistic predictions of instrument behaviour, observing efficiency, and wavefront control performance. This paper describes corgihowfsc, a configurable simulation framework for repeatable Roman CGI HOWFSC studies. The framework preserves the Roman ground-in-the-loop (GITL) workflow represented by the NASA cgi-howfsc package, while allowing the images to be generated by the higher-fidelity corgisim model. In this configuration, cgi-howfsc remains the reference implementation for estimation, control, and compact-model Jacobian generation; corgisim can supply more flight-like images for studies of instrument performance and robustness. corgihowfsc also coordinates exposure planning, camera settings, expected iteration timing, and contrast normalisation of the HOWFSC loop through cgi-eetc, calibration-related workflows through cgi-coralign, structured diagnostics, and local or distributed execution. By exposing observing modes, image models, probe choices, estimators, controllers, deformable-mirror settings, and runtime options through reusable configuration files, corgihowfsc enables controlled comparisons between reference compact-model simulations and higher-fidelity HOWFSC studies.
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All authors A. Lau, A. J. Riggs, S. F. Redmond, E. Cady, J. Krist, I. Laginja, D. Sirbu, L. Delaye, R. Soummer, S. Noiret, J. C. Lambert, A. Bidot

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: Using the Zernike wavefront sensor for a full characterisation of the Roman Space Telescope and the Coronagraph Instrument

Arthur Vigan, Alexis Bidot, Vincent Chambouleyron et al. (+4 more)

The Roman Space Telescope Coronagraph Instrument (CGI) will demonstrate a series of technologies and techniques to enable the direct detection of reflected-light planets with space-based observatories. Among the several available observing modes and coronagraphic devices embarked in CGI, there is the transmissive dual-path Zernike wavefront sensor (ZWFS) that could be used to directly measure optical aberrations in the system. The dual-path ZWFS is currently unsupported, but in this work we advocate for the commissioning of this unique observing mode. We investigate the sensitivity of the ZWFS using CGI simulator and other tools developed and supported by the Roman community participation program (CPP). This type of analysis is crucial for understanding the stability of the Roman observatory and to prepare the path towards HWO.
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All authors Arthur Vigan, Alexis Bidot, Vincent Chambouleyron, Garreth Ruane, Laurent Pueyo, Mamadou N'Diaye, Kjetil Dohlen

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.CO

A stochastic forward model for the intergalactic dispersion-measure distribution of Fast Radio Bursts

Jéferson A. S. Fortunato, Valerio Marra, Wiliam S. Hipólito-Ricaldi et al. (+1 more)

Fast Radio Bursts probe ionised baryons through their observed dispersion measures. We present \turbofrb, a semi-analytic stochastic forward model for the intergalactic dispersion-measure distribution, $P({\rm DM}_{\rm IGM}\mid z)$, that resolves the diffuse IGM, halo, and filament contributions as explicit physical channels, with the halo and filament encounter rates coupled by a latent line-of-sight environmental variable. Only four effective parameters are calibrated against hydrodynamical ray-traced IllustrisTNG benchmark. The model matches the benchmark mean DM to the percent level and yields a per-redshift Jensen-Shannon divergence of at most $5\times10^{-3}$ across $z = 0.5$-$2.5$. The per-sightline channel decomposition makes explicit what closed-form parametric descriptions cannot show: the diffuse IGM sets the body of the distribution, while halos and filaments populate the high-DM tail. Applied to representative localised FRBs, the forward likelihood quantifies host-excess events independently of their astrophysical signatures and recovers the injected $H_0$ within $1\sigma$ in a closed-loop consistency test. The \turbofrb package is available at \href{https://github.com/jefersonfortunato/turbofrb}{github.com/jefersonfortunato/turbofrb}.
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All authors Jéferson A. S. Fortunato, Valerio Marra, Wiliam S. Hipólito-Ricaldi, Amanda Weltman

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE

SST-1M: Recent results and prospects for observation of the Galactic Center region

Jakub Juryšek and for the SST-1M Collaboration

The Galactic Center is a crowded region containing powerful particle accelerators and objects producing non-thermal radiation, including the diffuse very-high-energy (VHE) gamma-ray component known as the `Ridge', whose hard spectrum suggests particle acceleration up to PeV energies. The relevant processes can be tested, and the source parameters can be constrained via Cherenkov telescope observations. Two Single-Mirror Small-Size Cherenkov Telescopes (SST-1M) are currently operated in stereoscopic mode at the Ondřejov Observatory. Their future relocation is being considered, including a site with excellent visibility of the Galactic Center. We present recent observations demonstrating SST-1M capabilities for detecting extended emission and discuss prospects for probing the Galactic Center region, including searches for a spectral cut-off above 10 TeV. We show that the large field-of-view and good VHE sensitivity make SST-1M an ideal instrument for the search for PeVatrons.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE

NMMA-Astro-COLIBRI: An Automated Light-Curve Supernovae Classification Service in the Multi-Survey Era

R. Weizmann Kiendrebeogo, Bernardo Cornejo Avila, Sofia Bisero et al. (+6 more)

The surge in publicly available photometric alerts from wide-field surveys requires automated tools for real-time transient classification. We present NMMA–Astro-COLIBRI, an on-demand Bayesian classification service that couples the Nuclear-physics and Multi-Messenger Astrophysics (NMMA) inference framework to the Astro-COLIBRI real-time multi-messenger platform. After the detection of an optical transient, if photometry is available, it is quality-filtered. The filtered photometry is fitted by nested sampling against a user-selected model from a library of eleven supernova templates; results are delivered to every user within minutes. Applying two or more models on the same optical transient, the service reports the corresponding log Bayes factors as a quantitative ranking of competing subtypes. We demonstrate the workflow on SN 2021ugl (ZTF21abotose), a Type IIb supernova initially mistaken for a kilonova candidate by automated real-time pipelines, comparing competing supernova and kilonova models. In an early-time configuration using only the first ~ 6 days of photometry in two bands (ZTF g and r), so ten days before spectroscopic confirmation, the empirical Type IIb template recovers the correct classification, favored over both the kilonova template and the kilonova-mimicking shock-cooling model. In the full 47-day, three-band baseline, it again achieves the highest evidence over every competing supernova and kilonova template. These results highlight the importance of a comprehensive supernova template library for kilonova discrimination in the multi-survey era.
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All authors R. Weizmann Kiendrebeogo, Bernardo Cornejo Avila, Sofia Bisero, Maxime Cellier, Antoine Ciric, Ilja Jaroschewski, Henrik Rose, Alexandre Saint-Paul, Fabian Schüssler

Instrumentation and Methods for Astrophysics · Cross-listed from nucl-th

Generative artificial intelligence for reconstructing neutron-star matter

Julia Yu. Panteleeva, Herzallah Alharazin and Evgeny Epelbaum

Neutron-star cores hold the only known matter in the universe that is simultaneously cold and strongly interacting, compressed beyond nuclear density into a state of unknown composition. The equation of state links stellar masses, radii and tidal deformabilities to this regime, but recovering this key quantity from sparse observations is an ill-posed inverse problem. Existing analyses bury a prior in a fixed functional form, unevenly weighting admissible solutions and biasing the result. We reconstruct the equation of state with a denoising diffusion model that keeps prior, physics and data separate: it learns an inspectable, physically motivated prior anchored to first-principles nuclear theory, while perturbative-QCD and astrophysical constraints are imposed exactly. Future measurements therefore will update the posterior by reweighting alone, without retraining or resampling. The inferred radius of 12.6 km and tidal deformability of 469 at 1.4 solar masses reproduce Gaussian-process and heavy-ion-informed inferences despite a far broader prior. We find near-conformal but still stiff matter in the heaviest stars, consistent with a gradual hadron-quark crossover and disfavouring a strong first-order phase transition. More broadly, coupling a learned prior to exactly enforced physics establishes a template for ill-posed inverse problems where theory and data constrain different regions.
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Instrumentation and Methods for Astrophysics

EON-SII: Design of a transportable picosecond stellar intensity interferometer for compact-star astrophysics

Thomas Schweizer, Josef Eder, Jürgen Besenrieder et al. (+5 more)

Stellar intensity interferometry (SII) measures correlations in photon-arrival fluctuations recorded by telescopes observing bright celestial sources. It can resolve angular scales far smaller than those accessible to a single optical telescope and is largely insensitive to atmospheric turbulence. After the first demonstration of SII on Sirius in 1956, Hanbury Brown and Twiss used the technique to measure the diameters of 32 stars. More recently, VERITAS, MAGIC, H.E.S.S., and CTAO's LST-1 have revived the method, although observations remain restricted to bright targets because of their optical design, optimized for gamma-ray astrophysics, rather than SII. We present EON-SII, the design and performance of a two-telescope intensity interferometer intended to extend the SII technique to compact targets at magnitudes of about V=8.5 up to V=10.7. Each transportable telescope has a 4-m diameter mirror, approximately 9m2 collecting area, an actively aligned 18-panel primary mirror, and Cassegrain optics specified to concentrate at least 90% of the light within 3 arcsec. A fibre-free spectrograph covers 400-550 nm at R~7000-8000 and is designed to provide of order 1000 statistically independent spectral channels.
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All authors Thomas Schweizer, Josef Eder, Jürgen Besenrieder, Razmik Mirzoyan, Carina Haider, Olaf Reimann, Derek Strom, Roland Walter

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: calibration strategy for the Mueller matrix using on-sky sources

Toshiyuki Mizuki, Justin Hom, Bertrand Mennesson et al. (+14 more)

The Nancy Grace Roman Space Telescope Coronagraph Instrument will provide space-based polarimetric observations of circumstellar disks and exoplanetary systems. Accurate reconstruction of the linear polarization fraction requires calibration of the instrumental Mueller matrix using polarized and weakly polarized standard stars. We constructed a candidate catalog by combining published optical polarimetry with Gaia DR3 astrometry and photometry and selected separate samples for coronagraphic calibration observations and observations using a neutral-density filter. Precursor $VRI$-band polarimetry of 18 faint candidates was obtained with HONIR on the 1.5-m Kanata telescope. The wavelength dependence of their normalized Stokes parameters was modeled using the Serkowski law to predict their polarization properties in \cgi\ Bands~1 and 4, and 2 sets of 3 calibrators were selected for the 2 calibration scenarios. We then estimated the achievable LPF reconstruction accuracy using Monte Carlo simulations that include uncertainties in the calibrator polarization properties, photometric noise, and residual detector-response errors. A dithered observing configuration was also simulated to reduce differential detector-response errors among the calibrators. The current estimates indicate LPF reconstruction errors at the few-percentage-point level, with a small bias arising from treating a weakly polarized calibrator as unpolarized. Finally, we present progress toward an end-to-end test using corgisim and corgiDRP, including successful processing of simulated datasets from Level~1 through Level~2b.
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All authors Toshiyuki Mizuki, Justin Hom, Bertrand Mennesson, Ramya M. Anche, Maxwell A. Millar-Blanchaer, Vanessa P. Bailey, Koji Kawabata, Mitsuhiko Takeuchi, Motohide Tamura, Naoshi Murakami, John Livingston, Jason J. Wang, Schuyler G. Wolff, Guillermo Gonzalez, Eric Shen, Tsutsumi Nagai, Taichi Uyama

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: early calibration plan and pilot observation of a companion

Julien H. Girard, Eric Cady, Neil T. Zimmerman et al. (+42 more)

Roman is set to launch in weeks! The Coronagraph Instrument - technology pathfinder for future direct imaging missions - is ready to fly too. According to predictions, laboratory tests and high fidelity simulations, it will open a new contrast regime enabling the imaging of mature, giant planets in visible reflected light. The Community Participation Program is responsible for preparing a comprehensive observing program with associated data processing software and calibrations. We give a brief update about the on-going "baseline" calibration plan for the first months. Additionally, we describe a pilot program aiming for the stellar companion HD 29992 B at moderate ~1e-5 to ~1e-6 Band 1 (575 nm) contrast, to be carried out as soon as the instrument is operational. The idea is to generate a canonical data set with a self luminous companion that is easily recoverable. This functional checkout will be precious to best prepare our community, exercise our calibration plan and suite of tools.
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All authors Julien H. Girard, Eric Cady, Neil T. Zimmerman, Clarissa R. Do Ó, Jingwen Zhang, Guillermo Gonzalez, Bijan Nemati, Vanessa P. Bailey, Alexis Lau, Sophie Noiret, John Krist, Julia Milton, Marie Ygouf, Ramya M. Anche, Schuyler Wolff, Justin Hom, Amanda Chavez, Jason J. Wang, Maxwell A. Millar-Blanchaer, Jessica Gersh-Range, Matthias Samland, Macarena Vega-Pallauta, Wolfgang Brandner, Toshiyuki Mizuki, Masayuki Kuzuhara, Susan Redmond, Kevin Ludwick, Jaren N. Ashcraft, William O. Balmer, Rusland Belikov, Beth Biller, Sarah Blunt, Ellis Bogat, Oscar Carrión-González, Gael Chauvin, Alexandra Z. Greenbaum, Sebastiaan Haffert, Jim Ingalls, Brian Kern, Bertrand Mennesson, Laurent Pueyo, Dmitry Savransky, Dan Sirbu, Peter Williams, Chen Xie

Instrumentation and Methods for Astrophysics · Cross-listed from physics.plasm-ph

The FLARE Facility

Hantao Ji, Jongsoo Yoo, Peiyun Shi et al. (+53 more)

The Facility for Laboratory Reconnection Experiments (FLARE) has been constructed to study magnetic reconnection in multiple X-line regimes relevant to space, astrophysical, and fusion plasmas. Building upon the successful design of the Magnetic Reconnection Experiment (MRX), FLARE features a larger physical volume, stronger magnetic fields, and an independent ohmic heating drive to significantly extend the accessible parameter space, targeting Lundquist numbers up to S ~ 10^5 and normalized system sizes up to \lambda ~ 10^3. This paper details the facility's core engineering components, including the primary vacuum vessel, internal flux cores, highly segmented external coil systems, modular capacitor banks, and the safety interlock and control architecture. An initial diagnostic suite is presented, comprising high-resolution 2D magnetic probe arrays, triple Langmuir probes, a fully fiber-coupled interferometer, ion Doppler spectroscopy, and fast camera imaging. Initial operations demonstrate the device's experimental flexibility and reliability, successfully executing symmetric push-pull reconnection, spheromak merging, and asymmetric downstream configurations. Currently operating within "Stage 2.5" with S ~ 2,500 and \lambda ~ 60 for anti-parallel reconnection, FLARE provides immediate access to the multiple X-line regimes. Planned hardware upgrades, advanced diagnostic additions, and integration with fully kinetic simulations will further expand its capabilities as it transitions into a collaborative user facility for the broader plasma science community.
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All authors Hantao Ji, Jongsoo Yoo, Peiyun Shi, Euichan Jung, Kush Maheshwari, Adam Robbins, Sunghyun Son, Adam Stanier, Yang Ren, Sayak Bose, Dylan Corl, Keith Corrigan, Robert Cutler, William Daughton, Robert Ellis, Geoffrey Gettelfinger, Ronald Hatcher, Philip Heitzenroeder, Frank Hoffmann, Jonathan Jara-Almonte, Michael Kalish, Thomas Kozub, Enrique Merino, Weiguo Que, Benjamin Smith, John Wallace, Xin Zhao, Sofia Avrutsky, Neal Crocker, Seth Dorfman, Yuka Doke, Corina Dunn, William Fox, Boting Li, Xiaocan Li, Clayton Myers, Shohgo Okazaki, Joshua Pawlak, Tongnyeol Rhee, Byonghoon Seo, Taiju Suzuki, Yang Zhang, Stuart Bale, Amitava Bhattacharjee, Troy Carter, Chuanfei Dong, James Drake, Jan Egedal, Erik Gilson, Michiaki Inomoto, Jonathan Menard, Yasushi Ono, Stewart Prager, John Sarff, Hiroshi Tanabe, Masaaki Yamada

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: corgisim - a simulation suite for the Nancy Grace Roman Space Telescope Coronagraph Instrument

Jingwen Zhang, Sophie Noiret, Maxwell A. Millar Blanchaer et al. (+14 more)

NASA's Roman Space Telescope will feature a pathfinder Coronagraph Instrument to demonstrate advanced high-contrast imaging from space, paving the way for future missions like the Habitable Worlds Observatory. The Coronagraph Instrument could obtain imaging, polarimetry and spectroscopy of Jupiter analogs in reflected visible light for the first time. We present the development of an open-source simulation package “corgisim” as part of the Roman Coronagraph Community Participate Program. Built on established optical propagation libraries including PROPER and CGISim, corgisim provides a user-friendly, publicly available Python framework for end-to-end simulations of the Coronagraph Instrument observations. The package produces high-fidelity, format-compliant data for pre-launch calibration, pipeline testing, and community applications such as target selection and observation planning. We will give an overview of corgisim's infrastructure, functionalities, and current implementation across planned imaging, polarimetry, and spectroscopy modes, including the ability to simulate host stars, injected companions, and extended disks. We will also highlight suitable applications of corgisim and provide guidance on how users can access and employ the software.
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All authors Jingwen Zhang, Sophie Noiret, Maxwell A. Millar Blanchaer, Jason Wang, Alexis Lau, Neil Zimmerman, Jessica Gersh-Range, Eric Shen, Kevin Ludwick, Taichi Uyama, Chen Xie, Vanessa P. Bailey, John Krist, Elodie Choquet, Julien Girard, Alexis Bidot, Arthur Vigan

Monday 17 August

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP

Astro-Hunters: Machine Learning for Exoplanet Transit Detection in TESS Photometry

Fatimah Emad Eldin

Finding planets beyond the Solar System is now largely a data-analysis problem: photometric surveys return far more stellar light curves than can be inspected by eye, and machine learning is increasingly asked to recognise the faint, periodic dimming of a transiting planet. Whether such a detector works turns on a choice that is seldom reported: how its training labels were made. No catalogue disposes the individual measurements a per-cadence detector must classify, so the annotation has to be derived, and this paper asks what that costs. We present Astro-Hunters, an end-to-end pipeline over TESS two-minute photometry: retrieval, detrending, seven sliding-window statistics per cadence, and gradient-boosted classification. These components are deliberately conventional. What is new is the treatment of label provenance as an experimental variable, a corpus of 189,279 cadences from twelve confirmed hosts annotated from published ephemerides rather than from the photometry, and a physical bound on what the task permits. Six classifier families are compared under a star-disjoint protocol. Holding features, model and protocol fixed, precision–recall performance spans a factor of 29 across label sources against 1.8 across architectures. Labels from an isolation forest fitted to the classifier's own features give an apparent AUC of 0.9915 that measures circularity; an unconverted transit epoch drives performance to chance; correct annotation gives AUC 0.788 at 5.3 times the prevalence baseline. The ceiling is observational, not architectural: a median single-cadence signal-to-noise ratio of 2.10 caps per-cadence AUC at 0.932. A Box Least Squares baseline recovers eight of twelve orbital periods from one sector. Phase-folding, not classifier capacity, is what makes the transit signal accessible.
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Instrumentation and Methods for Astrophysics

On-sky demonstration of dual-field interferometry at the CHARA Array

Narsireddy Anugu, John D. Monnier, Douglas R. Gies et al. (+10 more)

Dual-field interferometry uses a bright reference star for real-time fringe tracking, allowing a second beam combiner to record long coherent integrations on a fainter off-axis science target. At the Center for High Angular Resolution Astronomy (CHARA) Array, we implement this mode using the six-telescope MIRC-X and MYSTIC beam combiners in the H and K bands, respectively. We first demonstrated this capability in summer 2025 on the hierarchical triple $\alpha$~Piscium. MIRC-X tracked component A in the $H$ band, while MYSTIC observed component B in the K band, resolving the 7~mas Ba–Bb subsystem and measuring the relative astrometry of the 1.85~arcsec A–B pair with an uncertainty of 234~$\mu$as. Here, we describe subsequent phase-tracking testing, preliminary sensitivity simulations, and planned instrumental upgrades aimed at extending this mode to faint off-axis science targets.
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All authors Narsireddy Anugu, John D. Monnier, Douglas R. Gies, Jeremy Jones, Robert Klement, Stefan Kraus, Rainer Köhler, Karolina Kubiak, Cyprien Lanthermann, Edgar R. Ligon, Denis Mourard, Gail H. Schaefer, Nicholas J. Scott

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: target database and tools

Dmitry Savransky, Rifah Tasnim, Saanika Choudhary et al. (+13 more)

The Nancy Grace Roman Space Telescope, set to launch in Fall 2026, will carry the Coronagraph Instrument, which will, for the first time, demonstrate high-contrast imaging with active wavefront control in visible wavelengths from space. In preparation for execution of the Coronagraph's commissioning and observing programs, the Roman Coronagraph Community Participation Program (CPP) has developed a target database and associated ecosystem of publicly accessible tools for observation planning and scheduling. The target database includes both stars and known sub-stellar companions and disks that may be observed by the Coronagraph instrument during its primary mission. Targets in the database include planet and disk hosts as well as calibration stars, reference stars, and engineering program targets. The database is designed to operate in conjunction with a variety of tools, including an exposure time calculator, a pointing and keepout calculator, and a reference star selection tool. Here, we describe the current schema and contents of the database and demonstrate how it and its associated tools are being used for observation planning.
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All authors Dmitry Savransky, Rifah Tasnim, Saanika Choudhary, Hovik Grigoryan, Justin Hom, Bijan Nemati, Neil Zimmerman, Ramya Anche, Nicholas Phillips, Louie Donesa, Parth Mittal, Amira Razack, Savaas Iqbal, Javier Majumdar, Schuyler G. Wolff, Vanessa P. Bailey

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: Observation planning and data reduction for polarimetric mode

Ramya M Anche, Toshiyuki Mizuki, Justin Hom et al. (+25 more)

Reflected-light polarimetry of exoplanets constrains and resolves degeneracies in atmospheric properties, while polarized light observations of debris disks enable the characterization of dust-grain properties. The best-effort polarimetric mode of the Roman Coronagraph Instrument will be able to perform multi-wavelength observations of planetary systems using both the Hybrid Lyot Coronagraph (HLC) and the Shaped Pupil Coronagraph (SPC). This paper presents an overview of observation planning, simulations, and data reduction procedures for the polarimetric mode of the Roman Coronagraph. As an initial test of simulation and data reduction, a dataset of polarimetric observing sequences for the debris disk HD 172555 in HLC mode was generated using corgisim with estimated observation parameters, and data reduction was performed using corgidrp, incorporating all relevant noise factors and calibration products. Currently, mock calibration products are used in corgidrp; these will be replaced with simulated calibration products in future updates
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All authors Ramya M Anche, Toshiyuki Mizuki, Justin Hom, Alexis Lau, Saanika Choudhary, Jaren N. Ashcraft, Clarissa Do O, Tsutsumi Nagai, Sophie Noiret, Eric Shen, Taichi Uyama, Chen Xie, Jingwen Zhang, Vanessa P. Bailey, Eric Cady, Jessica Gersh-Range, Julien H. Girard, Guillermo Gonzalez, John Livingston, Bertrand Mennesson, Maxwell A. Millar-Blanchaer, Julia Milton, Naoshi Murakami, Dmitry Savransky, Motohide Tamura, Jason J. Wang, Schuyler G. Wolff, Marie Ygouf

Instrumentation and Methods for Astrophysics

Simulating Zernike-based CWFSing with HCIPy

Klaus Subbotina Stephenson and Kate Jackson

This work explores optimal sensing distances in Zernike-based Curvature WaveFront Sensing (CWFS). By using HCIPy, an open-source Python package, we simulate the first 100 Zernike modes at a variety of propagation distances (1 to 20,000 m) to explore the relationship between the propagation of a wavefront and its spatial complexity to understand an idealized CWFS' sensitivity to individual modes. We find that there exist distinct optimal sensing distances for low-spatial-order-modes, with high-spatial-order modes demonstrating grouping behavior at exponentially shorter optimal sensing distances. Our results indicate that there is a sensitivity gap in current CWFSing that can be resolved by resorting to a high number of sensing planes for the low spatial order regime, with one sensing plane for each individual low-order mode; similarly, we propose several high-order regime sensing planes, with each sensing plane dedicated to small groups of localized modes centered around the highest modal sensitivity at a given propagation distance. We also discuss the caveats in dealing with high-order Zernike modes and the need for carrying out further propagation analysis in the Fourier space to extend preliminary work presented here. Lastly, we suggest the development of a new reconstruction algorithm that weighs the ability to reconstruct a complete wavefront according to the sensitivity (gain) to each mode at an individual sensing distance.
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Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: trials and triumphs of designing an observing program for a technology demonstration instrument

Schuyler G. Wolff, Vanessa P. Bailey, Justin Hom et al. (+19 more)

The Coronagraph Instrument onboard the Nancy Grace Roman Space Telescope serves as a crucial technology pathfinder for the Habitable Worlds Observatory, with on-sky verification of high-contrast imaging techniques and the potential to image a Jupiter analog in reflected light for the first time. Together with the Roman Project Team, the Community Participation Program (CPP) is responsible for target selection, preparatory observations, developing an exposure time calculator, target database, data reduction pipeline, simulation tools, and engagement with the broader community. Here we present an overview of the CPP activities over the past two years with an emphasis on observation planning activities for the initial in-orbit checkout and the first six months of the observation phase. Finally, we present future opportunities for the astronomical community to interact with the data as it becomes public early in the mission.
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All authors Schuyler G. Wolff, Vanessa P. Bailey, Justin Hom, Beth Biller, Dmitry Savransky, Julien H. Girard, Ellis Bogat, Óscar Carrión-González, Clarissa R. Do Ó, Masayuki Kuzuhara, Chen Xie, Maxwell Millar-Blanchaer, Susan Redmond, Johan Mazoyer, Macarena Vega-Pallauta, Gael Chauvin, Matthieu Ravet, Alexandra Greenbaum, Eric Cady, Ramya Anche, James Ingalls, the Roman Coronagraph Community Participation Program Team

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: pre-launch reference star list and impact of reference star properties on post-processing performance

Justin Hom, Schuyler G. Wolff, Jessica Gersh-Range et al. (+51 more)

The upcoming Roman Coronagraph will be the first high-contrast instrument in space capable of high-order wavefront sensing and control technologies, a critical technology demonstration for the proposed Habitable Worlds Observatory (HWO) that aims to directly image and characterize habitable exoEarths. The nominal Roman Coronagraph observing plan involves alternating observations of a science target and a bright, nearby reference star for both wavefront calibration and reference differential imaging post-processing. Reference star criteria for the most demanding coronagraph mode are restrictive, limiting the sample to only 40 candidates for which thorough observational vetting is needed to assess their suitability. Reference star properties such as resolved diameters, presence of circumstellar dust, and close point sources may also have more subtle impacts on post-processing efficacy that may inhibit final contrast performance. In this work, we describe the current progress of the CoronaGraph Instrument Reference stars for Exoplanets (CorGI-REx) observing campaign, a 300+-hour observing campaign that utilizes instruments from around the world to vet reference stars for high-order wavefront control suitability. We will present the pre-launch list of reference star candidates being utilized for the Roman Coronagraph Observation Phase constructed from a thorough analysis of high contrast and interferometric observations. We will also present the results of simulations investigating the impact of reference star resolved diameters and companions on post-processing performance. We conclude by discussing the importance of reference star selection for scheduling observations and optimizing contrast performance for the Roman Coronagraph along with implications for HWO coronagraph operations.
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All authors Justin Hom, Schuyler G. Wolff, Jessica Gersh-Range, Ramya M. Anche, Vanessa P. Bailey, Jean-Philippe Berger, Beth A. Biller, Wolfgang Brandner, Marah Brinjikji, Gaël Chauvin, David R. Ciardi, Catherine A. Clark, Laird M. Close, Robert J. De Rosa, Sarah Deveny, Warren B. Foster, Julien H. Girard, Alexandra Z. Greenbaum, Olivier Guyon, Sebastiaan Y. Haffert, Alexander D. Hedglen, Steve B. Howell, Parker T. Johnson, Maggie Y. Kautz, Jay K. Kueny, Masayuki Kuzuhara, Manon Lallement, Rico Landman, Colin Littlefield, Jean-Baptiste Le Bouquin, Jialin Li, Joshua Liberman, Joseph D. Long, Miles Lucas, Jennifer Lumbres, Bruce Macintosh, Jared R. Males, Eric Mamajek, Matthijs Mars, Eden A. McEwen, Avalon L. McLeod, Maxwell A. Millar-Blanchaer, Toshiyuki Mizuki, Sophie Noiret, Tiffany Nguyen, Lauren Schatz, Nicholas T. Schragal, Adam K. Taras, Elena Tonucci, Katie Twitchell, Kyle Van Gorkom, Macarena C. Vega-Pallauta, Jason J. Wang, Jingwen Zhang

Instrumentation and Methods for Astrophysics

pynucastro 3: A community library for nuclear astrophysics

Zhi Chen, Khanak Bhargava, Eric T. Johnson et al. (+8 more)

We describe the latest release of pynucastro: a community python library for nuclear astrophysics. The goal of the pynucastro project is to build the tools needed to interactively explore nuclear properties, reaction rates, and networks, and to export these networks to a variety of simulation codes. Major changes in pynucastro since the last major release include new rate approximations, a stellar equation of state, support for the StarLib library and rate uncertainties, and new tools for exploring networks.
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All authors Zhi Chen, Khanak Bhargava, Eric T. Johnson, Reth Lopes, Melissa Rasmussen, Alexander Smith Clark, Michael Zingale, Brendan Boyd, Kiran Eiden, Sam Glosser, Don E. Willcox

Instrumentation and Methods for Astrophysics

The Roman Coronagraph Community Participation Program: data reduction pipeline design and implementation

Jason J. Wang, Maxwell A. Millar-Blanchaer, Marie Ygouf et al. (+39 more)

The Roman Space Telescope Coronagraph Instrument will demonstrate a series of technologies and techniques to enable the direct detection of reflected-light planets with space-based observatories. To characterize and validate the performance of the Coronagraph Instrument, the Community Participation Program is developing corgidrp, an open-source Python-based data reduction pipeline. The pipeline can process data from the required and best-effort observing modes and their associated calibration sequences into calibrated science-ready data products. We present the software design and implementation of corgidrp and the motivation behind specific design decisions. We describe the software architecture, data flow, processing steps, automation tools, testing framework, and development philosophy. We also outline future development plans in preparation for on-sky data.
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All authors Jason J. Wang, Maxwell A. Millar-Blanchaer, Marie Ygouf, Julia Milton, Jürgen Schreiber, Kevin J. Ludwick, Ellis Bogat, Amanda Chavez, Eric Shen, Aneesh Baburaj, Ramya Anche, Toshiyuki Mizuki, Taichi Uyama, Ezar Shinbaro, Alexis Lau, Neil T. Zimmerman, Sophie Noiret, William Balmer, Ben J. Sutlieff, Adrien Maillard, Matthias Samland, A J Eldorado Riggs, Clarissa Do Ó, Jingwen Zhang, Giovanni M. Strampelli, Lisa Altinier, Michael Liang, Jessica Gersh-Range, Kylee Fluckiger, John Livingston, Malachi Noel, Dmitry Savransky, Michele Woodland, Tsutsumi Nagai, Justin Hom, Al Niessner, Cynthia Wong, Eric J. Cady, Vanessa P. Bailey, Guillermo Gonzalez, Alexandra Z. Greenbaum, Enrico Biancalani

Instrumentation and Methods for Astrophysics · Cross-listed from physics.comp-ph

Validating direct solvers for Newton's gravitational N-body problem, and the systematic comparison between IEEE floating point and Posits

Simon Portegies Zwart

We present a systematic comparison between arbitrary precise arithmetic and integration, IEEE-754 compliant floating point arithmetic (fp16, bfp16, fp32, double precision fp64, and quadruple precision fp128), and two implementations of Posits (type III unum) for solving Newton's chaotic N-body problem. Each implementation is benchmarked with arbitrary precise calculations to objectively evaluate their performance in precision as well as speed. We rely on hardware and compiler implementations for fp64, and software implementations for arbitrary-precision arithmetic and Posits. Half precision arithmetic (fp16, bfp16, and Posits$<16,1>$) are insufficiently precise for solving Newton's equations of motion. Single precision (fp32, and Posits$<32,2>$) could be used for statistical ensemble calculations, but lead to relatively large errors in any individual strong encounter. All 64-bit implementations fp64 as well as Posits (Posits$<64,3>$) experience difficulty in our tests. One of the implementations of Posits (Universal) gives precision comparable to fp64 but is slow (by at least an orders of magnitude compared to fp64 after correcting for the more efficient hardware support for the latter). The other (CPPPosits) has a speed comparable to fp64 but has systematically larger errors (by about an order of magnitude compared to fp64 with excesses exceeding two orders of magnitude). As a consequence, this implementation leads to a systematic drift in the result space and has difficulty resolving close encounters. Posits and fp64 have difficulty when integrating a dynamical system in a moving reference frame; testing Galileo invariancy. In their current implementation, Posits do not seem to be the ideal alternative for fp64 when integrating chaotic or stiff ordinary differential equations, such as Newton's equations of motion.
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Instrumentation and Methods for Astrophysics

A novel technique for reflection coefficient measurement in precision cosmology

Adarsh Kumar Dash, Yash Agrawal, Somashekar R. et al. (+7 more)

The detection of the global 21-cm signal from the Cosmic Dawn and Epoch of Reionisation remains a challenge to experiments worldwide. Emitted at a rest-frame frequency of 1420.405~MHz, this signal from the early Universe is redshifted to 40-200~MHz with a maximum brightness temperature of a few 100~mK. Efforts to detect this sky-averaged signal include experiments such as the Shaped Antenna measurement of the background RAdio Spectrum (SARAS) and Probing ReionizATion of the Universe using Signal from Hydrogen (PRATUSH). Detecting this faint signal requires precise calibration of the antenna, which includes a high-precision measurement of its reflection coefficient. This measurement must be performed in situ at the observation site, as the antenna characteristics vary significantly with the environment. PRATUSH, a space-based radiometer, faces the additional challenge of structural distortions induced by thermal cycling, necessitating multiple measurements of the reflection coefficient. This work highlights the development of an in situ Vector Network Analyser, which utilises a novel noise source-based calibration scheme and a cross-correlation spectrometer to perform magnitude and phase measurements of the complex reflection coefficient of the antenna. Further, we demonstrate the performance of the designed network analyser using independent measurements from a precision network analyser and reflection coefficient modelling of the device under test. We find the level of non-smooth calibration systematics, which need critical control for 21-cm signal detection, to be about $10^{-5}$. Finally, we study the impact of reflection coefficient correction on sky measurements, highlighting its usability for precision 21-cm observations.
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All authors Adarsh Kumar Dash, Yash Agrawal, Somashekar R., Jayadev Ashok T., Keerthipriya S., Vishwapriya Gautam, Saurabh Singh, Mayuri Sathyanarayana Rao, Girish B. S., Srivani K.S

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP

SCExAO/CHARIS High-Contrast Pre-Launch Vetting of Roman Coronagraph Technology Demonstration PSF Reference Stars

Thayne Currie, Jie Li, Mona El Morsy et al. (+9 more)

We present deep, SCExAO/CHARIS high-contrast integral field spectroscopy and archival imaging of four candidate Roman Coronagraph PSF reference stars within/near the Roman Continuous Viewing Zone and potentially suitable for the Coronagraph's key technology demonstration targets HIP 71618 and HIP 54515. For CHARIS data, we achieve 5-$\sigma$ contrasts down to $\sim$1.4$\times$10$^{-5}$, $\sim$6$\times$10$^{-6}$, and 10$^{-6}$ to 4$\times$10$^{-7}$ at 0\farcs{}16, 0\farcs{}25, and 0\farcs{}5 to 1\arcsec{}. Companion mass limits rule out brown dwarfs at $\rho$ $\sim$ 0\farcs{}15–0\farcs{}25 and massive planets at wider separations around all targets. More critically, for three of the four references our analysis disfavors companions with $V$ band contrasts brighter than 10$^{-8}$, 10$^{-9}$, and $10^{-10}$ at 0\farcs{}15, 0\farcs{}3, and 1$\arcsec{}$. Unless these targets have faint substellar companions within $\rho$ $\sim$ 0\farcs{}15, they likely lack background stars or companions that could corrupt the Roman Coronagraph's dark hole digging to preclude detecting reflected-light planets. For $\alpha$ Cep, our limits are a factor of $\sim$10 worse but still meet the TTR5 limit of 10$^{-7}$ beyond $\rho$ $\sim$ 0\farcs{}25: beyond 0\farcs{}4, they exclude a Jupiter-twin reflected-light companion (10$^{-9}$). Archival Keck/NIRC2 data likewise find no substellar companions with $\Delta$V $>$ 10$^{-8}$ at wider separations. Finally, we assess the observability of HIP 71618 and HIP 54515 – updated for Roman's launch date of August 30, 2026. Adding $\gamma$ Boo – not currently in the Roman CPP team reference-star list – would improve schedulability for the tech demo's key targets.
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All authors Thayne Currie, Jie Li, Mona El Morsy, Olivier Guyon, Julien Lozi, Erica Dykes, Danielle Bovie, Sebastien Vievard, Garima Singh, Kyohoon Ahn, Vincent Deo, Yoshito Ono

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE

Resolving Nearby Supermassive Black Holes with the Black Hole Explorer

Yuto Akiyama, Kazunori Akiyama, Dominic W. Pesce et al. (+12 more)

Recent Event Horizon Telescope results have demonstrated unique and transformative science in gravitational physics and black hole astrophysics enabled by event-horizon-scale imaging of supermassive black holes (SMBHs). Nevertheless, the angular resolution of current ground-based very long baseline interferometry (VLBI) arrays limits such studies to only two sources, precluding systematic investigations of horizon-scale emission across a nearby SMBH population. The proposed Black Hole Explorer (BHEX), a millimeter/submillimeter space VLBI mission, would overcome this limitation by delivering substantially higher angular resolution. Here, we present a series of simulated observations to assess a population of nearby horizon-scale targets accessible with BHEX. Based on a recently developed SMBH number density model, we find that BHEX could infer black hole masses for ~70-90 sources from size measurements, constrain magnetic field structures through linear polarization imaging for ~20-30 sources, and resolve black hole shadows for ~20-25 sources. Targeted observations of ~50 nearby SMBHs are expected to yield measurements for ~30 source sizes and ~10 shadows and linear-polarization patterns. These projections are supported by detailed imaging simulations of general relativistic magnetohydrodynamic (GRMHD) models for eleven nearby SMBHs. Together, our results highlight BHEX as a powerful facility for revealing the demographics of SMBH properties across diverse accretion states, radio loudness, host galaxy environments, and viewing geometries.
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All authors Yuto Akiyama, Kazunori Akiyama, Dominic W. Pesce, Daniel C. M. Palumbo, Angelo Ricarte, Paul Tiede, Marvin N. Martinez, Hikaru Yoshida, Avery E. Broderick, Aya E. Higuchi, Sara Issaoun, Neil M Nagar, Kotaro Niinuma, Venkatessh Ramakrishnan, Xinyue Alice Zhang