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Physics Astrophysics Instrumentation and Methods for Astrophysics

astro-ph.IM Watch Instrumentation and Methods for Astrophysics

Monday 31 August

Instrumentation and Methods for Astrophysics

DINOspec: Efficient Multimodal Alignment of Vision and Spectral Foundation Models for Astronomy

Erica Lastufka, Mariia Drozdova, Daniel Schaerer et al. (+1 more)

Astronomical observations provide multimodal views of physical systems, with images and spectra capturing complementary properties of celestial objects. Scientific foundation models can learn powerful representations from these observations, but representations learned by separate models remain difficult to combine. We investigate whether physical representations learned by separate vision and spectral models can be aligned without retraining their encoders. We introduce DINOspec, a multimodal framework that aligns a frozen DINOv3 image encoder with a pre-trained AION-1 spectral tokenizer using lightweight adapters and contrastive learning on 20,472 paired images and spectra of astronomical objects. DINOspec improves galaxy morphology classification (F1: 0.72$\rightarrow$0.78) and spectral classification (F1: 0.70$\rightarrow$0.74) while training at most 21M parameters. Improvements depend on the downstream task, revealing asymmetric transfer between independently learned representations, while spectroscopic redshift prediction remains unchanged ($R^2\approx0.9$). These results demonstrate that scientific foundation models can be composed through lightweight representation alignment.
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All authors Erica Lastufka, Mariia Drozdova, Daniel Schaerer, Svyatoslav Voloshynovskiy

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

SNAD: enabling discovery in the era of big data

Maria Pruzhinskaya, Emille E. O. Ishida, Konstantin Malanchev et al. (+8 more)

In the era of wide-field surveys and big data in astronomy, the SNAD team is exploiting the potential of modern datasets for discovering new, unforeseen, or rare astrophysical objects and phenomena with machine learning (ML). The SNAD pipeline was built under the hypothesis that, although automatic ML algorithms have a crucial role to play in this task, the scientific discovery is only completely realized when such systems are designed to boost the impact of domain knowledge experts. Our key contributions include the development of the Coniferest Python library, which offers implementations of two active learning algorithms with an “expert in loop”, and the creation of the SNAD Transient Miner, facilitating the search for specific types of transients. We have also developed the SNAD Viewer, a web portal that provides a centralized view of individual objects from the Zwicky Transient Facility's (ZTF) data releases, making the analysis of potential anomalies more efficient. Finally, when applied to ZTF data, our approach has resulted in more than a hundred new supernova (SN) candidates, along with a few other non-catalogued objects, such as red dwarf flares, superluminous SNe, RS CVn type variables, and young stellar objects.
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All authors Maria Pruzhinskaya, Emille E. O. Ishida, Konstantin Malanchev, Anastasia Lavrukhina, Etienne Russeil, Timofey Semenikhin, Sreevarsha Sreejith, Emmanuel Gangler, Matwey Kornilov, Vladimir Korolev, Alina Volnova

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

Broad-band host measurements of little red dots and similar compact nuclei require source-conditioned polychromatic PSFs

Sergio Bonaque-González

Characterizing compact sources in the early Universe is difficult because light from physically distinct components can overlap within the same diffraction-limited image. A common method uses field stars to model how a single point of light appears and from this estimates the intrinsic structure and contributions of the physical components of the distant object under study. Many important properties inferred for high-redshift objects depend on the accuracy of this method. Using the little red dots (LRDs) analysed by Zhang et al. as a test case, this work shows that applying the method through broad filters to objects whose spectra differ from those of the field stars can systematically misassign light, overestimating an existing extended component or creating an apparent one where none exists. At the measured level, this error is large enough to alter the inferred sizes, luminosities and masses, and therefore the physical interpretation of these systems. The physical and mathematical origin of the error is established and a correction applicable to other compact distant sources is demonstrated.
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Sunday 30 August

Instrumentation and Methods for Astrophysics

CRUX: A topology-aware load balancer for mesh-based fluid dynamics codes on GPU clusters

M.T.P. Liska and C. Crozier

The rapid growth of computational power has revolutionized numerical simulations, profoundly enhancing our understanding of fluids and plasmas. Computational fluid dynamics (CFD) simulations, which solve partial differential equations governing fluid or plasma motion on discretized grids, have been central to this progress. Recent advances have pushed the resolution and runtime of legacy numerical models to unprecedented levels while enabling newer codes to incorporate increasingly sophisticated physics. However, further scaling of these simulations has become a significant challenge, largely due to the comparatively modest improvements in networking capabilities relative to the rapid growth of floating-point performance in modern GPU-accelerated clusters. In this article, we introduce a novel load-balancing routine CRUX designed to scale efficiently for the most demanding CFD grids in astrophysics. Unlike traditional approaches based on space-filling curves, our method dynamically accounts for computational cost disparities among mesh blocks evolved with different timesteps while minimizing communication overhead. It is also able to take into account heterogeneous hardware. Through an extensive suite of benchmarks featuring up to 5,400 GPUs on OLCF Frontier and ALCF Aurora, we demonstrate that our load-balancing algorithm outperforms space-filling curve methods across all key metrics, including load uniformity, memory consumption, and communication efficiency, making it a robust solution for next-generation CFD simulations.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA

Caught Napping by JWST UNCOVER+MegaScience: Constraining bursty star formation histories and number densities of mini-quenched galaxies at redshifts 4-7

Gourav Khullar, Rachel Bezanson, Katherine A. Suess et al. (+27 more)

We explore the prevalence of mini-quenched or “napping” galaxies selected from spectroscopic and photometric samples in the UNCOVER/MegaScience survey. These galaxies are empirically identified by the presence of moderate Balmer breaks, weak emission lines ($EW(H\alpha) < 100$A) and relatively blue UV continua. We infer the star formation histories (SFHs) of our sample using flexible non-parametric models with Prospector optimized to capture recent episodes of bursty star formation and quenching, and find that they are uniquely identifiable in the SFR$_{10}$/SFR$_{100}$ parameter space moving towards (temporary) quiescence. We demonstrate that although spectroscopy is best able to identify rapidly declining SFRs, densely sampled medium-band photometry recover these key spectral features and thus robustly identify pure samples of this transient phase – with imaging alone. We quantify the number density of napping galaxies at $z=4-7$ in the Abell 2744 lensing field, finding 8 spectroscopically confirmed nappers and 60 photometric candidates spanning log$_{10}$(M$_*$/M$_\odot$) $= 7.5-10$. We verify that the photometry alone can identify a pure sample of nappers, leveraging a smaller high signal-to-noise ratio spectroscopic sample. Consistent with previous studies, we find that nappers are most common at low stellar mass (log$_{10}$(M$_*$/M$_\odot$) $\sim9$). We see a hint that the number densities increase from $z\sim6$ to $z\sim4$, though our small sample is likely affected by cosmic variance. Our study demonstrates the increasing importance of stochastic star formation as a regulator of low-mass galaxy growth in the several hundred Myr after reionization, and offers a direct observational testbed for the strength and duty cycle of stellar feedback in cosmological simulations.
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All authors Gourav Khullar, Rachel Bezanson, Katherine A. Suess, Ikki Mitsuhashi, David J. Setton, Joel Leja, Sedona H. Price, Katherine E. Whitaker, Emilie Burnham, John R. Weaver, Iryna Chemerynska, Lukas J. Furtak, Jenny Greene, Bingjie Wang, Hakim Atek, Gabe Brammer, Olivia R. Cooper, Robert Feldmann, Seiji Fujimoto, Anna de Graaff, Ivo Labbe, Danilo Marchesini, Ian McConachie, Tim B. Miller, Abby Mintz, Themiya Nanayakkara, Pascal Oesch, Richard Pan, Casey Papovich, Yunchong Zhang

Instrumentation and Methods for Astrophysics

A generalized likelihood model for segmented muon counters

Joaquín de Jesús, Juan Manuel Figueira, Federico Sanchez et al. (+1 more)

Measurements of the muonic component of extensive air showers constrain cosmic-ray mass composition and hadronic interactions at energies beyond those accessible at accelerators. Arrays of segmented detectors with binary readout are widely used for this purpose: they sample the muon density at different distances from the shower core to reconstruct the muon lateral distribution function (LDF). Each detector response is summarized by the number of activated segments, $k$, whose probability distribution provides the likelihood relating the observation to the expected muon content. Signal pile-up, detector inefficiency, corner-clipping muons, and background signals shape this distribution, and neglecting them can bias the reconstruction. Existing analytical models include pile-up but otherwise assume an ideal detector response. In this work, we develop a unified statistical framework that incorporates inefficiency, corner clipping, and background through a small set of physically interpretable parameters. We derive exact expressions for the detector response and the likelihood required for muon-LDF reconstruction, together with a simple binomial approximation that preserves the main statistical properties of the exact distribution. Dedicated Monte Carlo simulations are used to assess the impact of the assumptions underlying the analytical treatment and show that it is negligible over the parameter range considered. They also show that the exact and approximate likelihoods yield similar performance in terms of estimator bias and confidence-interval coverage. Although motivated by the Underground Muon Detector of the Pierre Auger Observatory, the framework applies more broadly to segmented particle detectors with binary readout in which particle content is inferred from the number of activated segments.
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All authors Joaquín de Jesús, Juan Manuel Figueira, Federico Sanchez, Darko Veberic

Instrumentation and Methods for Astrophysics

Soft proton experiments supporting the development of astronomical X-ray instrumentation

S.J. Diebold, B. Heß, F. Pfeifle et al. (+11 more)

Orbital soft protons can severely degrade the performance of astronomical X-ray observatories. On the one hand, they may cause permanent radiation damage to X-ray detectors; on the other hand, they introduce an irreducible background component. Our low-energy grazing-incidence scattering setup provides experimental data for the validation of radiation transport simulations used in the assessment of future X-ray missions. Recent measurements indicate that a significant fraction of protons scattered from X-ray optics undergo charge exchange and therefore cannot be mitigated by magnetic diverters. In addition, we present initial proton-transmission measurements through a thin X-ray filter and compare them qualitatively with TRIM simulations. Quantitative measurements of energy loss and charge-exchange fractions, together with comparisons with TRIM and Geant4, are planned. In this publication, we present the upgraded experimental setup together with commissioning measurements for grazing-incidence scattering and proton transmission through thin X-ray filters.
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All authors S.J. Diebold, B. Heß, F. Pfeifle, L.Ph.H. Schmidt, C. Tenzer, T. Wildfang, D. Ferreira, M. Freyberg, S. Massahi, D. Paredes-Sanz, E. Perinati, A. Santangelo, B. Stelzer, S. Svendsen

Instrumentation and Methods for Astrophysics · Cross-listed from quant-ph

Imaging Stars at the Quantum Compatibility Limit

Xinyao Guo, Haixing Miao, Zheng Cai et al. (+1 more)

Imaging astrophysical sources with a multi-station interferometer is intrinsically a multiparameter quantum-estimation problem. {Using tools from multiparameter quantum metrology,} we show that time-resolved repetitive or adaptive measurements in an \(N\)-station array suffer a fundamental array-level incompatibility among visibility estimators. Collective measurements, {which coherently process the received starlight across multiple time bins in a single joint readout}, remove the array-size penalty up to an order-unity factor, yielding an asymptotic \(O(\sqrt{N})\) enhancement for the {directional-averaged} SNR of visibility measurement. We then propose a memory-assisted interferometric architecture designed to implement collective readout through coherent storage and joint quantum processing. Imaging simulations and Fisher-information analyses demonstrate that collective measurements improve image reconstruction in near-term arrays and enhance the resolving power of future long-baseline architectures, with pronounced benefits for representative AGN targets such as NGC~4151 and 3C~273. These results highlight collective measurement as a promising building block for future quantum-assisted interferometric arrays for stellar imaging.
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All authors Xinyao Guo, Haixing Miao, Zheng Cai, Huan Yang

Instrumentation and Methods for Astrophysics

Microchannel plate detector development for ultraviolet astronomy

S. Diebold, J. Barnstedt, J. Bayer et al. (+8 more)

Observational data from the UV wavelength range is crucial to solve several astrophysical puzzles. Consequently, there are a number of upcoming UV missions from CubeSats up to the future flagship Habitable Worlds Observatory. Besides novel instrument concepts and improved coatings, advanced detectors are key for the success of these missions. The microchannel plate (MCP) detector technology offers a unique asset in the UV: the combination of single-photon counting and visible-blindness. The UV hardware group at the Institut für Astronomie und Astrophysik Tübingen (IAAT) develops a versatile MCP detector system that addresses the complete UV band. While a sealed-tube design is limited to wavelengths above 118\,nm, an open-face variant also covers the whole far- and extreme-UV. Both use the same readout: a coplanar cross-strip anode and FPGA-based electronics. In this contribution, we report on the status of the detector development, present the latest characterization results, and give an outlook on the mission prospects.
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All authors S. Diebold, J. Barnstedt, J. Bayer, L. Conti, H.R. Elsener, C. Kalkuhl, D. Rau, D. Schaadt, T. Schanz, B. Stelzer, K. Werner

Instrumentation and Methods for Astrophysics

Self-calibration of adaptive optics systems. Application to the THEMIS solar telescope

Clementine Bechet, Eric Thiebaut, Michel Tallon et al. (+3 more)

The interaction matrix models the effects of deformable mirror (DM) commands as perceived by the wavefront sensor (WFS) and is the cornerstone of the Adaptive Optics (AO) control. Difficulties to calibrate this matrix arise due to the number of degrees of freedom, the non-linearity, and temporal evolution of the AO system. An affine approximation of the unknown mapping between the DM commands and the WFS measurements is considered. Optimal estimators of the parameters of this affine model are obtained by fitting, in the weighted least squares sense, WFS data acquired with random probe commands sent to the DM. Several calibration methods are being considered depending on whether the model is directly fit to the WFS data or to the differences between successive WFS data. We derive closed-form expressions of the estimators of the components of the model. The proposed calibration methods can be applied under different conditions: before observing, on an internal source, or on-sky in open- or closed-loop. By introducing forgetting factors to reduce the weight of data as they age, we show that the model can be learned continuously using simple recurrence rules. The low computational complexity of these rules makes them suitable for real-time at the same frequency as the AO loop. We derive simple expressions for the mean squared errors (MSE) of the proposed estimators. We apply the proposed calibration methods to real telemetry data from the AO system of the THEMIS solar telescope. Our results show that the simple differences method is the method of choice: not only does it produce estimators with the least MSE, but it is also very simple to implement compared to the push-pull method which is widely used in AO systems.
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All authors Clementine Bechet, Eric Thiebaut, Michel Tallon, Isabelle Tallon-Bosc, Bernard Gelly, Richard Douet

Instrumentation and Methods for Astrophysics

AO3k + SCExAO: on-sky wavefront quality and demonstration of novel WFS techniques with the double XAO system

Julien Lozi, Kyohoon Ahn, Vincent Deo et al. (+5 more)

The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system, fed by its upstream 3000-actuator "woofer" (AO3k), serves both as a platform for high contrast imaging (HCI) technology maturation and as a science instrument for imaging, spectroscopy, and polarimetry of exoplanets and disks. SCExAO operates in the visible and near-IR and offers a wide choice of instrument configurations. Over the last year, AO3k/SCExAO underwent significant upgrades to bring improved capabilities and support new developments, all while easing science operations. The new configuration features a beam switcher so that light can be shared between several instrument modules. The system is evolving toward a tighter integration between multiple WFSs and AO stages of correction, with the first stage (AO3k) providing visible and nearIR WFSing, as well as laser tomography. AO3k+SCExAO has been fully operational since October 2025, demonstrating very high stability on-sky, even in bad seeing conditions up to 2". Having two XAO in series allows us to deploy advanced wavefront control techniques optimized for high-contrast imaging (e.g. speckle nulling, EFC, Coronagraphic LOWFS, Fast and Furious) on the second-stage XAO loop, as AO3k by itself delivers high-contrast PSFs already. Areas of active ongoing research include use of photonic devices for spectrally dispersed interferometric sensing, PSF reconstruction from WFS telemetry, and non-linear sensors (focal plane and curvature). Recent upgrades to the computer infrastructure are aimed at supporting these R&D efforts and providing a rich collaborative environment for experimentation. In this paper, we will present on-sky high-contrast performance characterization of AO3k, AO3k+SCExAO, and on-sky demonstrations of novel wavefront control techniques to improve the contrast behind the coronagraph.
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All authors Julien Lozi, Kyohoon Ahn, Vincent Deo, Olivier Guyon, Sandrine Juillard, Yoshito Ono, Garima Singh, Sébastien Vievard

Saturday 29 August

Instrumentation and Methods for Astrophysics · Cross-listed from cs.LG

Efficient Context-Limited Telescope Bibliography Classification for the WASP-2025 Shared Task Using SciBERT

Madhusudhana Naidu

The creation of telescope bibliographies is a crucial part of assessing the scientific impact of observatories and ensuring reproducibility in astronomy. This task involves identifying, categorizing, and linking scientific publications that reference or use specific telescopes. However, this process remains largely manual and resource intensive. In this work, we present an efficient SciBERT-based approach for automatic classification of scientific papers into four categories - science, instrumentation, mention, and not telescope. Despite strict context-length constraints (maximum 512 tokens) and limited compute resources, our approach achieved a macro F1 score of 0.89, ranking at the top of the WASP-2025 leaderboard. We analyze the effect of truncation and show that even with half the samples exceeding the token limit, SciBERT's domain alignment enables robust classification. We discuss trade-offs between truncation, chunking, and long-context models, providing insights into the efficiency frontier for scientific text curation.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP

A semi-analytical surrogate model for giant planet evolution: bypassing ordinary differential equation solvers with localised thermodynamics, softplus asymptotes, and B-spline photometry

Christian Wilkinson, Jonas Wehrung-Montpezat, Benjamin Charnay et al. (+7 more)

Context. Evolutionary models translate the observable luminosity, temperature, and colours of giant planets and brown dwarfs into mass and age. Generating their cooling tracks normally requires integrating the internal energy over time with an ordinary differential equation (ODE) solver coupled to pre-computed atmospheric grids, which becomes numerically stiff at sharp transitions such as cloud condensation and the onset of electron degeneracy, and is fragile inside Bayesian retrievals. Aims. We aim to generate continuous cooling tracks and photometric light curves directly from discrete atmospheric grids, without an ODE solver. Methods. We mapped the grids into a logarithmic thermodynamic space and extracted localised surrogate models with Gaussian-weighted regressions at fixed planetary parameters. We fitted the entropy and cooling rate against the internal temperature using bounded piecewise softplus functions to capture structural and cooling-rate transitions; the radius was fitted on the same temperature axis; and band photometry was represented with fixed-knot cubic B-splines. The age followed from numerical integration of these analytic functions, and uncertainties were propagated from the residual scatter of each fit. Results. The surrogate, CoolTrack, reproduces the transition into electron degeneracy and the L-to-T spectral-type transition in the colour-magnitude diagram, converges on Solar System benchmarks, and evaluates a full evolutionary track in milliseconds on a standard desktop CPU. Conclusions. By removing the forward-modelling bottleneck, CoolTrack is suitable for direct use in Bayesian retrieval pipelines, where the age, mass, and formation entropy of a planet can be inferred jointly with its atmospheric properties.
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All authors Christian Wilkinson, Jonas Wehrung-Montpezat, Benjamin Charnay, Mathilde Mâlin, Lukas Delaye, Anne-Marie Lagrange, Vito Squicciarini, Johan Mazoyer, Stéphane Mazevet, Baptiste Perrier

Instrumentation and Methods for Astrophysics

Characterization of the stabilized nulling interferometry testbed PERSÉE

Julien Lozi

Observing exoplanets is hindered by high stellar contrast and tiny angular separation. Nulling interferometry addresses this by recombining two pupils for destructive interference on the star and constructive interference on the planet. However, maintaining deep nulls despite external disturbances requires sub-nanometer optical path difference (OPD) stability and sub-hundredth Airy disk pointing control. To validate this technology for a space mission, the PERSEE laboratory demonstrator bench was developed by a CNES-led consortium and integrated at the Meudon Observatory. Simulating a complete space mission setup, PERSEE targeted a stable star extinction rate of 1e-4 with variations of 1e-5 over several hours under simulated disturbances. The thesis focused on the multi-stage integration, calibration, and characterization of the bench's critical components and cophasing control loops. By implementing a Linear Quadratic Gaussian (LQG) controller optimized through preliminary disturbance measurements, the system mitigated multi-frequency vibrations (1-100 Hz, tens of nanometers amplitude), reducing residual OPD to 0.3 nm RMS and tip-tilt errors to 0.4 percent of the Airy disk. These stabilization controls achieved a record null rate of 8.8e-6 with 9e-7 stability over several hours in the 1.65-2.45um spectral band, surpassing initial specifications by an order of magnitude. Extrapolating these results to space missions indicates that with 40 cm telescopes and 100 Hz control loops, exoplanet observations are feasible for stars brighter than 9th magnitude.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

Automated identification and subtraction of gravitational-wave glitches using boundary refinement

Mohammad Abu Thaher Chowdhury and Soumya D Mohanty

Transient noise artifacts, or glitches, in gravitational wave strain data elevate the false alarm rate of astrophysical searches and degrade parameter estimation when overlapping a signal. No method previously identified a glitch's time boundary: existing detection and classification tools flag and label glitches without resolving their extent, forcing subtraction to run over padded windows that cost time and erase signal beyond the glitch itself. We present three boundary identification methods, AMPS (Amplitude-based Multi-glitch Pulse Segmenter), FLARE (Fitness-based Localization And Refinement Extractor), and CRISP (connected-region identification via spectrogram power), paired with three subtraction techniques, adaptive spline fitting, wavelet shrinkage, and their combination, across five glitches from the GravitySpy database spanning Advanced LIGO's first three observing runs. AMPS sets a boundary from a robust amplitude threshold, FLARE from the best fitness of a segmented spline fit, and CRISP from spectrogram power. Injecting a chirp signal on four broadband glitches, the combined technique recovers 95 to 97 percent of the injected signal-to-noise ratio, against roughly 64 percent for wavelet shrinkage alone. CRISP gives the most uniform boundary width across glitches; AMPS and CRISP both identify a boundary in a fraction of a second, two to three orders of magnitude faster than FLARE. For the glitch overlapping GW170817, a low-frequency residual persists under the default boundary, a deliberate tradeoff against removing signal power. Scattered light glitches remain untested and are the primary direction for future work.
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Instrumentation and Methods for Astrophysics

How nanoscale physics shapes ice formation in the Universe: Rethinking gas freeze-out on dust grains

Philippe Parent, Carine Laffon, Stefano Curiotto et al. (+3 more)

In cold molecular clouds, gas freeze-out onto dust grains initiates interstellar ice formation, yet sticking probabilities of heavy species are often assumed to be near unity at low temperature. Recent laboratory measurements on realistic grain analogues show that this assumption can fail. Using CO as a prototype, we investigate how nanoscale surface morphology controls adsorption and ice growth at 10 K on highly oriented pyrolytic graphite and carbon soot. X-ray photoelectron spectroscopy, low-temperature scanning tunneling microscopy, kinetic Monte Carlo simulations, and a thermodynamic description are combined to relate molecular retention to local surface structure. CO does not adsorb with unit sticking on graphite: adsorption proceeds through monolayer growth, a reduced-retention crossover near monolayer completion, and delayed multilayer growth. STM shows that CO remains highly mobile on graphite terraces and is stabilized mainly at island edges and terrace steps. On soot, the same sequence occurs at much higher exposures and with substantially lower sticking coefficients, while simulations show preferential retention in concave regions and poor wetting of convex asperities. These results indicate that low-temperature sticking is governed by post-impact exploration and competition between stabilization and escape. Nanoscale morphology amplifies this mechanism, reducing effective sticking probabilities and delaying gas freeze-out on realistic dust grains.
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All authors Philippe Parent, Carine Laffon, Stefano Curiotto, Daniel Ferry, Caroline Stadler, Frederik Granzow Doktor

Instrumentation and Methods for Astrophysics

First overnight balloon flight of the GRAINE 2023 emulsion gamma-ray telescope enabled by a large-scale pressure-vessel gondola

Hiroki Rokujo, Shigeki Aoki, Takashi Azuma et al. (+34 more)

The Gamma-Ray Astro Imager with Nuclear Emulsion (GRAINE) project conducts precision observations of sub-GeV–GeV cosmic gamma rays using a balloon-borne nuclear-emulsion telescope with high angular resolution. In GRAINE 2023, a 2.5-m$^{2}$ telescope was flown in the project's first overnight balloon flight, including observation periods for the Vela pulsar and Galactic center region. To operate the telescope under the low-pressure and low-temperature stratospheric environment, the balloon-style pressure-vessel concept was scaled up to a lightweight gondola with an internal length of 4.9 m. A new aluminum-alloy ring structure and a lightweight membranous-shell material, SHL-300MDL, were developed. While the telescope aperture was increased by a factor of 6.6 over GRAINE 2018, the pressure-vessel gondola mass was limited to 179 kg. Ground tests of the completed flight assembly demonstrated a differential pressure above 100 hPa at room temperature and at a mean temperature of $-66.0^{\circ}$C. The payload was launched from Alice Springs, Australia, in April 2023 and achieved a total flight duration of approximately 27 h, including 24.3 h of level flight. Although the upper membranous shell reached approximately $-60^{\circ}$C at night, the vessel internal pressure remained above the required 100 hPa throughout level flight. These results demonstrate that the developed gondola can accommodate a 2.5-m$^{2}$ emulsion gamma-ray telescope and maintain the required pressure during overnight stratospheric flight. Scientific analyses of astrophysical and atmospheric gamma rays, including dedicated analysis of the Galactic center region, are ongoing using the recovered emulsion data. This development provides a technical basis for repeated observations with future large-area GRAINE telescopes.
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All authors Hiroki Rokujo, Shigeki Aoki, Takashi Azuma, Hirotaka Hayashi, Yudai Isayama, Atsushi Iyono, Takumi Kato, Tsuyoshi Kawahara, Koichi Kodama, Ryosuke Komatani, Masahiro Komatsu, Masahiro Komiyama, Hideyuki Minami, Kunihiro Morishima, Fumiya Murakami, Shogo Nagahara, Naotaka Naganawa, Mitsuhiro Nakamura, Tomoaki Nakamura, Yuya Nakamura, Noboru Nakano, Toshiyuki Nakano, Kazuma Nakazawa, Miyuki Oda, Kazuhiro Okamoto, Osamu Sato, Kai Shimizu, Amon Suganami, Yuki Sugi, Kou Sugimura, Satoru Takahashi, Ikuya Usuda, Saya Yamamoto, Jun Yamashita, Mayu Yamashita, Shoma Yoneno, Masahiro Yoshimoto

Friday 28 August

Instrumentation and Methods for Astrophysics

Lynx2030 Science Analysis Group: Final Report

Lynx2030 Science Analysis Group: Simon R. Bandler, Laura W. Brenneman, Nico Cappelluti et al. (+50 more)

The Lynx2030 Science Analysis Group (SAG) was convened to reassess the scientific goals and technical drivers of the Lynx mission concept amid a rapidly evolving astrophysics landscape. Building on the original Lynx Concept Study, the SAG examined how recent discoveries, emerging facilities, and advances in instrumentation influence the scientific opportunities for a next-generation flagship X-ray observatory. Through focused working groups, the SAG investigated the scientific impact of enhanced capabilities: (i) improved angular resolution, (ii) broader bandpass coverage, (iii) an enhanced microcalorimeter, (iv) new capabilities and observing modes, and (v) larger fields of view. Across a broad range of topics, from the formation of the first black holes and the evolution of galaxies to the baryon cycle, compact objects, stellar explosions, multi-messenger astrophysics, and the dynamic high-energy Universe, the SAG finds that the scientific motivation for a Lynx-class observatory remains compelling and, in many areas, has significantly strengthened over the past decade, prominently through JWST's discovery of the "Little Red Dots", likely massive accreting black holes in infant galaxies whose nature is fundamentally an X-ray question. This report shows that modest extensions beyond the original Lynx design reference mission can unlock transformative science while preserving the observatory's core architecture. Powerful current and future facilities such as Roman, Rubin, JWST, SKA, ngVLA, LISA, and NewAthena highlight the unique role a high-angular-resolution, high-throughput X-ray observatory would play in the multi-wavelength and multi-messenger ecosystem of the 2030s and beyond. The findings of the Lynx2030 SAG confirm Lynx's central vision: an unprecedented view of the hot and energetic Universe, enabling discoveries that will define high-energy astrophysics in the coming decades.
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All authors Lynx2030 Science Analysis Group: Simon R. Bandler, Laura W. Brenneman, Nico Cappelluti, Daniel Castro, Steven R. Ehlert, W. Peter Maksym, Fabio Pacucci, Scott W. Randall, Grant R. Tremblay, John ZuHone, Steven W. Allen, Antara R. Basu-Zych, Akos Bogdan, Joel N. Bregman, Tamta Burduli, Thomas Connor, Sanskriti Das, Casey DeRoo, Stephen DiKerby, Paul A. Draghis, Martin Elvis, Giuseppina Fabbiano, Ralf K. Heilmann, Jimmy A. Irwin, Amruta Jaodand, Margarita Karovska, Vinay L. Kashyap, Anthony A. Kerr, Caroline Kilbourne, Ralph Kraft, Jiangtao Li, Labani Mallick, Herman L. Marshall, Michael L. McCollough, Anna Ogorzałek, Frederik Paerels, Daniel Patnaude, Paul Plucinsky, David Pooley, Frederick S. Porter, Daniele Rogantini, Roger Romani, Helen R. Russell, Kazuhiro Sakai, Mark Schattenburg, Dan A. Schwartz, Malgorzata Sobolewska, Paolo Soffitta, Alexey Vikhlinin, Daniel R. Wilkins, Scott Wolk, Ka-Wah Wong, Irina Zhuravleva

Instrumentation and Methods for Astrophysics

Pre-shipment optical characterization of the SCALES instrument

Isabel J. Kain, Reni Kupke, Daren Dillon et al. (+31 more)

The Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy (SCALES) instrument is a 1-5 micron imager and 2-5 micron integral field spectrograph, currently being commissioned on the Keck II Telescope. SCALES is optimized for exoplanet high-contrast imaging and spectroscopic characterization, and will be sensitive to older, colder exoplanets than existing instrumentation. The 12.3" x 12.3" imaging channel is designed to replicate the capabilities of NIRC2, and the low (R~35-200, 2.2" x 2.2" FOV) and medium (R~2500-5000, 0.36" x 0.34" FOV) spectral resolution modes offer new capabilities compared to existing Keck instrumentation. We present preliminary optical performance results from laboratory testing and commissioning of SCALES.
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All authors Isabel J. Kain, Reni Kupke, Daren Dillon, R. Deno Stelter, Rosalie McGurk, Gwendolin Weber-Stover, Athira Unni, Marc Kassis, Scott Lilley, Peyton Benac, Mackenzie Lach, Arun Surya, Amirul Hasan, Ravinder Banyal, Raquel Martinez, Nicholas MacDonald, Will Deich, Aaron Hunter, Emily Plume, Michael Gonzales, Cristian Rodriguez, Arjun Kumar, Cyril Bourgenot, Paul Whiteg, Juergen Schmollg, James Wells, Spencer Davies, David Bramall, Dimitri Mawet, Olivier Absil, Michael Fitzgerald, Eric Wang, Steph Sallum, Andrew Skemer

Instrumentation and Methods for Astrophysics

96 kHz on-sky imaging on an adaptive optics system with a single-photon avalanche diode

Theodore A. Grosson, Maaike A. M. van Kooten, Kathryn Jackson et al. (+2 more)

Astronomical observations requiring extremely high angular resolution necessitate advanced adaptive optics (AO) systems to overcome blurring caused by the atmosphere. In addition to obtaining much sharper point-spread functions (PSFs) with these systems, it is beneficial to be able to characterize the behaviour of the resulting PSF across time and wavelength. We have installed a commercially-available Single-photon avalanche diode (SPAD) array on the focal plane of the REVOLT AO testbench at the Dominion Astrophysical Observatory, allowing us to observe the visible PSF of the system at rates up to 96 kHz. This provides a time-resolved view of the PSF at $\sim$100 times the frequency of the AO system itself. We use this detector to analyze the high-frequency behaviour of the PSF of the AO system, including residual tip/tilt and deformable mirror response. We also explore the performance of AO-assisted lucky imaging, in which we average together only the frames which result in the best image quality. We find that high-framerate imaging can significantly improve the PSF beyond the native capabilities of the AO system.
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All authors Theodore A. Grosson, Maaike A. M. van Kooten, Kathryn Jackson, Jean-Pierre Veran, Simon Carrier

Instrumentation and Methods for Astrophysics

Exploring the trade-space of distributed aperture telescopes for faint-object spectroscopy

Theodore A. Grosson, Deborah M. Lokhorst and Alan W. McConnachie

Scientific programs targeting the faintest objects push modern telescopes to increasingly large sizes, high costs and complex designs. Obtaining spectra of low surface brightness galaxies, for example, requires hours of observations on state-of-the art instruments. Increasing telescope diameters beyond 40 m raises potentially insurmountable challenges for design and funding. An innovative strategy for combating these costs is to use many small telescopes in place of a single large aperture. For observations in which high angular resolution is not necessary, this can be equivalent to a large diameter telescope in terms of sensitivity, while diffraction limited by the individual aperture. Improvements in commercial off-the-shelf (COTS) components have made this concept a possibility, as demonstrated by instruments such as the Dragonfly Telephoto Array, the Huntsman Telescope, and the Argus Array. In this work, we discuss the merits of "distributed aperture telescopes" as applied to the use case of spectroscopic observations of ultra-diffuse galaxies (UDGs). We compare the cost and simulated scientific performance of different configurations of apertures, detectors, and other components for this purpose, finding that an array of half-metre telescopes can obtain comparable observations to large telescopes for a fraction of the cost. Finally, we discuss the path to prototyping an array which will enable a spectroscopic survey of UDGs.
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Instrumentation and Methods for Astrophysics · Cross-listed from q-bio.OT

Geochemical Hazard Assessment of Martian Regolith for Future Human Exploration

Mavia Anjum and Gwendolyn D. Bart

As human missions to Mars move from concept to planning to reality, a systematic quantitative health risk assessment of martian regolith exposure has become critically important. This study presents a comprehensive multi-element, multi-pathway health hazard analysis of martian regolith for a 70 kg adult astronaut on an 18-month surface mission, using bulk silicate Mars geochemical data and Earth Upper Continental Crust reference values as baseline comparators. We computed Average Daily Dose, Hazard Quotient, Hazard Index, Enrichment Factor, Ecological Risk Factor, and Incremental Lifetime Cancer Risk across all three exposure pathways (oral ingestion, inhalation, and dermal contact) for toxic and heavy metals, under four filtration scenarios (0%, 25%, 50%, 95%). Results demonstrate that Cr and Co represent the most critical non-carcinogenic hazards, exceeding the regulatory threshold (HI > 1) even at 50% filtration, while Cr also poses the most significant carcinogenic risk, near the $10^{-4}$ regulatory threshold level. At least 92% regolith filtration efficiency is required to reduce Cr to acceptable non-cancer hazard levels. Nickel exceeds the acceptable cancer risk threshold of $10^{-6}$ at all filtration levels below 95%. No element other than Cr and Co exceeds HI = 1 in the unfiltered scenario, although Fe, Ni and Mn approach concerning levels. These results establish that a minimum 95% High-Efficiency Particulate Air (HEPA)-grade filtration efficiency combined with active chemical sorption is required for acceptable Cr and Co short term exposure and Cr, Ni long term exposure management. This study provides a pathway-specific quantitative risk framework applicable to habitat air quality standards and EVA suit specifications for Mars surface operations
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Instrumentation and Methods for Astrophysics

X-ray grating spectroscopy as a mission enhancement

Hans Moritz Guenther, Ehud Behar, Joel N. Bregman et al. (+27 more)

We propose to add instruments to any potential future X-ray mission with focussing optics that is considered in NASA's ASTRA framework. Such an instrument is a necessity to study AGN wind outflows and feedback, find the missing baryons, study the intergalactic medium, and analyze abundances and chemical bonds in dust grains throughout the Milky Way. We conclude that those science goals can be achieved with a spectral resolving power > 3000 in the soft X-ray band (about 10-40 Ang) and an effective area a few times larger than current instruments. We describe a possible mission implementation for a soft X-ray grating spectrometer that can be folded in and out or be mounted permanently in the beam. Such an instrument can reach the requirements for a wide variety of host mission properties. A small UV imager and a UV spectrograph can be mounted on the same platform with independent optics. These added instruments vastly enhance the science capabilities of the host mission for a modest cost (100-200 million $) and with weight and power needs that can be easily accommodated in any major mission.
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All authors Hans Moritz Guenther, Ehud Behar, Joel N. Bregman, Laura W. Brenneman, Alexander R. Bruccoleri, Lía Corrales, Elisa Costantini, Thomas Dauser, Casey T. DeRoo, Abraham D. Falcone, Adam R. Foster, Luigi Gallo, Catherine E. Grant, Sean J. Gunderson, Ralf K. Heilmann, David P. Huenemoerder, Maurice Leutenegger, Eric D. Miller, Michael Nowak, Frits Paerels, David A. Principe, Ioanna Psaradaki, Andrew Ptak, Agata Rozanska, Randall K. Smith, Pasquale Temi, Todd M. Tripp, Lynne Valencic, Joern Wilms, Scott J. Wolk

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

Impacts of Correlated Noise on Retrievals of Exo-Earth Atmospheres

Nicole Wolff, Bruce Macintosh, Tyler D. Robinson et al. (+6 more)

The Habitable Worlds Observatory (HWO) aims to accomplish high-contrast imaging and spectroscopy of true Earth analogs for the first time. However, high-contrast spectroscopy with HWO may be limited by residual speckles which persist after deformable mirror correction and post-processing, hindering atmospheric characterization. Previous studies of self-luminous giant planets showed that neglecting spectrally correlated errors due to speckles results in biased inferences of planetary parameters. Currently, HWO retrieval studies generate spectra without noise spectral correlations. We present a Gaussian Process model of correlated noise of known properties in simulated HWO exo-Earth spectra, and the integration of this noise source into the forward and inverse modeling tool rfast. We quantify the impact of correlated noise on inferred molecular abundances and planetary properties across the ultraviolet/visible/near-infrared bandpass, for varying spectral resolutions (R), signal-to-noise ratios (SNR), and noise correlation length-scales (L). We find that, at the fiducial UV/Vis/NIR R=7/140/70 and SNR=10, including spectrally correlated noise at L=200 nm and L=10 nm yields a 57% and 161% higher average uncertainty on log oxygen abundance, compared to uncorrelated noise. Consequently, it is critical for both instrument design and post-processing algorithms to minimize short length-scale chromaticity. Additionally, we find that a moderate resolution can constrain carbon dioxide (R$\geq 280$) and weakly detect methane (R$\geq2800$) abundances, demonstrating the benefit of a moderate resolution near-infrared spectrograph. These findings can aid the interpretation of future HWO reflectance spectra and set requirements on optical quality, instrument stability, and observing configurations.
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All authors Nicole Wolff, Bruce Macintosh, Tyler D. Robinson, Sarah Blunt, Jean-Baptiste Ruffio, Beck Dacus, Alex Madurowicz, Marshall Perrin, Laurent Pueyo

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

On the Impact of Correlated Noise and Spectral Resolution on the Retrieval Analysis of the Habitable World Observatory

Ji Wang, Philipp A. Huber and Sascha P. Quanz

Finding signs of life elsewhere in the universe is the holy grail of the field of exoplanets. Future space missions such as the Habitable World Observatory (HWO) are under development to search for biosignatures in exoplanets. We investigate the impact of correlated noise and spectral resolution on the retrieved biosignature chemical abundances. At the nominal spectral resolving power R=140 for HWO, we show that in 40% of the simulated runs the retrieved biosignature (H$_2$O and O$_2$) abundances are at least 1-$\sigma$ off the input ground truth. At R=1000, the 1-$\sigma$ inaccuracy rate drops to 10%. We provide an empirical relationship between the retrieved biosignature abundance uncertainty and the amplitude of the correlated noise. As part of the mitigation plan to reduce the impact of correlated noise on retrieval accuracy at low spectral resolution, we investigate the synergy between the HWO and LIFE space missions that cover ultraviolet, optical, and thermal-infrared wavelengths. After considering clouds and their effect on planet albedo, we find that the two missions are complementary in that (1) more biosignatures (H$_2$O, CO$_2$, O$_2$, and O$_3$) are detectable with a broader wavelength coverage; (2) retrieval uncertainty improves with the joint HWO+LIFE data set; and (3) LIFE is more sensitive to the atmospheric temperature profile, surface pressure, and planet radius. This work provides evidence to support the choice of a medium resolution at R=1000 instead of R=140 for HWO and a quantitative relationship between the retrieved abundance uncertainty and the level of correlated noise at different spectral resolutions.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE

Galactic Science with Ultra-High Angular Resolution X-ray Imaging

Paul A. Draghis, Jeremy Hare, Mayura Balakrishnan et al. (+8 more)

Milli- to micro-arcsecond X-ray imaging will open a new observational regime for Galactic astrophysics by resolving physical scales that are inaccessible to current X-ray observatories. This white paper highlights the science enabled by such capabilities across four broad questions: how particles are accelerated, how stars die, how accretion is fueled, and what populations of X-ray sources inhabit the Galaxy. Ultra-high angular resolution will enable many new studies, such as resolving shocks and jets, measuring proper motions, parallaxes, and binary orbits, and providing secure multiwavelength counterpart identifications in crowded environments such as the Galactic Center and globular clusters. Combined with high-time-resolution observations, these measurements will connect variability and transient events to the physical structures in which they originate, while coordination with gravitational-wave, neutrino, $\gamma$-ray, radio, optical, and infrared facilities will provide spatial information needed to identify and characterize multi-messenger sources. In addition to defining the science cases, this paper presents a curated list of compelling targets spanning various angular resolutions and outlines the complementary specifications necessary to maximize the scientific outcome. Accomplishing these science goals will require an instrument with high angular resolution, precise astrometry, substantial collecting area, sufficient spectral and timing resolution, and high dynamic range imaging capabilities.
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All authors Paul A. Draghis, Jeremy Hare, Mayura Balakrishnan, Poshak Gandhi, Tyler Holland-Ashford, Margarita Karovska, Thomas Maccarone, Herman L. Marshall, Mark Reynolds, Malgosia Sobolewska, Ryan Tanner

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

Spatially-Resolved Spectra of Diffuse Galactic Light using 10.8 M DESI Sky Fibers

Andrew K. Saydjari, Bruce T. Draine, Timothy D. Brandt et al. (+49 more)

Using 10.8 million “blank” sky spectra from the DESI Year 3 dataset, we measure the diffuse galactic light (DGL) spectrum in the optical at spectral resolution $R \sim 4000$ by correlating with far-infrared emission from IRAS. Subdividing the sky into 54 deg$^2$ pixels (HEALPix, NSIDE = 8), we map the variation of the DGL correlation spectrum and nebular emission lines across the DESI footprint in the high-Galactic-latitude sky. The increased data volume over previous SDSS-based analyses enables several new detections in the DGL, including scattering both onto and out of the line of sight from neutral interstellar sodium and potassium. We further detect direct emission from ro-vibrational transitions of molecular hydrogen in the near-infrared with an absolute radiance of $0.65\substack{+0.13 \\ -0.12}\times10^{-9}~{\rm erg\, cm^{-2}\,s^{-1}\,sr^{-1}}$, roughly consistent with theoretical expectations, but with an apparent ortho-to-para line ratio that is lower by a factor of $0.60\substack{+0.28 \\ -0.27}$. We confirm previous detections of extended red emission (ERE) in the DGL and map its spatial variation. Our spatially resolved DGL maps provide important observational constraints for the radiative transfer efforts that are now possible with recent 3D models of the Milky Way.
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All authors Andrew K. Saydjari, Bruce T. Draine, Timothy D. Brandt, Edward F. Schlafly, Arjun Dey, Douglas P. Finkbeiner, J. Aguilar, S. Ahlen, C. Allende Prieto, A. Anand, F. Beutler, D. Bianchi, D. Brooks, A. Carnero Rosell, T. Claybaugh, A. de la Macorra, P. Doel, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A Gontcho, G. Gutierrez, J. Guy, K. Honscheid, T. Karim, D. Kirkby, A. Kremin, O. Lahav, A. Lambert, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, E. Paillas, W. J. Percival, I. Pérez-Ràfols, F. Prada, C. Ravoux, G. Rossi, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, M. Schubnell, R. Sharples, J. Silber, M. Siudek, G. Tarlé, B. A. Weaver, R. Zhou

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

ExoMOD II. A Statistical Model of Transit Timing Variations in Kepler Multi-Planet Systems

David Nesvorny, Daniel A. Yahalomi, David Kipping et al. (+2 more)

In Paper I (Nesvorný et al. 2026), we forward modeled transit observations of the Kepler telescope to characterize the orbital properties of close-in planetary systems. The new population model, ExoMOD, was calibrated on Kepler's DR25 data. Here we use ExoMOD to statistically predict Transit Timing Variations (TTVs) from gravitationally interacting planets in the close-in systems, and compare these predictions with TTVs actually detected in the Kepler data. We find that planet-planet interactions are not expected to produce significant short-period TTVs, $P_{\rm TTV}/P_{\rm orb}<10$, where $P_{\rm TTV}$ and $P_{\rm orb}$ are the TTV and orbital periods, often enough to explain the short-period TTV signals inferred from the Kepler data. Most measured short-period signals must therefore have a different origin. The statistics of long-period TTVs – likely arising from the gravitational interaction between planets – indicates that single transiting planets have TTV-inducing companions nearly as often as doubles, thus ruling out multiplicity distributions with a prevalence of intrinsic singles. The fraction of planets with measured long-period TTVs increases to $\simeq 15$-18% for observed multiplicities $m \geq 3$, suggesting a change in the orbital architecture. High-multiplicity planetary systems have low gap complexities and probably retained a memory of their formation conditions. Ultimately, our work aims at developing a more informative feedback between observations and planet formation theories.
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All authors David Nesvorny, Daniel A. Yahalomi, David Kipping, Cristian Beauge, Sarah C. Millholland

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

ExoMOD I. A Forward Model for the Orbital Architecture of Kepler Multi-Planet Systems

David Nesvorny, Daniel A. Yahalomi, David Kipping et al. (+1 more)

Transit observations only detect planets with favorable, near edge-on orientation of orbits as seen by a distant observer, which leaves much freedom for various interpretations in terms of the underlying planetary system architecture. Here we forward model transit observations of the Kepler telescope to characterize the orbital properties of close-in planetary systems. We make sensible choices about the underlying distributions of planet radii, masses and orbital periods, parameterize the orbital excitation with the Angular Momentum Deficit (AMD), and adopt an accurate method to account for transit detection. The fits to Kepler's DR25 data are executed with MultiNest. We find that the orbital period distributions of Kepler singles and multis are statistically different from each other – possibly a consequence of Kepler's observational baseline. The observed gap complexity distribution is reproduced when planets in high multiplicity systems ($m \geq 5$) are assigned ideally correlated period ratios. The high-multiplicity systems probably retained a memory of their formation conditions. The gap complexity metric also helps to constrain the AMD distribution. We find that systems with positive radius monotonicities typically harbor smaller planets, as expected if the radius monotonicity is influenced by non-detections. A FGK dwarf in the Kepler field should host $\simeq 2.4 \pm 0.2$ planets on average with radii $0.5 < R_{\rm pl}/R_\oplus < 7$ and orbital periods $3<P_{\rm orb}<300$ d. For a detected planetary system, there is roughly a 50% chance that Kepler transit observations missed at least one inner or intermediate-period planet.
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All authors David Nesvorny, Daniel A. Yahalomi, David Kipping, Cristian Beauge

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

Exploring the sensitivity of in-ice radio detectors to cosmic ray mass composition

Nathaniel Alden, Marissa Boucher, Cosmin Deaconu et al. (+2 more)

In-ice radio detectors have been developed primarily for the detection of high-energy neutrinos via the Askaryan effect, but have recently been shown to also be sensitive to cosmic ray air showers impacting the ice sheet. Using CORSIKA 8 to simulate impacting air showers, we find that the lateral width of the in-ice cascade is sensitive to the atomic mass of the primary cosmic ray. The width of the shower core is accessible through the shape of the Askaryan radio spectrum, while the amplitude encodes the total in-ice charge excess. Using these two observables, we show that in-ice radio detectors can be used to measure cosmic ray mass composition in the region above $10^{17}$eV if the in-ice receivers are placed to adequately sample the Askaryan emission pattern. We also show that the in-ice core width is highly, but not exactly, correlated with the depth of maximum particle count ($\mathrm{X}_{\mathrm{max}}$), the most commonly used observable for reconstructing cosmic ray mass composition.
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All authors Nathaniel Alden, Marissa Boucher, Cosmin Deaconu, Abigail Vieregg, Philipp Windischhofer