Peer Revenue Publish or profit

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics Instrumentation and Methods for Astrophysics

astro-ph.IM Watch Instrumentation and Methods for Astrophysics

Monday 21 September

Instrumentation and Methods for Astrophysics

Emerging Technologies for Astrophysics Missions: Workshop Summary Report

Brendan P Crill, Nicholas Siegler, Dan Sirbu et al. (+3 more)

NASA's Astrophysics Division convened the Emerging Technologies for Astrophysics Missions (ETAM) Workshop in March 2025 at the Ames Research Center in Silicon Valley, California. The workshop's goal was to identify emerging technologies that could critically impact or enable future space missions-including concepts previously considered unachievable. Four key technology areas were examined: Astrophotonics, Artificial Intelligence and Machine Learning, Advanced Materials, and Quantum Sensors. Approximately 60 participants from academia, industry, government laboratories, and NASA centers attended. The workshop fostered an inspiring and collaborative atmosphere that encouraged interaction among experts both within and across disciplines. The workshop's three-day novel format featured landscape presentations outlining the state of each field, followed by breakout sessions where participants, grouped in their own disciplines, identified high-impact technologies for astrophysics missions. Cross-pollination sessions then brought together experts from multiple technology domains to foster interdisciplinary insights. The event successfully identified several high-priority emerging technologies (summarized in subsequent sections of this report). In addition to the field-specific insights, the workshop also produced five key cross-cutting suggestions for the NASA Astrophysics Division to consider.
Read the full abstract

All authors Brendan P Crill, Nicholas Siegler, Dan Sirbu, Luc Peterson, Sanaz Vahidinia, Ryan Watkins

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

Using Machine Learning to Model Stellar Collisions in our Galactic Center

Tristan C. Sand, Sanaea C. Rose, Elena González Prieto et al. (+9 more)

Direct collisions in the inner pc of the Galactic center can alter the orbits and properties of stars. The outcome of a collision depends on a number of parameters, including the masses and ages of the stars, the impact parameter, and the initial relative velocity. We utilize the newly developed $\verb|collAIder|$, a machine learning tool developed to predict the outcomes of stellar collisions, to bridge 3D hydrodynamic simulations of stellar collisions with a dynamical model of the Galactic center. Our results show a substantial population of stripped stars, $\sim$$10\%$ of the initial stellar population, produced by mass loss during high-speed collisions. Stellar mergers are less frequent, with about $5\%$ of the stars experiencing a collision-induced merger. We also find that high-speed, nearly head-on collisions can completely disrupt the stars. These destructive collisions are usually preceded by 10 or more collisions, which gradually reduce the mass of the star before it is ultimately destroyed. We estimate that mass loss during stellar collisions injects roughly $(2.5-8)\times 10^5$ M$_\odot$ of gas into the surrounding environment. Most of this gas is injected into the inner $0.1$ pc and about $90\%$ is retained within the cluster and may be accreted onto the supermassive black hole.
Read the full abstract

All authors Tristan C. Sand, Sanaea C. Rose, Elena González Prieto, James C. Lombardi, Jr., Charles F. A. Gibson, Fulya K{\i}roğlu, Kyle Kremer, Christopher E. O'Connor, Enrico Ramirez-Ruiz, Frederic A. Rasio, Tjitske Starkenburg

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

Probing Exoplanetary Rings with Asterodensity Profiling: A PhotoRing Analysis of Kepler-51

Jorge I. Zuluaga, Sebastian Numpaque, David M. Kipping et al. (+1 more)

The Kepler-51 system hosts transiting super-puff planets whose extremely low bulk densities challenge structural models, possibly because unresolved rings inflate their inferred radii. We test this hypothesis by combining asterodensity profiling with TTV-aware transit fits of Kepler long-cadence photometry. For Kepler-51b we measure a density ratio $\Psi\equiv\rho_{\star,\mathrm{obs}}/\rho_{\star,\mathrm{true}} = 1.18\pm0.06$, a $2.9\sigma$ offset from $\Psi=1$; for Kepler-51d we find $\Psi=1.04\pm0.08$ ($0.6\sigma$), consistent with no anomaly. Unmodelled eccentricity is disfavoured for planet b by TTV-derived dynamical constraints ($p=0.007$) but remains viable for planet d ($p=0.33$). The offset of Kepler-51b is also compatible with the PhotoRing (PR) effect of unmodeled rings. Using a geometric ringed-transit forward model and Bayesian retrieval, we identify ring configurations that reproduce the transit observables and the measured density ratios. The preferred solutions are consistent with compact, moderately inclined rings that raise the true bulk densities by factors of $2-5$. Conversely, the absence of a large PR offset excludes extended, optically thick, high-obliquity rings at $99\%$ credibility for b and $70\%$ for d from archival photometry alone. These objects may thus be "puff ringed planets" although recent JWST observations of Kepler-51d show no direct signature of an opaque ring. While the required impact parameters and stellar densities show tension with independent constraints -attributable to Kepler's 30-minute cadence- this study presents the first complete application of the PR effect, offered as a methodological demonstration and exclusion experiment rather than as evidence that rings are present. All code is publicly available to support applications to other systems.
Read the full abstract

All authors Jorge I. Zuluaga, Sebastian Numpaque, David M. Kipping, Jaime A. Alvarado-Montes

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

Merlin: Fast and flexible 3x2pt cosmology with simulation-based inference

Alexandra Wernersson, Guillermo Franco-Abellán and Guadalupe Cañas-Herrera

We present Merlin, a simulation-based inference (SBI) pipeline to perform cosmological analyses of 3x2pt summary statistics: cosmic shear, galaxy clustering and the cross-correlation power spectra. Our approach combines Marginal Neural Ratio Estimation (MNRE) with 3x2pt angular power spectra predictions from the cloelib library, although the pipeline is readily extensible to other cosmology libraries. We demonstrate this pipeline on a realistic setting representative of a Stage-IV photometric survey, with a 50-dimensional parameter space describing cosmology and a wide range of systematic effects. We find posteriors that are in excellent agreement with the nested sampler Nautilus, while reducing the number of required CPU-hours by two orders of magnitude. Because the generation of training data and the training of inference networks are decoupled processes, a single simulation bank can be reused to perform inference under different analysis choices, further improving the simulator-efficiency. We illustrate this flexibility by applying scale cuts, varying the survey area, and removing cosmic shear from the data vector (2x2pt), all at zero extra model evaluations, whereas sampling-based methods need costly re-runs for each case. The Merlin code is publicly available on GitHub.
Read the full abstract

Instrumentation and Methods for Astrophysics

The Sun can flip the shielding effect of added spacecraft mass

Yasser Maghrbi and Nelson Christensen

Spacecraft structure is usually treated as shielding against energetic particles. We find that the Sun can reverse the effect of adding that structure. Free-falling test masses are the inertial references of gravitational-wave observatories and equivalence-principle experiments; charge accumulated on them couples to stray electric fields and produces acceleration noise that limits sensitivity. In a LISA-like system, increasing the surrounding aluminium from 16 to 24 g cm -2 reduces the stopping-proton population by (2.3 $\pm$ 0.5)% at solar minimum but increases it by (17.0 $\pm$ 1.0)% at solar maximum, the crossover lying in the deep-solar-minimum regime. Complete 2-24 g cm -2 mass curves show a broad maximum at solar minimum but a monotonic rise at maximum. The reversal arises because added material both attenuates incident protons and feeds a nuclear-processed population into the stopping-energy window. A first-order projection onto published charging rates gives changes of about -2% and +11% in the net charging rate, affecting charge accumulation, discharge requirements and the associated noise budget. The sign of a structural trade is therefore not fixed by the structure alone.
Read the full abstract

Instrumentation and Methods for Astrophysics

First Experimental Evaluation of Stray Light Noise Modeling of kilometers-long Beam Tube Arms of Gravitational Wave Detectors

Emilia Chick, Timothy O'Hanlon, Hiro Yamamoto et al. (+3 more)

We present the results of the first experimental evaluation of stray light noise models for LIGO beam tube baffles. We combine the results of a testing campaign at LIGO Livingston and SIS simulations to get a model of backscatter and diffraction noise of select mid-arm baffles. Agreement to within a factor of $3-10$ is found between models and measured gravitational waHe strain. Two distinct regions of well-propagating motion were identified, at approximately $35Hz$ and $90Hz$, and these are visible in the strain signal as broadband features. Peaks with $Q \approx 100-1000$ were also found in the strain signal between $70Hz$ and$100Hz$. These are theorized to come from diffraction noise only, and are modeled using Q-factors measured from the strain. These models are also in good agreement with the strain signal. Other findings on the effect of auxiliary arm systems on stray light noise are discussed.
Read the full abstract

All authors Emilia Chick, Timothy O'Hanlon, Hiro Yamamoto, Denis Martynov. Valery Frolov, Anamaria Effler, Antonios Kontos

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

Real-Time Doppler-Frequency Measurement and Frequency-Pulling Suppression in Arm-locking

Zheng-Rong Xiang, Jun Ke, Tian-Chi Zhu et al. (+3 more)

Arm-locking is an important technique for suppressing laser frequency noise in space-based gravitational-wave detection. However, stronger noise suppression inevitably increases the magnitude of frequency pulling, thereby prolonging the lock-acquisition time and increasing the risk of system instability. To address this issue, this paper proposes a real-time Doppler-frequency measurement and frequency-pulling suppression method based on a linear-quadratic-gaussian controller. To achieve a balance between noise suppression and pulling suppression, a time-varying control strategy is adopted. At the initial stage of the time-varying control process, the primary objective is to rapidly limit frequency pulling. Subsequently, the level of pulling suppression is gradually relaxed while the capability for laser frequency-noise suppression is progressively enhanced, so that the residual frequency noise satisfies the time-delay interferometry (TDI) requirement by the end of the transition. Comprehensive performance simulations are conducted for several arm-locking configurations. The results show that the proposed suppressor can reduce frequency pulling within approximately 1000 s while limiting its magnitude to below 100 MHz, thereby eliminating the need for the conventional Doppler frequency pre-estimation stage. When a Fabry-Perot laser is used, the amplitude spectral density (ASD) of the closed-loop laser frequency noise meets the requirements of second-generation and first-generation TDI after 2000 s and 9200 s of closed-loop operation, respectively. These results demonstrate that the proposed suppressor provides both rapid frequency-pulling suppression and a high level of laser frequency-noise suppression. This new method provide a feasible way for rapid acquisition and locking of arm-locking.
Read the full abstract

All authors Zheng-Rong Xiang, Jun Ke, Tian-Chi Zhu, Hao-Xin Xu, Cheng-Gang Shao, Jie Luo

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

Transit timing variation

Luca Borsato

The transit timing variation (TTV) method is a key approach to the confirmation, detection, and characterisation of exoplanetary systems. This review discusses the detection of TTVs from transit observations and the origins of TTVs, mainly due to gravitational interactions with perturbing planets, whether transiting or not. Additionally, this work details methodologies for deriving planetary parameters, employing quasi-global and local optimisation algorithms within a Bayesian framework. By analysing TTVs, planetary orbital parameters and dynamical properties can be inferred, providing valuable insights into system formation and evolution. The role of resonances and stability in shaping these systems is reviewed, along with sensitivity biases that influence mass determination. Comparative analyses highlight the unique demographic contributions of TTV systems. TTVs offer a window into the dynamical and physical properties of planetary systems, advancing our understanding of their diversity and stability.
Read the full abstract

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

LATED: Ly$\alpha$-anchored photometric selection of candidate metal-free and extremely metal-poor star formation from the end of reionisation to cosmic noon

Mingyu Li, Zheng Cai, Roberto Maiolino et al. (+24 more)

Cosmological simulations allow a low-level tail of Population III (Pop III) star formation to persist to $z=2-6$. Spectroscopic confirmation is expensive, so an efficient photometric pre-selection is needed. We present LATED (Lyman-Alpha Tomography of Extremely Metal-poor Domains), which selects metal-free and extremely metal-poor candidates from a Ly$\alpha$-emitter parent sample using strong-line diagnostics. The method requires three bands and two colours, $x=m_{\rm OIII}-m_{{\rm H}\alpha}$ and $y=m_{{\rm H}\alpha}-m_{\rm cont}$, which trace oxygen abundance and the H$\alpha$ equivalent width, respectively. Requiring that the filters simultaneously contain [O III]+H$\beta$ and H$\alpha$, together with a Ly$\alpha$ parent selection, defines five windows spanning $z=1.92-6.60$ (four JWST/NIRCam, one Roman/WFI). The criteria, $x\geq x_{\rm min}(z)$ and $y\leq y_{\rm max}(z)$, are set by the per-redshift extrema of a forward-modelled Pop III template locus. Ordinary metal-enriched star-forming and AGN templates fall outside the selection region, and possible contaminants such as little red dots are flagged by their multi-band colours. To check contamination empirically, we apply LATED to 1126 JADES spectroscopic galaxies, and no source is selected in the four NIRCam windows. We release a Python package which converts the same photometry into R3=[O III]/H$\beta$ as a measurement or upper limit, reproducing JADES spectroscopy with small 0.12 dex scatter. Applied to 85 archival MUSE Ly$\alpha$ emitters in Abell 2744, LATED recovers the confirmed extremely metal-poor galaxy AMORE6 and reveals three new candidates at $z=3-5$. Photometry alone cannot establish a metal-free nature. LATED delivers prioritised candidates for spectroscopic follow-up, providing a scalable route toward a systematic census of late-time Pop III star formation.
Read the full abstract

All authors Mingyu Li, Zheng Cai, Roberto Maiolino, Fuyan Bian, Sijia Cai, Francesco D'Eugenio, Qiao Duan, Eiichi Egami, Xiaohui Fan, Yuki Isobe, Xihan Ji, Gareth C. Jones, Maria Koller, Xiaojing Lin, Boyuan Liu, Christopher C. Lovell, Kimihiko Nakajima, Masami Ouchi, Robert G. Pascalau, Zijin Su, Jan Scholtz, Fengwu Sun, Sandro Tacchella, Hannah Übler, Yunjing Wu, Fujiang Yu, Zijian Zhang

Instrumentation and Methods for Astrophysics

Pushing high angular resolution and high contrast observations on the VLTI from Y to L band with the Asgard instrumental suite: integration status and plans

Marc-Antoine Martinod, Michael J. Ireland, Denis Defrère et al. (+39 more)

ESO's VLTI has a history of record-breaking discoveries in astrophysics using high-angular resolution instrumentation. Its latest visitor instrument, the Asgard instrumental suite, is one key to further enhance the potential of the facility, particularly in the very near-infrared. It comprises four natively collaborating instruments: HEIMDALLR, a K-band fringe tracker, wavefront corrector and stellar interferometer in K band, with the same optics; Baldr, an H-band Zernike wavefront sensor; BIFROST, an Y-J-H-band photonic combiner whose main science case is studying the formation processes and properties of stellar and planetary systems; and NOTT, an L-band nulling interferometer for imaging young planetary systems. Each of these instruments promise significant advances in their respective science goals that scale with their technical challenges and technology innovations. The integration of Asgard is planned in three phases. The first one (integration, commissioning of HEIMDALLR and Baldr) is successfully done. In this paper, we show an overview of the current progress of the integration of Asgard, the first results of the on-sky commissioning of HEIMDALLR and the future steps and observing policies for Asgard to serve the broader community.
Read the full abstract

All authors Marc-Antoine Martinod, Michael J. Ireland, Denis Defrère, Stefan Kraus, Frantz Martinache, Peter G. Tuthill, Emilie Bouzerand, Julia Bryant, Sorabh Chhabra, Peter Chingaipe, Benjamin Courtney-Barrer, Fred Crous, Nick Cvetojevic, Daniel S. Dahl, Colin Dandumont, Steve Ertel, Germain Garreau, Adrian M. Glauser, Xavier Haubois, Lucas Labadie, Stéphane Lagarde, Daniel Lancaster, Romain Laugier, Roxanne Ligi, Nathan Long, Alexandra Mazzoli, Thomas Mattheussen, György Medgyesi, Kwinten Missiaen, Sébastien Morel, Daniel J. Ahrer, Barnaby Norris, Jyotirmay Paul, Romain Petrov, Gert Raskin, Sylvie Robbe-Dubois, Gordon Robertson, Muhammad Salman, Ahmed Sanny, Nicolas Schuhler, Owain Snaith, Adam K. Taras

Instrumentation and Methods for Astrophysics

Silencing the stellar glare with kernel-nulling and active phase control on photonic chips

Marc-Antoine Martinod, Vincent Foriel, Nick Cvetojevic et al. (+4 more)

Characterizing exoplanets and finding biosignatures are among the hottest topics in astronomy. This quest is challenged by the brightness contrast between the faint planet and the overwhelming glare of the host star, their small angular separation, and observing conditions degraded by optical aberrations. Nulling interferometry is a promising technique to achieve this goal by fulfilling requirements for both high contrast and high angular resolution. Photonic Integrated Circuits (PICs) provide compactness, design versatility, and scalability needed for nulling. With the PHOTONICS project, we aim to create novel coherent combination architectures, based on a multimode interferometer (MMI) coupler and on-chip active phase control with no moving parts. We present the first lab tests of a four-beam kernel-nuller made out of a single MMI coupler with active phase control: ABCD fringe-tracking and the characterization of the contrast detection limits of a four-beam kernel-nuller.
Read the full abstract

All authors Marc-Antoine Martinod, Vincent Foriel, Nick Cvetojevic, Frantz Martinache, Jeronimo Calderon-Gomez, Roxanne Ligi, David Mary

Instrumentation and Methods for Astrophysics

Premature re-entry of the FACSAT-2 nanosatellite: orbital decay and attribution to the maximum of solar cycle 25

Santiago Vargas Dominguez, Mara Valentina Angel and Brayan Nicolas Buitrago

FACSAT-2 Chiribiquete, the second satellite of the Colombian Aerospace Force and the first South American nanosatellite mission dedicated to greenhouse gases, re-entered on 27 October 2025, 926 days after its deployment into a Sun-synchronous orbit, against a declared service life of at least five years and an estimated orbital lifetime of fifteen. The orbital evolution was built from the epochs of the TLEs (two-line elements) of NORAD ID 56205. We reconstruct its decay using its 3696 orbital elements, the solar and geomagnetic indices from the OMNI2 database, and NRLMSISE-00 densities sampled along the orbit. Inverting the drag yields a ballistic coefficient of 72.3 kg/m2 (6% statistical, 20% systematic), equivalent to an effective area of 0.047 m2, consistent with the declared geometry. With it, the model reproduces the trajectory with a root-mean-square error of 7.4 km and, calibrated on 2023-2024 alone, the re-entry with a 28-day out-of-sample error. F10.7 averaged 170.8 sfu over the mission, against the 139 sfu of the environmental scenario derived from the official 2019 forecast, which lengthens the orbital lifetime by x1.52; two co-launched CubeSats give x1.50 and x1.57, a consistency check across objects rather than independent evidence. Imposing quiet geomagnetic conditions returns 102 days, 22% of the shortening, with strong sensitivity to the adopted threshold; a superposed-epoch analysis over 149 storms gives a median drag enhancement of x1.92 for the intense events. We discuss the consequences for the design of FACSAT-3 and for the public communication of a mission's expected lifetime.
Read the full abstract

Instrumentation and Methods for Astrophysics

Natural coordinates for constrained correlation functions: Partial autocorrelations and the geometry of positive power spectra

Thomas Erben

Two-point correlation functions are a standard summary statistic in cosmic shear and large-scale-structure analyses. Their values are, however, constrained: non-negativity of the underlying power spectrum restricts any admissible sequence of correlation coefficients $(r_1,\ldots,r_N)$ to a bounded convex region, described in the one-dimensional case by the recursive interval geometry of Schneider & Hartlap (2009). Their formalism introduces an affine variable $x_n$ that maps the admissible interval for $r_n$, given $r_1,\ldots,r_{n-1}$, to $[-1,+1]$. We identify $x_n$ with the partial autocorrelation coefficient $\alpha_n$ of the associated positive Toeplitz correlation matrix, a classical quantity in time-series analysis. The partial autocorrelations thus provide natural coordinates on the admissible region, each $\alpha_n$ varying independently in $[-1,+1]$. This identification makes the standard partial-autocorrelation toolbox directly applicable. The admissible intervals for $r_n$, cumbersome to obtain at higher order in the original determinant-based formalism, now follow from an $\mathcal{O}(N^2)$ recursion at arbitrary order. The inverse hyperbolic tangent used in the quasi-Gaussian likelihood construction of Wilking & Schneider (2013) becomes Fisher's $z$-transformation of partial autocorrelations, providing a classical statistical interpretation of its empirical Gaussianising effect. Numerical experiments illustrate the practical use of these natural coordinates in the tested one-dimensional settings. Higher-dimensional isotropic constraints require additional geometric input and lie outside the direct scope of this identification.
Read the full abstract

Instrumentation and Methods for Astrophysics

Development of a Photonically Generated Frequency Reference for Space VLBI

Hannah Tomio, Kohei Yamamoto, Charlotte Zehnder et al. (+5 more)

Space-based Very Long Baseline Interferometry (VLBI) can improve both the angular and temporal resolution of images over terrestrial VLBI techniques. Future space VLBI (sVLBI) missions are targeting higher observation frequencies than modern, terrestrial VLBI, and therefore these missions will require higher stability frequency references than standard hydrogen masers. While existing frequency references for space-based applications have concentrated on long-term stability, in this effort, we present a frequency reference with high short-term stability intended for sVLBI missions. This reference leverages developments in cavity-stabilized lasers from the Laser Interferometer Space Antenna (LISA) mission and commercial efforts towards a robust, space-qualifiable optical frequency comb. We describe the implementation and experimental results of this system with a path to spaceflight, which demonstrates an Allan deviation of $3.26 \times 10^{-14}$ at 1 second, $6.00 \times 10^{-15}$ at 10 seconds, and $6.73 \times 10^{-15}$ at 30 seconds for the 100 MHz frequency reference signal, and show that this performance meets the needs of future sVLBI missions.
Read the full abstract

All authors Hannah Tomio, Kohei Yamamoto, Charlotte Zehnder, Guangning Yang, Kenji Numata, Andrew Attar, Henry Timmers, Holly Leopardi

Instrumentation and Methods for Astrophysics

IceCube Upgrade status and perspectives

Anna Eimer

The IceCube Neutrino Observatory instruments one cubic kilometer of deep-glacial ice between 1450 m and 2450 m below the surface at the geographic South Pole to detect neutrinos via Cherenkov radiation of relativistic charged particles produced in their interactions. This detector is responsible for a number of key observations in neutrino astrophysics, which include the discovery of a high-energy astrophysical neutrino flux and, more recently, the galactic plane. During the austral summer of 2025/26, five new strings equipped with new photosensor designs were deployed as a dense infill in the middle of the existing detector. The science goals of this detector are twofold: Firstly, given the higher photocathode density, an improved atmospheric neutrino event selection and reconstruction at a few GeV can be achieved for enhanced capabilities to study neutrino oscillations. Secondly, novel calibration devices will improve the knowledge of the optical properties of the glacial ice and the detector response. These new calibration results will be applied to archival IceCube data, improving angular and spatial resolution of all detected astrophysical neutrino events. The IceCube Upgrade also serves as a first step towards the next-generation neutrino telescope at the South Pole, called IceCube-Gen2.
Read the full abstract

Instrumentation and Methods for Astrophysics

Fast and accurate astronomical source deblending with Density-Peak Clustering

M. D. Lepinzan, F. Tomba, E. Romelli et al. (+2 more)

Source deblending is a fundamental challenge for current and forthcoming astronomical surveys, where increasing source density and image depth lead to a growing number of overlapping detections. Accurate deblending is essential for reliable measurements of source morphology and photometry, as well as for cosmological analyses. We present a redesign of the Advanced Density Peak (ADP) clustering algorithm, tailored to the identification and separation of blended astronomical sources within detection regions. We develop a validation framework combining realistic image simulations, automatically generated ground-truth segmentation, and label-invariant metrics. ADP is assessed against ASTErIsM, an established density-based astronomical deblender, using pairwise simulations, synthetic multi-source images, and Euclid Q1 public data. In pairwise simulations, the methods show comparable performance across a broad range of source separations and flux ratios, with photometric differences typically below 1% and reaching 5-7% in the most challenging cases, without systematic bias. In multi-source simulations, ADP recovers approximately 8% more ground-truth sources, while the positions of sources identified by both methods agree at the sub-pixel level. On Euclid Q1 public data, the methods show strong agreement in segmentation area, ellipticity, position angle, and photometry, with the largest differences for the smallest and faintest sources. ADP also provides a substantial computational advantage: end-to-end benchmarks on 19200 x 19200 pixel Euclid images require approximately 16-200 s, corresponding to speedups of 12-156x relative to ASTErIsM, with median and mean improvements of 36x and 54x, respectively. These results show that ADP provides scientifically competitive deblending at substantially lower computational cost, making it a promising approach for large-scale astronomical imaging surveys.
Read the full abstract

All authors M. D. Lepinzan, F. Tomba, E. Romelli, A. Rodriguez, L. Tornatore

Instrumentation and Methods for Astrophysics

Scale-Vector Alignment: A Scale-Aware Framework for Spatially Resolved Morphological Similarity in Astronomical Images

Mengke Zhao, Guang-Xing Li, Keping Qiu et al. (+1 more)

Astronomical maps made with different tracers are not expected to have identical morphology. Excitation, optical depth, chemistry, radiation, and ISM phase alter the response of a tracer, and the resulting differences can depend on both position and spatial scale. We propose scale-vector alignment, a scale-aware method based on Constrained Diffusion Decomposition (CDD). CDD decomposes an image into localized scale components; at each position, their amplitudes define a scale vector that describes how the measured intensity is distributed over spatial scale. We define the pixel-wise similarity $\Spix(x,y)$ as the normalized alignment of two local scale vectors. The normalization removes the overall amplitude, so $\Spix$ compares relative scale composition rather than absolute flux. We also define the scale-wise similarity $\Sscale(l)$ by comparing the two CDD component maps at each spatial scale. Spatial shifts are used to construct an empirical shifted reference distribution for $\Spix$. In Orion~A, the tracer with the highest similarity to the dust-derived column-density map changes from $^{12}$CO to $^{13}$CO to C$^{18}$O toward higher column density. In NGC~6334I(N), the line–continuum similarity decreases locally around the brightest compact structures, where radiative-transfer effects can alter the observed line morphology. In NGC~3627, CO is most similar to 21~$\mu$m emission, and $\Sscale$ reaches its maximum at an intermediate sub-kpc scale. The method measures where two tracers have similar multiscale structure and at which scales their spatial distributions agree. The implementation is publicly available at https://github.com/meng-ke/Scale-Vector-Alignment.
Read the full abstract

All authors Mengke Zhao, Guang-Xing Li, Keping Qiu, Shanghuo Li

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

Sound-Horizon-Independent Test of Cosmic Distance Duality Relation Using Artificial Neural Networks and Gaussian Processes

Bo-Hao Jiang, Guo-Jian Wang and Tao Yang

The cosmic distance duality relation (CDDR), $D_L(z)(1+z)^{-2}/D_A(z) \equiv 1$, is a fundamental relation in modern cosmology linking luminosity distance $D_L$ and angular diameter distance $D_A$. We define $\eta(z) \equiv D_L(z)(1+z)^{-2}/D_A(z)$ and reconstruct the relevant quantities over $0 < z < 2.5$ using two independent non-parametric methods: Gaussian processes (GP) and artificial neural networks (ANN). Specifically, we reconstruct $D_L$ from three different Type Ia supernovae (SNe$~$Ia) compilations (PantheonPlus, Union3, and DES-Dovekie), the baryon acoustic oscillation distance ratio $D_M/D_H$ from SDSS and DESI, and the Hubble function $H(z)$ from cosmic chronometer (CC) data. Our CDDR test is independent of both the cosmological model and the sound horizon $r_d$ calibration, as $D_M/D_H$ naturally eliminates $r_d$. We render our GP reconstructions insensitive to mean-function and kernel choices via full Bayesian marginalization over hyperparameters, with ANN as a cross-check$-$revealing the impact of data sparsity on the latter. Our results show no significant deviation from the CDDR exceeding $2\sigma$, and for the CC+BAO+DES-Dovekie combination it remains within $1\sigma$ over most of the redshift range. With $r_d$ eliminated, varying the only remaining external parameter $M_B$ systematically shifts $\eta(z)$ through the $M_B$-$H_0$ degeneracy, indicating that the observed $\eta\neq1$ signal is closely tied to $H_0$ tension among datasets and is likely driven by $M_B$ systematics rather than a true CDDR violation. Future high-quality CC, BAO, and SNe$~$Ia data$-$with either improved $M_B$ calibration or $M_B$-free distance measurements$-$will be essential for extending this calibration-free approach.
Read the full abstract

Sunday 20 September

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

XMST II: The spatial and kinematic structure of Galactic OB associations in Gaia DR3

Mark Gallaway

Stellar associations are difficult clustering targets because position, kinematics and extinction carry different physical units, different uncertainties and different discriminatory power. We extend the Extended Minimum Spanning Tree (XMST) framework without forcing these observables into a single metric. Three-dimensional spatial connectivity first defines candidate parent structures (XMST-S1), transverse kinematics then tests those parents for dynamically distinct populations (XMST-S3), and visual extinction provides a final reddening refinement (XMST-S2). Across 1000 Monte Carlo realisations, XMST-S1 produced a better purity–completeness balance than the eight predefined three-dimensional HDBSCAN configurations tested, although neither method reliably separated a deliberately superimposed pair using spatial information alone. Applying kinematics before reddening increased mean Jaccard similarity to 0.8354 and resolved the overlapping pair in 98.6 per cent of realisations. The S3 null experiment produced only five accepted subdivisions among 106,265 tested groups. Across 1000 paired reddening-uncertainty realisations, increasing uncertainty reduced the mean number of accepted S2 subdivisions from 4.224 to 1.982, while mean Jaccard similarity changed only from 0.8074 to 0.7993. Direct XMST-S3 uncertainty tests showed negligible practical degradation for transverse-velocity errors up to $0.5~\mathrm{km\,s^{-1}}$ per component, with larger errors progressively suppressing kinematic refinement. In a label-blind repartition of 2,551 stars from 56 published OB associations, median best-match Jaccard similarity increased from 0.6535 after spatial clustering to 0.8861 after complete refinement, with 22 associations recovered identically. The main result is that physically different observables can refine an existing spatial hierarchy without redefining its me
Read the full abstract

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

Designing 3D transfers: application to Earth-Moon

Allan Kardec de Almeida Junior, Timothée Vaillant, João P.F. Agostinho et al. (+2 more)

Three dimensional Earth-Moon transfers usually consume more fuel than planar ones, but are needed depending on the latitude of the launch site and the desired inclination of the final lunar orbit. A systematic search of the optimal 3D transfers represents a true challenge due the dimension of the parameter set to span. In this paper, we propose a new method to design 3D transfers using a tangential velocity constraint for the burns, modeled using the overdetermined constraints technique based on the Theory of Functional Connections for an optimal search of solutions in a numerically efficient way. The developed method is applied here for a systematic study of optimal 3D Earth-Moon transfers, but could be used to design any type of 3D maneuvers.
Read the full abstract

All authors Allan Kardec de Almeida Junior, Timothée Vaillant, João P.F. Agostinho, Antonio F.B.A. Prado, Leonardo B. T. Santos

Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

Optimal all-angle reconstruction of the Hellings-Downs curve

Jing-Hong Han and Zhi-Chao Zhao

Pulsar timing arrays (PTAs) detect nanohertz gravitational waves through spatial correlations between the timing residuals of different pulsars. For an isotropic, unpolarized stochastic background in general relativity, the ensemble-mean correlation follows the Hellings–Downs (HD) curve; measuring this angular pattern tests the gravitational-wave origin of the signal. Standard bin-by-bin reconstructions optimize the weights within each angular bin separately. We reconstruct the curve jointly using the full pulsar-pair covariance, retaining a free amplitude in every bin. The resulting all-angle best linear unbiased estimator minimizes the variance of every bin value and every linear combination of bins. Applied to the public NANOGrav 15 yr data products, our method reduces the bin standard deviations by up to 12.9%, with a median reduction of 9.5%. For a future Square Kilometre Array Observatory (SKAO)-like PTA, the predicted reduction reaches 36.4%, with a median of 29.6%, enabling significantly more precise measurements of the gravitational-wave background.
Read the full abstract

Saturday 19 September

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

Marginalized planet-to-star radius ratio posteriors for low-SNR transiting planets via dimensionality reduction

Oryna Ivashtenko and Barak Zackay

Occurrence rate estimates of small long-period planets rely on the radii of low signal-to-noise ratio transit candidates whose posteriors should be propagated into the population inference. These posteriors should include the error budget from all latent parameters and account for the effects of the correlated noise. Full Markov chain Monte Carlo fits with Gaussian processes take days of runtime per target, and provide information on latent parameters that will be marginalized over anyway. We present a method that computes the marginalized posterior of the planet-to-star radius ratio while sampling only a lower-dimensional effective parameter space. The 11-dimensional problem reduces to a 4-dimensional one, while the posterior retains the uncertainty budget of all the nuisance parameters, including eccentric orbits, stellar parameters, and limb darkening. The method operates on whitened light curves, mitigating biases due to correlated noise. We show that the posteriors are calibrated on simulated systems: the true radii have uniformly distributed p-values. Applied to 419 faint long-period Kepler Objects of Interest, the method yields radius ratios broadly consistent with the KOI table, although their differences exceed those expected from the reported uncertainties.
Read the full abstract

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

Surveying the Universe in 4D: Beating Cosmic Variance with Wide-Field Slitless Spectroscopy from HST, JWST, Euclid, Roman, and Beyond

Andreea Petric, Gaël Noirot, Stacey Alberts et al. (+71 more)

We summarize strategies, lessons learned, and future directions from the Space Telescope Science Institute workshop Surveying the Universe in 4D: Beating Cosmic Variance with Wide-Field Slitless Spectroscopy from HST, JWST, Euclid, Roman, and Beyond, held August 24–28, 2026. The workshop examined scientific results, observational and data analysis challenges, extraction tools, and future opportunities. Discussions highlighted (1) the transformative potential of WFSS for the study of transient phenomena, galaxy evolution –both spatially-resolved and within the broader context of the cosmic web–, and rare populations and (2) the synergies among Euclid and Roman surveys, Rubin-LSST monitoring, JWST WFSS, and high-resolution integral-field observations. Participants identified advances in forward modeling and physics-informed machine learning as essential for addressing spectral overlap, crowded fields, and upcoming, very large data volumes. Realizing WFSS's full potential will require community-wide infrastructure, science-ready data products, accessible cloud-based analysis tools, and robust benchmarking of reduction pipelines. Crucially, participants called for systemic changes to properly recognize early-career researchers who invest significant efforts in pipeline, code, and calibration developments that enable WFSS science, and stressed that progress requires collaborative, multidisciplinary practices that optimize the participation and benefits of the next generation.
Read the full abstract

All authors Andreea Petric, Gaël Noirot, Stacey Alberts, Russell Ryan, Louis-Gregory Strolger, Vicente Estrada-Carpenter, Mainak Singha, Adrian E. Bayer, Olivier Gilbert, Farhanul Hasan, Mason Huberty, Bingcheng Jin, Xiangyu Jin, Anika Kumar, Kasra Mokhtarpour, Preethi Nair, Eleni Tsiakaliari, Vivian U, Brittany N. Vanderhoof, Arshia Akhtarkavan, Natalia Alvarez-Ibanez, Roman Fernandez Aranda, Tri L. Astraatmadja, Clive Binu, Claire Bolda, Westley Brown, Guillermo Romero Cruz, Mohamed H. Abdullah, Jeremy Favaro, Mason Footh, Helen Fraser, Yuming Fu, Annie Giman, Nicolas Gomez, Massimo Griggio, Peter Gwartney, Aryana Haghjoo, Fabian Hervas-Peters, Jiamu Huang, Sandra Jaison, Jeyhan S. Kartaltepe, Sarah Kendrew, Ivan Kramarenko, Sahana Kumar, Zhaoran Liu, Arianna S. Long, Sangeeta Malhotra, Faezeh Manesh, Jasleen Matharu, Vihang Mehta, Edward M. Molter, Ivelina Momcheva, Zhiwei Pan, Yuxuan Pang, Pallavi Patil, Rachel Plesha, Marc Rafelski, Mitchell Revalski, Jyotika Roychowdhury, Gregory Rudnick, Swetha Sankar, Maya Seagraves, Lu Shen, Sabnam Shrestha, Manuchehr Taghizadeh-Popp, Jo Taylor, Wei Leong Tee, Scott Tompkins, Feige Wang, Xin Wang, Isak Wold, Jerry J.-Y. Zhang, Qianqiao Zhou, Zihao Zuo

Friday 18 September

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

Short-term solar eclipse predictions using Euclidean geometry and dynamical systems

Alin-Doru Aluas, Valerian-Alin Fodor and Virgilius-Aurelian Minuta

We propose a computationally inexpensive algorithm to determine whether an opaque spherical body eclipses a luminous one, using only classical geometrical tools. We apply this method to the Sun-Earth-Moon system and predict solar eclipses, including their type, beginning, and duration, using the three-body problem. For predictions over a one-year period, the resulting errors are in the order of minutes.
Read the full abstract

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

The Science Potential of Characterizing Gas Giant Exoplanets with HWO

Beck Dacus, Jean-Baptiste Ruffio, Quinn Konopacky et al. (+19 more)

With the ability to directly image Earth-like exoplanets and search their atmospheres for biosignatures, the upcoming Habitable Worlds Observatory (HWO) will also collect high signal-to-noise ratio (S/N) reflected-light photometry and spectra of nearby gas giant exoplanets. Such high-quality data would allow novel investigations into gas giant atmospheric composition, formation, and kinematic properties, and could enable the detection of exomoons around these planets. We use the EXOSIMS direct imaging mission simulator to model HWO observations of Jupiter-radius gas giants at Earth-like and Jupiter-like instellations around the 164 stars in the ExEP target list. We find that HWO should be able to achieve S/N $\geq$ 5 broadband visible-light detections of gas giants in this instellation range within 5 minutes of integration. 10 hours of R=1000 near-IR spectroscopy with HWO should reveal water, methane, and ammonia absorption features in the atmospheres of Jupiter-like gas giants. HWO time-series photometry should exceed 1% flux precision in one hour for any Earth-instellation gas giants around ExEP stars, and for Jupiter-like gas giants at $d\leq$ 7 parsecs. Time-series light curves at this cadence and precision could, over tens of hours, reveal rotation-induced variability comparable to Jupiter's. Eclipses of Mars-sized exomoons may be detectable in high-cadence light curves of Jupiter sized planets in the habitable zones of ExEP stars at $d\leq$ 10 parsecs. For any hypothetical Earth-like exomoons with oxygen-rich atmospheres at $d\leq$ 7 parsecs from the Solar System, HWO might be able to detect the spectral signature of molecular oxygen amid the parent planet's photon noise in deep ($\sim$400 hour integration) spectroscopic HWO observations at R=1000. Such moons, if they exist, represent additional habitable worlds that HWO could investigate for biosignatures.
Read the full abstract

All authors Beck Dacus, Jean-Baptiste Ruffio, Quinn Konopacky, Renyu Hu, Tyler D. Robinson, Mary Anne Limbach, Kielan Hoch, Katelyn Horstman, Bruce Macintosh, Dimitri Mawet, Michael W. McElwain, Bertrand Mennesson, Charley Noecker, Marshall D. Perrin, Laurent Pueyo, Dmitry Savransky, Corey Spohn, Sarah Steiger, Connor Vancil, Ji Wang, Nicole Wolff, Shelley Wright

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

Exoplanet Atmosphere Spectral Sensitivity Analysis with PICASO: Jacobians, Linear-Gaussian Approximations, and Information Content

Natasha E. Batalha and Nicholas F. Wogan

Designing observatory and instrument architectures for complex missions like the Habitable Worlds Observatory (HWO) requires a rapid and rigorous mathematical framework to evaluate trade-offs across bandpass, spectral resolution, and signal-to-noise regimes. While full Bayesian atmospheric retrievals are the gold standard for atmospheric inference, they are too computationally expensive to explore this full parameter space. Here, we present a sensitivity analysis and retrieval diagnostic toolkit within the open-source code PICASO. The core addition to the code base is a flexible solution for computing finite-difference Jacobian matrices, which provides a local linearization of the forward model. These Jacobian matrices characterize the sensitivity of the spectrum (either reflected, thermal, or transmission) to perturbations in any atmospheric state parameter, such as molecular abundances. Given the Jacobian for a certain reference atmosphere, our toolkit provides a suite of analytic diagnostic quantities under Gaussian assumptions for the prior, likelihood, and posterior. These include Fisher-matrix-based estimates of 1$\sigma$ constraint intervals of atmospheric parameters, averaging kernels, singular-value-decomposition diagnostics for parameter degeneracies, and an information-content metric. We validate the results of our toolkit by comparing them to that of a full Bayesian retrieval of an Earth-like planet with an HWO-like facility. We show that our metrics can provide rapid understanding of model parameter sensitivity and that local linear-Gaussian approximations can diagnose dominant degeneracies seen in retrievals as well as provide first order estimates of posterior probability distributions. Ultimately, this provides the community with a complementary toolkit for optimizing instrument design and conducting spectral sensitivity diagnostics.
Read the full abstract

Instrumentation and Methods for Astrophysics

Initial modeling and testbed feasibility studies of WaveDriver: a laser guide star AO system for HWO

Dominic F. Sanchez, Benjamin L. Gerard, Peter Waswa et al. (+16 more)

The Habitable Worlds Observatory (HWO) will require $>100\times$ greater wavefront stability than achieved by JWST, pushing conventional telescope architectures to picometer-level performance limits. WaveDriver is a mission concept that relaxes these constraints by employing an external laser guide star (LGS) spacecraft flying in formation with HWO to enable wavefront sensing and control. Early results from the High Contrast Testbed demonstrate feasibility of required stability using coronagraphs, multiple deformable mirrors, and a suite of wavefront sensors. We report mission design analyses, initial testbed stability metrics, compare sensor performance, and present an optical model that quantifies LGS brightness, conjugation errors, and field errors arising from finite beacon separation.
Read the full abstract

All authors Dominic F. Sanchez, Benjamin L. Gerard, Peter Waswa, Alex Geringer-Smith, Aditya Sengupta, Alexx Perloff, Michael Messerly, William Moore, Matthew Cook, Paul Pax, Cesar Laguna, Mathew DeMartino, Kevin Bundy, Rebecca Jensen-Clem, Aaron Lemmer, S. Mark Ammons, Megan Eckart, Lisa Poyneer, Eric Strang

Instrumentation and Methods for Astrophysics

Probing Millisecond Optical Timescales with Continuous-Readout Mode Observations from ZTF

Shar Daniels, Federica Bianco, Igor Andreoni et al. (+6 more)

The subminute-timescale phase space is an underexplored regime of the optical sky. Sub-second optical observations are difficult to accomplish with traditional CCD exposure-readout cycles, and alternative technologies like EMCCDs and CMOS have historically limited surveys to targeted observation. Continuous-readout mode enables millisecond-timescale observations on traditional cameras by leaving the shutter open during readout, enabling high-cadence observations on all-sky surveys. We present the first results from continuous-readout mode data from the Zwicky Transient Facility. We developed a deep-learning-based data analysis pipeline and report results on 141 square degrees, or 1128 star-hours, of data, sampled at 300x/second. Our Convolutional Neural Network can retrieve optical transients of duration 9.7-29.2 milliseconds with a precision of 66% and recall of 78% for brightness changes of 10% and greater, and our subsequent light curve-based analysis has an efficiency of >94.6%. We retrieve a total of ~300,000 candidates on sources of magnitude G_{RP} < 12, of which 100 are above SNR=1.55 and were visually inspected. After accounting for noise and filtering contaminants both known and unique to this mode of observation, these 100 candidates were eliminated as being astrophysical in nature, leading to upper limits on the observed rate of ~10-ms transient events associated with point sources as well as specifically with white dwarfs and quasars. This first survey-scale characterization of the bright millisecond optical transient and variable sky establishes the rarity of short-timescale variability in the optical regime.
Read the full abstract

All authors Shar Daniels, Federica Bianco, Igor Andreoni, Ashish Mahabal, Rich Dekany, Gregory Dobler, Matthew Graham, Roger Smith, Rujula Yete

Instrumentation and Methods for Astrophysics

The optical high-resolution spectral archive of the HERMES spectrograph mounted on the 1.2m Mercator telescope

Hans Van Winckel, Saskia Prins, Gert Raskin et al. (+13 more)

Context. The HERMES spectrograph is a high-resolution, fibre-fed optical spectrograph of the 1.2m Mercator telescope operated from the Roque de los Muchachos observatory in Spain. HERMES started its scientific operations in June 2009 and has been the workhorse instrument since then. Regular instrument updates have been crucial. They have helped to ensure the continued provision of high-quality spectra. This will continue both now and in the future. Aims. With this contribution we review over 16 years of HERMES operations and we launch and introduce the archive to the interna- tional community at large. We describe the overall performances of the HERMES spectrograph and list the most important instrument upgrades since the start of the operations. We release about 150 000 high-resolution spectra to the community and describe global properties of the datarelease. We use a standard propriety period of 1 year with some exceptions. Methods. We used the German Astrophysical Virtual Observatory (GAVO) DaCHS platform to present the archive in a Virtual Ob- servatory (VO) compatible form with both an access via a dedicated webinterface, and via VO-compliant tools like PyVO, TOPCAT, Aladin etc. We illustrate the use in several worked-out examples to search and download the fully wavelength-calibrated, cosmic- cleaned and barycentric corrected 1D spectra. Results. With this contribution we provide the needed information of the data product and offer a reference paper for the users of the HERMES archive.
Read the full abstract

All authors Hans Van Winckel, Saskia Prins, Gert Raskin, Jesus Perez Padilla, Wim Pessemier, Wim De Meester, Maarten Dirickx, Yves Frémat, Alain Jorissen, Holger Lehmann, Kwinten Missiaen, Maddalena Reggiani, Hugues Sana, Andrew Tkachenko, Bart Vandenbussche, Christoffel Waelkens

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

Nonlinearly Causal General-Relativistic Two-Fluid Dissipative Magnetohydrodynamics

Elias R. Most and Samuel J. Dunham

We present a formulation of general-relativistic (GR) 19-moment dissipative magnetohydrodynamics (MHD), capable of handling all first-order dissipative terms (viscosity, heat conductivity, resistivity and Hall terms), as well as all ideal electron degrees of freedom (number density, momentum and energy) in a GR astrophysical two-fluid plasma. We derive necessary and sufficient nonlinear causality conditions for the constrained first-order 19-moment system, as well as both necessary and sufficient conditions for strong hyperbolicity. To assess the formulation numerically, we develop a high-resolution shock-capturing scheme that solves these equations in a performance-portable fashion. The scheme expresses all evolution equations, including the dissipative and electron sectors, in flux-divergence form, allowing us to model systems with scales separated by orders of magnitude without resolving kinetic scales everywhere on the grid. In addition, we use implicit integration methods to systematically overstep kinetic scales in MHD regions, such as cyclotron and plasma frequencies. To make the scheme as robust as GRMHD codes, we construct necessary and sufficient conditions for a conserved state to be physically admissible, and based on these construct a new physicality-enforcement scheme. As an exact validation comparison, we formulate and derive a full solution to dissipative two-fluid Bondi accretion in general relativity. We then validate the equations against a series of results from kinetic particle-in-cell models of black hole accretion and magnetospheric dynamics, demonstrating that our formulation and scheme can correctly capture major features relevant for feedback on global scales of these solutions, including dimensionless reconnection rates of order $0.1$ and Braginskii-like anisotropic pressures and heat fluxes.
Read the full abstract