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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 11 June

Instrumentation and Methods for Astrophysics

Classification of Astronomical Spectra Using PCA-Compressed Flux and Inverse-Variance Features

Bruno Santos Meneses Barreto and Marcio Eisencraft

This paper evaluates a signal-processing and supervised-learning pipeline for classifying SDSS DR17 astronomical spectra into stars, galaxies, and quasars. Each spectrum is represented by its measured flux and inverse-variance information, combining spectral shape with a wavelength-dependent reliability profile. After resampling onto a common logarithmic wavelength grid, the flux and inverse-variance vectors are standardized and separately compressed using principal component analysis. The resulting components are concatenated and used to train several classifiers. The best performance was obtained with the LightGBM gradient-boosting classifier, reaching $94.6\%$ accuracy and $92.1\%$ balanced accuracy on the test set.
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High Energy Astrophysical Phenomena

Twisted-pair unilateral reconnection: A unifying driver for magnetically powered astrophysical bursts

Shu-Ping Yan, Wenhui Yu, Jing Ye et al. (+11 more)

Magnetic reconnection in twisted loops has long been invoked as an engine powering energetic transients from black hole accretion to neutron star mergers, yet never directly observed. Here we report the first direct observation of the complete reconnection of this type in a solar flare. We find a magnetic loop twisted to about 540 degrees, far exceeding the 180 degrees twist assumed in existing simulations. This extreme twist inherently enables efficient multiple X-line reconnection, akin to the role of turbulence in contemporary theory. Remarkably, the intertwined end breaks unilaterally after reconnection (unlike symmetric breaking in simulations), forming open field lines that release hot plasma – providing a promising mechanism for coronal generation or heating. We first detect hard X-ray emission from the current sheet, directly proving it as a particle accelerator. Moreover, we discover a power-law relationship between quasi-periodic oscillation frequency and magnetic field strength across solar flares, black hole binaries, active galactic nuclei, magnetars, and gamma-ray bursts. This relation identifies twisted-pair unilateral reconnection as a common burst mechanism and provides a natural ruler for cosmic magnetic fields. These findings establish an observational foundation for future reconnection theory and simulations, offering a unified framework for magnetically powered bursts.
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All authors Shu-Ping Yan, Wenhui Yu, Jing Ye, Siming Liu, Yang Su, Huirong Yan, Ping Zhang, Guotianci Xu, Jun Lin, Haisheng Ji, Zongjun Ning, Wei Chen, Li Ji, Jingxing Wang

Cosmology and Nongalactic Astrophysics

Controlling instrumental systematics for the BICEP inflation survey

C. Vergès, P. A. R. Ade, Z. Ahmed et al. (+92 more)

The BICEP series of experiments has been observing CMB polarisation from the South Pole for over 20 years, with the goal of constraining inflationary gravitational waves. The upcoming data release, using data taken through 2024, is forecasted to constrain the tensor-to-scalar ratio $r$ at the level of $\sigma(r) \sim 0.005$ (including delensing), with the longer-term goal of reaching $\sigma(r) \sim 0.001$ by 2034. As the survey sensitivity increases, it is crucial to control instrumental systematics to unprecedented levels, and our goal is to limit dominant sources of systematics to 20% of $\sigma(r)$ or lower. Achieving this requires careful instrumental characterisation and dedicated end-to-end studies to evaluate the impact of each systematic on cosmological parameters. We first present the BICEP calibration program, which characterises the optical, spectral, and polarisation response of the receivers. We then describe the analysis strategies implemented to identify and mitigate systematic contamination, and we detail simulations used to evaluate the impact of residual effects. We focus in particular on beam systematics, the dominant source of systematics for BICEP receivers. Finally, we report preliminary estimates of the expected level of systematic contamination for upcoming BICEP results, and we discuss approaches to evaluate and mitigate instrumental systematics for future surveys.
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All authors C. Vergès, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, H. Boenish, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, G. Halal, M. Halpern, E. Hand, S. A. Harrison, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. L. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. Reintsema, S. Richter, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, R. Schwartz, C. D. Sheehy, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, G. Teply, K. L. Thompson, C. Tucker, A. D. Turner, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, C. L. Wong, W. L. K. Wu, H. Yang, C. Yu, L. Zheng, C. Zhang, S. Zhang

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

Binary Black Hole Parameter Estimation with Hybrid CNN-Transformer Neural Networks

Panagiotis N. Sakellariou, Spiros V. Georgakopoulos, Sotiris Tasoulis et al. (+1 more)

The detection of gravitational waves has revolutionized our ability to explore fundamental aspects of the Universe. Traditionally, modeled gravitational-wave signals have been identified using template-based matched filtering, followed by coincidence analysis across multiple detectors in the signal-to-noise ratio time series. Recent advances in Machine Learning and Deep Learning have sparked growing interest in their application to both signal detection and parameter estimation. In this study, a hybrid Deep Learning strategy is proposed that leverages the effectiveness of Transformer encoders alongside well-established Convolutional Neural Network architectures in an attempt to estimate the intrinsic and extrinsic parameters of non-precessing binary black hole systems. The primary focus of this work is point estimation, producing single best-fit values for each parameter rather than full posterior distributions. This method is evaluated on both simulated signals embedded in Gaussian noise and real gravitational-wave events, and it demonstrates strong predictive performance and robustness across key astrophysical parameters.
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All authors Panagiotis N. Sakellariou, Spiros V. Georgakopoulos, Sotiris Tasoulis, Vassilis P. Plagianakos

Cosmology and Nongalactic Astrophysics

The baryonic Tully-Fisher relation as an independent direct probe of cosmology and of the nature of dark matter

Francesco Sinigaglia

The baryonic Tully-Fisher relation (BTFR), a well-established galaxy scaling relation linking the dynamical mass of rotation-supported galaxies through their maximum circular velocity to the baryonic luminous mass, has emerged over the decades as a fundamental scaling relation and as a robust calibrated distance indicator, thereby providing a robust benchmark to test galaxy formation and evolution theories as well as an independent probe of the expansion of the Universe. In this paper, we show for the first time that the BTFR is also simultaneously directly sensitive to the cosmological parameters $\Omega_m$ and $\sigma_8$, the astrophysical feedback from supernovae (SNe) and active galactic nuclei (AGN), and the mass of warm dark matter particles $M_{\rm wdm}$, and can therefore be used as novel, direct probe of cosmology and fundamental physics. We perform simulation-based inference on the large DREAMS cosmological magneto-hydrodynamic simulations suite and train deep neural networks in the form of normalizing flows to estimate the posterior distributions of $\Omega_m$, $\sigma_8$, $M_{\rm wdm}$ and the three astrophysical free parameters, given a BTFR measurement. Our framework is able to recover unbiased values for $\Omega_m$ and $\sigma_8$, with subpercent deviations accuracy and a $\sim 2.6\%$ and $\sim 3.9\%$ median precision, respectively, to capture the warm dark matter particle mass $M_{\rm wdm}$ within a $\sim 30-35\%$ precision, as well as to constrain the SN feedback parameters (but not the one regulating AGN feedback). We conclude that, beyond its usage as a distance indicator, the BTFR constitutes a direct independent probe of cosmology and fundamental physics and opens new promising avenues, such as constraining the cosmic growth rate and testing gravity theories, to be explored with the future Square Kilometer Array.
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Earth and Planetary Astrophysics

A coupled-oscillator model for the formation of planetary rings

Ruoming Gong, Theodore Broeren, Eryn M. Cangi et al. (+1 more)

We study the dichotomy between compact satellite and ring formation in proto-planetary disks. Specifically, we examine the behavior of a model system of $N$ identical particles locked into circular, gravitationally-bound orbits around a central body. We treat interactions as dominated by inter-particle collisions, and extract an effective two-particle interaction function based on both theory and simulations. We then demonstrate that the expected dynamics are equivalent to a variant of the Kuramoto model, which undergoes a phase transition as parameters vary. This offers a novel potential explanation for the transition between formation of rings versus moons.
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All authors Ruoming Gong, Theodore Broeren, Eryn M. Cangi, Daniel M. Abrams

Instrumentation and Methods for Astrophysics

Autonomous AI-Cosmoindustry and the Quiet Expansion Filter: A Threshold-Based Resolution of the Fermi Paradox

Sergey Ivliev

The Fermi paradox is sharpened, not weakened, by plausible extrapolations of artificial intelligence, autonomous robotics, in-situ resource utilization, orbital manufacturing, space-based computing, and uncrewed interstellar probes. Once a civilization can design, launch, and maintain autonomous industrial systems beyond its home planet, interstellar expansion no longer requires biological starships or a human-like empire. It can proceed through low-mass probes, robotic seed factories, archival payloads, biological repositories, local computation, and slow replication across nearby stellar systems. This paper proposes the quiet expansion filter: old, stable civilizations that reached autonomous AI-cosmoindustry probably did not arise in the part of the Galaxy capable of reaching the Solar System, because after that threshold interstellar expansion becomes too useful, inexpensive, and rational for all civilizations to refuse; however, successful expansion would be machine-mediated, distributed, low-noise, and partly biological rather than Kardashev-like or imperial. Order-of-magnitude estimates indicate that a single post-threshold civilization could saturate its reachable stellar neighborhood within ~10^7 yr – less than 0.1% of Galactic age – at modest energy cost per probe. The novelty of the proposal lies not in any new mechanism but in extending the AI-filter literature toward post-threshold observability predictions. The hypothesis predicts that successful advanced expansion, if present, is more likely to appear as weak artifacts, local probes, small-scale resource processing, exoplanetary anomaly clusters, or techno-biological preservation systems than as galaxy-scale energy harvesting.
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Instrumentation and Methods for Astrophysics

Multi-Variable Stellar Parameter Estimation Using Residual Multitask Neural Networks

Bruno Santos Meneses Barreto and Marcio Eisencraft

We present an end-to-end pipeline for estimating stellar parameters from Sloan Digital Sky Survey Data Release 12 spectra using a fully connected multitask neural network with residual blocks, whose hyperparameters are tuned via Bayesian optimization. The preprocessing pipeline includes per-spectrum standardization, RobustScaler normalization of the target variables – effective temperature $T_{\mathrm{eff}}$, metallicity $[\mathrm{Fe/H}]$, and surface gravity $\log g$ – and data augmentation via Gaussian noise injection. On a held-out test set, the model achieved Mean Absolute Errors (MAE) of $59.76~\mathrm{K}$ for $T_{\mathrm{eff}}$, $0.103~\mathrm{dex}$ for $[\mathrm{Fe/H}]$, and $0.130~\mathrm{dex}$ for $\log g$. Normalized against the full-scale range of each parameter, these results represent range-normalized errors between $1\%$ and $3\%$, achieved with a highly efficient model complexity of approximately 540,000 trainable parameters. These results demonstrate that a compact residual multitask architecture, combined with principled signal preprocessing, provides a parameter-efficient solution for nonlinear parameter estimation in large-scale spectral datasets. In particular, the proposed model achieves competitive performance with substantially lower complexity than deeper neural network baselines.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.soc-ph

AI can help scientists publish less

Gianfranco Bertone

We can do more than defend science from a flood of AI-assisted papers. Used well, AI offers a historic opportunity to correct distortions in the publication system, help us publish fewer and better papers, and give scientists back the time to do their best work.

Astrophysics of Galaxies

GA-NIFS: The interplay between feedback and star formation at 3 < z < 9 probed by JWST/NIRSpec IFU

L. Ulivi, M. Perna, S. Arribas et al. (+24 more)

The study of starburst- and AGN-driven feedback is fundamental for understanding the processes that shape galaxy growth, quench star formation, and drive the co-evolution of galaxies and their central black holes. We present a spatially resolved study of six galaxies at $3 < z < 9$, including starburst- and AGN-dominated systems, observed with JWST/NIRSpec IFU in low- ($R \sim 100$) and high-resolution ($R \sim 2700$) mode. Previous analysis of $R \sim 2700$ data revealed ionized outflows in all these galaxies. We explore possible links between outflows and stellar population properties to assess the mechanisms driving galaxy evolution at early epochs. Combining the spatially resolved stellar population analysis with the outflow properties, we find that the most massive galaxies ($M_\star > 5 \times 10^{10} M_\odot$) with strong AGN-driven ionized outflows show evidence of past quenching episodes occurring within the last $\sim 100$–$300$ Myr, mainly in the nuclear regions ($r < 3$ kpc). In contrast, higher-redshift ($z > 5$) and less massive ($M_\star < 10^{10} M_\odot$) starburst galaxies with powerful (starburst-driven) outflows appear to have experienced continuous growth, with no clear sign of quenching. Massive galaxies with weaker outflows do not show evidence of quenching in their history. One massive AGN host (GS20936) shows evidence for a recent ($10$–$30$ Myr) rejuvenation phase, likely fueled by a recent major merger. These results suggest that (AGN-driven) outflows can already play a key role in shaping the SFHs of massive galaxies at early cosmic epochs.
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All authors L. Ulivi, M. Perna, S. Arribas, B. Rodríguez Del Pino, P. G. Pérez-González, I. Lamperti, C. Marconcini, H. Übler, F. D'Eugenio, T. Böker, A. J. Bunker, S. Carniani, S. Charlot, R. Maiolino, P. Alvarez, E. Bertola, G. Cresci, M. Curti, M. Hamed, L. R. Ivey, G. C. Jones, E. Parlanti, R. Pascalau, C. Prieto Jimenez, B. Trefoloni, G. Venturi, S. Zamora

Instrumentation and Methods for Astrophysics

Design and Commissioning of an Iodine Cell for the ESPRESSO Spectrograph

Gillian Nave and R. Paul Butler

High resolution echelle spectrographs remain the backbone of precision Doppler radial velocity (RV) programs, detecting almost all known exoplanets within 50 pc. Precision Doppler RV spectrographs have traditionally fallen into two camps. Standard unstabilized echelles observe targets through an iodine absorption cell. The iodine spectrum is embedded on the target spectrum, and provides a wavelength scale and a record of the spectrometer point-spread-function (PSF). Super-stabilized spectrometers are placed inside a vacuum tank, temperature stabilized at the level of 0.001 deg C, and fed by two scrambled fibers. One fiber carries the target, the other the calibration source (ThAr, Fabry-Pérot, laser-comb). Both techniques have found hundreds of planets and produce sub m/s uncertainties on the highest resolution echelles currently available. Both techniques have advantages and disadvantages and can be combined with the goal of reducing the long-term Doppler RV uncertainty to the sub 10 cm/s level. We have designed, built, calibrated, and commissioned an iodine cell for the European Southern Observatory's (ESO) ESPRESSO spectrograph. The design and construction of the cell was carried out in 2022. The cell was calibrated at the National Institute of Standards Technology (NIST) Atomic Spectroscopy laboratory in early 2023 and was commissioned in May 2023. The commissioning run was limited to evening and morning twilight on VLT-UT2. Five main sequence dwarf stars ranging in spectral type from G to early K were observed between 4 and 6 nights spanning a total of ten nights.
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High Energy Astrophysical Phenomena

Observational Biases and Improved Modelling of Off-axis Relativistic Jets

A. J. Cooper, A. P. Scott, L. Rhodes et al. (+8 more)

Relativistic Doppler boosting significantly affects the observed emission of astrophysical jets resulting in observational biases. In this work we investigate the observational biases and modelling opportunities which arise due to relativistic boosting using two X-ray binary case studies. Using the one-sided jet ejecta from MAXI J1535-571, we demonstrate that incorporating non-detections of the receding jet ejecta into kinematic modelling can significantly improve parameter estimation, reducing posterior uncertainties by over 40%. For the bipolar jets of MAXI J1820+070, we recover the intrinsic jet rest-frame emission of both approaching and receding jet components, demonstrating that they follow a common powerlaw evolution. Using this rest-frame emission profile as a base model, we show that current observational strategies strongly bias against detecting ejecta with high initial Lorentz factors >5 and receding ejecta components across a broad region of parameter space. These results highlight the importance of observational strategy selection, particularly early-time and late-time observations, and leveraging non-detections in the modelling of relativistic jets. More generally, quantifying observational biases and maximising modelling capabilities by incorporating the non-detection of receding jets can be employed to enhance interpretation of future gravitational-wave/optically-triggered observations of off-axis, extragalactic jetted transients.
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All authors A. J. Cooper, A. P. Scott, L. Rhodes, F. Carotenuto, A. K. Hughes, J. H. Matthews, K. Savard, F. J. Cowie, E. L. Elley, C. Lilje, R. Fender

High Energy Astrophysical Phenomena

Resolving the temporal evolution of M87 jet with $\lesssim0.1$-arcsec Chandra observations

Camille Poitras, Gerrit Schellenberger, Ralph Kraft et al. (+3 more)

We present a 13-year Chandra/HRC-I study of the M87 jet, using point-spread-function deconvolution to achieve unprecedented sub-arcsecond X-ray resolution of its kiloparsec-scale structure and temporal evolution. The deconvolved images reveal previously blended structures within the jet, including two components in HST-1 and complex morphology in downstream knots. Flux measurements reveal a global decrease in X-ray emission across the jet of up to 84 %, consistent with synchrotron cooling. Modeling the fading yields minimum magnetic field strengths of ~324-1006 $\mu$G for HST-1 and ~41-115 $\mu$G for knot A. Consistent with synchrotron cooling, multi-wavelength comparisons with ALMA, JWST, and HST show that the principal X-ray structures closely match the jet width and knot locations observed at lower energies, while the X-ray emission is generally shifted upstream. Proper motion measurements show that jet features exhibit both quasi-stationary and superluminal apparent motions, reaching up to 4.8 $c$ for HST-1, and also demonstrate that unresolved component blending can substantially bias inferred velocities. These results demonstrate the unique capability of high-resolution Chandra X-ray imaging over long temporal baselines to resolve the evolving substructure of relativistic jets and to probe the particle acceleration and energy dissipation processes that shape their dynamics.
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All authors Camille Poitras, Gerrit Schellenberger, Ralph Kraft, Paul Nulsen, Marie-Lou Gendron-Marsolais, Eileen Meyer

Earth and Planetary Astrophysics

Solar System Technosignatures

T. Joseph W. Lazio

NASA has five robotic space probes on escape trajectories from the Solar System, and the Interstellar Probe concept was considered in the recent U.S. Solar & Space Physics Decadal Survey. While none of these robotic probes will be operational when they reach another star, it is natural to ask whether another civilization also might have sent out interstellar probes. Serious consideration of interstellar probes dates at least to R. Bracewell in the early 1960s, and the discovery of three interstellar objects has rekindled some of that interest. I consider current limits on signatures of extraterrestrial technology in the Solar System, both objects on various orbits ("probes") and surface artifacts, using data from planetary exploration and astronomical sky surveys. Perhaps not surprisingly, the completeness to which the Solar System has been searched varies as a function of distance from the Sun. I conclude that only extremely crude upper limits can be placed on the existence of technosignatures in the Solar System and that, in some cases, relatively large probes or surface artifacts would have escaped detection. I also highlight areas that might be profitable for improving these limits considerably.
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Instrumentation and Methods for Astrophysics

A Scalable Fast Multipole Method Poisson Solver for the RAMSES code: I. Unigrid Algorithm

Jun-Young Lee and Romain Teyssier

We present a scalable Poisson solver with $O(N)$ complexity based on the fast multipole method (FMM) implemented in RAMSES. Our FMM constructs a hierarchy of FMM grids on top of the pre-existing Cartesian grid which is used to compute the force for hydrodynamics or particle-mesh simulations. In contrast to the $O(N)$ multigrid solver (MG) - an iterative method that requires multiple V-cycles through a multi-resolution hierarchy of Cartesian grids - the FMM algorithm performs just one upward pass through the same hierarchy, during which multipole expansions are accumulated and shifted, followed by a single downward pass, in which local expansions are propagated. Numerical tests indicate that FMM attains accuracy comparable to that of MG for smooth potentials and is particularly well-suited for problems with isolated boundary conditions, since it avoids the approximate Dirichlet boundary conditions required by MG schemes. Although in theory FMM requires around 30 times more floating-point operations than MG, its higher arithmetic intensity leads to comparable performance and better scalability relative to MG.
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Astrophysics of Galaxies

A novel data-driven approach to extract stellar population properties from galaxy spectra using absorption indices

Zahra Sharbaf, Ignacio Ferreras, Anna R. Gallazzi et al. (+3 more)

In an era of highly complex machine learning methods that often are informative but not straightforward to interpret, Principal Component Analysis (PCA) offers a simple, easily interpretable approach. With no fitting parameters, it extracts the most salient statistical trends in data without the need for training sets. In this paper, we explore a large range of composite stellar population models defined for detailed analyses of galaxy spectra from surveys. Six of the most prominent spectral indices are targeted to visualize a PCA-based latent space created by the model data. The age-metallicity degeneracy is broken in the 3-dimensional space spanned by the first three eigenvectors, but we emphasize that non-trivial combinations of all six absorption indices are needed for this. Moreover, the last eigenvector suggests an intriguing tug of war between two Balmer indices: H$\gamma_A$ and $H\delta_A$, that can help discern the presence of recent bursting behaviour, as it exploits the different behaviour of the two indices over timescales $\sim$0.5-1 Gyr. Comparisons can be made between SDSS and LEGA-C galaxy spectra based on the latent space created by the models. This method, based on pure data, produces excellent results in agreement with standard SPS model fitting techniques, allowing for the study of stellar populations in a variety of surveys or observational/synthetic databases on solid ground.
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All authors Zahra Sharbaf, Ignacio Ferreras, Anna R. Gallazzi, Stefano Zibetti, Daniele Mattolini, Laura Scholz-Díaz

Earth and Planetary Astrophysics

COUNTESS I: A Uniformly Vetted Catalog of Known and New Transiting Exoplanets in the TESS Northern Continuous Viewing Zone

Andrew Hotnisky, Rachel B. Fernandes, Kevin K. Hardegree-Ullman et al. (+9 more)

The Transiting Exoplanet Survey Satellite (TESS) has transformed the study of nearby exoplanetary systems; however, its nominal observing strategy limits sensitivity to planets with orbital periods shorter than $\sim$10 days for most parts of the sky. The two TESS Continuous Viewing Zones (CVZs) provide extended temporal baselines that help overcome this limitation, enabling the detection of longer-period ($>$10 days) transiting planets around nearby stars. Here, we present COUNTESS, a transit-search pipeline optimized for long-baseline TESS observations that combines multi-sector light curves with heterogeneous cadences, and implements fast-folding BLS period detection, vetting, and statistical validation. As a first application of the pipeline, we conducted a search on the primary and first extended mission photometry in the TESS northern CVZ. For this analysis, we used Gaia DR3 and 2MASS photometry to homogeneously derive a stellar catalog of FGKM stars for the TESS northern CVZ, resulting in a sample of 391,059 stars. We used COUNTESS to search for transiting planets around 26,114 of these stars with TESS-SPOC light curves and assessed its performance, recovering 115 out of 159 known TESS Objects of Interest (TOIs; $0.85\ \text{days} < P <124.72\ \text{days}$; $1.03\ R_\oplus < R_p < 16.35\ R_\oplus$). Additionally, we identified 10 new exoplanet candidates ($1.20\ \text{days} < P <34.62\ \text{days}$; $1.73\ R_\oplus < R_p < 4.19\ R_\oplus$) that passed vetting tests, including two new statistically validated sub-Neptunes, TIC 219893931b and TIC 237254473b. COUNTESS enables extended-baseline TESS analyses and identification of longer-period planets, establishing a foundation for future exoplanet demographic studies, including comparisons with Kepler and K2.
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All authors Andrew Hotnisky, Rachel B. Fernandes, Kevin K. Hardegree-Ullman, Steven Giacalone, Kiersten M. Boley, Kristo Ment, Michelle Kunimoto, Galen J. Bergsten, Sakhee Bhure, Jessie L. Christiansen, Brandon Radzom, Suvrath Mahadevan

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Probing New Degrees of Freedom with the Universal Tail of Primordial Black Hole Mass Functions

Kaustubh Agashe, Jae Hyeok Chang, Steven J. Clark et al. (+3 more)

The primordial black hole (PBH) mass function today develops a low-mass evaporation tail whose shape is universal with respect to the initial PBH mass distribution. This universality is fixed by the continuity equation and the Hawking mass-loss rate, but the tail is distorted if additional particle degrees of freedom participate in Hawking evaporation. Since this tail controls high-energy PBH photon emission, such distortions leave characteristic features in the gamma-ray spectrum. We show that these features provide a robust probe of new degrees of freedom, even for subdominant PBHs, within reach of future experiments and independent of visible-sector couplings or relic abundance.
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All authors Kaustubh Agashe, Jae Hyeok Chang, Steven J. Clark, Bhaskar Dutta, Yuhsin Tsai, Tao Xu

Astrophysics of Galaxies

Reconstructing the orbits of Milky Way dwarf galaxies: A Large Magellanic Cloud perspective

Alberto Manuel Martínez-García, Andrés del Pino, Roeland P. van der Marel et al. (+14 more)

The orbital histories of the dwarf satellites of the Milky Way (MW) are key to understanding their evolution and placing their present-day properties in a dynamical context. We present the results of the orbit integration of 72 dwarfs in the vicinity of the MW, based on accurate 6D phase-space coordinates from the literature and a suite of six realistic, time-evolving gravitational potentials that account for the mutual interaction of the MW and the Large Magellanic Cloud (LMC). We provide the largest catalogue of orbital parameters for MW dwarfs to date, in terms of both galaxy sample size and range of potentials explored. We also assess the binding status of the dwarfs and estimate their infall times, finding that the majority of them have spent the last 5 Gyr within the MW virial radius. From the reconstructed orbits, we identify ten likely LMC satellites, several of which have experienced very close passages within the LMC stellar disc. For the Small Magellanic Cloud (SMC), we find that its most recent pericentre about the LMC ($\sim$8 kpc, $\sim$170 Myr ago) is consistent with predictions from the direct collision scenario proposed to explain the LMC's offset and tilted bar. We also note a broad temporal coincidence between previous SMC pericentres and star formation rate peaks reported in both Magellanic Clouds, suggesting a causal connection. Finally, we identify Grus II and Tucana IV as possible MW satellites recently captured by the LMC, based on their pronounced orbital deflections and velocities relative to the LMC.
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All authors Alberto Manuel Martínez-García, Andrés del Pino, Roeland P. van der Marel, Giuseppina Battaglia, Ewa L. Łokas, Eduardo Vitral, Kevin A. McKinnon, Laura L. Watkins, Nitya Kallivayalil, Sangmo Tony Sohn, Guillaume F. Thomas, Salvador Cardona-Barrero, Borja Anguiano, Jairo A. Alzate-Trujillo, Francisco Nogueras-Lara, Paul Bennet, Adrián Hidalgo-Pinilla

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Universality in the Transition from Inspiral to Plunge for Extreme-Mass-Ratio-Inspirals: High-Accuracy Analytic Solutions and Catastrophe Theory

Ariadna Ribes Metidieri, Béatrice Bonga, Badri Krishnan et al. (+1 more)

We revisit the transition from inspiral to plunge for extreme mass-ratio inspirals on quasi-circular, inclined orbits in Kerr spacetime from the perspective of catastrophe theory. Our goal is to uncover the mathematical structures underlying the universality of the transition dynamics, which remains governed by the same Painlevé I differential equation as for equatorial inspirals despite the additional complexity. We first analyze the solution of the Painlevé I equation selected by the physical boundary conditions of slowly evolving quasi-circular inspiral at early times. We argue that these conditions uniquely select the tritronquée solution of Painlevé I. We then compare existing high-accuracy analytic approximations of the tritronquée solution with direct numerical integrations of the Painlevé I equation, finding comparable accuracy and improved stability under differentiation and integration for the analytic solution. In the second part of this work, we show that the equilibrium structure of the Kerr radial effective potential admits a natural interpretation in terms of catastrophe theory. Equatorial orbits are associated with the fold catastrophe, while inclined orbits are described by the cusp catastrophe. In both cases, the transition to plunge corresponds to slow evolution across fold lines of the catastrophe manifold, providing a geometric explanation for the universal appearance of the Painlevé I equation in the transition dynamics.
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All authors Ariadna Ribes Metidieri, Béatrice Bonga, Badri Krishnan, José Luis Jaramillo

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Relativistic and Newtonian Proca Stars: A Tale of Two Limits

Alberto Diez-Tejedor, Carlos Herdeiro, Claudio Lazarte et al. (+4 more)

We investigate a representative set of static solitonic solutions of the Einstein-Proca theory in the Newtonian regime, where the field frequency approaches the particle mass, $\omega \to \mu$, and compare them with the corresponding solutions of the spin-1 Schrödinger-Poisson system, which provides the effective description in this limit. While this correspondence is relatively straightforward in the Einstein-Klein-Gordon case, the vector nature of the Proca field, combined with the enhanced $U(3)$ symmetry of the nonrelativistic spin-1 regime, gives rise to several nontrivial features that require careful analysis. We establish a mapping between the two descriptions by identifying $\ell=0$ electric Proca stars with radially polarized (hedgehog) configurations and $\ell=1$ electric Proca stars with linearly polarized configurations. We further clarify some aspects of the ground state and resolve several apparent discrepancies between relativistic and Newtonian solutions, particularly concerning their morphology and stability properties. An important conclusion of this work is that the nonrelativistic regime supports a richer spectrum of stable equilibrium configurations than the relativistic theory, including stable excited states.
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All authors Alberto Diez-Tejedor, Carlos Herdeiro, Claudio Lazarte, Eugen Radu, Armando A. Roque, Nicolas Sanchis-Gual, Etevaldo dos Santos Costa Filho

Astrophysics of Galaxies

The host halo masses of AGNs and quasars at $z \sim 3-7$ with TNG-Cluster, FLAMINGO and other cosmological galaxy simulations

Akanksha Kapahtia, Annalisa Pillepich, Joey Braspenning et al. (+5 more)

Most observations and clustering analyses suggest that quasars inhabit a narrow range of dark-matter halo masses ($10^{12-13}$ M$_{\odot}$) across cosmic time ($z\lesssim7$). Recent hydrodynamical simulations in gigaparsec-scale volumes now enable direct comparison of this picture with self-consistent galaxy-formation models. We quantify the relation between AGN bolometric luminosity and host halo mass before Cosmic Noon in TNG300, TNG-Cluster, FLAMINGO L1_m8 and L2p8_m9, and in smaller-volume simulations (Illustris, EAGLE, TNG100, and Simba). For AGNs with $L^{\mathrm{AGN}}_{\mathrm{bol}} \ge 10^{42}$ erg s$^{-1}$, more massive haloes host more luminous AGNs on average, but only up to a certain mass. The median luminosity-halo mass relation is highly non-linear, with large scatter, and flattens (FLAMINGO) or turns over (TNG300+TNG-Cluster) at halo mass, $M_{\mathrm{200,crit}} \gtrsim10^{12}$ M$_{\odot}$, at least at $z<5$-6. This high mass AGN quenching also manifests as a characteristic quasar host halo mass: in TNG300+TNG-Cluster, quasars ($L^{\mathrm{AGN}}_{\mathrm{bol}} \sim10^{45-47}$ erg s$^{-1}$) typically reside in haloes of mass $10^{12-12.5}$ M$_{\odot}$ at $z=3$-6, while FLAMINGO quasars extend to median masses of $\sim10^{12.8}$ M$_{\odot}$ at $z\sim3$-4. All simulations predict substantially larger scatter in AGN luminosity at fixed halo mass than in halo mass at fixed luminosity (up to 3 dex versus $\lesssim1$ dex between the 5th and 95th percentiles), implying weak coupling between halo growth and instantaneous SMBH accretion. Consequently, simulated quasar host masses broadly agree with observational estimates. The most luminous AGNs occupy increasingly rare haloes at earlier epochs but typically do not reside in the most massive haloes at any redshift up to $z\approx7$.
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All authors Akanksha Kapahtia, Annalisa Pillepich, Joey Braspenning, Dylan Nelson, Joop Schaye, Eduardo Bañados, Silvia Belladitta, Frederick Davies

Astrophysics of Galaxies

CANUCS/Technicolor Data Release 2: A Catalogue of Galaxy Structural Parameters in up to 29 HST+JWST bands and a Multi-Wavelength Exploration of the Galaxy Size-Mass Relation at $0.6 < z \leq 4$

Maya Merchant, Lamiya A. Mowla, Georgios E. Magdis et al. (+23 more)

We present James Webb Space Telescope (JWST) results of a morphological study of galaxies in the CAnadian NIRISS Unbiased Cluster (CANUCS) and Technicolor surveys, observed in 19 medium- and broadband NIRCam filters in five CANUCS NIRCam Flanking Fields with rest-frame wavelength coverage between $\sim 0.2 - 3.2\mu m$. Using GALFIT, we measure the morphological parameters of $\sim$ 4,100 star-forming galaxies at $0.6 < z \leq 4$ with stellar masses of $8.5 < \text{log}(M_*/M_\odot) \leq 11.5$. This enables us to concurrently examine how galaxy size varies as a function of stellar mass, redshift, and rest-frame wavelength to provide a novel parametrization of the galaxy size-wavelength relation. Additionally, we analyze the evolution of the galaxy size-mass relation in the rest-frame optical and NIR with the introduction of wavelength as a free parameter. We report a gradient in the slope of the size-mass relation with respect to rest-frame wavelength with a critical crossover mass at $\sim 10^{9.5} M_\odot$. We propose this characteristic mass as the stellar mass at which galaxies transition between diffuse and compact morphologies. We concurrently present the data release of morphological measurements of the five CANUCS-Technicolor NIRCam Flanking Fields in which we provide structural parameters for $\sim$ 41,000 galaxies in up to 29 JWST+HST filters.
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All authors Maya Merchant, Lamiya A. Mowla, Georgios E. Magdis, Adam Muzzin, Chris J. Willott, Roberto Abraham, Yoshihisa Asada, Maruša Bradač, Gabriel B. Brammer, Guillaume Desprez, Kartheik G. Iyer, Nicholas S. Martis, Gaël Noirot, Gregor Rihtaršič, Marcin Sawicki, Ghassan T. E. Sarrouh, Sunna Withers, Natalie Allen, Jacqueline Antwi-Danso, Westley Brown, Jon Judež, Danilo Marchesini, Rosa M. Mérida, Katherine Myers, Luke Robbins, Visal Sok

Astrophysics of Galaxies

Turbulence in the multi-phase circumgalactic medium: bridging TNG50 and idealized kpc-scale simulations

Jonas Biba and Dylan Nelson

The circumgalactic medium (CGM) is the extended multi-phase gaseous halo surrounding a galaxy. To study how its dynamics are shaped by the interplay of radiative cooling and turbulence, we first turn to the TNG50 cosmological magnetohydrodynamical simulation. We analyze the turbulent properties of the CGM of Milky Way-like galaxies at z=0, using a multi-scale filtering technique. We find that the CGM hosts predominantly subsonic flows with Mach number ~ 0.1 - 0.7 that are roughly balanced between compressive and solenoidal components with b = M_comp / M_tot ~ 0.3 - 0.6. We then use these physically motivated properties of turbulent CGM media to set the initial conditions and driving parameters for idealized, turbulent box simulations. These represent ~ 1 kpc^3 volumes of the CGM, but reach resolutions higher than available in cosmological volumes such as TNG50. To do so, we implement a turbulent driving algorithm into the AREPO code based on random but smoothly time-fluctuating acceleration fields, and then run a suite of turbulent boxes across the parameter space, including a model for metal-line radiative cooling. Using these simulations, we study how turbulence seeds density fluctuations that trigger thermal instability and promotes mixing between hot and cold phases, depending on the relative timescales of cooling and mixing. The abundance and evolution of cold ~10^4 K gas depends strongly on the strength of turbulence and the efficiency of cooling.
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Solar and Stellar Astrophysics

Dynamo Simulations Confirm Predominantly Toroidal Fields in Near-Core Region of an Intermediate-Mass Star

R.P. Ratnasingam and T.M. Rogers

Recent asteroseismic analysis of the main-sequence F star KIC 9244992 has revealed evidence for a strong, predominantly toroidal magnetic field in its deep radiative interior. Motivated by this result, we present three-dimensional anelastic magneto-hydrodynamic simulations of a rotating 2 solar mass main-sequence star to investigate whether such internal magnetic field strengths and geometries naturally arise in global stellar dynamo simulations for stars within a similar mass range. These simulations self-consistently generate magnetic fields with azimuthal components that dominate over radial components by factors of several near the peak of the Brunt-Vaisala frequency left behind as the core recedes. Moreover, these field strengths arise despite near-uniform, spherically-averaged, rotation from the near-core region to the surface. When the Reynolds number is greater than 100 and the appropriate Rossby number is used, the resulting field strengths and geometrical properties are consistent with those inferred asteroseismically for KIC 9244992. These results indicate that a dominant toroidal field in the near-core region is a generic field configuration in core-convecting stars and should be considered in future asteroseismic inferences.
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High Energy Astrophysical Phenomena

IceCube Real-time Searches for High-energy Neutrinos Coincident with LIGO/Virgo/KAGRA Gravitational-Wave Alerts in O4a

The IceCube Collaboration: R. Abbasi, M. Ackermann, J. Adams et al. (+417 more)

Gravitational-wave events from mergers of compact objects are a predicted source of high-energy neutrinos. Using data from the IceCube Neutrino Observatory, we search for neutrinos coincident with 85 significant and 945 low-significance gravitational-wave candidate events from compact binary coalescences published in real-time by the LIGO-Virgo-KAGRA collaboration during the first part of its fourth observing run (O4a) and its preceding engineering run, within a time window of $\pm500$ seconds centered on the merger time. We report improvements to the online pipelines, including automatic sending of notices, which has decreased the IceCube real-time response time to gravitational-wave events. In addition, we search for long-duration neutrino emission (up to two weeks after the merger) from three candidate events: two neutron star-black hole mergers, and one low-significance gravitational-wave event with a possible subthreshold gamma-ray counterpart. We use two methods, both of which have been previously used to search for neutrino emission associated with gravitational-wave transients: an unbinned maximum likelihood analysis on significant alerts and a Bayesian analysis accounting for astrophysical priors on both significant and low-significance alerts. We find no statistically significant emission from any of the individual gravitational-wave events analyzed, and set upper limits on the time-integrated flux and energy emitted in high energy neutrinos assuming isotropic emission from each event.
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All authors The IceCube Collaboration: R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, L. Brusa, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, S. Minji, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. J. Romfoe, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Velazquez, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, A. Zhang, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas

Astrophysics of Galaxies

On the survival of dark matter spikes: Stellar and compact-object perturbations

Theophanes K. Karydas, Francesca Scarcella, Bradley J. Kavanagh et al. (+1 more)

Establishing realistic expectations for the dark matter (DM) distribution near a supermassive black hole (BH) is essential for assessing environmental imprints on gravitational wave (GW) signals. Using the Galactic Center as an observationally constrained case study, we investigate the evolution of DM density spikes under gravitational perturbations from the nuclear stellar and black hole populations surrounding the central BH. We find that scattering of DM particles by the nuclear star cluster depletes the DM distribution at radii $r \sim 10^{-1}~\mathrm{pc}$, far outside the region where the relevant GW signals are produced. At smaller radii, at $r \sim 10^{-3}~\mathrm{pc}$, the closest known stellar perturbers, S2 and S38, induce only negligible changes to the density profile. At still smaller radii, where no stellar perturbers are currently known, we assess the cumulative impact of past EMRIs by modelling successive mergers with stellar-mass BHs of mass $\sim10~\mathrm{M}_\odot$, in numbers consistent with the expected rate over $10~\mathrm{Gyr}$. We find that these events do not erase the central overdensity, reducing the density only to approximately $82 \%$ of its initial value at $r \lesssim 10^{-5}~\mathrm{pc}$. Our results indicate that, at least at the Galactic Center, DM overdensities around the central BH are expected to remain largely intact under stellar perturbations and plausible stellar-BH merger histories.
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All authors Theophanes K. Karydas, Francesca Scarcella, Bradley J. Kavanagh, Gianfranco Bertone

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

SPLIT: Loosely-coherent inference of long-inspiral gravitational-wave sources for robustness against modeling and data outliers

Shubham Kejriwal

The Laser Interferometer Space Antenna (LISA) will detect gravitational waves (GWs) from dozens of extreme- and intermediate-mass-ratio inspirals (EMRIs/IMRIs). These sources will stay in-band for months to years, offering extraordinary scientific potential. However, their fully phase-coherent analysis standard in current pipelines imposes stringent waveform accuracy requirements; failing to model the signal over such long durations can result in significant systematic biases. To address this, we formulate a robust Bayesian inference framework that segments the data into blocks, infers each block coherently, and recombines the results using loosely-coherent phase information. By restricting full phase-tracking to much shorter block durations, this approach prevents significant accumulation of phase errors. We implement this methodology in SPLIT (Segmented Posteriors for Long-Inspiral Templates), a GPU-accelerated Python package. Applying SPLIT to an environment-rich injection, we demonstrate that while a fully-coherent vacuum-GR analysis incurs a maximum 1D systematic bias of $\approx 4.8\sigma$ from the truth, the shorter integration window of our loosely-coherent approach restricts such biases to $\lesssim 0.5\sigma$. Overall, despite a fractional loss of optimal signal-to-noise ratio, the substantial improvement in parameter accuracy offered by our method presents a highly advantageous trade-off for LISA and other future GW detectors.
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Earth and Planetary Astrophysics · Cross-listed from gr-qc

High-Precision Relativistic Time Scales for Mars Surface and Orbital Clocks

Slava G. Turyshev

We develop a Mars-centered post-Newtonian framework for relating barycentric coordinate time, Mars-centered coordinate time, a conventional Mars surface time scale, and the proper times of landed and orbiting clocks. The construction follows the International Astronomical Union BCRS/TCB formalism, introduces Areocentric Coordinate Time (TCA), and writes each clock transformation as a secular rate plus zero-mean periodic terms. Terms are retained when their fractional-frequency amplitude exceeds 5e-18 or their one-way accumulated timing amplitude exceeds 0.1 ps. The numerical realization uses the GMM-3 Mars gravity field through degree and order 120, point-mass tides from the Sun, Phobos, and Deimos with origin and dipole terms removed, and bounds on omitted local c^-4 and external-perturber terms. Representative low-Mars-orbit, areostationary, Phobos-/Deimos-distance, and highly elliptical relay regimes are evaluated. Relative to the adopted Mars surface scale, a 300 km near-polar clock is slower by 4.56 microseconds per day, while areostationary and Deimos-distance clocks are faster by 9.13 and 9.52 microseconds per day. The leading Mars-J2 timing line is about 87 ps at 300 km altitude and remains several ps near areostationary radius for inclined or librating areosynchronous cases; perihelion-scaled solar tides become retained sub-ps terms in high relay orbits. The result is a reference-system and model-retention framework, not a final operational Mars Time Ephemeris. A realized sub-ps system still requires a selected planetary ephemeris, Mars orientation and seasonal-gravity model, spacecraft orbit determination, calibrated link delays, and covariance analysis. Time-variable low-degree gravity from seasonal CO2 exchange is a leading surface-realization term and must be modeled, monitored, or empirically bounded before sub-ps Mars surface-scale claims are made.
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Astrophysics of Galaxies

Centrally concentrated star formation in young clusters II: Jet feedback

Adilkhan Assilkhan, Sabrina M. Appel, Bekdaulet Shukirgaliyev et al. (+5 more)

Protostellar jets are one of the earliest forms of stellar feedback, but their impact on star formation and cluster assembly in centrally concentrated molecular clouds remains poorly understood. We study how protostellar jets affect the star formation efficiency, the temporal variability of star formation, star cluster structure, and the early dynamical state of centrally concentrated, newly forming star clusters using the Torch star cluster formation framework. We adopt a centrally concentrated initial cloud model with mass M = 2.5 x 10^3 solar masses and compare six pairs of simulations with and without protostellar jets, supplemented by one additional higher resolution pair of simulations. We analyze our simulations using global star formation diagnostics together with structural and dynamical measures of the stellar population. Models with jet feedback achieve star formation efficiencies of 12-16%, while the corresponding models without jets yield higher efficiencies of 19-33%. Jets also cause star formation to occur in discrete bursts rather than continuously, to produce more extended and substructured stellar systems, and to leave behind stellar populations that are less tightly bound and have higher virial parameters. In our centrally concentrated initial conditions, runs with jets form stellar systems that better reproduce the observed range of the projected structural parameter Q_2D in young clusters than runs without jets, indicating that protostellar jets are an important early feedback channel even in centrally concentrated clouds that regulates star formation efficiencies and shapes the emerging cluster structure.
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All authors Adilkhan Assilkhan, Sabrina M. Appel, Bekdaulet Shukirgaliyev, Ernazar Abdikamalov, Simon Portegies Zwart, Eric P. Andersson, Mukhagali Kalambay, Mordecai-Mark Mac Low