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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 13 October

Earth and Planetary Astrophysics

Rings around irregular bodies I. Structure of the resonance mesh, applications to Chariklo, Haumea and Quaoar

Bruno Sicardy, Heikki Salo, Maryame El Moutamid et al. (+2 more)

Three ring systems have been discovered to date around small irregular objects of the solar system (Chariklo, Haumea and Quaoar). For the three bodies, material is observed near the second-order 1/3 Spin-Orbit Resonance (SOR) with the central object, and in the case of Quaoar, a ring is also observed near the second-order resonance 5/7 SOR. This suggests that second-order SORs may play a central role in ring confinement. This paper aims at better understanding this role from a theoretical point of view. It also provides a basis to better interpret the results obtained from N-body simulations and presented in a companion paper. A Hamiltonian approach yields the topological structure of phase portraits for SORs of orders from one to five. Two cases of non-axisymmetric potentials are examined: a triaxial ellipsoid characterized by an elongation parameter C22 and a body with mass anomaly mu, a dimensionless parameter that measures the dipole component of the body's gravitational field. The estimated triaxial shape of Chariklo shows that its corotation points are marginally unstable, those of Haumea are largely unstable, while those of Quaoar are safely stable. The topologies of the phase portraits show that only first- (aka Lindblad) and second-order SORs can significantly perturb a dissipative collisional ring. We calculate the widths, the maximum eccentricities and excitation time scales associated with first- and second-order SORs, as a function of C22 and mu. Applications to Chariklo, Haumea and Quaoar using mu ~ 0.001 show that the first- and second-order SORs caused by their triaxial shapes excite large (>~ 0.1) orbital eccentricities on the particles, making the regions inside the 1/2 SOR inhospitable for rings. Conversely, the 1/3 and 5/7 SORs caused by mass anomalies excite moderate eccentricities (<~ 0.01), and are thus a more favorable place for the presence of a ring.
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All authors Bruno Sicardy, Heikki Salo, Maryame El Moutamid, Stefan Renner, Damya Souami

Astrophysics of Galaxies

PDRs4All XVII: Formation and excitation of HD in photodissociation regions. Application to the Orion Bar

Marion Zannese, Jacques Le Bourlot, Evelyne Roueff et al. (+12 more)

The James Webb Space Telescope enabled the first detection of several rovibrational emission lines of HD in the Orion Bar, a prototypical photodissociation region. This provides an incentive to examine the physics of HD in dense and strong PDRs. Using the latest data available on HD excitation by collisional, radiative and chemical processes, our goal is to unveil HD formation and excitation processes in PDRs by comparing our state-of-the-art PDR model with observations made in the Orion Bar and discuss if and how HD can be used as a complementary tracer of physical parameters in the emitting region. We compute detailed PDR models, using an upgraded version of the Meudon PDR code, which are compared to NIRSpec data using excitation diagrams and synthetic emission spectra. The models predict that HD is mainly produced in the gas phase via the reaction D + H2 = H + HD at the front edge of the PDR and that the D/HD transition is located slightly closer to the edge than the H/H2 transition. Rovibrational levels are excited by UV pumping. In the observations, HD rovibrational emission is detected close to the H/H2 dissociation fronts of the Orion Bar and peaks where vibrationally excited H2 peaks, rather than at the maximum emission of pure rotational H2 levels. We derive an excitation temperature around Tex ~ 480 - 710 K. Due to high continuum in the Orion Bar, fringes lead to high noise levels beyond 15 $\mu$m, no pure rotational lines of HD are detected. The comparison to PDR models shows that a range of thermal pressure P = (3-9)x10$^7$ K cm$^{-3}$ with no strong constraints on the intensity of the UV field are compatible with HD observations. This range of pressure is compatible with previous estimates from H2 observations with JWST. This is the first time that observations of HD emission lines in the near-infrared are used to put constraints on the thermal pressure in the PDR.
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All authors Marion Zannese, Jacques Le Bourlot, Evelyne Roueff, Emeric Bron, Franck Le Petit, Dries Van De Putte, Maryvonne Gerin, Naslim Neelamkodan, Javier R. Goicoechea, John Black, Ryan Chown, Ameek Sidhu, Emilie Habart, Els Peeters, Olivier Berné

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

Hydrodynamic properties in soliton field theory

Qian Chen

The crucial role of hydrodynamic instabilities in soliton field theory is revealed. We demonstrate that the essential of soliton formation mechanism is the sound mode instability induced by thermodynamic instability. This instability triggers phase separation, where new thermal phases are generated to produce solitons. These solitons can be regarded as a coexistence state composed of a matter phase and a vacuum phase, with an interface providing surface tension to maintain dynamical equilibrium. The phase separation mechanism naturally allows the existence of vacuum bubbles, characterized by a vacuum phase surrounded by a matter phase with negative pressure. Furthermore, we show that the soliton interface resembles a fluid membrane, whose interface pressure satisfies a Young-Laplace-type relation, resulting in the emergence of the membrane instability induced by surface tension. In the thin-wall limit, the dispersion relation is analytically derived. This instability triggers topological transition of the interface, splitting a cylindrical interface into multiple spheres with a smaller total surface area. Such results highlight the duality between solitons and fluids, providing a field theory description for hydrodynamics with interfaces.
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Earth and Planetary Astrophysics

Analyzing Data Quality and Decay in Mega-Constellations: A Physics-Informed Machine Learning Approach

Katarina Dyreby, Francisco Caldas and Cláudia Soares

In the era of mega-constellations, the need for accurate and publicly available information has become fundamental for satellite operators to guarantee the safety of spacecrafts and the Low Earth Orbit (LEO) space environment. This study critically evaluates the accuracy and reliability of publicly available ephemeris data for a LEO mega-constellation - Starlink. The goal of this work is twofold: (i) compare and analyze the quality of the data against high-precision numerical propagation. (ii) Leverage Physics-Informed Machine Learning to extract relevant satellite quantities, such as non-conservative forces, during the decay process. By analyzing two months of real orbital data for approximately 1500 Starlink satellites, we identify discrepancies between high precision numerical algorithms and the published ephemerides, recognizing the use of simplified dynamics at fixed thresholds, planned maneuvers, and limitations in uncertainty propagations. Furthermore, we compare data obtained from multiple sources to track and analyze deorbiting satellites over the same period. Empirically, we extract the acceleration profile of satellites during deorbiting and provide insights relating to the effects of non-conservative forces during reentry. For non-deorbiting satellites, the position Root Mean Square Error (RMSE) was approximately 300 m, while for deorbiting satellites it increased to about 600 m. Through this in-depth analysis, we highlight potential limitations in publicly available data for accurate and robust Space Situational Awareness (SSA), and importantly, we propose a data-driven model of satellite decay in mega-constellations.
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High Energy Astrophysical Phenomena

Survival of the accretion disk in LMC Recurrent Nova 1968-12a: UV–X-ray case study of the 2024 eruption

Judhajeet Basu, G.C. Anupama, Jan-Uwe Ness et al. (+3 more)

We report on UV and X-ray observations of the 2024 eruption of the recurrent nova LMCN 1968-12a, a rapidly recurring extragalactic system with a $\sim$4.3 year recurrence period and a massive white dwarf (WD). The eruption was discovered on 2024 August 1.8 by Swift, and subsequently monitored using AstroSat's UVIT and SXT, along with Swift/UVOT and XRT. The multi-wavelength light curves reveal a rapid UV-optical decline, followed by a plateau phase exhibiting 1.26-day modulations consistent with the orbital period. The Supersoft (SSS) X-ray emission, that emerged by day 5, exhibited a double peak, suggesting variable obscuration that could be due to an inhomogeneous nova ejecta or due to a nova super-remnant along the line of sight. Time-resolved X-ray spectroscopy shows a blackbody component with T $\approx 10^6$ K. The SEDs obtained concurrently in the UV, peaking at T $\approx$ 20,000 K and with a source radius $\sim$2-3 R$_\odot$, are inconsistent with emission from the secondary star or nova photosphere alone. Instead, the UV emission is attributed to an irradiated accretion disk that survived the eruption. The persistent UV plateau and its temperature suggest that the accretion disk was not completely disrupted and resumed activity within days, consistent with recent findings in other rapidly recurring novae such as U~Sco and M31N~2008-12a.
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All authors Judhajeet Basu, G.C. Anupama, Jan-Uwe Ness, Kulinder Pal Singh, Sudhanshu Barway, Shatakshi Chamoli

High Energy Astrophysical Phenomena

Second Discovery of GeV-TeV Connection from the Globular Cluster UKS 1

Jiwon Shin, C. Y. Hui, Sangin Kim et al. (+2 more)

Using 16 years of data collected by Fermi Large Area Telescope and 1523 days of survey data from High Altitude Water Cherenkov (HAWC) Observatory, we discovered the long-sought second GeV-TeV connection towards the globular cluster (GC) UKS 1 (Shin et al. 2025). Gamma-ray spectroscopy suggests that the GeV emission can be attributed to both the pulsar magnetosphere and inverse Compton scattering (ICS) by the pulsar wind. In particular, the TeV peak is displaced from the cluster center by several tidal radii in the trailing direction of the proper motion of UKS 1. This alignment supports a scenario in which relativistic leptons, likely driven by a millisecond pulsar population, produce very-high-energy (VHE) gamma-rays via ICS within a bow shock tail. Our findings not only highlights GCs as potential sources of VHE gamma-rays, but also offers a rare opportunity to probe cosmic ray transport in the Milky Way by studying particle propagation and anisotropic gamma-ray production associated with the extended, offset TeV feature of UKS 1.
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All authors Jiwon Shin, C. Y. Hui, Sangin Kim, Kwangmin Oh, Ellis R. Owen

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

Reconstructing and resampling: a guide to utilising posterior samples from gravitational wave observations

Gregory Ashton

The LIGO, Virgo, and KAGRA (LVK) gravitational-wave observatories have opened new scientific research in astrophysics, fundamental physics, and cosmology. The collaborations that build and operate these observatories release the interferometric strain data as well as a catalogue of observed signals with accompanying Bayesian posterior distributions. These posteriors, in the form of equally-weighted samples, form a dataset that is used by a multitude of further analyses seeking to constrain the population of merging black holes, identify lensed pairs of signals, and much more. However, many of these analyses rely, often implicitly, on the ability to reconstruct the likelihood and prior from the inputs to the analysis and apply resampling (a statistical technique to generate new samples varying the underlying analysis assumptions). In this work, we first provide a guide on how to reconstruct and modify the posterior density accurately from the inputs for analyses performed with the Bilby inference library. We then demonstrate and compare resampling techniques to produce new posterior sample sets and discuss Pareto-smoothing to improve the efficiency. Finally, we provide examples of how to use resampling to study observed gravitational-wave signals. We hope this guide provides a useful resource for those wishing to use open data products from the LVK for gravitational-wave astronomy.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.SE

Interoperability From OpenTelemetry to Kieker: Demonstrated as Export from the Astronomy Shop

David Georg Reichelt, Shinhyung Yang and Wilhelm Hasselbring

The observability framework Kieker provides a range of analysis capabilities, but it is currently only able to instrument a smaller selection of languages and technologies, including Java, C, Fortran, and Python. The OpenTelemetry standard aims for providing reference implementations for most programming languages, including C# and JavaScript, that are currently not supported by Kieker. In this work, we describe how to transform OpenTelemetry tracing data into the Kieker framework. Thereby, it becomes possible to create for example call trees from OpenTelemetry instrumentations. We demonstrate the usability of our approach by visualizing trace data of the Astronomy Shop, which is an OpenTelemetry demo application.
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Astrophysics of Galaxies

Measuring the Evolution of Bulge, Disk and Colour Gradients in HST Observations of Galaxies with 3D Modelling

N. Welikala, L. Miller, A. N. Taylor et al. (+1 more)

We measure galaxy structural properties and colour gradients using HST images to trace the evolution of galaxy components. We develop and apply a physically motivated 3D bulge+disk modelling framework, jointly fitting the components in 2505 galaxies in GOODS-South across seven bands (bvizYJH) to $I_{\rm AB}=25.5$, accounting for different component ellipticities and inclination-dependent dust extinction. Extinction strongly affects structural parameters and colour gradients in $\sim$26% of the sample - primarily edge-on galaxies with central obscuration (B-band face-on optical depth $\tau \simeq 4$) that reveal clear bulge components in the near-infrared. Despite irregular morphologies, the model captures observed colour gradients well. Bulges at $z \sim 1$ differ markedly from $z \sim 0$, with typical Sérsic index $n \sim 1.0$ and bulge-to-disc size ratio $R_{\rm e}/h_{\rm d} \sim 0.15$, suggesting most galaxies host pseudo-bulges formed via secular evolution. Galaxy ellipticity correlates strongly with disk scale-length. We trace bulge and disk evolution from $z \sim 0$ to $z \sim 2.5$: bulges are redder than disks (observed-frame) at $z < 1.4$, but colours converge at higher redshifts and fainter magnitudes. Redder galaxies show redder cores relative to their outskirts, and brighter galaxies have redder cores. These results provide new measurements of bulge and disk structural properties at $z \sim 1$ and observational constraints on their evolution, while also providing empirically motivated input distributions for assessing colour gradient systematics in weak lensing surveys.
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All authors N. Welikala, L. Miller, A. N. Taylor, G. Congedo

Astrophysics of Galaxies

The evolution of CH in Planck Galactic Cold Clumps

Gan Luo, Arshia M. Jacob, Marco Padovani et al. (+6 more)

Methylidyne (CH) has long been considered a reliable tracer of molecular gas in the low-to-intermediate extinction range. Although extended CH 3.3 GHz emission is commonly observed in diffuse and translucent clouds, observations in cold, dense clumps are rare. In this work, we conducted high-sensitivity CH observations toward 27 PGCCs with the Arecibo 305m telescope. Toward each source, the CH data were analyzed in conjunction with $^{13}$CO (1–0), HINSA, and H$_2$ column densities. Our results revealed ubiquitous subsonic velocity dispersions of CH, in contrast to $^{13}$CO, which is predominantly supersonic. The findings suggest that subsonic CH emissions may trace dense, low-turbulent gas structures in PGCCs. To investigate environmental effects, particularly the cosmic-ray ionization rate (CRIR), we estimated CRIR upper limits from HINSA, yielding values from $(8.1\pm4.7)\times10^{-18}$ to $(2.0\pm0.8)\times10^{-16}$ s$^{-1}$ ($N_{H_2}$ from $(1.7\pm0.2)\times10^{21}$ to $(3.6\pm0.4)\times10^{22}$~cm$^{-2}$). This result favors theoretical predictions of a cosmic-ray attenuation model, in which the interstellar spectra of low-energy CR protons and electrons match Voyager measurements, although alternative models cannot yet be ruled out. The abundance of CH decreases with increasing column density, while showing a positive dependence on the CRIR, which requires atomic oxygen not heavily depleted to dominate CH destruction in PGCCs. By fitting the abundance of CH with an analytic formula, we place constraints on atomic O abundance ($2.4\pm0.4\times10^{-4}$ with respect to total H) and C$^+$ abundance ($7.4\pm0.7\times10^{13}\zeta_2/n_{\rm H_2}$). These findings indicate that CH formation is closely linked to the C$^+$ abundance, regulated by cosmic-ray ionization, while other processes, such as turbulent diffusive transport, might also contribute a non-negligible effect.
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All authors Gan Luo, Arshia M. Jacob, Marco Padovani, Daniele Galli, Ana López-Sepulcre, Ningyu Tang, Di Li, Jing Zhou, Pei Zuo

Instrumentation and Methods for Astrophysics

Machine Learning Frameworks for Large-Scale Radio Surveys: A Summary of Recent Studies

Nikhel Gupta

The rapid growth of large-scale radio surveys, generating over 100 petabytes of data annually, has created a pressing need for automated data analysis methods. Recent research has explored the application of machine learning techniques to address the challenges associated with detecting and classifying radio galaxies, as well as discovering peculiar radio sources. This paper provides an overview of our investigations with the Evolutionary Map of the Universe (EMU) survey, detailing the methodologies employed-including supervised, unsupervised, self-supervised, and weakly supervised learning approaches – and their implications for ongoing and future radio astronomical surveys.
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High Energy Astrophysical Phenomena

Quasi-Periodic Oscillations in Gamma-Ray Bursts' Prompt Light Curves

Mariusz Tarnopolski

I report on the discovery of 34 new quasi-periodic oscillations (QPOs) in the prompt light curves of long gamma-ray bursts (GRBs) from the Swift/BAT catalog: with one or more constant leading periods, as well as several chirping signals. This is the largest homogenously identified sample or GRB QPOs to date. The presence of QPOs suggests the existence of characteristic time scales that at least in some GRBs might be related to the dynamical properties of plasma trajectories in the accretion disks powering the relativistic jets. Several scenarios for their origin were examined. We identify non-planar orbits around Kerr black holes, the Lense-Thirring effect, and shock oscillations as plausible mechanisms for the QPO generation.
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Cosmology and Nongalactic Astrophysics

Wide Area VISTA Extragalactic Survey (WAVES): Redshift-limited selection of targets for the Wide survey using decision-tree classification

G. Kaur, M. Bilicki, S. Bellstedt et al. (+11 more)

The Wide-Area VISTA Extragalactic Survey (WAVES) on the 4-metre Multi-Object Spectroscopic Telescope (4MOST) includes two flux-limited subsurveys with very high (95%) completeness requirements: Wide over $\sim\!1200$ deg$^2$ and Deep over $\sim\!65$ deg$^2$. Both are $Z$-band selected, and additionally redshift-limited, while the true redshifts are not known a priori but will only be measured by 4MOST. Here, we present a classification-based method to select the targets for WAVES-Wide. Rather than estimating individual redshifts for the input photometric galaxies, we assign probabilities of them being below $z=0.2$, the redshift limit of the subsurvey. This is done with the supervised machine learning approach of eXtreme Gradient Boosting (XGB), trained and tested on a comprehensive spectroscopic sample overlapping with WAVES fields and using nine-band VST+VISTA photometry for the feature space. We check the performance of our classifier both for the fiducial WAVES-Wide limits, as well as for a range of neighboring redshift and magnitude thresholds, finding purity and completeness at the level of 90-95% depending on the test set. The metrics deteriorate for sources close to the selection limits and for test sets selected from DESI, not used in training. We apply the classifier trained on the full spectroscopic sample to the 8.6 million galaxies from the WAVES photometric catalog. This gives us about 1.2 million target candidates, reducing to 1 million if we apply an XGB probability threshold $P_\mathrm{XGB}(z\leq0.2) > 0.72$. Our work demonstrates that a machine-learning classifier could be used to select a flux- and redshift-limited sample from deep photometric data.
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All authors G. Kaur, M. Bilicki, S. Bellstedt, E. Tempel, W. A. Hellwing, I. Baldry, B. Bandi, S. Barsanti, S. Driver, N. Guerra-Varas, B. Holwerda, C. Lagos, J. Loveday, A. Robotham

Astrophysics of Galaxies

Intrinsic alignment of disks and ellipticals across hydrodynamical simulations

M. L. van Heukelum and N. E. Chisari

The correlations between the positions and shapes of galaxies, i.e. intrinsic alignments, have been measured in many observational studies and hydrodynamical simulations. The position-shape correlation measurements of disk galaxies with varying methodologies, samples and hydrodynamical simulations are inconsistent in amplitude and sign. This work compares the correlations of disk and elliptical shapes around all galaxy positions and disk shapes around the positions of ellipticals at $z=0$ and $z=1$ for two different shape definitions in TNG300, Horizon-AGN and EAGLE for multiple morphological definitions in a consistent way. All types of signals are positive and robust in TNG300 and EAGLE and positive or null in Horizon-AGN. A re-weighting of the ellipticals around all galaxies correlations in TNG300, according to the underlying stellar mass distributions of the samples, suggests that stellar mass is the driving factor determining the amplitude of the correlations. The exception to this is the negative correlation of disks around ellipticals in Horizon-AGN. This arises for reduced shapes, which down-weight the outskirts of galaxies, at $z=1$, when disks are identified via a threshold in $|v/\sigma|$, the rotational velocity over the velocity dispersion.
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Instrumentation and Methods for Astrophysics

Argus: JAX state-space filtering for gravitational wave detection with a pulsar timing array

Tom Kimpson, Nicholas J. O'Neill, Patrick M. Meyers et al. (+1 more)

Argus is a high-performance Python package for detecting and characterising nanohertz gravitational waves in pulsar timing array data. The package provides a complete Bayesian inference framework based on state-space models, using Kalman filtering for efficient likelihood evaluation. Argus leverages JAX for just-in-time compilation, GPU acceleration, and automatic differentiation, facilitating rapid Bayesian inference with gradient-based samplers. The state-space approach provides a computationally efficient alternative to traditional frequency-domain methods, offering linear scaling with the number of pulse times-of-arrival, and natural handling of non-stationary processes.
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All authors Tom Kimpson, Nicholas J. O'Neill, Patrick M. Meyers, Andrew Melatos

Cosmology and Nongalactic Astrophysics

Detection of Axion Stars in Galactic Magnetic Fields

Kuldeep J. Purohit, Jitesh R. Bhatt, Subhendra Mohanty et al. (+1 more)

We perform a linear mode analysis of a uniformly distributed cloud of axion-like particles (ALPs) embedded in a magnetized intergalactic medium, in order to investigate the stability of axion stars under realistic astrophysical conditions. We find that when the frequency $\omega$ of transverse waves is much smaller than the collision frequency $\nu_c$ of the intergalactic plasma, the conversion of ALPs into photons occurs on timescales far longer than the age of the Universe, ensuring stability of the star. In the opposite regime, $\omega \gg \nu_c$, significant axion-to-photon conversion may occur if the condition $\tfrac{\beta^2}{m_a^2-\omega_p^2} < 1$ is satisfied, where $\beta$ depends on the ALP–photon coupling and the magnetic field, $m_a$ is the ALP mass, and $\omega_p$ is the plasma frequency. We have calculated up to second order in perturbations to compute the effect of an ALP star. Since the calculated value of parameter $\beta ^2$ is extremely small in comparison with $\omega^2_p$, we argue that the direct detection of an axion star is highly unlikely in experiments like NCLE. However, since the calculated $\beta$ is extremely small compared to $\omega_p$, this requires an unrealistically fine-tuned coincidence between $m_a$ and $\omega_p$. As a consequence we argue that that detection of Our results therefore suggest that axion stars remain stable in typical intergalactic environments, though extreme magnetic fields (e.g.\ near magnetars) may lead to different outcomes.
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All authors Kuldeep J. Purohit, Jitesh R. Bhatt, Subhendra Mohanty, Prashant K. Mehta

High Energy Astrophysical Phenomena

Resonant W and Z Boson Production in FSRQ Jets: Implications for Diffuse Neutrino Fluxes

Ji-Hoon Ha and Ibragim Alikhanov

Blazars, particularly Flat Spectrum Radio Quasars (FSRQs), are well-known for their ability to accelerate a substantial population of electrons and positrons, as inferred from multiwavelength radiation observations. Therefore, these astrophysical objects are promising candidates for studying high-energy electron–positron interactions, such as the production of $W^{\pm}$ and $Z$ bosons. In this work, we explore the implications of electron–positron annihilation processes in the jet environments of FSRQs, focusing on the resonant production of electroweak bosons and their potential contribution to the diffuse neutrino flux. By modeling the electron distribution in the jet of the FSRQ 3C~279 during a flaring state, we calculate the reaction rates for $W^{\pm}$ and $Z$ bosons and estimate the resulting diffuse fluxes from the cosmological population of FSRQs. We incorporate the FSRQ luminosity function and its redshift evolution to account for the population distribution across cosmic time, finding that the differential flux contribution exhibits a pronounced peak at redshift $z \sim 1$. While the expected fluxes remain well below the detection thresholds of current neutrino observatories such as IceCube, KM3NeT, or Baikal-GVD, the flux from $Z$ boson production within the jet blob is many orders of magnitude smaller than the total diffuse astrophysical neutrino flux. These results provide a theoretical benchmark for the role of Standard Model electroweak processes in extreme astrophysical environments, highlighting the interplay between particle physics and astrophysics, and illustrating that even extremely rare high-energy interactions can leave a subtle, theoretically meaningful imprint on the diffuse astrophysical neutrino background.
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Cosmology and Nongalactic Astrophysics

Cavendish experiment with fast radio bursts on cosmological scales

Shuren Zhou and Pengjie Zhang

A key measure of gravity is the relation between the Weyl potential $\Psi+\Phi$ and the matter overdensity $\delta_m$, encapsulated as an effective gravitational constant $G_{\rm light}$ for light motion. Its value, along with possible spatial and temporal variations, is essential for probing physics beyond Einstein gravity. However, the absence of an unbiased proxy for $\delta_m$ prevents the direct measurement of $G_{\rm light}$. In this work, we show that within a theoretical framework respecting the weak equivalence principle, the dispersion measure (DM) of localized fast radio bursts (FRBs) serve as a good proxy for $\delta_m$. We further propose an FRB-based estimator $F_G$ to directly measure $G_{\rm light}$, combining galaxy-DM of localized FRBs and galaxy-weak lensing cross-correlations. With a conservative cut $k\leq 0.1\, h/{\rm Mpc}$, the measurement can achieve a precision of $\lesssim 10\% \sqrt{10^5/N_{\rm FRB}}$ over 10 equal-width redshift bins at $z\lesssim 1$. The major systematic error, arising from the clustering bias of electrons traced by the FRB DM, remains subdominant at the $5\%$ level. It can be further mitigated to the $\lesssim 1\%$ level, based on the gastrophysics-agnostic behavior that the clustering bias of total baryons (ionized diffuse gas, stars, neutral hydrogen, etc) approaches unity at sufficiently large scales. Therefore, FRBs shed light on gravitational physics across spatial and temporal scales spanning 20 orders of magnitude.
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Earth and Planetary Astrophysics

On The Orbital Evolution of Multiple Wide Super-Jupiters: How Disk Migration and Dispersal Shape the Stability of The PDS 70 System

Clarissa R. Do Ó, Jaehan Bae, Quinn M. Konopacky et al. (+4 more)

Direct imaging has revealed exoplanet systems hosting multiple wide-orbit Super-Jupiters, where planet-planet interactions can shape their long-term dynamical evolution. These strong perturbations may lead to orbital instability, raising questions about the long-term survival of such systems. Shortly after formation, planet-disk interactions can shepherd planets into mean-motion resonances, which may promote long-term stability as seen in HR 8799. However, early-stage processes such as disk photoevaporation and viscosity can influence these outcomes. The $\sim$5 Myr-old PDS 70 system offers a unique laboratory to investigate these processes: its two massive ($>$4 $M_{Jup}$), wide-orbit ($>$20 AU) giants are still embedded in their natal disk. We perform 2D hydrodynamic simulations of the system, allowing the disk to disperse via photoevaporation. Once the disk dissipates, we continue to track the planets' orbital evolution over Gyr timescales using N-body simulations. We find that the system is likely to remain stable for $>$ 1 Gyr. To assess the importance of disk-driven evolution, we compare these results with disk-free N-body simulations using orbital parameters constrained by orbit fits that include recent relative astrometry and radial velocities from the literature. In this case, we find that only $\lesssim 4\%$ of posterior is stable for 100 Myr, highlighting the importance of considering disk-driven evolution for long-term dynamics stability of exoplanetary systems. We also simulate two three-planet configurations including the proposed inner candidate "PDS 70 d", finding that a higher photoevaporation leads the system to become unstable in $<$ 10 Myr.
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All authors Clarissa R. Do Ó, Jaehan Bae, Quinn M. Konopacky, Jayke S. Nguyen, Patrick Diamond, Krzysztof Goździewski, Dawid Jankowski

Astrophysics of Galaxies

The Relation Between AGN and Host Galaxy Properties in the JWST Era: II. The merger-driven evolution of Seyferts at Cosmic Noon

Nina Bonaventura, Jianwei Lyu, George H. Rieke et al. (+3 more)

In Paper I, we exploited the unsurpassed resolution and depth of JWST/NIRCam imagery to investigate the relationship between AGN and host-galaxy properties in the JWST era, finding a correlation between the level of spatial disturbance (as measured by shape asymmetry, $A_S$) and obscuration ($N_H$). Here in Paper II, we report an expansion of our X-ray and infrared analysis of Seyfert-luminosity host galaxies with four additional metrics to the single-metric morphology analysis of Paper I, as well as new samples of inactive control galaxies. This expanded study of one of the largest and most complete, multi-wavelength samples of AGN detected at $0.6<z<2.4$ in the GOODS-South and North fields, confirms that mergers surprisingly play a significant role in obscured, sub-quasar AGN host galaxies. Additionally, the pattern of morphological disturbances observed amongst the X-ray- and mid-IR-selected AGN suggests that these represent different phases of AGN evolution tied to a major-merger timeline, as opposed to distinct populations of AGN. These results indicate that mergers are important in triggering sub-quasar AGN at these redshifts.
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All authors Nina Bonaventura, Jianwei Lyu, George H. Rieke, Andrew J. Bunker, Chris J. Willott, Christopher N. A. Willmer

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

Detecting gravitational waves with spin systems

Jiamin Liang, Mingqiu Li, Yu Gao et al. (+3 more)

The observation of gravitational waves has opened a new window into the Universe through gravitational-wave astronomy. However, high-frequency gravitational waves remain undetected. In this work, we propose that spin systems can be employed to detect gravitational waves in this unexplored frequency regime. We derive the spin's response to gravitational waves and identify three distinct effects: the well-known Gertsenshtein effect, a metric-induced interaction, and the gravitational spin Hall effect. We focus on nuclear spins and utilize nuclear magnetic resonance to enhance the gravitational response, leveraging the advantages of long coherence time, high polarization, and a small gyromagnetic ratio. The proposed experimental scheme is capable of probing gravitational waves in the kilohertz to gigahertz range, with projected sensitivities reaching $\sqrt{S_h}\approx10^{-20}~\mathrm{Hz}^{-1/2}$.
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All authors Jiamin Liang, Mingqiu Li, Yu Gao, Wei Ji, Sichun Sun, Qi-Shu Yan

Astrophysics of Galaxies

Three Birds with One Stone: Core-Collapsed SIDM Halos as the Common Origin of Dense Perturbers in Lenses, Streams, and Satellites

Hai-Bo Yu

We show that core-collapsed self-interacting dark matter halos of mass $\sim 10^6\,{M_\odot}$, originally simulated to explain the dense perturber of the GD-1 stellar stream, also reproduce the structural properties inferred for the dense perturber detected in the strong lensing system JVAS B1938+666 from radio observations. Furthermore, these halos are sufficiently compact and dense to gravitationally capture field stars in satellite galaxies of the Milky Way, providing a natural explanation for the origin of Fornax 6, a stellar cluster in the Fornax dwarf spheroidal galaxy. Our results demonstrate that observations of halos with similar masses but residing in different cosmic environments offer a powerful and complementary probe of self-interacting dark matter.
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Instrumentation and Methods for Astrophysics

Using chromatic covariance to correct for scintillation noise in ground-based spectrophotometry

Jason E. Williams and Nicholas P. Konidaris

Atmospheric scintillation is one of the largest sources of error in ground-based spectrophotometry, reducing the precision of astrophysical signals extracted from the time-series of bright objects to that of much fainter objects. Relative to the fundamental Poisson noise, scintillation is not effectively reduced by observing with larger telescopes, and alternative solutions are needed to maximize the spectrophotometric precision of large telescopes. If the chromatic covariance of the scintillation is known, it can be used to reduce the scintillation noise in spectrophotometry. This paper derives analytical solutions for the chromatic covariance of stellar scintillation on a large telescope for a given atmospheric turbulence profile, wind speed, wind direction, and airmass at optical/near-infrared wavelengths. To demonstrate how scintillation noise is isolated, scintillation-limited exoplanet transit spectroscopy is simulated. Then, a procedure is developed to remove scintillation noise and produce Poisson-noise limited light curves. The efficacy and limits of this technique will be tested with on sky observations of a new, high spectrophotometric precision, low resolution spectrograph.
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Instrumentation and Methods for Astrophysics

Image reconstruction with the JWST Interferometer

Max Charles, Louis Desdoigts, Benjamin Pope et al. (+7 more)

Flying on board the James Webb Space Telescope (JWST) above Earth's turbulent atmosphere, the Aperture Masking Interferometer (AMI) on the NIRISS instrument is the highest-resolution infrared interferometer ever placed in space. However, its performance was found to be limited by non-linear detector systematics, particularly charge migration - or the Brighter-Fatter Effect. Conventional interferometric Fourier observables are degraded by non-linear transformations in the image plane, with the consequence that the inner working angle and contrast limits of AMI were seriously compromised. Building on the end-to-end differentiable model & calibration code amigo, we here present a regularised maximum-likelihood image reconstruction framework dorito which can deconvolve AMI images either in the image plane or from calibrated Fourier observables, achieving high angular resolution and contrast over a wider field of view than conventional interferometric limits. This modular code by default includes regularisation by maximum entropy, and total variation defined with $l_1$ or $l_2$ metrics. We present imaging results from dorito for three benchmark imaging datasets: the volcanoes of Jupiter's moon Io, the colliding-wind binary dust nebula WR 137 and the archetypal Seyfert 2 active galactic nucleus NGC 1068. In all three cases we recover images consistent with the literature at diffraction-limited resolutions. The performance, limitations, and future opportunities enabled by amigo for AMI imaging (and beyond) are discussed.
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All authors Max Charles, Louis Desdoigts, Benjamin Pope, Peter Tuthill, Dori Blakely, Doug Johnstone, Shrishmoy Ray, K. E. Saavik Ford, Barry McKernan, Anand Sivaramakrishnan

Instrumentation and Methods for Astrophysics

Slitless Spectroscopy Source Detection Using YOLO Deep Neural Network

Xiaohan Chen, Man I Lam, Yingying Zhou et al. (+6 more)

Slitless spectroscopy eliminates the need for slits, allowing light to pass directly through a prism or grism to generate a spectral dispersion image that encompasses all celestial objects within a specified area. This technique enables highly efficient spectral acquisition. However, when processing CSST slitless spectroscopy data, the unique design of its focal plane introduces a challenge: photometric and slitless spectroscopic images do not have a one-to-one correspondence. As a result, it becomes essential to first identify and count the sources in the slitless spectroscopic images before extracting spectra. To address this challenge, we employed the You Only Look Once (YOLO) object detection algorithm to develop a model for detecting targets in slitless spectroscopy images. This model was trained on 1,560 simulated CSST slitless spectroscopic images. These simulations were generated from the CSST Cycle 6 and Cycle 9 main survey data products, representing the Galactic and nearby galaxy regions and the high galactic latitude regions, respectively. On the validation set, the model achieved a precision of 88.6% and recall of 90.4% for spectral lines, and 87.0% and 80.8% for zeroth-order images. In testing, it maintained a detection rate >80% for targets brighter than 21 mag (medium-density regions) and 20 mag (low-density regions) in the Galactic and nearby galaxies regions, and >70% for targets brighter than 18 mag in high galactic latitude regions.
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All authors Xiaohan Chen, Man I Lam, Yingying Zhou, Hongrui Gu, Jinzhi Lai, Zhou Fan, Jing Li, Xin Zhang, Hao Tian

Sunday 12 October

Astrophysics of Galaxies

HI terminal velocity curves – Lessons learned from N-body/hydrodynamic `surrogate' models of the Milky Way

Hillary Davis, Thor Tepper-Garcia, Naomi McClure-Griffiths et al. (+2 more)

The development of an N-body/hydrodynamic `surrogate' model of the Milky Way (MW) - a model that resembles the MW in several key aspects after many Gyrs of evolution - would be extremely beneficial for Galactic Archaeology. Here we present four new `surrogate' models, all built with the Nexus framework. The simulations contain stars, dark matter and gas. Our most sophisticated model allows gas to evolve thermodynamically, and includes star formation, metal production, and stellar feedback. The other three models in this work have an isothermal gas disc. We examine these new simulations in the context of cold gas observations of the Galaxy. Our focus is the so-called `HI terminal velocity curve' - a heliocentric measurement of the maximum Vlos as a function of Galactic longitude, which dates back to the early days of radio astronomy. It is a powerful approach to indirectly estimating the gas dynamics because it does not require knowledge about the distance to individual gas clouds, which is difficult to estimate. A comparison of the terminal velocities and recovered rotation curve values in the simulations against observations suggests that our models are in need of further refinement. The gravitational torques associated with our synthetic bars are too strong, driving excessive streaming motion in the inner gas disc. This causes the simulated terminal velocity curves in the Galactic Quadrant I and IV to deviate substantially from each other, unlike what is seen in observed HI terminal velocities of the MW. We suggest possible ways forward for future models.
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All authors Hillary Davis, Thor Tepper-Garcia, Naomi McClure-Griffiths, Joss Bland-Hawthorn, Oscar Agertz

Earth and Planetary Astrophysics

Survival of satellites during the migration of a Hot Jupiter

Emeline Bolmont, Edward Galantay, Sergi Blanco-Cuaresma et al. (+2 more)

We investigate the origin and stability of extrasolar satellites orbiting close-in gas giants, focusing on whether these satellites can survive planetary migration within a protoplanetary disk. To address this question, we used Posidonius, an N-Body code with an integrated tidal model, which we expanded to account for the migration of a gas giant within a disk. Our simulations include tidal interactions between a $1M_\odot$ star and a $1M_{Jup}$ planet, as well as between the planet and its satellite, while neglecting tides raised by the star on the satellite. We adopt a standard equilibrium tide model for the satellite, planet, and star, and additionally explore the impact of dynamical tides in the convective regions of both the star and planet on satellite survival. We examine key parameters, including the initial satellite-planet distance, disk lifetime (proxy for the planet's final orbital distance), satellite mass, and satellite tidal dissipation. For simulations incorporating dynamical tides, we explore three different initial stellar rotation periods. We find that satellite survival is rare if the satellite has nonzero tidal dissipation. Survival is only possible for initial orbital distances of at least 0.6 times the Jupiter-Io separation and for planets orbiting beyond about 0.1 AU. Satellites that fail to survive are either 1) tidally disrupted, as they experience orbital decay and cross the Roche limit, or 2) dynamically disrupted, where eccentricity excitation drives their periastron within the Roche limit. Satellite survival is more likely for low tidal dissipation and higher satellite mass. Given that satellites around close-in planets appear unlikely to survive planetary migration, our findings suggest that if such satellites do exist, another process should be invoked. In that context, we also discuss the claim of the existence of a putative satellite around WASP-49 A b.
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All authors Emeline Bolmont, Edward Galantay, Sergi Blanco-Cuaresma, Apurva V. Oza, Christoph Mordasini

Astrophysics of Galaxies

Co-evolution of Nuclear Star Clusters and Massive Black Holes: Extreme Mass-Ratio Inspirals

Fupeng Zhang and Pau Amaro Seoane

We explore extreme mass-ratio inspirals (EMRIs) in the co-evolution of massive black holes (MBHs) and nuclear star clusters (NSCs), which host diverse stellar populations across a wide range of masses. The dynamics are simulated self-consistently with GNC, which we have updated to incorporate gravitational wave orbital decay, the loss cone of a spinning MBH, and stellar evolution. Over $12$ Gyr, we investigate the evolution of the NSC with a mass-growing MBH, as well as the EMRIs of stellar black holes, neutron stars, white dwarfs, brown dwarfs (BDs), and low-mass main-sequence stars (MSs), along with tidal disruption events (TDEs) involving MSs, BDs, and post-MSs. The mass growth of the MBH contributed by TDEs is typically $\sim 10^7\,M_{\odot}$, $\sim 10^6\,M_{\odot}$, and $\sim 5\times10^4\,M_{\odot}$ for massive, Milky-Way-like, and smaller NSCs, respectively. Between $40\%$ and $70\%$ of the stellar mass is lost during stellar evolution, which dominates the mass growth of the MBH if a significant fraction of the lost mass is accreted. The evolution of EMRI rates is generally affected by the cluster's size expansion or contraction, stellar population evolution, MBH mass growth, and the stellar initial mass function. The EMRI rates for compact objects peak at early epochs ($\lesssim 1$ Gyr) and then gradually decline over cosmic time. LISA-band ($0.1$ mHz) EMRIs involving compact objects around Milky-Way-like MBHs tend to have high eccentricities, while those around spinning MBHs preferentially occupy low-inclination (prograde) orbits. In contrast, MS- and BD-EMRIs usually have eccentricity and inclination distributions that are distinct from those of compact objects.
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Earth and Planetary Astrophysics

On the discovery of meteoritic mineral Zolenskyite; The artificial origin should not be overlooked

Boutros Pierre Embaid

Recently a new meteoritic mineral, Zolenskyite (Fe0.99Mn0.04Ca0.01Cr1.99S3.98), was discovered from the Indarch meteorite. Zolenskyite was structurally indexed as the monoclinic C2/m CrNb2Se4 - Cr3S4 type structure of synthetic FeCr2S4, with unit cell parameters a = 12.84(1) Å, b = 3.44(1) Å, c = 5.94(1) Å and e̱ta} = 117(1){\deg}. Zolenskyite was reported as high-pressure phase formed from Daubréelite at high pressures and temperatures in highly shocked regions of the EH parent asteroid. Although this discovery provides valuable information about the origin of meteoritic mineral assemblages, the results and conclusions raise controversies with those reported in previous articles where the synthetic FeCr2S4 was described. In this review, an alternative analysis of the supplementary X-ray data from Zolenskyite was made and yields to the monoclinic I2/m Cr3S4 type structure of synthetic FeCr2S4, with unit cell parameters a = 5.940 Å, b = 3.440 Å, c = 11.441 Å and e̱ta} = 90.55{\deg}, in agreement with previous results in the literature and differ from those reported above. Regarding the genesis of Zolenskyite and according to solid-state laboratory synthesis, the transformation of cubic FeCr2S4 phase (ideal composition of Daubréelite) to monoclinic FeCr2S4 (ideal composition of Zolenskyite) requires a process whose replication in Shock metamorphism stages is not well established and remains an open issue to address, together with another open issue related to the real composition of meteoritic minerals, with minor and trace metals, which is often overlooked when compared with synthetic ideal compositions. Whatever the results to be obtained by addressing the above open issues, they will shed more light on the genesis of Zolenskyite. In this context, it is worth to promote an open debate about the hypothesis of artificial origin.
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Instrumentation and Methods for Astrophysics

Dual Band Receiver Design for the Black Hole Explorer (BHEX) Mission

Cheukyu Edward Tong, Keara Carter, Paul Grimes et al. (+6 more)

A dual band receiver has been designed for the Black Hole Explorer (BHEX) mission, which is a space Very-Long Baseline Interferometry (VLBI) mission concept, aimed at unveiling the photon ring of black holes. The cryogenic receiver comprises a 228-320 GHz Superconductor-Insulator Superconductor (SIS) receiver, paired with a 76-106.7 GHz HEMT receiver. The details of the design are described in this talk. A novel comb generator, which will be used for delay tracking, has been designed and tested.
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All authors Cheukyu Edward Tong, Keara Carter, Paul Grimes, Eugene Lauria, Dan Marrone, Gabriella Montano, Matthew Morgan, Yoshirnori Uzawa, Lingzhen Zeng