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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 30 September

Instrumentation and Methods for Astrophysics

The Simons Observatory: Design and Initial Performance of the Detector Readout System for the Large-Aperture Telescope

Thomas P. Satterthwaite, Tristan Pinsonneault-Marotte, Shawn W. Henderson et al. (+34 more)

We present the design, implementation, and initial performance of a highly multiplexed cryogenic superconducting detector readout system in the context of its deployment to the Simons Observatory large-aperture telescope (LAT). The Simons Observatory is a cosmic microwave background experiment located at 5,200 m in Chile's Atacama Desert. In addition to its 6 m LAT, whose broad range of science goals spans probing large-scale structure to searching for new Solar System objects, the observatory also currently includes three 0.42 m small-aperture telescopes, which search for signatures of primordial gravitational waves. Nearly 100,000 optically-coupled transition-edge sensor bolometers have been deployed across the observatory's four telescopes to enable these science goals. The readout systems for these telescopes use microwave frequency multiplexing to simultaneously read out 860 optically-coupled bolometers per transmission line. This is enabled by the large-scale fabrication of multiplexing chips which house radio-frequency superconducting quantum interference devices for each detector, and the development of room-temperature electronics to read out these bolometers. This has enabled the largest deployment of superconducting sensors for astronomical observations to date. This paper focuses on the design and implementation of the readout system for the 63,000 detectors in the LAT's cryogenic receiver. We present performance results from an early phase in the telescope's operation. We show that the readout system's performance enables the instrument to meet key benchmarks, including successful readout of 81.4% of its optically-coupled bolometers, which exceeds projections, and readout noise-equivalent current consistent with pre-deployment specifications.
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All authors Thomas P. Satterthwaite, Tristan Pinsonneault-Marotte, Shawn W. Henderson, Zeeshan Ahmed, Kam Arnold, Declan Baker, Andrew Bazarko, Josh Borrow, Michael L. Brown, Mark Devlin, Simon Dicker, Peter N. Dow, Shannon M. Duff, Daniel Dutcher, John C. Groh, Saianeesh K. Haridas, Kathleen Harrington, Erin Healy, Johannes Hubmayr, Bradley R. Johnson, Brian Keating, Anna M. Kofman, Adrian T. Lee, Alex Manduca, Aashrita Mangu, Jenna E. Moore, Michael D. Niemack, Sandra O'Neill, John Orlowski-Scherer, Yudai Seino, Mufan Shao, Carlos Sierra, Max Silva-Feaver, Suzanne Staggs, Eve M. Vavagiakis, Yuhan Wang, Edward J. Wollack

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

Primordial Tensor Signatures and Gravitational Wave Constraints in Lorentz Violating Inflation with Non-Canonical Kinetics

Dibash Plaban Kalita and Shreya Banerjee

We investigate primordial tensor perturbations in a Lorentz violating inflationary framework with non-canonical scalar field dynamics. Using an Einstein-Æther type with a higher order kinetic term $K_3X^2$, we derive the tensor propagation speed and its dependence on an effective Lorentz violating coupling. We consider an analytically tractable potential free background and study two representative couplings, $q_k=\lambda_T\phi_k^2$ and $q_k=\lambda_T\phi_k^4$. The resulting tensor spectral index $n_T$ and its running $\alpha_T$ satisfy distinct consistency relations, providing potential signatures of Lorentz violation in the primordial gravitational wave spectrum. We derive corresponding constraints from the tensor tilt and running and compare them with the stringent late-time bound on the gravitational wave speed from GW170817/GRB170817A. We emphasize that translating this bound into primordial constraint requires an assumption about the evolution of tensor sector coupling between inflation and the late Universe. Our results demonstrate that primordial tensor observables can provide a complementary probe of Lorentz violation and its interplay with non-canonical inflationary dynamics.
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High Energy Astrophysical Phenomena

Improved Population and EOS Joint Inference for Binary Neutron Star Systems

Marc Ebiri and Richard O'Shaughnessy

The extreme environment within neutron stars presents the opportunity to probe the nuclear equation of state at high densities while studying the properties of these stellar remnants. Historically, the equation of state and neutron star mass distribution have been inferred separately, with the latter often simply assumed to be fixed in studies of the former, but the dependence of the equation of state on neutron star mass indicates they should be inferred together. In this work, we extend the generalized version of the popular RIFT algorithm known as Hyperpipe to interface with flexible, user-provided priors that will facilitate joint inference of equation of state and binary neutron star population hyperparameters. We demonstrate this framework's utility via application to a combination of several existing observations, particularly including massive galactic pulsars, double neutron star systems, millisecond X-ray pulsars, the gravitational wave event GW170817 and the nuclear symmetry energy, within the context of a widely-adopted parametric EOS family and a simple Gaussian population model. We recover parameters consistent with previous analyses of the EOS and binary neutron star population, finding the latter to fit a bivariate normal distribution with mean $(\mu_1,\mu_2) = (1.39,1.27) M_{\odot}$ and width $\sigma = 0.08 M_{\odot}$. Furthermore, we implement novel coordinate transformations in our pipeline, with which we have discovered that the ad hoc prior boundaries used for this EOS family may be too restrictive. We present results with relaxed yet still physical prior boundaries, noting vastly improved hyperparameter posteriors and modestly different equation of state inferences.
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Astrophysics of Galaxies

Stacked strong and weak lensing united: Improved measurement of the stellar and dark matter distributions in massive early-type galaxies at $z\sim 0.5$

Momoka Fujikawa and Masamune Oguri

We present a new measurement of the stellar and dark matter distributions in massive early-type galaxies at redshift $0.4<z<0.6$ by combining stacked strong and weak lensing measurements. The stacked weak lensing measurements down to the small radius of $0.013\,\mathrm{Mpc}/h$ enabled by the Subaru Telescope Hyper Suprime-Cam data are combined with stacked enclosed projected mass measurements from 13 strong lens systems. We find that adding strong lensing constraints improves constraints on the stellar and dark matter distributions. The central dark matter profile is found to be consistent with the standard Navarro-Frenk-White density profile. The stellar initial mass function is found to be bottom-heavy. The total density profile in the inner region is described well by the power-law density profile with the slope of $-1.96\pm 0.07$, which can also explain weak lensing signals out to $1\,\mathrm{Mpc}/h$ reasonably well. The stacked weak lensing profile constrains an internal mass-sheet transformation parameter to $\lambda_{\mathrm{c}}=0.978\pm0.010$. Our analysis demonstrates that the combination of the stacked strong and weak lensing serves as a powerful tool for studying central density profiles of galaxies.
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Cosmology and Nongalactic Astrophysics

Metastable Dark Energy on the Phantom Brane

Purba Mukherjee, Arman Shafieloo, Varun Sahni et al. (+1 more)

Recent DESI observations hint at a preference for dynamical dark energy with an equation of state (EoS) that crosses the phantom divide at $w=-1$. In this work, we investigate metastable dark energy (DE) on the minimal phantom brane. Braneworld effects lead to $w < -1$ at early times, whereas metastable decay of DE results in $w > -1$ at late times. We consider three metastable decay prescriptions on the phantom brane: an exponentially decaying DE component (M1), decay of DE into non-baryonic dark matter (M2), and decay into dark radiation (M3). Using CMB observations, DESI DR2 BAO measurements, and the DES-Dovekie Type Ia supernova sample, we compare these models with $\Lambda$CDM, the Chevallier–Polarski–Linder (CPL) parametrization, and the minimal phantom-brane model with a non-decaying $\Lambda$. We find that metastable models on the brane are preferred over $\Lambda$CDM, their decay rates being $\Gamma/H_0=0.362\pm0.086$, $0.539\pm0.125$, and $0.483\pm0.112$ for M1, M2, and M3, respectively. Best fits of metastable models improve over $\Lambda$CDM by $\Delta\chi^2_{\rm MAP}=-17.14$, $-18.76$, and $-18.22$, while the corresponding $\Delta{\rm DIC}$ values are $-8.66$, $-9.63$, and $-6.56$. Braneworld screening drives effective phantom behaviour at $z\gtrsim0.4$, while DE decay drives the EoS toward non-phantom values closer to the present epoch, with the phantom divide $w=-1$ being crossed at $z \simeq 0.3$–$0.4$. These results show that the interplay between metastable decay and phantom-brane screening provides a simple physical mechanism for an effective crossing of the phantom divide consistent with DESI observations.
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All authors Purba Mukherjee, Arman Shafieloo, Varun Sahni, Yuri Shtanov

Astrophysics of Galaxies

The "Fork" Geometry in the DESI Main Survey DR1: Implications of Target Selection for Galaxy Evolution Studies

A. Nigoche-Netro, P. Lagos, R. J. Diaz et al. (+3 more)

The Dark Energy Spectroscopic Instrument (DESI) Main Survey Data Release 1 (DR1) provides an unprecedented spectroscopic view of galaxies and quasars across a large fraction of the observable Universe. However, the survey's tracer-dependent targeting strategy introduces complex observational selection effects that strongly influence the apparent distribution of galaxies in the redshift-luminosity plane. In this work, we investigate the origin of the characteristic "fork" geometry observed in DESI DR1 and show that the observed distribution is consistent with an interpretation in which it arises from the combined action of intrinsic galaxy bimodality and the survey's redshift-dependent selection function. We show that the observed underdensity separating the dominant galaxy populations is influenced not only by the physical Green Valley but also by survey selection effects, since it is further shaped by magnitude limits, surface-brightness selection, and structural incompleteness. Using DESI DR1 spectroscopy together with Legacy Survey photometry, we analyze the roles of the BGS, LRG, ELG, and QSO target classes in producing the observed distribution and assess their impact on luminosity-function measurements. Our results indicate that both target selection and observational biases significantly affect the observed galaxy distribution and the evolutionary trends inferred from it. We summarize practical observational considerations aimed at minimizing these effects and enabling more robust studies of galaxy evolution with DESI.
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All authors A. Nigoche-Netro, P. Lagos, R. J. Diaz, E. García-Manzanárez, J. A. Quezada-Pérez, R. Ibarra-Nuño

Astrophysics of Galaxies

The impact of the turbulent Mach number on star formation and the initial mass function

Sajay Sunny Mathew, Christoph Federrath and Amit Seta

Turbulence regulates star formation by influencing the density structure and fragmentation of molecular clouds, and therefore it is expected to play a key role in setting the initial mass function (IMF). We study how the strength of the turbulent shocks affects star formation and the IMF by comparing a series of magnetohydrodynamical (MHD) simulations of star cluster formation in clouds with three different rms Mach number values, $M=2.5, 5$, and $10$, but otherwise the same Alfvén Mach number ($M_\mathrm{A}\sim3$) and virial parameter ($\alpha_\mathrm{vir}\sim0.5$). All three simulations include stellar feedback in the form of protostellar jets/outflows and accretion heating. We find that the star formation rate per freefall time ($\mathrm{SFR_{ff}}$) for the $M=10$ model is higher by a factor of $\sim3$ compared to the $M=2.5$ and $5$ cases, which have similar $\mathrm{SFR_{ff}}$. In terms of the IMF, the $M=5$ and $10$ models produce almost similar distributions, resembling typical observed IMFs. The $M=2.5$ model, on the other hand, produces a bimodal IMF with a primary peak at supersolar masses ($\sim 2\, \mathrm{M_\odot}$) and a secondary peak in the substellar regime ($< 0.1\, \mathrm{M_\odot}$). The $M=2.5$ and $5$ simulations producing significantly different IMFs while having similar $\mathrm{SFR_{ff}}$, suggest that a distinct set of physical processes governs the SFR and IMF. Through a resolution study for the $M=2.5$ case, we find our base models have reached near numerical convergence, potentially only slightly underestimating close-binary formation. We also see signatures of bimodality in the $M=2.5$ model for the multiplicity fraction and stellar angular momentum distribution.
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Earth and Planetary Astrophysics

Planetesimal Formation under Realistic Gas Dynamics: Dust Concentration in Turbulent and Windy Protoplanetary Disks

Pinghui Huang and Xue-Ning Bai

Planetesimals are a key intermediate stage of planet formation and originate from dust concentration in protoplanetary disks, which is strongly regulated by gas dynamics. In this study, we use the multifluid dust module of Athena++ to investigate dust concentration in 2D axisymmetric global non-ideal MHD (ambipolar diffusion, AD) simulations of outer disks. Our simulations simultaneously launch large-scale MHD disk winds and resolve both streaming instability (SI) and vertical shear instability (VSI). We systematically explore the effects of magnetic field strength, cooling timescale, ambipolar Elsasser number, and dust size on dust concentration. We find that strong dust clumping persists across a broad range of magnetized and wind-launching disk conditions. MHD winds also enhance dust clumping by modifying background conditions in the following ways: (1) secular gas depletion by MHD wind mass loss, and (2) dust trapping in zonal flows as a result of magnetic flux concentration (which occurs in more strongly magnetized cases). Overall, our results demonstrate that strong dust clumping can persist in global magnetized disks with AD and large-scale MHD winds, leading to conditions favorable for planetesimal formation.
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Instrumentation and Methods for Astrophysics

MATCH: Performance Characterization and Scientific Observations of the Wuhan University 1-m Optical Telescope

Sai-En Xu, Bei You, Han He et al. (+22 more)

The Multi-mode Autonomous Terminal for Compatible Hybrid-optics (MATCH), operated by Wuhan University and located at Lenghu, is a 1-m Ritchey–Chrétien telescope equipped with imaging and spectroscopic instruments. MATCH has been in trial operation since October 2025. In this work, we present the telescope and instrument configuration, characterize its performance during the first year of operation, and describe the integrated observing workflow developed for routine and time-domain observations, including the observatory control system, observation scheduler, and automated data reduction pipelines. Under typical observing conditions, the imaging system reaches 60-s-equivalent $5\sigma$ limiting magnitudes of approximately 18–20 mag across the $ugri$ bands, while the spectroscopic system reaches approximately 15–16~mag in the B and G channels in a 30-minute integration at the effective spectral resolution of the instrument. In the best-quality imaging observations, the $g$- and $r$-band depths approach 21~mag. Together with flexible scheduling and Target-of-Opportunity capability, MATCH provides photometric and spectroscopic follow-up and long-term monitoring of transient and variable sources.
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All authors Sai-En Xu, Bei You, Han He, Shuai-Kang Yang, Xiao Fan, Yi-Fei Qu, Rui-Xiang Hu, Hui-Bo Fei, Bo-An Chen, Zong-Hong Zhu, Zheng-Yang Li, Xiao-Yan Li, Zi-Jian Han, Jia-Nan Cong, Chao Chen, Jia-Li Chen, Kai-Wen Zheng, Yi-Qiao Yang, Qing-Shan Li, Zhen-Guang Sun, Tong Zhou, Kai Zhang, Jiajia Wu, Xuhang Yin, Liang Yuan

High Energy Astrophysical Phenomena

Pulsar glitches triggered by quakes when stress reaches a threshold

Zixuan Zhou, Ruipeng Lu, Weiyang Wang et al. (+2 more)

The starquake model of pulsar glitches is revisited in light of accumulated observational data. A statistical comparison between the time-predictable and the magnitude-predictable models, borrowed from seismology and grounded in the classical spring-slider framework, is performed against a sample of 245 glitch events from 9 pulsars. It is found that the data supports the time-predictable model, i.e., a quake resulting in a glitch could be triggered when the developed stress reaches a critical threshold, $\tau_{\rm c}$, while the remaining elastic energy (correspondingly the residual stress, $\tau_{\rm r}$) after quakes is not fixed. The critical stress could be the order of $\tau_{\rm c}\simeq (10^{34}-10^{35})\ {\rm dyn\,cm^{-2}}$ if the residual stress after a quake with maximum stress drops could be considered negligible (i.e., $\tau_{\rm r}\simeq 0$), to explain the glitch amplitudes and the intervals. This $\tau_{\rm c}$-value is the order of the shear modulus of strangeon stars, but would be several orders higher than that of conventional neutron stars.
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All authors Zixuan Zhou, Ruipeng Lu, Weiyang Wang, Han Yue, Renxin Xu

Solar and Stellar Astrophysics

Magnetic field diagnostics of a solar active region filament

Daiki Yamasaki, Yu Wei Huang, Yuki Hashimoto et al. (+2 more)

We performed spectropolarimetric observations of an active region filament in He I 10830 angstrom and Si I 10827 angstrom lines to investigate its magnetic field structure. We carried out full-Stokes inversions with the HAZEL code, which takes into account the Zeeman and Hanle effects. As a result, we yielded a mean field strength of 101 $\pm$ 33 G and a horizontal field nearly parallel to the filament axis, such that the distinction between the two classical normal- and reverse-polarity models becomes physically insignificant. In addition, we found Zeeman-like signatures in the linear polarization, characterized by double-peaked symmetric profiles, in some pixels of our observations. Since these profiles could not be well reproduced by modeling that included both the Zeeman and Hanle effects, we performed inversions assuming only the Zeeman effect. The inversion yielded a strong magnetic field of approximately 500 G. However, simultaneous observations of Si I 10827 angstrom indicate a photospheric magnetic field weaker than 100 G. Therefore, the scenario proposed by Diaz Baso et al. (2016), in which the strong field inferred from He I 10830 angstrom originates from contamination by the underlying photosphere, does not apply to our filament. The Zeeman-like profiles are preferentially found in optically thick regions ($\tau$ ~ 1.4-2.5), where the simplifying assumptions adopted in HAZEL are expected to become less reliable. Our results suggest that these profiles reveal limitations of the current inversion framework in optically thick regions and motivate future radiative-transfer modeling incorporating self-consistent radiation fields, differential illumination of the multiplet components, and possibly partial frequency redistribution.
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All authors Daiki Yamasaki, Yu Wei Huang, Yuki Hashimoto, Satoru UeNo, Kiyoshi Ichimoto

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

Kilopixel Performance of the Kinetic Inductance Detectors for the Terahertz Intensity Mapper

Justin S. Bracks, Reinier M. J. Janssen, Steve Hailey-Dunsheath et al. (+32 more)

We characterize a flight-grade array of lumped-element kinetic inductance detectors (LEKIDs) developed for the long-wavelength module of the Terahertz Intensity Mapper (TIM). From an 864-pixel science array, we select 490 well-isolated resonators spanning the focal plane and readout band and measure their thermal response, optical responsivity, and noise using a ZCU111-based multitone readout system intended for flight. The thermal and optical response of the detector population is consistent with previous single-pixel measurements and can be described by Mattis-Bardeen theory under the influence of a change in Cooper pair or quasi-particle density. Under increasing blackbody loading, the measured noise transitions from a thermal generation-recombination-dominated floor to photon-noise-limited scaling, with the majority of detectors achieving photon-noise-limited operation by approximately 400 fW incident power, with a median detector noise-limited NEP of $NEP_{det} = 1.1\times10^{-17} W \sqrt{Hz}$. The measured photon-noise scaling implies a median optical efficiency of approximately 0.67, indicating additional unknown loss sources between the detectors and blackbody radiator, tentatively attributed to losses in the waveguide. These results demonstrate that the TIM LEKID architecture retains the required sensitivity when scaled to kilopixel-class arrays; the principal remaining challenges are array-level tone optimization, resonator tracking, and identification of frequency-domain collisions.
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All authors Justin S. Bracks, Reinier M. J. Janssen, Steve Hailey-Dunsheath, Talia Saeid, Bruce Bumble, Logan Foote, Elijah Kane, Lun-Jun Liu, Charles M. Bradford, Shubh Agrawal, James E. Aguirre, Hrushi Athreya, Brockton S. Brendal, Karia Dibert, Peter Dow, Jeffrey P. Filippini, Jianyang Fu, Karolina G. Garcia, Christopher E. Groppi, Bradley Johnson, Dylan Joralmon, Wooseok Kang, Garrett K. Keating, Ryan P. Keenan, Ian N. Lowe, Alex Manduca, Aashrita Mangu, Daniel P. Marrone, Philip D. Mauskopf, Evan C. Mayer, Sydnee ODonnell, Simon Tartakovsky, Mathilde Van Cuyck, Joaquin D. Vieira, Jessica A. Zebrowski

High Energy Astrophysical Phenomena

HLX-1 as a Repeating Partial Tidal Disruption Event around an Intermediate-Mass Black Hole

Fangyuan Yu, Andrew Mummery and Muryel Guolo

ESO 243$-$49 HLX–1 is one of the first known compelling intermediate-mass black hole (IMBH) candidates, but the origin of its recurrent X-ray outbursts remains unsettled. In this work we fit the HLX–1 outbursts simultaneously with a relativistic thin-disk time-dependent model. The black-hole and disk-geometry parameters are tied across epochs, while the injected mass and timing parameters are fitted separately for each outburst. We also include a contemporaneous HST UV/optical/IR spectral energy distribution obtained near the peak of one outburst, which constrains the global temperature and radius scales of the disk. The soft-state data are consistent with a common global solution, with black hole mass $\log_{10}(M_{\bullet}/M_\odot)=4.5\pm0.2$ and disk formation radius $\log_{10}(r_0/r_g)=3.8\pm0.3$. The differences between outbursts are mainly described by modest changes in disk mass and viscous timescales. The inferred injected masses are typically $\sim 10^{-3}\,M_\odot$ per outburst, requiring a total fuel supply of at least a few $\times 10^{-3}\,M_\odot$ across the observed sequence. This mass scale, and the disk size, are consistent with repeated partial stripping of a low-mass donor. A simple Keplerian mapping of the flare gaps and fitted disk radius implies a highly eccentric orbit with a pericenter just outside the donor's tidal radius. These results support a repeating partial tidal disruption interpretation for the origin of HLX–1.
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High Energy Astrophysical Phenomena

New Constraints on $r$-process Nucleosynthesis in Neutron Star Mergers from GW170817 Late-Phase Spectra

Salma Rahmouni, Masaomi Tanaka, Daiji Kato et al. (+2 more)

The neutron star merger event GW170817 provided the first direct evidence of $r$-process nucleosynthesis. Observed spectra of its electromagnetic counterpart AT2017gfo exhibited several features that encode information on the nature and abundance of the synthesized $r$-process elements. In this study, we investigate the late nebular-phase spectral features of AT2017gfo, which provide important probes of the elemental abundance of the ejecta. We construct an analytic spectral model that computes emission features produced by the radiative decay of collisionally excited ions through allowed and forbidden transitions. By comparing our model to AT2017gfo, we identify La III and Ce III as the main contributors to the emission features at $1.4\,\mu{\rm m}$ and $1.6\,\mu{\rm m}$, respectively. We also confirm Te III as the dominant contributor to the $2.1\,\mu{\rm m}$ feature proposed in previous works. We infer mass fractions of $X({\rm La})\approx 0.025-0.05$, $X({\rm Ce})\approx 0.05-0.1$, and $X({\rm Te})\approx 0.04-0.08$, although the La and Ce abundance estimates remain tentative due to uncertainties in the radiation field. From the non-detections of Kr and Sb lines, we derive upper limits of $X({\rm Kr})\lesssim 0.03$ and $X({\rm Sb})\lesssim 0.003$. These results suggest that nucleosynthesis in the inner ejecta of GW170817 produced a suppressed first $r$-process peak and an enhanced heavy-element abundance compared to the solar $r$-process pattern, with an estimated lanthanide fraction of $X_{\rm LN}\approx (3-6) \times 10^{-2}$. Our conclusions are consistent with the apparent universality of heavy $r$-process elements and the lanthanide fraction inferred from observations of $r$-enhanced metal-poor stars.
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All authors Salma Rahmouni, Masaomi Tanaka, Daiji Kato, Gediminas Gaigalas, Kenta Hotokezaka

Tuesday 29 September

Earth and Planetary Astrophysics

A Probabilistic Trajectory and Dispersion Study of Martian Tumbleweed Rover Swarms in Global Dust Storm Conditions

Emma-Catherine Belhadfa and Gabriele MT D'Eleuterio

Global Dust Storms (GDSs) dominate the Martian climate, yet the mechanisms of dust lifting, transport, and deposition remain poorly constrained because in situ observations are limited: landers are stationary, and their Radioisotope Thermoelectric Generators (RTGs) contaminate local measurements. Our solution is a swarm of lightweight, wind-propelled spherical rovers – Dust Rovers (DRs) – that follow natural wind patterns to collect high-spatial-resolution in situ dust data during storms. Here, we quantify the dispersion and communication connectivity of this robotic architecture. Using 625 wind states calculated using the Mars Climate Database (MCD) for the MY34 storm at the Curiosity site, we build a bivariate-normal model of the near-surface wind velocity and characterise its diurnal structure. Rover trajectories and swarm dispersion are propagated with three integrators: the Euler and fourth-order Runge-Kutta schemes for the deterministic dynamics, and a stochastic Ornstein-Uhlenbeck formulation that simulates turbulent gust forcing. Dispersion is controlled by the unmeasured gust correlation time: with a static rolling threshold enforced, the white-gust case (tau_g = Delta t = 1 s) provides a two-rover separation below 1 m over an hour (0.44 km over a sol), whereas correlation times of 10-60 s yield 6-25 m over an hour (1.4-3.3 km over a sol). We demonstrate that a 20-rover swarm needs only a 1.6-4.1 km per-rover range to remain connected over a sol, and stays connected across the plausible envelope – for gust amplitudes up to twice the nominal value with tau_g <= 60 s, and at the nominal amplitude up to tau_g ~ 150 s.
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High Energy Astrophysical Phenomena

Chandra X-ray Spectral Evidence of the Dual AGN Nature of the Gravitational lens MG B2016+112 at z=3.273 with 175 pc separation

Daniel A. Schwartz, Julia M. Sisk-Reynes and Anna Barnacka

We use a new 175 ks Chandra X-ray observation of the z=3.273 radio-loud gravitational lens system MG B2016+112 to present definitive X-ray spectral evidence that it contains a dual active galactic nucleus (AGN). With a projected separation of 175 parsecs, this is the tightest separation confirmed AGN pair at high redshift. Prior multi-epoch very long baseline interferometry (VLBI) and archival Chandra data had revealed two distinct emitters, but could not rule out a single AGN with a complex, highly magnified jet. Our new Chandra observations allow a separate spectral analysis of each source. We find strong intrinsic absorption (N_H > 4 x 10^22 cm^-2, 3 sigma confidence) at the source redshift for the highly magnified source inside the caustic. This identifies it as an obscured AGN. In addition to the previously known type II AGN outside the caustic, this confirms a compact dual AGN system in MG B2016+112. On-going and future surveys using facilities such as Euclid, SKA, and the Rubin and Roman observatories will uncover more such systems, probing SMBH evolution and gravitational wave precursors.
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Solar and Stellar Astrophysics

Sunrise III/SUSI reveals extended and spectrally structured Ca II K emission above the solar limb

Ivan Milić, Christopher M. J. Osborne, Francisco A. Iglesias et al. (+32 more)

The Sunrise III/SUSI instrument performed a sit-and-stare observation of the off-limb emission in the Ca II K line core, with a combination of excellent temporal and spectral resolution. The emission reaches up to 6 Mm above the solar limb, indicating the existence of off-limb structures akin to spicules. In this letter, we describe the spatio-spectral properties of the observed emission, focusing on the spectral line shape resolved in detail by Sunrise III/SUSI, and compare the observation with simple modeling that relies on a numerical simulation of the solar chromosphere. We find that the simulation contains enough cool and dense material at Mm heights to produce off-limb emission, but that the spectral width of these features is slightly lower than observed, necessitating more detailed modeling.
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All authors Ivan Milić, Christopher M. J. Osborne, Francisco A. Iglesias, Juan Sebastián Castellanos Durán, Damien F. Przybylski, Lakshmi Pradeep Chitta, Sanghita Chandra, Andreas Lagg, Sami K. Solanki, Tino L. Riethmüller, Achim Gandorfer, Alex Feller, Johannes Hoelken, H. N. Smitha, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alberto Álvarez-Herrero, Masahito Kubo, Valentín Martínez Pillet, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Hanna Strecker, Azaymi L. Siu-Tapia, Pablo Santamarina Guerrero, Julian Blanco Rodríguez, Yusuke Kawabata, Takuma Matsumoto, Ryohtaroh T. Ishikawa, Edvarda Harnes, Takayoshi Oba, Dušan Vukadinović

High Energy Astrophysical Phenomena

Angular structure of finite-field vacuum birefringence in magnetars

Shahram Abbassi and S. R. Valluri

Vacuum birefringence in a strong magnetic field is often modelled by combining the finite-field splitting for perpendicular propagation with the familiar $\sin^2\theta$ angular factor. That separation is exact only at leading response order. Continuing our previous study of the field-strength dependence of the birefringence, we examine the angular dependence of the full one-loop refractive indices in the local Heisenberg–Euler theory. We show analytically that, on the positive-birefringence branch, the usual factorized form systematically overestimates the exact splitting away from perpendicular propagation. The relative correction is largest close to the magnetic-field direction, where the absolute birefringence itself vanishes. Compact analytic expansions expose the sign, scaling, and angular location of the correction throughout the magnetar-relevant range $B/B_{\rm cr}\le100$, while an independent proper-time calculation verifies the underlying one-loop coefficients. In centred-dipole applications the correction is sub-percent for moderate magnetar fields but reaches several percent for the strongest sources; surface averaging and radial phase accumulation reduce its physical weight as the field decreases away from the stellar surface. The result separates finite-field amplitude and angular corrections and provides controlled analytic benchmarks for precision polarization transport in strongly magnetized environments.
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Earth and Planetary Astrophysics

aRieL - Reinforcement Learning for the Ariel Space Telescope Scheduling

James Kostas Ray, Kai Hou Yip, Alexandra Thompson et al. (+2 more)

The Ariel mission will conduct a population level survey of hundreds of exoplanet atmospheres, requiring observations to be scheduled across a large and diverse catalogue of potential targets. By framing Ariel scheduling as a long-horizon optimisation problem in which individual decisions affect both mission time and the scientific opportunities available later in the survey, Reinforcement Learning (RL) can be utilised as a framework for target selection. We introduce aRieL, a simulated observing environment coupled to a Set Transformer Proximal Policy Optimisation (PPO) agent that is trained to generate a scheduling policy. The RL policy consistently finds a strong compromise between competing survey objectives, producing large Tier~1 samples while maintaining high Tier~3 completion, population coverage, and observing efficiency when compared to a set of baseline heuristic polices. This behaviour is retained when the candidate catalogue is substantially expanded, while modifications to the reward function produce corresponding changes in the learned observing strategy. We further show that a policy trained on the baseline mission scenario can generalise without retraining to a modified scenario requiring repeated Tier~3 observations, revealing the resulting trade-off with the wider survey. These results demonstrate that reinforcement learning provides a flexible approach to large-scale astronomical scheduling, in which the observing strategy can respond directly to changes in mission state and to the scientific priorities, and motivate its wider exploration for observatories with similarly complex, state dependent scheduling problems.
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All authors James Kostas Ray, Kai Hou Yip, Alexandra Thompson, Luís F. Simões, Nikolaos Nikolaou

High Energy Astrophysical Phenomena

Nonthermal hotspot orbiting the supermassive black hole Sgr A*

Alejandro Cruz-Osorio, David Barrero-González, Juan J. Zaldívar et al. (+1 more)

Recent millimeter wavelength observations at 230 GHz by the Event Horizon Telescope have resolved the innermost structure of the Galactic Center, Sgr A*, revealing a ring-like structure consistent with synchrotron emission from a magnetized torus surrounding a supermassive black hole. These observations reveal two key features: three prominent hotspots near the photon ring and low light-curve variability, with a modulation index of $\bar{\sigma}/\bar{\mu} \lesssim 0.1$. State-of-the-art general relativistic magnetohydrodynamic and radiative transfer simulations cannot simultaneously reproduce the three hotspots and low light-curve variability observed in Sgr A*. We propose that an orbiting hot blob, formed in the accretion disk, could account for hotspots. We systematically explore its physical properties, including size, emission amplitude, orbital radius, eccentricity, velocity, and orbital plane orientation. The results – applying two observational constraints–show that the preferred model corresponds to a black hole with dimensionless spin $a_{\star}=0.5$, a magnetically arrested disk configuration for the magnetic field, and the presence of a hotspot with size $\sigma_{\rm hs}=2\,M$ and intensity amplitude $A=10$, orbiting circularly at $r_{\rm orb}=6 M$ with Keplerian velocity in the black holes equatorial plane, and an inclination view angle of $i^\circ=20$.
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All authors Alejandro Cruz-Osorio, David Barrero-González, Juan J. Zaldívar, Yosuke Mizuno

Astrophysics of Galaxies

A triple-induced merger in T Ori C, solves the proplyd lifetime problem and the curiously young shell of M42

Maite Wilhelm, Alessandro Alberto Trani and Simon Portegies Zwart

There has long been a tension between the stellar ages in the Orion Nebula Cluster and the rapid external photoevaporation of its protoplanetary discs. Recently, the shell of the Orion Nebula has similarly been found to be dynamically younger than the stars. We propose a new scenario to resolve both age problems. In our scenario the ONC's most massive star, $\theta^1$~Ori~C1, formed from the merger between two binary stars induced by vZLK oscillations due to the present-day binary companion $\theta^1$~Ori~C2. This merger, happening between the last episode of star formation and today, resulted in an increased luminosity, leading to stronger external photoevaporation and accelerated expansion of the shell. {We use Monte Carlo simulations to explore both whether a sudden brightening of $\theta^1$~Ori~C1 could reconcile the stellar ages and shell expansion, and whether triple progenitors to $\theta^1$~Ori~C\, could result in stellar mergers on the relevant timescale. A sudden brightening of $\theta^1$~Ori~C1 a few hundred thousand years ago can reproduce today's shell while maintaining a system age close to the stellar age. However, the required increase in stellar wind luminosity is greater than a simple merger can explain. At lower luminosity, the mixing of a relatively greater amount of cool photoevaporative wind material into the hot bubble could result in the required increase, and we identify a lower limit on the required strength of this effect. Additionally, we find that progenitor triples merge readily, on timescales even shorter than the scenario would require. These mergers could be deferred by increased pre-main sequence tidal effects, rotation, and perturbing encounters with other cluster members. Our proposed scenario with a merger driven by von Zeipel-Lidov-Kozai evolution solves two problems; the Orion Nebula's proplyd problem and the shell lifetime problems.
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Earth and Planetary Astrophysics

Modeling of the Yarkovsky effect. I. Thermal dependence

O. Golubov, O. Mikhalchenko, V. Lipatova et al. (+1 more)

We investigate how the Yarkovsky effect created by one flat surface element on the asteroid depends on the thermal parameter. Then we integrate the Yarkovsky force over the surface of a spherical asteroid. In the next articles of the series, we will investigate the Yarkovsky force for bodies of more complicated shape and compute the change of the asteroid's orbit. Using perturbation theory, we analytically solve the one-dimensional heat conduction equation under the surface element and use the solution to analytically compute the Yarkovsky effect in the limiting cases of big and small thermal parameters. Then we analytically sew the two solutions to obtain an approximate expression for the Yarkovsky effect valid for both large and small thermal parameters. We verify it by comparing it to the results of the numerical solution of the heat conduction equation. Finally, we fit the parameters in an approximate analytical expression to improve the agreement with the numerical results. We obtain a fully analytical expression for the Yarkovsky effect of one surface element, which is composed of 4 terms and is precise for any value of the thermal parameter up to the accuracy of 15%. We also propose a fitted expression of the same form, which is precise up to 0.15%. They both much supersede the traditionally used 3-parameter fit, which produces an error up to 50% and, in particular, is about a factor of 2 wrong for small values of thermal parameters. Finally, we apply the new formalism to evaluate an analytical expression for the Yarkovsky force acting on a spherical asteroid, ending up in a 0.1%-accurate fitted expression for an asteroid with 0 obliquity on a circular orbit and a less accurate expression for the general case.
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All authors O. Golubov, O. Mikhalchenko, V. Lipatova, D. J. Scheeres

High Energy Astrophysical Phenomena

Relativistic Spherical Accretion in Nonrotating Black Hole Spacetimes: Astrophysical Implications

David Barrero-González and Alejandro Cruz-Osorio

We present a systematic analysis of spherically symmetric accretion flows onto thirteen non-rotating black hole spacetimes, including charged and regular black holes, scalar and dilaton fields, dark energy, cosmological constants, modified gravity, and parametrized metrics. We generalize the Michel solution to arbitrary diagonal spacetimes and investigate the density, temperature, velocity, Mach number, mass accretion rate, and bremsstrahlung luminosity equilibrium profiles. Using the Schwarzschild solution as a reference, we find significant deviations in the accretion flow, with cosmological-constant and dark-energy models strongly suppressing accretion, while regular and Yukawa-like spacetimes generally enhance it. We provide fitting formulas for the accretion rates and luminosities as functions of the spacetime parameters. We then explore two astrophysical applications: accretion onto supermassive black holes, such as Sgr A* and M87*, and the inferred progenitor masses of the intermediate-mass black holes associated with the GW190521 gravitational wave event. We find that observational uncertainties may allow us to probe signatures of deviations from the Schwarzschild spacetime.
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Earth and Planetary Astrophysics

Migration and Evolution of giant ExoPlanets (MEEP). III. Twenty-Nine Giant Planets from the TESS Mission

Jack Schulte, Joseph E. Rodriguez, David W. Latham et al. (+97 more)

We present the discovery and characterization of 29 hot and warm Jupiter systems transiting bright ($G < 12.8$) FGK stars using TESS data and ground-based photometry and spectroscopy. Through the use of high angular resolution imaging, we discovered three bound stellar companions, named TOI-3988 B, TOI-6171 B, and TOI-7266 B. The planets that we confirmed span an orbital period range of $1.28 - 16.9$ days, a mass range of $0.35 - 8.7$ $\mathrm{M}_{\mathrm{J}}$, and an orbital eccentricity range of $0 - 0.6$, and add to the growing self-consistent sample of hot and warm Jupiter systems detected using TESS and analyzed using the Markov-Chain Monte Carlo code EXOFASTv2. By performing two-sample Kolmogorov-Smirnov tests on a set of host star and planetary parameters, we find that this growing self-consistent sample of giant planets has a different distribution of host star masses, surface gravities, and metallicities, compared to the hot Jupiter and warm Jupiter systems in the literature, likely due to the additional constraint on the host star density from the planetary transits included in our global fits. We find that seven of the 29 newly confirmed planets have significant orbital eccentricity, and that one of these, TOI-3365 b, is in a system which likely hosts a massive outer companion. The continued confirmation of hot Jupiter and warm Jupiter systems and the follow-up RV monitoring on these systems to identify outer companions will pave the way for important investigations of giant planet migration.
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All authors Jack Schulte, Joseph E. Rodriguez, David W. Latham, Allyson Bieryla, Karen A. Collins, Samuel N. Quinn, Xian-Yu Wang, Rafael Brahm, Abdullah Al-Haji, Robert Aloisi, Caitlyn Altermatt, Nikola Antonov, David Baker, Pavel Balanutsa, Khalid Barkaoui, Özgür Baştürk, Slawomir Bednarz, Paul Benni, Krzysztof Bernacki, Mario Billiani, Ventsislav Bodakov, Pau Bosch-Cabot, Valerio Bozza, Ahmet Cem Kutluay, David R. Ciardi, Catherine A. Clark, Jerome de Leon, Jason D. Eastman, İpek Aleyna Ertürk, Thomas M. Esposito, Phil Evans, Miranda Felsmann, Raquel Forés-Toribio, Isaac Fournier, Akihiko Fukui, Tianjun Gan, Cristilyn Gardner-Watkins, Purvi Garg, Eric Girardin, Tateki Goto, Ferran Grau Horta, Thomas Henning, Eric G. Hintz, Keith Horne, Kai Ikuta, Jon M. Jenkins, Andrés Jordán, Jenson Keen, Adam Kraus, Valentina Kuzmina, Artem Kuznetsov, Adam Lark, Rodrigo Leiva, Vladimir Lipunov, Michael B. Lund, Franck Marchis, Joshua Margherone, Robert Massey, Kim McLeod, Edward Michaels, Mayuko Mori, J. A. Muñoz, Felipe Murgas, Norio Narita, Takaya Okada, Shane Painter, Enric Palle, Ivan Panchenko, Hannu Parviainen, Anastasiia Pechko, Adam Popowicz, Don Radford, Fabian Rodriguez Frustaglia, Sylvain Roux, Subhroja Roy, Matthew Ryno, Gülben Şanc{\i}, Richard P. Schwarz, Victor Senik, Lauren A. Sgro, Avi Shporer, Gregor Srdoc, Denise Stephens, Chris Stockdale, Ashley Stone, Ivan Strakhov, Marcelo Tala Pinto, Thiam-Guan Tan, Suzanne Taylor, Neil Thomas, Nataly Tiurina, Julian C. van Eyken, Songhu Wang, Noriharu Watanabe, Levi R. Webb, Francis P. Wilkin, Joe Williams, Selçuk Yalç{\i}nkaya, Mesut Y{\i}lmaz, Carl Ziegler

Cosmology and Nongalactic Astrophysics

Toward Detecting the Moving Lens Effect with Optical Spectroscopy

David Wittman, Rodrigo Stancioli and Christopher Hopp

Relativity predicts that sky-plane motion of a gravitational lens changes the wavelengths of lensed photons. This moving lens effect is orders of magnitude smaller than cosmological and Doppler effects on the same photons, but can be isolated by comparing different strongly lensed images of a given source. With a massive, fast-moving lens such as a galaxy cluster falling into another cluster, lensed spectra of a given source could differ in wavelength by up to 1 part in $10^6$. We examine the feasibility of detecting this effect with optical spectroscopy, using Keck/Deimos data on the merging cluster RM J001938.7+033557.3 as a case study. We also quantify the predicted sky-plane motions of systems likely to be identified as merging clusters in a $\Lambda$CDM cosmology, and investigate how information on sky-plane motions could help constrain merger models. We find that measurement of the moving lens effect would disambiguate between models in which the subclusters are outbound after first pericenter and those in which the subclusters have returned to the same separation after first apocenter.
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Earth and Planetary Astrophysics

Space Journey Beyond Earth: Exploring the properties of exoplanets and multi-planetary systems

Alexandra Muresan

In contrast to the observed exoplanet diversity, planets within many multi-planetary systems exhibit intra-system similarities in their radii, masses, and orbital spacings. This thesis investigates the planetary properties and system architectures, focusing on the intra-system similarities, the inferred planetary interior compositions, and the differences between single- and multi-planetary systems. Paper A shows that planets within the same system tend to have similar orbital spacings even when their sizes or masses differ. The spacing similarity is more pronounced in orbital period ratios than in mutual Hill separations, while the period ratios are more strongly correlated with the masses than with the radii of adjacent planets. These results indicate that uniform orbital spacings represent a common architectural property and are not necessarily associated with similarities in planetary size or mass. Paper B compares transiting planets in observed single- and multi-planetary systems. After excluding hot Jupiters, the distributions of planet types and radii of singles and multis orbiting FGK stars show no significant differences, suggesting a common underlying planet population. Around FGK host stars, however, an overabundance of multis is identified within a specific planet radius range. Paper C finds that non-gas-giant planets in systems hosting detected gas giants are, on average, larger, more massive, and more irregularly spaced than planets in systems without detected gas giants. Adjacent planets exhibit significant similarities in radius, mass, and bulk density, whereas their inferred core and water mass fractions show substantial scatter and no strong correlations. These results indicate that similarities in bulk properties do not necessarily translate into similarities in compositions. These studies place new constraints on the processes governing planet formation and evolution.
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Astrophysics of Galaxies

Cosmic Collisions I: Optical Morphologies for MIRI-selected galaxies from the PRIMER survey

Gregory Troiani, Allison Kirkpatrick, Leyna Bajaj et al. (+7 more)

We present the first results of visual morphology classifications from the Cosmic Collisions project, comprising 14,657 galaxies from the JWST Public Release IMaging for Extragalactic Research (PRIMER) survey. The sample consists of galaxies detected with MIRI F770W and spans the epoch of peak cosmic star formation (1<z<3). We produce rest-frame optical and observed-frame mid-IR images and enlisted citizen science volunteers through the Zooniverse platform to classify galaxy morphology, surface features, and interactions. The project accumulated 304,524 classifications from more than 4,700 volunteers. We find that mid-IR selected galaxies have significantly different morphologies relative to optical and near-IR selected galaxies, favoring dust-rich disk galaxies at z<2 and compact systems at z>2. This inverts findings from optical selection, which shows galaxies becoming more bulge-dominated and elliptical over cosmic time. In addition, we identify a population of galaxies with disk-like optical morphologies and luminous mid-IR point-source cores that may represent obscured AGN candidates, offering a promising path to identify AGNs based on imaging alone. Comparison with visual classifications from HST imaging demonstrates the impact of JWST's improved sensitivity and resolution on the identification of galaxy structure and interactions, with systems previously identified by HST as compact, smooth, or featureless showing significant extended and internal structure in JWST. These results provide a foundation for future investigations into the connection between morphology, dust structure, star formation, and AGN activity.
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All authors Gregory Troiani, Allison Kirkpatrick, Leyna Bajaj, Joseph Havens, Jackson Stephens, Anton M. Koekemoer, James S. Dunlop, Adriano Fontana, Norman Grogin, Pablo G. Pérez-González

Cosmology and Nongalactic Astrophysics

AdS - de Sitter transition in interacting dark energy models

Yifei Zhao, Jailson Alcaniz, Humberto A. Borges et al. (+2 more)

Recent cosmological results, including the persistent $H_0$ tension and indications of dynamical dark energy, have raised the possibility that the standard $\Lambda$-Cold Dark Matter ($\Lambda$CDM) model may be incomplete. At the same time, theoretical developments based on swampland conjectures indicate that the realization of a stable de Sitter vacuum within string theory is challenging. Motivated by these observational and theoretical considerations, we investigate an interacting $\Lambda$ scenario characterized by a general linear coupling in the dark sector. At the background level, this model naturally allows the dark energy density to evolve from negative to positive values, opening the possibility of a transition from an anti-de Sitter-like phase to the de Sitter-like phase inferred by current observations. We derive the analytic background solutions and perturbation equations, discuss the physically acceptable region of parameter space, and constrain the model with DES-Dovekie type Ia supernovae, DESI BAO and CMB data. Our analysis suggests a parameter space allowing the dark energy density to change sign while maintaining positive dark matter density, motivating further investigation of an interaction-driven anti-de Sitter to de Sitter transition.
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All authors Yifei Zhao, Jailson Alcaniz, Humberto A. Borges, Saulo Carneiro, Rodrigo von Marttens

Instrumentation and Methods for Astrophysics

Fisher and DALI posterior approximations for testing gravity with gravitational waves

Felipe A. da Silva Barbosa, Davi C. Rodrigues, Josiel Mendonça Soares de Souza et al. (+1 more)

We investigate the accuracy and computational efficiency of posterior approximations for gravitational-wave (GW) parameter estimation based on Fisher Matrix and its higher-order extension, the Derivative Approximation for LIkelihoods (DALI), in the context of tests of General Relativity using parameterized deviations in the inspiral waveforms (the TIGER formalism). We adopt the IMRPhenomD waveform and compare the exact posterior sampling to the following approximations in increasing order of complexity: the traditional Fisher Matrix, the Fisher sampling (singlet-DALI), the doublet-DALI and the triplet-DALI. We find that both singlet and doublet-DALI are significantly faster than the exact posterior by factors between 20 and 1000, depending on the inspiral SNRs – larger gains correspond to larger SNRs. These gains are considerably larger for more complete waveforms, such as IMRPhenomHM. To evaluate the accuracy of the approximations, we use Jensen-Shannon divergence. We conclude that both singlet and doublet-DALI systematically improves over the standard Fisher Matrix approximation, while triplet-DALI shows large variability, limiting its practical advantage. We also introduce a code with a new implementation of Fisher and DALI analysis (Symbolic DALI, SymDALI) which computes derivatives symbolically via Wolfram Language.
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All authors Felipe A. da Silva Barbosa, Davi C. Rodrigues, Josiel Mendonça Soares de Souza, Miguel Quartin

Instrumentation and Methods for Astrophysics

PTED: A multi-dimensional two-sample test for scientific inference and generative machine learning

Connor Stone

Two-sample tests are widely applicable in inference and generative modelling, yet users frequently fall back on heuristics and visual inspection due to lack of an accessible test that operates in multiple dimensions. I present Permutation Test using the Energy Distance (PTED), a Python implementation of a powerful two-sample test described in Székely and Rizzo [2004]. The test statistic is the energy distance, a metric on probability distributions that admits a natural sample estimator built from pairwise distances. A permutation test is run on energy distances to produce an exact two-sample test. Because the statistic depends on the data only through pairwise distances, the test applies in high dimensions, on learned feature representations, at large or small or imbalanced sample sizes, and to any data type on which a distance can be defined. An approximation to the formula allows PTED to scale linearly with both number of dimensions and samples while retaining most discriminative power. I highlight a number of instructive sensitivity tests on PTED alongside other multi-dimensional two-sample tests for comparison. PTED is the only method that is sensitive to all tests, though conventional Maximum Mean Discrepancy is identical for all but an over-fitting test.
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