High Energy Astrophysical Phenomena
GenASiS: General Astrophysical Simulation System. II. Self-gravitating Baryonic Matter
Christian Y. Cardall, Reuben D. Budiardja, R. Daniel Murphy et al. (+1 more)
GenASiS (General Astrophysical Simulation System) is a code being developed initially and primarily, though not exclusively, for the simulation of core-collapse
supernovae on the world's leading capability supercomputers. This paper – the second in a series – documents capabilities for Newtonian self-gravitating fluid dynamics, including tabulated microphysical equations of state treating
nuclei and
nuclear matter (`baryonic matter'). Computation of the gravitational potential of a spheroid, and simulation of the gravitational collapse of
dust and of an ideal fluid, provide tests of self-gravitation against known solutions. In multidimensional computations of the adiabatic collapse, bounce, and explosion of spherically symmetric pre-
supernova progenitors – which we propose become a standard
benchmark for code comparisons – we find that the explosions are
prompt and remain spherically symmetric (as expected), with an average shock expansion speed and total kinetic energy that are inversely correlated with the progenitor mass at the onset of collapse and the compactness parameter.
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All authors Christian Y. Cardall, Reuben D. Budiardja, R. Daniel Murphy, Eirik Endeve
Instrumentation and Methods for Astrophysics
Characterization of the commercial spectrograph system for astronomical observations: PIXIS 1300BX Camera and IsoPlane 320A Spectrograph
Jiwon Jang, Changsu Choi, Ho Seong Hwang et al. (+4 more)
We present the result from a comprehensive laboratory and on-sky characterization of the commercial spectrograph system consisting of a PIXIS 1300BX charge-coupled device (CCD) camera and an IsoPlane 320A spectrograph as part of the preparation of the forthcoming all-sky spectroscopic survey of nearby
galaxies (A-SPEC). In the laboratory, we have quantified readout noise, dark current, gain, and full-well capacity via bias, dark, and
photon transfer curve analysis at all acquisition modes. To do that, we have developed a gradient correction technique to address row-dependent signal gradients in the image, which are caused by the shutter-less condition of our CCD camera test setup. The technique successfully reproduces the values in the manufacturer specifications. We also have measured
quantum efficiency exceeding 80% from 400–800 nm and $\gtrsim$ 90% between 450–750 nm, with sub-second persistence decay, making it ideal for rapid, multi-object spectroscopy. Using a set of diffraction gratings (150, 300, and 600 gr mm$^{-1}$), we have evaluated the spatial separability of multiple spectra and spectral resolution. We have conducted a test observation with this spectrograph system at the Seoul National University Astronomical Observatory (SAO) 1 m
telescope and successfully demonstrated its capability of multi-object spectroscopy with moderate resolution of $R \approx 600 - 2600$. We release all Python codes for the test and recipes to facilitate further instrument evaluations.
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All authors Jiwon Jang, Changsu Choi, Ho Seong Hwang, Haeun Chung, Hyeonguk Bahk, Dongkok Kim, Jae-Woo Kim
High Energy Astrophysical Phenomena
Hot, Retrograde Tilted MADs: Misaligned, Precessing, and Shaped by Electromagnetic Torques
Sajal Gupta and Jason Dexter
Tilted
accretion disks in the magnetically arrested (MAD) state may be present in X-ray binaries and active
galactic nuclei such as Sgr A* and M87. We have carried out 3D global GRMHD simulations to study the
evolution of these
accretion flows as a function of black hole
spin and misalignment angle. Prograde MADs align with the
spin through a two-stage process: an initial rapid
alignment phase that operates on the
magnetic flux saturation timescale, followed by a slower,
spin-independent phase. In contrast, retrograde MADs remain persistently misaligned regardless of the black hole
spin, displaying solid-body precession at rates four times higher than weakly magnetized flows at the same
spin magnitude. By deriving torque equations in ideal GRMHD and evaluating them in a frame aligned with instantaneous disk orientation, we demonstrate that electromagnetic (EM) torques always act to align the disk with the BH
spin, but are countered by opposing hydrodynamic fluxes in retrograde flows. We further develop a preliminary empirical model to explain the cause of two-stage prograde
alignment and discuss the possibility of
alignment in the retrograde MAD. Strongly magnetized, retrograde, misaligned
accretion disks provide a candidate scenario for the low-frequency quasi-periodic oscillations in black hole X-ray binaries.
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Earth and Planetary Astrophysics
TOI-6692b: An eccentric 130 day period giant planet with a single transit from TESS
Allyson Bieryla, Karen A. Collins, George Zhou et al. (+46 more)
We report the discovery and characterization of TOI-6692 b, an eccentric (e~0.54) Jupiter on a 130-day orbit. TOI-6692 b was first detected as a community TESS Object of Interest (cTOI) by the Visual Survey Group and the
Planet Hunters group as a single transit candidate via TESS observation. The period was subsequently confirmed via radial velocity monitoring from the
Planet Finder Spectrograph on the 6.5m Magellan
telescope. Additional radial velocities were acquired with the CHIRON, FEROS, and CORALIE spectrographs. LCOGT ground-based photometric follow-up was conducted over 2 weeks to detect another transit and refine the period. Although we did not detect an ingress or egress of the 11.04 hr transit, we did detect a possible in-transit signal in the multi-night data and provide an updated ephemeris for future monitoring. TOI-6692 b is one of few
planets with orbital periods longer than 100 days that have a secure mass, radius, and eccentricity detection. As with most
giant planets at these orbital periods, the eccentricity of TOI-6692 b is lower than that expected of
planets undergoing high-eccentricity
tidal migration, but is more consistent with the expectations of
planet-
planet scattering outcomes. A long-term radial velocity trend was detected and further monitoring is warranted to determine the outer companion period. TOI-6692 b is also one of few TESS single transit targets that have its period eventually confirmed via follow-up photometric campaigns timed to capture transits despite the relatively large ephemeris uncertainties. Such efforts highlight the capabilities of night-to-night stability on ground-based photometric facilities today.
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All authors Allyson Bieryla, Karen A. Collins, George Zhou, David W. Latham, Brad Carter, Paul Dalba, Robert Gagliano, Thomas L. Jacobs, Martti Holst Kristiansen, Daryll Lacourse, Mark Omohundro, H.M. Schwengeler, Khalid Barkaoui, Rafael Brahm, Douglas A. Caldwell, Jeffrey D. Crane, Tansu Daylan, Sarah Deveny, Yadira S. Gaibor, Michael Gillon, Thomas Henning, Keith Horne, R. Paul Butler, Jason D. Eastman, Steve B. Howell, Emmanuel Jehin, Eric L.N. Jensen, Andres Jordan, Michelle Kunimoto, Colin Littlefield, Lena Parc, Samuel N. Quinn, Malena Rice, Joseph E. Rodriguez, Richard P. Schwarz, Ramotholo Sefako, Stephen A. Shectman, Avi Shporer, Abderahmane Soubkiou, Gregor Srdoc, Michal Steiner, Marcelo Tala Pinto, Johanna Teske, Trifon Trifonov, Solene Ulmer-Moll, Cristilyn N. Watkins, Sharon X. Wang, Jhon Yana Galarza, Samuel W. Yee
Cosmology and Nongalactic Astrophysics
Unifying cluster and galaxy cosmology analyses using the galaxy-halo connection
Shulei Cao, Hao-Yi Wu, Andrés N. Salcedo et al. (+3 more)
Galaxies and
galaxy clusters trace the same
cosmic density field, but their statistics have been modeled separately in cosmological analyses. We present a unified, simulation-based framework to model them using the
galaxy-
halo connection. Our analysis includes cluster
lensing,
galaxy clustering, and
galaxy-cluster cross-correlation. We validate our method on the FLAMINGO hydrodynamic simulation. Relative to the cluster-only approach, combining these probes improves the $\sigma_8-\Omega_m$ figure of merit by a factor of 15. Our framework enables stringent tests of cosmological models and exploits small-scale information.
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All authors Shulei Cao, Hao-Yi Wu, Andrés N. Salcedo, David H. Weinberg, Matthieu Schaller, Joop Schaye
Astrophysics of Galaxies
The detectability of bars at high redshift: a case study using Euclid-like mock observations of TNG50 simulated galaxies
Gustavo F. Gonçalves, Rubens E. G. Machado, Raquel R. Valença et al. (+3 more)
Modern surveys such as Euclid report a decline in the fraction of barred
galaxies from the local Universe to $z \sim 1$, whereas the TNG50 simulation predicts higher bar fractions, in tension with observations. This discrepancy may be due to observational biases in bar detectability when comparing simulations with observations. We present a proof-of-concept study quantifying how Euclid-like observational conditions affect bar detectability in TNG50. We analysed the entire
galaxy sample at $z = 0.5$ and highlight one borderline case with a bar length of 2.1 kpc and bar strength $A_2 = 0.4$. Synthetic images were produced with Monte Carlo radiative transfer and realistic post-processing, and analysed with ellipse fitting and
Fourier decomposition, as well as the recently constructed Zoobot analysis. Results were compared to idealised, noise-free
stellar mass maps. In the illustrative case the bar is clearly detected in the mass map and remains visible in the Euclid VIS $I_{\rm E}$ filter, where Zoobot also classifies it as barred, but becomes undetectable in $Y_{\rm E}$ and in the VIS-NISP RGB composite, with all methods failing outside VIS. Extending to the full $z = 0.5$ sample, Zoobot recovers only 31/141
galaxies, while $A_2$ and ellipse fitting perform better (80/141 and 67/141) but still miss many short or weak bars. When non-detections are counted as unbarred, the bar fraction of 44 percent falls to $12\!-\!33$ percent depending on the method. These results demonstrate the strong impact of observational effects on bar detectability and motivate bar-fraction estimates which incorporate realistic instrumental conditions across
redshift in cosmological simulations.
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All authors Gustavo F. Gonçalves, Rubens E. G. Machado, Raquel R. Valença, E. Athanassoula, Karín Menéndez-Delmestre, Thiago Bueno-Dalpiaz
Astrophysics of Galaxies
A differential-geometry approach to black hole characterization of megamaser systems in static spherically symmetric spacetimes
Santiago González-Salud, Rodrigo Bárcena-Ramos, Alfredo Herrera-Aguilar et al. (+1 more)
We develop a geometry-first model that maps measured thin-disk water megamaser observables–sky angles, frequency shifts, their secular drifts and the angular
redshift rate–to the black hole parameters in a generic static, spherically symmetric (SSS) spacetime written in the Schwarzschild gauge. The core of the approach is local: dot-product relations in the equatorial curved geometry relate the conserved light-deflection parameter to the observed detector angle at finite distance, providing a connection between sky positions and
photon constants of motion. These local identities feed a closed model for the frequency shift of
photons traveling between a maser clump circularly orbiting a black hole and a finite-distance detector, making explicit the dependence on the metric at emission and detection radii. We also apply the Gauss-Bonnet
theorem to this construction on the equatorial two-
manifold as an intrinsic cross-check. This
theorem provides a global consistency relation between the local emission and detection angles, helping to validate sign conventions and angle branch choices in the local setup. In this sense, the local and global perspectives on the megamaser system support each other. To supplement the instantaneous information contained in frequency shifts, we incorporate the time-domain general relativistic invariant, the
redshift rapidity. We further introduce a prospective angular-domain observable, the angular
redshift rate, and give its analytic expression in the SSS framework. The results are formulated for generic SSS backgrounds, providing closed relations suited for likelihood-based inference from VLBI positions and spectral monitoring. In particular, for a Schwarzschild background, the black hole mass, its distance to Earth and megamaser orbital radius are fully constrained in the
language of astrophysical observables.
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All authors Santiago González-Salud, Rodrigo Bárcena-Ramos, Alfredo Herrera-Aguilar, Roberto Cartas-Fuentevilla
Cosmology and Nongalactic Astrophysics
MeerKAT observations of Abell 1775 and Abell 1795: the discovery of a hadronic radio halo?
R. J. van Weeren, E. Osinga, G. Brunetti et al. (+13 more)
Giant radio haloes are diffuse synchrotron sources typically found in merging
galaxy clusters, while smaller mini-
haloes occur in cool-core clusters. Both trace
cosmic-ray electrons in the intracluster medium, though recent observations suggest their distinction is not always clear. We present new 903-1655 MHz MeerKAT observations of Abell 1775 and Abell 1795, both hosting cool cores and cold fronts. Combined with reprocessed 120-168 MHz LOFAR Two-metre Sky Survey data, we perform imaging and spectral analyses of their
radio emission. In both clusters, we detect
radio haloes with distinct inner and outer components. In Abell 1775, the
halo appears diffuse at 1.3 GHz, while LOFAR images reveal steep-spectrum filaments. In Abell 1795, the inner component corresponds to a previously reported mini-
halo candidate, but the full structure extends to $\sim$1 Mpc with a spectral index of $\alpha=-1.08\pm0.06$. The presence of such a large, flat-spectrum
halo in a dynamically relaxed cluster makes Abell 1795 an outlier relative to typical merging systems. This suggests that some relaxed clusters may still retain sufficient
turbulence to sustain particle re-acceleration, or that hadronic interactions producing secondary electrons play a significant role. Together with other recent discoveries in cool-core systems, our results indicate that some large
radio haloes may have been overlooked in past studies due to limited dynamic range near bright central AGN. Finally, we detect steep-spectrum emission south of Abell 1795's central AGN, tracing a 45 kpc X-ray and optical filament that terminates in an X-ray cavity, likely linked to a past AGN outburst.
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All authors R. J. van Weeren, E. Osinga, G. Brunetti, C. J. Riseley, A. Botteon, R. Timmerman, A. Bonafede, M. Brüggen, R. Cassano, V. Cuciti, D. Dallacasa, F. de Gasperin, J. M. G. H. J. de Jong, F. Gastaldello, K. Knowles, X. Zhang
Astrophysics of Galaxies
UNCOVER/MegaScience Finds Uniform and Highly Bursty Star Formation at 3 < z < 9, consistent with the High-Redshift UV Luminosity Function
Ikki Mitsuhashi, Katherine A. Suess, Joel Leja et al. (+24 more)
Star formation timescales are key to understanding fundamental physics like feedback mechanisms, as well as the abundance of bright
galaxies at $z>10$. We investigate
galaxy star formation histories (SFHs) and their
evolution across $z\sim3$–9 by measuring the line-to-UV ratio (\rline) and line equivalent width (EW) of \hanii\ and \oiiihb\ directly from UNCOVER/MegaScience spectro-photometry without relying on a specific SFH or nebular line modeling. Our photometric measurements recover \rline\ and EW to $<10\%$ systematic accuracy compared to spectroscopy. This allows us to construct a large mass- (and flux-) complete sample and quantitatively examine how \rline\ evolves with
redshift and
stellar mass. We find that the intrinsic scatter in \rline\ does not significantly evolve with
redshift across $3<z<7$, though it may increase at $z\gtrsim8$. We build population-level toy models using fsps to help interpret our observations, and find that scatter in \rline\ primarily reflects the amplitude of SFH fluctuations; this implies that our observed lack of
evolution in the scatter of \rline\ is due to similar
star formation burstiness from $z\sim3$ to $z\sim7$. Our observations are best reproduced by a set of SFHs with rising, long-duration, and large-amplitude bursts. Finally, we demonstrate that the toy model that best describes our $z\sim6$ data can boost UV brightness by up to $\Delta M_{\rm UV}\sim-2.0\,{\rm mag}$ compared with a 200\,Myr constant SFH, and naturally produces a large number of
galaxies at $z>10$. This suggests that no significant
evolution in
star formation burstiness is required to explain the abundance of UV-bright
galaxies at high
redshift.
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All authors Ikki Mitsuhashi, Katherine A. Suess, Joel Leja, Rachel Bezanson, Jenny E. Greene, Emilie Burnham, Gourav Khullar, Abby Mintz, Themiya Nanayakkara, Karl Glazebrook, Sedona H. Price, David J. Setton, Bingjie Wang, John R. Weaver, Hakim Atek, Pratika Dayal, Robert Feldmann, Seiji Fujimoto, Lukas J. Furtak, Brian Lorenz, Natalia Porraz Barrera, Ivo Labbe, Gabriel Brammer, Sam E. Cutler, Richard Pan, Katherine E. Whitaker, the UNCOVER/MegaScience team
Astrophysics of Galaxies
A first GLIMPSE into star clusters populations across cosmic time
Adélaïde Claeyssens, Angela Adamo, Vasily Kokorev et al. (+12 more)
We present the first sample of 222 high-
redshift (z>0.5)
star clusters, detected with JWST/NIRCam in 78 magnified
galaxies from different
galaxy cluster fields. The majority of the systems (~60%) is observed in the very deep NIRCam observations of the cluster AbellS1063 (GLIMPSE program), showing the power that deep observations, combined with
lensing, has to reveal these
primordial stellar structures. We perform simultaneous size-flux estimates in all available NIRCam filters and spectral energy distribution (SED) fitting analysis to recover
star cluster physical properties. All
star cluster candidates have very high magnification.
Star clusters and clumps show similar ages and
redshift distributions, although noticeable differences are seen in their masses, sizes and
stellar surface densities inherent to the lack of resolution in the latter group. We reconstruct the formation
redshift of
star clusters and find that the large majority of the observed
star clusters show young ages (<100 Myr) and seems to form at
cosmic noon (CN,1<z<4). A small sample of CN
star clusters is about 1 Gyr old, these potential globular clusters have formed well within
cosmic reionization.
Star clusters have
stellar densities in the range 10^2 to 10^6 M/pc^2, with median values around 10^4 pc2. Their sizes and densities better overlap with those of
nuclear star clusters in the local Universe. These intrinsic properties make high-z
star clusters a viable channel to grow intermediate mass black holes. We use
Bayesian inference to make first direct measurement of the
star cluster mass function at z>1, based on a subsample of 60
star clusters younger than 100 Myr and with masses above 2e6 Msun. The
star cluster mass function is well described by a power-law with slope beta = -1.89 suggesting that a power-law -2 function might already be in place in the distant Universe.
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All authors Adélaïde Claeyssens, Angela Adamo, Vasily Kokorev, Lukas Furtak, Johan Richard, Benjamin Beauchesne, Miroslava Dessauges-Zavadsky, Hakim Atek, John Chisholm, Ryan Endsley, Seiji Fujimoto, Damien Korber, Richard Pan, Alberto Saldana-Lopez, Daniel Schaerer
Cosmology and Nongalactic Astrophysics
Relaxing DESI DR2 BAO Constraints on $\sum m_\nu$ with Planck and SPT-3G 2018 in the Context of SPT D1
Dmitry Gorbunov and Nikita Nedelko
We present constraints on the sum of
neutrino masses $\sum m_\nu$ from a
dataset incorporating the full SPT-3G 2018 TT/TE/EE+
lensing spectra together with Planck PR4
lensing and low-$\ell$ parts of the Planck PR3 spectra. Using it as a baseline for the DESI DR2 BAO measurements, we arrive at a $95\%$ upper limit of $\sum m_\nu < 0.11$ eV, relaxing the tension between $\rm \Lambda$CDM and lower bounds on $\sum m_\nu$ based on
neutrino oscillation experiments. When including DES Y1 weak
lensing information and the Pantheon+ SNIa catalog, the limit is further loosened to $\sum m_\nu<0.138$ eV with a slight preference for $\sum m_\nu>0$. On contrast, replacing SPT-3G 2018 primary CMB and
lensing spectra with ones from the SPT-3G 2019-2020 (D1) release tightens the overall constraint to $<0.082$ eV and pushes the $\sum m_\nu$ posterior mode value to zero, indicating a preference for quasi-negative
neutrino masses in line with the D1 analysis. This is a curious shift within SPT-3G measurements of the same field taken in 2018 and in 2019-2020 and processed with different analysis pipelines.
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Instrumentation and Methods for Astrophysics
proto-Lightspeed: a high-speed, ultra-low read noise imager on the Magellan Clay Telescope
Christopher Layden, Kevin Burdge, Gabor Furesz et al. (+9 more)
proto-Lightspeed is a new instrument that has been commissioned on the Nasmyth East port of the Magellan Clay
Telescope at Las Campanas Observatory to deliver high-speed optical imaging with deep sub-electron read noise. Making use of commercial re-imaging lenses and the ORCA-Quest 2 camera from Hamamatsu, proto-Lightspeed images a field $1'$ in diameter at up to $200$ Hz or windowed fields at higher rates, up to 6600 Hz for a $1.6''\times 1'$ field of view. proto-Lightspeed delivers seeing-limited image quality in the $g'$, $r'$, and $i'$ bands and adjustable magnification for pixel scales between $0.017''-0.050''$. proto-Lightspeed is well suited to studying compact binary systems,
exoplanet transits, rapid flaring associated with
accretion, periodic optical emission from
pulsars, occultations of background
stars by small trans-Neptunian Objects, and any other rapidly variable source. proto-Lightspeed will be a P.I. instrument beginning in 2026B, available for use by members of the Magellan Consortium. In this paper, we discuss the design and performance of the instrument, results from its two commissioning runs, and plans for a facility instrument, Lightspeed, to support simultaneous multicolor imaging across a $7'\times4'$ field.
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All authors Christopher Layden, Kevin Burdge, Gabor Furesz, Juliana Garcia-Mejia, Jack Dinsmore, Geoffrey Mo, David Osip, John J. Piotrowski, Roger W. Romani, August Berne, Deepto Chakrabarty, Emma Chickles
High Energy Astrophysical Phenomena
Measuring the Black Hole and Accretion Parameters of Sagittarius A* from EHT Observations using a Semi-Analytic Model
Braden J. Marazzo-Nowicki, Paul Tiede, Dominic O. Chang et al. (+2 more)
The Event Horizon
Telescope (EHT) Collaboration produced the first image of the apparent shadow of the central black hole of Sagittarius\,A$^*$ (\sgra). \sgra source structure varies significantly on timescales shorter than the duration of an observation, preventing improved data coverage through Earth rotation aperture synthesis. This rapid variability provides the opportunity to quantify intrinsic variability and separate time-variable emission features from stable signatures of strong
gravity and the
accretion environment. To infer the properties \sgra and its surrounding
accretion flow, we perform
Bayesian inference on a series of EHT data segments (“snapshots”). We directly fit parameters of a semi-analytic emission model jointly with complex station gains to snapshot visibilities, then extract estimates of the time-averaged, persistent source structure and temporal variability by stacking snapshots in a
Bayesian hierarchical model. This approach successfully reproduces parameters of General Relativistic Magnetohydrodynamics simulations using synthetic EHT observations. Even with physically motivated assumptions about the \sgra environment, black hole
spin and
magnetic field parameters are poorly constrained by 2017 EHT observations. Our inference constrains other parameters, favoring a nearly face-on observer inclination ($\theta_{\rm o} = 9.2\degree \pm 3.6 \degree \pm_{\rm v} 11.6\degree$), an emission peak near the horizon ($R_{\rm peak} = 4.9 \pm 0.1 \pm_{\rm v} 0.5\,GM/c^2$), near-vertical projected
spin position angle ($p.a. = 7.3\degree \pm 7.08 \degree \pm_{\rm v} 43.5\degree$ counterclockwise from vertical), and dominant emission $43.4\degree \pm 2.0\degree \pm_{\rm v} 5.9\degree$ above the equatorial plane, where we separate average structure uncertainty ($\pm$) from the impacts of temporal variability and model misspecification ($\pm_{\rm v}$).
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All authors Braden J. Marazzo-Nowicki, Paul Tiede, Dominic O. Chang, Daniel C. M. Palumbo, Michael D. Johnson
Solar and Stellar Astrophysics
A Binary-Based Reassessment of the Age and Stellar Properties of NGC 7789 Using Twelve Binary Components
Kadri Yakut, Belinda Kalomeni and Saul Rappaport
We present a binary-based reassessment of the age of the intermediate-age open cluster NGC 7789, together with well-constrained
stellar parameters for twelve components in six SB2 systems, including two eclipsing binaries. Our analysis employs a unified modelling framework that combines radial-velocity orbits, TESS light curves, and blue-to-IR spectral energy distributions (SEDs), providing a robust alternative to traditional isochrone-based age determinations. By adopting common cluster-wide parameters (age, distance, and line-of-sight extinction) when solving for the
stellar parameters of the binary components, we obtain a coherent set of masses, radii, effective temperatures, and luminosities for all twelve
stars. The combined SED, eclipsing-binary, and radial-velocity analysis yields a well-constrained cluster age of $1.26 \pm 0.09$ Gyr and an extinction of $A_V = 0.90 \pm 0.05$ mag, while remaining consistent with the
Gaia DR3 distance of $d \simeq 2.06$ kpc used as an external prior. An independent
Gaia DR3 astrometric analysis gives a distance of $2082 \pm 142$ pc and confirms the membership of all six systems. The twelve binary components occupy the turnoff and subgiant regions of the cluster, enabling stringent evolutionary tests: in the radius–mass, radius–temperature, and temperature–mass diagrams, they show excellent agreement with modern
stellar evolution models for the derived cluster parameters. NGC 7789 thus serves as a valuable
benchmark for multi-observable, binary-based age determinations in open cluster studies.
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Cosmology and Nongalactic Astrophysics
TORRCH: Tomographic reconstruction of the reionization of cosmic hydrogen with Ly${\alpha}$ emitters and non-Ly${\alpha}$-selected galaxies
Soumak Maitra, Girish Kulkarni, Vipul Arora et al. (+5 more)
Tomographic reconstruction of reionization is a long-sought goal. It would move the field beyond global summary statistics, such as the volume-averaged ionised fraction, to direct, field-level constraints on the ionization
topology. With this in mind, we present TORRCH (TOmographic Reconstruction of the Reionization of
Cosmic Hydrogen), a deep-learning framework that reconstructs the neutral-hydrogen fraction field during the epoch of reionization from the spatial distributions of Ly$\alpha$ emitters (LAEs) and non-Ly$\alpha$-selected
galaxies (NLSGs) at luminosity limits comparable to current surveys. Using hydrodynamical simulations post-processed with radiative transfer, we train a deterministic 3D U-Net on mock surveys spanning diverse reionization scenarios and predict the neutral-fraction field. We find that TORRCH recovers the large-scale ionization morphology from synthetic data comparable to current surveys with high fidelity, and reproduces both the one-point distribution and the 2D power spectrum of projected neutral fractions. The predicted
galaxy-IGM cross-correlation is also captured well, including the expected small-scale anti-correlation and its decline towards zero at large separations. Reconstruction quality depends on tracer completeness, with deep joint LAE+NLSG samples yielding the most accurate morphology, while LAE-only selections retain bubble-scale
topology but with reduced fidelity. Robustness tests show that the method is stable to variations in ionization conditions between training and test data, and to realistic
redshift uncertainties. Our results suggest that
galaxy-based
tomography can potentially deliver reliable reionization maps across realistic survey
redshift windows.
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All authors Soumak Maitra, Girish Kulkarni, Vipul Arora, Matteo Viel, Shikhar Asthana, James S. Bolton, Martin G. Haehnelt, Laura Keating
Cosmology and Nongalactic Astrophysics
A shot in the dark: searching for dark substructures in the RX J0437+00 galaxy cluster
David J. Lagattuta, Mathilde Jauzac, Jessica E. Doppel et al. (+2 more)
Obtaining a census of dark matter structures at low mass ($\leq 10^9 M_\odot$) can provide strong constraints on the nature of dark matter, though identifying such structures remains difficult. In this work, we study the
galaxy cluster RX J0437.1+0043, taking advantage of its powerful "exotic"
Hyperbolic-Umbilic (HU)
lensing configuration to search for substructure candidates. Using a combination of high resolution imaging, IFU spectroscopy, and gravitational
lensing modelling, we report on a tentative detection of a dark matter subhalo ($m_{\rm halo} = 2.25 \pm 0.94 \times 10^9 M_\odot$) near the vicinity of one of the largest HU images. We stress that this result is still preliminary and that deeper data and more advanced modelling techniques are needed to ultimately confirm this detection. Nevertheless, this work outlines the first steps towards understanding subhalo properties in dense cluster environments, developing HU cluster lenses as a potential new tool for investigating dark matter.
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All authors David J. Lagattuta, Mathilde Jauzac, Jessica E. Doppel, Guillaume Mahler, Anna Niemiec
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Searching for Ultralight Scalar Dark Matter with Clocks in Low Earth Orbit
Dawid Brzeminski and Aaron Pierce
The density of ultralight dark matter can be modified in the vicinity of macroscopic bodies when the dark matter possesses quadratic couplings to the Standard Model. If these couplings are sufficiently strong, Earth's atmosphere acts to shield the dark matter, thereby limiting the effectiveness of laboratory-based experiments. Experiments performed at altitudes exceeding the dark matter de Broglie wavelength experience the same orbit-averaged field amplitude as in the absence of scattering.
Quantum clocks are capable of detecting variations in fundamental parameters due to the dark matter background. If based on the International Space Station, they are therefore well-suited to probe dark matter masses $m_{\rm DM}\gtrsim 10^{-9} \text{\, eV}$. Moreover, when the dark matter de Broglie wavelength is smaller than Earth's radius ($m_{\rm DM} \gtrsim 10^{-10}$ eV), the dark matter profile around Earth exhibits a dipole feature. In Low Earth Orbits this dipole temporally modulates potential dark matter signals. This provides a powerful cross-check of the orbit-averaged effect and can enhance the sensitivity of these experiments. We find optical clocks could give rise to world-leading constraints in some cases. Orbiting
nuclear clocks could probe even more of the parameter space inaccessible to ground-based experiments.
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Earth and Planetary Astrophysics
Assessing the Vera Rubin Observatory's Ability to Discover Asteroid Impactors Before They Collide with Earth
Qifeng Cheng, Daniel Scolnic, Jacob A. Kurlander et al. (+2 more)
Asteroid impactors larger than ~10 m, from Chelyabinsk-scale airburst and Tunguska-scale events to >300 m continental threats, remain the dominant planetary-defense risk. While the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will transform
Solar System science, its observing cadence and survey design were not specifically optimized to discover imminent impactors. To assess its performance, we introduce a new method for efficiently generating synthetic impactor populations by minimally perturbing sampled NEOMOD3 orbits and evaluate their discovery efficiency with the Sorcha survey simulator. Our simulations show that LSST discovers 79.7% of large impactors (>140 m), decreasing to 50.3% for upper mid-sized (50-140 m), 26.8% for lower mid-sized (20 - 50 m), and 10.5% for small objects (10-20 m). Warning times of the discovered impactors show a similar size dependence: small objects are typically discovered only weeks before impact (median:12.4 days), lower mid-sized within a month (median: 21.5 days), and upper mid-sized objects on timescales of a few months (median: 106.2 days). 39.0% of large impactors are discovered more than a year before impact, lacking long-lead warning despite their brightness. A loss-mode analysis reveals the underlying cause that small impactors are limited mainly by photometric sensitivity, whereas mid-sized and large objects are missed primarily due to cadence and linking constraints from LSST and its
Solar System Processing (SSP) Pipelines. These results show that LSST excels at discovering faint, small impactors, but cannot by itself guarantee long-lead warning across the hazardous size spectrum. Coordinated multi-survey strategies will therefore be essential in the LSST era to achieve robust planetary-defense capability, and we study a complementary high-cadence, shallow-depth example with the Argus Array.
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All authors Qifeng Cheng, Daniel Scolnic, Jacob A. Kurlander, Ian Chow, Maryann Benny Fernandes
Earth and Planetary Astrophysics
Accretion Rate Changes Detected in a Polluted White Dwarf
Jay Farihi, Hiba Tu Noor, Carl Melis et al. (+6 more)
This letter reports statistically significant changes in the equivalent widths of MgII and CaII lines in the dusty and polluted white
dwarf WD 0106-328, based on six epochs of spectroscopy using the VLT and Keck spanning 25 yr. Furthermore, the ratio of these two equivalent widths may also vary, with a 7% probability of being constant. Between 2000 and 2025, both Mg and Ca have experienced decreases in
accretion rates, of approximately 20 and 60%, respectively, but with individual variation during the interim. These metal abundance decreases are the first empirical corroboration of
diffusion theory in white
dwarfs, which predict sinking timescales on the order of days for this
star. However, the persistent atmospheric metals require a more gradual, circumstellar process, where one possibility is viscous spreading in an ionized disk of metals, consistent with $\alpha\approx0.1$ within that formalism. The combination of optical and ultraviolet spectroscopy with the Hubble Space
Telescope detects all the major rock-forming elements (O, Mg, Si, Fe), and demonstrates that Fe dominates the accreted material by mass, and that it is delivered mostly as pure metal from within a differentiated parent body. This inference is consistent with the possibility that chemically-segregated
accretion may result from a combination of planetary assembly, fragmentation, disk
evolution, and be observed on relatively short timescales.
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All authors Jay Farihi, Hiba Tu Noor, Carl Melis, Beth L. Klein, Snehalata Sahu, Boris T. Gänsicke, Mark C. Wyatt, Seth Redfield, Ted M. Johnson
Astrophysics of Galaxies
Comprehensive Gaia DR3-Based Astrometric, Photometric, and Kinematic Studies of the Binary Open Cluster $h$ and $\chi$ Persei
Seval Taşdemir, Waleed Elsanhoury, Deniz Cennet Ç{\i}nar et al. (+2 more)
In the
Gaia era, a comprehensive analysis of the binary open clusters NGC 869 (h Persei) and NGC 884 (chi Persei) system has been conducted to investigate its structural, astrophysical, kinematic, and
Galactic orbital properties, along with its dynamical
evolution. By applying the UPMASK
algorithm to
Gaia astrometric data for the estimation of cluster membership probabilities, it has been determined that 808
stars in NGC 869 and 707
stars in NGC 884 exhibit the highest statistical likelihood of being cluster members. The fundamental astrophysical parameters of the clusters were inferred within a
Bayesian framework using
Gaia data and PARSEC
stellar evolutionary isochrones, through the application of the Markov Chain Monte Carlo (MCMC) technique. The estimated parameters are: colour excess E(B-V) = 0.516 +0.17/-0.24 mag and 0.516 +0.22/-0.33 mag, distances 2376 +301/-278 and 2273 +230/-290 pc, ages log(t/yr) = 7.31 +0.17/-0.32 and log(t/yr) = 7.30 +0.13/-0.29, and
metallicities [Fe/H] = -0.24 +/- 0.12 and [Fe/H] = -0.25 +/- 0.12 dex for NGC 869 and NGC 884, respectively. Since spectroscopic observations are not available for the clusters, SED analysis was employed for the member
stars, yielding results consistent with those obtained using the MCMC method. Kinematic and
Galactic orbital analyses suggest that the open clusters originated in nearby regions of the
Galaxy. This interpretation is supported by their similar space velocities and
Galactic orbital parameters. Furthermore, orbital integration over 1 Gyr indicates a potential interaction between the clusters within the next 11 Myr. This study provides strong evidence of a common origin and a possible future dynamical interaction, contributing valuable insights into the formation and
evolution of binary open clusters in the Milky Way.
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All authors Seval Taşdemir, Waleed Elsanhoury, Deniz Cennet Ç{\i}nar, Aly Haroon, Selçuk Bilir
Cosmology and Nongalactic Astrophysics · Cross-listed from physics.ins-det
Probing dark matter interactions with a RES-NOVA prototype cryogenic detector
D. Alloni, G. Benato, P. Carniti et al. (+44 more)
We report on the operation of a 13 g PbWO$_4$
crystal, grown from archaeological Pb and operated as a cryogenic calorimeter in an underground environment. Read out with a Ge thermistor, the detector achieves a low energy threshold and, for the first time, enables the derivation of a dark matter exclusion limit using PbWO$_4$ as target material, for both
spin-dependent interactions on
neutrons and
spin-independent interactions. Although limited in mass and not representative of the final RES-NOVA detector design, this prototype demonstrates effective control of mechanical vibrations and low-energy noise in a cryogenic system, which is a key requirement for rare-event searches. The experiment therefore provides a proof of principle for the RES-NOVA detection concept, validating the use of archaeological Pb-based PbWO$_4$
crystals, low-background operation, and robust data-analysis procedures. These results establish a solid technological and methodological foundation for future RES-NOVA detectors employing larger target masses and advanced thermal readout technologies.
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All authors D. Alloni, G. Benato, P. Carniti, M. Cataldo, L. Chen, M. Clemenza, M. Consonni, G. Croci, I. Dafinei, F.A. Danevich, C. de Vecchi, D. Di Martino, E. Di Stefano, N. Ferreiro Iachellini, F. Ferroni, F. Filippini, S. Ghislandi, A. Giachero, L. Gironi, C. Gotti, D.L. Helis, D.V. Kasperovych, V.V. Kobychev, G. Marcucci, A. Melchiorre, A. Menegolli, S. Nisi, M. Musa, L. Pagnanini, L. Pattavina, G. Pessina, S. Pirro, S. Pozzi, M.C. Prata, A. Puiu, S. Quitadamo, M.P. Riccardi, M. Ricci, M. Rossella, R. Rossini, E. Sala, F. Saliu, A. Salvini, V.I. Tretyak, L. Trombetta, D. Trotta, H. Yuan
Earth and Planetary Astrophysics
Evolution of Mean Orbital Spacing in Planetary and Satellite Systems under Tidal Dissipation and Nebular Drag
Vladimir Pletser
The approximately
geometric spacing of orbital distances in planetary and regular satellite systems has long been recognized, yet its dynamical
evolution remains poorly constrained. In this paper, we investigate the secular
evolution of the mean distance ratio of secondaries under the combined effects of primary
tidal dissipation and nebular gas drag. A general analytical framework is derived linking the initial and final mean distance ratios to system parameters and to the physical characteristics of the dominant dissipative processes. Applying this formalism to the
Solar System
planets and to the regular satellites of Jupiter, Saturn, and Uranus, we show that primary
tidal interactions produce only negligible changes in mean distance ratios over timescales comparable to the age of the
Solar System. Similarly, nebular gas drag during the protoplanetary and circumplanetary disk phases leads to limited deviations over a broad range of disk models and lifetimes. These results suggest that, within the assumptions adopted, the mean distance ratio evolves only weakly and may preserve information about
primordial system configurations established during early disk
evolution. The approximate conservation of this quantity may therefore provide a useful diagnostic for constraining the formation and early dynamical
evolution of planetary and satellite systems, with potential implications for the architecture of exoplanetary systems.
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Solar and Stellar Astrophysics
Cyclic sunspot activity during the first millennium CE as reconstructed from radiocarbon
Ilya Usoskin, Sami K. Solanki, Natalie A. Krivova et al. (+1 more)
Context.
Solar activity, dominated by the 11-year cyclic
evolution, has been observed directly since 1610. Before that, indirect cosmogenic proxy data are used to reconstruct it over millennia. Recently, the precision of radiocarbon measurements has improved sufficiently to allow reconstructing
solar activity over millennia. Aims. The first detailed reconstruction of
solar activity, represented by annual sunspot numbers, is presented for 1-969 CE. Methods. The reconstruction of sunspot numbers from D14C was performed using a physics-based method involving several steps: using a carbon-cycle box model, the 14C production rate, corrected for the geomagnetic shielding, was computed from the measured data; The open
solar magnetic flux was computed using a model of the heliospheric
cosmic-ray modulation; Sunspot numbers were calculated using a model of the
evolution of the Sun's
magnetic field. The Markov Chain Monte Carlo approach was used to account for different sources of uncertainty. Results. Annual sunspot numbers were reconstructed for the first millennium CE. This period includes one extreme
solar event of 774 CE and one Grand
solar minimum of 650-730 CE. We could identify 91
solar cycles, of which 26 were well-defined, while 24 and 41 were reasonably and poorly defined, respectively. The mean cycle length was 10.6 years, but the lengths of individual cycles vary between 8 and 15 years. The existence of empirical Waldmeier's relations remains inconclusive. No significant periodicities were found beyond the 11-year cycle. Conclusions. This work fills the gap in the
solar cycle statistics between the previously reconstructed first millennium BCE and the second millennium CE, providing vital constraints for the
solar dynamo and irradiance models. A consistent 3-millennium-long reconstruction of sunspot numbers, based on a composite multi-proxy cosmogenic record, is pending.
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All authors Ilya Usoskin, Sami K. Solanki, Natalie A. Krivova, Theodosis Chatzistergos
Solar and Stellar Astrophysics
A multiwavelength ALMA view of gas and dust in binary protoplanetary system AS 205: Evidence of dust asymmetric distribution
Nguyen Thi Phuong and Nguyen Tat Thang
We present Atacama Large Millimeter/Submillimeter Array observations of multi-wavelength
dust emissions at 3.1 and 1.3 mm; along with molecular line emissions of CO(2-1), CO(3-2), $^{13}$CO(3-2), and C$^{18}$O(3-2) at spatial resolutions of 7-45 AU towards the protoplanetary system AS 205. The
dust emissions exhibit two distinct components of AS 205 N and AS 205 S, separated by 1.3 arcsec. While gas kinematics within the
dust disk regions are dominated by Keplerian rotation, the more extended gas emission displays complex morphology and kinematics strongly affected by the binary gravitational interaction in the outer regions. The
stellar masses of AS 205 N and AS 205 S are estimated at $0.78\pm0.19$ and $1.93\pm0.86$ M$_\odot$, respectively. Azimuthal variation is observed in the spectral index distribution of both disks. In AS 205 N, the spectral index minimum in the southwest is coincident with the peaks of CO($2-1$), CO($3-2$), and $^{13}$CO($3-2$) integrated intensity and the relative position of its southern counterpart. On the other hand, the spectral index distribution in AS 205 S exhibits two prominent maxima, with the one in the northeast aligning with the peak of $^{13}$CO($3-2$), and the peak in the south coinciding with local maxima in CO($2-1$) and CO($3-2$) azimuthal profiles. These results suggest a correlation between
dust grain size and/or optical depth with the gas distributions.
Dust trapping along the spiral arms possibly contributes to the spectral index minima in AS 205 N; however, the observed asymmetry across both disks suggests the involvement of additional mechanisms.
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Cosmology and Nongalactic Astrophysics
Constraining dark energy models using Jackknife and Bootstrap resampling
Roshna K, Nikhil Fernandes, P Praveen et al. (+1 more)
Analyses of type Ia
supernovae have helped us shed light on the existence and nature of dark energy. Most of these analyses have relied on
Bayesian techniques. In this work, we employ resampling techniques, namely Jackknife and Bootstrap, together with generalised least squares, to analyse
supernova data. We first calibrate these techniques using near-ideal mock data and versions of the PantheonPlus data, and compare their performance with
Bayesian methods. We find that with near-ideal mock data, Jackknife can yield better constraints. We then apply these methods to constrain parameters of flat $\Lambda$CDM, $\Lambda$CDM, flat $w$CDM, $w$CDM, and flat $w_0\,w_a$CDM models from the PantheonPlus and SH0ES (PPS) data. We observe that constraints obtained with different techniques for three- and four-parameter models are largely consistent. We also find that the Hubble tension is less significant with constraints from the Jackknife. For instance, we find that Jackknife estimates $h\,=\,0.743\,\pm\,0.029$ from PPS data, making the Planck value well within $3\sigma$. Moreover, we estimate $h\,=\,0.678\,\pm\,0.052$ from PantheonPlus data when we only consider sources with $z > 0.01$, in which case there is no tension with the Planck estimate. These results highlight the importance of using multiple techniques while analysing data and warrant further investigation.
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All authors Roshna K, Nikhil Fernandes, P Praveen, V. Sreenath