Astrophysics of Galaxies
C3PO: A Ly{\alpha} Emitting Galaxy at $z \sim 9$
Weida Hu, Casey Papovich, Taylor A. Hutchison et al. (+6 more)
We present deep, $>10$ hr, JWST NIRSpec G140M and G395M observations of a previously known
galaxy C3PO-8447 at $z=8.99781$. Our new NIRSpec data from the Carbon-3 plus Oxygen (C3PO) survey detect Ly$\alpha$ emission with an escape fraction of $1.5\pm0.3\%$ and a velocity offset of $210\pm80$ km s$^{-1}$, making C3PO-8447 the third Ly$\alpha$ emitting
galaxy confirmed at $z\gtrsim 9$. The
galaxy has a low stellar mass of $2.2\pm0.1\times 10^7\ M_\odot$, a young stellar age of $1.6\pm0.2$ Myr, and a low oxygen abundance of $12+\log(\mathrm{O/H}) = 7.50\pm0.08$. UV diagnostic diagrams incorporating the C IV, O III], and C III] emission lines indicate that the ionization of C3PO-8447 is dominated by the recent starburst. The low Ly$\alpha$ escape fraction of C3PO-8447 implies that C3PO-8447 resides in a small ionized bubble with radius $R \sim 0.07$ to 0.20 pMpc, which can be produced by C3PO-8447 alone. We find no evidence for either a large-scale
galaxy overdensity around C3PO-8447 or a significant contribution from nearby
galaxies to its ionizing
photon budget. Taken together, these results suggest that C3PO-8447 likely represents an ionized bubble powered by a single low-mass, vigorously
star-forming
galaxy during the early stages of
cosmic reionization.
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All authors Weida Hu, Casey Papovich, Taylor A. Hutchison, Rebecca L. Larson, Pablo Arrabal Haro, Steven L. Finkelstein, Nikko J. Cleri, Lu Shen, Jiayang Yang
Earth and Planetary Astrophysics
Trans-Neptunian Object dynamics even better explained by a stellar flyby after 4.5 Gyr of evolution
Susanne Pfalzner, Frank W. Wagner and Marco Bischoff
The Trans-Neptunian objects (TNOs) formed together with the
planets from a flat disc of gas and dust but now orbit the Sun mostly on inclined, eccentric orbits. One explanation for the TNOs' orbits is a close flyby of another
star. One with a mass of $M_p =$0.8 Msun at $q_p =$ 110 au and $i_p =$70{\deg} fits the observations. However, such close encounters were more frequent when the Sun was young and still part of its birth cluster. Assuming that the flyby happened then, we use numerical $N$-body simulations to model how the TNOs' orbits changed due to interactions with the
planets over the 4.56 Gyr since the Sun formed. We find that the cold Kuiper belt region lost about 80% and the hot Kuiper belt population about 40% of its initial population. About 7% –8% of the TNOs were injected into the
planet region, but almost all (99%) were ejected afterwards. By contrast, the orbital parameters of distant Sedna-like objects ($q >$60 au) remained basically unchanged. Surprisingly, in sum, these changes improve the fit to the observed TNO population even more, strengthening the argument for a close flyby to the Solar System. The remaining differences concern the location of the cold population and the inclination distribution of the Sedna population. We discuss possible reasons and steps to resolve these issues.
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Earth and Planetary Astrophysics
Effect of stellar spot-only spectral lines in high-resolution transit spectroscopy
W. Dethier, E. Cristo, O. D. S. Demangeon et al. (+3 more)
We investigate how a representative single spectral line present only in a stellar spot can introduce distortions in high-resolution planetary absorption spectra. Specifically, we assess whether such spot-induced features may resemble planetary atmospheric absorption and the observational or stellar conditions under which they become significant. Using the SOAPv4 code, we simulated transit observations of an atmosphere-less
planet across a
star with a spot containing an additional absorption line compared to the photosphere's spectrum. Two systems were modelled: a close-in Jupiter-sized
planet and a distant Earth-sized
planet transiting a Sun-sized
star. We varied the stellar rotation period and the spot size, and ensured that the
planet transits the spot. Spectral lines were idealised Gaussians to isolate the impact of the spot-specific feature. We show that a single stellar spot line can generate spurious features in the absorption spectrum. These features contaminate the absorption spectrum in ways that may lead to misinterpretation if not accounted for. For Jupiter-sized
planets with short transits, the features are mainly emission-like, but can nonetheless dampen a potential true atmospheric absorption signature. For Earth-sized
planets with long transits, the distortion is mainly absorption-like and could be interpreted as planetary absorption. These results highlight the importance of accounting for stellar heterogeneity and activity in the analysis of high-resolution absorption spectra.
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All authors W. Dethier, E. Cristo, O. D. S. Demangeon, J. P. Lucero, N. C. Santos, B. Tessore
Earth and Planetary Astrophysics
Dynamically favorable hosts for submoons around Jupiter and Saturn
Ryan Dahoumane, Valéry Lainey and Kevin Baillié
The long-term stability of small bodies orbiting natural satellites (submoons) in the Solar System has been previously investigated using an analytical approximation of a three-body problem, focusing mainly on tidal forces and neglecting other perturbations. This approach suggests that submoons around most of the regular satellites in the Solar System could be stable. However, no such object has been detected to date. In this work, we extend these previous results by numerically testing the survival of submoons around a large number of satellites of Jupiter and Saturn. Our goal is to rank the satellites of Jupiter and Saturn according to how dynamically favorable they are for submoon survival over the simulated timescales. For each regular or irregular satellite considered, we performed 130 separate N-body integrations, each containing one hypothetical submoon with a different initial semimajor axis and inclination. From the 1 Myr survival fractions, we rank the satellites according to their dynamical favorability for submoon survival over the simulated timescale. We find that, after 1 Myr, the satellites with the highest survival fractions (above 30%) are Iapetus ($\approx 37\%$), Titan ($\approx 35\%$), Rhea ($\approx 32\%$), Phoebe ($30\%$), Callisto ($\approx 34\%$), and Ganymede ($30\%$). Rather than providing absolute probabilities for the existence of submoons, these survival fractions identify the most dynamically favorable hosts. Iapetus, Titan, Rhea, Phoebe, Callisto, and Ganymede are the most dynamically favorable submoon hosts among the tested satellites.
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Astrophysics of Galaxies
Bright star-forming galaxies naturally forming at z>10 in the Shark semi-analytic model
Claudia D.P. Lagos, Angel Chandro-Gomez, Chris Power et al. (+1 more)
The James Webb Space
Telescope (JWST) has unveiled the existence of numerous z>10 bright ultraviolet (UV)
galaxies, potentially challenging
galaxy formation models in a Lambda Cold Dark Matter (LCDM) universe. Modifications to
star formation and stellar feedback models have been suggested to alleviate the tension. However, the fundamental challenge is to design a
galaxy formation model that simultaneously reproduces observations from z=0 to those at the highest
redshifts. Here, we present predictions from the Shark semi-analytic model of
galaxy formation, which is tuned to reproduce the z=0 universe. We show that the same model is capable of reproducing the current UV luminosity function constraints even up to z=17 without the need to invoke variations in the baryon physics model. This model is also capable of reproducing reasonably well the stellar mass function
evolution from z=0 to z=10 and the
cosmic star formation rate (SFR) density at 0<z<15, again with the same baryon physics and parameters. The key to the success of Shark is the triggering of starbursts by violent disk instabilities included in the model, which leads to an increase in the variance of the UV luminosity with increasing
halo mass at z>10. We demonstrate that without this mechanism,
galaxies are not bursty enough in the model to reproduce the observations at z>10.
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All authors Claudia D.P. Lagos, Angel Chandro-Gomez, Chris Power, Aaron S.G. Robotham
Astrophysics of Galaxies
Magnetic Fields in Massive Star-forming Regions (MagMaR). IX. Radiative Torque Alignment and Disruption in NGC6334I
Vineet Rawat, Thiem Hoang, Patricio Sanhueza et al. (+18 more)
Intense radiation from high-mass
stars is expected to significantly affect dust grain
alignment and
evolution through RAdiative Torques (RATs). We investigate this effect in a massive
star-forming region, NGC6334I, using 1.2 mm dust continuum polarization observations from the Atacama Large Millimeter/submillimeter Array. The polarization fraction spans from $\lesssim1\%$ to $\sim10\%$ and decreases with increasing column density, remaining below $2\%$ in dense cores despite high temperatures ($\sim100$ K), where efficient grain
alignment by RATs is expected. We investigate how grain
alignment, grain growth, grain disruption, B-field tangling, and local physical conditions affect the polarization properties of MM1, MM2, MM3, and their surroundings. Polarization angle dispersion shows that B-field tangling contributes to depolarization at moderate densities but cannot fully explain the lowest polarization fractions. Using RAT-based grain
alignment and polarization modeling, we find that reduced
alignment efficiency and high optical depth reproduce the low polarization in the densest regions. MM2 shows evidence of grain growth, with maximum grain sizes $a_{\max}\sim0.35-1.0~\mu$m, while MM1 exhibits smaller values of $\sim0.35-0.50~\mu$m. Accounting for optical depth increases the inferred grain sizes in MM1 to $\sim1.0-2.0~\mu$m. Analytical estimates of radiative torque disruption from the intense outburst suggest that micron-sized grains in high-temperature, moderate-density regions can fragment into submicron grains. Alternatively, high optical depth may also explain the low polarization in the densest regions even in the presence of micron-sized grains. Incorporating the B-field inclination effect indicates a transition from predominantly plane-of-sky fields at low densities to more line-of-sight-aligned configurations at high densities.
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All authors Vineet Rawat, Thiem Hoang, Patricio Sanhueza, Ian W. Stephens, Manuel Fernández López, Paulo Cortés, Jihye Hwang, Junhao Liu, Kaho Morii, Josep Miquel Girart, Ji-Hyun Kang, Yu Cheng, Shanghuo Li, Luis A. Zapata, Eun Jung Chung, Fernando A. Olguin, Huei-Ru Vivien Chen, Piyali Saha, Chakali Eswaraiah, Qizhou Zhang, O.R. Jadhav
High Energy Astrophysical Phenomena
Gamma-Ray Bursts and Optical Brightness: Insights from Swift Satellite
Istvan I. Racz, Yasmin Nehme and Lajos G. Balazs
During the examination of optical properties of gamma-ray bursts (GRBs) measured during the life of the Neil Gehrels Swift Observatory satellite, significant discoveries were made. While the satellite measures gamma, X-ray, and optical data simultaneously, in many cases, only an upper limit is established in the optical domain. Hence, survival analysis, a.k.a. dependability modelling, was necessary, serving as a tool for studying samples where some cases are bound only by the upper limit, as mentioned earlier. This method is used to analyse
datasets that may have upper or lower bounds rather than precise observations, but nevertheless contain relevant information. It was previously established that the duration, gamma fluence, and peak flux all have a substantial effect on the optical brightness distribution, probably due to the energy of the beam from the GRB's central engine. However, after analysing more than 200 data points, we no longer see this association. This disagreement shows that the previously reported impact may not be as significant as previously derived, needing more research to better understand the underlying processes that determine the optical brightness in connection to gamma-ray properties.
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High Energy Astrophysical Phenomena
The Jet Properties and Accretion Regime for the Blazar Sequence
Qingchen Long
The puzzling bimodality displayed by blazars on the broad-band spectral indices ($\alpha_{\rm ro}-\alpha_{\rm ox}$) plane is still an open question. To investigate its physical origin, we compiled a sample comprising 136 flat-spectrum
radio quasars (FSRQs), 64 low-synchrotron-peaked BL Lac objects (LBLs), 39 intermediate-synchrotron-peaked BL Lac objects (IBLs), and 105 high-synchrotron-peaked BL Lac objects (HBLs). Our results show that (FSRQs+LBLs)$\rightarrow$IBLs$\rightarrow$HBLs follow a \reflectbox{$\angle$}-shaped evolutionary sequence on the $\alpha_{\rm ro}-\alpha_{\rm ox}$ plane, with the average 5\,GHz
radio Doppler factor, jet power, and
accretion Eddington ratio decreasing along this \reflectbox{$\angle$}-shaped track. Additionally, the distributions of $\alpha_{\rm ox}$ exhibit only slight differences among blazar subclasses, whereas those of $\alpha_{\rm ro}$ and $\alpha_{\rm rx}$ differ significantly. Our results can be naturally explained if the distribution of blazars on the $\alpha_{\rm ro}-\alpha_{\rm ox}$ plane is regulated by the
accretion rates and the Doppler beaming effect across different bands ($\delta_i^{q_i}/\delta_j^{q_j}$). However, $\delta_i/\delta_j$ plays a pivotal role in the distribution, while jet shape ($q=2(3)+\alpha_\nu$) and spectral indices ($\alpha_\nu$) play a minor role. Our results suggest that FSRQs+LBLs are strong-jet sources coupled with radiatively efficient
accretion, and their jets are accelerated to a larger distance from the core and still maintain relativistic speeds down to the
radio region; HBLs are weak-jet sources coupled with radiatively inefficient
accretion, and their jets may begin to decelerate in the optical region and exhibit sub-relativistic speeds as they propagate to the
radio region. IBLs are regarded as transitional objects between FSRQs+LBLs and HBLs.
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Astrophysics of Galaxies
Constraints on mu-variations from the methanol CH3OH thermal lines in the Galaxy at galactocentric distances of 1.5 < D_GC < 13 kpc
A. I. Shtein, J. S. Vorotyntseva and S. A. Levshakov
In this study, constraints are set on hypothetical variations of the fundamental physical constant mu = m_e/m_p - the electron-to-
proton mass ratio - based on thermal emission lines of E-methanol (CH3OH) in the 216-220 GHz frequency range. Molecular spectra toward seven massive clouds located across a wide range of galactocentric distances (1.5 < D_GC < 13 kpc) have been analyzed. The obtained weighted mean value <Delta mu/mu> = (0.5+/-0.5)*10^(-7) does not indicate statistically significant changes in mu at the 1 sigma confidence level of 5*10^(-8), which is in good agreement with previously established upper limits in a number of molecular clouds in the Galactic disk.
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Instrumentation and Methods for Astrophysics
Reconstruction of Shower-like Events in NEON Using Likelihood and Graph Neural Network Methods
Sujie Lin, Weiqin Huang, Yihan Liu et al. (+3 more)
The
Neutrino Observatory in the Nanhai (NEON) is a proposed deep-sea
neutrino telescope deployed in the South China Sea. Accurate reconstruction of shower-like events is crucial for
neutrino energy measurements and multi-messenger astronomy, yet it poses significant challenges due to seawater optical attenuation, irregular detector geometry, and substantial $^{40}\mathrm{K}$ ambient background. In this work, we present the first comprehensive reconstruction framework for shower-like events in NEON, encompassing both a physics-driven maximum likelihood estimation (MLE) method and a data-driven Graph Neural Network (GNN). The traditional MLE framework integrates spatial-isochronic hit selection, vertex reconstruction via time-residual M-
estimator minimization, and decoupled directional and energy estimation based on pre-computed
photon distribution tables. Physical calibrations, including PMT angular acceptance, hit-level time slewing corrections, and an effective line-source shower extension, are incorporated into the likelihood formulation. In parallel, a two-stage GNN is developed to capture intra-DOM PMT correlations and distance-weighted inter-DOM topological patterns. Simulation studies show that the MLE method achieves an overall median angular resolution of $4.19^\circ$ and an energy resolution of 25%-37% over 1 TeV to 1 PeV with negligible systematic bias. The GNN further improves reconstruction fidelity in the low-to-intermediate energy regime, achieving a median angular resolution of $1.8^\circ$ at 30 TeV and an energy resolution of $\sim$ 20% between 40 and 300 TeV. Based on these reconstruction performances, the effective area and point-source discovery potential of NEON are evaluated. This framework establishes an essential reconstruction
benchmark for NEON and provides practical methodologies for future next-generation deep-sea
neutrino telescopes.
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All authors Sujie Lin, Weiqin Huang, Yihan Liu, Chengyu Shao, Lili Yang, Huiming Zhang
Astrophysics of Galaxies
Search for intranight optical variability in a large sample of intermediate-mass black holes
Himanshu Sharma, Gopal-Krishna, Vibhore Negi et al. (+3 more)
Using the extensive archival database of the Zwicky Transient Facility (ZTF) survey, we have investigated intranight optical variability (INOV) in a large sample of low-mass active galactic
nuclei (LMAGN) powered by intermediate-mass black holes (IMBHs). After applying a sequence of well-motivated selection filters, we constructed an unbiased, representative sample of 62 IMBHs for which $r$-band intranight photometric sequences are available in the ZTF database, yielding 167 sessions with a minimum duration of 2 h. By performing aperture photometry on the sequence of exposures in each session, we derived differential light curves (DLCs) of the target LMAGN relative to two carefully selected non-varying comparison
stars monitored simultaneously with the LMAGN in the same exposure sequence. Application of the widely used test based on $F$-statistics to all these DLCs revealed no case of statistically significant INOV. We discuss this result for the present large sample of LMAGN in the context of an earlier report of INOV detections in another, albeit much smaller and differently selected, sample of LMAGN that had been monitored in targeted observations.
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All authors Himanshu Sharma, Gopal-Krishna, Vibhore Negi, Hum Chand, Krishan Chand, Anshul Kumar Sharma
Instrumentation and Methods for Astrophysics
Night-sky emission correction techniques for high-resolution spectroscopy: Demonstration with NIRPS
Avidaan Srivastava, François Bouchy, Xavier Dumusque et al. (+54 more)
Ground-based spectrographs operating in the near-infrared (NIR) regime are hampered by various absorption and emission features of Earth's atmosphere. While considerable
attention has been paid to mitigating telluric absorption, correcting telluric emission features remains non-trivial and can significantly affect the observation of faint targets. We aim to develop and implement automated
algorithms for sky background emission correction in the context of high-resolution spectroscopy. These empirical-based
algorithms have been officially integrated into both NIRPS data reduction pipelines: NIRPS DRS and APERO DRS. Designed for flexibility, these techniques can be incorporated into the reduction workflow of any high-resolution spectrograph to improve the radial velocity (RV) performance. In our approach, a reference sky spectrum is first created by deep-stacking NIRPS sky calibration frames on a common wavelength grid and calculating the weighted median flux per pixel, separately for both the high-accuracy and high-efficiency instrument modes. This process is repeated for all spectral orders and for both the object and sky-calibration fibres: fibre A and fibre B, respectively. In this reference sky spectrum, the sky emission lines can be identified and used to construct a static library. During the data reduction process, the emission features in the library are individually scaled in terms of flux using two distinct techniques, each specific to the two DRS pipelines. Finally, they are locally subtracted from the science observations to minimise their noise contribution to the final spectrum. We find that the correction
algorithms significantly improve the RV measurements obtained using both the cross-correlation function and line-by-line techniques, enabling NIRPS to achieve submetre-per-second precision in the NIR. The techniques have been successfully validated and demonstrated.
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All authors Avidaan Srivastava, François Bouchy, Xavier Dumusque, Étienne Artigau, René Doyon, Neil J. Cook, Danuta Sosnowska, Flavie Bélanger, David Lafrenière, Frédérique Baron, Lison Malo, Susana C. C. Barros, Björn Benneke, Xavier Bonfils, Marta Bryan, Ryan Cloutier, Nicolas B. Cowan, Elisa Delgado-Mena, Xavier Delfosse, David Ehrenreich, Pedro Figueira, Jonay I. González Hernández, Izan de Castro Leão, Christophe Lovis, Bruno L. Canto Martins, Lucile Mignon, Christoph Mordasini, Francesco Pepe, Rafael Rebolo, Jason Rowe, Nuno C. Santos, Damien Ségransan, Alejandro Suárez Mascareño, Jose Renan De Medeiros, Stéphane Udry, Diana Valencia, Gregg Wade, Romain Allart, Vincent Bourrier, Pedro Branco, Charles Cadieux, Gaspare Lo Curto, Yolanda G. C. Frensch, Jonathan Gagné, Roseane de Lima Gomes, Nicole Gromek, Vigneshwaran Krishnamurthy, Pierrot Lamontagne, Yuri S. Messias, Khaled Al Moulla, Dany Mounzer, Nicola Nari, Léna Parc, Atanas K. Stefanov, Thomas Vandal, Drew Weisserman, Joost P. Wardenier
Instrumentation and Methods for Astrophysics
3.5-meter Segmented-Mirror Robotic Space Telescope Mission White Paper V. Key Scientific Mission: Compact-Object Time-Domain Science
Juhan Kim, Yong-Woo Kang, Sang Hyun Lee et al. (+22 more)
An isolated compact object retains the point-source resolving power of the space-based slitless spectrograph. The baseline wavelength range is 0.2–1.5 $\mu$m. The planning baseline uses $R \simeq 1000$ for broad and faint transient spectra and reserves selectable bands at $R \simeq 5000$ for
accretion-disk profiles, velocity structure, and precision line ratios. Broad features can be measured after binning the native $R \simeq 5000$ data to lower resolution. Rapid-response spectroscopy follows gravitational-wave counterparts and kilonovae from hours to days. Repeated spectra of dwarf novae and compact binaries trace
accretion state and orbital phase, while uninterrupted imaging of white dwarfs measures pulsation frequencies. The program combines mission-based monitoring with external alerts, including KGMT transient detections. The instrument study must preserve calibrated throughput to 2.70 $\mu$m and evaluate a 3.0 $\mu$m operational band edge, with 2.5 $\mu$m retained as the formal engineering off-ramp. Mid-infrared imaging is not part of the adopted compact-object baseline.
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All authors Juhan Kim, Yong-Woo Kang, Sang Hyun Lee, Jeong-Yeol Han, Sungwook E. Hong, Bongkon Moon, Donguk Song, Juhyung Kang, Myeong-Gu Park, Sang Chul Kim, Chung-Uk Lee, Sangmo Tony Sohn, Arman Shafieloo, David Parkinson, Hong Soo Park, Dohyeong Kim, Chan Park, Jungjoo Sohn, Young-Beom Jeon, Jong-Hak Woo, Hyung Mok Lee, Hong Bae Ann, Myungkook James Jee, Mansoo Choi, Changbom Park
Instrumentation and Methods for Astrophysics
3.5-meter Segmented-Mirror Robotic Space Telescope Mission White Paper IV. Key Scientific Mission: Solar-System Small Bodies and Planetary Defense
Juhan Kim, Yong-Woo Kang, Sang Hyun Lee et al. (+22 more)
The baseline 0.2–1.5 $\mu$m observatory provides rapid-response astrometry, visible and near-infrared taxonomy, rotation and phase curves, recovery, and long-arc orbit improvement for near-Earth objects and other small bodies. The instrument study also evaluates calibrated throughput to 2.70 $\mu$m with a 3.0 $\mu$m operational band-edge goal. A reduction to 2.5 $\mu$m remains the formal engineering off-ramp if thermal, detector, cooling, mass, power, or cost constraints require it. The 3.5-meter Segmented-Mirror Robotic Space
Telescope does not carry a mid-infrared channel. Coordinated ground-based mid-infrared
telescopes provide the thermal fluxes required to infer diameter and albedo, while the space mission supplies contemporaneous reflected-light measurements and observing geometry. The program combines recovery, physical characterization, orbit refinement, and covariance-based hazard assessment. Its CODES dynamics system and OGFinder-to-OpenOrb processing path connect measured astrometry to reproducible orbit solutions and close-approach predictions.
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All authors Juhan Kim, Yong-Woo Kang, Sang Hyun Lee, Jeong-Yeol Han, Sungwook E. Hong, Bongkon Moon, Donguk Song, Juhyung Kang, Myeong-Gu Park, Sang Chul Kim, Chung-Uk Lee, Sangmo Tony Sohn, Arman Shafieloo, David Parkinson, Hong Soo Park, Dohyeong Kim, Chan Park, Jungjoo Sohn, Young-Beom Jeon, Jong-Hak Woo, Hyung Mok Lee, Hong Bae Ann, Myungkook James Jee, Mansoo Choi, Changbom Park
Astrophysics of Galaxies
Evolution of Virial Clouds - II: From the Formation of First Stars up to their Explosion
Noraiz Tahir, Asghar Qadir, Francesco De Paolis et al. (+1 more)
The existence of cold gas and dust clouds close to the
cosmic microwave background (CMB) temperature was proposed as a potential repository for a significant fraction of the missing baryons in galactic
halos. While the
evolution of the virial clouds from the last scattering surface (LSS) ($z=1100$) up to the formation of Population III (Pop III)
stars ($z=48$) was studied in [N. Tahir, A. Qadir, M. Sakhi, & F. De Paolis, The Euro. Phys. Jour. C 81, 827 (2021)] (Paper I), the subsequent
evolution during the epoch of the first
stars remained unexplored. In the present work, we investigate the second evolutionary phase of the virial clouds, covering the
redshift range $48 \gtrsim z \gtrsim 10$. We develop a comprehensive model incorporating the coupled thermal, chemical, and dynamical
evolution of the cloud, including CMB heating, adiabatic compression due to gravitational contraction, H$_2$ and metal-line cooling, and feedback from Pop III
supernovae. Solving the coupled ordinary differential equations (ODE) numerically, we find that the cloud cools monotonically from $137$~K to $41.5$~K, contracts from $120$~pc to $89.8$~pc, and becomes enriched in metals and molecular hydrogen, while the cooling rate dominates the heating rate throughout the
evolution.
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All authors Noraiz Tahir, Asghar Qadir, Francesco De Paolis, Noor Fatima
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Introducing SINFONIA: Symplectic, slimplectic and Magnusian (Neural) Flows for Orbital Numerical Integration and Acceleration
Lidia J. Gomes Da Silva
Long-duration gravitational-wave modelling must resolve fast orbital motion together with slow dissipative
evolution while preventing small numerical errors from accumulating into secular phase drift. Here we ask whether the finite-time
evolution map itself can be learned as an explicit, differentiable, structure-preserving object and then repeatedly composed through a complete inspiral. We construct three neural-flow architectures: a symplectic and slimplectic flow on Galley's doubled phase space, [SINFONIA-J0]; a Taylor-anchored flow, [SINFONIA-J1]; and a Magnusian flow that learns the finite-time dissipative correction in the interaction picture, [SINFONIA-J2]. Applied to a 2.5PN
neutron-
star inspiral, all three expose the same controlling mechanism: long-time accuracy is governed not by pointwise map error alone, but by its signed projection onto a single secular channel fixed by energy–angular-momentum balance. Encoding this structure allows the learned maps to remain accurate through $10^{2}$–$10^{5}$ window compositions to coalescence at timesteps of a full orbital period and beyond, reaching chained phase errors orders of magnitude below a
benchmark slimplectic integrator at lower cost. The same secular structure can also be exploited for physics inference: when the channel is left unconstrained, the accumulated phase retains enough information to recover an un-modelled dynamical-friction-like force, both parametrically and as a learned function of separation. Network-off controls isolate the contribution of learning from the analytic structure already built into each map. These results establish a proof of concept for structure-preserving learned
evolution maps as tools for fast long-duration integration and physics inference in gravitational-wave source modelling.
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Solar and Stellar Astrophysics
NGC 1901: A new benchmark cluster for gyrochronology in the TESS Southern continuous viewing zone
Mara Bernizzoni, Timothy R. Bedding, Prasad Mani et al. (+5 more)
We use Gaia DR3 astrometry and TESS time-series photometry to study NGC 1901, a sparse open cluster in the TESS Southern continuous viewing zone, that has been neglected due to its proximity on the sky to the Large Magellanic Cloud. We refine its membership list and measure rotation periods for 32 high-confidence rotating
stars. By applying the gyro-interp empirical model, we calculate a gyrochronal age of 830 $\pm$ 50 Myr. Because NGC 1901 possesses a sub-solar
metallicity of [Fe/H]$\approx -0.11$, its excellent agreement with empirical models suggests that temperature-period relations mitigate
metallicity effects for Sun-like
stars. Our results place NGC 1901 in the gap between the
benchmark open clusters Praesepe (670 Myr) and NGC 6811 (1 Gyr). We find that the rotation sequence exhibits significant
spin-down stalling in late K dwarfs, supporting models of core–envelope recoupling. Furthermore, our findings provide constraints for the cluster's structural
evolution, including its recently identified tidal tail and corona. This study establishes NGC 1901 as a new
benchmark for calibrating the next generation of gyrochronal models.
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All authors Mara Bernizzoni, Timothy R. Bedding, Prasad Mani, Luke G. Bouma, Courtney L. Crawford, Jason Lee Curtis, Benjamin T. Montet, Samir Nepal
Solar and Stellar Astrophysics
Bifurcations in the Heliosphere: Global-scale Coronal Pseudostreamer Evolution and the Creation of Secondary Heliospheric Current Sheets
Lizet S. Casillas, Benjamin J. Lynch, Victor Réville et al. (+2 more)
The heliospheric current sheet (HCS) is the boundary between open
magnetic fields of opposite polarity in the solar wind that connect back to their respective open flux regions in the corona. The HCS is often described as a disc-like sheet warped by the combined effects of the inclination of the
magnetic equator on the Sun, solar rotation, and solar wind expansion. The HCS is an extension of the helmet streamer belt-the closed-flux region resulting from the global dipole component of the observed photospheric
magnetic field. In the absence of a strong dipole, a dominant quadrupole can result in two separate HCSs. Here we report on a set of idealized, axisymmetric solar wind simulations designed to study the transition of the single-HCS corona and inner heliosphere into a multiple-HCS configuration, run with the WindPredict-AW PLUTO MHD code. We systematically vary the relative strengths of the dipole/quadrupole contributions to the global field and show this results in the formation of a large-scale, closed-flux pseudostreamer that interacts with the ambient solar wind. We find that when the dipole and quadrupole magnitudes are approximately equal, our model corona can oscillate between a one- and two-HCS configuration on the timescale of days-to-weeks. We characterize the
plasma dynamics of the transition of a global-scale pseudostreamer into a localized, secondary helmet-streamer belt with its own HCS surrounding a newly-opened, opposite-polarity coronal hole. We discuss the implications of our results for solar cycle
evolution and the dynamic coupling of the highly structured corona and inner heliosphere.
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All authors Lizet S. Casillas, Benjamin J. Lynch, Victor Réville, Olga A. Panasenco, Marco Velli
Astrophysics of Galaxies
Turbulent gas-rich discs at high redshift: the origin of early massive stellar bars
Joss Bland-Hawthorn, Thor Tepper-Garcia, Chris Hamilton et al. (+4 more)
Recent observations combining the power of ALMA and JWST have revealed large ($3-7$ kpc), massive ($3-10\times10^{10}\,\mathrm{M}_\odot$) stellar bars at $z=4-5$ when the Universe was only 1.2-1.6 Gyr old. At this early epoch, the host
galaxy was baryon-dominated (typically 75% gas, 25%
stars) within the observed extent of the disc ($8-15$ kpc). Using NEXUS $N$-body/hydrodynamic simulations, we show that such bars can form promptly (400$-$800 Myr), provided the disc mass fraction is high ($f_{\rm disc}\gtrsim 70\%$) and the bar is gas-dominated at the time of its formation, consistent with the observations. In this limit, gas-free bars are unstable to vertical bending modes, but a dominant gas component suppresses this instability. Unlike massive bars in the local Universe, these early bars were sites of vigorous
star formation, as we show. Remarkably, for gas-rich models with $f_{\rm gas}\lesssim60\%$, the bars develop X-shaped boxy bulges; at higher gas fractions ($f_{\rm gas}> 60\%$),
diffusion suppresses resonant orbit trapping and the emerging bar collapses within 1 Gyr to form a classical bulge. The bar formation time, length, mass, and $m=2$
Fourier amplitude are all inversely related to $f_{\rm gas}$. We present a simple analytic model for how
stochastic forcing shifts the bar onset time, defined as the time at which the growing bar amplitude reaches a specified threshold.
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All authors Joss Bland-Hawthorn, Thor Tepper-Garcia, Chris Hamilton, Johan M. Villa-Alatorre, Oscar Agertz, Takafumi Tsukui, Ken Freeman
High Energy Astrophysical Phenomena
Radiative Efficiency Enhancement by Electromagnetic Energy Dissipation in Strongly Magnetized Supercritical Accretion Flows around Kerr Black Holes
Hiroyuki R. Takahashi, Ken Ohsuga, Ryohei Kobayashi et al. (+4 more)
We investigate how black hole
spin and the amount of
magnetic flux affect electromagnetic energy dissipation and radiation transport in supercritical
accretion flows. For this purpose, we perform general relativistic radiation magnetohydrodynamic simulations of MAD and SANE
accretion flows with different black hole
spins. In the high-
spin MAD model, we find that a fraction of the electromagnetic energy extracted by the Blandford–Znajek mechanism is dissipated near the disk surface in the vicinity of the black hole. This dissipation significantly contributes to the generation of radiative energy and enhances the luminosity. The time-averaged radiative efficiency reaches $\eta_{\rm rad}=0.60$, which is much larger than $0.088$ for the non-spinning black hole case and $0.21$ for the weak-
magnetic-flux case, corresponding to the SANE state. As a result, the effective trapping radius, defined as the radius at which the outward radiative luminosity becomes equal to the inward radiative luminosity, is $r_{\rm trap}=2.5r_{\rm g}$, comparable to the ISCO radius. This value is significantly smaller than $12r_{\rm g}$ for the non-spinning case and $8.5r_{\rm g}$ for the SANE state. These results suggest that the amount of
magnetic flux accumulated on the black hole can affect the radiative properties of supercritical
accretion flows and should therefore be considered, in addition to black hole mass,
spin, and mass
accretion rate, when interpreting observed luminosities and spectra.
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All authors Hiroyuki R. Takahashi, Ken Ohsuga, Ryohei Kobayashi, Akihiro Inoue, Yuta Asahina, Akira Nukada, Taisuke Boku
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Non-extensive entropy signatures in compact star
B. N. Jayawiguna, M. H. Al Ghifari, A. Rohim et al. (+1 more)
The non-extensive
entropy models applied to the black-hole horizon are connected to the generalized Einstein–
Hilbert action, $f(R)$, via the Wald
entropy formalism. We demonstrate that
quark star configurations characterized by the MIT bag model under this modified
gravity approach conform to the observational lower and upper bounds established for compact objects linked to HESS J1731$-$347 and GW190814. Furthermore, we assess the effective energy conditions and corresponding speed of sound to evaluate the physical plausibility and stability of the stellar configurations. All non-extensive
entropy models studied satisfied these conditions. Our findings show that the exotic compact objects offer a compelling and credible framework for exploring aspects of non-extensive
entropy models, such as the Barrow, Tsallis-Cirto, and Rényi formalisms, and vice versa.
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All authors B. N. Jayawiguna, M. H. Al Ghifari, A. Rohim, A. Sulaksono
Astrophysics of Galaxies
CLAS+: A large catalog of Changing-Look AGN candidates selected through S-PLUS narrow-band photometry
L. Nakazono, L. L. Oliveira, R. R. Valença et al. (+11 more)
Changing-look active galactic
nuclei (CLAGN) exhibit rapid spectral transitions on timescales of months to years, challenging standard AGN unification models and providing unique insight into
accretion-disk variability and obscuration processes. Despite their scientific importance, systematic searches for CLAGN remain limited by the scarcity of multi-epoch spectroscopy and the difficulty of constructing large samples efficiently. We introduce CLAS+, a catalog constructed by comparing synthetic photometry derived from DESI DR1 and SDSS DR17 spectra with contemporaneous narrow-band imaging from the S-PLUS survey. Applying our pipeline to a parent sample of 98,139
quasars, we select high-confidence CLAGN candidates above a threshold of reduced chi-squared $\chi_r^2 > 15$. We identify 3,554 strong CLAGN candidates, corresponding to 3.6% of the parent sample. This selected fraction is conditional on the adopted criterion and should not be interpreted as an intrinsic CLAGN occurrence rate. Cross-matching with existing CLAGN compilations shows that CLAS+ identifies a large population of previously unreported high-priority candidates (3,481). Among the spectroscopic–photometric comparisons with reliable temporal classification, 40% are classified as photometric turn-on, 41% as intermediate, and 19% as turn-off. We also find an apparent
redshift dependence in the relative fractions, with photometric turn-on candidates becoming more common at higher
redshifts within the CLAS+ selected sample. Therefore, narrow-band photometry provides a powerful and efficient alternative to purely spectroscopic searches for identifying CLAGN candidates at scale. CLAS+ substantially expands the known CLAGN candidate population and provides a valuable target list for future spectroscopic follow-up and time-domain studies with facilities such as Rubin/LSST.
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All authors L. Nakazono, L. L. Oliveira, R. R. Valença, P. Sánchez-Sáez, G. Oliveira-Schwarz, N. M. Cardoso, A. L. O'Mill, S. Panda, E. Telles, R. Demarco, W. Schoenell, T. Ribeiro, A. Kanaan, C. Mendes de Oliveira