Peer Revenue Now accepting positions

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 10 June

Cosmology and Nongalactic Astrophysics

Nonminimal couplings and preheating effects in $R^2$-Higgs inflation after ACT and SPT data

Haneesh Gonuguntla, Tanmoy Modak and Arnab Samanta

We study the effects of dimension-four and dimension-six nonminimal Higgs couplings to the Ricci scalar $R$ in the $R^2$-Higgs inflation model in light of the recent ACT and SPT observations. We show that the dimension-six operators $|\Phi|^2 R^2$ and $|\Phi|^4 R$ can accommodate the enhanced scalar spectral index $n_s$ preferred by the combined CMB+BAO analyses. Using a doubly covariant formalism, we find that the same region of parameter space that explains the observed value of $n_s$ can also induce rapid preheating through the production of the Goldstone modes. If thermalization proceeds efficiently through this preheating mechanism, it may help match the inflationary scale with the CMB reference scale.
Read the full abstract

Solar and Stellar Astrophysics

Building three-dimensional giant stellar models for common envelope simulations

Ron Schreier, Shlomi Hillel and Noam Soker

We build a three-dimensional (3D) red supergiant (RSG) stellar model by transporting a 1D stellar model to a 3D numerical grid, mimicking core nuclear power by depositing energy into an inner shell, and mimicking stellar emission by cooling grid cells with densities below the photospheric density. The goal is to use such models for common envelope evolution (CEE) and grazing envelope evolution simulations. We do not relax the model; rather, we let it perform its natural pulsation. We find that when we mimic photospheric emission by cooling low-density grid cells, the oscillations decay slowly on a timescale much longer than without photospheric cooling. When we mimic both nuclear energy production, by depositing the stellar luminosity in an inner shell above the inert core of the stellar model, and photospheric cooling, the oscillations do not decay; instead, their amplitude slowly increases with time. The main pulsational period is about 1 year, comparable to the stellar dynamical time, suggesting a fundamental radial pulsation mode. The non-spherical structure of the stellar model and rapid low-amplitude temporal variations in the average stellar radius tentatively hint at the presence of non-radial oscillation modes on top of the fundamental radial mode. We also obtain convection, as RSG stars should have. We conclude that energy deposition in the inner envelope at the stellar luminosity and the cooling of the outer low-density numerical cells are a way of preparing a pulsating giant star to simulate CEE and grazing-envelope evolution. This procedure requires no relaxation of the stellar model.
Read the full abstract

High Energy Astrophysical Phenomena

Gamma-Ray Constraints on Heavy Axion-Like-Particle Decays from Fermi-LAT and H.E.S.S. Blazar Spectra

A. Acharyya, F. Aharonian, M. Backes et al. (+118 more)

The propagation of very-high-energy (VHE; $E_{\gamma} \geq 100$ GeV) gamma rays from extragalactic sources is affected by interactions with photons of the extragalactic background light (EBL), resulting in pair production that attenuates the intrinsic gamma-ray flux. This interaction renders the Universe increasingly opaque to VHE photons at high energies and redshifts. New physics scenarios involving axion-like particles (ALPs) could modify this expected optical depth. In particular, ALPs with masses $m_a \sim 10$ eV can decay into two photons over cosmological timescales, thereby contributing to the diffuse EBL. If such ALPs constitute a significant fraction of the dark matter density, their decay would enhance the EBL intensity and consequently increase the gamma-ray optical depth. In this study, we investigate this scenario using a large sample of gamma-ray spectra observed with the High Energy Stereoscopic System (H.E.S.S.) and the Fermi Large Area Telescope. We model the contribution of decaying ALPs to the EBL and assess their impact on the spectra of blazars across redshifts. By comparing these observations with standard EBL models, we place constraints on the properties of heavy ALPs, specifically their mass and photon coupling, and evaluate their viability as a dark matter candidate capable of modifying the gamma-ray transparency of the Universe. From the combined analysis, and under the assumption that ALPs constitute the entire dark matter density, we derive 95% confidence exclusion limits on the photon-ALP coupling down to $g_{a\gamma} \sim 7 \times 10^{-12}$ GeV$^{-1}$ for masses $m_a\sim 15$ eV. These constraints are competitive with existing astrophysical bounds and provide complementary sensitivity to other techniques, closing a previously unconstrained region of parameter space in the $m_a \sim 2.5$-$20$ eV range.
Read the full abstract

All authors A. Acharyya, F. Aharonian, M. Backes, R. Batzofin, Y. Becherini, S. Bisero, M. Böttcher, C. Boisson, J. Bolmont, F. Brun, C. Burger-Scheidlin, T. Bylund, S. Casanova, D. Cecchin Momesso, M. Cerruti, A. Chen, M. Chernyakova, J.O. Chibueze, O. Chibueze, T. Collins, B. Cornejo, G. Cotter, G. Cozzolongo, J. de Assis Scarpin, M. de Naurois, E. de Oña Wilhelmi, A. Deka Baruah, A. Dmytriiev, K. Egberts, K. Egg, C. Escañuela Nieves, K. Feijen, M.D. Filipović, G. Fontaine, S. Funk, S. Gabici, Y.A. Gallant, M. Genaro, P. Geneste, J.F. Glicenstein, P. Goswami, C. Grimaud, L. Heckmann, B. Heß, J.A. Hinton, W. Hofmann, T.L. Holch, M. Holler, M. Jamrozy, F. Jankowsky, I. Jaroschewski, I. Jung-Richardt, D. Kerszberg, B. Khélifi, N. Komin, D. Kostunin, R.G. Lang, S. Lazarević, M. Lemoine-Goumard, J.-P. Lenain, P. Liniewicz, A. Luashvili, J. Mackey, D. Malyshev, D. Malyshev, V. Marandon, M.G.F. Mayer, A. Mehta, M. Meyer, A.M.W. Mitchell, R. Moderski, L. Mohrmann, A. Montanari, E. Moulin, J. Niemiec, L. Olivera-Nieto, M.O. Moghadam, M. Panter, R.D. Parsons, D. Pastuszka Malek, P. Pichard, S. Pita, S. Porras-Bedmar, T. Preis, G. Pühlhofer, M. Punch, A. Quirrenbach, A. Reimer, O. Reimer, H.X. Ren, B. Reville, F. Rieger, G. Roellinghoff, G. Rowell, B. Rudak, K. Sabri, V. Sahakian, A. Santangelo, M. Sasaki, F. Schüssler, J.N.S. Shapopi, W. Si Said, Ł. Stawarz, R. Steenkamp, S. Steinmassl, T. Tanaka, A.M. Taylor, G.L. Taylor, R. Terrier, Y. Tian, T. Unbehaun, C. van Eldik, M. Vecchi, J. Vink, V. Voitsekhovskyi, T. Wach, S.J. Wagner, A. Wierzcholska, M. Zacharias, A. Zech, W. Zhong

High Energy Astrophysical Phenomena

Spectral study of X-ray sources in some galaxies recently observed by Chandra

Amom Lanchenbi Chanu and Anoubam Senorita Devi

With the aim to study the spectral properties of some X-ray sources from recently observed Chandra data, 9 galaxies which have been observed by Chandra ACIS-S during the year 2018 to 2022 have been considered for the present work. 27 sources with net source counts $ \ge$ 100 have been considered. The spectra of all the sources were fitted using two empirical models – an absorbed powerlaw and an absorbed disk blackbody. From their estimated bolometric luminosities, the 27 X-ray sources are categorized as 6 X-ray binaries (XRBs) and 21 Ultraluminous X-ray sources (ULXs). All the six XRBs are found to be in the spectrally hard state ($\Gamma \sim$ 1.52-2.29) which indeed may be due to thermal comptonization. Only one ULX, CXOUJ032251.2-370950 (X-5), was found to be spectrally soft while the remaining 20 ULXs were spectrally hard. The spectral parameters of X-5 with an inner disk temperature (kT$_{in}$) $\sim $ 0.5 keV and an estimated bolometric luminosity, L$_X \sim$ 3.26 $\times$ 10$^{39}$ erg s$^{-1} $ requires a black hole of mass, M$_{BH} \sim$ 137.86$^{+66.62}_{-47.41}$ M$_\odot $ accreting at $ \sim$ 0.19 times its Eddington limit. 8 ULXs, X-4, X-8, X-9, X-10, X-11, X-12, X-20 and X-21, were found to be in the Extremely luminous X-ray sources (ELXs) regime with even their lower limit of luminosity $>$ 10$^{40}$ erg s$^{-1}$. Softening/Hardening of spectra with or without changes in the luminosity were also observed in some ULXs/ELXs. In the hard ELX, X-8, spectral softening with almost consistent luminosity was observed. While in the ULXs X-20 and X-25 spectral softening with increasing luminosity was observed. However spectral hardening with increase in luminosity were observed in the ULXs X-21 and X-26.
Read the full abstract

Solar and Stellar Astrophysics

Protostellar Outflows at the EarliesT Stages (POETS). IX. Magnetohydrodynamic disk winds traced by SO and SO$_2$ in luminous protostars

L. Moscadelli, H. Beuther, A. Sanna et al. (+13 more)

We investigate two massive young stellar objects (YSOs), IRAS21078+5211 and G035.02+0.35, where evidence for magnetohydrodynamic (MHD) disk winds (DWs) has been obtained at scales of 10-100 au through measurements of the 22GHz water maser velocity distribution within the Protostellar Outflows at the EarliesT Stages (POETS) survey. We employ IRAM Northern Extended Millimeter Array and archival Atacama Large Millimeter Array observations of IRAS21078+5211 and G035.02+0.35, respectively, to study kinematics and physical conditions of the corresponding protostellar winds on scales of 100-1000 au using the same molecular tracers. In IRAS21078+5211, the emissions of several molecules, particularly SO, SO2, CH3CN and CH3OH, are distributed along the axis of the radio jet, and present a LSR velocity (Vlsr) gradient transversal to the jet axis. Position-velocity (PV) plots of the SO lines show patterns consistent with Keplerian rotation. The SO2 emission comes from high velocity gas flowing close to the jet axis, while CH3CN and CH3OH present larger radial extension than the S-bearing species. In G035.02+0.35, the same molecules are instead distributed along the major axis of the rotating disk, and their Vlsr gradients consistently trace the disk rotation. The corresponding PV plots present Keplerian profiles. SO is the only molecular species whose emission extends well outside the disk. In both YSOs, the spatial and velocity distributions of SO are consistent with a rotating wind magneto-centrifugally launched from the YSO disk. The comparison with models of molecule formation and excitation in shocks indicates that the different radial extension of the molecular species observed in the protostellar wind of IRAS21078+5211, as well as the lack of molecules, except SO, in the G035.02+0.35's wind, can be explained in terms of a radially extended MHD DW, rather than a compact X-wind.
Read the full abstract

All authors L. Moscadelli, H. Beuther, A. Sanna, M.T. Beltrán, C. Gieser, Th. Henning, P.D. Klaassen, R. Kuiper, S. Leurini, T. Möller, A. Palau, R. E. Pudritz, Á Sánchez-Monge, D. Semenov, J.S. Urquhart, H. Zinnecker

High Energy Astrophysical Phenomena

A Jet from a Nearly Dormant Black Hole

Xiaopeng Cheng, Hai Yang, Jun Yang et al. (+11 more)

Most galaxies host supermassive black holes (SMBHs) that remain weakly accreting or dormant for much of their lifetimes. At the lowest accretion rates, these systems may represent the transition between active nuclei and dormant black holes, but whether they can still launch collimated jets remains unclear. The nuclei in our Galaxy (\sgra) and M31 are key examples of this regime, although no clear jet structure has yet been detected in either source. Here we report multi-frequency very long baseline interferometric observations of \Msixty\ (NGC~4649), a nearby elliptical galaxy hosting a nearly dormant SMBH with an Eddington ratio of $\sim10^{-8}$. We detect a compact two-sided jet with an unusually steep synchrotron spectrum, demonstrating that collimated outflows can persist even under nearly dormant accretion conditions. The apparent radio core exhibits an unprecedentedly steep frequency-dependent position shift toward the SMBH, locating the central engine only $\sim57\,\mu$as, corresponding to a projected distance of $\sim10$ Schwarzschild radii, upstream of the 8.37-GHz core. The observed jet morphology and steep core-shift behaviour are reproduced by general relativistic magnetohydrodynamic and radiative-transfer simulations, indicating a magnetically dominated, non-equipartition jet-launching region that departs from the standard conical equipartition picture. These results provide direct observational evidence that jet production can survive near the dormant SMBHs and establish \Msixty\ as a unique laboratory for probing jet formation on event-horizon scales in the lowest-accretion SMBH regime.
Read the full abstract

All authors Xiaopeng Cheng, Hai Yang, Jun Yang, Xiaofeng Li, Feng Yuan, Rusen Lu, Hyunwook Ro, Bong Won Sohn, Lulu Fan, Yihang Zhang, Wen Chen, Niu Liu, John E. Conway, Taehyun Jung

Astrophysics of Galaxies

Distinct Gas and Stellar Circular Rotation Curves in the Milky Way Galaxy

Alistair H. Nelson, Yoshiaki Sofue and Peter R. Williams

The rotational velocity of interstellar gas in the Milky Way, and other galaxies, has been taken to represent the circular velocity of a test particle in the Galaxy gravitational field, and hence an indicator of the Galaxy mass. The derived circular velocity is found to be too high for the gas to be gravitationally bound to the galaxy given the observed Galaxy mass in stars and gas, and consequently an extra component of mass in the Milky Way and other galaxies, namely dark matter, has been postulated. However recently the observational satellite Gaia, has been carrying out ground-breaking astrometric observations to accurately measure, inter alia, the three dimensional velocities of stars in the vicinity of the Sun and beyond. This has revealed that the circular velocity derived from the stellar population is much less than that of the gas, and the rotation curve, circular velocity versus radius, is distinctly declining with radius, whereas the gas rotation curve is not declining. By combining results from multiple observations of the gas velocity, averaging the velocities in radial bins, we establish that there is a grand average rotation curve. This can be compared directly with a grand average of the published Gaia rotation curves, and the confidence level in the difference between the two estimated by statistical analysis. The difference is shown to have a high degree of confidence, and increases with galactocentric radius. The lower circular rotation curve from the stellar velocities has resulted in significantly reduced estimates of the dark matter mass fraction of the Milky Way. The higher rotation of the gas lacks an explanation, but it is unlikely to be an accurate indicator of the kinematic mass of the Galaxy. This also has significant consequences for the mass of external galaxies based on gas rotation curves.
Read the full abstract

Earth and Planetary Astrophysics

Strong and variable stratospheric CO emission from lava-planet 55 Cnc e observed with NIRCam/JWST

Ignas Snellen, Yamila Miguel, Leoni Janssen et al. (+4 more)

Some rocky planets orbit so close to their host stars that stellar heating melts their surfaces. They offer a rare glimpse of planets in a magma-ocean state, providing an observable analogue to processes that likely shaped the early Earth and other terrestrial planets during their infancy. Recent JWST observations of five eclipses of the prototypical lava planet 55 Cnc e have confirmed earlier hints that it exhibits highly variable thermal emission, with low-resolution spectroscopy pointing to a possible volatile-rich atmosphere likely rich in CO and CO2. Here we report on an analysis of the same JWST datasets but at their native spectral resolution, utilizing cross-correlation techniques. An unambiguously strong ~8 sigma signal from CO in emission is recovered during one out of five epochs, with potential ~3 sigma detections during two others. The strongest observed cross-correlation signal is difficult to reconcile with a hydrostatic atmosphere, requiring a steep and strong thermal inversion at the right pressure level (~1-10 mbar) and a relative abundance of CO2 that is at least 3 orders of magnitude lower which would otherwise mask the CO signal. Self-consistent atmospheric modelling indicates that this is most readily achieved in a hydrogen-rich atmosphere, which produces the steepest inversions and highest CO/CO2 ratios. The pronounced epoch-to-epoch variability suggests that the CO signal does not trace a static atmosphere alone, but may reveal a transient, dynamically active component, potentially linked to variable atmospheric outflow.
Read the full abstract

All authors Ignas Snellen, Yamila Miguel, Leoni Janssen, Dario Gonzalez Picos, Sam de Regt, Natalie Grasser, Lars Klijn

Earth and Planetary Astrophysics · Cross-listed from physics.space-ph

Extreme, transient bursts of energy in the auroral ionosphere. II. A magnetotail dipolarization event

Magnus F Ivarsen, Yukinaga Miyashita, Brian Pitzel et al. (+5 more)

We report ground-based coherent VHF radar observations of extreme turbulent field-structures detected in coincidence with a magnetospheric substorm-associated magnetotail dipolarization. The field-structures are observed by the ICEBEAR radar, in the form of Farley-Buneman (FB) waves in the auroral electrojets, and the field-structures themselves move an order of magnitude faster than the saturation speed of the underlying FB waves, implying transient electric field sources up to 330 mV/m in strength. The field-structures are identified and automatically tracked using an unsupervised clustering & tracking algorithm, applied to clutters of ICEBEAR radar backscatter targets, a method that turns the Doppler radar into a tracking radar capable of measuring the ionospheric ExB-drift by proxy. We place this finding in a coordinated multi-instrument context. Three THEMIS spacecraft observed the dipolarization event in-situ in the near-Earth plasma sheet. In the ionosphere, Swarm A, crossing through the guilty auroral arc at the onset of the dipolarization event, recorded clear signatures of propagating Alfvén waves threading the relevant flux tube. We interpret the ICEBEAR transients as the natural ionospheric foot signature of a shear Alfvén pulse launched by the bipolar space-charge (Hall) electric field of the thinned current sheet, with amplification along the converging flux tube, partial reflection at the ionospheric boundary, and spatial sharpening by precipitation-produced Pedersen-conductance gradients on the auroral arc edges. A one-dimensional wave-transmission analysis recovers the observations. Our results elucidate a tightly controlled coupling between magnetotail processes and meter-scale auroral plasma turbulence, and demonstrate the capability of ICEBEAR to resolve extreme, transient electric-field enhancements in the ionosphere.
Read the full abstract

All authors Magnus F Ivarsen, Yukinaga Miyashita, Brian Pitzel, Jean-Pierre St-Maurice, Jaeheung Park, Devin R Huyghebaert, Yangyang Shen, Glenn C Hussey

Instrumentation and Methods for Astrophysics

Some polarized lines of the second solar spectrum (SrI, CaI, BaII, C2, MgH, NdII) observed at the Meudon Solar Tower spectropolarimeter

Jean-Marie Malherbe

The second solar spectrum is the spectrum of the Stokes parameter Q (linear polarization) close to the solar limb. It is made of a few polarized lines with Q/I of about 1% (such as CaI, SrI, or BaII), but most lines exhibit weaker polarization. This paper presents processing of unpublished observations made in 2008 with the Meudon solar tower spectropolarimeter, which are of interest for weak and turbulent unresolved magnetic field measurements in the quiet Sun, through the Hanle effect.
Read the full abstract

High Energy Astrophysical Phenomena

Centrifugal instability of compressible flows and the hydrodynamic stability of accretion disks

Serguei S. Komissarov and Konstantinos N. Gourgouliatos

A recent analysis of the centrifugal instability in the case of pressure-supported compressible relativistic rotation, with application to astrophysical jets, yielded a generalisation of the famous Rayleigh criterion for Newtonian flows. According to this criterion, the centrifugal instability is strongly affected by the flow Mach number, and not only in the relativistic fluid dynamics but also in its Newtonian limit. To validate the Newtonian version of this criterion, we performed axisymmetric numerical simulations of non-relativistic transonic rotating flows which are stable according to the original Rayleigh criterion but can be either stable or unstable according to the new one. The results of computer simulations are found to be in perfect agreement with the theory. The hydrodynamic stability of accretion disks is often explained by referring to the original Rayleigh criterion, even if their rotation is highly supersonic. To clarify the matter, we analysed the hydrodynamic stability of flows rotating about central compact object and derived an instability criterion that retains the explicit dependence on the flow Mach number. This criterion turns out to be equivalent to the standard Solberg-Høiland criterion, which does not involve the Mach number. The same applies to the case of pressure-supported rotation, where the role of gravity is played by the centrifugal force.
Read the full abstract

High Energy Astrophysical Phenomena

Recombination Rates for $5f^N$ Uranium Ions Using the Analogous $4f^4$ Nd III as a Guideline and Their Effect on Kilonova Nebular SpectraAn Exploration of Recombination of Uranium with application to Kilonovae Spectra

Niamh Ferguson, Anders Jerkstrand, Smaranika Banerjee et al. (+2 more)

Dielectronic recombination (DR) is expected to be the dominant recombination process during the non-local thermodynamic equilibrium (non-LTE) phase of kilonovae, yet reliable DR data remain unavailable for most heavy ions. Current spectral models therefore rely on simplified recombination prescriptions, introducing significant uncertainties into predicted spectra. We present an optimization strategy for open f-shell ions using AUTOSTRUCTURE, targeting uranium ions U II–U IV relevant to actinide-producing kilonovae. As a benchmark case, calculations are performed for Nd III to validate the treatment of the f-shell structure and its impact on DR. The resulting DR rate coefficients are of order $10^{-10}$–$10^{-12}$ cm$^{3}$\,s$^{-1}$ over temperatures relevant to kilonova plasmas. The optimized rates are implemented into the radiative-transfer code SUMO, and their impact on kilonova spectra studied. The Nd III benchmark demonstrates that refinements to the atomic structure can produce measurable changes in spectral features supporting the atomic structure optimisation performed for U II–IV.
Read the full abstract

All authors Niamh Ferguson, Anders Jerkstrand, Smaranika Banerjee, Martin. G. O'Mullane, Nigel.R.Badnell

Instrumentation and Methods for Astrophysics

Time Series Analysis in Machine Learning

Antonio Pagliaro and Anna Anzalone

Time series analysis is a fundamental component of machine learning, especially in astrophysics and cosmology where temporal data abound. This chapter provides a pedagogical review of time series analysis techniques from a machine learning perspective. We cover the basic concepts of time series (stationarity, autocorrelation, seasonality), classical statistical models (autoregressive, moving average, ARIMA, exponential smoothing, state-space models), and modern machine learning approaches. In particular, we discuss how traditional statistical methods lay the groundwork, and then explore machine learning methods for time series, including feature-based regression, tree-based ensemble methods, hidden Markov models, Gaussian processes, and deep learning models (recurrent neural networks, convolutional networks, transformers). Throughout, we illustrate with examples drawn from multiple domains (e.g. astronomy, weather forecasting, finance) to emphasize common principles. The goal is to equip readers with both the theoretical understanding and practical context to apply machine learning techniques for time series analysis in their research.
Read the full abstract

Instrumentation and Methods for Astrophysics

Machine Learning for Event Reconstruction in Imaging Atmospheric Cherenkov Telescopes

Antonio Pagliaro and Antonino La Barbera

Imaging Atmospheric Cherenkov Telescopes (IACTs) are the leading instruments for very-high-energy (VHE) gamma-ray astronomy, covering the range from hundreds of GeV to hundreds of TeV. This chapter reviews the critical role of machine learning in reconstructing the physical properties of particles detected by IACTs. We introduce the IACT technique and its central challenge: distinguishing rare gamma-ray showers from the overwhelming cosmic-ray background. We detail the standard reconstruction pipeline, from image cleaning and Hillas parameterization to stereoscopic observation, and frame event reconstruction as a supervised learning problem encompassing particle classification and energy/direction regression. Two frontiers of innovation are then explored: the exploitation of the temporal dimension of shower images through novel timing-based features that enhance background rejection at low energies, and the application of advanced ensemble methods (gradient boosting, stacking) that surpass baseline Random Forests, notably in mitigating systematic energy bias. Finally, we discuss performance metrics and provide an outlook on next-generation approaches dominated by deep learning, including Convolutional and Graph Neural Networks.
Read the full abstract

Earth and Planetary Astrophysics

Machine-learning clustering of close-in exoplanet populations: links to pebble accretion

Yi Duann, Anders Johansen, Haiyang S. Wang et al. (+1 more)

Close-in exoplanets exhibit a wide range of orbital architectures and physical properties shaped by both formation conditions and migration processes. Although population-synthesis models predict distinct planetary populations, establishing a quantitative connection between observed exoplanets and synthetic populations remains challenging. We investigate the intrinsic organisation of close-in exoplanets using physically motivated dynamical parameters and connect the resulting populations to pebble-accretion formation pathways. A two-stage Gaussian mixture model (GMM) is applied to an observed sample of close-in exoplanets, performing unsupervised probabilistic clustering in a feature space dominated by dynamical descriptors of planet-star interactions. The resulting clusters are mapped onto a pebble-accretion synthetic population within a statistically motivated three-dimensional parameter space. Formation-related quantities, including gas availability, gas fraction, and ice-rock mass ratio, are then used to interpret the mapped populations. We identify statistically supported sub-populations without imposing predefined classification boundaries, including very-massive gas giants, hot giants, warm-Jupiter-dominated systems, and lower-mass giants. The mapped synthetic populations reveal systematic differences in formation timing, gas accretion, and solid growth histories. In particular, very-massive gas giants are preferentially associated with earlier formation epochs than hot-giant and warm-Jupiter-dominated populations. These results demonstrate that physically motivated machine-learning approaches can provide a statistically robust framework for linking observed exoplanet populations to theoretical planet formation pathways.
Read the full abstract

All authors Yi Duann, Anders Johansen, Haiyang S. Wang, H. Jens Hoeijmakers

Astrophysics of Galaxies

Geometry and Kinematics of Molecular Cloud Substructures in the Second Galactic Quadrant

Wen Ge and Fujun Du

We analyze the geometry and kinematics of substructures within molecular clouds identified in an unbiased catalog from the MWISP survey. These substructures are defined as spatially connected regions enclosed by the 20% peak-integrated-intensity contour of each cloud. After applying selection criteria on voxel size and excluding structures truncated by map boundaries, we construct a sample and quantify their projected morphology using the projected scale ratio $R=\Delta b/(\Delta l\cdot\cos b)$. This ratio essentially measures $\tan\theta$ where $\theta$ is the plane-of-sky angle of an elongated filament relative to the Galactic plane. The resulting sample exhibits a median $R=0.96$, indicating a slight but systematic preference for elongation along Galactic longitude. This tendency becomes more pronounced at larger spatial scales. We further investigate the relative orientations among the structural major axes, velocity-gradient directions, and plane-of-sky magnetic-field orientations derived from Planck data for a subsample of well-defined structures. We find that, for cloud structures within our sample, with physical scale $\sim 0.3$ to $\sim 30$ pc, velocity gradients tend to be perpendicular to the major axes, while magnetic-field are generally aligned parallel to them. This scale range differs from those typically probed in studies of dense cores ($\sim 0.05$ pc) and GMC-scale structures ($\gtrsim$ 10 to 100 pc), which have reported scale-dependent variations in relative orientations. In addition, the alignment between velocity gradients and magnetic fields shows a gradual weakening with increasing physical scale. These results suggest that the observed anisotropy of molecular cloud substructures may arise from a combination of large-scale Galactic dynamics, anisotropic gas motions, and magnetic fields, with the relative importance of these effects varying with scale.
Read the full abstract

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

Comisso-Asenjo Mechanism in Rotating $\mathcal{N}=2,U(1)^2$ Gauged Supergravity Black Holes: Extended Comparison With Kerr Black Hole

Abhinav Jaguri, Hemwati Nandan, Pankaj Sheoran et al. (+1 more)

In this paper, we investigate energy extraction via the Comisso-Asenjo (CA) magnetic reconnection process near a coupled $\mathcal{N}=2,\,U(1)^2$ gauged supergravity Black Hole (BH). Our study focuses on the combined impact of the independent parameter set $p_i\in(N_g,g,v,e)$ with the spin parameter $a$ on the extracted energy ($\epsilon_{\pm}$), efficiency ($\eta$), and extracted power ($\mathcal{P}_{CA}$), aiming to identify optimal combinations where energy can be extracted with higher efficiency in certain cases at lower spin $(a\sim0.39)$ than the Kerr extremal case $(a\sim1)$. Using the spacetime parameters, we explore various cases leading to distinct spacetimes and provide an extended comparison with the Kerr Black Hole (KBH). We also examine the influence of the orientation angle ($\xi$) and magnetization parameter ($\sigma_0$) on both efficiency and extracted power. Investigating low $[\,\forall p_i<0.2 \land N_g<0.08\,]$, mid $[\,\exists p_i\ge0.5 \land N_g\in(0.08,0.15)\,]$, high $[\,\exists p_i>0.7 \land N_g\in(0.16,0.23)\,]$, and mixed $[\,\forall p_i\in(0,1) \land N_g\in(0,0.23)\,]$ parameter combinations, we explore only extremal cases for all spacetime parameters and demonstrate that the extremal Kerr efficiency limit ($\eta>1.495$) can be exceeded. The statistical Kendall's Tau approach allows us to identify the key independent parameters acting as boosters or dampers in the energy extraction process and to visualize the relationship between $(N_g,g,v,e)$ and the physical outputs $(a_{\rm ext},r_E,r_{\rm ergo},\epsilon_{\pm},\eta,\mathcal{P}_{CA},R_{\eta},R_{\mathcal{P}})$. Furthermore, we show that the observable Lundquist number $S_{\rm obs}$ in rotating BH spacetimes acquires an observer-dependent angular dependence through the lapse function $(\alpha)$. This leads to deviations from the standard Sweet-Parker scaling when expressed in terms of observable quantities.
Read the full abstract

All authors Abhinav Jaguri, Hemwati Nandan, Pankaj Sheoran, Sanjar Shaymatov

Cosmology and Nongalactic Astrophysics

Bayesian Constraints on Inverse-Tangent Inflation with Constant-EOS Reheating and a Dynamical Reheating Analysis

Mayur Abhisheki and Prasanta Kumar Das

We perform a Bayesian inference analysis of an inflationary model based on an inverse-tangent potential, incorporating reheating dynamics in both constant and dynamical equation-of-state (DEOS) frameworks. Using Planck and ACT constraints on the scalar spectral index, we find preferred values $\kappa\simeq0.5-0.6$ and $N_k\simeq40-60$, leading to reheating temperatures $T_{RH}\sim10^{10}-10^{14}$ GeV and reheating durations $N_{RH}\sim3-36$ e-folds. Reheating weighted $H_0$ posteriors shift the Planck inference towards the ACT preferred region through the intrinsic $n_s-H_0$ degeneracy of the CMB likelihood. In the DEOS framework, reheating with a constant decay rate yields $N_{RH}\simeq4-8$ e-folds and $T_{RH}\simeq10^{13}$ GeV, while a dynamical decay rate produces a strong dependence on the Yukawa coupling $y$, with $N_{RH}$ varying from $\mathcal{O}(30)$ to $\mathcal{O}(1)$ e-folds and the reheating temperature spanning $\sim10^{-2}-10^{14}$ GeV. Imposing inflation-reheating consistency significantly restricts the viable parameter space to a narrow region around $n_s\simeq0.9720-0.9725$ and $r\simeq0.026-0.060$, demonstrating that reheating dynamics provide a nontrivial bridge between early-universe inflation and late-time cosmological parameter inference.
Read the full abstract

Instrumentation and Methods for Astrophysics

Design of a three-lens wide field corrector with aspherical surfaces for the 2.34-m VBT

Nitish Singh, S. Sriram and Bharat Kumar Yerra

We are developing a compact three-element Wide Field Corrector (WFC) with spherical and aspherical lenses for the 2.34 m Vainu Bappu Telescope (VBT) to enhance its field coverage for imaging and spectroscopic applications. The design consists of three optical elements, with at least one spherical lens movable to serve as an Atmospheric Dispersion Corrector (ADC), while the aspherical elements remain fixed to maintain optical stability. We are currently testing two design configurations, one with two spherical lenses and one aspherical lens, and another with two aspherical lenses and one spherical lens. The ADC is designed to correct atmospheric dispersion for zenith angles ranging from 0 degree to 60 degree. The system is optimized to operate over a wavelength range of 0.4 {\mu}m to 0.9 {\mu}m, targeting an effective field of view of about 0.5 degree. Considering the limited mechanical space available at the VBT prime focus, the design emphasizes compactness, ease of alignment, and manufacturability. The system achieves a mean D80 better than 0.3 arcsec and 0.23 arcsec for Design 1 and Design 2, respectively, at zenith, and maintains a mean D80 within 0.57 arcsec and 0.45 arcsec up to a zenith angle of 60 degree after atmospheric dispersion correction. Atmospheric dispersion at higher zenith angles (up to 60 degrees) is corrected using a movable lens element, enabling the system to preserve high image quality across the field.
Read the full abstract

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

Horizon absorption in eccentric precessing binary black hole inspirals and its importance for gravitational wave data analysis

Alberto Álvaro-Díaz and Gonzalo Morras

During the evolution of a binary black hole, energy and angular momentum are exchanged between the orbital motion and the individual black holes through horizon absorption, modifying both the binary dynamics and the black hole masses and spins. This leaves an imprint on the emitted gravitational waves that may be relevant for the accurate modeling of signals observed by current and future detectors, while also offering a probe of the nature of compact objects. In this work, we derive, for the first time and at leading order in the post-Newtonian expansion, the effect of horizon absorption in binary black hole inspirals with both orbital eccentricity and spin-induced precession, and we incorporate these corrections into the pyEFPEHM waveform model. We then quantify their impact through analytical estimates of the orbital dephasing, waveform mismatches, and Bayesian parameter-estimation studies. The effect is largest for systems with large spin components (anti-)aligned with the orbital angular momentum ($|\vec{\chi}_i \cdot \hat{l}| \sim 1$), highly unequal mass ratios ($q=m_2/m_1 \ll 1$), and long inspirals spanning a wide frequency range ($\log(f_\mathrm{max}/f_\mathrm{min}) \gg 1$). For such systems, neglecting horizon absorption biases the recovered binary parameters at moderate signal-to-noise ratios. In quasi-circular binaries these biases largely absorb the effect, rendering it difficult to detect. In eccentric binaries, however, the richer signal morphology breaks this degeneracy, making horizon absorption potentially measurable in high signal-to-noise-ratio events.
Read the full abstract

Instrumentation and Methods for Astrophysics

Wavelet-Based Extraction of Transient Noise in Gravitational-Wave Interferometers using a Saliency-Guided Learning Architecture

Christopher Allene, Dhruv Kumar, Yusuke Sakai et al. (+2 more)

Gravitational-wave interferometers exhibit a wide variety of short-duration non-Gaussian transients, commonly referred to as glitches, that complicate the detection of astrophysical signals, bias parameter estimation, and detector characterisation. Existing machine-learning approaches classify glitch morphologies but do not provide a complete mechanism to segment and extract these disturbances from the strain data. We introduce a wavelet-based, saliency-guided framework for the supervised extraction of transient noise. Candidates are first pre-tagged using Uniform Manifold Approximation and Projection, which is also used as a diagnostic of the learned representations. A traditional learning model operating on Continuous Wavelet Transform spectrograms then identifies relevant time-frequency regions through saliency maps. These saliency patterns are transferred to an invertible multiresolution representation via the Discrete Wavelet Transform, where adaptive coefficient masking enables exact reconstruction of both glitch-only and glitch-suppressed waveforms. We demonstrate effective extraction across several representative glitch families, including 'Whistle' and 'Scattered-Light' transients, and show robustness in challenging regimes such as low signal-to-noise events and partially overlapping structures, where classical thresholding or band-limited filtering methods typically fail or introduce leakage. The proposed framework offers an interpretable and computationally efficient approach to transient-noise extraction, establishing a foundation for scalable applications to larger glitch catalogs and future observing runs.
Read the full abstract

All authors Christopher Allene, Dhruv Kumar, Yusuke Sakai, Marco Meyer-Conde, Hirotaka Takahashi

Solar and Stellar Astrophysics

Empirical colour–effective temperature relations in the SDSS system from IRFM temperatures of GALAH and APOGEE stars

Zenghua Zhou, Luca Casagrande, Xiaobin Zhang et al. (+5 more)

Reliable estimates of stellar effective temperature ($T_{\mathrm {eff}}$) are fundamental to stellar population studies and Galactic astrophysics. However, the majority of stars observed in modern large-scale photometric surveys lack spectroscopic measurements, making empirical colour–$T_{\mathrm {eff}}$ relations essential tools. In this work, we present updated empirical colour–$T_{\mathrm {eff}}$ calibrations based on Sloan Digital Sky Survey (SDSS) $ugriz$ photometry combined with 2MASS $JHK_{\mathrm s}$ data. Effective temperatures are determined on a homogeneous InfraRed Flux Method (IRFM) scale using a combined sample of 3902 GALAH and 2535 APOGEE stars with high-quality photometry and well-characterised atmospheric parameters. Using this dataset, we establish empirical relations between $T_{\mathrm {eff}}$ and colour indices constructed from SDSS and 2MASS combinations. We provide both colour–metallicity–$T_{\mathrm {eff}}$ and colour–$T_{\mathrm {eff}}$ relations for dwarfs and giants. The calibrations are derived using low-order polynomial models with iterative $3\sigma$ clipping. Their performance depends on the adopted colour index, with long-baseline colours such as $(g-K_{\mathrm s})_0$ and $(g-z)_0$ achieving internal precisions of $\sim$30–50~K. Comparisons with previous calibrations show general agreement, with differences attributable to sample selection, photometric zero-points, and functional form. The resulting relations provide a homogeneous and internally consistent framework for estimating $T_{\mathrm {eff}}$ from SDSS and 2MASS photometry alone, and are well suited for application to large photometric surveys lacking spectroscopic information.
Read the full abstract

All authors Zenghua Zhou, Luca Casagrande, Xiaobin Zhang, Jianping Xiong, Jiao Li, Yanjun Guo, Zhanwen Han, Xuefei Chen

Instrumentation and Methods for Astrophysics

Recalibration of SDSS photometric zero-points based on the InfraRed Flux Method temperature scale

Zenghua Zhou, Luca Casagrande, Heran Xiong et al. (+4 more)

Accurate photometric zero-points are essential for translating observed magnitudes into physical fluxes, from comparing with models to ensuring consistency across surveys. We determine the zero-points needed to place the Sloan Digital Sky Survey (SDSS) $ugriz$ system on its nominal AB definition, by exploiting the sensitivity of the Infrared Flux Method (IRFM) to broadband flux calibration. Using benchmark effective temperatures for over 6,000 FGK-type stars, we invert the method to identify the zero-point corrections required for SDSS photometry to reproduce the adopted temperature scale. The $r$ band is found to be very well standardized, while the $i$ and $z$ bands show offsets of a few hundredths of a magnitude, consistent with previous studies. We also find a small offset in the $g$ band. The largest discrepancy occurs in the $u$ band, where the derived offset depends strongly on the adopted filter transmission curves, in particular whether one uses the original definition commonly adopted in the literature or the updated measurements that account for the presence of a red leak. This effect introduces a colour-dependent zero-point offset that becomes apparent when using a sample of late-type stars. Independent comparisons with CALSPEC spectrophotometric standards and Gaia XP spectra broadly support the offsets derived from the IRFM analysis. Our results provide a revised set of SDSS zero-points anchored to the IRFM temperature scale and demonstrate that large stellar samples can be used to constrain photometric calibration. The methodology presented here offers a complementary approach to traditional spectrophotometric calibration and may prove useful for future large-scale surveys.
Read the full abstract

All authors Zenghua Zhou, Luca Casagrande, Heran Xiong, Yanjun Guo, Jiajia Li, Zhanwen Han, Xuefei Chen

Cosmology and Nongalactic Astrophysics

Equilibrium Halo Solutions of the Gross-Pitaevskii-Poisson System: The Role of the Particle Number

Francisco A. Guzmán, Elías Castellanos and Jorge Mastache

We investigate stationary halo-like solutions of the Gross-Pitaevskii-Poisson (GPP) system, which describes self-gravitating Bose-Einstein condensates with repulsive self-interactions, as a dark matter model. The boson mass $m_\phi$, scattering length $a_s$, and total particle number $N$ are kept explicit, with $N$ treated as an independent macroscopic control parameter. Solving the stationary GPP equations over a broad parameter space, we identify ground-state, excited-state, and unbound solution branches according to their binding properties and nodal structure. The ground-state branch occupies a well-defined region of the $(m_\phi,N)$ plane whose location depends strongly on the self-interaction strength, whereas the excited-state and unbound regions are largely insensitive to the initial ansatz. From the converged solutions, we derive empirical scaling relations connecting the characteristic halo radius $R_{99}$ to $m_\phi$, $a_s$, and $N$. In the weakly interacting regime, the results reproduce the standard Schrodinger-Poisson mass-radius relation, while finite self-interactions reveal an intermediate regime in which gravity, quantum pressure, and repulsive interactions jointly determine the equilibrium structure. As an astrophysical application, we show that ground-state solutions can reproduce representative dwarf-galaxy rotation curves using only the solitonic component. We also examine the implications of current Lyman-$\alpha$ forest constraints and find that, although increasing $a_s$ shifts equilibrium solutions toward larger boson masses compatible with existing bounds, the resulting configurations do not reproduce the observed dwarf-galaxy kinematics. These results provide a systematic characterization of stationary GPP halos and establish a direct connection between microscopic particle properties and observable galactic quantities.
Read the full abstract

High Energy Astrophysical Phenomena

Long thermonuclear burst driven thermal-viscous instability of accretion disk: triggering an outburst-like X-ray flare

Wenhui Yu, Zhaosheng Li, Yuanyue Pan et al. (+2 more)

We report on NICER and MAXI observations of a long-duration thermonuclear X-ray burst and a subsequent outburst-like X-ray flare from the neutron star low-mass X-ray binary MAXI J0911–655. Prior to the burst, the source was in a persistent low/hard state with a power-law-dominated spectrum ($\Gamma \sim 1.7$) and a mass accretion rate of $\sim 1\%$ of the Eddington limit. The long burst, detected by MAXI on 2020 May 22 (MJD 58991.7101), was rapidly followed up by NICER. From time-resolved spectroscopy of the cooling tail, we estimate an exponential decay time of $\approx43$ minutes, the ignition column depth of $\approx0.1\times 10^{12}~{\rm g ~cm^{-2}}$, the burst fluence of $\approx 1.1\times 10^{-4}~{\rm erg~cm^{-2}}$, and the total energy release of $\approx1.2\times10^{42}$ erg. Approximately one day after the burst onset, the 0.5-10 keV light curve unexpectedly re-brightened, initiating an outburst-like flare. During the peak of this flare, the persistent power-law flux increased from its pre-burst level of $\sim0.27\times10^{-9}~{\rm erg~cm^{-2}~s^{-1}}$ to $1.4\times10^{-9}~{\rm erg~cm^{-2}~s^{-1}}$. This flux enhancement was accompanied by significant spectral softening, with the photon index increasing to $\Gamma \sim 2.2$. Subsequently, the flux decayed and the source returned to its baseline low/hard state. The observed timescales and energetics suggest that intense irradiation from the long burst amplified the ongoing thermal-viscous accretion process. This heating drove an inside-out heating front that temporarily enhanced the mass accretion rate, providing compelling observational evidence of a thermonuclear burst directly modulating the accretion dynamics of its surrounding disk.
Read the full abstract

All authors Wenhui Yu, Zhaosheng Li, Yuanyue Pan, Yanan Wang, Erlin Qiao

Tuesday 9 June

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

Thermodynamic coefficients in third-order relativistic fluid dynamics

Teboho Abram Moloi and Azwinndini Muronga

We developed the third-order hydrodynamic equations using relativistic extended thermodynamics of gases with 14 independent fields. The resulting fluid equations are based on the relativity principle, the entropy principle, and the requirement of hyperbolic, and hence finite, propagation of disturbances, which is automatically incorporated. The expressions of entropy, four-current, shear-stress tensor, dynamic pressure, and heat flux are expanded up to third order (cubic). We explicitly present the newly calculated coefficients in the equilibrium properties of an ultra-relativistic gas regime and the non-degenerate relativistic gas. Contrary to the general cases, the non-degenerate regime eliminates fugacity from the coefficients, allowing for the easy normalization of these coefficients, and the ultra-relativistic regime provides us with the upper bounds of these coefficients. We found good agreement on some of the coefficients as compared to calculations from earlier models, specifically in kinetic theory, and other coefficients had slightly different values to those obtained in kinetic theory.
Read the full abstract

Instrumentation and Methods for Astrophysics

Revealing Cosmic Ecosystems with the Hubble Space Telescope in 2030s and Beyond

Sanchayeeta Borthakur, Tanmay Singh, David French et al. (+22 more)

Ultraviolet spectroscopy with the Hubble Space Telescope (HST) provides the most direct and sensitive probe of the disk-circumgalactic medium (CGM) interface at radii of 20 kpc, where galaxies exchange gas, metals, and energy with their surroundings. Many of the key diagnostics of the multiphase circumgalactic medium – including H I, O VI, C II-IV, Si II-IV, N V, Ne VIII, and other metal transitions – lie in the ultraviolet and are inaccessible from the ground, making HST the only observatory capable of making the required observations. By measuring the physical (column density, density), chemical (metallicity, ionization structure), and kinematical properties of the gas at the disk-CGM interface, UV absorption-line spectroscopy reveals how galaxies acquire fresh fuel, recycle enriched material, and drive feedback into their halos. When combined with spectroscopic characterization of the host galaxy's stellar populations and the feedback they generate (outflow velocity, mass loading), we will establish a direct understanding of how stellar populations enable circulation of gas and metals through the galactic ecosystem. HST's ultraviolet (UV) spectroscopic capability provides the only comprehensive observational pathways for uncovering the physical drivers that regulate galaxy growth and evolution in the low-redshift Universe.
Read the full abstract

All authors Sanchayeeta Borthakur, Tanmay Singh, David French, Yakov Faerman, Kate Rubin, Brad Koplitz, Rongmon Bordoloi, Frances H. Cashman, Matthew J. Hayes, Yong Zheng, Joseph N. Burchett, Jane C. Charlton, Hsiao-Wen Chen, Andrew J. Fox, Yucheng Guo, Timothy M. Heckman, Christopher J. Howk, Sean D. Johnson, Glenn G. Kacprzak, Varsha P. Kulkarni, Nicolas Lehner, Sowgat Muzahid, Namrata Roy, Evan Scannapieco, Jessica K. Werk

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

Statistical-Uncertainty-Driven Selection of Evaluation Frequency for Time-Dependent Sensing Calibration: A Demonstration with KAGRA Data

Shingo Hido, Takahiro Yamamoto, Dan Chen et al. (+2 more)

Accurate calibration of the gravitational-wave strain h(t) is essential for both detection and astrophysical inference. In operating detectors, slow temporal variations in the sensing response are tracked using calibration lines, but practical constraints can prevent those lines from being injected at frequencies that are favorable for precise estimation of sensing-side parameters. We present a statistical framework for preselecting evaluation frequencies under such constraints. We apply this framework to KAGRA data from the first part of the fourth LIGO-Virgo-KAGRA Observing Run, for which the nominal cavity-pole frequency was about 18 Hz, while the sensing-side calibration line used in practice was injected at 32.7 Hz. For each candidate evaluation frequency, we construct the sensing function, quantify its segment-wise statistical uncertainty from empirical percentiles of the sample distribution, and rank the candidates using a score that combines the interval widths of the amplitude and phase. When a 1% amplitude interval width and a 1 degree phase interval width are weighted equally, 244 Hz is selected in all 4096 s analysis segments throughout the analyzed period. Relative to the reference frequency of 32.7 Hz, the amplitude interval width is reduced to about one quarter over a broad frequency range, while the phase interval width remains broadly comparable. We also assess the discrepancy introduced by frequency translation separately. These results suggest that the proposed method provides a useful statistical preselection framework for evaluation frequencies under practical operational constraints.
Read the full abstract

All authors Shingo Hido, Takahiro Yamamoto, Dan Chen, Takahiro Sawada, Shinji Miyoki

Solar and Stellar Astrophysics

Summary of the First Year of the Space Weather Around Young Suns Program: 900 Hours of Low-frequency Radio and Optical Data Dedicated to Young, Solar-type Stars

Ivey Davis, Gregg Hallinan, Nikita Kosogorov et al. (+51 more)

The Space Weather Around Young Suns (SWAYS) program was introduced in \citet{Davis2025} as a multi-wavelength monitoring program for studying the activity and particle environments of nearby, young, solar-type stars. The SWAYS program currently includes the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) operating between 13–87\,MHz to search for stellar equivalents of solar type~II and III bursts, which are associated with bulk plasma motion in the corona and interplanetary medium. These observations are accompanied by simultaneous photometric data from the high-precision, optical instrument Flarescope to identify associated flare events. These two instruments have collectively acquired nearly 900\,hr of data with $\approx70\%$ overlap between November 2023–June 2024, dedicated to six stars. Here, we present the results of this first season of the SWAYS observing campaign, which include a superflare from the star EK~Draconis with no accompanying low-frequency particle-flux signal. The novelty of the coordination at these specific parts of the spectrum allow us to uniquely evaluate the conditions that may have inhibited a radio detection. We find that the exceptionally hot, dense coronae of incredibly active stars may not be conducive to the development of the instabilities required for type~II and III bursts, or else inspire new expectations for when we should expect to observe a signal relative to the time of the flare. This may represent the plasma-density complement to the magnetospheric limitations to observing space-weather signatures at low frequencies.
Read the full abstract

All authors Ivey Davis, Gregg Hallinan, Nikita Kosogorov, Marin M. Anderson, John Baker, Judd D. Bowman, Rick Burruss, Ruby Byrne, Morgan Catha, Bin Chen, Xingyao Chen, Sherry Chhabra, Curt Corcoran, Larry D'Addario, Jayce Dowell, Katherine Elder, Dale Gary, Charlie Harnach, Carolyn Heffner, Greg Hellbourg, Jack Hickish, Rick Hobbs, David Hodge, Mark Hodges, Yuping Huang, Andrea Isella, Daniel C. Jacobs, Ghislain Kemby, John T. Klinefelter, Matthew Kolopanis, James Lamb, Casey Law, Nivedita Mahesh, Surajit Mondal, Navtej Saini, Brian O'Donnell, Kathryn Plant, Corey Posner, Travis Powell, Vinand Prayag, Andres Rizo, Andrew Romero-Wolf, Jun Shi, Greg Taylor, Jordan Trim, Mike Virgin, Akshatha K. Vydula, Sandy Weinreb, Scott White, David Woody, Sijie Yu, Thomas Zentmeyer, Peijin Zhang, Jeffry Zolkower

Earth and Planetary Astrophysics

Hydrodynamical Simulations of Resonant Breaking in Multi-Planet Systems via Rebound Migration During Disk Dispersal

Beibei Liu, Clément Baruteau, Zhaohuan Zhu et al. (+3 more)

This study extends the investigation of rebound outward migration to multi-planet systems near an inner expanding disk cavity driven by stellar X-ray photoevaporation. Using 2D hydrodynamical simulations, we explore how systems of two and three planets that span masses from super-Earths to Jupiters evolve as the disk disperses from the inside out. Our results show that rebound migration can substantially reshape multi-planet architectures in the final stages of disk clearing. Owing to the strong, positive corotation torque exerted onto the planet near the cavity edge, divergent migration of the neighbouring planets can break resonant configurations and trigger dynamical instabilities, producing non-resonant orbits with widened period ratios. However, the outcome depends critically on planet mass and the disk dispersal timescale. In lower-mass disks where cavity expansion is too rapid, rebound migration is suppressed, and systems tend to preserve resonant chains. These findings suggest that the rebound mechanism can provide a compelling pathway to explain the prevalence of widely separated, non-resonant architecture observed in the exoplanet population.
Read the full abstract

All authors Beibei Liu, Clément Baruteau, Zhaohuan Zhu, Ya-Ping Li, Sijme-Jan Paardekooper, Shigeru Ida