Solar and Stellar Astrophysics
Unusual periodic modulation in the radio emission of the methane dwarf binary WISEP J101905.63+652954.2
Timothy W. H. Yiu, Harish K. Vedantham, Joseph R. Callingham et al. (+1 more)
Brown
dwarfs display Jupiter-like auroral phenomena, such as rotationally modulated electron cyclotron maser
radio emission.
Radio observations of cyclotron maser emission can be used to measure their
magnetic field strength,
topology, and to deduce the presence of magnetically interacting
exoplanets. Observations of the coldest brown
dwarfs (spectral types T and Y) are especially intriguing, as their magnetospheric phenomena could closely resemble those of gas-
giant exoplanets. Here we report observations made over ten epochs, amounting to 44 hours, of WISEP J101905.63+652954.2 (J1019+65 hereinafter) using the LOFAR
telescope between 120 and 168 MHz. J1019+65 is a methane
dwarf binary (T5.5+T7) whose
radio emission was originally detected in a single-epoch LOFAR observation to be highly circular polarised and rotationally modulated at $\approx 3$h. Unexpectedly, our long-term monitoring reveals an additional periodic signature at $\approx 0.787$h. We consider several explanations for the second period and suggest that it could be the rotationally modulated emission of the second brown
dwarf in the binary, although follow-up infrared observations are necessary to confirm this hypothesis. In addition, the data also allow us to statistically estimate the duty cycle and observed
radio-loud fraction of the 120-168\,MHz cyclotron emission from methane
dwarfs to be $\langle D \rangle = 0.030^{+0.034}_{-0.030}$ and $F^{'}_{\rm radio} = 0.088^{+0.168}_{-0.088}$ respectively.
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All authors Timothy W. H. Yiu, Harish K. Vedantham, Joseph R. Callingham, Timothy W. Shimwell
Astrophysics of Galaxies
Accelerating star formation of dense clumps
Xunchuan Liu
We present a statistical framework that establishes an accelerating
star formation scenario for dense clumps using ATLASGAL and ALMAGAL samples. By employing the cumulative distribution function of
dust temperature as a monotonic evolutionary indicator, we linearize clump
evolution into a normalized timescale, enabling direct comparison across different samples. The virial mass of clumps increases exponentially with this normalized time, revealing an accelerating buildup of
star-forming gas within protoclusters. The
evolution of the maximum core mass further shows that the growth timescales of protoclusters and their embedded most massive protostars are comparable, implying a self-similar acceleration of
star formation from the
stellar to the protocluster scale. This unified framework naturally reproduces the observed
evolution of luminosity, the core mass function, the mass growth of the most massive protostars, and the dense gas
star formation law on clump scales, establishing a coherent picture of accelerating
star formation across scales.
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Cosmology and Nongalactic Astrophysics
A Unified Photometric Redshift Calibration for Weak Lensing Surveys using the Dark Energy Spectroscopic Instrument
Johannes U. Lange, Diana Blanco, Alexie Leauthaud et al. (+61 more)
The effective
redshift distribution $n(z)$ of
galaxies is a critical component in the study of weak gravitational
lensing. Here, we introduce a new method for determining $n(z)$ for weak
lensing surveys based on high-quality
redshifts and neural network-based importance weights. Additionally, we present the first unified photometric
redshift calibration of the three leading stage-III weak
lensing surveys, the Dark Energy Survey (DES), the Hyper Suprime-Cam (HSC) survey and the Kilo-Degree Survey (KiDS), with state-of-the-art spectroscopic data from the Dark Energy Spectroscopic Instrument (DESI). We verify our method using a new, data-driven approach and obtain $n(z)$ constraints with statistical uncertainties of order $\sigma_{\bar z} \sim 0.01$ and smaller. Our analysis is largely independent of previous photometric
redshift calibrations and, thus, provides an important cross-check in light of recent cosmological tensions. Overall, we find excellent agreement with previously published results on the DES Y3 and HSC Y1 data sets while there are some differences on the mean
redshift with respect to the previously published KiDS-1000 results. We attribute the latter to mismatches in photometric noise properties in the COSMOS field compared to the wider KiDS SOM-gold catalog. At the same time, the new $n(z)$ estimates for KiDS do not significantly change estimates of
cosmic structure growth from
cosmic shear. Finally, we discuss how our method can be applied to future weak
lensing calibrations with DESI data.
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All authors Johannes U. Lange, Diana Blanco, Alexie Leauthaud, Angus Wright, Abigail Fisher, Joshua Ratajczak, Jessica Nicole Aguilar, Steven Ahlen, Stephen Bailey, Davide Bianchi, Chris Blake, David Brooks, Todd Claybaugh, Andrei Cuceu, Kyle Dawson, Axel de la Macorra, Joseph DeRose, Arjun Dey, Peter Doel, Ni Putu Audita Placida Emas, Simone Ferraro, Andreu Font-Ribera, Jaime E. Forero-Romero, Cristhian Garcia-Quintero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Sven Heydenreich, Hendrik Hildebrandt, Mustapha Ishak, Jorge Jimenez, Shahab Joudaki, Robert Kehoe, David Kirkby, Theodore Kisner, Anthony Kremin, Ofer Lahav, Claire Lamman, Martin Landriau, Laurent Le Guillou, Michael Levi, Leonel Medina Varela, Aaron Meisner, Ramon Miquel, John Moustakas, Seshadri Nadathur, Jeffrey A. Newman, Nathalie Palanque-Delabrouille, Anna Porredon, Francisco Prada, Ignasi Pérez-Ràfols, Graziano Rossi, Rossana Ruggeri, Eusebio Sanchez, Christoph Saulder, David Schlegel, Michael Schubnell, David Sprayberry, Zechang Sun, Gregory Tarlé, Benjamin Alan Weaver, Sihan Yuan, Pauline Zarrouk, Hu Zou
Astrophysics of Galaxies
Rapid bulge assembly in young galaxy disks at Cosmic Dawn
Anshuman Borgohain and Kanak Saha
Recent observations with the James Webb Space
Telescope (JWST) have begun to reveal a surprising morphological diversity in
galaxies within the first billion years after the Big Bang, including indications of structural maturity previously thought to arise much later. These findings raise fundamental questions about when and how well-known structural components of
galaxy morphology, such as bulges and disks, first emerged. However, directly identifying and resolving such structures at z $>$ 6 remains challenging due to limited spatial resolution and sensitivity. In this work, we present a clear and robust morphological analysis of a sample of 190
galaxies at z $>=$ 6, demonstrating that distinct bulge and disk components were already beginning to emerge during this early epoch. Using multi-component light profile fitting, we model the radial brightness distributions of a subset (20) of
galaxies with an inner spheroidal (Sersic) component and an underlying exponential disk. These systems exhibit high bulge-to-total (B/T) light ratios (~ 0.47) and central
stellar mass surface densities (~ 2.82*10$^{8}$ M$_{sun}$ kpc$^{-2}$ ) - values close to those of nearby quiescent
galaxies. Combined with their intense central
star formation rate surface densities (~ 1.26*10$^{1}$ M$_{sun}$ yr$^{-1}$ kpc$^{-2}$ ), our results indicate a rapid building of inner
stellar mass and bulge assembly within these young systems. We propose that these early bulge-disk
galaxies represent progenitors of massive
star-forming and quiescent systems observed at lower
redshifts. Their subsequent
evolution may proceed through physical processes such as disk growth, compaction, quenching, or bulge-disk co-
evolution, driven by both internal dynamics and external interactions.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Inferring the stochastic gravitational-wave background from eccentric stellar-mass binary black holes with spaceborne detectors
Zheng-Cheng Liang, Zhi-Yuan Li and Yi-Ming Hu
The
stochastic gravitational-wave background (SGWB) from eccentric
stellar-mass binary black holes (SBBHs) holds crucial clues to their origins. For the first time, we employ a
Bayesian framework to assess the detectability and distinguishing features of such an SGWB with spaceborne detectors, while accounting for contamination from the
Galactic foreground. Our analysis covers eccentric SBBHs from three formation channels: isolated binary
evolution, dynamical assembly in globular clusters (GCs), and in active
galactic nuclei (AGNs). We find that TianQin,
Laser Interferometry Space
Antenna (LISA), and Taiji can detect the SGWBs from both isolated and GC-formed SBBHs after four years of operation, with the corresponding SNRs of around 10, 60, and 170. However, these backgrounds are spectrally degenerate with a strictly power-law SGWB. Furthermore, highly eccentric SBBHs formed in AGNs yield an SGWB marked by a spectral turnover and sharp decline. While this feature lowers the SNR by approximately an order of magnitude, it can enable a clear distinction from the strictly power-law background using LISA and Taiji.
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Solar and Stellar Astrophysics
Modeling multiphase plasma in the corona: prominences and rain
Rony Keppens, Yuhao Zhou and Chun Xia
We review major achievements in our understanding of multiphase coronal
plasma, where cool-dense and hot-tenuous matter coexists, brought about by advances in modeling and theory, inspired by observations. We give an overview of models that self-consistently form
solar (or
stellar) prominences and filaments, or (postflare) coronal rain, and clarify how these different phenomena share a common physical origin, relating radiative losses and coronal heating. While we do not fully understand the coronal heating, multi-dimensional models of
solar prominence and rain formation demonstrate how thermal instability triggers condensations, and how their morphology may reveal aspects of the applied heating at play. We emphasize how the many pathways to linear instability due to combined ingredients of heat-loss,
gravity, flows, and
magnetic topologies are all involved in the resulting nonlinear magnetohydrodynamics. We provide some challenges to future model efforts, especially concerning prominence fine structure, internal dynamics, and their overall lifecycle.
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Earth and Planetary Astrophysics
The CARMENES search for exoplanets around M dwarfs : Understanding the wavelength dependence of radial velocity measurements
S. V. Jeffers, J. R. Barnes, P. Schöfer et al. (+22 more)
Context. Current
exoplanet surveys are focused on detecting small
exoplanets orbiting in the
liquid-water habitable zones of their host
stars. Despite the recent significant advancements in instrumental developments, the current limitation in detecting these
exoplanets is the intrinsic variability of the host
star itself. Aims. Our aim is to use the full CARMENES guaranteed time observations (GTO) data set spanning more than 8 years of observations of over 350
stars to investigate the wavelength dependence of high-precision radial velocities (RV), as
stellar activity features should exhibit a wavelength dependence while the RV variation due to an orbiting
planet will be wavelength independent. Methods. We use the chromatic index (CRX) to quantify the slope of the measured RVs as a function of logarithmic wavelength. We investigate the dependence of the CRX in the full CARMENES GTO sample on 24
stellar activity indices in the visible and near-infrared channels of the CARMENES spectrograph and each
star's
stellar parameters. We also present an updated convective turnover time scaling for the calculation of the
stellar Rossby number for M
dwarfs. Results. Our results show that approximately 17% of GTO
stars show a strong or a moderate correlation between CRX and RV. We can improve the measured RVs by a factor of up to nearly 4 in rms by subtracting the RV predicted by the CRX-RV correlation from the measured RVs. Mid M
dwarfs with moderate rotational velocities, moderate CRX-gradients and quasi-stable activity features have the best rms improvement factors. Conclusions. We conclude that the CRX is a powerful diagnostic in mitigation of
stellar activity and the search for low mass rocky
planets.
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All authors S. V. Jeffers, J. R. Barnes, P. Schöfer, S. Reffert, V. J. S. Béjar, A. Quirrenbach, A. Reiners, Y. Shan, M. R. Zapatero Osorio, B. Fuhrmeister, P. J. Amado, J. A. Caballero, I. Ribas, C. Cardona Guillén, F. Del Sordo, M. Fernández, A. García-López, A. Guijarro, A. P. Hatzes, M. Lafarga, N. Lodieu, M. Kürster, K. Molaverdikhani, D. Montes, J. C. Morales
Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics
Illuminating the lantern: coherent, spectro-polarimetric characterisation of a multimode converter
Adam K. Taras, Barnaby R. M. Norris, Christopher Betters et al. (+4 more)
While photonic lanterns efficiently and uniquely map a set of input modes to single-mode outputs (or vice versa), the optical mode transfer
matrix of any particular fabricated device cannot be constrained at the design stage due to manufacturing imperfections. Accurate knowledge of the mapping enables complex sensing or beam control applications that leverage multimode conversion. In this work, we present a characterisation system to directly measure the electric field from a photonic lantern using digital off-axis holography, following its
evolution over a 73 nm range near 1550 nm and in two orthogonal, linear polarisations. We provide the first multi-wavelength, polarisation decomposed characterisation of the principal modes of a photonic lantern. Performance of our testbed is validated on a single-mode fibre then harnessed to characterise a 19-port, multicore fibre fed photonic lantern. We uncover the typical wavelength scale at which the modal mapping evolves and measure the relative dispersion in the device, finding significant differences with idealised simulations. In addition to detailing the system, we also share the empirical mode transfer
matrices, enabling future work in astrophotonic design, computational imaging, device fabrication feedback loops and beam shaping.
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All authors Adam K. Taras, Barnaby R. M. Norris, Christopher Betters, Andrew Ross-Adams, Peter G. Tuthill, Jin Wei, Sergio Leon-Saval
Earth and Planetary Astrophysics
BEBOP VIII. SOPHIE radial velocities reveal an eccentric, circumbinary brown dwarf
Amaury H.M.J. Triaud, Thomas A. Baycroft, Neda Heidari et al. (+18 more)
Circumbinary configurations offer a test of
planet formation in an altered environment, where the inner binary has perturbed a protoplanetary disc. Comparisons of the physical and orbital parameters between the circumbinary
planet population and the population of
exoplanets orbiting single
stars will reveal how these disc perturbations affect the assembly of
planets. Circumbinary
exoplanets detected thus far typically have masses $< 3 \,\rm M_{jup}$ raising the question of whether high-mass circumbinary
planets are possible, and also whether population features such as the brown
dwarf desert would appear in circumbinary configurations like for single
star systems. Here, we report observations taken with the SOPHIE high-resolution spectrograph. These observations reveal an $m_{\rm b}\,\sin i_{\rm b} = 20.9 \,\rm M_{jup}$ outer companion, on an eccentric ($e = 0.43$), $1800\,\rm d$ orbit, which we call BEBOP-4 (AB) b. Using dynamical arguments we constrain the true mass $m_{\rm b}< 26.3 \,\rm M_{jup}$. The inner binary's two eclipsing
stellar components have masses $M_{\rm A} = 1.51\,\rm M_\odot$, and $M_{\rm B} = 0.46\,\rm M_\odot$. Their orbital period is $72\,\rm d$, and their eccentricity is $0.27$. This system contains the longest period binary surveyed by the BEBOP project. BEBOP-4b is expected to be detectable using
Gaia DR4 single epoch astrometric measurements. Despite a large period ratio of $\sim 25:1$, the substantial eccentricities of both orbits mean that the outer orbit is on the edge of orbital stability, and located in between two destabilising secular resonances. Should the outer companion survive, the BEBOP-4 system appears like a precursor to several post-common envelope binaries exhibiting eclipse timing variations where very massive circumbinary companions have been proposed.
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All authors Amaury H.M.J. Triaud, Thomas A. Baycroft, Neda Heidari, Alexandre Santerne, Aleyna Adamson, Isabelle Boisse, Gavin A.L. Coleman, Alexandre C.M. Correia, Yasmin T. Davis, Magali Deleuil, Guillaume Hébrard, David V. Martin, Pierre F.L. Maxted, Richard P. Nelson, Lalitha Sairam, Daniel Sebastian, Matthew R. Standing, Adam T. Stevenson, Amalie Stokholm, Mathilde Timmermans, Stéphane Udry
Instrumentation and Methods for Astrophysics
Pre-flight Background Estimates for COSI
Savitri Gallego, Uwe Oberlack, Jan Lommler et al. (+14 more)
The Compton Spectrometer and Imager (COSI) is a Compton
telescope designed to survey the 0.2 - 5 MeV sky, consisting of a compact array of cross-strip germanium detectors. It is planned to be launched in 2027 into an equatorial low-Earth (530 km) orbit with a
prime mission duration of 2 years. The observation of MeV gamma rays is dominated by background, mostly from extragalactic and atmospheric
photon but also from the activation of the detector materials induced by
cosmic-ray interactions. Thus, background simulation and identification are crucial for the data analysis. In this work we perform Monte Carlo simulations of the background for the first 3 months in orbit, and we extrapolate the results to 2 years in orbit, in order to determine the build-up of the activation due to long-lived isotopes. We determine the rates of events induced by the background that are reconstructed as Compton events in the simulated COSI data. We find that the extragalactic background
photons dominate at low energies (<660 keV), while delayed activation from
cosmic-ray primaries (
proton/alpha) and albedo
photons dominate at higher energies. As part of this work, a comparison at low latitude (<1 deg) between recent measurement of the SAA by the High-Energy Particle Detector (HEPD-01) on board the China Seismo-Electromagnetic Satellite (CSES-01) and the AP9/AE9 model has been made, showing an overestimation of the flux by a factor 9 by the model. The systematic uncertainties associated with these components are quantified. This work marks a major step forward in estimating and understanding the expected background rates for the COSI satellite mission.
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All authors Savitri Gallego, Uwe Oberlack, Jan Lommler, Christopher M. Karwin, Francesco Fenu, Valentina Fioretti, Andreas Zoglauer, F.M. Follega, A. Perinelli, Roberto Battiston, Roberto Iuppa, E. Steven Boggs, Saurabh Mittal, Pierre Jean, Carolyn Kierans, H. Dieter Hartmann, A. John Tomsick
Earth and Planetary Astrophysics
Ringed versus Ringless Worlds: How Poynting-Robertson Drag Shapes Rings across the Solar System
Ryuki Hyodo and Shigeru Ida
Planetary rings are not only ubiquitous around the
giant planets in the outer
Solar System, but have also been discovered around several small distant bodies. In contrast, no rings have been observed around any inner
Solar System objects. To constrain the dynamical origin of this ringed-versus-ringless dichotomy, we employ a numerically cross-checked analytical model of gigayear-scale Poynting-Robertson (PR) drag due to the
solar flux acting on an isolated particle, expressed as a function of the host body's heliocentric distance \(\,a_{\mathrm{pla}}\) and the particle radius \(\,r_{\mathrm{par}}\). Here we show that, in the absence of additional perturbations, PR drag alone can explain the observed ring architecture of the
Solar System: outer
planets and Centaurs/TNOs are able to retain rings for the age of the
Solar System, whereas any rings around the inner
planets are removed on much shorter timescales. Because the PR-drag lifetime scales steeply with heliocentric distance \(\bigl(\tau_{\mathrm{decay}}\propto a_{\mathrm{pla}}^{2} \,r_{\mathrm{par}}\bigr)\), we predict that forthcoming surveys will reveal an ever-growing population of ring-bearing bodies in the distant
Solar System.
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Cosmology and Nongalactic Astrophysics
Primordial black hole formation from the merger of oscillons
Kentaro Kasai and Naoya Kitajima
We show that the merger of oscillons results in a broad spectrum of the oscillon mass. A huge number of oscillon samples obtained from numerical
lattice simulations reveal that the oscillon mass distribution has an exponential tail in a heavy-mass region. This enables us to infer the fractional abundance of heavy oscillons. Using the criterion for the
primordial black hole (PBH) formation from the oscillon collapse obtained in previous studies, we estimate the abundance of PBHs and conclude that a sizable number of PBHs can be produced from oscillons. It can be an alternative PBH formation mechanism without employing the tuning of the inflaton potential to enhance the small-scale density fluctuations in the conventional PBH formation scenario.
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High Energy Astrophysical Phenomena
A Dual-Resolution Prescription in the $S_N$ Method for Boltzmann Neutrino Transport I: Proof of Principle and the Resolution of Collision Term
Akira Ito, Ryuichiro Akaho, Hiroki Nagakura et al. (+1 more)
We propose a dual-resolution prescription meant for the Boltzmann
neutrino transport, in which the advection and collision terms are calculated with different angular resolutions in momentum space. The purpose is to address the issue of the low resolution that afflicts the $S_N$ method in the multi-dimensional
neutrino transport simulations for core-collapse
supernovae. We handle with a high resolution the advection term alone, assuming that the collision term does not require such high resolutions. To confirm this surmise as well as our new conversion scheme, from low- to high-angular resolutions and vice versa, we run a couple of experimental one-zone (in space) simulations.
Neutrino scatterings on nucleons are considered with small
recoils fully taken into account whereas the advection term is replaced by the angle- and energy-dependent source terms that are designed to mimic the results of a Boltzmann simulation, inducing the anisotropy in momentum space. For the conversion from a low-resolution distribution function to a high-resolution one, we employ a
polynomial interpolations in the zenith and azimuth directions separately with the number conservation and continuity (and periodicity only in the azimuth direction). We find that this dual-resolution scheme works well and that the current angular resolution employed in the canonical
supernova simulations with our Boltzmann solver or a bit better in the $\phi_\nu$ direction will be sufficient for the collision terms if they are coupled with the advection terms calculated with a high-angular resolution via this prescription.
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All authors Akira Ito, Ryuichiro Akaho, Hiroki Nagakura, Shoichi Yamada
High Energy Astrophysical Phenomena
Evolution of accretion disc-corona in the TDE Candidate AT 2019avd
Haichao Xu, Xinwu Cao, Yanan Wang et al. (+1 more)
X-ray observations of the
tidal disruption event (TDE) candidate AT 2019avd show drastic variabilities in flux and spectral shape over hundreds of days, providing clues on the
accretion disc-corona
evolution. We utilize a disc-corona model, in which a fraction of the gravitational energy released in the disc is transported into the hot corona above/below. Some soft
photons emitted from the disc are upscattered to X-ray
photons by the hot electrons in the optically thin corona. By fitting the NICER observations of AT 2019avd during epochs when the spectra exhibit significant hardening, we derive the
evolution of the mass
accretion rate, $\dot{m}$, and the coronal energy fraction, $f$. Our results show that $f$ decreases with increasing $\dot{m}$, which is qualitatively consistent with that observed in active
galactic nuclei (AGNs), while the slope of this source, $f\propto \dot{m}^{-0.30}$, is much shallower than that of AGNs. We also find that the non-thermal X-ray spectrum in this source is significantly softer than those typically seen in AGNs and black-hole X-ray binaries. We argue that these quantitative differences can be a powerful diagnostic of the underlying
magnetic turbulence, which may imply a stronger
magnetic field within the TDE
accretion disc than that in typical AGNs. It is also found that the
evolution of the fitted neutral hydrogen column density follows a similar pattern to that of the
accretion rate
evolution, which may reflect the accumulation of absorbing material originating from the inflowing streams of
stellar debris and/or other related sources.
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All authors Haichao Xu, Xinwu Cao, Yanan Wang, Andrzej A. Zdziarski
Solar and Stellar Astrophysics
Probing the Physical and Chemical Characteristics of an Extremely Early Class 0 Protostar in G204.4-11.3A2-NE
Hsuan-I Chou, Naomi Hirano and Masayuki Yamaguchi
We have observed the low-mass molecular cloud core G204.4-11.3A2-NE (G204NE) in the direction of Orion B
giant molecular cloud with the Atacama Large Millimeter/submillimeter Array in Band 6. The $\rm 1.3\ mm$ continuum images and visibilities unveil a compact central structure with a radius of $\sim$12 au, while showing no signature of binarity down to 18 au. The bolometric temperature and luminosity of this source are derived to be ${\sim}$33 K and $\sim$1.15 $~L_{\odot}$, respectively. Chemical stratification is observed in dense gas tracers, with C$^{18}$O emission peaking at the continuum position surrounded by the spatially extended emission of N$_2$D$^+$ and DCO$^+$. This implies that the core is in a very early evolutionary stage in which $\rm CO$ depletion occurs in most regions except for a small area heated by the central source. The envelope kinematics indicates a rotating and infalling structure with a central protostar mass of 0.08-0.1 $M_{\odot}$. The protostar drives a collimated
outflow traced by CO, SiO, SO, and H$_2$CO, with misaligned blueshifted and redshifted lobes exhibiting a pair of bow-like patterns. High-velocity jets, extending up to 720 au, are detected in CO, SiO, and SO lines. The jet launching region is likely within twice of the
dust sublimation zone. The absence of a binary signature suggests the
outflows and jets are driven by a single protostar, although a close binary cannot be ruled out. The observed deflection of the
outflows and jet is likely due to turbulent
accretion in a moderately magnetized core.
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Astrophysics of Galaxies
Exploring the Origin of Rejuvenating Gas from MaNGA Nearby Galaxies
Ting-Hsuan Li and Po-Feng Wu
This study investigates the origin of secondary
star formation, i.e., rejuvenation in nearby
galaxies. From the MaNGA IFU survey, we use
stellar absorption features, D$_n$4000 and EW(H$\mathrm{\delta_A}$), to identify regions that started the rejuvenation within the last $\sim$200~Myr and use gas-phase
metallicity as a primary tracer for
accretion of pristine gas, in order to verify the mechanism that triggers the rejuvenation. We compare the
metallicity and the velocity of rejuvenating regions with typical
star-forming regions. We also compare
metallicity gradients, environments, \ion{H}{1} gas fractions, and visual morphologies of
galaxies hosting rejuvenating regions to controlled
star-forming and quiescent
galaxy samples. Overall, we do not find the rejuvenating regions or their hosts show anomalies in
metallicity, kinematics, and visual morphology to the controlled comparison samples. These observations suggest that local rejuvenation is likely fueled by gas already residing within the host rather than accreted from outside, and reflect the short life time of small scale dense gas clouds. On the contrary, if the rejuvenation is fueled by gas
accretion, the chemical and mixing timescale should be much shorter than $\sim100$ Myr so that no chemical and kinematical anomalies are measured. Meanwhile, we report a clear case of a massive quiescent
galaxy brought back to
star-forming by accreting gas. Our method of identifying rejuvenation is simple and effective, and can be applied to large spectroscopic surveys to investigate the origin of rejuvenation across
cosmic time.
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Astrophysics of Galaxies
Tracing Gas Kinematics and Interactions between H II Regions and Molecular Clouds using VLA Observations of Recombination Lines and Hydroxyl
E. Cappellazzo, J. R. Dawson, Mark Wardle et al. (+7 more)
Observational studies of HII region-molecular cloud interactions constrain models of feedback and quantify its impact on the surrounding environment. A recent hypothesis proposes that a characteristic spectral signature in ground state hyperfine lines of hydroxyl (OH) – the OH flip – may trace gas that is dynamically interacting with an expanding HII region, offering a new means of probing such interactions. We explore this hypothesis using dedicated Jansky Very Large Array (VLA) observations of three
Galactic HII regions, G049.205$-$0.343, G034.256+0.145 and G024.471+0.492, in 1–2 GHz continuum emission, all four 18-cm ground-state OH lines, and multiple hydrogen
radio recombination lines. A Gaussian decomposition of the molecular gas data reveals complex OH emission and absorption across our targets. We detect the OH flip towards two of our sources, G049.205$-$0.343 and G034.256+0.145, finding agreement between key predictions of flip hypothesis and the observed multi-wavelength spectra, kinematics and morphology. Specifically, we demonstrate a strong spatial and kinematic association between the OH flip and the ionized gas of the HII regions – the first time this has been demonstrated for resolved sources – and evidence from $^{13}$CO(1–0) data that the expected OH component originates from the non-disturbed gas of the parent cloud. While we detect no flip in G024.471+0.492, we do find evidence of interacting molecular gas traced by OH, providing further support for OH's ability to trace HII region-molecular cloud interactions.
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All authors E. Cappellazzo, J. R. Dawson, Mark Wardle, Trey V. Wenger, Anita Hafner, Dana S. Balser, L. D. Anderson, Elizabeth K. Mahony, M. R. Rugel, John M. Dickey
Instrumentation and Methods for Astrophysics
Ephemeris and Almanac Design for Lunar Navigation Satellites
Keidai Iiyama and Grace Gao
This paper presents almanac and ephemeris message representation for lunar
navigation satellites supporting the Lunar Augmented
Navigation System (LANS). The proposed method combines osculating orbital elements, Chebyshev
polynomials, and
Fourier series to efficiently represent lunar satellite trajectories subject to complex perturbations from lunar
gravity and third-body effects. For the ephemeris, a hybrid Chebyshev–
Fourier formulation improves fitting accuracy over long arcs while maintaining message compactness under the data-size constraint of the LunaNet Interoperability Specification. For the almanac, a compact low-order
polynomial and
Fourier model is introduced to capture mid-term orbital variations over a 15-day fitting arc. The approach is validated for multiple orbit regimes, including 30-hour, 24-hour, and 12-hour elliptical lunar frozen orbits (ELFOs) and a 6-hour polar orbit. Results show that the proposed framework achieves sub-meter position and sub-millimeter-per-second velocity fitting errors within the 900-bit limit for 6-hour ephemeris arcs, and almanac fitting accuracy sufficient for reliable satellite-visibility identification in warm-start operations.
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High Energy Astrophysical Phenomena
Multifaceted Accretion: The Interplay of Turbulence, Resistivity, Thermal Transport, and Dust around Black Holes
Asish Jyoti Boruah, Liza Devi and Biplob Sarkar
Accretion near black holes (BHs) is multidimensional, with
turbulence, resistivity, thermal transport, and
dust dynamics all playing essential roles. In cold
accretion discs (ADs) or the region of an AD where
magnetic fields (MFs) are negligible (or absent), hydrodynamic (HD)
turbulence is probably dominating. However, Magneto-rotational instability (MRI) is the primary cause of
turbulence in ADs. Significant velocity variations and rapid pressure changes are characteristics of turbulent flows, which allow better mixing and more angular momentum (AM) and energy transfer. Also, in
accretion flow (AF), the interaction between
turbulence and resistivity determines the efficiency of energy dissipation and heat transfer. Radiation, convection, and thermal conduction (TC) are the heat transport modes existing in AFs, where TC enables energy transfer in accreting materials via heat flux. Moreover, convection, also generated by
turbulence, significantly impacts the stability of the AD and its vertical structure. The disc may be affected by radiation from the AD surrounding the BH when X-ray emission occurs. The emission from the disc is also affected by
dust particles.
Dust grains near BH are exposed to high temperatures and intense radiation, which might affect the flow characteristics, as seen in Active
Galactic Nuclei (AGN). This chapter highlights the combined effect of
turbulence, resistivity, transport mechanisms, and
dust particles on BH AF. Future studies in this field must thoroughly investigate how
dust, transport mechanisms, and
turbulence interact in the BH
accretion system.
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Astrophysics of Galaxies
A century of change: new changing-look event in Mrk 1018's past
Thomas Dunn, Rebecca McElroy, Mirko Krumpe et al. (+7 more)
We investigate the long-term variability of the known Changing Look Active
Galactic Nuclei (CL AGN) Mrk 1018, whose second change we discovered as part of the Close AGN Reference Survey (CARS). Collating over a hundred years worth of photometry from scanned photographic plates and five modern surveys we find a historic outburst between ~1935-1960, with variation in Johnson B magnitude of ~0.8 that is consistent with Mrk 1018's brightness before and after its latest changing look event in the early 2010s. Using the combined modern and historic data, a Generalised Lomb-Scargle suggests broad feature with P = 29-47 years. Its width and stability across tests, as well as the turn-on speed and bright phase duration of the historic event suggests a timescale associated with long-term modulation, such as via rapid flickering in the
accretion rate caused by the Chaotic Cold
Accretion model rather than a strictly periodic CL mechanism driving changes in Mrk 1018. We also use the modern photometry to constrain Mrk 1018's latest turn-off duration to less than ~1.9 years, providing further support for a CL mechanism with rapid transition timescales, such as a changing mode of
accretion.
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All authors Thomas Dunn, Rebecca McElroy, Mirko Krumpe, Scott M. Croom, Massimo Gaspari, Miguel Perez-Torres, Michael Cowley, Osase Omoruyi, Grant Tremblay, Mainak Singha
Solar and Stellar Astrophysics
A Systematic Search for Gaseous Debris Disks in DESI Early Data Release White Dwarfs
Ziying Ma, Xiaoxia Zhang, Taotao Fang et al. (+5 more)
Detecting gaseous debris disks around white
dwarfs offers a unique window into the ultimate fate of planetary systems and the composition of accreted planetary material. Here we present a systematic search for such disks through the Ca II infrared triplet using the Dark Energy Spectroscopic Instrument (DESI) Early Data Release. From a parent sample of 2706 spectroscopically confirmed white
dwarfs, we identify 22 candidate systems showing tentative emission-line features, which corresponds to a raw occurrence rate of 0.81%, more than ten times higher than previous estimates. The detected emission lines are predominantly weak and require confirmation by follow-up observations. Three of these candidates also exhibit infrared excess in WISE photometry, suggesting a possible coexistence of gas and
dust. However, the high candidate rate indicates that most are likely false positives due to telluric residuals or unresolved binaries. This work demonstrates the potential of DESI spectra for blind searches of rare circumstellar phenomena. The recently released DESI DR1, with its substantially larger spectroscopic sample, will enable searches for more gaseous disks and provide better insights into their occurrence and nature.
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All authors Ziying Ma, Xiaoxia Zhang, Taotao Fang, Junfeng Wang, Jincheng Guo, Xiaochuan Jiang, Zhi-Xiang Zhang, Hu Zou
High Energy Astrophysical Phenomena
XRISM Spectroscopy of the Stellar-mass Black Hole GRS 1915+105
Jon M. Miller, Liyi Gu, John Raymond et al. (+11 more)
GRS 1915$+$105 was the
stellar-mass black hole that best reproduced key phenomena that are also observed in Type-1 active
galactic nuclei. In recent years, however, it has evolved to resemble a Type-2 or Compton-thick AGN. Herein, we report on the first XRISM observation of GRS 1915$+$105. The high-resolution Resolve calorimeter spectrum reveals that a sub-Eddington central engine is covered by a layer of warm, Compton-thick gas. With the obscuration acting as a coronagraph, numerous strong, narrow emission lines from He-like and H-like charge states of Si, S, Ar, Ca, Cr, Mn, Fe, and Ni dominate the spectrum. Radiative recombination continuum (RRC) features are also observed, signaling that much of the emitting gas is photoionized. The line spectrum can be fit by three photoionized emission zones, with broadening and bulk velocities suggestive of an origin in the outer disk atmosphere and/or a slow wind at $r \simeq 10^{6}~GM/c^{2}$. The Fe XXV He-$\alpha$ and Fe XXVI Ly-$\alpha$ lines have a broad base that may indicate some emission from $r \sim 3\times 10^{3}~GM/c^{2}$. These results broadly support a picture wherein the current state in GRS 1915$+$105 is due to obscuration by the irradiated outer disk. This could arise through disk thickening if the Eddington fraction is higher than inferred, but it is more likely due to a warped, precessing disk that has brought the outer disk into the line of sight. We discuss the strengths and weaknesses of this interpretation and our modeling, and possible explanations of some potentially novel spectral features.
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All authors Jon M. Miller, Liyi Gu, John Raymond, Laura Brenneman, Elena Gallo, Poshak Gandhi, Timothy Kallman, Shogo Kobayashi, Junjie Mao, Daniele Rogantini, Megumi Shidatsu, Yoshihiro Ueda, Xin Xiang, Abderahmen Zoghbi
Astrophysics of Galaxies
Magnetic Fields in Massive Star-forming Regions (MagMaR). VI. Magnetic Field Dragging in the Filamentary High-mass Star-forming Region G35.20–0.74N due to Gravity
Jihye Hwang, Patricio Sanhueza, Josep Miquel Girart et al. (+27 more)
We investigate the
magnetic field orientation and strength in the massive
star-forming region G35.20-0.74N (G35), using polarized
dust emission data obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the
Magnetic fields in Massive
star-forming Regions (MagMaR) survey. The G35 region shows a filamentary structure (a length of $\sim$0.1 pc) with six bright cores located along the filament's long axis.
Magnetic field strengths across the G35 region range from 0.2 to 4.4 mG with a mean value of 0.8 $\pm$ 0.4 mG. The mass-to-flux ratio ($\lambda$) varies from 0.1 to 6.0 the critical value. The highest values are found locally around cores, whereas the remains of the filament are subcritical. A H$^{13}$CO$^+$ (3–2) velocity gradient of 29 km s$^{-1}$ pc$^{-1}$ is evident along the filament's long axis, aligned with the
magnetic field direction. At larger scales ($\sim$0.1 pc), the
magnetic field lines appear roughly perpendicular to the filament's long axis, in contrast to the smaller-scale structure ($\sim$0.003 pc) traced by ALMA. The
magnetic field lines could be dragged along the filament as a result of the gas motion induced by the gravitational potential of the filament. Six cores in the filament have similar spacings between 0.02–0.04 pc. The initial filament fragmentation could have produced a core spacing of 0.06 pc, following filament fragmentation theory, and the current core spacing is the result of cores comoving with the gas along the filament. This core migration could occur in a few 10$^4$ years, consistent with high-mass
star formation time scales.
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All authors Jihye Hwang, Patricio Sanhueza, Josep Miquel Girart, Ian W. Stephens, Maria T. Beltrán, Chi Yan Law, Qizhou Zhang, Junhao Liu, Paulo Cortés, Fernando A. Olguin, Patrick M. Koch, Fumitaka Nakamura, Piyali Saha, Jia-Wei Wang, Fengwei Xu, Henrik Beuther, Kaho Morii, Manuel Fernández López, Wenyu Jiao, Kee-Tae Kim, Shanghuo Li, Luis A. Zapata, Jongsoo Kim, Spandan Choudhury, Yu Cheng, Kate Pattle, Chakali Eswaraiah, Panigrahy Sandhyarani, L. K. Dewangan, O. R. Jadhav
Solar and Stellar Astrophysics
Reconnection nanojets associated with a prominence eruption observed with Solar Orbiter/EUI-HRI
Tarhik Wallace and Patrick Antolin
Magnetic reconnection is a proposed mechanism for nanojets associated with coronal heating. We investigate the characteristics of reconnection-driven nanojets just before and during a prominence eruption using the High Resolution Imager (HRI) of the Extreme Ultraviolet imager (EUI) aboard
Solar Orbiter during its perihelion on September 30, 2024. Extreme UV (EUV) images at unprecedented high spatial and temporal resolution from \hrieuv were analysed. The dimensions and propagation speeds of nanojets were estimated and used to estimate the kinetic energies. Nanojet activity was compared with GOES X-ray flux to assess its relation to
flare evolution. The high spatial and temporal resolution in the EUV was found to be essential to fully capture the properties and numbers of reconnection nanojets. Approximately 120 nanojets were detected during the eruption, with 40 analysed in detail. Nanojets exhibited lengths of $200 - 5000$~km, widths of $200 - 500$~km and durations of $2-12$~s. Instant velocities ranged from 150 km~s$^{-1}- 600~$km~s$^{-1}$ with kinetic energies reaching $1.56\times10^{27}$~erg. These nanojets are faster, longer, more energetic and more numerous compared to previous studies. We also find clear signatures of acceleration and deceleration, reflecting
magnetic tension release and reach of new
equilibria. Reconnection events during the eruption were found to be more frequent and energetically intense. Pre-
flare nanojet clustering indicates small-scale reconnection may precede large eruptive activity. These results suggest that nanojets also occur in fully ionised coronal
plasma, playing a role in both quiescent and eruptive
solar activity.
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High Energy Astrophysical Phenomena
The 2025 June 01 Forbush Decrease measured over a range of primary cosmic ray energies
Roger Clay
The 2025 June 01 Forbush Decrease in the terrestrial ground-level flux of
cosmic ray secondaries was recorded by many
cosmic ray systems. This was the deepest such decrease, from the quiescent value of the flux, which has been observed in the past two decades. It resulted from a complex series of
solar events, none of which on its own reached the most extreme level. The extreme depth of this Decrease has enabled measurements of the flux reduction to be made, which would normally be severely limited by particle counting statistics. In particular, here we examine the Decrease phenomenon over a primary
cosmic ray energy range which is rarely accessible, due to the low flux of high energy
cosmic rays. This work considers data mainly from a
muon telescope system which can respond to both unaccompanied
muons and small
cosmic ray air showers, providing data from GeV to mid-TeV energies, where the Forbush Decrease ceases to be statistically observable. This paper examines the depth of the flux Decrease, as a fraction below its quiescent value, over that primary energy range. The progressive development of internal time structure in the flux through the seven days of the phenomenon is also demonstrated.
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