Solar and Stellar Astrophysics
Classifying white dwarfs from multi-object spectroscopy surveys with machine learning
James Munday, Pier-Emmanuel Tremblay, Ingrid Pelisoli et al. (+5 more)
With tens to hundreds of spectra of white
dwarfs being taken each night from multi-object spectroscopic surveys, automated spectral classification is essential as part of efficient data processing. In this study, we design a neural network to classify the spectral type of white
dwarfs using a combination of spectra from the Dark Energy Spectroscopic Instrument (DESI) data release~1 and imaging from Pan-STARRS photometry. The trained network has a near 100% accuracy at identifying DA and DB white
dwarf spectral types, while having an 85-95% accuracy for identifying all other primary types, including metal pollution. Distinct spectral or photometric features map into separate structures when performing a Uniform
Manifold Approximation and Projection (UMAP) dimensionality reduction. Investigating further and looking at multiple epoch spectra, we performed a separate search for objects that have strongly changing spectral signatures using UMAP, discovering 3 new inhomogeneous surface composition ('double-faced') white
dwarfs in the process. We lastly show how machine learning has the potential to separate single white
dwarfs from double white
dwarf binary
star systems in a large
dataset, ideal for isolating a single
star population. The results from all of these techniques show a compelling use of machine learning to boost efficiency in analysing white
dwarfs observed in multi-object spectroscopy surveys, at times replacing the need for human-driven spectral classifications. This demonstrates our techniques as powerful tools for batch population analyses, finding outliers as a form of rare subclass detection, and in conducting multi-epoch spectral analyses.
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All authors James Munday, Pier-Emmanuel Tremblay, Ingrid Pelisoli, Thomas Killestein, Julia Martikainen, David Jones, Antoine Bédard, Paulina Sowicka
Astrophysics of Galaxies
Wiggling Through the ICM: Multi-Resolution Radio Imaging of a Tailed Radio Galaxy in MACS J1354.6+7715
Abdul Gani, Roland Timmerman, Leah K. Morabito et al. (+4 more)
Tailed
radio galaxies are powerful tracers of interactions between active
galactic nuclei (AGN) and the intracluster medium (ICM), providing unique insights into cluster dynamics. We present LOw Frequency ARray (LOFAR) 144 MHz and uGMRT 400 MHz observations of the cluster MACS J1354.6+7715 (z = 0.3967) to investigate the
radio emission associated with its member
galaxies and the cluster environment. The dominant tailed
radio galaxy in the cluster exhibits a sharply bent tail extending over approximately 300 kpc, with the spectral index steepening from approximately -0.46 +/- 0.21 near the AGN core to approximately -2.43 +/- 0.30 in the outermost regions. Synchrotron modelling of the tail yields a radiative age of 150 +/- 10 Myr, implying a
galaxy velocity of 1956 +/- 130 km s^-1, which is of order ~ 0.9 times the escape velocity. We find no evidence of relics or
halos in our
radio images, and the X-ray morphology from Chandra appears relatively undisturbed, suggesting that the system is a pre-merging candidate. Our results indicate that the
radio galaxy is undergoing its first infall into the cluster, providing an excellent laboratory for studying the impact of the ICM on AGN activity and
galaxy evolution, and demonstrating how multi-frequency
radio observations of tailed
galaxies can uniquely probe both AGN lifecycles and the early stages of cluster assembly.
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All authors Abdul Gani, Roland Timmerman, Leah K. Morabito, Ruta Kale, Satish S. Sonkamble, Arpan Pal, Sravani Vaddi
Astrophysics of Galaxies
The GMRT archive atomic gas survey – III. Comparative Study of Dark Matter Halos in Nearby Galaxies
Sougata Sarkar, Prerana Biswas, Veselina Kalinova et al. (+3 more)
The distribution of dark matter in the inner regions of
galaxies poses a key challenge for small-scale {\Lambda}CDM cosmology. While cold dark matter simulations predict cuspy inner density profiles, observations of low surface brightness (LSB) and
dwarf galaxies often favour cored profiles, an issue known as the cusp-core problem. We investigate this problem by comparing four dark matter
halo profiles: NFW (cuspy), Einasto (intermediate), Burkert (cored), and pseudo-isothermal (pISO) (cored) in a pilot sample of $11$
galaxies from the GMRT archive atomic gas survey (GARCIA). We have performed mass modelling using Markov Chain Monte Carlo (MCMC) techniques, utilising rotation curves derived from robust 3D Kinematic modelling. Baryonic contributions from
stars derived using
stellar kinematics based on $3.6\mu\mathrm{m}$ or $r$-band photometry via Multi-Gaussian Expansion (MGE) combined with Jeans Anisotropic Model (JAM) and from gas, calculated directly from the gas surface density (HI + He) without assuming any predefined functional form, are included. Our mass modelling shows that all
halo profiles provide statistically good fits, yielding consistent estimates of
halo mass and
stellar mass-to-light ratio. To validate our analysis, we examine the
stellar-to-
halo mass relation and find broad agreement with empirical models. Non-parametric density profiles derived from
baryon-subtracted rotation curves show that NFW fits the inner regions best, while all profiles converge in the outskirts. Future studies with a larger sample from GARCIA will be helpful in refining this trend and addressing the cusp-core issue in greater depth.
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All authors Sougata Sarkar, Prerana Biswas, Veselina Kalinova, Nirupam Roy, Narendra Nath Patra, Sushma Kurapati
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Impact on Inferred Neutron Star Equation of State due to Nonlinear Hydrodynamics, Background Spin, and Relativity
Joseph Bretz and Hang Yu
Tidal interaction is a unique, detectable signature in gravitational wave signals from inspiraling binary
neutron stars (BNSs), which can be used to constrain the
neutron star (NS) equation of state (EoS). The
tidal interaction is resonantly amplified as the orbital frequency approaches the NS fundamental mode (f-mode) frequency. It has been shown that the exclusion of
tidal resonance in parameter estimation leads to a significant bias in the inferred NS
tidal deformability and hence the NS EoS [Pratten et al. PRL 129, 081102 (2022)]. The strength and location of
tidal resonance depend sensitively on the f-mode frequency, which is typically modeled using its universal relation with the
tidal deformability that is derived for an isolated, non-spinning NS assuming only linear fluid perturbations. In a BNS inspiral, the f-mode frequency can be corrected by at least three known effects: nonlinear hydrodynamics, background
spin, and relativity. We use
Hamiltonian Monte Carlo simulations to estimate the systematic bias on
tidal deformability when each frequency correction is ignored. Our study considers both loud, individual events and the stacking of a population of detections. Both scenarios are expected when the next-generation detectors are available with a sensitivity level increased by about an order of magnitude.
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Astrophysics of Galaxies
How Do Disk Galaxies Form?
Vadim A. Semenov
In both observed and simulated
galaxies, disk morphologies become more prevalent at higher masses and lower
redshifts. To elucidate the physical origin of this trend, we develop a simple analytical model in which
galaxy morphology is governed by the competition between rotational support and
turbulence in a gravitational potential of a dark matter
halo and the
galaxy itself, and a disk forms when the potential steepens due to the accumulation of
baryons in the
halo center. The minimum
galaxy mass required for this transition decreases with an increasing dark matter contribution within the
galaxy, making more concentrated
halos more prone to forming disks. Our model predicts that
galaxy sizes behave qualitatively differently before and after disk formation: after disks form, sizes are governed by the
halo spin, in agreement with classical models, whereas before disk formation, sizes are larger and set by the scale on which turbulent motions, which dominate over rotation, can be contained. We validate our model against the results of the TNG50 cosmological simulation and, despite the simplicity of the model, find remarkable agreement. In particular, our model explains the increase with
redshift in the critical
halo mass for disk formation, reported in both simulations and observations, as a consequence of the
evolution of the
halo mass-concentration and baryonic mass-
halo mass relations. This
redshift trend therefore supports the recent proposal that it is the steepening of the gravitational potential that primarily drives disk formation, while other effects discussed in the literature, such as potential deepening and hot gaseous
halo formation, can still play important roles in the transition from early turbulent to dynamically cold disks.
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High Energy Astrophysical Phenomena
Tidal disruption event rates across cosmic time: forecasts for LSST, Roman, and JWST and their constraints on the supermassive black hole mass function
Mitchell Karmen, Suvi Gezari, Colin Norman et al. (+1 more)
Measuring the mass distribution of supermassive black holes (SMBHs) over
cosmic time remains particularly challenging for the low mass (M_BH<10^8 M_sun) population at z>1. This population is also the most sensitive to SMBH seeding and early growth models. In this work we construct a semi-empirical model for the
redshift evolution of the TDE rate under multiple SMBH mass function prescriptions, and show that the observed
redshift-dependent rate of TDEs is very sensitive to the SMBH mass function and its
evolution with
redshift. We further incorporate
galaxy-scale processes that evolve with
redshift – namely, increasing
galaxy nuclear stellar densities, enhanced
galaxy-
galaxy merger rates,
dust obscuration, and a possible top-heavy IMF at early
cosmic times – and quantify their combined impact on the TDE rate. We find that including these effects generally results in a volumetric TDE rate that increases with
redshift until a maximum near
cosmic noon, before declining at higher
redshift where SMBHs that can disrupt
stars become increasingly scarce. We forecast TDE rates in the Rubin LSST and the Roman High Latitude Time Domain Survey, alongside expectations for serendipitous TDE rates in the JWST COSMOS-Web survey. Finally, we provide a methodology for using a flux-limited survey of TDEs in LSST to directly constrain the
redshift evolution of the SMBH mass function.
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All authors Mitchell Karmen, Suvi Gezari, Colin Norman, Muryel Guolo
Cosmology and Nongalactic Astrophysics
Oort Cloud Bombardment by Dark Matter
Jeremy Mould
The realization that
primordial black holes (PBHs) might be some fraction of the dark matter begged the question, how often do PBHs enter the
solar system? For a Neptune radius
solar system the answer is, rarely. For an Oort cloud sized system the answer is different. Simulations of bombardment of the Oort cloud by dark matter suggest that dislodgement of protocomets and their entry into the inner
solar system can match the observed frequency of comets, if that PBH fraction is high enough. Comets were traditionally considered as messengers, usually omens. After 50 years of puzzlement regarding dark matter, we need a hint from the dark universe about the size and nature of dark matter particles.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Primordial black holes as cosmic accelerators of light dark matter: Novel direct detection constraints
Sk Jeesun, Anirban Majumdar and Rahul Srivastava
Current multi-tonne-scale dark matter (DM) detectors are largely incapable of detecting light dark matter from the
Galactic halo due to the energy threshold limitations of their
recoil measurements. However,
primordial black holes (PBHs) can evaporate via Hawking radiation to particles whose energies are set by the black hole temperature. Consequently, weakly interacting light dark matter (or dark radiation) particles produced in this manner can reach the Earth with sufficient flux and kinetic energy above the experimental thresholds. This opens up a novel avenue to probe the light dark sector in terrestrial experiments. In this work, we explore this possibility by considering fermionic DM produced through PBH evaporation and investigating its electron
recoil signatures in direct detection experiments. We analyze both energy independent (constant) and energy dependent (scalar and vector mediated) DM-electron interactions, highlighting the strong dependence of the
recoil spectra on the underlying Lorentz structure of the interaction. In addition, we also account for the attenuation effects due to the loss of kinetic energy while DM traverses through Earth's crust, which can significantly modify the incoming DM flux. Incorporating these effects carefully, we place constraints on light DM using the electron
recoil data from XENONnT, LZ, and PandaX-4T. Finally, we also discuss the detection prospects of such dark matter in current and future generation
neutrino detectors, such as Super-Kamiokande and Hyper-Kamiokande.
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Solar and Stellar Astrophysics
Diagnostics for the solar chromosphere using neutral carbon Rydberg lines
R.P. Dufresne, C.M.O. Osborne and G. Del Zanna
Diagnostics for the
solar chromosphere are relatively few compared to other parts of the atmosphere. Despite this, hundreds of Rydberg lines emitted by neutrals in this region have been observed at UV wavelengths. Here, we investigate their diagnostic potential by modelling the lines emitted by neutral carbon using recent atomic data. We use the radiative transfer code Lightweaver to explore how they form and how they respond to temperature, density and micro-turbulent velocity perturbations in the atmosphere. To simplify the modelling, we investigate lines emitted from levels with principal
quantum number $n\geq10$, which are expected to be in Saha-Boltzmann
equilibrium with the ground state of the singly-charged ion. Optical depth effects are apparent in the lines and their response to atmospheric perturbations suggest that they will be useful in reconstructions of the atmosphere using inversions. The study opens the way for using many such lines emitted by multiple elements over a range of heights, a large number of which will be observed by the forthcoming
Solar-C EUV High-throughput Spectroscopic
Telescope (EUVST).
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Instrumentation and Methods for Astrophysics
The EXoplanet Climate Infrared TElescope (EXCITE): A balloon-borne mission to measure spectroscopic phase curves of transiting hot Jupiters
Timothy D. Rehm, Caitlyn Altermatt, Lee Bernard et al. (+26 more)
The
EXoplanet Climate Infrared
TElescope (EXCITE) is a balloon-borne mission dedicated to measuring spectroscopic phase curves of hot Jupiter-type
exoplanets. Phase curve measurements can be used to characterize an
exoplanet's longitude-dependent atmospheric composition and energy circulation patterns. EXCITE carries a 0.5 m primary mirror and moderate resolution diffraction-limited spectrograph with spectral coverage from 0.8–3.5 um. EXCITE is designed to fly from a long-duration balloon (LDB). EXCITE will observe through the peak of a target's spectral energy distribution (SED) and through spectral signatures of hydrogen and carbon-containing molecules. In this paper, we present the science goals of EXCITE, detail the as-built instrument, and discuss its performance during a 2024 engineering flight from Fort Sumner, New Mexico.
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All authors Timothy D. Rehm, Caitlyn Altermatt, Lee Bernard, Andrea Bocchieri, Nathaniel Butler, Oliver Carey, Ryan C. Challener, John Hartley, Kyle R. Helson, Daniel P. Kelly, Kanchita Klangboonkrong, Andrei L. Korotkov, Maura Lally, Edward Leong, Nikole K. Lewis, Steven Li, Michael Line, Stephen F. Maher, Ryan McClelland, Lorenzo V. Mugnai, Peter C. Nagler, C. Barth Netterfield, Vivien Parmentier, Enzo Pascale, Jennifer Patience, L. Javier Romualdez, Paul A. Scowen, Gregory S. Tucker, Ingo Waldmann
Earth and Planetary Astrophysics
A Two-Dimensional Analytic Solution for the Generation of Hyperbolic Trajectories Via A Single Close Encounter with Applications To Interstellar Objects
Hayden Monk and Darryl Z. Seligman
The discovery of interstellar interlopers such as 1I/`Oumuamua, 2I/Borisov, and 3I/ATLAS have highlighted the necessity of understanding the dynamical pathways that eject small bodies from planetary systems into
hyperbolic trajectories. In this paper we examine the orbital elements of particles in the restricted three-body problem prior to and post scattering onto
hyperbolic trajectories by massive perturbers. Building on previous work, we calculate closed-form – but approximate – analytic criteria that map pre- to post-encounter orbital elements. An application of these equations demonstrates that ejection occurs most efficiently when the orbital eccentricity of the massless test particle exceeds a minimum threshold, $e\gtrsim0.4$. The primary driver of the final eccentricity is the component of the perturber-centric velocity projected along the direction of motion of the perturber. These analytic criteria are then benchmarked and validated against numerical simulations which demonstrate that they provide a reasonably good zeroth-order approximation for ejection behavior. However, system-specific cases will generally require numerical simulations in addition to this analytic construction. The methodology is applied to (i) the
solar system and exoplanetary systems (ii) $\beta$ Pictoris and (iii) HR 8799 to evaluate the pre-scattering orbits of ejected particles. This method provides a transparent and computationally efficient tool for identifying orbits within a given system from which interstellar objects are efficiently ejected via a single scattering event from a massive perturber.
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Solar and Stellar Astrophysics
The Frequency of Solar Eclipses for a Given Place: A New Approach to a Classic Question
Graham Jones, Renate Mauland-Hus, Frank Thomas Tveter et al. (+6 more)
In a classic 1982 paper in this journal, Jean Meeus used a statistical approach for finding the mean frequency of a total and an annular eclipse of the Sun at a given place on the surface of the Earth. In this current paper we tackle the problem again, taking advantage of the much greater computing power now available. We obtain narrower estimates of once every 373 $\pm$ 7 years for a total eclipse, and once every 226 $\pm$ 4 years for an annular eclipse. In addition, we obtain a result of once every 2.59 $\pm$ 0.02 years for a partial eclipse. We provide further insights into the "latitude effect", showing that
solar eclipses occur most frequently around the Arctic and Antarctic Circles. We also show how the gradual shift of aphelion and perihelion with respect to the seasons produces a $\sim$21,000-year cycle in the frequency of eclipses in the Northern and Southern Hemispheres.
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All authors Graham Jones, Renate Mauland-Hus, Frank Thomas Tveter, Anne Buckle, Sébastien Emonet, Adalbert Michelic, Anna Smith, David Usken, Steffen Thorsen
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Near-Resonant Thermal Leptogenesis
Angus Spalding
We study leptogenesis in the quasi-degenerate but non-resonant regime. Expanding the CP asymmetry parameter near degeneracy and imposing the conservative non-resonance condition that the mass splitting must be much greater than the right-handed
neutrino decay rates $\Delta M > 100\Gamma_i$, yields the universal upper bound $\epsilon \leq 1/200$, independent of both the effective
neutrino masses and the right-handed
neutrino mass. We investigate vanilla and flavoured near-resonant leptogenesis and find that successful leptogenesis by right-handed
neutrino decays can occur for $M \gtrsim 100~\mathrm{GeV}$ independent of washout regime, extending the viable parameter space of thermal leptogenesis down to the electroweak scale without invoking resonance. We also analyse near-resonant thermal leptogenesis during reheating and show that successful
baryon asymmetry generation is compatible with reheating temperatures as low as $T_{RH}\simeq 10\rm GeV$ without relying on non-thermal production. Finally, we present a consistent framework for incorporating flavour effects in near-resonant leptogenesis during reheating. Overall, near-resonant thermal leptogenesis offers a controlled alternative regime to resonant leptogenesis, lowering the leptogenesis scale to the electroweak scale, without reliance on a disputed regulator used in resonant leptogenesis.
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Cosmology and Nongalactic Astrophysics
Measurement of the Hubble constant using the Dark Energy Survey Year 6 Gold galaxy catalogue and the fourth Gravitational-Wave Transient Catalogue
Isaac McMahon, Danny Laghi, Marcelle Soares-Santos et al. (+9 more)
Gravitational wave (GW) standard sirens enable independent measurements of the Hubble constant $H_0$. In the absence of electromagnetic counterparts, the 'dark siren' method statistically correlates GW events with potential host
galaxies. We present a measurement of $H_0$ using GWTC-4.0 (the fourth Gravitational-Wave Transient Catalogue) combined with the Dark Energy Survey Year 6 Gold photometric
galaxy catalogue. Using the gwcosmo pipeline, we jointly infer cosmological and GW population parameters. We analyse the impact of
galaxy catalogue properties on the inference, identifying significant features in the
galaxy redshift distribution which can introduce biases. By restricting the
galaxy catalogue to $0.05<z<0.50$ to maintain consistency with a uniform in comoving volume
galaxy distribution, we obtain a result of $H_0 = 71.7^{+22.7}_{-18.3}\;\text{km}\;\text{s}^{-1}\;\text{Mpc}^{-1}$ from dark sirens and $H_0=73.1^{+11.9}_{-8.5}\;\text{km}\;\text{s}^{-1}\;\text{Mpc}^{-1}$ when combined with the bright siren GW170817. This study demonstrates the adaptation of deep
galaxy catalogues for GW cosmology, highlighting key challenges and methodologies essential for maximizing the potential of next-generation
galaxy surveys.
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All authors Isaac McMahon, Danny Laghi, Marcelle Soares-Santos, Kendall Ackley, Gergely Dálya, Yavuz Gençel, David Sánchez-Cid, Felipe Andrade-Oliveira, Sean MacBride, Christian Chapman-Bird, Rachel Gray, Alexander Papadopoulos
Astrophysics of Galaxies
J.V.Wijesekera, M.P.Koprowski, J.S.Dunlop et al. (+5 more)
Aims. We derive a dependence of the IRX on UV slope $\beta$,
stellar mass $M_\ast$, and
redshift out to $z \simeq 5$, and establish consistent functional relations that can be used for correcting the UV/optical-selected
galaxy samples for the effects of
dust absorption. Methods. This work is based on a $K$-band selected sample of $\sim 10^5$
star-forming
galaxies detected in the UDS and COSMOS fields. Quiescent sources and known starbursts are removed, and the IR luminosities are established through stacking in FIR Herschel and JCMT maps. UV slopes are found from SED fits and stacked IRX values are derived by taking the median of individual IRX measurements in bins of $\beta$, $M_\ast$ and
redshift. Results. While our best-fit IRX-$\beta$ relation is consistent with a Calzetti-like attenuation curve at $\beta\gtrsim -1$, at bluer values the IRX seems to increase with
redshift due to different mass-completeness limits imposed. When deriving the IRX-$\beta$ relation in
stellar-mass bins, a systematic trend is found, where the effective slope of the attenuation law becomes progressively shallower with increasing mass. We incorporate this into the IRX-$\beta$ relation through the slope of the underlying reddening law, $dA_{1600}/d\beta$, being a quadratic function of $\log(M_\ast/{\rm M_\odot})$. Expressing IRX as a function of the
stellar mass we find a tight correlation, with IRX rising monotonically with mass but exhibiting a clear high-mass turnover at $z\lesssim 2-3$, consistent with suppressed cold-gas
accretion and
dust growth in massive systems.
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All authors J.V.Wijesekera, M.P.Koprowski, J.S.Dunlop, K. Lisiecki, D.J.McLeod, R.J.McLure, M.J.Michałowski, M.Solar
Astrophysics of Galaxies
Nonlinear Saturation of the Acoustic Resonant Drag Instability
Ben Y. Israeli, Jonathan Squire, Eric Moseley et al. (+1 more)
Resonant drag instabilities (RDIs) are a novel type of
dust/fluid instability relevant to a diverse range of astrophysical environments. They are driven by a resonant interaction between streaming
dust and waves in a background medium, which results in
dust density fluctuations and amplification of the waves. This broad class of instabilities includes recently-proposed modes incorporating acoustic and magnetohydrodynamic waves, as well as the well-studied disk streaming instability. As the study of RDIs is at an early stage, their
evolution beyond the linear regime is not well understood. In order to make inroads into the nonlinear theory of RDIs, we performed simulations of the simplest case, the acoustic RDI, in which sound waves in a gas are amplified by interaction with supersonically streaming
dust. This particular instability is of interest both due its potential relevance in various poorly ionized environments, and due to its resemblance to the fast magnetosonic RDI. We find that the nonlinear growth and saturation of the instability are characterized by a balance between time scales of instability growth and turbulent eddy turnover. The simulations demonstrate a saturated state possessing an anisotropic outer forcing range in which this balance is maintained, and suggest the presence of an isotropic turbulent inertial range below this scale. By presenting a model for the nonlinear growth and saturated state of the acoustic RDI, this work provides a framework for further study of the nonlinear behavior of this and other RDIs.
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All authors Ben Y. Israeli, Jonathan Squire, Eric Moseley, Amitava Bhattacharjee
Solar and Stellar Astrophysics
Early Stages of Protostellar Disk Evolution: A Link to the Initial Cloud Core
Majd Noel, Rahul Khanna, Shahram Abbassi et al. (+2 more)
We study the structure and
evolution of the very early protostellar disk (“protodisk”) just after protostar formation, where disk self-
gravity dominates and the
stellar contribution is dynamically minor. The disk redistributes angular momentum outward through
outflows and gravitational torques, thereby helping to resolve the angular momentum problem of
star formation. We develop a self-similar model and carry out a parameter study that examines disk stability as a function of the key drivers of early
evolution, notably the infall rate from the envelope and the strength of the gravitational torques. The mass infall rate onto the disk is estimated to be that from the collapse of a Bonnor-Ebert sphere. Our results indicate that protostellar disks that form from more unstable initial cores are more likely to be Toomre-unstable. We also find that the specific angular momentum of young protostellar disks lie in the range $10^{19}\text{--}10^{20}\,{\rm cm^2\,s^{-1}}$. We find distinct power-law profiles of physical quantities in the protodisk stage, including a rotation velocity profile that is shallower than the Keplerian profile that would be established at a later stage. As a rough validity window, our assumptions are most secure during the first $\lesssim 2\times 10^{3}$\,yr after protostar formation and may plausibly extend to $\sim(0.5\text{--}1)\times 10^{4}$\,yr under weak
magnetic braking and strong infall.
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All authors Majd Noel, Rahul Khanna, Shahram Abbassi, Sami Dib, Shantanu Basu
Cosmology and Nongalactic Astrophysics
Unclustered tracers remain unclustered: the lack of primordial non-Gaussianity response of bias-zero tracers
Celia Merino, Santiago Avila, A. G. Adame et al. (+3 more)
Constraining
primordial non-Gaussianities (PNG) is one of the main goals of new-generation large-scale
galaxy surveys. It had been proposed that unclustered tracers (with bias $b_1=0$) could be optimal for PNG studies, and that these could be found by selecting
galaxies in bins of their local density. Here, we test this hypothesis in state-of-the-art simulations from the PNG-UNITsim suite with local $f_{\rm NL}=100$ and $f_{\rm NL}=-20$. We consider different parent tracer catalogues: all
halos together,
halos in large mass bins, and HOD models for LRGs and QSO. We then classify these tracers by their local density ($\delta_{t,R}$) and measure the linear bias ($b_1$) and PNG-response ($b_\phi$). Most $\delta_{t,R}$ bins show a PNG-response compatible with $b_\phi=0$ for all
halos or the low-mass bin (log$M<11$). For high-mass
halos (log$M>$12), QSO or LRG, we recover a trend closer to the universality relation ($b_\phi = 2 \delta_{\rm crit}(b_1-1)$) for $b_1>1$, but the $b_\phi(b_1)$ curve flattens to 0 below $\vert b_1\lvert<1$. Hence, we find $b_\phi\approx0$ for all bias-zero tracers considered. The complex $\delta_{t,R}$-based selection causes their clustering to strongly deviate from simple assumptions, namely the universality relation and Poisson shot noise, hindering their capability to constrain PNG.
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All authors Celia Merino, Santiago Avila, A. G. Adame, A. Anguren, V. Gonzalez-Perez, J. Meneses-Rizo
Solar and Stellar Astrophysics
EPISODE III: The Nested Jet/Outflow Morphology of EC 53 Revealed by JWST and ALMA
Seonjae Lee, Jeong-Eun Lee, Chul-Hwan Kim et al. (+8 more)
We present an extensive study of the structure and kinematics of the jet and
outflow of EC 53, a Class I protostar with a quasi-periodic variability, using combined James Webb Space
Telescope (JWST) and Atacama Large Millimeter/submillimeter Array (ALMA) observations. ALMA continuum observations resolve a compact disk with a radius of $\sim$0.14\arcsec\ (60\,au). Scattered light from the
outflow cavity is prominent in the short-wavelength NIRCam and NIRSpec observations, revealing only the southeast nearside lobe. We detected 27 H$_2$ emission lines tracing a narrow, cone-shaped structure within the
outflow cavity. A high-velocity ionized jet is detected in several forbidden atomic lines, characterized by a position angle of 142\degree, an opening angle of 1.4\degree, and an estimated
geometric launching radius of at most $\sim$40\,au. Mid-infrared CO ro-vibrational emission lines, stronger in the P-branch, show a similar distribution to the H$_2$ emission and are likely to originate from hot gas within the
outflow cavity. CO and C$_2$H emission lines detected by ALMA trace slower, colder
outflow components and cavity walls. The spatial and kinematic stratification between the hot atomic and molecular components and the colder molecular gas is consistent with predictions from MHD disk wind models, although envelope material entrained by a wide-angle wind or jet may also contribute. Our analysis highlights the powerful synergy between JWST and ALMA in advancing the understanding of protostellar jets and
outflows across multiple spatial and physical scales.
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All authors Seonjae Lee, Jeong-Eun Lee, Chul-Hwan Kim, Seokho Lee, Doug Johnstone, Gregory J. Herczeg, Joel Green, Logan Francis, Yao-Lun Yang, Hyundong Lee, Nagayoshi Ohashi
Instrumentation and Methods for Astrophysics
Expanding the Horizon of Black Hole Imaging with AtLAST
Kazunori Akiyama, Mariafelicia De Laurentis, Ziri Younsi et al. (+8 more)
The Event Horizon
Telescope (EHT) has directly resolved and imaged two supermassive black holes and opening a new window on black hole physics. However, the current array is limited to only these two brightest nearby targets. This white paper outlines how future EHT upgrades, anchored by the Atacama Large Aperture Submillimeter
Telescope (AtLAST), will enable a transformative expansion of the accessible population of event-horizon-scale sources. By substantially improving sensitivity and multi-frequency capabilities, EHT+AtLAST will enable demographic studies of black hole growth,
accretion physics, and jet launching across a wide range of masses, environments, and
accretion states.
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All authors Kazunori Akiyama, Mariafelicia De Laurentis, Ziri Younsi, Yuto Akiyama, Dominic W. Pesce, Geoffrey C. Bower, Kazuhiro Hada, Jens Kauffmann, Shoko Koyama, Kotaro Moriyama, Derek-Ward Thompson
Solar and Stellar Astrophysics
Wide binaries without viable bound Newtonian orbits
L. Pasquini, R. Saglia, F. Patat et al. (+7 more)
Context. Wide binaries offer a unique opportunity to test
gravity in the low acceleration regime, where deviations from Newtonian dynamics may appear. Aims. We use high-resolution VLT-ESPRESSO archival spectra to study 26 wide binaries with projected separations larger than 13,000 AU. By combining precise radial velocities with
Gaia proper motions and parallaxes, we aim to test whether these systems are consistent with Newtonian
gravity in the low acceleration regime. Methods. We use multiple radial velocity measurements and
stellar parameters to remove systems affected by unresolved triples, chance
alignments, or young systems. For the remaining binaries, we combine radial velocities (corrected for convective shift and gravitational
redshift) with
Gaia proper motions, parallaxes, and positions to attempt bound Newtonian orbital solutions Results. Fourteen of the 26 initial systems were discarded: 12 due to radial velocity variability indicating unresolved close binaries, one hosting a faint
Gaia companion, and one too young. Of the remaining 12, nine can be fitted with bound orbital solution, while three show velocity differences too large to be reconciled with any bound Newtonian orbit. Conclusions. For the three systems that cannot be fitted with a bound orbit, repeated radial velocity observations allow us to confidently exclude, with one possible exception, unresolved triple
stellar companions or massive close-in
planets as causes. Given their likely large 3-dimensional separations, these binaries may have been dynamically perturbed or disrupted by
stellar encounters or
Galactic tides, and may no longer be gravitationally bound. This highlights how utmost caution must be applied when studying wide binaries as isolated systems.
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All authors L. Pasquini, R. Saglia, F. Patat, L. Berni, D. Bossini, L. Magrini, H. Ludwig, M. T. Murphy, J.R. de Medeiros, J. Chanamé
High Energy Astrophysical Phenomena
An Afterglow Study of the "New Year's Burst" GRB 220101A
Agniva Roychowdhury, Tuomas Kangas, Andrew Fruchter et al. (+12 more)
We present a detailed broadband afterglow study of GRB 220101A ($10^4\lesssim\Delta T\lesssim10^7$ s) combining multi-wavelength data from soft X-rays until 6 GHz. The afterglow light curves in both X-ray and optical show distinct steepening around $\sim9$ days, followed by a sharp post-break decay index of $\sim2.99\pm0.10$. We fit the light curves using the afterglow modelling package afterglowpy for both Top-hat and Gaussian jets for different values of the electronic participation fraction $\xi$ from 0.01 to 1.0 and find that, although the
radio behavior is well described by the $\xi=1.0$ case, the required circumburst medium (CBM) densities are very low, $<10^{-4}$ cm$^{-3}$. However, the resulting energy requirements are modest, $\sim10^{52}$ erg, with an electron energy distribution (EED) index $p\sim2.05$. Similar results are also obtained from an analytic model fit to the light curve, except the predicted $p$ is higher, $\sim2.40$. The observed post-break decay index of $2.99$ is at least 5$\sigma$ away from $p$, which is one of the steepest observed so far. We also find that when ignoring the
radio observations, the CBM density is raised by a few orders of magnitude to $\sim0.01$ cm$^{-3}$ for $\xi=1.0$, still far from the expected ISM density ($>1$ cm$^{-3}$) of GRB environments, which are highly
star forming regions. Similarly low ISM densities have been seen in modeling of other LAT GRBs as well, especially ones with reverse-shock features (e.g., GRBs 130427A, 160509A and 160625B), thereby hinting at either an issue with the standard model or possible evacuated cavities where GRBs explode.
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All authors Agniva Roychowdhury, Tuomas Kangas, Andrew Fruchter, A. Pe'er, K. Bhirombhakdi, J. Graham, K. Misra, A. J. Levan, B. Cenko, A. Cucchiara, V. Cunningham, B. P. Gompertz, D. Perley, J. Racusin, N. R. Tanvir
Solar and Stellar Astrophysics
The incidence of LBV variability in the LMC
V. M. Kalari, J. S. Vink, C. Furey et al. (+3 more)
Luminous blue variables (LBVs) exhibit unique variability features, characterized by episodic outbursts ($>$1 mag) accompanied by spectroscopic changes (S Dor variables). It is debated if all massive
stars undergo an LBV-like phase during their
evolution, or instead LBVs are exotic phenomena. We aim to quantify the incidence of LBV-like variability in the blue supergiant (BSgs) population of the Large Magellanic Cloud (LMC) using the OGLE survey. Here, we extend previous work in the Small Magellanic Cloud to the LMC, where we examine the light curves of 87 B Supergiants (BSgs) (out of 254 known BSgs) spanning timescales of twenty years, and 37 objects across a three year timescale for aperiodic variations resembling known S Dor variables. One blue supergiant, [ST92] 4-13 shows S Dor type photometric variations. New spectra of this object reveals a potential change in spectral type compared to the literature classification. However, based on its spectral characteristics and low luminosity and mass, we do not currently classify it as an LBV. Our study highlights the need to classify bona fide LBVs as
stars undergoing both photometric and spectroscopic variations. Based on currently known
stellar population of S Dor variables in the LMC, the lifetime of the S Dor phase is at most $\sim$10$^3$ yrs, in agreement with our duty cycle study based on OGLE data in the SMC. This is orders of magnitude shorter than assumed in literature. Our discovery of LBV-like variability at low luminosities may suggest that S Dor variations could arise from Eddington limit related physics over a wide range of
stellar masses, rather than being linked to a unique evolutionary stage.
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All authors V. M. Kalari, J. S. Vink, C. Furey, R. Salinas, A. Udalski, M. Pawlak
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Impact of higher-order modes on eccentricity measurement in binary black hole gravitational waves
Honglue Tang, Jinzhao Yang, Baoxiang Wang et al. (+1 more)
We investigate the systematic biases in measuring orbital eccentricity for binary black hole (BBH) mergers that arise when higher-order modes (HOMs) of gravitational waves are neglected in waveform modeling. Using
Bayesian inference with the state-of-the-art eccentric,
spin-aligned, higher-mode effective-one-body model SEOBNRv5EHM, we reanalyze six previously suggested eccentric gravitational-wave events–GW190521, GW190620, GW190701, GW191109, GW200129, and GW200208\_222617. Comparing results with its dominant-mode-only counterpart SEOBNRv5E, we find no statistically significant HOM-induced bias in eccentricity for any of these events, including GW190521, whose eccentricity has been debated in the literature. To explore representative parameter regimes vulnerable to HOM omission, we perform a broad zero-noise injection campaign varying detector-frame total mass, mass ratio, eccentricity, inclination, and network SNR. We find that significant systematic biases ($\Delta_e/\sigma > 1$) arise predominantly in systems with relatively high total mass ($M^{\rm det}\gtrsim120M_\odot$), highly asymmetric mass ratios ($q \gtrsim 4$), large inclinations ($\theta_\textrm{JN} \gtrsim 30^\circ$), and high SNRs ($\rho^N_\textrm{mf}\approx50$). Notably, for quasicircular BBHs with approximately $M^{\rm det}\gtrsim140M_\odot$, our results suggest that neglecting HOMs may lead to strong false-positive evidence for nonzero eccentricity. By contrast, for lower-mass systems ($M^{\rm det}\sim100 M_\odot$), HOM exclusion produces negligible eccentricity biases. Our results demonstrate that although current eccentric candidates are not impacted by HOM omission, future eccentricity measurements–particularly for relatively massive, asymmetric, or edge-on systems–require HOM-inclusive waveforms to avoid substantial systematic errors.
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All authors Honglue Tang, Jinzhao Yang, Baoxiang Wang, Tao Yang
High Energy Astrophysical Phenomena
Constraints on cyclotron features and accretion regime in the high-mass X-ray binary 4U 1700-37 from NuSTAR
Lautaro West-Ocampo, Federico A. Fogantini, Enzo A. Saavedra et al. (+6 more)
4U 1700-37 is a wind-fed high-mass X-ray binary hosting a compact object, likely a
neutron star, accreting from O6.5 Iaf+ supergiant HD 153919. Coherent pulsations not firmly detected;
magnetic field strength remains uncertain. We analyze NuSTAR observations to characterize hard X-ray timing and spectral properties, test robustness of candidate cyclotron features, and constrain
magnetic field and
accretion regime. We perform timing and spectral analysis of two observations, modeling spectra with continua used for accreting
pulsars, and use simulations to assess significance of features. No coherent pulsations detected; pulsed fraction constrained below 1.5%. Spectra are well described by absorbed blackbody plus cutoff power-law continuum, showing residuals around 20 keV and 40–50 keV. Features improve fits but do not constitute firm cyclotron detections. Intensity-resolved spectroscopy suggests possible shifts of apparent line centroid. Results favor
neutron-
star magnetic field of 1.7–4.4 $\times 10^{12}$ G and quasi-spherical subsonic
accretion regime with
equilibrium spin period $\sim 1.9$ ks. Analysis provides quantitative constraints on
magnetic field and
accretion physics, helping reconcile discrepant line-energy measurements.
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All authors Lautaro West-Ocampo, Federico A. Fogantini, Enzo A. Saavedra, Jorge A. Combi, Federico García, Pedro L. Luque-Escamilla, Josep Martí, Sylvain Chaty, Juan F. Albacete-Colombo
High Energy Astrophysical Phenomena
$\gamma$-Ray Lines – Signatures of Nucleosynthesis, Cosmic Rays, Positron Annihilation, and Fundamental Physics
Thomas Siegert, Francesca Calore, Pierre Jean et al. (+6 more)
The
nuclear $\gamma$-ray lines in the MeV range of the electromagnetic spectrum hold a vast variety of astrophysical, particle-physical, and fundamental physical information that is otherwise extreme difficult to access. MeV $\gamma$-ray line observations provide the most direct evidence for ongoing nucleosynthesis in
galaxies by measuring freshly produced radioactive isotopes from massive
stars,
supernovae, classical novae, or binary
neutron star mergers. Their flux ratios can determine the low-energy
cosmic-ray spectrum in different objects and of the Milky Way as a whole. Different phases of the interstellar medium are traced by hot nucleosynthesis ejecta, cooling positrons, or
cosmic-ray interactions with molecular clouds. Positron annihilation itself can be considered as an astrophysical messenger as their production and destruction in typical space environments is inevitable. Finally, as-of-yet unknown signatures from beyond standard model physics might have their elusive imprints in $\gamma$-ray lines. This Chapter gives an overview of historical $\gamma$-ray line measurements, newest results, and open questions that may only be solved by a new generation of MeV
telescopes.
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All authors Thomas Siegert, Francesca Calore, Pierre Jean, Mark Leising, Nicolas de Séréville, Gerald H. Share, Vincent Tatischeff, Wei Wang, Meng-Ru Wu
Cosmology and Nongalactic Astrophysics
The Standard siren tests of viable $f(R)$ cosmologies
Yi Zhang, Xuanjun Niu, Xianfu Su et al. (+1 more)
We constrain the Hu-Sawicki and Starobinsky $f(R)$
gravity models utilizing current electromagnetic (PP+CC, Planck and DESI2)
datasets and simulate standard siren catalogs based on the resulting best-fit parameters. We demonstrate that the simulated SS data provide complementary sensitivity to the modified gravitational wave propagation friction term, thereby enhancing the discriminating power between $f(R)$
gravity and the $\Lambda$CDM model. However, we note that standard sirens do not offer a viable resolution to the Hubble tension in this analysis, as the inferred constraints are predominantly driven by the fiducial cosmologies adopted in the simulations. Regarding the specific models, we find that for the Hu-Sawicki scenario, several data combinations favor $F_{RR0}<0$, implying potential theoretical instabilities. And, for the Starobinsky model, while EM-only constraints are nearly symmetric between the two parameter branches ($b<0$ and $b>0$), the inclusion of SS constraints introduces mild asymmetries, revealing the sensitivity of SS observables to the
curvature dependence of the theory. Future truly independent standard siren observations would be crucial for a definitive assessment of $f(R)$
gravity as an alternative to $\Lambda$CDM.
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All authors Yi Zhang, Xuanjun Niu, Xianfu Su, Dong-Ze He
Cosmology and Nongalactic Astrophysics
Separation of polarized dust emission in Planck observations with Scattering Transforms
Alexandros Tsouros, Elisa Russier, Erwan Allys et al. (+3 more)
Polarized
dust emission is a major astrophysical foreground contaminant of the
cosmic microwave background polarization (CMB), which must be accurately measured to look for the faint
primordial polarization B-modes of inflationary origin. The available maps to date, obtained from Planck space mission data, are noise-dominated in the high
Galactic latitude regions that are most relevant for CMB observations. The goal of this work is to obtain better
dust polarization maps from Planck observations, by exploiting both the dependence between polarization and total intensity, as well as the non-Gaussian filamentary structure of the
dust emission. To this end, we use scattering transforms, which provide a stable and interpretable representation of complex non-Gaussian textures, allowing for a data-driven analysis approach requiring no explicit priors on
dust. The analysis is performed locally on Cartesian patches of sky, where Stokes linear polarization parameters, redefined in a local reference frame, are modeled as the sum of a signal of interest and a nuisance term. Using multiple realizations of the random nuisance term, we recover the polarized
dust maps by minimizing a composite objective function that enforces multiple statistical constraints in scattering space. The proposed
algorithm reconstructs maps of polarized
dust emission whose statistics are consistent with those expected from the Planck data once random nuisance realizations are added. This is confirmed in a validation test using a high signal-to-noise sky region as a test case. Comparisons with existing
dust polarization maps and models show that our approach better recovers small-scale polarized
dust emission, and that our reconstructed power and cross-spectra closely match those of the
dust polarization maps. A second set of maps that deterministically reproduce the features of the
dust polarized emission is also produced.
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All authors Alexandros Tsouros, Elisa Russier, Erwan Allys, Constant Auclair, François Boulanger, Jacques Delabrouille
High Energy Astrophysical Phenomena
Emergence of cyclic flux eruptions in kinetic simulations of magnetized spherical accretion onto a Schwarzschild black hole
Enzo Figueiredo, John Mehlhaff, Adrien Soudais et al. (+1 more)
The dynamics of black hole magnetospheres critically depend on the black hole
spin and on the structure of the
accretion flow. In the limit of a Schwarzschild black hole immersed in a zero-net angular momentum flow,
accretion is spherical. However, in the presence of a large-scale vertical
magnetic field, the classical Bondi
accretion model is significantly altered. The frozen-in field is stretched radially as the
plasma is pulled inward by
gravity. This continues until the restoring force from the
magnetic tension suddenly expels the material and resets the field, allowing a new cycle to begin. Although this scenario has been well depicted in previous studies, it remains incomplete as the issues of dissipation and particle acceleration are not yet fully resolved. In this work, we aim to revisit these issues with a first-principles kinetic
plasma model. We perform two-dimensional global general relativistic particle-in-
cell simulations of magnetized spherical
accretion onto a Schwarzschild black hole, for both pair and electron-ion
plasmas. The simulations are evolved over long timescales to capture multiple flux eruption events and establish a quasi-steady state. For each
accretion cycle, we find that the system goes through three main stages: (i) an ideal advection phase where
magnetic flux through the horizon increases quasi-linearly with time; (ii) a reconnection-regulated phase where the net increase of the flux is slowed down by intermittent reconnection events near the horizon; and (iii) a flaring phase when a major, large-scale reconnection event expels the flux, leading to efficient particle acceleration. The emergence of large-amplitude quasi-periodic flux eruptions and concomitant particle acceleration is reminiscent of Sgr A* flaring activity. This phenomenon could also be applicable to quiescent black holes, especially isolated black holes accreting the interstellar medium.
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All authors Enzo Figueiredo, John Mehlhaff, Adrien Soudais, Benoît Cerutti
Cosmology and Nongalactic Astrophysics
Weak Lensing Low Multipoles
Albert Bonnefous and Roya Mohayaee
We analyse the low–multipole components of the weak-
lensing convergence field in a FLRW universe. The low–multipole convergence field, encodes the largest-angle coherent potential gradients, essential for assessment of large-angle features in data. To study this large angle signal, we perform a combined analytical, numerical and observational study. Starting from exact analytical expressions for the convergence power spectrum, we quantify how the dipole, quadrupole and octupole build up with source
redshift and show that, in $\Lambda$CDM, they saturate at an amplitude of order $10^{-4}$. We then use full-sky, horizon-scale $N$-body simulations (Quijote) to explore the dependence of this signal on the observer's environment, comparing random observers to “Milky Way–like” observers. In parallel, we reconstruct the convergence field due to our local Universe with the 2MASS
Redshift Survey (2MRS), with proper treatment of incompleteness and
galaxy bias. We find that the observed low multipoles from observation is above the $\Lambda$CDM mean predictions, but in full agreement with Milky Way–like observers in the simulation. Finally, by converting the convergence dipole into a number-count dipole, we test whether weak
lensing can contribute to the
cosmic dipole anomaly, an idea motivated by its natural
alignment with the CMB dipole and by the fact that
lensing, unlike clustering, cannot be removed by cross-matching surveys and thus survives in all high-
redshift catalogues. We show that weak
lensing by local structure contributes at most a few percent to this observed anomaly.
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