Earth and Planetary Astrophysics
Physical and Chemical Characterization of GY 91's Multi-ringed Protostellar Disk with ALMA
Sally D. Jiang, Jane Huang, Ian Czekala et al. (+14 more)
GY 91, commonly categorized as a Class I young
stellar object, is notable for disk
dust substructures that have been hypothesized to trace early
planet formation. Using the ALMA 12-m and ACA arrays, we present new Band 7
dust continuum and molecular line observations of GY 91 at an angular resolution of (~40 au). We report detections of CS $J=6-5$, N$_2$H$^+$ $J=3-2$, C$^{18}$O $J=3-2$, H$_2$CS $J_{K_a, K_c} = 8_{1,7}-7_{1,6}$, H$_2$CO $J_{K_a, K_c} = 4_{0,4}-3_{0,3}$, and H$_2$CO $J_{K_a, K_c} = 4_{2,3}-3_{2,2}$, as well as a tentative detection of $^{13}$C$^{18}$O $J=3-2$. We observe azimuthal asymmetry in CS and H$_2$CS emission, as well as radially structured H$_2$CO $4_{0,4}-3_{0,3}$ emission outside the
dust continuum. C$^{18}$O and H$_2$CO 4$_{0,4}-3_{0,3}$ show significant cloud contamination, while CS and N$_2$H$^+$ are good tracers of Keplerian rotation originating from the disk. Envelope emission does not appear to contribute significantly either to the continuum or molecular line observations. GY 91's chemical properties appear in large part to resemble those of Class II disks, although observations of additional molecular probes should be obtained for a fuller comparison. With CS, we estimated a dynamical
stellar mass of 0.58 $M_\odot$, which is higher than previous estimates from
stellar evolutionary models (0.25 $M_\odot$). Using both radiative transfer modeling of the
dust continuum and comparison of the C$^{18}$O and N$_2$H$^+$ fluxes to literature thermochemical models, we estimate a disk mass of $\sim0.01$ $M_\odot$.
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All authors Sally D. Jiang, Jane Huang, Ian Czekala, Leon Trapman, Yuri Aikawa, Sean M. Andrews, Jaehan Bae, Edwin A. Bergin, Charles J. Law, Romane Le Gal, Feng Long, François Ménard, Karin I. Öberg, Chunhua Qi, Richard Teague, David Wilner, Ke Zhang
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Single-wave solutions of the neutrino fast flavor system. Part II. Weak instabilities and their resonant behavior
Damiano F. G. Fiorillo and Georg G. Raffelt
Flavor instabilities in dense
neutrino media trigger exponential growth of
flavor waves, yet their nonlinear saturation remains poorly understood. We examine a simple proxy for this effect in the form of a single-wave solution of an axially symmetric fast
flavor system. When the angular crossing is shallow and the growth rate of the instability correspondingly small, the
flavor wave primarily affects resonant
neutrinos that move in phase with it. The
evolution of these resonant
neutrinos becomes periodic, undergoing cycles of full
flavor reversal. They feed power into the unstable wave, and subsequently return to their initial state, draining power back out. This new
flavor pendulum captures the dynamics of weak, nearly monochromatic fast
flavor instabilities. Since weakly unstable distributions always exhibit a narrow range of unstable wavenumbers, our model likely describes the earliest development of a
flavor instability when it first appears. When the instability is not weak, the linear phase of a single-wave excitation does not connect to a regular nonlinear solution, unless the angle distribution consists of only two beams.
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Solar and Stellar Astrophysics
Homogenous abundances of Mg, Si, Ca, and Ti for about 1500 red giants in 16 globular clusters from FLAMES spectra
Eugenio Carretta
The FLAMES survey “Na-O anti-correlation and HB" uncovered the modern standard for globular clusters (GCs), that is their ubiquitous multiple
stellar populations (MPs) distinct by the abundance of
proton-capture elements. That survey can still be mined to extract a wealth of data. We derive new abundances of Mg, Si, Ca, and Ti for 948, 954, 1542, and 1350 red
giant branch
stars in 16 GCs, both formed in situ or accreted in the Milky Way. The program GCs cover the
metallicity range from [Fe/H]=-2.35 dex to [Fe/H]=-0.74 dex. Both the
halo and disc GCs show a clear overabundance of alpha-elements with the modulation in Mg and Si due to the MPs phenomenon in different clusters. We found
star to
star variations in Si abundance correlated to changes in Na in more than half of our sample, implying that temperatures in excess of about 65 MK were achieved in the polluters responsible for the enrichment. We confirm with an enlarged sample the previous result that significant variations in Mg are observed in GCs that are metal-poor, massive or both. Evidence of excess of Ca with respect to reference unpolluted field
stars are found in NGC 6752 and NGC 7078, indicating the action of
proton-capture reactions at very high temperature regime in these GCs. These excesses fit very well in a previously found relation as a function of a combination of cluster mass and
metallicity shown by other typical signatures of MPs. At odds with previous results based on the Si abundance from APOGEE, we found that the average abundance of alpha-elements is not an efficient discriminating factor between in situ and accreted GCs.
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Earth and Planetary Astrophysics
Evidence for a Peak at $\sim$0.3 in the Eccentricity Distribution of Typical Super-Jovian Exoplanets
Sarah Blunt, Jason Wang, Ruth Murray-Clay et al. (+3 more)
In this study, we compute completeness-corrected occurrence rates of
giant exoplanets as a function of mass, semimajor axis, and eccentricity, using the approximately uniform California Legacy Survey sample of RV-discovered
planets published in Rosenthal et al. 2021. We recover the previously-detected rise in occurrence with semimajor axis for both lower- and higher-mass subsets of the population out to $\sim$5 au. When restricting to
planets with semimajor axes between 0.1 and 4.5 au (roughly speaking, the "peak" of
giant planet occurrence), we find evidence for distinct eccentricity distributions for each of two mass sub-populations. Most strikingly, we observe a peak in the eccentricity distribution of super-Jovian
planets (3-20~M$_{\rm J}$) at 0.3, which is apparent using two different parameterizations of the eccentricity distribution model. A hierarchical histogram model reveals that $\sim$92% of posterior samples indicate an elevated occurrence rate of super-Jupiters with modest eccentricities (0.2-0.4) compared to lower or higher eccentricities (i.e. evidence for a moderate eccentricity "peak"), and 99% of samples indicate super-Jupiters with modest eccentricities are more common than those with lower eccentricities (i.e. evidence that moderate eccentricities are more common than low eccentricities). We use a truncated Gaussian model fit to pinpoint the location of the super-Jupiter eccentricity peak with more precision, finding a maximum a posterior (MAP) peak location of $e=0.3$. This low but elevated characteristic eccentricity could be the result of dynamically hot histories, perhaps involving a
giant impacts phase. All analysis code for this project is publicly available on Zenodo (https://zenodo.org/records/18089157) and GitHub (github.com/sblunt/eccentricities).
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All authors Sarah Blunt, Jason Wang, Ruth Murray-Clay, Bruce Macintosh, Ryan A. Rubenzahl, B.J. Fulton
Astrophysics of Galaxies
The Milky Way's circular velocity curve measured using element abundance gradients
Danny Horta, Adrian M. Price-Whelan, Sergey E. Koposov et al. (+4 more)
Spectroscopic surveys now supply precise
stellar label measurements such as element abundances for large samples of
stars throughout the Milky Way. These element abundances are known to correlate with orbital actions or other dynamical invariants. We present a new data-driven method for empirically measuring the circular velocity curve of the
Galaxy that uses element abundance gradients in the plane of radial kinematics. We use
stellar surface abundances from the $\textit{APOGEE}$ survey combined with kinematic data from the $\textit{Gaia}$ mission. Our results confirm the ordered structure of the Milky Way disk in terms of average [Fe/H] and [Mg/Fe] abundance ratios, and suggest that $\langle$[Fe/H]$\rangle$ traces the radial position of
stars in the disk, while $\langle$[Mg/Fe]$\rangle$ traces the orbital excursions around this radius. Our method uses the radial orbit structure in the
Galaxy to enable an empirical measurement of the circular velocity curve, epicyclic and azimuthal frequencies, and kinematic gradients across the Milky Way disk. From these measurements, we infer a value of the circular velocity curve at the
Solar radius of $v_{c,\odot} = 235.3^{+2.8}_{-3.7}$ km s$^{-1}$ using the most constraining abundance ratio, [Mg/Fe]. We also measure the radial and azimuthal frequencies for a circular orbit at the
solar radius, $\kappa_{0,R_\odot}=36.9^{+0.8}_{-1.0}$ km s$^{-1}$ kpc$^{-1}$ and $\Omega_{0,R_\odot}=28.5_{-0.1}^{+0.4}$ km s$^{-1}$ kpc$^{-1}$, respectively. These values lead to an estimate of the Oort constants of $A = 16.5^{+0.1}_{-0.1}$ km s$^{-1}$ kpc$^{-1}$ and $B=-11.9^{+0.1}_{-0.3}$ km s$^{-1}$ kpc$^{-1}$. We measure the radial acceleration at the
Solar radius to be $(\frac{\partial \Phi}{\partial R})_{\odot} = a_{R_\odot}=7.0^{+0.2}_{-0.1}$ pc Myr$^{-2}$.
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All authors Danny Horta, Adrian M. Price-Whelan, Sergey E. Koposov, Jason A. S. Hunt, David W. Hogg, Carrie Filion, Kathryn J. Daniel
Astrophysics of Galaxies
Zoe A. Le Conte, Dimitri A. Gadotti, Thomas Harvey et al. (+7 more)
Recent studies have revealed that bars can form as early as a few billion years after the Big Bang, already displaying characteristics similar to those of evolved bars in the Local Universe. Bars redistribute angular momentum throughout the
galaxy, regulating
star formation, AGN activity, and the formation of new
stellar structures such as
nuclear discs. However, the effects of bar-driven
evolution on young
galaxies are not yet known, as no evidence of bar-built
stellar structures has ever been found beyond $z = 1$, until now. In this work, we present evidence for a bar-built,
star-forming
nuclear disc already present at
redshift $z = 1.5$. This is the first evidence of a bar-built
stellar structure at
Cosmic Noon. We find that this
nuclear disc is actively forming
stars and is of similar size to some
nuclear discs in nearby
galaxies. This evidence solidifies the now emerging picture in which bars are fundamental not only in the late
evolution of
galaxies, but also in their early evolutionary stages. It changes the current paradigm by urging a revision of our picture of
galaxy evolution beyond
redshift one to include new considerations of the role of bars as early as a few billion years after the Big Bang.
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All authors Zoe A. Le Conte, Dimitri A. Gadotti, Thomas Harvey, Leonardo Ferreira, Christopher J. Conselice, Taehyun Kim, Camila de Sá-Freitas, Francesca Fragkoudi, Justus Neumann, E. Athanassoula
Earth and Planetary Astrophysics
Uniform Forward-Modeling Analysis of Ultracool Dwarfs. IV. Benchmarking the Sonora Diamondback and Saumon & Marley (2008) Atmospheric Models Across Late-M, L, and T types with Low-Resolution 0.8-2.5 $\mu$m Spectroscopy
Emily Mader, Zhoujian Zhang, Jonathan J. Fortney et al. (+6 more)
(Abridged) We present a systematic assessment of two major cloudy atmospheric model grids – SM08 (Saumon & Marley 2008) and Sonora Diamondback – when applied to low-resolution near-infrared (0.8-2.5 $\mu$m) spectroscopy. Our analysis focuses on a uniform sample of 142 age-
benchmark brown
dwarfs and planetary-mass objects spanning late-M, L, and T spectral types, with independently determined ages from 10 Myr to 10 Gyr. We perform forward-model spectral fitting for all
benchmarks' IRTF/SpeX spectra ($R\sim$80-250) using both SM08 and Sonora Diamondback atmospheric models to infer effective temperatures, surface gravities,
metallicities, radii, and cloud sedimentation efficiencies. The two model grids yield broadly consistent results. Among L4-L9
dwarfs, we identify a statistically significant, population-level age dependence of the cloud parameter $f_{\rm sed}$, with young
benchmarks ($<300$ Myr) exhibiting systematically lower $f_{\rm sed}$ values than older counterparts. This trend is absent across L0-T5 and T0-T5, demonstrating that cloud properties vary with age and surface
gravity and offering explanations for the observed
gravity-dependent photometric properties at the late-L end of the L/T transition. By comparing spectroscopically inferred parameters with predictions from
evolution models, we quantify systematic errors in the fitted atmospheric parameters and establish empirical calibrations to anchor future studies using these atmospheric models. Stacked residuals of the sample reveal wavelength-dependent data-model mismatches associated with key atomic and molecular absorption bands, highlighting the need for improved opacities and rainout chemistry. Finally, we show that including an interstellar-medium-like extinction term significantly improves the spectral fits, confirming and broadening previous findings and suggesting missing opacity sources in current cloudy models.
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All authors Emily Mader, Zhoujian Zhang, Jonathan J. Fortney, Caroline V. Morley, Malik Bossett, Mark S. Marley, Sagnick Mukherjee, Brendan P. Bowler, Michael C. Liu
High Energy Astrophysical Phenomena
Induced Scattering of Fast Radio Bursts in Magnetar Magnetospheres
Rei Nishiura, Shoma F. Kamijima and Kunihito Ioka
We investigate induced Compton/Brillouin scattering of electromagnetic waves in magnetized electron and positron pair
plasma by verifying kinetic theory with Particle-in-
Cell simulations. Applying this to fast
radio bursts (FRBs) in magnetar magnetospheres, we find that the scattering–although suppressed by the
magnetic field–inevitably enters the linear growth stage before the incident wave amplitude becomes comparable to the background
magnetic field during its outward propagation through the magnetosphere. The subsequent
evolution bifurcates: full scattering occurs when the density exceeds a critical value, whereas below it the scattering saturates and the FRB can escape without substantial induced-scattering attenuation. This nonlinear saturation eases the tension with observations of compact emission regions and may explain the observed diversity, including the presence or absence of FRBs associated with X-ray bursts.
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Astrophysics of Galaxies
Inside the cocoon: a comprehensive explanation of the spectra of Little Red Dots
A. Sneppen, D. Watson, J. H. Matthews et al. (+10 more)
The James Webb Space
Telescope (JWST) has revealed a new population of compact
galaxies, the `little red dots' (LRDs), whose nature remains unclear. We assemble grating spectra for 53 LRD-like objects and use self-consistent radiative-transfer calculations to show that a supermassive black hole embedded in a dense gas cocoon reproduces the spectra in detail, without requiring a
stellar-like photosphere. The near-symmetric, electron-scattering-broadened emission line-shapes can be reproduced by cocoons with comparable inflowing and outflowing mass-fluxes. The same cocoon structure also simultaneously accounts for the continuum shapes, H and He line equivalent widths, and absorption features, and predicts metal-line absorption, X-ray weakness, and muted variability. We predict correlations should exist between Balmer break strength, Balmer line absorption, and scattering line width, and confirm their presence in the observed sample. Typical LRDs have black holes of order $10^{6}$ $\mathrm{M}_\odot$ inside ionised cocoons of tens of $\mathrm{M}_\odot$, likely fed by a much larger cold-gas reservoir.
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All authors A. Sneppen, D. Watson, J. H. Matthews, G. Nikopoulos, N. Allen, G. Brammer, R. Damgaard, K. E. Heintz, C. Knigge, K. S. Long, V. Rusakov, S. A. Sim, J. Witstok
Cosmology and Nongalactic Astrophysics
Redshift-space 21-cm bispectrum multipoles as an SKA-era gravity test in the post-reionization Universe
Sourav Pal and Debanjan Sarkar
The redshifted 21-cm line from neutral hydrogen ($\textrm{H}\textsc{i}$) enables volumetric intensity mapping of large-scale structure in the post-reionization Universe. In anticipation of SKA-MID's wide
redshift coverage and high signal-to-noise clustering measurements, we study the
redshift-space 21-cm bispectrum and its spherical-harmonic multipoles as probes of anisotropic non-linear structure formation and departures from General Relativity. Using a tree-level perturbative description for the 21-cm brightness-temperature field in
redshift space, and adopting the Hu–Sawicki $f(R)$ model as a representative modified-
gravity scenario, we forecast the detectability of configuration-dependent signatures with an SKA-MID–like survey. We derive the bispectrum-multipole covariance including sample variance and thermal noise and evaluate the expected signal-to-noise of deviations relative to $\Lambda$CDM. We find that the observable information is dominated by the lowest multipoles, while higher-order modes are strongly suppressed. This concentration in the lowest multipoles is well matched to SKA-MID sensitivity and to the quasi-linear modes that are expected to remain accessible in practice. The strongest modified-
gravity sensitivity arises from squeezed and stretched triangle configurations on quasi-linear scales, where scale-dependent growth enhances the bispectrum relative to the total variance. Our results position 21-cm bispectrum multipoles as a practical, SKA-ready observable for testing
gravity beyond $\Lambda$CDM in the post-reionization epoch.
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High Energy Astrophysical Phenomena
Energetic Ceilings and Benchmarks of Astrophysical Gravitational-Wave Backgrounds
Chiara M. F. Mingarelli
Every astrophysical gravitational-wave background (GWB) is limited by the rest mass its sources can convert into gravitational radiation. We combine available source mass, merger factor, radiative efficiency, and merger epochs for six populations: supermassive black hole binaries (SMBHBs), extreme-mass-ratio inspirals (EMRIs), IMBHs inspiralling into SMBHs,
stellar mass binary black holes (sBBHs), binary
neutron stars (BNSs), and Pop~III binary black holes. For each, we calculate a GWB
benchmark and an upper limit. For SMBHBs, the local mass census of Liepold & Ma (2024), together with the repeated-merger boost of Sato-Polito et al. (2024), allows us to compute a ceiling on the nanoHertz GWB. Anchoring the GWB to this census, and assuming one merger per SMBH, gives a
benchmark of $A_{\rm bench} = 2.11^{+0.43}_{-0.32}\times10^{-15}$ at $f=1\,{\rm yr}^{-1}$. For the ceiling, we assume an infinite number of previous mergers, yielding $A_{\rm ceil}=3.76^{+0.76}_{-0.56}\times10^{-15}$, consistent with published PTA amplitudes. Under this mass function and merger model, the measured GWB amplitude therefore does not require additional SMBH mass. A measured GWB can instead constrain its source population. Using the revised NANOGrav 15-yr GWB amplitude and this SMBH census gives $f_{\rm merge}=1.11^{+1.35}_{-0.63}$, where 1 means one merger per present-day remnant. For the other five populations, comparable censuses do not yet exist, so we report upper limits from the best available source constraints, including compact-binary merger rates. Finally, the six adopted upper limit cases yield a present-day gravitational-wave energy budget of $\rho_{\rm gw}^{(6)}=3.33^{+1.32}_{-0.83}\times10^{-7}\rho_c$. A larger energy density would require more source mass, mergers, radiative efficiency, or later epochs, or point to additional source populations or new physics.
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Instrumentation and Methods for Astrophysics
Towards a Comprehensive Understanding of Planetary Systems through Population-Level, Large-Scale Surveys
Francisco J. Pozuelos, Pedro J. Amado, Jesús Aceituno et al. (+13 more)
Over the past three decades,
exoplanet research has delivered an extensive census of
planets spanning a wide range of masses, sizes, and orbital configurations. Despite this progress, the physical interpretation of these populations remains severely limited, as precise constraints on planetary masses, interior structures, and atmospheres are available only for a small, highly selected subset of targets. As a result, most known
exoplanets remain physically ambiguous, preventing the construction of robust population-level trends and limiting our understanding of
planet formation,
evolution, and habitability. In the coming decades, missions such as PLATO, Earth 2.0, and the Nancy Grace Roman Space
Telescope will dramatically expand the number of
exoplanets detected. However, without a corresponding capability to characterise planetary masses and atmospheres at scale, these discoveries will remain largely detection-driven. Current and planned facilities, including JWST and ELT-class instruments, excel at detailed studies of individual systems but are intrinsically unsuited for large, homogeneous surveys. This white paper identifies population-level physical characterisation as a fundamental science challenge for the 2040s and motivates the need for a new observational paradigm. We outline how photonics-enabled, modular
telescope architectures can deliver the survey speed, stability, and scalability required to jointly probe planetary interiors and atmospheres across statistically meaningful samples, thereby enabling a comprehensive and physically grounded understanding of planetary systems.
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All authors Francisco J. Pozuelos, Pedro J. Amado, Jesús Aceituno, Marina Centenera-Merino, Stefan Cikota, Javier Flores, Julius Göhring, Sergio León-Saval, Kalaga Madhav, Giuseppe Morello, Abani Nayak, Jose L. Ortiz, David Pérez-Medialdea, María Isabel Ruiz-López, Miguel A. Sánchez-Carrasco, Alejandro Sánchez-López
Cosmology and Nongalactic Astrophysics
A Novel Lensed Point Source Modeling Pipeline using GIGA-Lens with Application to SN Zwicky and SN iPTF16geu
Saul Baltasar, Nicolas Ratier-Werbin, Xiaosheng Huang et al. (+5 more)
We introduce a novel modeling pipeline for strongly lensed point sources, using the GIGA-Lens framework, running on four A100 GPUs via the JAX platform. Using simulations, we demonstrate accurate and precise recovery of image positions, fluxes, and time delays, together with inference of complex lens mass distributions – including the mass density slope, $\gamma$ – from images of lensed point sources alone. We further show that we can achieve statistical uncertainty of $\sim 3.6\%$ ($\sim 2.5\, \mathrm{km\, s^{-1}/Mpc}$) on $H_0$ from a single system, with full forward modeling, i.e., simultaneous inference of all lens model parameters together with $H_0$. We apply our pipeline to two well-studied lensed SNe Ia, Zwicky and iPTF16geu. For SN iPTF16geu, unlike previous modeling efforts, we model only the images of the lensed point source (the SN) and do not use the lensed images of the extended host-
galaxy. Nevertheless, we are able to infer all of the mass parameters modeled in earlier studies, and our best-fit values, including $\gamma$, are fully consistent with published results. In the case of SN Zwicky, taking the same approach, however, we obtain an alternative best-fit model compared to published results, underscoring the importance of fully exploring the model parameter space.
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All authors Saul Baltasar, Nicolas Ratier-Werbin, Xiaosheng Huang, W. Sheu, C. J. Storfer, Y.-M. Hsu, Sean Xu, David J. Schlegel
Cosmology and Nongalactic Astrophysics
Baryonification III: An accurate analytical model for the dispersion measure probability density function of fast radio bursts
MohammadReza Torkamani, Robert Reischke, Michael Kovač et al. (+6 more)
We develop an analytical framework to predict the one-point probability distribution function (PDF) of dispersion measures (DMs) for fast
radio bursts (FRBs) within the baryonification (BFC) model. BFC provides a computationally efficient alternative to expensive hydrodynamical simulations for modelling baryonic effects on cosmological scales. By applying the
halo mass function and
halo bias, we convolve contributions from individual
halos across a range of masses and
redshifts to derive the large-scale structure contribution to the DM PDF. We validate our analytical predictions against consistency-check simulations and compare them with the IllustrisTNG hydrodynamical simulation over the
redshift range $ z = 0$ to $z = 5$, demonstrating excellent agreement. We demonstrate that our model produces consistent results when fitting gas profiles and predicting the PDF, and vice versa. We show that the BFC parameters controlling the gas profile, particularly the
halo mass scale ($M_\mathrm{c}$), mass-dependent slope ($\mu$), and outer truncation ($\delta$), are the primary drivers of the PDF shape. Additionally, we investigate the validity of the log-normal approximation commonly used for DM distributions, finding that it provides a sufficient description for a few hundred FRBs. Our work provides a self-consistent model that links gas density profiles to integrated DM statistics, enabling future constraints on baryonic feedback processes from FRB observations.
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All authors MohammadReza Torkamani, Robert Reischke, Michael Kovač, Andrina Nicola, Jozef Bucko, Alexandre Refregier, Sambit K. Giri, Aurel Schneider, Steffen Hagstotz
Earth and Planetary Astrophysics
Col-OSSOS: Investigating the Origins of Different Surfaces in the Primordial Kuiper Belt
Laura E. Buchanan, Megan E. Schwamb, Wesley C. Fraser et al. (+12 more)
The Colours of the Outer
Solar System Origins Survey (Col-OSSOS) measured the optical/NIR colours of a brightness-complete sample of Trans-Neptunian Objects (TNOs). Like previous surveys, this one found a bimodal colour distribution in TNOs, categorised as red and very red. Additionally, this survey proposed an alternative surface classification scheme: FaintIR and BrightIR. Cold classical TNOs mostly have very red or FaintIR surfaces, while dynamically excited TNOs show a mixture of surfaces. This likely indicates that formation locations and proximity to the Sun influenced surface characteristics and color changes. Our study combines the data from Col-OSSOS with two dynamical models describing the formation of the Kuiper belt during Neptune's migration. We investigate the proposed surface-colour changing line and explore the distribution of different surfaces within the
primordial disk. By comparing radial colour transitions across various scenarios, we explore the origins of surface characteristics and their implications within the context of BrightIR and FaintIR classifications. Moreover, we extend our analysis to examine the distribution of these surface classes within the present-day Kuiper Belt, providing insights into the configuration of the early
solar system's planetesimal disk prior to
giant planet migration. We find that the most likely
primordial disk compositions are inner neutral / outer red (with transition $30.0^{+1.1}_{-1.2}$ au), or inner BrightIR / outer FaintIR (with transition $31.5^{+1.1}_{-1.2}$ au).
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All authors Laura E. Buchanan, Megan E. Schwamb, Wesley C. Fraser, Michele T. Bannister, J. J. Kavelaars, Michaël Marsset, Rosemary E. Pike, David Nesvorný, Samantha M. Lawler, Susan D. Benecchi, Nuno Peixinho, Nicole J. Tan, Kathryn Volk, Mike Alexandersen, Jean-Marc Petit
Earth and Planetary Astrophysics
The Role of Intrinsic Temperature and Vertical Mixing in Characterizing Sub-Neptune Atmospheres
Neha Dushyantha Kumar, Jessica E. Libby-Roberts, Caleb I. Canas et al. (+3 more)
Sub-Neptune
planets are often modeled with a dense rocky or metal-rich interior beneath a thick hydrogen/helium (H/He) atmosphere; though their bulk densities could also be explained by a water-rich interior with a thin H/He atmosphere. Atmospheric composition provides a key mechanism to break this degeneracy between competing interior models. However, the overall composition of sub-Neptunes inferred from spectra obtained with the James Webb Space
Telescope, remains debated in part due to differences in modeling assumptions. While previous studies explored parameter spaces such as
stellar spectra, atmospheric
metallicities, and carbon-to-oxygen ratios, they often assumed fixed intrinsic temperatures (Tint) and vertical eddy
diffusion coefficients (Kzz) - two critical, yet poorly constrained, drivers of atmospheric chemistry. To address this, we present a self-consistent grid of models that covers the full plausible range of Tint (60 - 450 K) and Kzz (10^{5} - 10^{12} cm^2/s) using the open-source PICASO and VULCAN packages to better characterize sub-Neptune atmospheres. Focusing on K2-18b analogs, we demonstrate that Tint and Kzz significantly impact CH4, CO2, CO, NH3 and HCN abundances, with H2O being largely unaffected. Our work demonstrates that comprehensive parameter space exploration of thermal and mixing parameters is essential for accurate interpretation of sub-Neptune spectra, and that single-parameter assumptions can lead to misclassification of planetary interiors. We provide a diagnostic framework using multi-molecule observations to distinguish between competing atmospheric models and advance robust characterization of sub-Neptunes.
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All authors Neha Dushyantha Kumar, Jessica E. Libby-Roberts, Caleb I. Canas, Nicholas F. Wogan, Suvrath Mahadevan, Sagnick Mukherjee
Astrophysics of Galaxies
Virgo Filaments VI: H$\alpha$ clumps in the filaments around the Virgo galaxy cluster
G. Nagaraj, P. Jablonka, R. A. Finn et al. (+9 more)
It is still not clear which environmental processes operate in filaments. Given the ubiquity of filaments and their importance in feeding clusters, a proper understanding of these mechanisms is crucial to a more complete picture of
galaxy evolution. To investigate them, we need large
galaxy samples with spatially resolved information. As part of this effort, we analyse resolved H$\alpha$ maps of 685
galaxies inside and outside the filaments around the Virgo cluster in addition to extensive measurements of integrated physical properties. We create a pipeline to decompose the H$\alpha$ images into individual clumps that trace
star forming regions. We find that the number and average size of clumps in a
galaxy are well-defined functions of distance and angular resolution. In particular, the power-law relation between the number of clumps and the distance of a
galaxy is consistent with a fractal structure of
star forming regions. We formulate an
algorithm to compare filament and non-filament
galaxies after removing observational differences. Although we do not have any conclusive evidence for a difference in clump size distributions between filament and non-filament
galaxies, we do find that filament
galaxies have slightly more peripheral clumps than their non-filament counterparts.
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All authors G. Nagaraj, P. Jablonka, R. A. Finn, Y. M. Bahé, F. Combes, G. Castignani, B. Vulcani, G. Rudnick, D. Zakharova, R. A. Koopmann, D. Zaritsky, K. Conger
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Impact of soft versus hard equations of state on hybrid stars
H. Güven, K. Bozkurt, E. Khan et al. (+1 more)
The
nuclear stiffness as a dominant contribution of
nuclear symmetry energy is analyzed on the properties of compact
stars considering constraints from
nuclear physics and astrophysics. A compact
star can be a
neutron star composed only of
nuclear matter or a hybrid
star with a
quark core. Two typical models (soft and stiff) are considered for the
nuclear equation of state, and for the hybrid one, a parameterized first-order phase transition approach, completed with a linear
quark matter equation of state, is implemented. We show that the phase transition reduces the tension between GW170817 and NICER observations, and we illustrate the impact of
nuclear stiffness for the understanding of the nature of the binary system in GW170817. The implication on
nuclear symmetry energy is also discussed. We also confirm our previous findings that the GW170817 waveform is best described as a binary HS with a low-density onset of stiff
quark matter. This could also be interpreted as a quarkyonic cross-over.
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All authors H. Güven, K. Bozkurt, E. Khan, J. Margueron
High Energy Astrophysical Phenomena
Explaining the thermal emission of old neutron stars with rotochemical heating and magnetized superconducting protons
Luis E. Rodríguez, Andreas Reisenegger, Denis González-Caniulef et al. (+1 more)
The detection of likely thermal ultraviolet emission from a few old
neutron stars suggests that at least one internal heating mechanism is present in these
stars. One proposed mechanism is rotochemical heating, in which the continuous contraction of the
neutron star due to its
spin-down produces chemical imbalances that induce Urca reactions, and the latter deposit heat in the
neutron star core. If the
protons in the
star are superconducting, their energy gap suppresses the reactions, except in microscopic magnetized regions (such as quantized flux tubes) in which the
protons act as if they were normal. Therefore, the strength of the internal
magnetic field controls the rate at which reactions proceed and thus affects the thermal
evolution of the
neutron star. Here, we present the first comprehensive study of the effect of an internal
magnetic field in the superconducting interior on rotochemical heating. We simulate the
evolution of
neutron stars for different internal
magnetic field strengths and
neutron energy gaps, comparing the results to Hubble Space
Telescope observations of old
neutron stars. All the observational data can be accounted for if the
proton energy gap is large ($\sim 1.5\,\mathrm{MeV}$) and the
neutron energy gap is small ($\lesssim 0.1\,\mathrm{MeV}$) or vanishing, while the millisecond
pulsar PSR~J0437$-$4715 needs to have a very weak internal
magnetic field. Our results suggest that
neutron-
star cores are characterized by a large
proton pairing gap and a small or vanishing
neutron gap, and that millisecond
pulsars have very weak internal
magnetic fields. Under these conditions, rotochemical heating alone can account for the observed thermal emission of old
neutron stars.
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All authors Luis E. Rodríguez, Andreas Reisenegger, Denis González-Caniulef, Cristóbal Petrovich
Cosmology and Nongalactic Astrophysics
Ultra-fast growth of primordial black holes through radiative absorption
Dimitris S. Kallifatides, Theodoros Papanikolaou and Emmanuel N. Saridakis
We show that Schwarzschild
primordial black holes (PBHs) formed in the radiation-dominated era can grow extremely rapidly through $\textit{radiative absorption}$ governed by the full Stefan-Boltzmann law. By introducing a principle of isonomy - ensuring identical particle species dependence for Hawking emission and absorption - we find that, whenever the temperature of the PBH environment is larger than the PBH horizon temperature, PBHs generically gain mass. In particular, for PBH masses following the critical collapse mass-scaling law with critical exponent $\gamma_\mathrm{crit}$, with $\gamma_\mathrm{crit} \in (0.33, 0.49)$, the aforementioned radiative absorption mass growth mechanism produces a striking effect: PBHs forming with a mass $10^6M_\odot$ during BBN can reach $\mathcal{O}(10^{10} M_\odot)$ within $\mathcal{O}(10^{6} \mathrm{s})$ ($\sim $ 58 days). Interestingly enough, small deviations from $\gamma_\mathrm{crit}$, depending itself on the number of relativistic species present in the
primordial plasma, yield a continuous PBH mass spectrum providing us ultimately with a single, Standard-Model-based explanation for the origin of
stellar-mass, intermediate-mass, and supermassive black holes (SMBHs), and naturally accounting for the early appearance of SMBHs. The Schwarzschild treatment presented here can be extended to spherically symmetric cosmological black holes, indicating that radiative absorption is a dominant and previously overlooked PBH growth channel in the early Universe.
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Astrophysics of Galaxies
Intracluster light as a dark matter tracer: how their spatial and kinematic relationship is shaped by satellite demographics
G Martin, F R Pearce, N A Hatch et al. (+6 more)
We investigate how the orbital
evolution and mass distribution of infalling satellite
galaxies shape the phase-space and radial distributions of intracluster light (ICL) relative to the underlying cluster dark matter (DM)
halo. Using N-body simulations, we follow the
tidal stripping and orbital
evolution of satellite
galaxies as they are accreted into a live cluster
halo, systematically varying satellite-to-host mass ratio and orbital circularity. We measure the specific orbital energy and angular momentum of stripped
stellar and DM material, finding that the stripped
stars consistently occupy lower-energy and lower-angular momentum regions of phase-space than the stripped DM. The magnitude of this difference increases strongly towards more equal satellite–to–host mass ratios, while the dependence on orbital circularity is weak. We construct a predictive model for the phase-space properties of stripped
stars and DM from a whole infalling satellite population and find that the resulting phase-space difference between the components are driven primarily by the characteristic mass of the infalling satellite
stellar mass function. We find that the ICL is always more centrally concentrated than the DM. The magnitude of this offset depends on the characteristic mass and increases towards higher characteristic masses. Comparisons with four independent cosmological hydrodynamical simulations show that, once the infalling satellite
stellar mass function is matched, the model reproduces the radial
stellar-to-DM density profile offsets to better than the inter-simulation scatter. This demonstrates that the radial relationship between the ICL and the DM distribution is largely governed by satellite demographics. With adequate constraints on the infalling satellite population, ICL density profiles can therefore be used as informative tracers of the underlying radial DM distribution in clusters.
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All authors G Martin, F R Pearce, N A Hatch, H J Brown, M Butler, Y M Bahe, W Cui, Y Dubois, A Knebe
Instrumentation and Methods for Astrophysics · Cross-listed from stat.ME
Learned harmonic mean estimation of the marginal likelihood for multimodal posteriors with flow matching
Alicja Polanska and Jason D. McEwen
The marginal likelihood, or
Bayesian evidence, is a crucial quantity for
Bayesian model comparison but its computation can be challenging for complex models, even in parameters space of moderate dimension. The learned harmonic mean
estimator has been shown to provide accurate and robust estimates of the marginal likelihood simply using posterior samples. It is agnostic to the sampling strategy, meaning that the samples can be obtained using any method. This enables marginal likelihood calculation and model comparison with whatever sampling is most suitable for the task. However, the internal density
estimators considered previously for the learned harmonic mean can struggle with highly
multimodal posteriors. In this work we introduce flow matching-based continuous normalizing flows as a powerful architecture for the internal density estimation of the learned harmonic mean. We demonstrate the ability to handle challenging
multimodal posteriors, including an example in 20 parameter dimensions, showcasing the method's ability to handle complex posteriors without the need for fine-tuning or heuristic modifications to the base distribution.
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Astrophysics of Galaxies
New parameters for star cluster dynamics: observational results
Barbara Lanzoni, Francesco R. Ferraro and Enrico Vesperini
We recently used a large set of Monte Carlo simulations of globular clusters (GCs) to define new fully empirical parameters (named A5, P5, and S2.5) able to trace the internal dynamical
evolution of dense
stellar systems. These parameters are specifically designed to quantify the steepness of the cumulative radial distribution of
stars in the innermost region of the host system, which tends to progressively increase with dynamical aging due to core contraction. Following the original definitions, here we measure A5 and P5 in a sample of 40
Galactic GCs homogeneously surveyed through HST photometric observations. In agreement with the predictions of our simulations, the largest values of A5 and P5 are found for the most dynamically evolved GCs, i.e., those previously classified as post-core collapse systems based on the shape of their density profile, and those characterized by the shortest central relaxation times. Moreover, the new dynamical parameters here measured strongly correlate with A+rh, another fully empirical, independent parameter that traces the dynamical age of
star clusters through the level of central segregation of blue straggler
stars.
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Instrumentation and Methods for Astrophysics
tilepy: A Flexible Open-Source Scheduling Engine for Time-Domain and Multi-Messenger Astronomy
Fabian Schüssler, H. Ashkar, W. Kiendrébéogo et al. (+5 more)
The era of multi-messenger astrophysics requires rapid and efficient follow-up of transient events, many of which, such as gravitational waves (GW), gamma-ray bursts (GRB), and high-energy
neutrinos, suffer from poor sky localisation. We present tilepy, a Python-based software designed to optimize observation schedules for these events. We here detail the modular architecture of tilepy, which separates high-level scheduling logic from low-level tiling and pointing tools, enabling full adaptability for ground- and space-based observatories. Furthermore, we describe the integration of tilepy into the Astro-COLIBRI platform, providing the community with a user-friendly interface and API for triggering complex observation campaigns in real time.
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All authors Fabian Schüssler, H. Ashkar, W. Kiendrébéogo, M. Seglar-Arroyo, M. de Bony, A. Berti, E. Ruiz-Velasco, R. Le Montagner
Cosmology and Nongalactic Astrophysics
Impact of Rastall gravity on hydrostatic mass of galaxy clusters
M. Lawrence Pattersons, Feri Apryandi and Freddy P. Zen
Galaxy clusters are the largest virialized structures in the Universe and are predominantly dominated by dark matter. The hydrostatic mass and the mass obtained from gravitational
lensing measurements generally differ, a discrepancy known as the hydrostatic mass bias. In this work, we derive the hydrostatic mass of
galaxy clusters within the framework of Rastall
gravity. We consider two scenarios: (i) the absence of dark matter and (ii) the presence of dark matter. In both cases, we constrain the Rastall parameter in the cluster-scale using observational data. In the first scenario, Rastall
gravity effectively reduces the hydrostatic mass, bringing it closer to the observed baryonic mass. The best linear fit yields a slope $\mathbf{M}=1.07\pm0.11$, indicating a near one-to-one correspondence between the two masses. In the second scenario, Rastall
gravity helps to alleviate the hydrostatic mass bias. The linear fit between the Rastall hydrostatic mass and the observed
lensing mass results in a best-fit slope $\mathbf{M}=0.99\pm0.26$, which is very close to unity. We also calculate the goodness-of-fit for every fit. The statistical evaluations indicate that Rastall
gravity provides a viable phenomenological framework that can improve certain aspects of the mass discrepancy problem at the level of scaling relations. However, it does not universally outperform other modified
gravity model, when evaluated using standard goodness-of-fit criteria.
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High Energy Astrophysical Phenomena
Closure models for the feedback of energetic particles on plasma turbulence
J. Pratt
Energetic particles interact with the
plasma surrounding them, resonating with certain
plasma waves to stabilize them while destabilizing others, and changing the character of the background
turbulence in ways that have not been fully quantified or understood. Interaction with the turbulent background
plasma is key to the acceleration of many types of energetic particles including high-energy
cosmic rays,
solar energetic particles, and pick-up ions. This is a process that would ideally be described by a kinetic model, a type of model that follows a probability distribution function (PDF) for all particles in 7-dimensional space. Because of the high dimensionality of a kinetic model, such simulations use the largest computational resources available, and are yet unable to simulate a realistic number of particles, reach the large scales necessary for astrophysical problems, or use high-precision numerical methods. Two available alternatives to kinetic
plasma models have been explored: a multi-fluid model, and a hybrid fluid/Fokker-Planck model. These methods are hampered by the physical modeling of the coupling. We develop a new model, which follows the PDF for all particles; this can be viewed as a step toward physical realism above a multi-fluid MHD model, while also being more computationally efficient than a kinetic model. The equations we develop model both the background
plasma and the energetic particles self-consistently. Over the last decade, similar PDF methods have been developed to a high level of sophistication to model reactive flows and turbulent combustion for engineering applications. For treatment of the feedback of the energetic particles on a background
plasma, a PDF closure approach should evaluate the mean characteristics, including the density, with better statistical quality than will particle-sampling procedures.
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High Energy Astrophysical Phenomena
The growing family of gamma-ray narrow-line Seyfert 1 galaxies
Luigi Foschini
The revision of the fourth
Fermi Large Area
Telescope (LAT) catalog of gamma-ray point sources (rev4FGL) revealed that the gamma-ray sky is populated by emerging populations of jetted active
galactic nuclei (AGN) other than blazars and
radio galaxies. Narrow-Line Seyfert 1, Seyfert 1, intermediate, and Seyfert 2
galaxies, changing-look AGN, plus a number of ambiguous or unclassified sources. After a short historical introduction on the gamma-ray observations of Seyfert-type AGN, I explore the main statistical properties of 1477 jetted AGN from the rev4FGL with spectroscopic
redshift, and also the cross-match with Very Large Baseline Array (VLBA)
radio observations at 15~GHz from the Monitoring Of Jets in Active
galactic nuclei with VLBA Experiments (MOJAVE) program. I then discuss the difference between gamma and non-gamma jetted AGN, and the implications on the classification.
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Astrophysics of Galaxies
The ALMA-ATOMS survey: Methanol emission in a large sample of hot molecular cores
Jiahang Zou, Tie Liu, Sheng-Li Qin et al. (+26 more)
Methanol (CH$_{3}$OH) is a key complex organic molecule (COM) in the interstellar medium, widely used as a tracer of dense gas and hot molecular cores (HMCs). Using high-resolution ALMA observations from the ATOMS survey, we investigate the excitation and abundance of methanol
nuclear spin isomers and their relationship to chemical complexity in massive
star-forming cores. We identify 20 methanol transitions, including A- and E-type lines in the v=0 state and E-type lines in the v$_{t}$=1 state, and detect 94 HMC candidates. Rotational temperature analysis under the LTE assumption yields average values of 194 $\pm$ 33 K for CH$_{3}$OH-E v$_{t}$=1, 178 $\pm$ 33 K for CH$_{3}$OH-A v=0, and 75 $\pm$ 33K for CH$_{3}$OH-E v=0. Emission from COMs other than methanol is detected in 87 of the 94 cores, with the CH$_{3}$OH-E v$_{t}$=1 line intensity showing a strong correlation with the channel detection ratio (CDR). These results demonstrate that CH$_{3}$OH-E v$_{t}$=1 lines are reliable tracers of HMCs and chemical complexity, and that the CDR provides a robust indicator of molecular richness. The temperature difference between A- and E-type methanol transitions is driven by anomalously strong J(2,J-2)$-$J(-1,J-1) lines, highlighting the importance of analyzing methanol
symmetry types separately.
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All authors Jiahang Zou, Tie Liu, Sheng-Li Qin, Yaping Peng, Fengwei Xu, Xunchuan Liu, Li Chen, Xindi Tang, Sami Dib, Zi-Yang Li, Hong-Li Liu, Mika Juvela, Patricio Sanhueza, Pablo Garcia, Chang Won Lee, Guido Garay, Swagat R. Das, Yan-Kun Zhang, Kee-Tae Kim, Jeong-Eun Lee, Meizhu Liu, Leonardo Bronfman, Zihping Kou, Dongting Yang, Gang Wu, Jihye Hwang, Dezhao Meng, Mengyao Tang, James O. Chibueze
Cosmology and Nongalactic Astrophysics
Constraining reionization morphology and source properties with 21cm galaxy cross-correlation surveys
Yannic Pietschke, Anne Hutter and Caroline Heneka
Cross-correlations between 21cm observations and
galaxy surveys provide a powerful probe of reionization by providing robustness against foreground contamination while linking ionization morphology to
galaxies. We quantified the constraining power of 21cm
galaxy cross-power spectra for inferring the neutral hydrogen fraction, $x_\mathrm{HI}(z),$ and mean overdensity, $\langle 1+\delta_\mathrm{HI} \rangle(z)$, exploring dependence on the field of view;
redshift precision, $\sigma_z$; and minimum
halo mass, $M_\mathrm{h,min}$. We employed our simulation-based inference framework EoRFlow for likelihood-free parameter estimation. Mock observations include thermal noise for 100h of SKA-Low with foreground avoidance and realistic
galaxy-survey effects. For a fiducial survey ($\mathrm{FOV}=100\,\mathrm{deg}^2$, $\sigma_z=0.001$, $M_\mathrm{h,min}=10^{11}\mathrm{M}_\odot$), cross-power spectra yield unbiased constraints with posterior volumes (PVs) of $\sim$10% relative to priors. Cross-power measurements reduce the PV by 20-30% versus 21cm auto-power alone. With foreground avoidance, spectroscopic
redshift precision is essential; photometric
redshifts render cross-correlations uninformative. Notably, cross-power spectra constrain ionizing source properties, the escape fraction $f_\mathrm{esc,}$ and the
star formation efficiency $f_*$, which remain degenerate in auto-power (PV >60%). Tight constraints require either deep surveys detecting faint
galaxies ($M_\mathrm{h,min} \sim 10^{10}\mathrm{M}_\odot$) with moderate foregrounds (PV~11%) or conservative mass limits with optimistic foreground removal (PV~19%). 21cm
galaxy cross-correlations enhance morphology constraints beyond auto-power while enabling previously inaccessible source property constraints. Realizing full potential requires precise
redshifts and either faint
galaxy detection limits or improved 21cm foreground cleaning.
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High Energy Astrophysical Phenomena
Disk-jet-wind coupling from stellar mass to supermassive black holes
Chris Done
Black holes are the simplest possible objects, characterised by only mass and
spin. We see them via
accretion, so there is one more fundamental parameter which is the mass
accretion rate. Here I will review how the data from both
stellar and supermassive black holes can be fit into a framework where there is a major spectral transition at $\dot{m}=L/L_{\rm Edd}\sim 0.01$ where the optically thick disc is replaced by a hot flow. This dramatic spectral change also affects the expected properties of thermal and radiatively powered winds, matching the overall properties of winds seen in new XRISM data from the
stellar mass binaries, though there can also be additional UV and
dust driven winds in supermassive black holes. The
radio data in
stellar and supermassive black holes are clear that the hot flow (not the disc) connects to the
radio jet, and the
radio-X-ray 'fundamental plane' can be qualitatively understood if the
radio quiet AGN and
stellar mass black holes have low to moderate
spins, with the jet power set as a constant fraction of the
accretion power. A small fraction of AGN (
radio loud) instead have much higher (factor $100-1000\times$)
radio-to-X-ray ratio at the same black hole mass and mass
accretion rates. I speculate that these have higher jet power due to high black hole
spin. I review the multiple issues still remaining in this picture, most of which are connected to the geometry and nature of the X-ray corona, and the conflicting constraints on this which come from reflection spectroscopy and polarimetry.
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