High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Extreme-mass-ratio inspirals in relativistic accretion discs
Francisco Duque, Laura Sberna, Andrew Spiers et al. (+1 more)
We compute relativistic Lindblad torques for circular, equatorial extreme-mass-ratio inspirals (EMRIs) embedded in relativistic thin
accretion discs, including spinning black hole configurations. We find that relativistic effects can amplify the magnitude of these torques by orders of magnitude in the strong-field regime, and that the torque can even reverse direction as the EMRI approaches the innermost stable circular orbit (ISCO). However, we show that the location of this reversal is highly
spin-dependent, shifting progressively closer to the ISCO, where gravitational-wave emission completely dominates the inspiral, as the
spin of the central black hole increases.
Spin also modifies the radial dependence of the Lindblad torques. We investigate whether Lindblad torques can be approximated by parametrised power laws of the form T_LR = A(r_s / 10M)^n_r (or combinations thereof), and find significant
spin- and disc-dependent variations in the slope parameter n_r. For instance, for
spin a/M = 0.9, we find n_r = 3.6 in the strong-field regime, compared to the Newtonian value of n_r = 4.5. Given current forecasts of parameter recovery for “golden”, loud EMRIs in
accretion discs (\Delta n_r ~ 0.5), we predict LISA could distinguish between different disc configurations through their relativistic Lindblad torque signatures, providing the first direct probe of the midplane structure of the inner region of
accretion discs, which is inaccessible to electromagnetic observations.
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All authors Francisco Duque, Laura Sberna, Andrew Spiers, Rodrigo Vicente
Astrophysics of Galaxies
The Entangling of Supernova Feedback Impacts with Coarsening Simulation Resolution
Eric Zhang, Laura V. Sales, Thales A. Gutcke et al. (+11 more)
It is often understood that
supernova (SN) feedback in
galaxies is responsible for regulating
star formation (SF) and generating gaseous
outflows. However, a detailed look at the small-scale effects of SNe on the interstellar medium (ISM) in simulations shows that the macroscopic processes of SF suppression and
outflow generation proceed in distinct channels. We demonstrate this finding in two independent simulations of isolated
dwarf galaxies with very high (m_gas ~ Msun) numerical resolution, LYRA and RIGEL. Our findings suggest that the macroscopic effect of a given SN on the
galaxy is best predicted by its local density.
Outflows are primarily linked to SNe in diffuse regions expanding to their cooling radii on large (~kpc) scales, while dense SF regions are disrupted in a localized (~pc) manner. However, these separate feedback channels are only distinguishable at very high resolutions capable of following mass scales \lesssim 10^2 \msun. When averaging on coarser scales, ISM densities are greatly mis-estimated, and variations between different SF and SNe-affected regions are severely washed out. It therefore cannot be __self-consistently__ determined, from coarse-resolution information __alone__, (1) whether a SN tends to contribute to
outflows or direct SF suppression, and (2) the rate of SF in a given region. In particular, commonly used parameters in coarse-resolution (subgrid) models, such as the SN cooling radius and SF density threshold, may require more detailed treatments informed by high-resolution studies.
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All authors Eric Zhang, Laura V. Sales, Thales A. Gutcke, Yunwei Deng, Hui Li, Rüdiger Pakmor, Federico Marinacci, Volker Springel, Mark Vogelsberger, Paul Torrey, Boyuan Liu, Rahul Kannan, Aaron Smith, Greg L. Bryan
Astrophysics of Galaxies
No Observational Evidence for Dark Matter Nor a Large Metallicity Spread in the Extreme Milky Way Satellite Ursa Major III / UNIONS 1
William Cerny, Daisy Bissonette, Alexander P. Ji et al. (+9 more)
The extremely-low-luminosity, compact Milky Way satellite Ursa Major III / UNIONS 1 (UMaIII/U1; $L_V = 11 \ L_{\odot}$; $a_{1/2} = 3$ pc) was found to have a substantial velocity dispersion at the time of its discovery ($\sigma_v = 3.7^{+1.4}_{-1.0} \rm \ km \ s^{-1}$), suggesting that it might be an exceptional, highly dark-matter-dominated
dwarf galaxy with very few
stars. However, significant questions remained about the system's dark matter content and nature as a
dwarf galaxy due to the small member sample ($N=11$), possible spectroscopic binaries, and the lack of any
metallicity information. Here, we present new spectroscopic observations covering $N=16$ members that both dynamically and chemically test UMaIII/U1's true nature. From higher-precision Keck/DEIMOS spectra, we find a 95% confidence level velocity dispersion limit of $\sigma_v< 2.3 \rm \ km \ s^{-1}$, with a $\sim$120:1 likelihood ratio now favoring the expected
stellar-only dispersion of $\sigma_* \approx 0.1 \rm \ km \ s^{-1}$ over the original $3.7 \rm \ km \ s^{-1}$ dispersion. There is now no observational evidence for dark matter in the system. From Keck/LRIS spectra targeting the Calcium II K line, we also measure the first
metallicities for 12 member
stars, finding a mean
metallicity of $\rm [Fe/H] = -2.65 \; \pm \, 0.1$ (stat.) $\pm \,0.3$ (zeropoint) with a
metallicity dispersion limit of $\sigma_{\rm [Fe/H]} < 0.35$ dex (at the 95% credible level). Together, these properties are more consistent with UMaIII/U1 being a
star cluster, though the
dwarf galaxy scenario is not fully ruled out. Under this interpretation, UMaIII/U1 ranks among the faintest and most metal-poor
star clusters yet discovered.
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All authors William Cerny, Daisy Bissonette, Alexander P. Ji, Marla Geha, Anirudh Chiti, Simon E.T. Smith, Joshua D. Simon, Andrew B. Pace, Evan N. Kirby, Kim A. Venn, Ting S. Li, Alice M. Luna
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
ArgoLOOM: agentic AI for fundamental physics from quarks to cosmos
S. D. Bakshi, P. Barry, C. Bissolotti et al. (+12 more)
Progress in modern physics has been supported by a steadily expanding corpus of numerical analyses and computational frameworks, which in turn form the basis for precision calculations and baseline predictions in experimental programs. These tools play a central role in navigating a complex landscape of theoretical models and current and potential observables to identify and understand fundamental interactions in physics. In addition, efforts to search for new fundamental interactions increasingly have a cross-disciplinary nature, such that understanding and leveraging interoperabilities among computational tools may be a significant enhancement. This work presents a new agentic AI framework, which we call ArgoLOOM, designed to bridge methodologies and computational analyses across cosmology,
collider physics, and
nuclear science. We describe the system contours, key internal aspects, and outline its potential for unifying scientific discovery pipelines. In the process, we demonstrate the use of ArgoLOOM on two small-scale problems to illustrate its conceptual foundations and potential for extensibility into a steadily growing agentic framework for fundamental physics.
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All authors S. D. Bakshi, P. Barry, C. Bissolotti, I. Cloet, S. Corrodi, Z. Djurcic, S. Habib, K. Heitmann, T. J. Hobbs, W. Hopkins, S. Joosten, B. Kriesten, N. Ramachandra, A. Wells, M. Zurek
Cosmology and Nongalactic Astrophysics
A New Recipe for Caustic Pancakes: On the Reality of Walls in the Cosmic Web
Benjamin Hertzsch, Job Feldbrugge, Maé Rodriguez et al. (+1 more)
The caustic skeleton model is a mathematically rigorous framework for studying the formation history of the emerging
cosmic web from the caustics in the underlying dark matter flow. In a series of two papers, we use constrained N-body simulations to investigate the different
cosmic web environments. For the current study, we focus on the
cosmic walls. We derive the conditions of the centres of proto-walls and analyse their
evolution with N-body simulations. Next, we investigate the statistical properties of Zel'dovich pancakes by studying the number density of the
cosmic wall centres in scale space and, for the first time, we calculate the Lagrangian-space volume of
cosmic walls. Finally, we infer the mean density and velocity fields and the distribution of
haloes around
cosmic walls with a suite of physically realistic dark-matter-only simulations. We compare the
cosmic walls obtained with the caustic skeleton framework with previously proposed saddle point conditions on the
primordial potential and density perturbation.
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All authors Benjamin Hertzsch, Job Feldbrugge, Maé Rodriguez, Rien van de Weygaert
Astrophysics of Galaxies · Cross-listed from hep-ph
Astrophysical Consequences of an Electroweak $\eta_{\rm w}$ Pseudo-Scalar
Hooman Davoudiasl
Recently, it has been suggested that the spectrum of physical states in the Standard Model may include an ultralight pseudo-scalar, denoted by $\eta_{\rm w}$, in analogy with the $\eta'$ state arising from the strong interactions. We find that typical expectations for the properties of $\eta_{\rm w}$ get challenged by astrophysical constraints on the couplings of ultralight
bosons. Our strongest limit sets a lower bound of $\mathcal{O}({\rm 100~TeV})$ on the decay constant of the hypothesized pseudo-scalar. We also briefly discuss whether $\eta_{\rm w}$ could be a dark matter candidate, or the origin of dark energy, but conclude that those identifications appear unlikely. Given the important implications of a potentially overlooked $\eta_{\rm w}$ state for a more complete understanding of the electroweak interactions and a fundamental description of Nature, further theoretical and phenomenological investigations of this possibility and its associated physics are warranted.
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Astrophysics of Galaxies
ALMA Deep Field in SSA22: Reconstructed [CII] Luminosity Function at z = 6
Natsuki H. Hayatsu, Rob J. Ivison, Paola Andreani et al. (+19 more)
The ADF22 line survey reported detections of two high-$z$ line-emitting source candidates above 6-$\sigma$, both of which were shown to be spurious after follow-up observations. We investigate the detectability of far-infrared emitters in ALMA deep fields using mock observations by injecting artificial line-emitting sources into the visibility planes. We also discuss our investigation, conducted together with the ALMA operations team, of a possible technical problem in the original observations. Finally, we devise a method to estimate the [CII] luminosity function (LF) at $z \sim 6$, including a full analysis of signal contamination and sample completeness. The comparison of pixel distributions between the real and mock datacubes does not show significant differences, confirming that the effect of non-Gaussian noise is negligible for the ADF22 datacube. Using 100 blank mock-mosaic
datasets, we show 0.43 $\pm$ 0.67 false detections per datacube with the previous source-finding method. We argue that the underestimation of the contamination rate in the previous work is caused by the smaller number of datacubes, using only 4 real ADF22 datacubes. We compare the results of clump-finding between the time division mode and frequency division mode correlator datacubes and confirm that the velocity widths of the clumps in the TDM case are up to 3 times wider than in the FDM case. The LF estimation using our model shows that a correction for the number count is required, up to one order of magnitude, in the luminosity range of $\geq 5 \times 10^8 L_\odot$. Our reconstruction method for the line LF can be applied to future blind line surveys.
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All authors Natsuki H. Hayatsu, Rob J. Ivison, Paola Andreani, Fabrizia Guglielmetti, Zhi-Yu Zhang, Andy Biggs, Hideki Umehata, Yuichi Matsuda, Naoki Yoshida, Mark A. Swinbank, Kotaro Kohno, Yoichi Tamura, Bunyo Hatsukade, Kouichiro Nakanishi, Yiping Ao, Tohru Nagao, Mariko Kubo, Tsutomu T. Takeuchi, Minju Lee, Takuma Izumi, Soh Ikarashi, Tohru Yamada
High Energy Astrophysical Phenomena
Relativistic Jets and Winds in Radio-Identified Supermassive Black Hole Binary Candidates
Andrew G. Sullivan, Roger D. Blandford, Anna Synani et al. (+4 more)
Supermassive black hole binary systems (SMBHBs) are thought to emit the recently discovered nHz gravitational wave background; however, not a single individual nHz source has been confirmed to date. Long-term
radio-monitoring at the Owens Valley
Radio Observatory has revealed two potential SMBHB candidates: blazars PKS 2131-021 and PKS J0805-0111. These sources show periodic flux density variations across the electromagnetic spectrum, signaling the presence of a good clock. To explain the emission, we propose a generalizable jet model, where a mildly relativistic wind creates an outward-moving helical channel, along which the ultra-relativistic jet propagates. The observed flux variation from the jet is mostly due to aberration. The emission at lower frequency arises at larger radius and its variation is consequently delayed, as observed. Our model reproduces the main observable features of both sources and can be applied to other sources as they are discovered. We make predictions for
radio polarization, direct imaging, and emission line variation, which can be tested with forthcoming observations. Our results motivate future numerical simulations of jetted SMBHB systems and have implications for the fueling, structure, and
evolution of blazar jets.
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All authors Andrew G. Sullivan, Roger D. Blandford, Anna Synani, Philipe V. de la Parra, Noémie Globus, Mitchell C. Begelman, Anthony C.S. Readhead
Earth and Planetary Astrophysics
Mapping the Cloud-Driven Atmospheric Dynamics & Chemistry of an Isolated Exoplanet Analog with Harmonic Signatures
Michael K. Plummer, Francis P. Cocchini, Peter A. Kearns et al. (+12 more)
Young planetary-mass objects and brown
dwarfs near the L/T spectral transition exhibit enhanced spectrophotometric variability over field brown
dwarfs. Patchy clouds, auroral processes, stratospheric hot spots, and complex carbon chemistry have all been proposed as potential sources of this variability. Using time-resolved, low-to-mid-resolution spectroscopy collected with the JWST/NIRISS and NIRSpec instruments, we apply harmonic analysis to SIMP J013656.5+093347, a highly variable, young, isolated planetary-mass object. Odd harmonics (k = 3) at pressure levels ~ 1 bar, corresponding to iron and forsterite cloud formation, suggest a potential North-South hemispheric asymmetry in the cloudy, and likely equatorial, regions. We use the inferred harmonics, along with 1-D substellar atmospheric models, to map the flux variability by atmospheric pressure level. We identify distinct time-varying structures in the near-infrared that we interpret as planetary-scale wave (e.g., Rossby or Kelvin)-associated cloud modulation. We detect deviations from bulk (composite) variability in water (S/N = 14.0), carbon monoxide (S/N = 13.0), and methane (S/N = 14.9) molecular signatures. Forsterite cloud modulation is anti-correlated with overlying carbon monoxide and water abundances and correlated with deep methane absorption, suggesting complex interaction between cloud formation, atmospheric chemistry, and temperature structure. Furthermore, we identify distinct harmonic behavior between methane and carbon monoxide absorption bands, providing evidence for time-resolved disequilibrium carbon chemistry. At the lowest pressures (< 100 mbar), we find mapped methane lines transition from absorption to emission, supporting evidence of high-altitude auroral heating via electron precipitation.
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All authors Michael K. Plummer, Francis P. Cocchini, Peter A. Kearns, Allison McCarthy, Étienne Artigau, Nicolas B. Cowan, Roman Akhmetshyn, Johanna Vos, Evert Nasedkin, Channon Visscher, Björn Benneke, René Doyon, Stanimir A. Metchev, Jason F. Rowe, Genaro Suárez
Astrophysics of Galaxies
Photometric stellar masses for galaxies in DESI Legacy Imaging Surveys
Ivana Ebrová, Michal Bílek and Jiří Eliášek
In many areas of extragalactic astrophysics, we need to convert the luminosity of a
galaxy into its
stellar mass. In this work, we aim to find a simple and effective formula to estimate the
stellar mass from the images of
galaxies delivered by the currently popular DESI Legacy Imaging Surveys. This survey provides an unsurpassed combination of a deep imaging with an extensive sky coverage in up to four photometric bands. We calibrated the sought formula against a sample of local
galaxies observed by the Spitzer Survey of
Stellar Structure in
Galaxies (S$^4$G) that was directly dedicated to measure the
stellar masses. For the absolute magnitudes $M_g$ and $M_r$ of a
galaxy in the Legacy Surveys $g$ and $r$ bands, we find that the
stellar masses can be estimated as $0.673M_g - 1.108M_r + 0.996$ with the scatter of 25%. Employing more complex functions does not improve the estimate appreciably, even after including the
galaxy ellipticity, Sérsic index, or the magnitudes in different Legacy Surveys bands. Generally, measurements in $r$ band were the most helpful ones, while adding $z$-band measurements did not improve the mass estimate much. We provide a Python-based script photomass\_ls.py to automatically download images of any
galaxy from the Legacy Surveys database, create image masks, generate GALFIT input files with well-assessed initial values, perform the GALFIT photometry, and calculate the
stellar mass estimate. Additionally, we tuned another version of the formula to the magnitudes provided by the Siena
Galaxy Atlas 2020 (SGA-2020) with a scatter of 29%. For both\,–\,our default and SGA-2020 formula, we offer two alternatives derived from different calibrations of S$^4$G masses that were based on different methods and assumptions.
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Solar and Stellar Astrophysics
Rotation Periods for Stars in Open Cluster NGC 6819 From Kepler IRIS Light Curves
Sabina Sagynbayeva, Isabel L. Colman and Will M. Farr
We present an updated catalog of
stellar rotation periods for the 2.5 Gyr open cluster NGC 6819 using the Kepler IRIS light curves from superstamp data. Our analysis uses Gaussian Process modeling to extract robust rotation signals from image subtraction light curves, allowing us unprecedented data access and measurement precision in the crowded cluster field. After applying stringent quality and contamination cuts, we identify 271 reliable rotation periods, representing by far the largest sample of rotators measured in a single intermediate-age cluster. Compared to previous work, which relied on only ~30
stars, our catalog extends the gyrochronological sequence of NGC 6819 with an order of magnitude more measurements and improved precision. The expanded
dataset reveals both the expected temperature-dependent
spin-down trend and substantial scatter at fixed effective temperature, including a bimodal distribution of fast and slow rotators. We also identify a distinct “pile-up” sequence consistent with predictions of weakened
magnetic braking at critical Rossby numbers. These results strengthen this cluster's role as a
benchmark for
stellar spin evolution, while also highlighting the limitations of traditional gyrochronology at older ages. The final catalog and the model implementations are all available on Zenodo.
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Astrophysics of Galaxies
Measurement of Substructure from the Kinematics of the GD-1 Stellar Stream
Jacob Nibauer, Ana Bonaca, Adrian M. Price-Whelan et al. (+2 more)
Stellar streams are sensitive tracers of low-mass dark matter subhalos and provide a means to test the Cold Dark Matter (CDM) paradigm on small scales. In this work, we connect the intrinsic velocity dispersion of the GD-1 stream to the number density and internal structure of dark matter subhalos in the mass range $10^5$-$10^9 M_\odot$. We measure the radial velocity dispersion of GD-1 based on 160 identified member
stars across four different spectroscopic catalogs. We use repeat observations of the same
stars to constrain binarity. We find that the stream's intrinsic radial velocity dispersion ranges from approximately $2$-$5 \textrm{km} \textrm{s}^{-1}$ across its length. The region of GD-1 with the highest velocity dispersion represents a $4\sigma$ deviation from unperturbed stream models formed in a smooth Milky Way potential, which are substantially colder. We use perturbation theory to model the stream's velocity dispersion as a function of dark matter subhalo population parameters, including the number of low-mass subhalos in the Milky Way, the dark matter half-mode mass, and the mass-concentration relation of subhalos. We find that the observed velocity dispersion can be explained by numerous impacts with low-mass dark matter subhalos, or by a single impact with a very compact subhalo with $M \gtrsim 10^8 M_\odot$. Our constraint on the fraction of mass in subhalos is $f_{\mathrm{sub}} = 0.05^{+0.08}_{-0.03}$ (68% confidence). In both scenarios, our model prefers subhalos that are more compact compared to CDM mass-size expectations. These results suggest a possible deviation from CDM at low subhalo masses.
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All authors Jacob Nibauer, Ana Bonaca, Adrian M. Price-Whelan, David N. Spergel, Jenny E. Greene
Astrophysics of Galaxies
Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal): IV. On the inner Milky Way stellar age distribution
Tomás Ruiz-Lara, David Mirabal, Carme Gallart et al. (+15 more)
The Milky Way's inner region is dominated by a
stellar bar and a boxy-peanut shaped bulge. However, which
stellar populations inhabit the inner
Galaxy or how
star formation proceeded there is still unknown. The difficulty in studying these
stars stems from their location in dense regions that are strongly impacted by extinction and crowding effects. In this work, we use
star formation histories computed in the
solar neighbourhood using
Gaia Colour-Magnitude Diagram fitting to shed light onto the
evolution of the central regions of our
Galaxy. For that, we have obtained precise age distributions for the non-negligible amount of super metal-rich
stars ([M/H] $\sim$ 0.5) in the
solar neighbourhood (more than 5$\%$ of the total
stars within 400 pc of the plane). Assuming that these
stars were born in the inner
Galaxy and migrated outwards, those distributions should be indicative of the true
stellar age distribution in the inner
Galaxy. Surprisingly, we find that these age distributions are not continuous but show clear signs of episodic
star formation ($\sim$~13.5, 10.0, 7.0, 4.0, 2.0 and less than 1~Gyr ago). Interestingly, with the exception of the 4~Gyr event, the timings of the detected events coincide with the formation of the primitive Milky Way and with known merging events or satellite encounters (
Gaia-Enceladus-Sausage, Sagittarius
dwarf galaxy, and the Magellanic Clouds), suggesting that these could have induced enhanced and global
star-forming episodes. These results are compatible with a scenario in which
Gaia-Enceladus-Sausage is responsible for the formation of the bar 10 Gyr ago. However, we cannot associate any
accretion counterpart with the 4-Gyr-ago event, leaving room for a late formation of the bar, as previously proposed. A qualitative comparison with the Auriga Superstars simulations suggesting a possible link to bar dynamics and satellite
accretion. [Abridged]
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All authors Tomás Ruiz-Lara, David Mirabal, Carme Gallart, Robert Grand, Francesca Fragkoudi, Isabel Pérez, Santi Cassisi, Emma Fernández-Alvar, Anna B. Queiroz, Guillem Aznar-Menargues, Yllari K. González-Koda, Alicia Rivero, Francisco Surot, Guillaume F. Thomas, Rebekka Bieri, Facundo A. Gomez, Rüdiger Pakmor, Freeke van de Voort
High Energy Astrophysical Phenomena
Noisy Timing Behavior is a Feature of Central Compact Object Pulsars
K. I. Perez, E. V. Gotthelf and J. P. Halpern
We present a timing study of the three known central compact object (CCO)
pulsars, isolated cooling
neutron stars in
supernova remnants, using Chandra, XMM-Newton and NICER observations spanning two decades. Relative to canonical young
pulsars, CCOs are spinning down at a very slow rate $|\dot f| <10^{-15}$ s$^{-2}$, implying a surface dipole
magnetic field strength $B_s < 10^{11}$ G that is too weak to account for their X-ray-emitting hot spots. Two CCO
pulsars with sufficiently long monitoring, 1E 1207.4$-$5209 and PSR J0821$-$4300, are seen to deviate from steady
spin-down; their timing residuals can be modeled by one or more glitches in $f$ and $\dot f$, or alternatively by extreme timing noise. For the third CCO
pulsar, PSR J1852+0400, the sparse temporal coverage was insufficient to detect such effects. Glitch activity and timing noise in large samples of rotation-powered
pulsars correlate best with $\dot f$, while the timing irregularities of the first two CCOs are extreme compared to
pulsars of the same $\dot f$. Nevertheless, timing activity in CCOs may arise from properties that they share with other young but more energetic
pulsars: high internal temperature, strong buried
magnetic field and superfluid behavior. Alternatively, continuing low-level
accretion of
supernova debris is not ruled out as a source of timing noise in CCOs.
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High Energy Astrophysical Phenomena
Jittering jets in stripped-envelope core-collapse supernovae
Nikki Yat Ning Wang, Dmitry Shishkin and Noam Soker
We compare the expected explosion time of core-collapse
supernovae (CCSNe) in the jittering jets explosion mechanism (JJEM) to that in the
neutrino-driven (the delayed
neutrino) mechanism, and conclude that for most, but not all,
stellar models, even when the
neutrino-driven mechanism might have led to an explosion, the JJEM starts to operate before the
neutrino mechanism fully revives the stalled shock. To achieve this goal, we conduct comprehensive one-dimensional
stellar evolution simulations using the code mesa to determine the expected explosion time according to the JJEM, which corresponds to the time when the inner convective layer of the core is accreted onto the newly born
neutron star (NS). We present results for many hydrogen-rich, hydrogen-stripped, and helium+hydrogen-stripped envelope CCSN progenitor models. We find that most, but not all, of our models in the initial mass range of $M_{\rm ZAMS}=12M_\odot$ to $M_{\rm ZAMS}=40M_\odot$, have at least one strong convective zone inside the mass coordinate that is the maximum baryonic mass of an NS, $m \simeq 2.65\ M_\odot$, which can facilitate the JJEM. This study contributes to establishing the JJEM as a viable explosion mechanism of CCSNe.
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Earth and Planetary Astrophysics
Understanding the Origins of Super-Puff Planets: A New Mass-Loss Regime Coupled to Planetary Evolution
Yao Tang, Jonathan J. Fortney, Ruth Murray-Clay et al. (+1 more)
Super-puffs are a class of low-mass, large-radius
planets that have challenged
planet formation and
evolution models. Their high inferred H/He mass fractions, required to explain their physical sizes, would lead to rapid atmospheric escape, raising questions about their long-term retention. Recent modeling work indicates that low-mass
planets typically require 50% less H/He mass to match their observed radius, due to significant roles of the radiative atmosphere and interior heating from the rock/iron core. Here, through a new quantitative analysis of XUV-driven escape in sub-Neptunes, we find that previous studies overestimated mass loss, as scaling laws in low-
gravity regimes deviate greatly from the widely used energy-limited regime. We define a new regime, thermal-energy-mediated photoevaporation (TEMP), in which thermal energy conversion critically sets the mass-loss rate. These effects make super-puffs more resilient to mass loss than previously thought. We develop a coupled
evolution model integrating this updated thermal
evolution framework with a 1D hydrodynamic photoevaporation model. Applying this novel, joint model to observed super-puffs and young low-density
planets, we find that their masses, radii and transit pressures align with predictions assuming either a clear or hazy atmosphere. This indicates that super-puffs have undergone a combination of boil-off and photoevaporative mass loss, with boil-off dominating the process. Our results indicate that low-density
planets typically possess both a thick convective envelope and substantial radiative atmosphere, which contribute to their large radii. For this to occur, these
planets must have intermediate masses of 5-10$M_\oplus$ and receive
stellar insolation $\lesssim 30F_\oplus$, favoring FG-type
stars over M-
dwarfs.
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All authors Yao Tang, Jonathan J. Fortney, Ruth Murray-Clay, Madelyn Broome
Astrophysics of Galaxies
The role of environment in triggering AGN – evidence for a change at $z\sim$1
Jason Reeves, Anna Sajina, Henry Adair et al. (+2 more)
What triggers AGN in some
galaxies and what role does this brief period of activity play in the overall
evolution of
galaxies are still open questions. This paper explores whether or not the local, on scales of $\approx$1\,Mpc,
galaxy density plays a role in triggering AGN when controlling for
stellar mass. We consider this question as a function of
redshift and AGN selection in the X-ray vs. in the IR. We use available density maps within the 4.8\,sq.deg. XMM-LSS field in the
redshift range $0.1 < z < 1.6$. Our key result is that the environment may play a role in triggering IR AGN. In particular, at $z > 1.2$ the incidence of AGN increases in higher density environments, controlling for
stellar mass. However, this dependence reverses at $z < 1.2$ where the incidence of IR AGN is higher in lower density environments. By contrast, among X-ray selected AGN there is no significant local density dependence. Bootstraping analysis confirms these conclusions. While these results agree with previous work on both obscured and unobscured AGN this is the first study to use a consistent methodology across IR and X-ray samples, as well as study IR dependence in this full
redshift range. Upcoming large spectroscopic surveys such as the
Prime Focus Spectrograph (PFS)
galaxy evolution survey will be critical in further elucidating how the environment affects AGN triggering across different
cosmic epochs.
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All authors Jason Reeves, Anna Sajina, Henry Adair, Duncan Farrah, Mark Lacy
Solar and Stellar Astrophysics
Near-infrared photometry of the central stars of planetary nebulae with the VVVX survey
Dante Minniti, Vasiliki Fragkou, Javier Alonso-García et al. (+2 more)
Achieving accurate photometric characterizations of central
stars of planetary nebulae (CSPNe) toward the
galactic plane is significantly hindered by the high levels of interstellar extinction in these regions. However, near-infrared (NIR) observations offer a more effective alternative, as extinction is substantially reduced at these wavelengths. By mitigating the effects of interstellar extinction via NIR observations of the
Galactic disk and bulge, we seek to improve the identification and characterization of CSPNe in these regions, enabling a deeper understanding of their properties and evolutionary status. We used NIR photometry from the VISTA Variables in the Vía Láctea (VVV) survey and its extension VVVX to define the NIR photometry of a large sample of CSPNe recently identified with
Gaia EDR3 data. We explored the optical and NIR properties of all CSPNe in our sample and searched for eclipsing binary candidates among them by employing relevant catalogs. We present a homogeneous catalog of 1274 CSPNe, including their Z, Y, H, J, and K NIR magnitudes and errors. We also include our findings on the photometric properties of our sample. We report 14 CSPNe with a large IR excess indicating cool companions and/or surrounding discs and 56 eclipsing binary candidates. Based on the present VVVX CSPN catalog, we conclude that NIR photometry can prove valuable for further and in-depth studies of CSPNe. Subsequent studies ought to focus on exploring the true nature of the CSPNe that present IR excess as well as eclipsing-binary CSPNe candidates.
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All authors Dante Minniti, Vasiliki Fragkou, Javier Alonso-García, Daniel Majaess, Arianna Cortesi
Earth and Planetary Astrophysics
Investigating the Sulfur Mystery in Protoplanetary Disks Through Chemical Modeling
Becky J. Williams, L. Ilsedore Cleeves, Rachel E. Gross et al. (+1 more)
Sulfur is a critical element to life on Earth, and with detections of sulfur-bearing molecules in
exoplanets and comets, questions arise as to how sulfur is incorporated into
planets in the first place. In order to understand sulfur's journey from molecular clouds to
planets, we need to understand the molecular forms that sulfur takes in protoplanetary disks, where the rotational emission from sulfur-bearing molecules in the gas phase indicates a very low abundance. To address this question, we have updated the 2D time-dependent disk chemical modeling framework of Fogel et al. (2011) to incorporate several new sulfur species and hundreds of new sulfur reactions from the literature. Specifically, we investigate the main molecular forms that sulfur takes in a disk orbiting a
solar mass young T Tauri
star. We explore the effects of different volatile (reactive) sulfur abundances, C/O ratios, initial sulfur molecular forms, and
cosmic-ray ionization rates. We find that a high C/O ratio can explain both the prevalence of CS observed in disks and the lack of SO detections, consistent with previous results. Additionally, initial sulfur form greatly affects the ice abundances in the lower layers of the disk, which has implications for comet formation and future observations with JWST.
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All authors Becky J. Williams, L. Ilsedore Cleeves, Rachel E. Gross, Jackson Baker
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Uncertainty in predicting the stochastic gravitational wave background from compact binary coalescences
Michael Ebersold and Tania Regimbau
The
stochastic gravitational wave background from compact binary coalescences is expected to be the first detectable
stochastic signal via cross-correlation searches with terrestrial detectors. It encodes the cumulative merger history of
stellar-mass binaries across
cosmic time, offering a unique probe of the high-
redshift Universe. However, predicting the background spectrum is challenging due to numerous modeling choices, each with distinct uncertainties. In this work, we present a comprehensive forecast of the astrophysical gravitational wave background from binary black holes, binary
neutron stars, and
neutron star-black hole systems. We systematically assess the impact of uncertainties in population properties, waveform features, and the modeling of the merger rate
evolution. By combining all uncertainties, we derive credible bands for the background spectrum, spanning approximately an order of magnitude in the fractional energy density. These results provide thorough predictions to facilitate the interpretation of current upper limits and future detections.
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Cosmology and Nongalactic Astrophysics
Angular BAO Measurements with the DESI DR1 BGS Sample
Paula S. Ferreira, Ulisses Ribeiro, Pedro da Silveira Ferreira et al. (+2 more)
We employ a model-independent approach in both the correlation function estimation and the angular BAO feature estimation by computing the angular two-point correlation function. First, we conducted a series of tests to the available DESI tracers to check their representativeness to angular clustering; the result was that, considering the completeness of the first data release across the footprint, we could only make use of the BGS sample for the effective
redshifts 0.21 (BGS1) and 0.25 (BGS2). For a reliable analysis in such low
redshift, we use the bootstrap of the data itself to construct a covariance
matrix that accounts for systematics. We use a purely statistical method to correct the projection effects and find that our results show reasonable agreement with the $\theta_{\rm BAO}$ expected by the CPL parameters obtained by DESI DR1, being BGS1 $12.77 \pm 1.15$ degrees and BGS2 $11.70 \pm 1.21$ degrees. This means a tension at the $2.4\sigma$ ($2.7\sigma$) level for BGS1 (BGS2) CPL parametrization, while a $2.84\sigma$ ($3.02\sigma$) discrepancy within the predicted by $\Lambda$CDM. We conclude that, with the current sample available, the use of an angular correlation function serving as the BAO probe, although prefers the CPL parametrization, does not provide conclusive results regarding the best cosmological model.
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All authors Paula S. Ferreira, Ulisses Ribeiro, Pedro da Silveira Ferreira, Clécio R. Bom, Armando Bernui
High Energy Astrophysical Phenomena
The Progenitor of the S147 Supernova Remnant
Elvira Cruz-Cruz and Christopher S. Kochanek
The
supernova remnant (SNR) S147 contains the
pulsar PSR J0538+2817 and a likely unbound binary companion, HD 37424. It is the only good
Galactic candidate for a binary unbound by a core-collapse
supernova (SN). Using
Gaia DR3 parallaxes and photometry, we select the
stars local to SNR S147 in a cylinder with a projected radius of $100$ pc and a parallax range of $0.614 < \varpi < 0.787$ mas (a length of $\simeq 360$ pc). We individually model the most luminous of these
stars. The two most luminous single
stars are the unbound binary companion, HD 37424, and HD 37367, with estimated masses of $(13.51\pm0.05) M_{\odot}$ and $(14.30\pm0.09) M_{\odot}$, respectively. The two most luminous binary systems are the spectroscopic binary HD 37366 and the eclipsing binary ET Tau that have primary masses of $(20.9\pm0.12) M_{\odot}$ and $(16.7\pm0.09) M_{\odot}$, respectively. We model the
Gaia color-magnitude diagram (CMD) of this local
stellar population using both single
stars and a model consisting of noninteracting binaries using
Solar metallicity PARSEC isochrones. For both models, the estimated age distributions of the $439$ $M_{G} < 0$ mag
stars favor a high mass progenitor of $21.5M_{\odot}-41.1M_{\odot}$ for the SN.
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Astrophysics of Galaxies
In-situ globular clusters in alternative dark matter Milky Way galaxies: a first approach to fuzzy and core-like dark matter theories
Pierre Boldrini and Paola Di Matteo
We present a first analysis of the dynamics of in-situ globular clusters (GCs) in Milky Way (MW)-like
galaxies embedded in fuzzy dark matter (FDM)
halos, combining cosmological assembly histories from the TNG50 simulation with dedicated orbital integrations and analytical models. GC populations are initialized with identical distributions in normalized $E$-$L_{z}$ in matched CDM and FDM
halos. In a universe dominated by FDM, we identify three distinct regimes for the in-situ GC population depending on the particle mass $m_{22} \equiv m_{\chi}/ 10^{-22}~\mathrm{eV}$. For $m_{22} < 7$,
baryons dominate the inner potential, which remains steep and centrally concentrated, confining GC orbits to a narrow region and producing less massive, more compact systems than in CDM. For $m_{22} \sim 7$, GC properties resemble those in CDM, with similar mass and spatial distributions. For $m_{22} > 7$, the dark matter becomes both compact and globally dominant, generating a deeper and more extended gravitational potential that supports a wider range of stable GC orbits, resulting in more massive and spatially extended GC systems. Finally, we extend our framework to make predictions for GC populations in alternative DM models, including warm dark matter and self-interacting dark matter, in both MW-like and
dwarf galaxies. Our findings demonstrate that in-situ GC systems offer a sensitive and independent probe of the underlying DM physics, opening new avenues for observational constraints with upcoming Euclid.
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Cosmology and Nongalactic Astrophysics
Scalar-induced gravitational waves including isocurvature perturbations with lattice simulations
Xiang-Xi Zeng
Scalar-induced gravitational waves (SIGWs) open a unique window into early-universe physics. While their generation from adiabatic perturbations has been extensively studied, the contribution from isocurvature perturbations remains largely unexplored. In this work, we develop a
lattice simulation framework to compute the
stochastic gravitational wave background from both pure isocurvature and mixed initial conditions. Our numerical results show excellent agreement with semi-analytical predictions in the pure isocurvature case. We further analyze multi-peak structures under general initial conditions and find that they closely match those produced in purely adiabatic scenarios. Additionally, we examine SIGWs in early matter-dominated eras, revealing that the peak amplitude and spectral slope are sensitive to the microphysical properties of the dominant field, such as the
primordial black hole mass, abundance, or
soliton decay rate. This study establishes
lattice simulations as a robust tool for predicting SIGW spectra from complex
primordial perturbations, with important implications for interpreting current and future gravitational wave observations.
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Solar and Stellar Astrophysics
Flare-Driven Plasma Dynamics and Elemental Abundance Redistribution
Biswajit Mondal and Amy R. Winebarger
Since the advent of X-ray and EUV spectroscopy, the discovery of the First Ionization Potential (FIP) effect–where coronal elemental compositions diverge from their photospheric values based on the element's FIP–has remained a key puzzle in
solar and
stellar astrophysics. These deviations exhibit significant fluctuations during
flares, yet their connection to
plasma dynamics has remained unclear. Here, we report a clear correlation between temperature-sensitive flaring
plasma emission and element-specific abundance changes for a
solar flare. These findings indicate that energy deposition in the chromosphere drives
plasma evaporation from different chromospheric heights, modulating elemental abundances. Hydrodynamic simulations support these observations, showing that varying energy deposition magnitudes generate
plasma upflows from different chromospheric heights, leading to element-specific FIP fractionation. These results provide new insights into the dynamic coupling of
flare energy,
plasma flows, and abundance variability, with implications for understanding coupling between different atmospheric layers.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Updating GUT-Scale Pole Higgs Inflation After ACT DR6
C. Pallis
We consider models of chaotic inflation driven by the real parts of a conjugate pair of
Higgs superfields involved in the spontaneous breaking of a grand unification
symmetry at a scale assuming its value within MSSM. We combine a superpotential, which is uniquely determined by applying a continuous R
symmetry, with two fractional shift-symmetric Kaehler potentials introducing two free parameters (p,N). The inflationary observables provide an excellent match to the recent ACT data for 1.355<=p<=6.7 and 6x10^-5<= N<=0.7. The attainment of inflation allows for subplanckian inflaton values and possibly detectable
primordial gravitational waves with (p,N) values of order unity. A solution to the mu problem of MSSM and baryogenesis via non-thermal leptogenesis can be also accommodated by
embedding the model into a B-L extension of MSSM.
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High Energy Astrophysical Phenomena
The very faint X-ray transient Swift J174610-290018 at the Galactic center
Giovanni Stel, Gabriele Ponti, Nathalie Degenaar et al. (+17 more)
Very Faint X-ray Transients (VFXTs) are a class of X-ray binary systems that exhibit occasional outbursts with peak X-ray luminosities (L_X< 1e36 erg s^-1) much lower than typical X-ray transients. On 22nd February 2024, during its daily
Galactic center monitoring, Swift-XRT detected a VFXT, 7 arcmin from Sgr A* dubbing it Swift J174610–290018. We aim to characterize the outburst that occurred in 2024, and a second, distinct outburst in 2025, to understand the nature and
accretion flow properties of this new VFXT. Swift-XRT light curves are used to constrain the duration of the two events. We carried out X-ray spectral analysis exploiting XMM and NuSTAR data. We used Chandra and XMM observations of the last 25 years to constrain the quiescent luminosity of the source. During the 2024 outburst, which lasted about 50 days, the source reached a luminosity in the 2-10 keV band of L_X = 1.2e35 erg s^-1 (assuming it is located at the
Galactic center). The 2025 outburst is shorter (about 5 days), and reached L_X = 9e34 erg s^-1. The spectral features of the source include an excess at 6.5-7 keV, which can be associated either with a single reflection line or with the ionized Fe XXV and XXVI lines. The same source was identified in both the XMM and Chandra catalogs of point sources (known as 4XMM J174610.7–290020). During previous detections, the source displayed luminosity levels ranging from L_X= 2e32 to L_X = 3e34 erg s^-1 between 2000 and 2010. Moreover, it exhibited a potential type I X-ray burst in 2004. The analysis of the outbursts and the potential type I burst strongly suggests the
neutron star low mass X-ray binary (NS-LMXB) nature of the VFXT. The source can be described by an
accretion disk corona (as has been recently proposed by the XRISM/Xtend analysis). This scenario explains the overall low luminosity of this transient and the peculiar iron lines in the spectrum.
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All authors Giovanni Stel, Gabriele Ponti, Nathalie Degenaar, Lara Sidoli, Sandro Mereghetti, Kaya Mori, Tong Bao, Giulia Illiano, Samaresh Mondal, Mark Reynolds, Chichuan Jin, Tianying Lian, Shifra Mandel, Simone Scaringi, Shuo Zhang, Grace Sanger-Johnson, Rudy Wijnands, Jon M. Miller, Jamie Kennea, Zhenlin Zhu
Cosmology and Nongalactic Astrophysics
Strong-lensing rates of massive black hole binaries in LISA
Juan Gutiérrez and Macarena Lagos
Similarly to electromagnetic (EM) signals, gravitational
lensing by intervening
galaxies can also affect gravitational waves (GWs). In this paper, we estimate the strong-
lensing rate of massive black hole mergers observed with LISA. Given the uncertainties in the source populations as well as in the population of
galaxies at high
redshift, we consider: six different source population models, including light and heavy seeds, as well as three lens population models, including
redshift-independent and
redshift-dependent
evolution properties. Among all the scenarios explored, the expected number of strong lensed events detected in a 4-year observation time in LISA ranges between 0.13-231 with most of them having two (one) images detectable in the heavy (light) seed scenarios. The event numbers obtained correspond to 0.2%-0.9% of all detected unlensed events. Out of all the detectable strong-lensed events, up to 61% (in the light-seed scenario) and 1% (in the heavy-seed scenario) of them are above the detectability threshold solely due to strong
lensing effects and would otherwise be undetectable. For detectable pairs of strong-lensed events by
galaxy lenses, we also find between 72%-81% of them to have time delays from 1 week to 1 year.
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Astrophysics of Galaxies
Investigating the need for a robust ultraviolet filter set aboard the Habitable Worlds Observatory
Kyle Cook, Benne Holwerda and Clayton Robertson
High resolution, ultraviolet imaging is often unavailable across the sky, even in heavily studied fields such as the Chandra Deep Field - South. The Habitable Worlds Observatory is one of two upcoming missions with the possibility of significant UV capabilities, and the only one early enough in development to consider suggestions to its design. In this paper, we conduct an initial study of how current common UV filter sets affect the results of spectral energy distribution fitting for the estimation of
galaxy parameter. This initial look is intended to motivate the need for future, more robust, SED fitting of mock
galaxies. We compare the broad near UV and far UV filters used by the GALEX mission to the three more narrow Swift UVOT filters. We find that the GALEX filters result in larger errors when calculating the UV beta parameter compared to UVOT, and provide little constraint on the
star formation age of a
galaxy. We further note the ability of the UVOT filters to investigate the 2175Å attenuation bump; GALEX has a reduced capacity to trace this same feature. Ultimately, we recommend that in order to optimize the effectiveness of HWO's ultraviolet capacity for transformative astrophysics, a minimum of a FUV filter with three medium band NUV filters should be adopted. This will combine the power of GALEX's wavelength range with the finer sampling of UVOT around an important
dust feature.
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Solar and Stellar Astrophysics
Observations of a Faint Nonthermal Onset before a GOES C-class Flare
Natália Bajnoková, Iain G. Hannah, Hannah Collier et al. (+6 more)
We present analysis of a GOES C1-class
flare from 2022 September 6, which was jointly observed as occulted by
Nuclear Spectroscopic
Telescope ARray (NuSTAR) and on-disk by Spectrometer/
Telescope for Imaging X-rays (STIX). NuSTAR observed faint coronal nonthermal emission as well as
plasma heating > 10 MK, starting 7 minutes prior to the
flare. This onset emission implies that during this time, there is a continuous electron acceleration in the corona which could also be responsible for the observed heating. The nonthermal model parameters remained consistent throughout the entire onset, indicating that the electron acceleration process persisted during this time. Furthermore, the onset coincided with a series of type III
radio bursts observed by Long Wavelength Array-1, further supporting the presence of electron acceleration before the
flare began. We also performed spectral analysis of the impulsive
flare emission with STIX (thermal and footpoint emission). STIX footpoints and the onset coronal source were found to have similar electron distribution power-law indices, but with increased low-energy cut-off during the
flare time. This could suggest that the nonthermal onset is an early signature of the acceleration mechanism that occurs during the main phase of the
flare.
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All authors Natália Bajnoková, Iain G. Hannah, Hannah Collier, Stephen M. White, Lindsay Glesener, Reed B. Masek, Marianne S. Peterson, Säm Krucker, Hugh S. Hudson