Earth and Planetary Astrophysics · Cross-listed from physics.ao-ph
On an Airborne Proton Accelerator for Enhancing Cloud Formation or Inducing their Precipitation
Orfeu Bertolami
We argue that an airborne
proton accelerator is an interesting tool for weather control. Following the findings of the CLOUD experiment at CERN, one expects that a beam of
protons, likewise
cosmic rays and other aerosols, can enhance the formation of low-altitude clouds, allow for tailor made cooling of overheated areas and induce the precipitation of high-altitude clouds that trap
solar radiation reflected from the ground. The
proton accelerator can also be used to mitigate droughts, regularise precipitation and avoid that it takes place through large and harmful storms.
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Instrumentation and Methods for Astrophysics
Systematic Polarization Errors from Parallactic-Angle Dependent Leakage in Pseudo-Circular Feeds
Dipanjan Mitra
Wideband
radio interferometers increasingly rely on analog quadrature hybrids to synthesize circular polarization from linear feeds. These systems are typically calibrated under the assumption that instrumental polarization leakage can be represented as a static complex offset, independent of parallactic angle. In this work, we demonstrate that this assumption breaks down in the presence of realistic hybrid imperfections. We show that amplitude and phase errors in the hybrid $\mathbf{H}(\nu)$ introduce a non-commutative interaction with parallactic rotation $\mathbf{R}(\chi)$, such that [$\mathbf{H}(\nu)\mathbf{R}(\chi) \neq \mathbf{R}(\chi)\mathbf{H}(\nu)$] leading to a time-dependent effective leakage term that rotates in the Stokes $(Q,U)$ plane. This effect causes systematic distortions in polarization angle and introduces frequency-dependent biases that can mimic or corrupt Faraday rotation measurements. We derive a first-order analytic model for this leakage and demonstrate that it manifests as a deterministic, geometrically modulated error proportional to total intensity. To mitigate this effect, we introduce a Static Offset Pre-correction (SOP) method that operates in the
antenna frame, inverting the hybrid response prior to parallactic de-rotation. Unlike conventional calibration approaches, SOP removes the non-commutative error in the Jones domain, preventing its projection into the sky frame. Our results show that hybrid-induced leakage is not merely a calibration artifact but a fundamental systematic error that must be addressed to achieve high-fidelity wideband polarimetry.
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Astrophysics of Galaxies
The Information Content of Quasar Variability Light Curves: How Well Can we Infer Stochastic Model Parameters?
Brendon J. Brewer, Geraint F. Lewis, Xiang Yu et al. (+1 more)
Quasar variability, driven by multi-scale physical processing within a relativistic
accretion disk, is commonly modelled with
stochastic time series models. The simplest of these is the Damped Random Walk (DRW), also known as the Ornstein-Uhlenbeck (OU) process. Here, we demonstrate that, when fitting such a model to
quasar light curve data, the mean of the light curve, $\mu$, should not be fixed (which is the typical approach), as this leads to overconfident inferences about the variability timescale $\tau$, with substantially underestimated uncertainties. However, the short term
volatility parameter $\eta$ is typically very well constrained from short light curves. Through simulations, we compute information theoretic quantities such as the conditional
entropy and the mutual information, confirming that light curves provide much more information about $\eta$ than about $\tau$. As a result, we recommend that future
quasar variability studies focus on $\eta$ rather than $\tau$. To demonstrate this approach, we fit a hierarchical
Bayesian regression model for $\eta$ as a function of bolometric luminosity and rest wavelength to a
dataset of 570 light curves measured over decades. We perform the fit using a likelihood function that uses the light curves directly, rather than using intermediate $\eta$ values from individual light curve fits. We find that
volatility decreases as a function of both bolometric luminosity and rest wavelength. The
volatility also decreases more steeply with
redshift than time dilation alone would suggest, pointing to an increase in intrinsic
volatility as
quasars evolve over
cosmic time.
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All authors Brendon J. Brewer, Geraint F. Lewis, Xiang Yu, Yuan Li
Astrophysics of Galaxies
Multiwavelength study of the Carina–Sagittarius Arm. I.Astrometric and photometric search for new open clusters in the 320$^ \circ $ $\le$ l $\le$ 325$^ \circ $ region
M.A. Corti, L. Rizzo, L.G. Paíz et al. (+1 more)
Our main goal is to determine whether the lower
stellar density observed in the Carina-Sagittarius Arm region (320$^ \circ$ $\le$ l $\le$ 325$^ \circ$, $|b| \le$ $1^ \circ$) is an intrinsic structural feature of the spiral arm or a consequence of high interstellar reddening and extinction along the line of sight. We performed a systematic search for new open clusters using the HDBSCAN
algorithm on
Gaia DR3 astrometric data. The physical reality of the candidates was validated through a multiwavelength analysis, integrating
Gaia photometry with NIR of the 2MASS catalog, MIR photometric information of the WISE catalog to identify young
stellar objects (YSOs), and the
radio continuum emission at 843 MHz with SUMSS survey to identify and associated interstellar material. We report the discovery of five new open clusters, the ESFERA sample. Our analysis reveals four young systems (10-50 Myr), with ESFERA 3 hosting YSOs, while ESFERA 5 is identified as a 2 Gyr old cluster. Although the region lacks massive
star-forming complexes, these clusters trace active, despite the fact that lower-efficiency,
star formation within the region. Our results suggest that this region represents an intrinsic
star-formation "valley" or low-density node (the "string" in a "beads on a string" morphology) rather than an effect of extinction. The discovery of these clusters demonstrates that while the local surface density is below the critical threshold for massive complexes,
star formation persists in isolated, small-scale pockets throughout the arm.
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All authors M.A. Corti, L. Rizzo, L.G. Paíz, G.S. Elizalde Caviglia
Earth and Planetary Astrophysics
Assessment of the Mass Loss and Radius Change of 3I/ATLAS Based on Observed Production Rates
Tessa T. Frincke and Darryl Z. Seligman
Formed from the debris of
planet formation, interstellar comets provide invaluable insights into the chemical compositions of planetary systems outside of our
Solar System. Spectroscopic observations of 3I/ATLAS, the third interstellar object, reveal production of numerous volatiles and refractory species throughout its trajectory. In this paper we present a framework to calculate the change in radius of an object on an arbitrary trajectory at any point in its orbit, applicable to any small body experiencing mass loss. We next provide a comprehensive, machine readable table containing volatile and refractory production rates from all reported observations of 3I/ATLAS pre- and post-perihelion. Applying these equations to 3I/ATLAS, we calculate that it has lost $\sim$ 1.71-5.24 meters of its surface during its passage through the
Solar System from gas alone, corresponding to $\sim$ 10$^{10}$ kg and $\sim$ 0.40-1.25% of its initial mass. Considering
dust-to-gas ratios from 1-4, we estimate surface erosion down to depths $>$10 meters. We present these calculations as approximations and lower limits based on discontinuous observational data with varying methodology and instrumentation. Conservative and optimistic estimates were calculated over a range of heliocentric distances defined by the onset of activity in reported observations and the typical onset of sublimation distance for each species, respectively. The reported production rates combined with the change in radius calculation can be used to estimate subsurface locations of various species within the
nucleus of 3I/ATLAS.
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Cosmology and Nongalactic Astrophysics
A short review on Quintom dark energy theory
Xin Ren, Si-Yu Li, Yang Liu et al. (+3 more)
In this paper, we provide a short review on the Quintom dark energy theory. Firstly, we discuss the No-Go
theorem associated with dynamical dark energy, then present some examples of models in which the equation of state (EoS) evolves with time and can cross $w=-1$ . Secondly, we discuss the bouncing universe and emergent universe with Quintom matter. Finally, we discuss the possibility of studying the nature of dark energy by measuring the
Cosmic Microwave Background (CMB) polarization rotation angle.
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All authors Xin Ren, Si-Yu Li, Yang Liu, Yifu Cai, Hong Li, Xinmin Zhang
Astrophysics of Galaxies
Inside-Out vs. Outside-In Quenching of MaNGA Galaxies: Dependence on Stellar Mass and Environment
Zi-Hua Ho, Lihwai Lin, Hung-Yu Jian et al. (+6 more)
Galaxy quenching, the cessation of
star formation, can proceed in spatially distinct ways, commonly described as inside-out or outside-in. However, the inferred quenching pattern depends strongly on how quenched or quenching regions are defined observationally. We utilize a sample of approximately 10,000
galaxies from the Mapping Nearby
Galaxies at APO (MaNGA) DR17 survey to systematically compare four widely used diagnostics of
star formation suppression: specific
star formation rate (sSFR), the 4000 Å break (Dn4000), post-starburst (PSB), and low-ionization (
nuclear) emission-line region (LI(N)ER) emission, to examine how tracer choice influences the inferred spatial quenching pattern. Using the non-parametric method developed by Lin et al. (2019), we classify
galaxies into inside-out and outside-in quenching modes based on the location on the plane of the fraction of the quenched area (Fq) and the concentration of quenched area (Cq). We find that the sSFR criterion yields comparable proportions of
galaxies classified as inside-out and outside-in, while Dn4000 and LI(N)ER diagnostics strongly favor inside-out patterns. Because PSB traces a distinct transitional phase, PSB-selected spaxels occupy a different region of the Fq-Cq plane. Across most diagnostics, the fraction of
galaxies classified as inside-out increases with
stellar mass, while outside-in patterns are more common in lower-mass systems, especially among satellites. In contrast, the dependence of quenching mode on
halo mass is weaker and less consistent across diagnostics. These differences show that the tracers probe complementary stages and timescales of
star-formation suppression, and together provide a more complete view of spatially resolved quenching.
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All authors Zi-Hua Ho, Lihwai Lin, Hung-Yu Jian, Bau-Ching Hsieh, Carlos López-Cobá, S. F. Sánchez, Wen-Yen Wu, Shuai Feng, Shiyin Shen
Instrumentation and Methods for Astrophysics
PSF-like Alpha-Particle Events in LSST Images
Guillem Megias Homar, Craig S. Lage, Pierre-François Léget et al. (+6 more)
Rare $\alpha$-particle-induced charge clusters appear in LSST images as compact, PSF-like sources with a median FWHM of $0.\!\!^{\prime\prime}95$ and median ellipticity consistent with zero, closely resembling unresolved astrophysical point sources. These events are detected in both dark and science exposures at a rate of approximately $10^{-12}\ \mathrm{pixel}^{-1}\ \mathrm{s}^{-1}$. Their collected charge and morphology are consistent with energy deposition from $\sim$5 MeV $\alpha$-particles in silicon CCDs, and their spatial distribution across the focal plane suggests a localized material origin, plausibly associated with trace radioactive contamination in the cryostat aluminum. Despite their deceptive appearance, we demonstrate that a simple broadness statistic based on fourth-order moments cleanly separates these events from
stellar PSFs, enabling efficient rejection in coadded images and real-time alert streams. Such charge clusters do not impose an intrinsic bright-end contamination floor for Rubin transient searches, as genuine fast astrophysical events would exhibit characteristically different morphological signatures.
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All authors Guillem Megias Homar, Craig S. Lage, Pierre-François Léget, Steven M. Kahn, Christopher W. Stubbs, S. R. Kulkarni, Ian S. Sullivan, James F. Bosch, Eli S. Rykoff
Earth and Planetary Astrophysics
Is the Dark Comet 1998 KY$_{26}$ the Spacecraft Phobos 1?
Adam Hibberd, Adam Crowl, Carlos Gómez de Olea Ballester et al. (+1 more)
Since the discovery of new kinds of celestial bodies known as $dark~comets$, scientists have speculated about their ontology. A curious hybrid of comet and asteroid, these objects show significant non-gravitational accelerations (NGAs) yet exhibit absolutely no signs of cometary outgassing in the form of a coma or tail. The planned rendezvous of the Hayabusa2 spacecraft with 1998 KY$_{26}$ in July 2031 elevates the question of this so-called dark comet's nature beyond a purely research exercise, as the true nature of the object may have practical implications for the scientific return of the mission. This study examines the hypothesis that 1998 KY$_{26}$ may be of technogenic origin, in fact a relic of a historical Russian mission to Mars, the Phobos 1 probe, which suffered a failure 2 months after the launch in July 1988, due to upload of a faulty command. We find that two propulsive DeltaVs combined at 1.9 km/s, the first just after loss of mission and the second in May 1996, allow the orbits and phases of the two bodies to align, with an arbitrarily low $Mahalanobis~distance$ using the covariance of the dark comet in 6D phase space. There is also evidence that 1.9 km/s was within the performance envelope of Phobos 1, which had a powerful nitric acid and amine-based autonomous thruster for Mars Orbital Insertion (MOI).
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All authors Adam Hibberd, Adam Crowl, Carlos Gómez de Olea Ballester, Abraham Loeb
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Improving the resolution of double white dwarf systems with spaceborne gravitational wave observatories using a robust astrophysical prior
Shao-Dong Zhao, Xue-Hao Zhang, Soumya D. Mohanty et al. (+1 more)
Resolving the crowded population of double white
dwarf (DWD) binaries in data from spaceborne gravitational wave (GW) observatories (e.g., LISA, Taiji) remains a major analysis challenge. Comparable performance on addressing this problem has been achieved with two main approaches: global fit, in which resolvable sources are estimated simultaneously from the data, and iterative, where sources are estimated one at a time and subtracted out from the data. While the latter is computationally efficient, methods developed under this approach have traditionally followed a frequentist framework that ignores astrophysical priors. This work incorporates a strong astrophysical prior, derived from the mass limits of detached white
dwarfs and linking the GW signal frequency $f$ with its time derivative $\dot{f}$, into the iterative $\mathtt{GBSIEVER}$ pipeline. Applied to simulated LISA and LISA-Taiji network data, the method increases the number of confidently resolved sources by ${\approx}7.3\%$ (LISA-only) and ${\approx}14.6\%$ (network), respectively, and improves parameter estimation accuracy. The improvement persists across multiple realistic DWD population realizations, including in the low-frequency confusion-dominated regime, demonstrating the robustness and practical utility of astrophysically informed priors in iterative source extraction.
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All authors Shao-Dong Zhao, Xue-Hao Zhang, Soumya D. Mohanty, Yu-Xiao Liu
High Energy Astrophysical Phenomena
Deep Optical Follow-up Observations to IceCube Cosmic Neutrinos: a case for IC230724A with Subaru/HSC and prospects with Rubin/LSST
Shigeo S. Kimura, Masaomi Tanaka, Seiji Toshikage et al. (+8 more)
IceCube has been detecting
cosmic high-energy
neutrinos for more than 10 years, but their major sources are still under debate. To identify them, IceCube is issuing
neutrino alerts, which enable us to perform electromagnetic follow-up observations. In this paper, we present our Subaru/HSC deep optical follow-up observations down to 25.5 mag to a well-localized
neutrino event, IceCube 230724A. We conduct a dedicated analysis with extensive evaluation of background rates and true positive rates adopting the blind analysis policy to identify or disfavor
tidal disruption events (TDEs) as
cosmic neutrino sources. Our analysis found no TDE candidate in the region of interest. Rubin/LSST survey will enable us to constrain their fractional contribution to the
cosmic high-energy
neutrino background, either $\lesssim 60\%$ or $\gtrsim30\%$ for non-detection and detection, respectively, if Rubin covers the error regions of 10
neutrino events.
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All authors Shigeo S. Kimura, Masaomi Tanaka, Seiji Toshikage, Tomoki Morokuma, Nobuhiro Shimizu, Nozomu Tominaga, Naoki Yasuda, Yousuke Utsumi, Michitoshi Yoshida, Yasushi Fukazawa, Koji S. Kawabata
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The Heuristic Approach to General Relativity in the Laplace-Beltrami Formalism
Noah M. MacKay
The Laplace-Beltrami formalism, in which the
Ricci tensor in the Einstein field equations (EFEs) is formulated at leading-order in terms of the partial-differential Laplace-Beltrami operator, was previously applied to coalescing compact binaries (CCBs) generating gravitational waves (GWs). Supposing that the CCB is an effective singular body – a hollow mass-shell – that follows a Kerr metric Ansatz, the EFEs were approached variationally such that the Ansatz
geometric signature dictates the energetic output via $G_{\mu\nu}=8\pi GT_{\mu\nu}$. For the CCB mass-shell representation, the generated GW energy is treated as radiated surface energy via $E:=T_{00}V$. This surface energy yielded a close approximation to the cataloged GW coalescence energy, as previously shown in past comparisons. Given this success, it is logical to ask whether the Laplace-Beltrami formalism can be applied to other general relativistic systems, whether “simple" or “perturbative", beyond CCBs. This heuristic work focuses broadly on the EFEs themselves under the Laplace-Beltrami formalism, considering all differential orders up to second-order. This namely includes a deeper analysis on the variational methodology employed on the EFEs in the second-order sector, utilized in previous works, and the
benchmark analysis of the lower first- and zeroth-order terms. This all-order report utilizes representative examples and select metric Ansätze to explore the formalism's practicality and its limitations; this is shown that the first-order decomposition showcases heuristically the mechanics of vector and scalar fields upon a curved spacetime.
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High Energy Astrophysical Phenomena · Cross-listed from hep-th
Self-gravitating quantum stars with a globally relevant Bohm potential
Ilidio Lopes
The microphysics underlying non-baryonic dark matter remains unknown. I derive the two-species Schrödinger-Poisson-Yukawa system for
spin-1/2 dark-sector
fermion fields, $\psi$ (mass $m_1$) and $\chi$ (mass $m_2$), coupled through a scalar mediator of mass $m_\phi$ via a universal Yukawa coupling, within an orbital-free density-functional framework with the Kirzhnits gradient coefficient $\lambda_B=1/9$. A central result is that the Bohm potential, far from being negligible in the Thomas-
Fermi regime, contributes a species-dependent surface-energy correction analogous to the
nuclear liquid-drop model: the heavier
fermion species generates an outward
quantum-pressure wall whilst the lighter species provides an inward surface tension, with degeneracy pressure furnishing the bulk confinement. In the single-species Schrödinger-Poisson limit the ground state recovers the benchmarked invariants $M_{\mathrm{dim}}\simeq 3.883$ and $x_T\simeq 2.562$, yielding $M R_T\simeq 9.95\,\lambda_B\hbar^2/(G m_1^2)$. For polytropic index $\gamma=5/3$ the mass-radius relation satisfies $R\propto M^{-1/3}$; for $\gamma=4/3$ a limiting mass emerges above which no stable
equilibrium exists. Illustrative configurations span $M=10^{-8}$-$5\, M_\odot$, $m_1\sim 10^{-14}$-$10^{-6}\, eV$, and radii from a few~km to $\sim 10^3\, R_\odot$, with gravitational-wave contact frequencies in the Einstein
Telescope and LISA bands and microlensing signatures accessible to current surveys. The predictive
rigidity of the resulting mass-radius relation, in which the single microphysical parameter $m_1$ determines the
equilibrium radius once the total mass is specified, furnishes a reproducible, first-principles reference for constraining the dark-
fermion mass in multi-component dark sectors.
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Astrophysics of Galaxies
The First Glimpse of Water Ice Absorption Map in the Milky Way
Zhetai Cao, Biwei Jiang and Stefan Meingast
Interstellar ice plays a key role in the thermal
evolution of the interstellar medium and in astrochemical pathways, yet its large-scale distribution remains poorly constrained. We use ALLWISE and 2MASS photometry to estimate water ice absorption in the $\Wi$/WISE band by correcting the observed colors for reddening and intrinsic
stellar colors. This allows us to construct a first Milky Way water ice map. By varying input parameters, we test the stability of the method and identify the extinction law as the dominant source of uncertainty. Using synthetic photometry, we also quantify how different physical and observational parameters influence the $\Wi$ band water ice absorption. The strong correlation between the measurement from photometric method and spectroscopic water ice abundance confirms that the $\Wi$ band signature originates from the 3 $\mu$m ice feature. We present the relationship between ice absorption in $\Wi$ band and water ice optical depth from theory and observations. Finally, we provide a preliminary Milky Way-scale map of water ice distribution.
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High Energy Astrophysical Phenomena
Photon Escape from Slab Thomson Media: A Scattering-order-resolved Recursive Formalism for Comptonization Applications
Haichao Xu
The scattering history of
photons in slab media plays an important role in modelling Comptonized spectra and disc-corona radiative feedback. We develop a recursive formalism that evolves the post-scattering depth–direction distribution in slab Thomson media and yields boundary- and angle-resolved escape probabilities at each scattering order. For azimuth-integrated problems, the angular dependence closes within a two-component basis, reducing the transport problem to an efficient depth-kernel recursion. We apply the method to normally incident beam injection, Lambert-law boundary injection, and a vertically uniform isotropic internal source, and verify the results with Monte Carlo radiative-transfer simulations. The resulting distributions provide a
photon-number-conserving route to semi-analytic Comptonized spectra and estimates of the Compton amplification factor and the fraction of downwardly scattered luminosity. We also derive the mean scattering number within this framework, obtaining the exact result $\langle N\rangle=2\tau$ for Lambert-law injection, while the uniform internal source changes from an optically thin $\tau\ln(1/\tau)$ behaviour to an optically thick $\tau^2/4$ scaling. At high scattering orders, the recursion is controlled by a dominant eigenmode: $P_n/P_{n-1}\rightarrow\lambda(\tau)$, where $\lambda(\tau)$ is the spectral radius of the slab recursion operator. This eigenmode also determines a limiting normalized angular distribution, so that viewing angle and escape boundary primarily affect the normalization of the high-order X-ray component, while spectral-shape differences are mainly confined to the unscattered and low-order components. These
eigenvalue and eigenfunction results provide transport ingredients for future energy-dependent slab Comptonization models.
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High Energy Astrophysical Phenomena
Hunting for Compact Object Binaries from eRASS1 Optical Counterparts through ZTF Time-domain Photometry and Multi-wavelength Surveys
Xin-Yu Fang, Hao-Bin Liu and Wei-Min Gu
Capitalizing on the eRASS1 optical counterpart catalog, we conduct a systematic census of compact object binary (COB) candidates, with a primary focus on X-ray binaries (XRBs), by integrating ZTF time-domain photometry with multi-wavelength observations. This framework establishes two complementary pipelines, yielding two distinct source samples. The first sample consists of 151 periodically variable sources, from which a highly refined subset of 43 high-priority COB candidates is identified. The second sample comprises 1958 distance-constrained sources selected based on elevated X-ray luminosities or high $\log(F_{\mathrm{X}}/F_{\mathrm{opt}})$. Crucially, cross-matching both samples with
radio catalogs reveals seven
radio-emitting sources, highlighting four promising XRB candidates. Our results underscore that coupling eROSITA with wide-field time-domain photometric and multi-wavelength surveys offers a highly efficient strategy for uncovering the hidden population of COBs.
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High Energy Astrophysical Phenomena
Enhancing the Angular Resolution of Large Array of imaging atmospheric Cherenkov Telescope (LACT) at Ultra-High Energies
Zhipeng Zhang, Ruizhi Yang, Shoushan Zhang et al. (+5 more)
The Large Array of Imaging Atmospheric Cherenkov
Telescopes (LACT) is dedicated to high-resolution morphological studies of PeVatrons. In this work, we present a fundamental investigation into stereoscopic direction reconstruction for the LACT array, specifically addressing the challenges of ultra-high-energy observations. We demonstrate that the standard Hillas parameterization introduces a significant reconstruction bias under severe image leakage. To mitigate this, we introduce an approach utilizing a 2D Gaussian fit, achieving an exceptional angular resolution of better than $0.06^\circ$ at $100\text{ TeV}$ within the central $0^\circ\text{--}1^\circ$ offset bin, and maintaining better than $0.12^\circ$ across offsets up to $4^{\circ}$. Building on this robust baseline, we evaluate advanced weighting schemes by utilizing a LightGBM-based
quantile regression model to independently estimate single-image quality. Applying these quality-based weights yields a consistent improvement of $0.02^\circ$ to $0.03^\circ$ for high-energy, large-offset events using both the HillasWeightedSum and HillasWeightedDisp methods. Finally, to establish a theoretical performance ceiling, we explore a pixel-wise likelihood reconstruction technique utilizing Neural Ratio Estimation. While its practical realization depends heavily on minimizing the gap between Monte Carlo simulations and observational data, this exploratory approach demonstrates the potential to yield an overall improvement of approximately 15% to 40% at $100~\rm TeV$ across the entire field of view. Such high angular resolution is critical for disentangling complex emission regions and mapping the internal structures of PeVatrons.
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All authors Zhipeng Zhang, Ruizhi Yang, Shoushan Zhang, Jiali Liu, Liqiao Yin, Wedong Wang, Lingling Ma, Zhen Cao
Astrophysics of Galaxies
Understanding the Broad-line Region of Active Galactic Nuclei with Photoionization. II. Slim disks, Self-shadowing, and BLR sizes
Qiaoya Wu, Yue Shen, Chris Done et al. (+2 more)
Reverberation-mapping (RM) measurements have revealed that high-
accretion-rate active
galactic nuclei (AGNs) systematically lie below the canonical broad-line region (BLR) radius - optical continuum luminosity (R-L) relation, exhibiting shorter lags than predicted for fixed 5100Åluminosity. The physical origin of these offsets remains debated. We investigate how
accretion-flow structure and BLR cloud properties affect the emissivity-weighted BLR radius using analytic slim-disk SEDs and photoionization calculations on a two-dimensional axisymmetric grid. As the
accretion rate approaches and exceeds the Eddington limit,
geometric thickening of the inner disk produces anisotropic illumination and self-shadowing, reducing ionizing flux seen by low-latitude BLR clouds and flattening the R-L relation at high L/LEdd. Self-shadowing at high
accretion rates reproduces the observed R-L trend in the RM AGN sample reasonably well, but this effect alone is insufficient to explain the observed lag offset in low-mass ($\sim10^{7}M_\odot$) systems with high
accretion rates. Motivated by
accretion-disk density scalings, we further explore models in which the BLR gas density increases toward lower black hole mass or higher
accretion rate. We find that an
accretion-rate-dependent BLR density enhancement further improves agreement with observed RM data, where the BLR gas density increases by a factor of 3-5 for one dex increase in $\dot{m}$. Variations in BLR opening angles produce a less important effect on BLR sizes. These results demonstrate that self-consistent modeling of
accretion disk SED, BLR illumination and photoionization, and gas density variations can fully explain the observed distribution of AGNs in the BLR size - optical luminosity plane. This framework provides a physically motivated link between
accretion-flow structure and BLR observables across a broad range of black-hole properties.
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All authors Qiaoya Wu, Yue Shen, Chris Done, Michael R. Goad, Scott Hagen
Earth and Planetary Astrophysics
Photochemical CS$_2$ Gas Detected on a 20-Myr-old Exoplanet
Fei Dai, Erik Petigura, John Livingston et al. (+6 more)
Probing the atmospheres of young
exoplanets offers a powerful window into how planetary systems evolve and the physical and chemical processes that drive those early evolutions. We present JWST/NIRSpec transmission spectroscopy of V1298 Tau e, a $\sim$20-Myr-old, $\sim$15-$M_\oplus$
planet with a Jupiter-like radius orbiting a young Sun-like
star. We identified carbon disulfide (CS$_2$) in its atmosphere at $>$8$\sigma$ significance based on spectral features between 4.3 and 4.7~$\mu$m. Photochemical forward models show that the inferred CS$_2$ abundance is physically plausible in an H/He-dominated atmosphere exposed to intense ultraviolet irradiation. The atmosphere of V1298 Tau e is strikingly different from its nearest neighboring
planet b, whose atmosphere shows SO$_2$ rather than CS$_2$. These observations demonstrate that even
planets within the same system can occupy distinct photochemical regimes. Our results further provide empirical evidence for complex sulfur photochemistry in
exoplanet atmospheres in general and may also point to divergent formation or evolutionary pathways within the same planetary system.
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All authors Fei Dai, Erik Petigura, John Livingston, Nicholas Wogan, Sagnick Mukherjee, Zhecheng Hu, Ian J. M. Crossfield, James Owen, Kento Masuda
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
A quarkyonic matter model
Toru Kojo
Quarkyonic matter is a state of matter in dense QCD whose bulk thermodynamics is dominated by
quarks, while low-energy excitations remain confined. This picture leads to a crossover description from baryonic matter to
quark matter, which is triggered by the saturation of
quark states in dense matter (
quark saturation). The crossover driven by the
quark saturation accompanies rapid growth in pressure but moderate increase in energy density, resulting in a peak in the sound speed which has been indicated by observational constraints from
neutron star physics. The
quark saturation can occur at a few times
nuclear saturation density, which is smaller than the density at which the
baryon cores of $\sim 0.5$–$0.8$ fm spatially overlap. In this contribution we discuss an ideal model of quarkyonic matter, the IdylliQ model, and we explicitly describe how the
baryon and
quark occupation probabilities are related, and explain how stiffening of matter occurs. The model is further applied to charge neutral matter including hyperons, and it is shown that the statistical constraints at
quark level induce effective repulsion among different
baryon species, mitigating the hyperon softening problem in
neutron star physics.
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