Instrumentation and Methods for Astrophysics
A Classic Nonlinearity Correction Algorithm for Detectors Read Out Up-The-Ramp
Timothy D. Brandt
We derive an
algorithm for computing a classic nonlinearity correction – applicable to constant and uniform illumination – in the presence of read noise and
photon noise. The
algorithm operates simultaneously on many nondestructive ramps at a range of count rates and directly computes the function transforming measured counts into linearized counts. We also compute chi squared for the corrected ramps, enabling the user to identify the
polynomial degree beyond which chi squared ceases to improve significantly. The computational cost of our
algorithm is linear in the number of reads and ramps, reaching ~100 hours to derive a correction for all 4096 x 4096 pixels of a Hawaii-4 RG detector from 186 illuminated 55-read ramps on a 2023 Macbook Pro laptop (~10,000 reads per pixel). We identify a potential source of bias in the nonlinearity correction when combining ramps of very different illuminations, together with effective mitigations. We apply our
algorithm to a random set of pixels from the Roman Space
Telescope's Wide Field Instrument. We find that a >=9th order nonlinearity correction is needed, at which point chi squared is close to its theoretically expected value and beyond which chi squared improves little with increasing
polynomial order. Python software implementing our
algorithm is available at https://github.com/RomanSpaceTelescope/SOCReferenceFileCode.
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Instrumentation and Methods for Astrophysics
Computing the Electronic Gain for Detectors Read Out Up-The-Ramp
Timothy D. Brandt
The electronic gain – the conversion between photoelectrons on a pixel and the digital number recorded to disk – gives physical units to an astronomical image and sets the relation between pixel value and
photon noise. This paper presents a new, likelihood-based approach to derive the gain from images taken up-the-ramp, where the detector is read out nondestructively many times before being reset. Our method makes full use of the individual reads assuming an ideal detector subject to
photon noise and Gaussian read noise. We extend the method to account for slight nonlinearities in the relation between photoelectrons and measured counts. We demonstrate that our likelihood-based approach provides a consistent (i.e. asymptotically correct) and nearly unbiased
estimator of the gain both with and without fitting for nonlinearity. Finally, we apply this approach to a single detector from the Wide-Field Instrument on the Roman Space
Telescope, and show how pixel-to-pixel gain variations describe much of the variations in pixel response seen in flatfield images. Code to compute gain and regenerate figures in this paper is available at https://github.com/RomanSpaceTelescope/SOCReferenceFileCode.
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Earth and Planetary Astrophysics
Metrics for Optimizing Searches for Orbital Precession and Tidal Decay via Transit- and Occultation-Timing
Brian Jackson, Elisabeth R. Adams, Rachel M. Huchmala et al. (+4 more)
Short-period
exoplanets may exhibit orbital precession driven by several different processes, including
tidal interactions with their host
stars and secular interactions with additional
planets. This motion manifests as periodic shifts in the timing between transits which may be detectable via high-precision and long-baseline transit- and occultation-timing measurements. Detecting precession and attributing it to a particular process may constrain the
tidal responses of
planets and point to the presence of otherwise undetected perturbers. However, over relatively short timescales, orbital decay driven by the same
tidal interactions can induce transit-timing signals similar to the precession signal, and distinguishing between the two processes requires robust assessment of the model statistics. In this context, occultation observations can help distinguish the two signals, but determining the precision and scheduling of observations sufficient to meaningfully contribute can be complicated. In this study, we expand on earlier work focused on searches for
tidal decay to map out simple metrics that facilitate detection of precession and how to distinguish it from
tidal decay. We discuss properties for a short-period
exoplanet system that can maximize the likelihood for detecting such signals and prospects for contributions from citizen-science observations.
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All authors Brian Jackson, Elisabeth R. Adams, Rachel M. Huchmala, Malia Barker, Marvin Rothmeier, Jeffrey P. Morgenthaler, Amanda A. Sickafoose
Solar and Stellar Astrophysics
Distance to the Globular Cluster M 3 from the Infrared Surface Brightness Technique applied to RR Lyrae stars
Bartłomiej Zgirski, Wolfgang Gieren, Grzegorz Pietrzyński et al. (+10 more)
The Infrared Surface Brightness (IRSB) technique is a specific application of the Baade-Wesselink method. Given a proper calibration, well covered optical and near-infrared photometry, as well as radial velocity curves, it allows for estimation of distances to individual pulsating
stars and determination of their mean radii. The technique is fully empirical and does not depend on
stellar atmosphere models. The goal of the work is to test the precision of distance determinations to individual RR Lyrae
stars and to their host system as a whole using the IRSB technique for a relatively distant globular cluster M 3 (NGC 5272). We also aim to determine mean radii and period-radius relations for these
stars in order to compare them with the existing theoretical prediction and empirical estimations for the field
stars from the
solar neighborhood. We use data available in the literature and the calibration of the IRSB technique based on the RR Lyrae
stars from the
solar neighborhood we published previously in order to determine distances to 14 RR Lyrae
stars in the globular cluster M 3. We study the impact of the selection of the fitting procedure (bisector v.s. the LS fit) on the results. We apply five different empirical surface brightness-color relations from the literature in the analysis. We obtained a mean distance to M 3 of $r_{M3} = (10.07 \pm 0.19 \pm 0.29) \,kpc$ that corresponds to a distance modulus ${\mu}_{M3} = (15.015 \pm 0.041 \pm 0.063) \,mag$ and a $7\%$ scatter of individual
stellar distances for 14 RR Lyrae
stars in M 3. We received a very good agreement between the two fitting techniques. We also determined mean
stellar radii for pulsators from the sample with a precision of $0.5\%$ and obtained excellent agreement with a theoretical prediction of the period-radius relation for RRab
stars available in the literature.
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All authors Bartłomiej Zgirski, Wolfgang Gieren, Grzegorz Pietrzyński, Gergely Hajdu, Piotr Wielgórski, Marek Górski, Jesper Storm, Nicolas Nardetto, Alexandre Gallenne, Garance Bras, Pierre Kervella, Paulina Karczmarek, Weronika Narloch
Instrumentation and Methods for Astrophysics · Cross-listed from math.NA
High Order Numerical Methods Preserving Invariant Domain for Hyperbolic and Related Systems
Kailiang Wu, Xiangxiong Zhang and Chi-Wang Shu
Admissible states in
hyperbolic systems and related equations often form a convex invariant domain. Numerical violations of this domain can lead to loss of hyperbolicity, resulting in illposedness and severe numerical instabilities. It is therefore crucial for numerical schemes to preserve the invariant domain to ensure both physically meaningful solutions and robust computations. For complex systems, constructing invariant-domain-preserving (IDP) schemes is highly nontrivial and particularly challenging for high-order accurate methods. This paper presents a comprehensive survey of IDP schemes for
hyperbolic and related systems, with a focus on the most popular approaches for constructing provable IDP schemes. We first give a systematic review of the fundamental approaches for establishing the IDP property in first-order accurate schemes, covering finite difference, finite volume, finite element, and residual distribution methods. Then we focus on two widely used and actively developed classes of high order IDP schemes as well as their recent developments, most of which have emerged in the past decade. The first class of methods seeks an intrinsic weak IDP property in high-order schemes and then designs
polynomial limiters to enforce a strong IDP property at the points of interest. This generic approach applies to high-order finite volume and discontinuousGalerkin schemes. The second class is based on the flux limiting approaches, which originated from the flux-corrected transport method and can be adapted to a broader range of spatial discretizations, including finite difference and continuous finite element methods. In this survey, we elucidate the main ideas in the construction of IDP schemes, provide some new perspectives and insights, with extensive examples, and numerical experiments in gas dynamics and magnetohydrodynamics.
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Astrophysics of Galaxies
High deuteration of methanol in L1544
S. Spezzano, W. Riedel, P. Caselli et al. (+7 more)
Isotopic fractionation is a very powerful tool to follow the
evolution of material from one stage to the next in the
star-formation process. Pre-
stellar cores exhibit some of the highest levels of deuteration because their physical conditions greatly favor deuteration processes. Deuteration maps are a measure of the effectiveness of the deuteration across the core, and they are useful to study both the deuteration as well as the formation mechanism of the main species. Methanol is the simplest O-bearing complex organic molecule (COM) detected in the interstellar medium (ISM). It represents the beginning of molecular complexity in
star-forming regions, thus a complete understanding of its formation and deuteration is a necessary step to understand the development of further chemical complexity. In this paper, we use single-dish observations with the IRAM 30 m
telescope and state-of-the-art chemical models to investigate the deuteration of methanol towards the prototypical pre-
stellar core L1544. We also compare the results of the chemical models with previous observations of deuterated methanol towards the pre-
stellar cores HMM1 and L694-2. The spectra extracted from the CHD$_2$OH map show that the emission is concentrated in the center and towards the north-west of the core. Using deep observations towards the
dust and the methanol peaks of the core, we derive a very large deuterium fraction for methanol ($\sim20\%$) towards both peaks. The comparison of our observational results with chemical models has highlighted the importance of H-abstraction processes in the formation and deuteration of methanol. Deep observations combined with state-of-the-art chemical models are of fundamental importance in understanding the development of molecular complexity in the ISM. Our analysis also shows the importance of non-LTE effects when measuring the D/H ratios in methanol.
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All authors S. Spezzano, W. Riedel, P. Caselli, O. Sipilä, Y. Lin, H. A. Bunn, E. Redaelli, L. H. Coudert, A. Megías, I. Jimenez-Serra
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Curvaton-assisted hilltop inflation
Wen-Yuan Ai, Stephen F. King, Xin Wang et al. (+1 more)
Following the recent Atacama Cosmology
Telescope (ACT) results, we consider hilltop inflation where the inflaton is coupled to a curvaton, simultaneously addressing two main challenges faced by conventional hilltop inflation models: the initial-value problem; and their viability for sub-Planckian field values. In standard single-field hilltop inflation, the inflaton must start extremely close to the maximum of the potential, raising concerns about the naturalness of the initial conditions. We demonstrate that the curvaton field not only significantly relaxes the initial-value tuning required for hilltop inflation, but also opens up parameter space through modifying the
curvature perturbation power spectrum, reviving the quartic hilltop inflation model in the sub-Planckian regime. We find viable parameter space consistent with the recent cosmological observations.
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All authors Wen-Yuan Ai, Stephen F. King, Xin Wang, Ye-Ling Zhou
Astrophysics of Galaxies
On the connection between galaxy orientation and halo absorption properties
Rohan Venkat, Soo May Wee and Hsiao-Wen Chen
We present a systematic investigation of the azimuthal dependence of metal-line absorption in the circumgalactic medium (CGM) using a uniformly selected sample of 87 isolated
galaxies at z < 0.4 from the Magellan MagE MgII (M3)
halo survey. High-quality archival imaging enables quantitative morphological measurements – including disk inclination and position angle – for every
galaxy, providing a robust framework for assessing how absorber strength depends on the
geometric alignment between
galaxies and the QSO sightlines. All
galaxies have associated constraints on MgII lambda 2796 absorption, and a subset of 56
galaxies also have measurements of CaII lambda 3934. We compare rest-frame MgII and CaII equivalent widths with both projected distance and deprojected galactocentric distance. Across the full sample, we find no statistically significant correlation between absorption strength and azimuthal angle. Restricting to the 71
galaxies with well-determined disk orientations reveals an apparent excess of strong MgII absorbers near the projected major axis, but a Kendall's tau test confirms that this trend is not statistically significant. CaII absorption, which exhibits a low covering fraction of kappa_CaII = 0.18^{+0.06}_{-0.04} within 50 kpc for W_r(3934) > 0.1 Ang, shows no measurable azimuthal dependence. To assess potential biases, we quantify the effects of projection, disk inclination, and variations in imaging quality. After accounting for these systematics, the spatial distribution of low-
redshift MgII and CaII absorbers is consistent with arising from a randomly distributed population, with no compelling evidence for azimuthal anisotropy at d <~ 50 kpc. A larger sample with robust constraints on the disk orientation will be required to uncover or rule out subtle anisotropic trends.
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High Energy Astrophysical Phenomena
Characterising the X-ray variability of QSOs to the highest Eddington ratios and black hole masses with eROSITA light curves
Antonis Georgakakis, Angel Ruiz, Johannes Buchner et al. (+9 more)
An important diagnostic of the inner structure of
accretion flows onto supermassive black holes are the
stochastic flux variations at X-ray wavelengths. Despite its significance, a systematic characterisation of the statistical properties of the X-ray variability to the highest Eddington ratios and most massive black holes is still lacking. In this paper we address this issue using SRG/eROSITA 5-epoch light curves to characterise the mean X-ray variability of optically selected SDSS QSOs extending to black holes masses of $10^{10}$
solar and
accretion rates close to the Eddington limit. The adopted variability statistic is the ensemble normalised excess variance, which is measured using a novel hierarchical
Bayesian model (eBExVar) tailored to the Poisson nature of the X-ray light curves. We find a clear anti-correlation of the ensemble variability with black hole mass, extending previous results to time scales of months. This can be interpreted as evidence for an X-ray corona size and/or physical conditions that scale with black holes mass. We also find an unexpected increase of the ensemble normalised excess variance close to the Eddington limit, which is contrary to the predictions of empirical variability models. This result suggests an additional variability component for fast growing black holes that may be related to systematic variations of the hot corona size with Eddington ratio or shielding of the hot corona by an inner puffed-up disk and/or
outflows.
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All authors Antonis Georgakakis, Angel Ruiz, Johannes Buchner, Iossif Papadakis, Maria Chira, Kirpal Nandra, Shi-Jiang Chen, Maurizio Paolillo, Qingling Ni, Mara Salvato, Thomas Boller, Andrea Merloni
High Energy Astrophysical Phenomena
Probing the origin of the kilonova candidate GRB 230307A: analysis of host galaxy and offset
Clecio R. Bom, Davi C. Rodrigues, Arianna Cortesi et al. (+12 more)
We investigate the host
galaxy of the long gamma-ray burst GRB 230307A, which is associated with a kilonova candidate likely produced by a binary
neutron-
star (BNS) merger. The transient occurred at a projected offset of ~40 kpc from its host. We consider two explanations for this large distance: (i) NSs that merge inside a remote globular cluster, or (ii) a BNS that formed in the disk whose orbit was strongly modified by the NS natal kicks. Using JWST data and comparisons with known globular clusters, we show that a globular-cluster origin is unlikely. Using JWST and MUSE data, we derive the host
galaxy morphology,
stellar mass, estimate the atomic gas (HI+He) contribution, and the host rotation curve. Assuming an NFW
halo and applying
Bayesian inference, we obtain a mass model for the host. From this model, we compute the time required for a disk-formed BNS, with a given natal kick, to reach the observed offset while marginalizing over uncertainties and over the initial position in the disk. We compare these results with BNS-merger simulations from a population-synthesis code combined with
stellar evolutionary tracks, which provide the coalescence time and kick velocity for each realization. The two approaches have an overlap in the kick-time diagram, but only 0.1% of the simulated systems is compatible with the
galaxy-mass model. This indicates that a disk origin is possible, but requires fine-tuned conditions for the kilonova to occur at such a large distance from the host
galaxy.
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All authors Clecio R. Bom, Davi C. Rodrigues, Arianna Cortesi, Amanda E. Araujo-Carvalho, Daniel Ruschel-Dutra, Giuliano Iorio, Luidhy Santana-Silva, Charles D. Kilpatrick, Fabricio Ferrari, Luis Lomeli-Nuñez, Thomas Harvey, Duncan Austin, Christopher J. Conselice, Nathan Adams, Roberto Cid Fernandes
Astrophysics of Galaxies
A High-resolution Study of the Cold Neutral Medium in and around 30 Doradus
Gyueun Park, Min-Young Lee, John M. Dickey et al. (+17 more)
With the aim of evaluating the roles of the cold neutral medium (CNM) in the cloud-scale
baryon cycle, we perform a high-resolution study of the CNM in and around the extreme
star-forming region 30 Doradus (30 Dor). For our study, we use
Galactic Australian Square Kilometre Array Pathfinder H I Survey data and produce H I emission and absorption cubes on 7 pc scales. To examine the CNM structures toward 30 Dor, we decompose the H I absorption cube into 862 Gaussian components and find that these components are distributed at four velocity ranges (B1, B2, B3, and B4, respectively): 200$-$230 km s$^{-1}$, 230$-$260 km s$^{-1}$, 260$-$277 km s$^{-1}$, and 277$-$300 km s$^{-1}$. We derive line-of-sight average
spin temperatures and opacity-corrected total H I column densities and show that the B1$-$B4 structures have systematically different properties, indicating that they are physically distinct. As for the nature of the observed CNM structures, we find that B2 is associated with the main dense structure where ionized, atomic, and molecular gases are concentrated. B3 and B4 trace inflows whose combined mass flux rate of 0.14 $M_{\odot}$ yr$^{-1}$ is comparable to the current
star formation rate, while B1 probes
outflows with a much lower mass flux rate of 0.007 $M_{\odot}$ yr$^{-1}$. Interestingly, the H I column densities in B1$-$B4 are nearly uniform with a factor of two spatial variations, implying the presence of H I shielding layers for H$_{2}$ formation.
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All authors Gyueun Park, Min-Young Lee, John M. Dickey, Nick M. Pingel, James Dempsey, Helga Dénes, Steven Gibson, Katie Jameson, Ian Kemp, Chang-Goo Kim, Denis Leahy, Bumhyun Lee, Callum Lynn, Yik Ki Ma, Antoine Marchal, Naomi M. McClure-Griffiths, Eric Muller, Hiep Nguyen, Snežana Stanimirović, Jacco Th. Van Loon
Astrophysics of Galaxies
Optimizing Photometric Redshift Training Sets I: Efficient Compression of the Galaxy Color-Redshift Relation with UMAP
Finian Ashmead, Jeffrey A. Newman, Brett H. Andrews et al. (+4 more)
Spectroscopic
datasets are essential for training and calibrating photometric
redshift (photo-$z$) methods. However, spectroscopic
redshifts (spec-$z$'s) constitute a biased and sparse sampling of the photometric
galaxy population, which creates difficulties for the common grid-based approach for mapping color to
redshift using self-organizing maps (SOMs). Instead, we utilized the uniform
manifold approximation and projection (UMAP)
algorithm to compress a Rubin–Roman-like $ugrizyJH$ color space into a thin and densely-sampled
manifold. Crucially, the
manifold varies continuously and monotonically in
redshift and specific
star formation rate in roughly orthogonal directions. Using COSMOS2020 many-band photo-$z$'s and compiled spec-$z$'s as representative and non-representative samples, respectively, we trained and tested
redshift prediction from a SOM, from nearest neighbors in UMAP coordinates (UMAP-$k$NN-$z$), and directly from nearest neighbors in the color space to assess how well location in each space maps to
redshift. For the representative training set, UMAP-$k$NN-$z$ exhibited smaller photo-$z$ scatter and fraction of outliers than SOM-based methods. When training with the highly-biased spec-$z$ sample, UMAP-$k$NN-$z$ maintained similar performance while SOM- and color-based methods predictions were significantly degraded, especially at $z>1.5$ where training sets are the most sparse. The physically-meaningful trends across the UMAP
manifold allow for accurate
redshift prediction even in such poorly-sampled regions of color space. This suggests that representative, spectroscopically-anchored training sets can be produced by interpolating between spectroscopic sources at the UMAP coordinates of photometric objects, maximizing the performance of photo-$z$
algorithms.
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All authors Finian Ashmead, Jeffrey A. Newman, Brett H. Andrews, Rachel Bezanson, Biprateep Dey, Daniel C. Masters, S.A. Stanford
Astrophysics of Galaxies
Core-wing transitions and the breakdown of diffusion in Lyman-$\alpha$ radiative transfer
Kevin Lorinc, Aaron Smith, Olof Nebrin et al. (+1 more)
The Lyman alpha (LyA) line of neutral hydrogen plays a central role in observations of
star-forming
galaxies. However, resonant scattering makes it difficult to directly interpret LyA signatures. Monte Carlo radiative transfer (MCRT) calculations have become the gold standard for modeling LyA, but it becomes extremely computationally expensive in optically thick environments. Workarounds, such as core-skipping to avoid repetitive low-transport scatterings, greatly increase the efficiency of MCRT simulations but introduce errors in the solutions. While core-skipping is designed to preserve emergent spectra, the internal radiation field, most importantly, the momentum imparted, is not properly preserved. On the other hand, to make analytical and numerical progress, it is often assumed that
photons diffuse in both frequency and physical space. We find that these
diffusion approximations break down for frequencies near the core and positions at finite optical depths. We propose a more physically-motivated definition for the core-wing transition frequency to isolate such effects. We derive new spectral distributions of internal radiation properties and compare the results with simulations. We analyze the diffusive properties of LyA
photons and demonstrate anomalous spatial
diffusion behavior with fat-tailed distributions. This work deepens our understanding of
diffusion in resonant-line transfer and identifies areas where simulations or analytics may be failing and how these failures may be resolved.
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All authors Kevin Lorinc, Aaron Smith, Olof Nebrin, Joshua Kasiri
Astrophysics of Galaxies
Enhanced rates of stellar radial migration in gas-rich discs at high redshift
HanYuan Zhang, Thor Tepper-García, Vasily Belokurov et al. (+6 more)
Radial migration and dynamical heating redistribute
stars within
galactic discs and thereby modify the chemo-kinematic structure of their host
galaxies. Usually, these secular processes are studied in N-body and hydrodynamical simulations of Milky Way analogues with
stellar-dominated discs. In contrast, discs at high
redshift are gas-rich, which may qualitatively change how secular
evolution proceeds. We use the Nexus framework to construct and evolve a suite of isolated
galaxies with fixed
halo and disc mass but varying initial disc gas fraction, from 0% to 100%. We show that in gas-rich models, the root-mean-square change in
stellar angular momentum is up to a factor of two larger than in gas-poor analogues and is accompanied by stronger radial and vertical heating, leading to enhanced radial mixing. We further dissect the role of gas in specific migration channels. For bar-driven migration, corotation resonance dragging dominates in gas-poor discs, whereas in gas-rich discs,
stars more readily reach and accumulate at the outer Lindblad resonance, which acts as a barrier. The high radial mixing efficiency in gas-rich phases can flatten the
stellar metallicity gradient relative to that of the initial gaseous disc within only a few orbital timescales. Together, these results imply that radial mixing in early, gas-rich discs is substantially more vigorous than in late-time, gas-poor discs, naturally producing distinct evolutionary tracks for chemically bimodal discs such as that of the Milky Way.
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All authors HanYuan Zhang, Thor Tepper-García, Vasily Belokurov, N. Wyn Evans, Takafumi Tsukui, Hillary Davis, Joss Bland-Hawthorn, Jason L. Sanders, Oscar Agertz
High Energy Astrophysical Phenomena
Non-Equilibrium Thermodynamics of Black-Hole Coronae: QPOs, Turbulence, and Jets
Vanessa López-Barquero, Alejandro Jenkins, Christopher S. Reynolds et al. (+1 more)
The variability of X-rays observed from accreting black hole systems, including quasi-periodic oscillations (QPOs), suggests a complex nonlinear dynamics in the corona. Here, we propose a new theoretical framework for this variability, based on non-
equilibrium thermodynamics. In this model, coronal variability arises from feedback between a macroscopic oscillation of the
plasma and the rate at which it is cooled by the inverse Compton scattering of soft
photons from the disc. The "pair thermostat” mechanism then allows the corona to act as a heat engine that extracts work cyclically from the underlying thermal disequilibrium between the low-
entropy heating from the black hole and the high-
entropy cooling by soft
photons from the disk, in close analogy to the well-known $\kappa$-mechanism for pulsating
stars. This coronal self-oscillation may explain QPOs without invoking an external periodic driving. Moreover, we argue that this mechanism can generate coronal
turbulence and jets.
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All authors Vanessa López-Barquero, Alejandro Jenkins, Christopher S. Reynolds, Andrew Fabian
Cosmology and Nongalactic Astrophysics
The eventful life journey of galaxy clusters. II. Impact of mass accretion on the thermodynamical structure of the ICM
David Vallés-Pérez, Susana Planelles and Vicent Quilis
Context. The internal structure of the intracluster medium (ICM) is tightly linked to the assembly history and physical processes in groups and clusters, but the role of recent
accretion in shaping these profiles has not been fully explored. Aims. We investigate to what extent mass
accretion accounts for the variability in ICM density and thermodynamic profiles, and what can present-day structures reveal about their formation histories. Methods. We analyze a hydrodynamical cosmological simulation including gas cooling but no feedback, to isolate the effects of heating from structure formation. Median profiles of ICM quantities are introduced as a robust description of the bulk ICM. We then examine correlations between mass
accretion rates or assembly indicators with the profiles of temperature,
entropy, pressure, gas and dark-matter density, as well as their scatter. Results.
Accretion in the last dynamical time strongly lowers central gas densities, while leaving dark matter largely unaffected, producing a distinct signature in the
baryon depletion function. Pressure and
entropy show the clearest dependence on
accretion, whereas temperature is less sensitive. The radii of steepest
entropy, temperature, and pressure shift inward by $\sim (10-20)\%$ between high- and low-
accretion subsamples. Assembly-state indicators are also related to the location of these features, and
accretion correlates with the parameters of common fitting functions for density, pressure, and
entropy. Conclusions. Recent
accretion leaves measurable imprints on the ICM structure, highlighting the potential of thermodynamic profiles as diagnostics of cluster growth history.
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Astrophysics of Galaxies
GA-NIFS: Understanding the ionization nature of EGSY8p7/CEERS-1019. Evidence for a star formation-driven outflow at z = 8.6
Sandra Zamora, Stefano Carniani, Elena Bertola et al. (+16 more)
Understanding the physical conditions and feedback mechanisms in early massive
galaxies is essential to uncover how they formed and evolved during the first billion years of the Universe. In this context, the
galaxy EGSY8p7/CEERS-1019 at z=8.6 provides an excellent
benchmark, given its
stellar mass of $10^{9.3}M_\odot$ and elevated N/O abundance despite its sub-
solar metallicity. In this study, we present new JWST/NIRSpec observations offering the first spatially resolved spectroscopy of this
galaxy, with higher sensitivity and spectral resolution than previous studies. We identify broad (FWHM=650km/s) H$\beta$ and [OIII] emission components whose emission is located between the two rest-frame UV clumps of the
galaxy and extended over a distance of $\sim1kpc$. The morphology and kinematics of these components indicate that the broad emission arises from outflowing gas rather than from an AGN broad-line region. The kinetic energy injection rate from
stellar feedback is an order of magnitude higher than that of the
outflow, while the radiation pressure rate is comparable to the
outflow momentum rate. These results suggest that
stellar feedback alone can drive the
outflow, with radiation pressure potentially providing the required momentum transfer. We derive a low mass-loading factor ($\eta=0.16$) and ionizing
photon escape fraction ($f_{esc}=0.021\pm0.014$). Together with the high electron density measured ($n_e=2200cm^{-3}$), these results support the interpretation that most of the gas remains confined within the
galaxy. Comparisons of diagnostic emission-line ratios with photoionization and shock models support a
star-formation-driven ionization scenario, ruling out any excitation by AGN radiation. Finally, the absence of detectable Wolf-Rayet features suggests that alternative mechanisms must be considered to explain the high N/O ratio in this
galaxy.
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All authors Sandra Zamora, Stefano Carniani, Elena Bertola, Eleonora Parlanti, Pablo G. Pérez-González, Santiago Arribas, Torsten Böker, Andrew J. Bunker, Francesco D'Eugenio, Roberto Maiolino, Michele Perna, Bruno Rodríguez Del Pino, Hannah Übler, Giovanni Cresci, Gareth C. Jones, Isabella Lamperti, Jan Scholtz, Bartolomeo Trefoloni, Giacomo Venturi
Astrophysics of Galaxies
Interpretable machine learning of halo gas density profiles: a sensitivity analysis of cosmological hydrodynamical simulations
Daniele Sorini, Sownak Bose, Mathilda Denison et al. (+1 more)
Stellar and AGN-driven feedback processes affect the distribution of gas on a wide range of scales, from within
galaxies well into the intergalactic medium. Yet, it remains unclear how feedback, through its connection to key
galaxy properties, shapes the radial gas density profile in the host
halo. We tackle this question using suites of the EAGLE, IllustrisTNG, and Simba cosmological hydrodynamical simulations, which span a variety of feedback models. We develop a random forest
algorithm that predicts the radial gas density profile within
haloes from the total
halo mass and five global properties of the central
galaxy: gas and
stellar mass;
star formation rate; mass and
accretion rate of the central black hole (BH). The
algorithm reproduces the simulated gas density profiles with an average accuracy of $\sim$83-90% over the
halo mass range $10^{9.5} \, \mathrm{M}_{\odot} < M_{\rm 200c} < 10^{15} \, \mathrm{M}_{\odot}$ and
redshift interval $0<z<4$. For the first time, we apply Sobol statistical sensitivity analysis to full cosmological hydrodynamical simulations, quantifying how each feature affects the gas density as a function of distance from the
halo centre. Across all simulations and
redshifts, the total
halo mass and the gas mass of the central
galaxy are the most strongly tied to the
halo gas distribution, while
stellar and BH properties are generally less informative. The exact relative importance of the different features depends on the feedback scenario and
redshift. Our framework can be readily embedded in semi-analytic models of
galaxy formation to incorporate
halo gas density profiles consistent with different hydrodynamical simulations. Our work also provides a proof of concept for constraining feedback models with future observations of
galaxy properties and of the surrounding gas distribution.
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All authors Daniele Sorini, Sownak Bose, Mathilda Denison, Romeel Davé
Earth and Planetary Astrophysics
University of Hawaii 88-inch Telescope Observations of the Interstellar Comet 3I/ATLAS: Spectrophotometric Blue-Sensitive Spectral Time Series Spanning Two Months from Discovery
W. B. Hoogendam, D. Kuesters, B. J. Shappee et al. (+22 more)
Interstellar objects are the ejected building blocks of other
solar systems. As such, they enable the acquisition of otherwise inaccessible information about nascent extrasolar systems. The discovery of the third interstellar object, 3I/ATLAS, provides an opportunity to explore the properties of a small body from another
solar system and to compare it to the small bodies in our own. To that end, we present spectrophotometric observations of 3I/ATLAS taken using the
SuperNova Integral Field Spectrograph on the University of Hawaii 2.2-m
telescope. Our data includes the earliest $\lambda\leq3800$ A spectrum of 3I/ATLAS, obtained $\sim$12.5 hours after the discovery announcement. Later spectra confirm previously reported cometary activity, including Ni and CN emission. The data show wavelength-varying spectral slopes ($S\approx($0%-29%)/1000 A, depending on wavelength range) throughout the pre-perihelion ($r_h=4.4$-$2.5$ au) approach of 3I/ATLAS. We perform synthetic photometry on our spectra and find 3I/ATLAS shows mostly stable color
evolution over the period of our observations, with $g-r$ colors ranging from $\sim$0.69-0.75 mag, $r-i$ colors ranging from $\sim$0.26-0.30 mag, and $c-o$ colors ranging from $\sim$0.50-0.55 mag. Ongoing post-perihelion observations of 3I/ATLAS will provide further insight into its potentially extreme composition.
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All authors W. B. Hoogendam, D. Kuesters, B. J. Shappee, G. Aldering, J. J. Wray, B. Yang, K. J. Meech, M. A. Tucker, M. E. Huber, K. Auchettl, C. R. Angus, D. D. Desai, J. T. Hinkle, J. Kiyokawa, G. S. H. Paek, S. Romagnoli, J. Shi, A. Syncatto, C. Ashall, M. Dixon, K. Hart, A. M. Hoffman, D. O. Jones, K. Medler, C. Pfeffer
Astrophysics of Galaxies · Cross-listed from hep-ph
Search for Dark Matter Annihilation and Decay with H$\alpha$ Line Emission
Rebecca K. Leane
I present a new indirect search for dark matter (DM) using Hydrogen-$\alpha$ (H$\alpha$) recombination emission. DM annihilation or decay products can ionize neutral gas; subsequent recombination cascades generate H$\alpha$
photons through the $3\rightarrow2$ transition. In quiet gas-rich
dwarf galaxies, the $n{=}2$ population is negligible, so H$\alpha$ is effectively unabsorbed and traces the DM-energy injection site. Using the non-detection of extended H$\alpha$ emission in the Leo T
dwarf galaxy with Multi Unit Spectroscopic Explorer (MUSE) observations, I derive the first H$\alpha$-based limits on DM annihilation and decay, reaching leading sensitivity for parts of the eV-GeV mass range. Existing and upcoming
telescopes can further extend this reach, establishing H$\alpha$ imaging as a powerful DM search strategy.
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High Energy Astrophysical Phenomena
Viscously Spreading Accretion Disks around Black Holes: Implications for TDEs, LFBOTs and other Transients
Mila Winter-Granic and Eliot Quataert
We present a simple time-dependent model of viscously spreading
accretion disks around black holes (BHs) with masses between $10-10^8M_\odot$. We apply the results to observations of late-time emission in
tidal disruption events (TDEs) and luminous fast blue optical transients (LFBOT) such as AT2018cow. Our model generalizes previous work by incorporating
outflows during super-Eddington
accretion, non-conservation of mass and angular momentum in TDE circularization, irradiation of the outer disk by the inner
accretion flow, and a range of viscous stress models. We show that many late-time plateaus in TDEs can be explained by disks formed with a large spread in angular momentum due to redistribution during circularization. Viscous spreading on year timescales is not required, although it is also compatible with the data. The collapse of radiation pressure dominated thin disks to the stable gas-pressure dominated phase greatly underpredicts TDE plateau luminosities, strongly favoring thermally stable magnetically dominated disk models. Irradiation of the outer disk in TDEs due to misalignment of the
stellar orbit and black hole
spin increases plateau luminosities and durations by factors of a few. Continued study of late-time TDE emission provides a unique opportunity to constrain the physics of disk formation and circularization, disk warps, angular momentum transport, and other poorly understood aspects of disk physics. The models we develop can also explain the late-time optical-UV emission in the LFBOT AT2018cow for BH masses of ~$10-100M_\odot$. The faint X-ray emission at late times in AT2018cow is likely due to ongoing absorption. Our models predict that late-time X-rays should eventually be detectable again, and that HST/JWST observations of AT2018cow may detect a break in the SED at near-IR-optical wavelengths, providing a powerful probe of outer
accretion disk thermodynamics.
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Astrophysics of Galaxies
Kinematics and physical structure of Ou 5: A bipolar planetary nebula with extreme abundance discrepancy and an eclipsing binary core
William J. Henney, J. A. López, Ma. T. García-Díaz et al. (+5 more)
We present new deep imaging and high-resolution spectroscopy of the extreme-abundance-discrepancy planetary nebula Ou 5, together with photoionization modelling aimed at probing its unusual thermal and chemical structure. The nebula exhibits a nested bipolar morphology, including inner and outer shells, faint outer lobes, and polar
knots. Remarkably, all these components share a dynamical age of order 10,000 yr. Thermal broadening of the H alpha line relative to heavier ions implies a hydrogen temperature 3000 K to 6000 K, in contrast to the ~ 10,000 K derived from collisionally excited line diagnostics. This provides independent support for the presence of at least two distinct temperature/
metallicity phases, as previously proposed to explain extreme abundance discrepancies. Photoionization models with sinusoidally varying
metallicity successfully reproduce the observed nebular spectrum and morphology. A mixture of fluctuations with both extreme and moderate
metallicity contrasts is required to simultaneously fit the O II and the [O III] observations. The nebular He II emission demands a hotter and more luminous central
star than previously inferred, consistent with a ~ 0.58
solar mass post-AGB progenitor evolving toward a CO white
dwarf. Ou 5 thus reinforces the link between close-binary
nuclei and extreme abundance discrepancies, and provides a valuable
benchmark for understanding how common-envelope ejections give rise to the thermal and abundance inhomogeneities observed in planetary nebulae.
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All authors William J. Henney, J. A. López, Ma. T. García-Díaz, M. G. Richer, D. H. González-Buitrago, S. V. Zharikov, S. Noroozi, F. Pozo Nuñez
Earth and Planetary Astrophysics
Hot Jupiters are Inflated Primarily by Shallow Heating
Stephen P. Schmidt, Daniel P. Thorngren and Kevin C. Schlaufman
The unexpectedly large radii of transiting hot Jupiters have led to many proposals for the physical mechanisms responsible for heating their interiors. While it has been shown that hot Jupiters reinflate as their host
stars brighten due to heating deep in planetary interiors, young hot Jupiters also exhibit signs of delayed cooling possibly related to heating closer to their surfaces. To investigate this ambiguity, we enhance our previously published hot Jupiter thermal
evolution model by adding a parameter that allows for both deep heating and delayed cooling. We fit our thermal
evolution models to a homogeneous, physically self-consistent catalog of accurate and precise hot Jupiter system properties in a hierarchical
Bayesian framework. We find that hot Jupiters' interior cooling rates are reduced on average by 95%–98% compared to simpler anomalous heating models. The most plausible explanation for this inference is substantial shallow heating just below their radiative–convective boundaries that enables reinflation with much weaker deep heating. Shallow heating by Ohmic dissipation and/or temperature advection are therefore important components of accurate models of hot Jupiter atmospheres, especially in circulation models. If hot Jupiters are inflated primarily by shallow heating as we propose, then we predict that atmospheric circulation-related observables should increase with temperature in the range $T_{\text{eq}}~\lesssim1500~\text{K}$, peak in the range $1500~\text{K}~\lesssim~T_{\text{eq}}~\lesssim~1800~\text{K}$, and decrease in the range $T_{\text{eq}}~\gtrsim~1800~\text{K}$.
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High Energy Astrophysical Phenomena
Resolving the (Debate About) Nozzle Shocks in Tidal Disruption Events
Zachary L. Andalman, Eliot Quataert, Eric R. Coughlin et al. (+1 more)
When a
star passes within the Roche limit of a supermassive black hole (SMBH), it is pulled apart by the BH's
tidal field in a
tidal disruption event (TDE). The resulting
flare is powered by the circularization and
accretion of bound
stellar debris, which initially returns to the BH on eccentric orbits in a thin debris stream. The returning fluid elements follow inclined orbits that converge near pericenter, resulting in extreme vertical compression to scales $10^{-4}~R_\odot$ and the formation of a nozzle shock. Dissipation at the nozzle shock may affect circularization by altering the properties of the debris stream, but its role is the subject of ongoing debate. We develop an idealized model for the debris stream
evolution combining 3D smoothed-particle hydrodynamics simulations, the semi-analytic affine model, and 1D finite-volume hydrodynamic simulations. Because our model is computationally cheap, we can unambiguously resolve the nozzle shock, use a realistic equation of state, and follow the debris stream
evolution at many different times. Near peak fallback, Hydrogen recombination and molecular Hydrogen formation broaden the stream by a factor $\sim 5$, enhancing dissipation at the nozzle. However, the dissipation is still insufficient to directly circularize the debris by in-plane pressure gradients. Instead, the thicker stream substantially increases the likelihood that the stream self-intersects on the second orbit, despite relativistic nodal precession. The stream properties at self-intersection are sensitive to dissipation at the nozzle and the timing of focal points where the ballistic trajectories of the debris converge. Our results clarify the nozzle shock's role in circularization in TDEs, providing a foundation for more realistic circularization and emission models.
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All authors Zachary L. Andalman, Eliot Quataert, Eric R. Coughlin, C. J. Nixon
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Fábio Köpp, César H. Lenzi, César V. Flores et al. (+1 more)
In this work, we explore how astronomical observations (specifically measurements of masses and radii) can constrain the presence of
quark matter inside
neutron stars, namely the phase transition from
nuclear matter to deconfined
quark matter. Our approach employs
Bayesian analysis to study this constraint. In this sense to model Hadronic matter we used the relativistic mean-field approximation, for which we have selected two parameter sets: \(NL3^{*}\omega\rho\), representing hadronic matter with nucleons only, and $EL3\omega\rho$ with nucleons only and $EL3\omega\rho Y$, which includes hyperons. On the other hand deconfined
quark matter is modeled using the vector-MIT bag model. Also, for our purpose, the first order phase transition is implemented using the Maxwell construction.
Bayesian inference is performed by optimizing three parameters: the bag constant (i.e. $B^{1/4}$), the vector coupling constant \(\left(G_{v}\right)\), and the Dirac sea contribution ($b_{4}$). We found that a phase transition could exist at densities below \(2.0\,n_{0}\) for both the $EL3\omega\rho$ and $NL3^{*}\omega\rho$ parametrizations. As a consequence, the inferred parameters of the vector MIT bag model, based on our likelihood function, imply hybrid
stars with large
quark cores.
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All authors Fábio Köpp, César H. Lenzi, César V. Flores, and Débora P. Menezes
Cosmology and Nongalactic Astrophysics
Foreground Mitigation for CMB Lensing with the Global Minimum Variance Quadratic Estimator
Yuka Nakato, W.L. Kimmy Wu, Ana Carolina Silva Oliveira et al. (+2 more)
Weak gravitational
lensing of the
cosmic microwave background (CMB) is a powerful probe of cosmology, providing insight into structure formation and the
evolution of the universe. Current and upcoming CMB experiments such as SPT-3G and the Simons Observatory (SO) provide high-resolution, low-noise temperature and polarization maps that are ideal for
lensing reconstruction. The global minimum variance (GMV) quadratic
estimator for CMB
lensing reduces reconstruction noise over the standard quadratic
estimator (SQE). In this work, we extend the GMV framework to incorporate the tSZ-deproj and cross-ILC foreground mitigation techniques, which enhance robustness against contamination from astrophysical sources. For a simulation study using SPT-3G Ext-10k and SO Extended configurations at $\ell_{\mathrm{max}}^T = 3500$, the
lensing bias at $L < 1000$ is reduced from $\sim4\%$ with standard GMV and SQE to $2\%$ with tSZ-deproj, and to $< 1\%$ with cross-ILC. These methods enable the construction of foreground-cleaned
lensing maps suitable for cross-correlation analyses, with direct relevance for current and future surveys.
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All authors Yuka Nakato, W.L. Kimmy Wu, Ana Carolina Silva Oliveira, Yuuki Omori, Abhishek S. Maniyar
Instrumentation and Methods for Astrophysics
The impact of lunar topography on the 21-cm power spectrum for grid-based arrays : Insights for the Dark-ages EXplorer (DEX)
S. Ghosh, L. V. E. Koopmans, C. Brinkerink et al. (+17 more)
The Dark Ages (DA) provides a crucial window into the physics of the infant Universe, with the 21-cm signal offering the only direct probe for mapping out the three-dimensional distribution of matter at this epoch. To measure this cosmological signal, the Dark-ages EXplorer (DEX) has been proposed as a compact, grid-based
radio array on the lunar farside. The minimal design consists of a 32 $\times$ 32 array of 3-m dipole
antennas, operating in the $7 - 50$ MHz band. A practical challenge on the lunar surface is that the
antennas may get displaced from their intended positions due to deployment imprecisions and non-coplanarity arising from local surface undulations. We present, for the first time, an end-to-end simulation pipeline, called SPADE-21cm, that integrates a sky model with a DA 21-cm signal model simulated in the lunar frame and incorporating lunar topography data. We study the effects of both lateral (xy) and vertical (z) offsets on the two-dimensional power spectra across the $7 - 12$ MHz and $30 - 35$ MHz spectral windows, with tolerance thresholds derived only for the latter. Our results show that positional offsets bias the power spectrum by $10 - 30$ per cent relative to the expected 21-cm power spectrum during DA. Lateral offsets within $\sigma_{xy}/\lambda \lesssim 0.027$ (at 32.5 MHz) keep the fraction of
Fourier modes with strong contamination (> 50 per cent of the signal) to less than 1 per cent, whereas vertical height offsets affect a larger fraction. This conclusion holds for the 21-cm window with $k_\parallel > 0.5$ $h$ cMpc$^{-1}$ over the range of $k_\perp = 0.003 - 0.009$ $h$ cMpc$^{-1}$.
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All authors S. Ghosh, L. V. E. Koopmans, C. Brinkerink, A. R. Offringa, A. J. Boonstra, S. A. Brackenhoff, E. Ceccotti, J. K. Chege, L. Y. Gao, B. K. Gehlot, L. I. Gurvits, C. Höfer, F. G. Mertens, M. Mevius, S. Munshi, A. Saxena, J. A. Tauber, H. Vedantham, S. Yatawatta, S. Zaroubi
High Energy Astrophysical Phenomena
Self-lensing of moving gravitational-wave sources can break the microlensing crossing timescale degeneracy
Helena Ubach
When a moving gravitational-wave (GW) source travels behind a massive astrophysical object, its signal is gravitationally lensed, showing a waveform distortion similar to a Paczyński curve. We present a first study on the
lensing signature of a massive black hole (MBH) on a frequency-dependent GW signal from a moving compact binary merger (CBC) source, focused on ground-based GW detectors. For both light and GW sources in a Keplerian circular orbit around a MBH lens, the self-
lensing geometry breaks the microlensing degeneracy in the Einstein radius crossing timescale $t_{\rm E}$. The duration of the curve ($2 t_{\rm E}$) becomes independent on the MBH mass $M_{\rm MBH}$, and provides a direct value of the orbital distance $d_{\rm LS}$ of the source around the MBH. However, $M_{\rm MBH}$ remains unknown. In GW signals, the redshifted mass $M_{{\rm MBH},z}$ can additionally be analytically inferred from the interference pattern, once the modulation period $T$, the GW frequency $f$, and $t_{\rm E}$ are known: $M_{{\rm MBH},z}\simeq 2.5\times 10^6\,M_\odot\,(t_{\rm E}/[100\,{\rm s}])\,(f\,T)^{-1}$. If this
lensing signature is not considered, it may be confused with other waveform distortions, especially in the modeling of overlapping CBC signals in next generation ground-based GW detectors. The observation of one of these curves and its associated parameters may help (1) constrain the orbital distance $d_{\rm LS}$ of sources, especially around low-mass MBHs at the center of
star clusters and
galaxies, (2) additionally estimate the mass $M_{{\rm MBH},z}$ of these MBHs, and (3) infer the orbital inclination of the binary. Simultaneously obtaining $d_{\rm LS}$ and $M_{{\rm MBH},z}$ through self-
lensing can help constrain the astrophysical environments where GW signals come from.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
The Strong-$CP$ Problem and its Gauge Axion solution as Evidence for Fundamental Strings
Gia Dvali, Lucy Komisel, Otari Sakhelashvili et al. (+1 more)
The topological susceptibility of the QCD
vacuum provides an understanding of $\theta$-
vacua as
vacua of a Chern-Simons gauge theory. In this way, it gives an immediate proof of the physicality of the boundary $\theta$-term. This makes the essence of the strong-$CP$ puzzle very transparent and offers a solution in form of the gauge
axion, which has exact quality. This
axion represents an intrinsic part of the QCD gauge redundancy without any reference to an anomalous global
symmetry. It is a two-form transforming under the QCD gauge
symmetry. Due to its pure gauge nature, the gauge
axion represents a powerful tool to monitor physics of $\theta$-
vacua in various regimes. Unlike the ordinary Peccei-Quinn
axion, which is UV-completed into a Goldstone phase of a complex scalar and thereby suffers from the quality problem, the gauge
axion is UV-completed directly into a fundamental theory of
gravity. We study the domain wall and string structure of the gauge
axion and show that the strings sourcing it must be a part of this fundamental theory. We thus observe that the absence of the
axion quality problem motivates the presence of fundamental strings. This provides a new argument for a connection between the
axion and
gravity.
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All authors Gia Dvali, Lucy Komisel, Otari Sakhelashvili, Anja Wachowitz
Solar and Stellar Astrophysics
Near-IR CO and CN in classical Cepheids
Scott G. Call, Thomas Griffith, Eric G. Hintz et al. (+4 more)
We present medium resolution near-infrared spectral measurements of the carbon monoxide (CO) and the cyano radical (CN) features in 12
Galactic classical Cepheids. The pulsation periods of our sample range from 5.5 to 69 days, and the
stars studied each had five or more near-IR spectral observations. The CO and CN measurements were used to probe CNO abundances of these
stars, and elemental abundance values from the literature were used to identify the trends of [C/N] and [O/N] with CN and CO. To put these measurements in context, we performed
stellar atmosphere fitting to obtain estimates of
stellar parameters, with a primary focus on effective temperature. Our measurements and temperature estimates show that CN is significantly affected by dredge-up of processed material. We provide discussion as to the potential nature of the recently confirmed classical Cepheid, ET~Vul, and connect our near-infrared CO measurements to the mid-infrared period-colour-
metallicity relation.
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All authors Scott G. Call, Thomas Griffith, Eric G. Hintz, Steve Ardern, Victoria Scowcroft, Jared Davidson, Benjamin Boizelle