Instrumentation and Methods for Astrophysics
HyperAIRI: a plug-and-play algorithm for precise hyperspectral image reconstruction in radio interferometry
Chao Tang, Arwa Dabbech, Adrian Jackson et al. (+1 more)
The next-generation
radio-interferometric (RI)
telescopes require imaging
algorithms capable of forming high-resolution high-dynamic-range images from large data volumes spanning wide frequency bands. Recently, AIRI, a plug-and-play (PnP) approach taking the forward-backward algorithmic structure (FB), has demonstrated state-of-the-art performance in monochromatic RI imaging by alternating a data-fidelity step with a regularization step via learned denoisers. In this work, we introduce HyperAIRI, its hyperspectral extension, underpinned by learned hyperspectral denoisers enforcing a power-law spectral model. For each spectral channel, the HyperAIRI denoiser takes as input its current image estimate, alongside estimates of its two immediate neighboring channels and the spectral index map, and provides as output its associated denoised image. To ensure convergence of HyperAIRI, the denoisers are trained with a Jacobian regularization enforcing non-expansiveness. To accommodate varying dynamic ranges, we assemble a shelf of pre-trained denoisers, each tailored to a specific dynamic range. At each HyperAIRI iteration, the spectral channels of the target image cube are updated in parallel using dynamic-range-matched denoisers from the pre-trained shelf. The denoisers are also endowed with a spatial image faceting functionality, enabling scalability to varied image sizes. Additionally, we formally introduce Hyper-uSARA, a variant of the optimization-based
algorithm HyperSARA, promoting joint sparsity across spectral channels via the $\ell_{2,1}$-norm, also adopting FB. We evaluate HyperAIRI's performance on simulated and real observations. We showcase its superior performance compared to its optimization-based counterpart Hyper-uSARA, CLEAN's hyperspectral variant in WSClean, and the monochromatic imaging
algorithms AIRI and uSARA.
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All authors Chao Tang, Arwa Dabbech, Adrian Jackson, Yves Wiaux
High Energy Astrophysical Phenomena
Magnetohydrodynamic-guiding-center-particle-in-cell Method for Multiscale Plasma Kinetic Simulations
Zitao Hu, Xue-Ning Bai and Xiaochen Sun
We present the formulation,
algorithm and numerical tests of the magnetohydrodynamic-particle-in-
cell (MHD-PIC) method with particles treated under the guiding center approximation, which we term the MHD-gPIC method, and it is implemented in the Athena++ MHD code. The new MHD-gPIC model consists of thermal (cold) fluid and high-energy particles whose dynamics are integrated through guiding center equations including drift motion, with carefully evaluated source terms as particle backreaction. The code is validated with a series of tests, and it is expected to be primarily applicable to study particle acceleration and transport in systems where gyro-resonance is considered insignificant. We also present preliminary studies of particle acceleration during non-relativistic
magnetic reconnection.
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High Energy Astrophysical Phenomena
Universal Relations for Elastic Hybrid Stars and Quark Stars
Chun-Ming Yip, Shu Yan Lau and Kent Yagi
Some compact
stars may contain deconfined
quark matter, forming hybrid
stars or
quark stars. If the
quark matter forms an inhomogeneous condensate in the crystalline color superconducting phase, its
rigidity may be high enough to noticeably alter the
stellar properties. In this paper, we investigate whether these elastic
stars follow the universal relations, i.e., relations insensitive to equations of state, that have been well established for fluid
stars. We improve upon previous studies by allowing
quark matter in the background, static, and spherically symmetric configuration to be sheared. Such background shear can be treated in the form of an effective pressure anisotropy. We then calculate the moment of inertia $I$,
tidal deformability ${\lambda}_2$, and
spin-induced quadrupole moment $Q$ of these models with pressure anisotropy. The $I$-${\lambda}_2$-$Q$ universal relations for the elastic hybrid (
quark)
star models are valid up to a variation of $\approx3\%(4\%)$, larger than that for typical fluid
star models, when the maximal magnitude of
quark matter shear modulus is considered in the crystalline color superconducting phase from realistic calculations. The uncertainty in universal relations related to the
stellar compactness for these elastic
star models, on the other hand, remain comparable to those for typical fluid
star models. Our results demonstrate the validity of universal relations for hybrid
stars and
quark stars with a realistic degree of pressure anisotropy due to the crystalline color superconducting
quark matter.
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Astrophysics of Galaxies
What is the True HI Gas Content in Massive Quiescent Galaxies in the Local Universe?
Xiao Li, Cheng Li, Cheng Cheng et al. (+3 more)
While massive quiescent
galaxies are known to be poor in atomic hydrogen (HI), their true HI content remains poorly constrained due to the limited sensitivity and morphological biases of existing surveys. We present deep HI observations using the Five-hundred-meter Aperture Spherical
radio Telescope (FAST) for a representative sample of 78 low-
redshift massive quiescent
galaxies, selected by
stellar mass ($M_\ast > 10^{10} M_\odot$), color (NUV$-r > 5$), and specific
star formation rate ($\rm \log sSFR < -11\ yr^{-1}$). Our observations reach a remarkable sensitivity of $\log(M_{HI}/M_\ast) = -2.6$ for 55 targets and $\log(M_{HI}/M_\ast) = -3.2$ for 23 targets. We find that one-third of the sample follows the HI scaling relation derived from previous surveys, while the remaining two-thirds exhibit significantly lower HI content. The HI mass fraction shows no clear correlation with specific
star formation rate, NUV$-r$ color index,
stellar surface mass density, and concentration. Our FAST sample shows remarkable similarity to the $ATLAS^{3D}$ sample which only includes early-type
galaxies, both in its high fraction of HI-poor
galaxies and its high satellite fraction among HI-poor
galaxies. These results suggest that while both early-type morphology and environment may contribute to the extreme HI deficiency, neither factor alone fully explains the observed gas depletion, indicating that additional physical mechanisms must be responsible for the extreme HI deficiency prevalent in massive quiescent
galaxies.
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All authors Xiao Li, Cheng Li, Cheng Cheng, Houjun Mo, Jing Wang, Amélie Saintonge
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Effects of Radiative Corrections on Starobinsky Inflation
John Ellis, Tony Gherghetta, Kunio Kaneta et al. (+2 more)
We analyze radiative corrections to the Starobinsky model of inflation arising from self-interactions of the inflaton, and from its Yukawa couplings, $y$, to matter
fermions, and dimensionful trilinear couplings, $\kappa$, to scalar fields, which could be responsible for reheating the Universe after inflation. The inflaton self-interactions are found to be of higher order in the Hubble expansion rate during inflation, and hence unimportant for CMB observations. In contrast, matter couplings to the Starobinsky inflaton can have significant effects on the spectral index of scalar CMB perturbations, $n_s$, and on the tensor-to-scalar ratio, $r$. Using a renormalization-group improved analysis of the effective inflationary potential, we find that the Planck measurement of $n_s$ constrains the inflaton coupling to light
fermions in the Einstein frame: $y < 4.5 \times 10^{-4}$, corresponding to an upper limit on the reheating temperature $T_{\rm RH} < 2 \times 10^{11}~{\rm GeV}$, whereas the ACT DR6 measurement of $n_s$ corresponds to $3.8 \times 10^{-4} < y < 5.6 \times 10^{-4}$ and $1.7 \times 10^{11} ~{\rm GeV} < T_{\rm RH} < 2.8 \times 10^{11}~{\rm GeV}$, while the upper limits on $r$ provide weaker constraints. Planck data also imply a constraint on a trilinear inflaton coupling to light scalars in the Einstein frame: $\kappa \leq 4 \times 10^{12}~{\rm GeV}$, corresponding to $T_{\rm RH} \leq 4.2 \times 10^{13}~{\rm GeV}$. We further present constraints on inflaton couplings to massive
fermions and scalars, and analyze constraints on couplings in the Jordan frame.
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All authors John Ellis, Tony Gherghetta, Kunio Kaneta, Wenqi Ke, Keith A. Olive
Instrumentation and Methods for Astrophysics
Polarization based direction of arrival estimation using a radio interferometric array
Sarod Yatawatta
Direction of arrival (DOA) estimation is mostly performed using specialized arrays that have carefully designed receiver spacing and layouts to match the operating frequency range. In contrast,
radio interferometric arrays are designed to optimally sample the
Fourier space data for making high quality images of the sky. Therefore, using existing
radio interferometric arrays (with arbitrary geometry and wide frequency variation) for DOA estimation is practically infeasible except by using images made by such interferometers. In this paper, we focus on low cost DOA estimation without imaging, using a subset of a
radio interferometric array, using a fraction of the data collected by the full array, and, enabling early determination of DOAs. The proposed method is suitable for transient and low duty cycle source detection. Moreover, the proposed method is an ideal follow-up step to online
radio frequency interference (RFI) mitigation, enabling the early estimation of the DOA of the detected RFI.
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High Energy Astrophysical Phenomena
Assessing the Distance for Probing the Nuclear Equation of State with Supernova Gravitational Waves
Y. Sultan Abylkairov, Matthew C. Edwards, Artyom Ostrikov et al. (+6 more)
Gravitational waves from core-collapse
supernovae provide a unique probe of the equation of state (EOS) of high density matter. In this work, we focus on the bounce signal from numerical simulations of rotating
supernovae and explore its potential for EOS inference. We employ a support vector machine, previously shown to perform best among tested methods, to classify GW signals simulated for 18 EOS models. For optimally oriented sources, we estimate that the Advanced LIGO A+ detector can probe the EOS for
Galactic events, while third-generation observatories such as the Einstein
Telescope and
Cosmic Explorer can reach substantially farther. For randomly oriented sources, only these next-generation detectors are expected to have sufficient sensitivity. These results represent the potential observational range for probing the
nuclear EOS, although, due to the simplifying assumptions adopted, they should be regarded as approximate upper limits.
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All authors Y. Sultan Abylkairov, Matthew C. Edwards, Artyom Ostrikov, Yersultan Tleukhanov, Alejandro Torres-Forné, Pablo Cerdá-Durán, José Antonio Font, Marek J. Szczepańczyk, Ernazar Abdikamalov
Solar and Stellar Astrophysics
An Improved Atlas of Full-Scan Spectra from ISO/SWS
D. R. Mizuno, T. A. Kuchar, Kathleen E. Kraemer et al. (+4 more)
We present an atlas of full-scan spectra from the Short-Wavelength Spectrometer (SWS) aboard the Infrared Space Observatory (ISO) after reprocessing and improving an earlier version published 22 years ago. The SWS spectra cover the wavelength range from 2.35 to 45.3 {\mu}m. They include scans in 12 separate bands, and we have updated the methods used to combine those bands into a single continuous spectrum. The main improvement comes from applying multiple constraints, including new photometry and spectra from the Infrared Spectrograph (IRS) on the Spitzer Space
Telescope that have become available since the release of the original products, and individualized
attention to each spectrum, to renormalize the separate bands into a more consistent single spectrum. In particular this removed unphysical negative fluxes that were common in the original data products. The new database, with 1035 reprocessed spectra, will be available to the community at IRSA, which also hosts the original processing.
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All authors D. R. Mizuno, T. A. Kuchar, Kathleen E. Kraemer, G. C. Sloan, Samantha Greene, Elianna Cohen, Holly Branco
Earth and Planetary Astrophysics
TOI-283 b: A transiting mini-Neptune in a 17.6-day orbit discovered with TESS and ESPRESSO
F. Murgas, E. Pallé, A. Suárez Mascareño et al. (+51 more)
Super-Earths and mini-Neptunes are missing from our
Solar System, yet they appear to be the most abundant planetary types in our
Galaxy. A detailed characterization of key
planets within this population is important for understanding the formation mechanisms of rocky and gas
giant planets and the diversity of planetary interior structures. In 2019, NASA's TESS satellite found a transiting
planet candidate in a 17.6-day orbit around the
star TOI-283. We started radial velocity (RV) follow-up observations with ESPRESSO to obtain a mass measurement. Mass and radius are measurements critical for planetary classification and internal composition modeling. We used ESPRESSO spectra to derive the
stellar parameters of the
planet candidate host
star TOI-283. We then performed a joint analysis of the photometric and RV data of this
star, using Gaussian processes to model the systematic noise present in both
datasets. We find that the host is a bright K-type
star ($d = 82.4$ pc, $\mathrm{T}_\mathrm{eff} = 5213 \pm 70$ K, $V = 10.4$ mag) with a mass and radius of $\mathrm{M}_\star = 0.80 \pm 0.01\; \mathrm{M}_\odot$ and $\mathrm{R}_\star = 0.85 \pm 0.03\; \mathrm{R}_\odot$. The
planet has an orbital period of $P = 17.617$ days, a size of $\mathrm{R}_\mathrm{p} = 2.34 \pm 0.09\; \mathrm{R}_\oplus$, and a mass of $\mathrm{M}_\mathrm{p} = 6.54 \pm 2.04\; \mathrm{M}_\oplus$. With an
equilibrium temperature of $\sim$600 K and a bulk density of $\rho_\mathrm{p} = 2.81 \pm 0.93$ g cm$^{-3}$, this
planet is positioned in the mass-radius diagram where planetary models predict H$_2$O- and H/He-rich envelopes. The ESPRESSO RV data also reveal a long-term trend that is probably related to the
star's activity cycle. Further RV observations are required to confirm whether this signal originates from
stellar activity or another planetary body in the system.
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All authors F. Murgas, E. Pallé, A. Suárez Mascareño, J. Korth, F. J. Pozuelos, M. J. Hobson, B. Lavie, C. Lovis, S. G. Sousa, D. Bossini, H. Parviainen, A. Castro-González, V. Adibekyan, C. Allende Prieto, Y. Alibert, F. Bouchy, C. Briceño, D. A. Caldwell, D. Ciardi, C. Clark, K. A. Collins, K. I. Collins, S. Cristiani, X. Dumusque, D. Ehrenreich, P. Figueira, E. Furlan, R. Génova Santos, C. Gnilka, J. I. González Hernández, Z. Hartman, S. B. Howell, J. M. Jenkins, N. Law, C. Littlefield, G. Lo Curto, A. W. Mann, C. J. A. P. Martins, A. Mehner, G. Micela, P. Molaro, N. J. Nunes, F. Pepe, R. Rebolo, H. M. Relles, N. C. Santos, N. J. Scott, S. Seager, A. Sozzetti, S. Udry, C. N. Watkins, J. N. Winn, M. R. Zapatero Osorio, C. Ziegler
High Energy Astrophysical Phenomena
Wave-Mediated Boundary Layers of Accretion Discs: Role of Internal Structure of the Accretor
Samuel G. D. Turner, Roman R. Rafikov and Alexander A. Philippov
Disc
accretion onto astrophysical objects with a material surface proceeds through the boundary layer (BL) – a radially narrow region in the inner disc where the incoming gas must slow down its rotation before settling onto the surface of the accretor. Here we numerically study a BL in which the angular momentum transport in the layer is accomplished via the excitation of global acoustic waves. While the earlier studies of such wave-mediated BLs typically modeled the internal structure of the central object as a globally isothermal sphere with sharply rising density profile, here we explore the effect of other internal density and temperature profiles on the mode operation. We model the inner structure of an accretor as a polytropic sphere, allowing a shallower increase of density and a non-trivial temperature profile inside the object. While the mix of acoustic modes observed in our long-duration (1000 inner orbits long) 2D hydrodynamic simulations is a weak function of the polytropic index $n$ of the accretor's structure, the mass
accretion rate and the angular momentum flux across the BL show a clear dependence on $n$, both decreasing in amplitude as $n$ is lowered. Interestingly, in 2D these transport metrics are better correlated not with $n$ but with a total mass inside the central object contained within the simulation domain. These results improve our understanding of the wave-mediated BL
accretion by quantifying the effect of the inner structure of the accretor on the excitation and propagation of acoustic modes mediating the BL transport.
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Cosmology and Nongalactic Astrophysics
Implications of a high growth index on the variation of $G$
Ícaro. B. S. Cortês, Léo. G. Medeiros and Ronaldo C. Batista
A recent determination of the growth index indicates a value significantly higher than the $\Lambda$CDM prediction, suggesting that alternative scenarios to $\Lambda$CDM may be required. In this work, we investigate whether a time-varying Newton's constant, $G_N$, can account for such a high growth index, $\gamma=0.063\pm0.025$. Adopting a phenomenological approach, we study two parameterizations of the effective gravitational coupling, $G_{\rm eff}$, one based on a Taylor expansion and another linked to the energy density parameter of Dark Energy. We constrain the models with
Cosmic Chronometers (CC), Dark Energy Spectroscopic Instrument
baryon acoustic oscillations (data release 2), CMB priors, and a gaussian likelihood for the growth index. We show that the constant $\gamma$ approximation is accurate for the parametrization linked to the energy density parameter of dark energy, but presents a non-negligible error for the other case, which we treat as a systematic error in the analysis. We find a $2.4\sigma-3.4\sigma$ tension level with constant $G_{\rm eff}$, depending on the parametrization. The results indicate that $G_{\rm eff}<G_N$ around the period of accelerated expansion, corresponding to a weaker effective gravitational interaction on cosmological scales, which leads to a suppression of the growth of cosmological structures.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Role of dynamical early dark energy in Hubble tension through warm inflation
Anupama B
The role of dissipation from the thermal bath of minimal warm inflation (MWI)is examined with the
Cosmic Microwave Background (CMB) to assess its ability to mimic a dynamical dark energy component. An increase in the dissipation strength modifies temperature anisotropies and shifts the phase and peak structure of the CMB TT angular power spectrum in a manner analogous to evolving dark energy.
Bayesian parameter estimation for cosmological parameters of MWI using Markov Chain Monte Carlo analysis with Planck18 + BICEP/Keck 2018 + sn.pantheon + SH0ES likelihoods reveals deviations from standard $\Lambda$CDM constraints, accompanied by an enhancement in the matter power spectrum that signals possible physics beyond the conventional model. Notably, the present day Hubble parameter increases with dissipation strength, indicating that minimal warm inflation can naturally generate a dynamical early dark energy like behavior capable of alleviating the Hubble tension. Within this unified framework, early and late time estimates of $H_0$ can be reconciled. Further, the time varying dark energy equation of state consistent with recent DESI DR2 indication favours a
quantum gravity phase preceding the inflationary epoch.
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High Energy Astrophysical Phenomena
Gradus.jl: spacetime-agnostic general relativistic ray-tracing for X-ray spectral modelling
Fergus J. E. Baker and Andrew J. Young
We introduce Gradus.jl, an open-source and publicly available general relativistic ray-tracing toolkit for spectral modelling in arbitrary spacetimes. Our software is written in the Julia programming
language, making use of forward-mode automatic differentiation for computing the Christoffel symbols during geodesic integration, and for propagating derivatives through the entire ray-tracer. Relevant numerical methods are detailed, and our models are validated using a number of tests and comparisons to other codes. The differentiability is used to optimally calculate Cunningham transfer functions – used to efficiently pre-compute relativistic effects in spectral models. A method is described for calculating such transfer functions for disc with non-zero vertical height, including the treatment of self-obscuration. An extension of the transfer function formalism that includes timing information is described, and used to calculate high-resolution reverberation lag spectra for a lamppost corona. The lag-frequency and lag-energy spectra for a Shakura-Sunyaev
accretion disc with various lamppost heights and Eddington ratios are calculated, and the general impact of disc thickness in reflection models is discussed.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The Missing Multipole Problem: Investigating biases from model starting frequency in gravitational-wave analyses
Ryan Ursell, Charlie Hoy, Ian Harry et al. (+1 more)
Our ability to infer the true source properties of colliding black holes from gravitational wave observations requires not only accurate waveform models but also their correct use. A key property when evaluating time-domain models is when to start the waveform: choosing a time that is too late can omit low-frequency power from higher order multipoles. By focusing on binary systems with total mass $\ge 200 \, M_{\odot}$, we show that current detectors are sensitive to this missing power and biased source properties can be obtained. We show that for systems with total mass $\lesssim 300 \, M_{\odot}$, mass ratio $\gtrsim 0.33$, and signal-to-noise ratio $\rho \gtrsim 20$, templates starting at $20 \, \mathrm{Hz}$ recover biased source properties. As the total mass increases, and the component masses become more asymmetric, templates starting from $13 \, \mathrm{Hz}$ recover biased properties. If the gravitational-wave signal is observed at signal-to-noise ratio $\rho < 20$, time-domain models can start from $20\, \mathrm{Hz}$ as statistical uncertainties dominate.
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All authors Ryan Ursell, Charlie Hoy, Ian Harry, Laura K. Nuttall
Cosmology and Nongalactic Astrophysics
Multi-species Dark Matter with Warmth and Randomness
Mustafa A. Amin, M. Sten Delos and Kaixin Yang
We present a general analytic framework for the
evolution of
cosmic structure in multi-species dark matter models that simultaneously incorporates finite velocity dispersion and Poisson fluctuations. Our approach accommodates arbitrary numbers of dark matter components with distinct mass fractions, velocity distributions, and number densities – ranging from cold particles to warm species and sparse populations such as
primordial black holes or
solitons. The framework is based on solving a truncated BBGKY hierarchy, whose solution is obtained by solving Volterra integral equations. We provide an efficient
algorithm to solve for the total, as well as inter- and intra-species power spectra. Worked examples with two-component mixtures illustrate how isocurvature (initially Poisson) and adiabatic spectra evolve differently depending on the properties of the warm or sparse fraction. This
evolution is controlled by the free-streaming and Jeans scales, and the results match analytic estimates and $N$-body simulations.
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Astrophysics of Galaxies
Evolution of the kinematic properties of rotating multiple-population globular clusters
Ethan B. White, Enrico Vesperini, Emanuele Dalessandro et al. (+1 more)
Globular clusters (GCs) host multiple
stellar populations differing in their chemical and dynamical properties. A number of models for the formation of multiple populations predict that the subsystem of second generation (SG)
stars is characterized by a more centrally concentrated spatial distribution and a more rapid rotation than the system of first generation (FG)
stars. We present the results of N-body simulations exploring the long-term dynamical
evolution of rotating multiple-population GCs. We study the
evolution of systems starting with four different orientations of the GC's total internal angular momentum vector relative to the orbital angular momentum. We explore the
evolution driven by two-body relaxation and the effects of the GC's interaction with the
galactic tidal field. We focus on the kinematic differences between the two generations and we quantify them by exploring the FG and SG rotation velocity and angular momenta. We find that kinematic differences between the generations persist for most of the GCs' lifetimes, although the strength of these differences decreases after a few relaxation times. The differences can be seen most clearly in the lowest-mass
stars. We find that the GCs' internal angular momentum gradually aligns with the orbital angular momentum, although there is little difference in this
alignment between the FG and SG systems. We also find that
stars in the GC's outer regions align with the orbital angular momentum vector more rapidly than those in the inner regions leading to a variation of the orientation of the internal angular momentum with the clustercentric distance. The
alignment between internal angular momentum and orbital angular momentum occurs more rapidly for low-mass
stars. We study the
evolution of the anisotropy in the velocity distribution and find the SG to be characterized by a stronger radial anisotropy than the FG.(abridged)
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All authors Ethan B. White, Enrico Vesperini, Emanuele Dalessandro, Anna Lisa Varri
Astrophysics of Galaxies
Taming the plunge: A circularization trap of supermassive black hole binaries
Pau Amaro Seoane, Alessandra Mastrobuono Battisti, Chingis Omarov et al. (+5 more)
We investigate the orbital eccentricity
evolution of supermassive black hole binaries within
galactic environments. We analyze the dynamics in triaxial merger remnants and subsequent interactions with geometrically thick
nuclear discs. We confirm that gravitational torques in triaxial potentials efficiently extract angular momentum, resulting in binary formation with high initial eccentricities. We then analyze the binary-disc interaction using a 3D analytical framework incorporating the Airy formalism and potential softening. We present a self-consistent derivation demonstrating that the 3D suppression of high-order torques leads to distinct scalings with disc thickness ($h$): migration rates $\tau_a^{-1} \propto h^{-3}$ and eccentricity damping rates $\tau_e^{-1} \propto h^{-5}$. This establishes a timescale hierarchy, $\tau_e/\tau_a \propto h^2$. For typical parameters ($h\approx 0.2$), eccentricity damping is significantly faster than orbital decay ($\tau_e \approx 0.04 \, \tau_a$). We further develop a wavelet-based formalism to quantify the impact of disc inhomogeneities arising from
accretion feedback and
turbulence. We derive the
stochastic torque variance in the wavelet domain and employ a Fokker-Planck analysis to determine the
equilibrium eccentricity distribution. While
stochastic fluctuations counteract deterministic damping, the strong damping imposed by the thick disc geometry ensures the
equilibrium eccentricity remains small unless the fluctuations are highly non-linear. Hence, even if born highly eccentric, SMBHBs are rapidly circularized. This circularization trap forces binaries to approach the gravitational wave-dominated regime on nearly circular orbits, prolonging the total merger timescale. This introduces a substantial cosmological delay governed by
stellar relaxation, which impacts detection rates and the modeling of SMBH assembly in cosmological frameworks.
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All authors Pau Amaro Seoane, Alessandra Mastrobuono Battisti, Chingis Omarov, Denis Yurin, Maxim Makukov, Dana Kuvatova, Gulnara Omarova, Anton Gluchshenko
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Atomic Quantum Sensors for High-Frequency Gravitational Wave Searches
Yi-fu Cai, Luca Visinelli and Sheng-Feng Yan
High-frequency gravitational waves (GWs), spanning frequencies from the microwave to the optical band, remain experimentally unexplored despite strong motivation from early-Universe dynamics, high-energy cosmology, and exotic compact objects. We propose a detection framework in which an incident GW excites an eigenmode of a high-$Q$ resonator in the presence of a static
magnetic field through GW-induced electromagnetic mode conversion; the resulting cavity field is then read out using atomic sensors placed outside the magnetized volume. We analyze two concrete architectures: microwave detection based on Rydberg transitions and optical/near-infrared Raman schemes. For each, we derive projected strain sensitivities achievable with realistic, though ambitious,
magnetic fields, cavity parameters, and atomic ensembles. Under optimistic assumptions on cavity performance, signal coherence, and technical noise, optical Raman implementations could approach
benchmark narrowband coherent strain sensitivities relevant for speculative high frequency GW scenarios, while microwave systems may probe
benchmark sensitivities in an otherwise unexplored frequency range. These setups motivate advances in high-$Q$ cavities, strong-field magnets, and
quantum-limited atomic sensors, with broader implications for
quantum instrumentation and fundamental physics.
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High Energy Astrophysical Phenomena
Impact of Neutrino Flavor Conversions on Neutron Star Merger Dynamics, Ejecta, Nucleosynthesis, and Multi-Messenger Signals
Yi Qiu, David Radice, Sherwood Richers et al. (+3 more)
We present numerical relativity simulations of binary
neutron star mergers incorporating
neutrino flavor transformations triggered by fast
flavor instability,
quantum many-body effects, or potential beyond standard model physics. In both long-lived and short-lived remnant scenarios,
neutrino flavor conversions modify species-dependent
neutrino luminosities and mean energies, and drive the matter towards more
neutron rich conditions. They produce up to $300\%$ more
neutron rich ejecta and significantly boost the r-process yields, especially in low-density, near-equatorial
outflows. We identify regions unstable to fast
flavor instabilities and find that these instabilities persist despite
flavor conversions. We further test the sensitivity to the equilibration timescale of the
flavor conversions, finding that slower
flavor conversions can interact with thermodynamic equilibration, and increase the
neutron richness of the ejecta.
Flavor conversions may also contribute to stronger gravitational wave and
neutrino emissions, pointing to a correlation between
neutrino transport and merger dynamics. These results highlight the potential impact of
flavor conversions while motivating future work to improve on theoretical understanding of
flavor instabilities in global simulations.
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All authors Yi Qiu, David Radice, Sherwood Richers, Federico Maria Guercilena, Albino Perego, Maitraya Bhattacharyya
Astrophysics of Galaxies
Black Holes in Globular Clusters: A Structural and Kinematic Perspective
Alessandro Della Croce
Black holes (BHs) play a major role in the structural and dynamical evolutions of Globular Clusters (GCs). Several recent works searched for BHs in
Galactic GCs using scaling relations derived from numerical simulations. However, the conclusions drawn by such approaches are strongly dependent on the specific prescriptions adopted in numerical simulations. Therefore, we analyzed a survey of 101 Monte Carlo simulations to identify some observable parameters that allow us to probe the present-day BH population in GCs reliably. We thoroughly show that a single observable is not suited to infer the BH mass fraction in real GCs: similar values could be attained by systems with different BH mass fractions, depending on the specific dynamical
evolution of the system. Finally, we present a combination of observable parameters that efficiently breaks this degeneracy. We also compare values from numerical simulations with a sample of
Galactic GCs.
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Astrophysics of Galaxies
An Investigation into the Low-Mass Fundamental Metallicity Relation in the Local and High-z Universe
Isaac H. Laseter, Michael V. Maseda, Andrew J. Bunker et al. (+3 more)
Recent JWST/NIRSpec observations have revealed high-$z$
star-forming
galaxies depart from the Fundamental
Metallicity Relation (FMR), yet the $z = 0$ FMR has not been well-characterized in the low-mass regime ($\rm log(M_{\star}/M_{\odot}) \lesssim 9$) for an appropriate comparison of low- and high-$z$ systems. We attempt to rectify this limitation through a meta-analysis, providing a local, observational comparison for future high-$z$ FMR studies. We analyzed common FMR fitting methods for $\sim 700$ [OIII]$\lambda 4363$ emitters with $\rm log(M_{\star}/M_{\odot}) \lesssim 9$ at $z \sim 0$. We find no evidence of the FMR below $\rm log(M_{\star}/M_{\odot}) \lesssim 9$ through any method, suggesting that slowly-evolving, quasi-steady state gas reservoirs are not yet established. We simultaneously find a weak positive correlation between
metallicity and
star formation, and that these systems are gas-rich with substantial diversity in effective yields ($y_{\rm eff}$) spanning $\rm \sim 3~dex$. We demonstrate increasing $y_{\rm eff}$ correlates with decreasing FMR offsets, which in the context of the analytical and non-
equilibrium gas models of Dalcanton et al. (2007), indicates a scenario where
star formation bursts rapidly return and eject metals from the ISM before subsequent gas-balancing. Pristine infall diluting the ISM metal-content cannot lead to the $y_{\rm eff}$ diversity we measure, and thus is not the primary process behind FMR deviations. Our results suggest low-$\rm M_{\star}$ systems, regardless of
redshift, depart from a steady-state gas reservoir shaping the canonical FMR, in which
metallicity variations are primarily driven by
star formation and enriched
outflows. With this characterization, we demonstrate $z \gtrsim 3$ [OIII]$\lambda 4363$ systems are indeed more metal-poor than $z \sim 0$ counterparts ($\rm \Delta 12+log(O/H) = 0.3~dex$) at fixed $\rm M_{\star}$.
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All authors Isaac H. Laseter, Michael V. Maseda, Andrew J. Bunker, Alex J. Cameron, Mirko Curti, Charlotte Simmonds
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Radiative Correction from Secret Neutrino Interactions and Implications for Neutrino-Scattering Experiments
Saeid Foroughi-Abari, Kevin J. Kelly and Yue Zhang
New, neutrinophilic mediators are one potential extension beyond the Standard Model of particle physics. Often, studies of neutrinophilic mediator consist of searching for direct evidence of its production and/or its tree-level virtual effect for generating strong
neutrino self-interaction. In this work, we focus instead on the fact that such new mediators also lead to deviations in
neutrino-matter scattering via radiative corrections. With a mediator mass well below the electroweak scale, these effects are potentially observable in a variety of contexts, including coherent elastic
neutrino-
nucleus scattering (CEvNS),
neutrino deeply-inelastic scattering ($\nu$DIS), and
neutrino-electron scattering (e.g., at Borexino). Additionally, such effects lead to new contributions to the $Z$-
boson decay width and to non-standard
neutrino interactions relevant for long-baseline oscillation experiments. We explore all of these scenarios in some depth, building on the rich phenomenology associated with neutrinophilic mediators.
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Cosmology and Nongalactic Astrophysics
Phantom Mirage from Axion Dark Energy
Rayne Liu, Yijie Zhu, Wayne Hu et al. (+1 more)
Supernova (SN) and
baryon acoustic oscillation (BAO) distance measures have recently provided hints that the dark energy is not only dynamical but apparently evolves from normal to phantom dark energy between
redshifts $0<z<1$. A normal
axion dark energy component in the mass range just below the Hubble scale can mimic a phantom component by appearing as dark energy at $z=1$ and dark matter at $z=0$, raising the possibility of a phantom mirage. We show that there is a wide range of
axion dark energy contributions that can resolve the SN-BAO tension as well as thawing quintessence does, leaving BAO tension with the
cosmic microwave background (CMB) for the distance measures from $z\sim 1$ to recombination to be resolved at high
redshifts. With
axions, raising the optical depth to reionization to $\tau \approx 0.1$ works essentially as well as $w_0-w_a$ phantom dark energy for all but the lowE CMB data, with a remaining $\Delta\chi^2\sim -16$ compared with $\Lambda$CDM, whereas a small spatial
curvature of $\Omega_K \sim 0.003$ can largely relax the full SN-BAO-CMB tension with a total $\Delta\chi^2 \sim -12$.
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All authors Rayne Liu, Yijie Zhu, Wayne Hu, Vivian Miranda
Cosmology and Nongalactic Astrophysics
Dark Matter Subhalos and Higher Order Catastrophes in Gravitational Wave Lensing
Luka Vujeva, Jose María Ezquiaga, Daniel Gilman et al. (+2 more)
Gravitational
lensing is an invaluable probe of the nature of dark matter, and the structures it forms. Lensed gravitational waves in particular allow for unparalleled sensitivity to small scale structures within the lenses, due to the precise time resolution in combination with the continuous monitoring of the entire sky. In this work, we show two distinct ways of using strongly lensed gravitational waves to identify the presence of dark matter subhalos: \emph{{i)}} through higher order caustics generating high relative magnification ($\mu_r > 2$), short time delay image pairs that break the caustic universality relations of single dark matter
halos, which occur for $\sim 1-10$ percent of strongly lensed events in our cold dark matter models, and ii) through the presence of more than three highly magnified images, which occur for $\sim 0.01-1$ percent of the same simulated events. We find that these results are highly sensitive to the concentrations of subhalos in our simulations, and more mildly to their number densities. The presence of low-mass subhalos increases the probability of observing wave-optics
lensing in lensed gravitational waves, which is studied by solving the diffraction integral with the stationary phase approximation, as well as numerically. We also report distinct quantitative and qualitative differences in the distributions of relative magnifications and time delays for subhalo populations with increased number densities or concentrations. With the upcoming detection of strongly lensed events by ground- and space- based detectors, comparisons against these simulated distributions will provide insight into the nature of dark matter.
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All authors Luka Vujeva, Jose María Ezquiaga, Daniel Gilman, Srashti Goyal, Miguel Zumalacárregui
Cosmology and Nongalactic Astrophysics
Non-Minimally Coupled Quintessence in Light of DESI
Samuel Sánchez López, Alexandros Karam and Dhiraj Kumar Hazra
We analyze a model of quintessence governed by an exponential potential and non-minimally coupled to
gravity, in light of recent
datasets, including
cosmic microwave background,
baryon acoustic oscillations, and
supernovae distance
moduli observations. Mainly focusing on the Palatini formulation of
gravity, a phase space analysis reveals the existence of a late-time stable de Sitter attractor as long as the non-minimal coupling constant is negative, regardless of the value of the slope of the exponential. Fitting to CMB+DESI+DESY5 data, we find strong evidence for our model over $\Lambda$CDM, with a Bayes factor $\log B = 5.52$. Furthermore, the data seem to prefer dynamical dark energy at $>3\sigma$ C.L. and a phantom crossing in the barotropic parameter of dark energy at $2-3\sigma$ C.L.. We find that the scalar field dynamics in the Palatini formalism provides marginally better agreement to the data compared to the metric formalism.
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High Energy Astrophysical Phenomena
X-ray panorama of the SS433/W50 complex by SRG/eROSITA
Rashid Sunyaev, Ildar Khabibullin, Eugene Churazov et al. (+3 more)
The
Galactic microquasar SS 433 and the
radio nebula W50 surrounding it present a prototypical example of a hyper-Eddington binary system shaping its ambient interstellar medium via energetic
outflows. In this paper, we present X-ray observations of the SS 433/W50 complex by the eROSITA
telescope onboard the SRG space observatory. These data provide images of the entire nebula characterized by a very large dynamic range and allow spectral analysis of the diffuse X-ray emission. In particular, these data illustrate a close connection between the thermal and non-thermal components of W50 on scales ranging from sub-parsecs, represented by narrow X-ray bright filaments, to the entire extent of $\gtrsim 100\,{\rm pc}$ of the nebula. These data also allowed us to fully characterize a pair of nearly symmetric, sharp-edged, elongated structures aligned with the orbital axis of the binary system, which lack
radio counterparts but are prominent in very-high-energy gamma-ray emission. The resulting multifaceted picture of the interaction between energetic
outflows and the surrounding medium paves the way for future focused multiwavelength observations and dedicated numerical simulations.
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All authors Rashid Sunyaev, Ildar Khabibullin, Eugene Churazov, Marat Gilfanov, Pavel Medvedev, Sergey Sazonov
Astrophysics of Galaxies
StarStream: Automatic detection algorithm for stellar streams
Yingtian Chen, Oleg Y. Gnedin, Adrian M. Price-Whelan et al. (+1 more)
The
Gaia mission has led to the discovery of over 100
stellar streams in the Milky Way, most of which likely originated from globular clusters (GCs). As the upcoming wide-field surveys can potentially continue to increase the number of known streams, there is a growing need to shift focus from manual detection of individual streams to automated detection methods that prioritize both quality and quantity. Traditional techniques rely heavily on the visual expectation that GC streams are dynamically cold and thin. This assumption does not hold for all streams, whose morphologies and kinematics can vary significantly with the progenitor's mass and orbit. As a result, these methods are biased toward a subset of the whole stream population, with often unquantified purity and completeness. In this work, we present StarStream, an automatic stream detection
algorithm based on a physics-inspired model rather than visual expectation. Our method provides a more accurate prediction of stream
stars in the multi-dimensional space of observables, while using fewer free parameters to account for the diversity of streams. Applied to a mock GC stream catalog tailored for the
Gaia DR3
dataset, our
algorithm achieves both purity and completeness of at least 65% at
Galactic latitudes |b| > 30 degree.
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All authors Yingtian Chen, Oleg Y. Gnedin, Adrian M. Price-Whelan, Colin Holm-Hansen