Earth and Planetary Astrophysics
CORINOS IV: Quantifying Baseline-Fitting Uncertainties in SO$_2$ Ice Measurements with JWST/MIRI
Rachel E. Gross, Yao-Lun Yang, L.Ilsedore Cleeves et al. (+15 more)
Sulfur dioxide (SO$_2$) ice has been tentatively detected in protostellar envelopes, but its reliability as a solid-state sulfur reservoir remains unclear. We present new measurements of SO$_2$ ice from 6.8-8.5 $\mu$m toward four Class 0 protostars observed with JWST's Mid-Infrared (MIRI) Medium Resolution Spectrometer, as part of the COMs ORigin Investigated by the Next-generation Observatory in Space (CORINOS) program. The sample spans a luminosity range from 1 $L_\odot$ (B335, IRAS 15398-3359) to 10 $L_\odot$ (L483, Ser-emb~7). To assess continuum placement uncertainty in absorption spectra, we apply randomized
polynomial fits over the restricted region. We fit laboratory spectra from the Leiden Ice Database for Astrochemistry (LIDA) using the open-source Python library Omnifit. We detect the 7.7 $\mu$m CH$_4$ band in all sources and find its column density robust to baseline choice, providing a reference for evaluating the weaker SO$_2$ feature on its blue shoulder and quantifying baseline-related uncertainty. Three SO$_2$ laboratory ices were tested: pure SO$_2$ ice yields 0.3-1.2% of volatile sulfur may be locked in SO$_2$ ice (lower and upper limits); CH$_3$OH:SO$_2$ ice gives 0.02-0.18%, but with lower quality fitting. The best-fitting H$_2$O:SO$_2$ ice yields 0.2-0.9%, which we consider the most realistic. These ranges define plausible bounds on SO$_2$ ice abundances in our sample. We find evidence for SO$_2$ in Ser-emb 7, L483, and IRAS 15398-3359, but emphasize the noisy spectrum of B335 prevents a definitive detection. Comparing SO$_2$ ice abundances across the different environments, we assess how conditions influence role of SO$_2$ as a potential sulfur reservoir and implications for the longstanding “missing sulfur” problem.
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All authors Rachel E. Gross, Yao-Lun Yang, L.Ilsedore Cleeves, Ewine F. van Dishoeck, Robin T. Garrod, Mihwa Jin, Nami Sakai, Christopher N. Shingledecker, JaeYeong Kim, Jennifer B. Bergner, Neal J. Evans II, Joel D. Green, Chul-Hwan Kim, Jeong-Eun Lee, Yuki Okoda, Will R.M. Rocha, Brielle Shope, Himanshu Tyagi
High Energy Astrophysical Phenomena
Simultaneous JWST, NuSTAR, and VLA Monitoring of Sgr A*: A Unified Picture of the Variable IR, X-ray and Radio Emission
F. Yusef-Zadeh, M. Wardle, R. G. Arendt et al. (+5 more)
Flux variability is a fundamental channel of information from Sgr A* because of its direct probe of processes occurring within an
accretion disk under strong
gravity. We present simultaneous IR, X-ray and
radio observations of Sgr A* on 2024 Apr 05 using JWST, NuSTAR, and VLA. We report the detection of a strong X-ray
flare with a luminosity of $\sim5.2x10^{35}$ erg/s coincident with a bright near-IR
flare, and a brightening in
radio about an hour later. We investigate the candidate physical mechanisms for the X-ray
flare emission and conclude that this can best be explained by inverse Compton scattering of near-IR
flare radiation. We propose a dynamic scenario analogous to a coronal mass ejection in which a
magnetic flux rope is ejected from Sgr A*'s inner
accretion flow with a current sheet extending down from the rope to the bulk of the
accretion flow. Reconnection within the sheet produces oppositely directed flows of accelerated particles moving upwards towards the rope and downwards towards the
accretion flow. Infrared radiation from the approaching energetic electrons is enhanced by beaming and up-scattered by thermal electrons in the
accretion flow to produce the strong X-ray
flare. Meanwhile, the relativistic electrons moving in the opposite direction away from the disk experience weaker
magnetic fields so radiate at longer wavelengths by feeding into the
magnetic flux tube and adiabatically cooled during its subsequent expansion. This physical picture attempts to unify the origin of the variable emission from Sgr A* at IR, X-ray and
radio/submm wavelengths.
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All authors F. Yusef-Zadeh, M. Wardle, R. G. Arendt, C. O. Heinke, C. J. Chandler, H. Bushouse, G. A. Moellenbrock, J. M. Michail
Solar and Stellar Astrophysics
A Physics Informed Neural Network For Deriving MHD State Vectors From Global Active Regions Observations
Subhamoy Chatterjee and Mausumi Dikpati
Solar active regions (ARs) do not appear randomly but cluster along longitudinally warped toroidal bands ('toroids') that encode information about
magnetic structures in the tachocline, where global-scale organization likely originates. Global MagnetoHydroDynamic Shallow-Water Tachocline (MHD-SWT) models have shown potential to simulate such toroids, matching observations qualitatively. For week-scale early prediction of
flare-producing AR emergence, forward-integration of these toroids is necessary. This requires model initialization with a dynamically self-consistent MHD state-vector that includes
magnetic, flow fields, and shell-thickness variations. However, synoptic magnetograms provide only
geometric shape of toroids, not the state-vector needed to initialize MHD-SWT models. To address this challenging task, we develop PINNBARDS, a novel Physics-Informed Neural Network (PINN)-Based AR Distribution Simulator, that uses observational toroids and MHD-SWT equations to derive initial state-vector. Using Feb-14-2024 SDO/HMI synoptic map, we show that PINN converges to physically consistent, predominantly antisymmetric toroids, matching observed ones. Although surface data provides north and south toroids' central latitudes, and their latitudinal widths, they cannot determine tachocline field strengths, connected to AR emergence. We explore here solutions across a broad parameter range, finding hydrodynamically-dominated structures for weak fields (~2 kG) and overly rigid behavior for strong fields (~100 kG). We obtain best agreement with observations for 20-30 kG toroidal fields, and ~10 degree bandwidth, consistent with low-order longitudinal mode excitation. To our knowledge, PINNBARDS serves as the first method for reconstructing state-vectors for hidden tachocline
magnetic structures from surface patterns; potentially leading to weeks ahead prediction of
flare-producing AR-emergence.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Echoes of $R^3$ modification and Goldstone preheating in the CMB-BAO landscape
Tanmoy Modak
The $R^2$ and the single-field-like regime of $R^2$-
Higgs inflation are disfavored by the observed high spectral index $n_s$ from the combined
cosmic microwave background (CMB) and
baryon acoustic oscillation (BAO) measurements at the $\sim2\sigma$ level. The addition of a dimension-six $R^3$ term in the action helps alleviate this tension. We show that the parameter space accounting for the observed high $n_s$ also induces rapid Goldstone and
Higgs preheating. The preheating, especially from Goldstone modes, helps match the CMB and inflationary scales, which in turn supports the observed $n_s$.
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Solar and Stellar Astrophysics
Flux rope formation through flux cancellation of sheared coronal arcades in a 3D convectively-driven MHD simulation
Sondre Vik Furuseth and Guillaume Aulanier
Context. Space weather and its potential negative consequences for life on Earth has received increasing
attention in recent decades. Particularly predicting CME onset has become important from a security perspective. To predict CMEs, one must first understand the dynamics leading to pre-eruptive
magnetic field configurations such as flux ropes. Aims. In this study, we investigate the realistic formation of coronal flux ropes above the
solar photosphere. The aim is to find if and how flux ropes can form there, and how the formation is related to flux cancellation at the photosphere. Methods. We run a convective non-symmetric 3D radiative MHD simulation with the code Bifrost. A linear force-free field with sheared coronal arcades is slowly inserted in the 24Mmx24Mmx30Mm simulation box. After this, the self-consistent
stochastic plasma flows of the convection zone drive several small-scale flux cancellations and
magnetic reconnection, without external influence. Lagrangian markers called corks are used to track the dynamic
evolution of the
magnetic field. Results. Over a period of 2.5 h, a flux rope is generated with photospheric footpoints separated by up to 12Mm. The flux rope forms gradually through several individual events, such as slipping reconnection, U-loop emergence, and thick-photosphere tether-cutting reconnection. Conclusions. Flux ropes can be formed in the
solar atmosphere solely driven by convection and flux cancellations at the photosphere. However, not all flux cancellations contribute to the build-up of the flux rope, and some coronal reconnection events that do are not clearly related to flux cancellation. The formation process of flux ropes from coronal sheared arcades driven by convection is therefore more complex than in the original smooth flux cancellation model. But the end result is qualitatively the same. Flux cancellation works. A flux rope is formed.
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Astrophysics of Galaxies
BASS.L. Near-infrared Data Release 3: A Spectral Atlas and Characterization of AGN
Jarred Gillette, Michael J. Koss, Darshan Kakkad et al. (+18 more)
We present an analysis of near-infrared (NIR) emission-line properties, AGN diagnostics, and circumnuclear gas dynamics for 453 hard X-ray selected (14$-$195 keV) AGN from the BAT AGN Spectroscopic Survey (BASS) NIR Data Release 3 (DR3; $\langle z \rangle=0.036$, $z<1.0$). This
dataset is the largest compilation of rest-frame NIR spectroscopic observations of hard-X-ray-selected AGN and includes the full DR2 sample. Observations were obtained with VLT X-shooter, a multiwavelength (0.3$-$2.5$\mu$m) spectrograph ($R$ = 4,000$-$18,000), using a $\geq 2 \sigma$ detection threshold, enabling broad analysis of emission features. We find that NIR coronal lines, particularly SiVI $\lambda1.964$, are more reliable tracers of AGN luminosity than optical [OIII], showing a tighter correlation with hard X-ray luminosity ($\sigma=0.25$dex) than [OIII] $\lambda5007$ ($\sigma=0.55$dex). Broad Paschen lines (Pa$\alpha$ and Pa$\beta$) are detected in 12% of Seyfert 2 and 57% of Seyfert 1.9, consistent with previous hidden BLR studies. We introduce a refined NIR diagnostic diagram (FeII $\lambda1.257$$\mu$m/Pa$\beta$ and H$_2$ $\lambda 2.122$$\mu$m/Br$\gamma$) that effectively distinguishes AGN,
star-forming, and composite sources even when contamination limits individual diagnostics or only upper limits are available. Additionally, we find a moderate correlation ($p \approx 7.4 \times 10^{-3}$) between hot molecular gas mass (traced by H$_2$ 2.121$\mu$m) and X-ray luminosity, while its relation with Eddington ratio is weaker. The hot-to-cold gas mass ratio spans four orders of magnitude, averaging $\sim 3 \times 10^{-7}$, indicating diverse molecular gas excitation processes likely driven by
star formation and AGN feedback. Our results underscore the value of NIR spectroscopy in probing AGN activity, obscured BLRs, and the complex interactions between AGN and their circumnuclear environments.
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All authors Jarred Gillette, Michael J. Koss, Darshan Kakkad, Federica Ricci, Isabella Lamperti, Kyuseok Oh, Alejandra Rojas, Yaherlyn Diaz, Turgay Caglar, Kohei Ichikawa, Ignacio del Moral-Castro, Claudio Ricci, Ezequiel Treister, Franz E. Bauer, Richard Mushotzky, Mislav Baloković, Jakob S. den Brok, Benny Trakhtenbrot, C. Megan Urry, Fiona Harrison, Daniel Stern
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Comparing next-generation detector configurations for high-redshift gravitational wave sources with neural posterior estimation
Filippo Santoliquido, Jacopo Tissino, Ulyana Dupletsa et al. (+2 more)
The coming decade will be crucial for determining the final design and configuration of a global network of next-generation (XG) gravitational-wave detectors, including the Einstein
Telescope (ET) and
Cosmic Explorer (CE). In this study, and for the first time, we assessed the performance of various network configurations using neural posterior estimation (NPE) implemented in Dingo-IS-a method based on normalizing flows and importance sampling that enables fast and accurate inference. We focused on a specific science case involving short-duration, massive and high-
redshift binary black hole mergers with detector-frame chirp masses $> 100~\mathrm{M}_\odot$. These systems encompass early-Universe
stellar and
primordial black holes, as well as intermediate-mass black hole binaries, for which XG observatories are expected to deliver major discoveries. Validation against standard
Bayesian inference demonstrates that NPE robustly reproduces complex and disconnected posterior structures across all network configurations. For a network of two misaligned L-shaped ET detectors (2L MisA), the posterior distributions on luminosity distance can become
multimodal and degenerate with the sky position, leading to less precise distance estimates compared to the triangular ET configuration. However, the number of sky-location multimodalities is substantially lower than the eight expected with the triangular ET, resulting in improved sky and volume localization. Adding CE to the network further reduces sky-position degeneracies, and the better performance of the 2L MisA configuration over the triangle remains evident.
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All authors Filippo Santoliquido, Jacopo Tissino, Ulyana Dupletsa, Marica Branchesi, Jan Harms
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Quirks Live in Cool Universes
Pouya Asadi, Graham D. Kribs and Markus A. Luty
We demonstrate that cosmological observations place strong bounds on the reheat temperature $T_\text{RH}$ of the Standard Model (SM) in minimal models of `quirks' – heavy
fermions transforming under the SM gauge group together with a new non-Abelian gauge interaction with a confinement scale far below the mass of the
fermions. These models have unique
collider signals associated with the confining flux strings, which cannot break due to the large mass of the quirks. Our work shows that in these models $T_\text{RH} \lesssim \mathcal{O}(100)$ GeV for the entire `quirky' parameter space where the effects of the flux string are important. These bounds are in tension with most models of baryogenesis, showing that the discovery of quirks at
colliders can have far-reaching implications for cosmology. The bounds arise because the irreducible relic abundance of glueballs from UV freeze-in, combined with their long lifetimes, leads to constraints from the disruption of BBN, distortions of the CMB, excess $\gamma$-rays, an over-abundance of self-interacting dark matter, and contributions to $\Delta N_{\rm eff}$. The glueball freeze-in abundance has a strong dependence on $T_\text{RH}$, making the bounds relatively insensitive to strong interaction uncertainties. The bounds are robust to the SM
quantum numbers of the quirks and the presence of Yukawa couplings with the
Higgs. In non-minimal extensions of the model where the glueballs can decay to an additional dark sector, the bounds remain for models where the flux string has a macroscopic length at
colliders. We also show that for quirk masses above $\sim 10$ TeV, the dark glueballs can be the dominant component of dark matter. This work illustrates a striking connection between quirky
collider signals and cosmological probes of new physics, strengthening the case for targeted quirk searches at
colliders.
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Cosmology and Nongalactic Astrophysics
Dynamical Dark Energy models in light of the latest observations
Javier de Cruz Pérez, Adrià Gómez-Valent and Joan Solà Peracaula
In this paper, we study several models and parameterizations of dynamical dark energy (DE) that have been studied already in the past, in conjunction with the recently proposed model $w$XCDM, the running
vacuum model (RVM) with and without a threshold at $z=1$ and two variants of it, the RRVM and the “flipped RVM”, and compare them all with the concordance $\Lambda$CDM model and the popular $w_0w_a$CDM parameterization. We use two standard sets of cosmological data, one including distant
supernovae from Pantheon$+$ and the other from DES-Y5. The rest of the data (BAO from DESI DR2 and CMB from Planck PR4) are shared by the two sets. They are analyzed using the state-of-the-art techniques. No structure formation data are utilized for this analysis and no use is made of the SH0ES calibration of $H_0$. Even so, we find that the flipped RVM and to a lesser extent the $w$XCDM and the RVM with threshold, point to significant evidence of dynamical DE, at a level comparable to $w_0w_a$CDM, more conspicuously for the
dataset that involves DES-Y5 observations. We also find that while more traditional models studied in the past, in which there is an exchange between
vacuum energy and cold dark matter (through e.g. an interactive source proportional either to the density of dark matter or to that of
vacuum) still hint at dynamical DE, the strength of the statistical signal (which we assess through information criteria and other
estimators) is nevertheless less pronounced. Finally, we discuss the ability of the various models to explain the data by performing an analysis of their effective equation-of-state parameters and corresponding
evolution of their dark energy densities.
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High Energy Astrophysical Phenomena
The Sensitivity of PUEO to Cosmogenic Neutrinos and Exotic Physics Scenarios
Angelina Sherman, Ke Fang and Dan Hooper
Several observatories designed to detect ultrahigh-energy
neutrinos are planned for the next decade. The most imminent of these is the Payload for Ultrahigh Energy Observations (PUEO), a long-duration balloon-based experiment that will provide unprecedented sensitivity to
neutrinos with energies in the range of ~ 1 - 1000 EeV. In this work, we assess the scientific reach of PUEO. In particular, we evaluate the sensitivity of this observatory to cosmogenic
neutrinos and, in turn, to the
proton fraction of the ultrahigh-energy
cosmic-ray spectrum. We also consider the potential of PUEO to probe scenarios in which
neutrinos are produced through the decays of ultraheavy dark matter particles or are radiated from
cosmic strings. We find that PUEO will be able to constrain the
proton composition of ultrahigh-energy
cosmic rays in scenarios that feature very strong source
evolution and in which
protons are accelerated to extremely high energies. Although gamma-ray observations are generally more sensitive to decaying particles than
neutrino observations, PUEO is expected to set the strongest
neutrino-detector constraints above 10^19 eV. PUEO will also provide the strongest constraints on some models of
cosmic strings.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Signatures of High-Frequency Gravitational Waves in Electromagnetic Cavities
Sebastian Schenk, Kristof Schmieden and Pedro Schwaller
Similar to
axions, gravitational waves (GW) can induce oscillating electromagnetic fields inside electromagnetic cavities. We explore their experimental sensitivity to monochromatic and non-monochromatic GW signals, using the total deposited energy as a primary measure. Focusing on cylindrical and spherical cavities, we present the coupling coefficients of GWs to the dominant electromagnetic resonances in transverse-traceless gauge, which is most appropriate in this regime. By considering the superposition of degenerate modes, we further examine their angular sensitivity. In addition, we calculate the response of a spherical cavity to non-monochromatic GWs emitted by
primordial black hole mergers. We find that, for transient signals, a high quality factor with $Q \gtrsim 10^5$ does not necessarily enhance experimental sensitivity. In fact, even in the most optimistic scenario, only mergers within the
solar system yield an observable energy deposit in the cavity.
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Solar and Stellar Astrophysics
Revisiting the near infrared Calcium triplet as metallicity indicator
M. Navabi, R. Carrera, N. E. D. Noël et al. (+3 more)
The near-infrared Calcium II Triplet (CaT), around 850nm, is a key
metallicity indicator for red
giant stars. We present a revised [Fe/H] calibration as a function of CaT line strengths and four luminosity indicators, including the $Gaia$ $G$-band, together with the classical $V$, $I$, and $K_s$ bandpasses. For this purpose, we used a sample of 366 red
giant stars belonging to 25 globular and open clusters, complemented by 52 extremely metal-poor field
giant stars. The CaT line strengths are determined by fitting Gaussian-Lorentzian combination profiles using the Python lmfit package, which utilises the
algorithms implemented therein. The derived calibration is valid for a wide
metallicity range, $-4$\,dex$ \lesssim \mathrm{[Fe/H]} \lesssim +0.15$, and for ages older than $\sim$200 Myr. In addition, we performed a detailed assessment of how factors such as spectral resolution, spectral quality (expressed through the signal-to-noise ratio), and the
algorithms used to constrain the line profiles affect the measured line strengths and the resulting
metallicities.
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All authors M. Navabi, R. Carrera, N. E. D. Noël, C. Gallart, E. Pancino, M. De Leo
Astrophysics of Galaxies
Machine Learning vs. Spectral Energy Distribution Fitting: A Comparative Analysis of Accuracy in Stellar Mass Estimation
Vahid Asadi, Akram Hasani Zonoozi and Hosein Haghi
Traditional spectral energy distribution (SED)-fitting methods for
stellar mass estimation face persistent challenges including systematic biases and computational constraints. We present a controlled comparison of machine learning (ML) and SED-fitting methods, assessing their accuracy, robustness, and computational efficiency. Using a sample of COSMOS-like
galaxies from the Horizon-AGN simulation as a
benchmark with known true masses, we evaluate the Parametric t-SNE (Pt-SNE)
algorithm – trained on noise-injected BC03 models – against the established SED-fitting code LePhare. Our results demonstrate that Pt-SNE achieves superior accuracy, with a root-mean-square error (sigma_F) of 0.169 dex compared to LePhare's 0.306 dex. Crucially, Pt-SNE exhibits significantly lower bias (0.029 dex) compared to LePhare (0.286 dex). Pt-SNE also shows greater robustness across all
stellar mass ranges, particularly for low-mass
galaxies (10^9 to 10^10
solar masses), where it reduces errors by 47-53 %. Even when restricted to only six optical bands, Pt-SNE outperforms LePhare using all 26 available photometric bands, underscoring its superior informational efficiency. Computationally, Pt-SNE processes large
datasets approximately 3.2 x 10^3 times faster than LePhare. These findings highlight the fundamental advantages of ML methods for
stellar mass estimation, demonstrating their potential to deliver more accurate, stable, and scalable measurements for large-scale
galaxy surveys.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Non-equilibrium Quantum Field Theory and Axion Electrodynamics in curved spacetimes
Amedeo M. Favitta
Axions are hypothetical pseudoscalar particles introduced initially as a solution to the Strong CP problem in
Quantum Chromodynamics (QCD), and they also arise naturally in a broad class of low-energy compactifications of string theory. Astrophysical, cosmological, and laboratory constraints require
axions to be extremely weakly coupled to Standard Model particles, making them viable dark matter candidates .This PhD thesis presents original results developed over three years of research, focusing on
axion cosmology and
axion electrodynamics. These topics address the production of
axions and their associated topological defects in the early Universe, as well as the interactions of
axions with Standard Model particles. The analysis combines methods from non-
equilibrium quantum field theory and
quantum field theory in curved spacetimes. After reviewing the foundations of
quantum field theory in curved spacetimes and cosmology, the thesis introduces the Strong CP problem and the Peccei-Quinn mechanism, including the PQWW
axion model and its invisible extensions. Ultraviolet completions of QCD
axion theories are discussed in both field-theoretic and extra-dimensional frameworks. A significant part of the thesis is devoted to
axion electrodynamics, where a classical
axion background modifies Maxwell's equations and electromagnetic observables. The non-
equilibrium dynamics of self-interacting
axion fields coupled to the Standard Model or to a dark sector are also studied using the two-particle-irreducible effective action, and applied to pre- and post-inflationary cosmological scenarios, yielding new insights and preliminary constraints.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Cosmological consequences of spontaneous symmetry breaking
Giacomo Ferrante
The Standard Model of particle physics and the $\Lambda$CDM model of cosmology provide an incomplete description of our Universe. Both models face challenges, including explaining the nature of dark matter, the origin of the Universe's initial conditions, and the fine-tuning of the
Higgs boson mass. This thesis investigates the cosmological implications of spontaneous
symmetry breaking to address some of these issues, focusing on theories with a non-trivial
vacuum structure. We introduce a novel class of elementary scalars called ”accidents”, which emerge as accidentally flat directions in the
vacuum manifold: unlike Nambu-Goldstone
boson directions, accident directions are not related to any
symmetry. Radiative corrections induce a mass for the accidents that is one-loop suppressed with respect to naive expectations, making them naturally light. We propose that accidents can act as viable dark matter candidates, and as the inflaton driving
cosmic inflation. We construct a model of hybrid inflation in which the inflaton potential is an accident direction and is naturally flat. In models of accident inflation where the
vacuum manifold has a non-trivial
topology,
cosmic strings and domain walls form after the end of inflation. Such topological defects generate a
stochastic background of gravitational waves. Finally, we investigate the cosmological production of dark
magnetic monopoles. Focusing on 't Hooft-Polyakov monopoles from SO(3)$\rightarrow$SO(2)
symmetry breaking, we explore both second-order and first-order phase transitions, and we identify the regions of parameter space where the monopole relic density matches the one of dark matter. This model also features stable massive gauge
bosons. We find that the relic density of dark gauge
bosons is always far larger than the one of monopoles, concluding that dark monopoles cannot constitute a sizeable fraction of dark matter.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Calibration Method of Spacecraft-Inertial Sensor Center-of-Mass Offset for the Taiji Gravitational Wave Detection Mission under Science Mode
Haoyue Zhang, Dong Ye, Peng Xu et al. (+3 more)
Accurately calibrating the center-of-mass (CoM) offset between the spacecraft (SC) and the inertial sensor test mass (TM) is crucial for space-based gravitational-wave (GW)
antennas, such as LISA and Taiji. Current calibration methods require additional spacecraft maneuvers that disrupt science data continuity and inter-satellite links, compromising the coherence of gravitational wave signals. Here, we present a maneuver-free calibration scheme that directly estimates the CoM offset vector using only standard science-mode measurements from inertial sensors, interferometers, and differential wavefront sensors. By
embedding the CoM offset induced coupling acceleration as an extended state in a model-based adaptive Kalman filter, we achieve estimation accuracy of 0.01-1.5 mm across all axes with a maximum error below 1%. This approach enables continuous, high-precision calibration during nominal observation runs, ensuring continuous and coherent gravitational wave data collection while maintaining the required precision, and also facilitating advanced DFACS functions such as performance evaluations and fault diagnosis. For LISA-like missions, where data continuity is paramount for detecting faint gravitational wave signals, this method will enhance scientific output and reliability.
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All authors Haoyue Zhang, Dong Ye, Peng Xu, Yunhai Geng, Li-E Qiang, Ziren Luo
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Finite parts of inflationary loops II: A streamlined UV in-in algorithm and distinguishable signatures
Guillermo Ballesteros, Jesús Gambín Egea and Flavio Riccardi
We introduce a streamlined method for evaluating in-in loop integrals using dimensional regularization for diagrams with an arbitrary number of external legs and vertices, which complements earlier work and facilitates the extraction of the ultraviolet contributions. The method leads us to identify an apparent difficulty to renormalize with
Hamiltonian counterterms within the in-in formalism. We also discuss the importance of the finite parts of loop corrections that can be distinguished from their associated counterterm contributions. As an application, we examine the one-loop
primordial bispectrum in the context of the effective field theory of inflation, considering a specific set of interactions, and identifying a contribution distinguishable from its tree-level counterpart.
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High Energy Astrophysical Phenomena
The Indian Pulsar Timing Array Data Release 2: II. Customised Single-Pulsar Noise Analysis and Noise Budget
K. Nobleson, Churchil Dwivedi, Shantanu Desai et al. (+33 more)
We present the results of customised single-
pulsar noise analysis of 27 millisecond
pulsars from the second data release of the Indian
Pulsar Timing Array (InPTA-DR2). We model various
stochastic noise sources present in the
dataset using stationary Gaussian processes and estimate the noise budget of the InPTA-DR2 using
Bayesian inference, involving model selection,
Fourier harmonics selection, and parameter estimation for each
pulsar. We check the efficacy of our noise characterisation by performing the Anderson-Darling test for Gaussianity on the noise-subtracted residuals. We find that all 11
pulsars with time baseline $\lesssim2.5\,\text{yr}$ show Gaussian residuals and do not have evidence for any red noise process in the optimal model, except for PSR J1944$+$0907, which shows presence of DM noise. PSRs J0437$-$4715, J1909$-$3744 and J1939$+$2134 show preference for the most complicated noise model, having achromatic and chromatic red noise processes. Only 4 out of 15
pulsars with time baseline $\gtrsim2.5\,\text{yr}$ show significant non-Gaussianity in noise-subtracted residuals. We suspect that this may require more advanced methods to model noise processes properly. A comparative study of six
pulsars with data removed near
solar conjunctions showed deviations from the parameter estimates obtained with the original
dataset, indicating potential bias in red noise processes due to unmodeled
solar-wind effects. The results presented in this work remain broadly consistent with the InPTA-DR1 noise budget, with better constraints obtained on noise processes for several
pulsars and support for achromatic red noise in PSR J1012$+$5307 due to the extended time baseline.
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All authors K. Nobleson, Churchil Dwivedi, Shantanu Desai, Bhal Chandra Joshi, Himanshu Grover, Debabrata Deb, Vaishnavi Vyasraj, Kunjal Vara, Hemanga Tahbildar, Abhimanyu Susobhanan, Mayuresh Surnis, Aman Srivastava, Shubhit Sardana, Keitaro Takahashi, Amarnath, P. Arumugam, Manjari Bagchi, Neelam Dhanda Batra, Manoneeta Chakraborty, Shaswata Chowdhury, Shebin Jose Jacob, Jibin Jose, Shubham Kala, Ryo Kato, M. A. Krishnakumar, Kuldeep Meena, Avinash Kumar Paladi, Arul Pandian, Kaustubh Rai, Prerna Rana, Manpreet Singh, Jaikhomba Singha, Adya Shukla, Pratik Tarafdar, Prabu Thiagraj, Zenia Zuraiq
Cosmology and Nongalactic Astrophysics
From Cosmology to Cosmonomy
Emmanuel N. Saridakis
For most of its history, cosmology was a qualitatively constrained discourse on the universe, shaped by limited observational access and the absence of global dynamical laws. This situation has changed decisively in recent decades. Modern cosmology is now driven by an unprecedented flow of high-precision data from a wide range of independent probes, including the
cosmic microwave background, large-scale structure,
supernovae,
baryon acoustic oscillations, gravitational
lensing,
cosmic chronometers,
redshift-space distortions, gravitational-wave standard sirens, and emerging 21-cm observations, among others. This observational wealth is matched by a concrete theoretical and mathematical framework, based on general relativity, which provides the dynamical equations governing the
evolution of spacetime and matter at
cosmic scales. Combined with explicit background and perturbative equations, this framework enables quantitative, predictive, and falsifiable descriptions of
cosmic evolution. Thus, cosmology operates today as a nomological natural science of the observable universe, characterized by general laws, predictive power, and systematic empirical testing. We argue that this epistemic transformation motivates a corresponding conceptual shift, directly analogous to the historical transition from astrology to astronomy. In this sense, the transition from cosmology to cosmonomy should begin to be discussed among cosmologists, or, more precisely, among cosmonomers.
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Cosmology and Nongalactic Astrophysics
A Spectrum of Cosmological Rips and Their Observational Signatures
Mikel Artola, Ruth Lazkoz and Vincenzo Salzano
We present a unified dark energy framework capable of generating a continuous spectrum of cosmological “rip” scenarios – including the Big Rip, Grand Rip, Mild Rip, Little Rip, Little Sibling of the Big Rip, and the newly found Dollhouse Rip – while ensuring a physically consistent
evolution across
cosmic history. Building on earlier phenomenological proposals, we introduce a barotropic equation-of-state parameter with a sigmoid-like correction to guarantee a strictly positive dark energy density and to avoid early-time pathologies commonly present in previous models. Using this formulation, closed-form analytic expressions for the energy density can be obtained. This, in turn, enables a systematic classification of future singularities based on the signs and magnitudes of two key parameters of the model. We test these scenarios with state-of-the-art cosmological probes, including DESI DR2 BAO,
cosmic chronometers, CMB compressed likelihoods, and the Pantheon+
supernovae sample. According to our
Bayesian analysis, all rip scenarios yield best-fit parameters compatible with $\Lambda$CDM at the $1\sigma$ level, with Bayes factors weakly favoring $\Lambda$CDM. The mild, logarithmic
evolution of the proposed dark energy density prevents current observations from distinguishing among the different future fates. We conclude that, for rip cosmologies to gain observational support over $\Lambda$CDM, they must display more accentuated late-time dynamical features – such as perhaps rapid transitions or a phantom-divide crossing – within the
redshift range probed by present surveys.
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Astrophysics of Galaxies
The impact of selection criteria on the properties of green valley galaxies
Beatrice Nyiransengiyumva, Mirjana Povic, Pheneas Nkundabakura et al. (+2 more)
Context: The bi-modality in the distribution of
galaxies usually obtained from colour-colour or colour-
stellar mass diagrams has been studied to show the difference between the
galaxies in the blue cloud and in the red sequence and to define the green valley region. As a transition region, the green valley
galaxies can give clues about morphological transformation of
galaxies from late- to early-types, and therefore the selection of green valley is of fundamental importance. Aims: In this work, for the first time, we evaluate the selection effects of the most used green valley selection criteria. The aim is to understand how these criteria affect the identification of green valley
galaxies, their properties, and their impact on
galaxy evolution studies. Methods: Using the SDSS optical and GALEX ultraviolet data at
redshift z < 0.1, we selected the eight most commonly used criteria based on colours, specific
star formation rate, and
star formation rate vs.
stellar mass. We then studied the properties of the green valley
galaxies (their
stellar mass,
star formation rate, specific
star formation rate, intrinsic brightness, morphological and pectroscopic types) for each selection criterion. Results: We found that when using different criteria, we select different types of
galaxies. UV-optical colour-based criteria tend to select more massive
galaxies, with lower
star formation rates, with higher fractions of composite and elliptical
galaxies, than when using pure optical colours. Our results also show that the colour-based criteria are the most sensitive to
galaxy properties, rapidly changing the selection of green valley
galaxies. Conclusions: Whenever possible, we suggest avoiding the green valley colour-based selection and using other methods or a combination of several, such as the
star formation rate vs.
stellar mass or specific
star formation rate.
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All authors Beatrice Nyiransengiyumva, Mirjana Povic, Pheneas Nkundabakura, Tom Mutabazi, Antoine Mahoro
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Novel Light Dark Matter Detection with Quantum Parity Detector Using Qubit Arrays
Xuegang Li, Yuxiang Liu, Jing Shu et al. (+6 more)
We present the design and the sensitivity reach of the
Qubit-based Light Dark Matter detection experiment. We propose the novel two-chip design to reduce signal dissipation, with
quantum parity measurement to enhance single-
phonon detection sensitivity. We demonstrate the performance of the detector with full
phonon and quasiparticle simulations. The experiment is projected to detect $\gtrsim 30$ meV energy deposition with nearly $100\%$ efficiency and high energy resolution. The sensitivity to $m_\chi\gtrsim 0.01$ MeV dark matter scattering cross section is expected to be advanced by orders of magnitude for both light and heavy mediators, and similar improvements will be achieved for
axion and dark
photon absorption in the $0.04$-$0.2$ eV mass range.
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All authors Xuegang Li, Yuxiang Liu, Jing Shu, Ningqiang Song, Yidong Song, Junhua Wang, Yue-Liang Wu, Tiantian Zhang, Yu-Feng Zhou
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A non-compact QCD axion
Georgios K. Karananas, Mikhail Shaposhnikov and Sebastian Zell
We investigate the cosmology of an
axion that is fundamentally non-compact. During inflation, fluctuations of the effectively massless field populate many QCD
vacua, thereby evading conventional isocurvature constraints while generating domain walls – without accompanying
cosmic strings. A small non-QCD contribution to the
axion potential is required to trigger the timely collapse of domain walls; as a consequence, a residual amount of CP violation in the strong sector must exist, potentially within reach of planned experiments. Non-compact
axions can account for the entirety of the dark matter abundance, and the collapse of domain walls sources a
stochastic gravitational-wave background at nanohertz frequencies. Such
axion dynamics can be embedded in top-down constructions – such as Weyl-invariant Einstein-Cartan
gravity – where the tilting of the
axion potential arises automatically.
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Solar and Stellar Astrophysics
Presence of solar inner F-corona and coronal heating
Z.Q. Qu, R.Y. Zhou, H. Su et al. (+1 more)
A new source in
solar corona scattering photospheric and chromospheric Fraunhofer spectral lines is detected below a height of one
solar radius above
solar limb, consisting of tenuous and cool neutral atoms and much fewer once ionized ions. It is demonstrated via maps at the sample Fraunhofer lines within the band from 516.38 to 539.89nm, reconstructed from one set of spatially successive raster scanning data. The
dataset was obtained from a spectrograph during the total
solar eclipse on April 8, 2024, at Oden, Arkansas, USA. It is revealed from these maps that both the scattering and its spatial distribution depend on spectral lines, yielded from different ionization and excitation states of neutral metal atoms and ions. The distributions show asymmetry and feature of
diffusion originated from the photosphere and chromosphere. Ratio of the Fraunhofer line depth to the continuum intensity evaluated over the observational band peaks at 0.25$\%$ and has an average of 0.32$\%$. More discrete and weaker
diffusion of emission counterparts of some Fraunhofer lines are detected simultaneously. These properties are critically different from those owned by that F-corona yielded via
dust grain scattering beyond heights of about two and half
solar radii. Hence a term 'inner F-corona' is dubbed for the assembly of scattering by this new particle source. It becomes definite now that the
solar corona consists of not only free electrons and ions but also much fewer yet non-negligible neutral atoms. It is emphasized that global distributions of the outward neutral atom fluxes and coronal
magnetic loops can make the abnormal Cowling resistance the most primary mechanism responsible for the coronal heating, via collisions of the neutral atoms injected with ions in the coronal loops. This likes the heating process in Tokamak with neutral beam injection(NBI).
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All authors Z.Q. Qu, R.Y. Zhou, H. Su, Y. Liang
High Energy Astrophysical Phenomena
Super-Eddington Accretion through a Multiwavelength Lens: Searching for Counterparts of Ultraluminous X-ray Sources
R. Amato, M. Bachetti, R. Soria et al. (+8 more)
Ultraluminous X-ray sources (ULXs) represent the closest and most accessible laboratories to study sustained super-Eddington
accretion onto compact objects. Over the past decade, the discoveries of coherent pulsations in a few ULXs has proved that these systems can be powered by accreting
neutron stars, while the most luminous and distant ones remain strong candidates for hosting intermediate-mass black holes. Despite the increasing number of available X-ray data and the significant progress in theoretical modeling and simulations, our understanding of ULXs remains incomplete. Key open questions include the nature and mass distribution of the compact objects, the type of the donor
stars, the geometry of the
accretion disc and its contribution to the observed broadband emission, the mechanisms responsible for the wide spectral and temporal phenomenology, the duration of the super-Eddington
accretion phase and its feedback on the host-
galaxy environment. Future ground-based facilities will play a crucial role in addressing these issues.
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All authors R. Amato, M. Bachetti, R. Soria, A. Gúrpide, M. Imbrogno, C. Salvaggio, R. Salvaterra, M. Del Santo, S. Scaringi, P. Casella, A. Wolter
Instrumentation and Methods for Astrophysics
The AI Scaling Wall of Diminishing Returns: Of LLMs, Electric Dogs, and General Relativity
Hemant Shukla
LLMs are hitting the scaling wall - compute grows 10-100x while accuracy barely moves. This note quantifies the slowdown and argues that the next leap in AI will come not from bigger models, but from smarter, more efficient ones.
Astrophysics of Galaxies
How Mergers and Flybys Shape Azimuthal Age Patterns in Spiral Galaxies
Qian-Hui Chen, Alex M. Garcia, Zefeng Li et al. (+7 more)
Spiral structures are one of the most common features in
galaxies, yet their origins and
evolution remain debated.
Stellar age distributions offer crucial insights into
galaxy evolution and
star formation, though environmental effects can obscure the intrinsic age patterns. Using the Auriga cosmological gravo-magnetohydrodynamical zoom-in simulations, we investigate the azimuthal age distribution of young
stars (<2 Gyr) in a sample of five Milky Way-mass spiral
galaxies over the past 5 Gyr. We quantify the age gradients across spiral arms using the mean age offset (${\Delta}{\tau}$) and the non-overlap fraction ($f_{non-overlap}$). We further analyse the impact of mergers and fly-by events on the age gradients. Our results show that Auriga spiral
galaxies generally feature younger
stars in their leading edges compared to the trailing edges, with a typical ${\Delta}{\tau}$ between 30 and 80 Myr. However, gas-rich interactions can disrupt this age offset, resulting in similar age distributions on each side of the spiral arms. In three snapshots, we observe similar mean ages on both sides of spiral arms but differing age distribution broadness, coinciding with satellite interactions crossing the host
galaxy's disc plane. Our simulation data suggest that the typical azimuthal age variation recovers within ~600 Myr after
galaxy interactions. This work highlights the transient role of environmental interactions in shaping spiral arm age patterns.
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All authors Qian-Hui Chen, Alex M. Garcia, Zefeng Li, Kathryn Grasha, Emily Wisnioski, Paul Torrey, Rhea-Silvia Remus, Lucas C. Kimmig, Andrew J. Battisti, Sven Buder
Cosmology and Nongalactic Astrophysics
Decay of $f(R)$ quintessence into dark matter: mitigating the Hubble tension?
Giovanni Montani, Luis A. Escamilla, Nakia Carlevaro et al. (+1 more)
We propose a revised cosmological scenario that extends the $\Lambda$ Cold Dark Matter ($\Lambda$CDM) framework by incorporating metric $f(R)$
gravity in the Jordan frame. In this model, the dark energy component arises from a non-minimally coupled scalar field, decomposed into a smooth background (set to unity to recover General Relativity) and a rapidly varying, massive fluctuation that decays into the dark matter sector. In the near-GR limit, this setup provides a phenomenological extension of $\Lambda$CDM characterized by two additional parameters: the present-day value of the scalar fluctuation and a normalized decay rate. Using a Markov Chain Monte Carlo analysis of low-
redshift cosmological data, comprising Type Ia
Supernovae,
Baryon Acoustic Oscillation (BAO), and
Cosmic Chronometer measurements, we find that the proposed model achieves a better overall fit than $\Lambda$CDM, while the
Bayesian evidence remains statistically inconclusive given the inclusion of two extra parameters. The model predicts a moderate increase in the inferred value of $H_0$ and an improved consistency with DESI BAO data when adopting the SH0ES prior. Furthermore, describing dark matter particle creation as a transition phase in the late Universe offers an intriguing physical interpretation, potentially capturing features already present in current data and providing a promising avenue to explore extensions of the standard cosmological model within modified
gravity frameworks.
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All authors Giovanni Montani, Luis A. Escamilla, Nakia Carlevaro, Eleonora Di Valentino
Solar and Stellar Astrophysics
Deep learning-driven atmospheric parameter prediction for hot subdwarf stars with synthetic and observed spectra
Zhenxin Lei, Yangyang Dong, Bokai Kou et al. (+4 more)
We design a convolutional neural network (CNN) incorporating channel
attention and spatial
attention mechanisms to predict atmospheric parameters of hot subdwarfs. The experimental
dataset comprises spectra at nine distinct signal-to-noise ratio (SNR) levels, with each SNR level containing 11 396 synthetic spectra and 945 observed spectra. The trained deep learning models achieves mean absolute errors (AME) in predicting hot subdwarf atmospheric parameters of 730 K for effective temperature (Teff ), 0.09 dex for surface
gravity (log g), and 0.03 dex for helium abundance (log(nHe/nH)), respectively, which reaches the accuracy of traditional spectral fitting methods. Utilizing the trained deep learning models and low-resolution spectra from LAMOST DR12, we confirm 1512 hot subdwarfs from the catalog of hot subdwarf candidates, of which 291 are newly identified. Our results demonstrate that the deep learning model not only achieves accuracy comparable to traditional methods in obtaining hot subdwarf atmospheric parameters, but also far exceeds them in speed and efficiency, making it particularly suitable for the analysis of large
datasets of hot subdwarf spectra.
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All authors Zhenxin Lei, Yangyang Dong, Bokai Kou, Mengqi Feng, Ke Hu, Yude Bu, Jingkun Zhao
Solar and Stellar Astrophysics
Formation of an optically thick shocked shell in the very fast nova V1674 Herculis: the origin of superbrightness
Izumi Hachisu and Maiko Kato
V1674 Her is the fastest ($t_2\sim 1$ day) classical nova in our
Galaxy and its absolute $V$ peak of $M_{V,\rm max}\sim -10.2$ is one magnitude brighter than typical very fast novae. Such a nova is sometimes called a superbright nova. Using our fully self-consistent nova outburst model combined with the optically thick winds on a $1.35 ~M_\odot$ white
dwarf (WD) with a mass
accretion rate of $1\times 10^{-11} ~M_\odot$ yr$^{-1}$, we have clarified that a strong reverse shock arises $0.3$ days after the outburst, which is just after the maximum expansion of the WD photosphere. The shocked shell is optically thick and expanding with the velocity of $\sim 3500$ km~s$^{-1}$. Its $V$ brightness reaches maximum of $M_{V,\rm max}=-10.2$ when the shocked shell expands to $R_{\rm shell}\sim 300 ~R_\odot$ on day $\sim 0.7$. After that, the shocked shell turns to optically thin and becomes fainter than the brightness of free-free emission from the nova wind. In chronological order, the optical brightness of free-free emission reaches maximum of $M_V=-9$ on day 0.3. However, it is overtaken on day 0.5–0.7 by the $\sim$1 mag brighter luminosity of the optically thick shocked shell. The GeV gamma-ray flux reaches maximum on day 0.4 because the gamma-rays are emitted by the shock that arises on day 0.3. Our model consistently explains both the superbrightness and chronological order that the gamma-ray peak precedes substantially before the optical $V$ peak. We also present a similar light curve model for another superbright nova V1500 Cyg.
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