Astrophysics of Galaxies
Do time delay effects explain galactic velocity profiles?
L. Benkoula, K. Chima, J. Kingsbury et al. (+3 more)
Using the gravitoelectromagnetic analogy for weak gravitational fields, we critique explanations of
galactic velocity profiles that invoke time delay effects (i.e. "retarded
gravity"). For isotropic, time-dependent matter currents, we show within this framework that the force exerted on an orbiting body is Newtonian and due only to the instantaneous ambient matter configuration – there are no time delay effects in such situations.
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All authors L. Benkoula, K. Chima, J. Kingsbury, K. Marroquin, M. Yim, T. Curtright
Earth and Planetary Astrophysics
JWST Exoplanetary Worlds and Elemental Survey (JEWELS) II: Condensation Temperature Trends and Galactic Chemical Evolution in JWST Planet-Hosting Stars
Qinghui Sun, Xianyu Tan, Gordon Yip et al. (+4 more)
We present high-precision chemical abundances for 25 FGK-type
stars hosting
exoplanets observed in JWST Cycle 3 programs and all GTO and DDT programs from Cycles 1-3, based on high-resolution, high signal-to-noise ratio optical spectra from ground-based
telescopes. Using a strictly differential, line-by-line analysis relative to the Sun, we derive homogeneous
stellar parameters and abundances for 19 elements with atomic number Z <= 30. The sample spans a wide range of
stellar properties, with [Fe/H] = -0.6 to +0.4 dex and effective temperatures between 4700 and 6600 K, and includes hosts of terrestrial and
giant planets as well as multi-
planet systems. We refine carbon and sulfur abundances in cool
dwarfs using spectral synthesis, mitigating systematics from line blending. Several chemically interesting systems are identified, including mildly $\alpha$-enhanced metal-poor
stars and multi-
planet hosts with elevated [C/O]. Using isochrone ages, we derive empirical
Galactic chemical
evolution (GCE) relations and examine condensation temperature (Tcond) trends before and after GCE correction. The $T_{cond}$ slopes show no dependence on
stellar or planetary properties, indicating that they reflect a mixture of multiple mechanisms, with
planet-related signatures entangled in GCE and
stellar evolution effects. Thus, Tcond trends require careful interpretation. Several systems with significantly positive or negative Tcond slopes are identified. Together with forthcoming JWST atmospheric measurements, this homogeneous
stellar abundance catalog provides a basis for probing
star-
planet chemical connections and
planet formation pathways.
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All authors Qinghui Sun, Xianyu Tan, Gordon Yip, Zitao Lin, Fan Liu, Sharon Xuesong Wang, Zhengduo Li
Instrumentation and Methods for Astrophysics
Smokescreen: A Python package for data vector blinding and encryption in cosmological analyses
Arthur Loureiro, Jessica Muir, Jonathan Blazek et al. (+10 more)
Smokescreen is an open-source Python library for data-vector concealment (blinding) in cosmological analyses. Data-vector blinding works by applying cosmology-dependent shifts to the observed data vector, moving it away from the true cosmological signal without affecting its statistical properties, so that analysts cannot infer the true result until the analysis is frozen and the blinding is lifted. The package computes these shifts using Firecrown likelihoods applied to data vectors stored in the SACC format, ensuring that the theoretical model used for blinding is identical to that used for inference whilst remaining agnostic to the specific observable being blinded. To prevent accidental unblinding, the original SACC file, containing the true cosmology, is encrypted. Although developed for the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), Smokescreen is applicable to any experiment using Firecrown likelihoods and the SACC data format.
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All authors Arthur Loureiro, Jessica Muir, Jonathan Blazek, Nora Elisa Chisari, Pedro H. Costa Ribeiro, Christos Georgiou, C. Danielle Leonard, Bruno Moraes, Marc Paterno, Nikolina Šarčević, Tilman Tröster, Sandro D. P. Vitenti, the LSST Dark Energy Science Collaboration
Cosmology and Nongalactic Astrophysics
A barotropic alternative to Early Dark Energy for alleviating the $H_0$ tension
Youri Carloni and Orlando Luongo
We propose a cosmological scenario in which, beyond matter and radiation, an additional barotropic fluid with positive equation of state $\omega_s$ contributes to the
cosmic energy budget, in contrast to Early Dark Energy (EDE). We investigate the theoretical implications of this framework, here dubbed the $\Lambda_{\omega_s}$CDM model, at both the background and perturbative levels, exploring its impact on the expansion history and structure formation. We show that, while remaining subdominant at late times and therefore consistent with current observational bounds, the additional fluid modifies the early-time expansion rate, leading to a higher inferred value of the Hubble constant. Thus, we perform a full
Bayesian analysis using a modified version of the CLASS Boltzmann code interfaced with MontePython, considering combinations of Planck 2018
Cosmic Microwave Background (CMB) data, DESI DR2
Baryon Acoustic Oscillations (BAO) measurements, Pantheon Type Ia
supernovae (SNe Ia), and SH0ES determinations of $H_0$. We find that the inclusion of the SH0ES prior, $H_0 = 73.04 \pm 1.04\,\mathrm{km/s/Mpc}$, leads to a preference for a nonvanishing barotropic fluid. In particular, we obtain $\omega_s = 0.290^{+0.017(0.021)}_{-0.007(0.028)}$ and density $10^5\Omega_s = 1.47^{+0.35(1.14)}_{-0.62(0.94)}$ for the
dataset combination CMB + BAO + Pantheon + SH0ES, and $\omega_s = 0.302^{+0.024(0.034)}_{-0.013(0.038)}$ and $10^5\Omega_s = 1.21^{+0.31(1.10)}_{-0.65(0.86)}$ when BAO data are excluded. We further compare our scenario with the EDE framework and show that, statistically, no strong evidence is found against the $\Lambda_{\omega_s}$CDM model. Finally, we provide a physical interpretation of our fluid in terms of matter with pressure, indicating that the standard cosmological model may be incomplete in its current minimal formulation.
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High Energy Astrophysical Phenomena
X-Ray Polarization from the Atoll 4U 1735-44 Suggests a Low Inclination
M. A. Díaz Teodori, A. Bobrikova, A. Gnarini et al. (+17 more)
X-ray polarimetry is a new tool capable of probing the geometry of
accretion onto weakly magnetized
neutron stars. Here we present the first X-ray spectropolarimetric results from coordinated observations of the atoll source 4U 1735-44, conducted with the Imaging X-ray Polarimetry Explorer (IXPE), NICER, and NuSTAR. Over the 2-8 keV energy range, we obtained a marginal detection of polarization with the polarization degree of $1.4\%\pm0.7\%$ and polarization angle of $-29^\circ\pm14^\circ$, corresponding to a $3\sigma$ upper limit on the polarization degree of 3.5%. The best-fit model to describe the spectrum comprises a thermal component associated with the
accretion disk, a Comptonized blackbody component, and a relativistic reflection component. From the reflection model, we infer a disk inclination of $\sim 40^\circ$. The spectroscopic and polarimetric properties of 4U 1735-44 are consistent with those observed in other atoll sources studied by IXPE, with its low polarization likely due to its low inclination.
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All authors M. A. Díaz Teodori, A. Bobrikova, A. Gnarini, F. Ursini, S. V. Forsblom, J. Poutanen, A. Salganik, S. Bianchi, F. Capitanio, M. Cocchi, S. Fabiani, R. Farinelli, P. Kaaret, J. J. E. Kajava, G. Matt, M. Ng, S. Ravi, P. Soffitta, A. Tarana, S. Zane
Instrumentation and Methods for Astrophysics
The trigger and localization system of SVOM-GRM
Jiang He, Jian-Chao Sun, Yue Huang et al. (+20 more)
The Space multi-band Variable Object Monitor (SVOM) is an astronomical satellite jointly developed by China and France, primarily focused on the detection of gamma-ray bursts (GRBs) and transient sources. The SVOM satellite was launched on 22nd June, 2024 with four payloads installed onboard. As one of payload, GRM comprises 3 gamma-ray detectors (each detector has an effective area of approximately 200~cm$^{2}$) with distinct pointing directions, enabling the temporal and spectral measurements as well as localization of GRBs in the energy range of 15-5000 keV. This article firstly introduces the on-board localization
algorithm design for GRM and presents preliminary test results. Then, leveraging abundant ground-based computational resources, a joint fitting method for spectral and localization analysis using Monte Carlo Markov Chain (MCMC) is implemented. In contrast to the on-board localization
algorithm, the on-ground MCMC method comprehensively considers the influence of spectral characteristics, thereby mitigating systematic biases. Finally, a systematic analysis based on this method is provided, highlighting the localization and spectral measurement capabilities of GRM. The preliminary localization analysis result for the on-board detected GRB 240629A by both GRM and
Fermi/GBM shows that the localization result (error$\sim$4.14$^{\circ}$) of GRM is consistent with the
Fermi/GBM result.
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All authors Jiang He, Jian-Chao Sun, Yue Huang, Yong-Wei Dong, Shi-Jie Zheng, Xiao-Yun Zhao, Min Gao, Lu Li, Jiang-Tao Liu, Xin Liu, Hao-Li Shi, Li-Ming Song, Wen-Jun Tan, Bo-Bing Wu, Chen-Wei Wang, Jin Wang, Jin-Zhou Wang, Ping Wang, Rui-Jie Wang, Shao-lin Xiong, Juan Zhang, Li Zhang, Shuang-Nan Zhang
High Energy Astrophysical Phenomena
Superfluid $^3$He aerogel experiments as a laboratory neutron star analogue
Samuli Autti, Vanessa Graber and Brynmor Haskell
Neutron stars make a unique astrophysical test bench for our understanding of
quantum physics at kilometre scales. The rotation of a
neutron star features glitches, sudden
spin-ups that interrupt the otherwise regular
stellar spin-down, which are often attributed to the dynamics of pinned quantised
vortices in one or several of the superfluid phases inside the
star. Laboratory experiments probing superfluid
vortices have inspired
neutron star theory and simulations from the beginning. Here we argue that
vortex experiments in superfluids contained in aerogels show phenomenology that offers a highly appealing but vastly unexplored analogue for
neutron star physics. We build a point-
vortex simulation that allows analysing experiments in a crust-like and a core-like aerogel, extracting two different regimes of pinned
vortex (non-)dynamics and validating a microscopic picture of very strong
vortex pinning. In the crust-like aerogel,
vortices get depinned once the ambient superflow is fast enough, while in the core-like aerogel pinned
vortices are never released and rotational velocity changes are accommodated by the avalanche-like production of new
vortices instead. Finally, we show that these concepts should apply also in
neutron stars and may thus revolutionise the analysis of
neutron star observations.
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Cosmology and Nongalactic Astrophysics
In-depth analysis of the clustering of dark matter particles around primordial black holes. Part III: CMB constraints
Julien Lavalle, Vivian Poulin and Pierre Salati
In a mixed dark matter scenario in which
primordial black holes (PBHs) would co-exist with thermally produced self-annihilating particles, one expects the former to be surrounded by extremely dense
halos made of the latter, built up during radiation domination. Here, as a continuation of previous work, we derive observational limits on such a scenario from a full statistical analysis of
cosmic microwave background (CMB) data. We quantify how a tiny fraction $\fbh$ of PBHs could restrict the parameter space available to thermal particle dark matter, limiting the $s$-wave annihilation cross section to values $\lesssim 10^{-30}\,{\rm cm^3/s}\,(\mchi/100\,{\rm GeV})\,(\fbh/10^{-6})^{-3}$ if PBHs are typically heavier than $\sim 10^{-10}\,\Msun$, which can also be turned into constraints on PBHs in this mass range. In contrast, asteroid mass or lighter PBHs could live in perfect peace with these particles. Finally, we shortly discuss the implications of the recent tentative interpretation of Subaru-HSC microlensing events as PBHs.
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Cosmology and Nongalactic Astrophysics
Mapping the CMB with QUBIC spectral imaging
Alexandre Huchet, Tom Laclavère and Leonora Kardum
QUBIC, the Q & U Bolometric Interferometer for Cosmology, is a
telescope that observes the polarisation of the sky in the millimetre-wavelength range. Its goal is to detect the
primordial B-modes of polarisation in the
cosmic microwave background by combining the sensitivity of bolometers with the good understanding of interferometry systematics. This dual aspect of QUBIC allows it to perform spectral imaging, that is, obtaining spatial and spectral information of the sky simultaneously. This makes the separation of components with complex spectral energy distributions easier, hence improving the performance of foregrounds removal. We developed three different map making methods (frequency, component and neural network map making) that take advantage of these characteristics. Moreover, QUBIC resumed observing the sky early March and is continuing its commisioning phase with, namely, observations of the Moon.
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Cosmology and Nongalactic Astrophysics
Efficiently emulating distribution functions in gigaparsec volumes for varying cosmological parameters
Christopher C. Lovell, Max E. Lee, William J. Roper et al. (+4 more)
We present a new method for emulating the
halo mass function (HMF) and other distribution functions in large effective volumes, down to low
halo masses, whilst simultaneously modifying large ranges of parameters, for a fraction of the cost of traditional periodic cosmological simulations. We demonstrate the method by selecting small regions, $V \sim (50 \,h^{-1}{\rm Mpc})^3$, with a range of overdensities from the Quijote suite, consisting of tens of thousands of $(1 \,h^{-1}{\rm Gpc})^3$ $N$-body simulation volumes run with varying $\Lambda$CDM parameters. We train a differentiable emulator, conditioned on the overdensity of the region and these global parameters, to reproduce the
halo mass function in these regions. We then successfully recover the global distribution of
halo masses of the entire box by integrating over the overdensity distribution. Our approach uses just $\sim\,$0.026% of the original simulation volume, and suggests that suites of targeted `zoom' simulations, extracted from low resolution parent volumes, can be used to emulate large volume simulations at a fraction of the computational cost, whilst simultaneously pushing the dynamic range to much lower masses than can be achieved in periodic simulations. We discuss emulation of other key dark matter and baryonic distribution functions, as well as higher order statistics, with implications for the interpretation of upcoming wide field surveys on observatories such as Euclid, Roman and Rubin.
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All authors Christopher C. Lovell, Max E. Lee, William J. Roper, Daniel Anglés-Alcázar, Shy Genel, Shivam Pandey, Francisco Villaescusa-Navarro
Astrophysics of Galaxies
BEACON: JWST NIRCam Pure-parallel Imaging Survey. III. Constraints on the UV LF and the Clustering of z~7-14 Galaxies
Kimi C. Kreilgaard, Charlotte A. Mason, Takahiro Morishita et al. (+21 more)
The James Webb Space
Telescope (JWST) has extended the frontier of
galaxy detection to
redshifts z>11, finding a high abundance of UV-bright sources that challenge theoretical models. However, most current results come from just a few fields, introducing uncertainties due to
cosmic variance. Here, we constrain z~7-14 UV luminosity functions (LFs) over ~400 sq. arcmin across 36 independent sightlines from DR2 of BEACON, a JWST pure-parallel NIRCam multi-band imaging survey. We identify 164 7<z<12
galaxy candidates: 150 F090W-, 14 F115W-, and no robust F150W-dropouts. In the 11 pointings overlapping with public JWST spectroscopy, we find no contaminants, indicating a high purity in our sample. Our z~7.5 UV LF agrees with previous bright-end measurements but yields lower number densities at -21 < Muv < -19. At z~10, our measurements are lower than most photometric JWST results but match spectroscopic constraints, consistent with the high purity of our selection. The LFs at z~7.5 and z~10 are consistent with pre-JWST models, while our limits at z>13 do not rule out a possible excess. We measure significant clustering of bright (Muv<-20.5)
galaxies at 7<z<10. Fields hosting such sources are approximately three times more likely to be overdense relative to the full survey, implying that UV-bright
galaxies preferentially reside in the most massive
halos at these
redshifts. Comparing with semi-numerical simulations, we estimate that Muv < -20.5
galaxies inhabit
halos ~0.8 dex less massive at z~11 than at z~8, consistent with a shift to higher
star formation rates. However, their observed clustering exceeds predictions from pre-JWST luminosity-
halo mass relations, suggesting these sources reside in more massive
halos than previously modelled and/or multiple
halo occupation.
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All authors Kimi C. Kreilgaard, Charlotte A. Mason, Takahiro Morishita, Yechi Zhang, Viola Gelli, Nicha Leethochawalit, Tommaso Treu, Michele Trenti, Abdurro'uf, Hakim Atek, Maruša Bradač, Larry D. Bradley, Andrew J. Bunker, Novan Saputra Haryana, Matthew J. Hayes, Zhaoran Liu, Vihang Mehta, Marc Rafelski, Guido Roberts-Borsani, Claudia Scarlata, Massimo Stiavelli, Ryo A. Sutanto, Kosuke Takahashi, Benedetta Vulcani
Astrophysics of Galaxies
Vaulting the barrier: An intrinsic mechanism to fuel the gas beyond the nuclear ring into the central region of barred galaxies
Kotaro Kobayashi, Naomichi Yutani, Takayuki R. Saitoh et al. (+2 more)
Gas delivery to
galactic centers powers
nuclear starbursts and active
galactic nuclei (AGNs), yet bar-driven inflow is generally expected to stall in a
nuclear ring a few hundred parsecs across. Using three-dimensional Lagrangian hydrodynamic simulations in a fixed barred potential, we identify a bypass channel in which a fraction of the inflowing gas acquires vertical momentum, vaults across the ring, and reaches the inner few tens of parsecs. This pathway is absent in two-dimensional calculations, which instead predict long-lived stagnation at the ring. We find that the circumnuclear material within $\sim 50$ pc originates from gas initially located outside the ring ($\gtrsim 300$ pc), rather than from secondary inflow out of the ring itself. Successful delivery requires both a sufficiently large vertical excursion, $|z| \sim 100$ pc before encountering the ring, and substantial loss of azimuthal angular momentum $L_z$. The resulting inflow is organized rather than chaotic: center-reaching trajectories are confined to a limited spatial region set by the scale height of the ring gas. Most bar-driven gas still accumulates near the resonance and fuels
star formation in the
nuclear ring, but the vaulting stream selects a modest yet sufficient fraction that penetrates to the circumnuclear disk. These results suggest that intrinsically three-dimensional gas motions help link
nuclear starbursts, AGN fueling, and the frequent misalignment of
nuclear disks with respect to their host
galaxies.
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All authors Kotaro Kobayashi, Naomichi Yutani, Takayuki R. Saitoh, Junichi Baba, Keiichi Wada
High Energy Astrophysical Phenomena
Study on the detector energy response of SVOM/GRM
Xiao-Yun Zhao, Jiang He, Shi-Jie Zheng et al. (+32 more)
The SVOM mission is specifically designed to for the detection and localization of Gamma-Ray Bursts (GRBs) and subsequent follow-up observations. Among the four
telescopes installed on the SVOM satellite, the Gamma-Ray Monitor (GRM) plays a crucial role in capturing the
prompt emission of GRBs due to its wide field of view (FOV) and broad energy range. Accurate determination of the detector's energy response is vital for analyzing GRM data, particularly considering the significant impact of the atmospheric albedo effect on this response. This research focuses on deriving the detector's energy response and establishing a calibration database for the GRM, with particular emphasis on investigating the atmospheric albedo effect. The study shows that the contribution of albedo
photons to the detector's effective area depends strongly on the orientation of the GRD line of sight (LoS) relative to Earth and on the incident direction of the GRB. When the GRD LoS is anti-Earth oriented, the albedo effect is minimal, with the highest proportion of albedo effective area accounting for approximately 10% of the total effective area. This occurs when the incident angle of the GRB is nearly perpendicular to the LoS. Conversely, if the GRD LoS is not pointing away from Earth and the GRB arrives from angles greater than about 90$^{\circ}$, the albedo component can become predominant, contributing up to around 100% of the total effective area. This is especially pronounced in the 8-20 keV range, where the direct effective area drops to zero due to the large GRB injection angle. Our results show that, it is necessary for GRM to consider the atmospheric albedo effects in detector response, otherwise the spectral and localization analyses will result in biased measurements.
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All authors Xiao-Yun Zhao, Jiang He, Shi-Jie Zheng, Ping Wang, Shao-Lin Xiong, Yue Huang, Dong-Ya Guo, Juan Zhang, Rui Qiao, Hao-Li Shi, Lu Li, Li Zhang, Jin Wang, Meng Bai, Yong-Wei Dong, Min Gao, Louvin Henri, Ulysse Jacob, Yong-Ye Li, Jiang-Tao Liu, Xin Liu, Qing-Yun Mao, Frédéric Piron, Li-Ming Song, Rui-Feng Su, Jian-Chao Sun, Wen-Jun Tan, You-Li Tuo, Chen-Wei Wang, Jin-Zhou Wang, Rui-Jie Wang, Bo-Bing Wu, Wen-Hui Yu, Shuang-Nan Zhang, Shu-Min Zhao
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Probing Cosmic-Ray-Boosted and Supernova-Sourced Sub-GeV Dark Matter with Paleo-Detectors
Xiaoyong Chu, Yue-Lin Sming Tsai and Mei-Wen Yang
Astrophysical dark matter particles with masses well below GeV-scale can be difficult to detect using conventional
nuclear recoil experiments due to their low velocities in our Milky Way
halo. Elastic scattering with high-energy
cosmic rays or thermal production inside core-collapse
supernovae can accelerate sub-GeV DM to (semi-)relativistic velocities, producing
nuclear recoil energies above the keV threshold that paleo-detectors can record over geological timescales. Using olivine as the target with 100$\,$g$\cdot$Gyr exposure, we compute track length distributions from such (semi-)relativistic dark matter fluxes, incorporating all major backgrounds (
neutrinos, uranium-chain
neutrons, thorium
recoils) with a statistical analysis on an Asimov
dataset. We derive 95 C.L. projected sensitivity of paleo-detectors to the DM-nucleon cross section for dark matter masses between a few MeV and hundreds of MeV. Our results show that paleo-detectors are able to probe large parameter regions that are not covered by current and near-future experiments designed to detect dark matter and
neutrinos. In particular, paleo-detectors offer a unique ability to record the dark matter flux from
Galactic supernova events over geological times. Such cumulative exposure enables sensitivity gains of a few orders of magnitude compared to conventional experiments.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Including higher-order modes in a quadrupolar eccentric numerical relativity surrogate using universal eccentric modulation functions
Tousif Islam, Adhrit Ravichandran, Peter James Nee et al. (+15 more)
gwNRHME is a framework that converts multi-modal (i.e., containing several spherical harmonic modes) quasi-circular waveforms into their eccentric counterparts, provided the quadrupolar eccentric mode is known, by exploiting universal eccentric modulation functions. Leveraging this framework, we combine the quasi-circular NR surrogate model NRHybSur3dq8 with the quadrupolar, non-spinning, eccentric surrogate NRSurE\_q4NoSpin\_22 to construct a multi-modal, non-spinning, eccentric model, denoted as \model{}, which includes nine modes: $(2,\{1,2\})$, $(3,\{1,2,3\})$, $(4,\{2,3,4\})$, and $(5,5)$. When compared against 156 eccentric SXS NR waveforms, \model{} achieves median frequency-domain mismatches (computed using the Advanced LIGO design sensitivity) of $\sim 9\times 10^{-5}$, with a standard deviation of $\sim 2 \times 10^{-4}$. To demonstrate the modularity of the framework, we further combine NRSurE\_q4NoSpin\_22 with effective-one-body (EOB) models SEOBNRv5HM and TEOBResumS-Dali in their non-spinning limits, yielding eccentric waveforms with median mismatches of $\sim 2\times10^{-4}$ and $\sim 10^{-3}$, respectively, with standard deviation of $\sim 2 \times 10^{-3}$ and $\sim 2 \times 10^{-2}$ respectively. Finally, we provide both a surrogate model, gwEccEvolve\_q4NoSpin\_Sur, and an analytical model, gwEccEvNSv2, for the eccentricity
evolution up to $2M$ before merger, based on eccentricity definitions derived from the universal modulation functions. The gwNRHME framework is publicly available through the gwModels package, and the resulting waveform models will be released via the gwsurrogate package.
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All authors Tousif Islam, Adhrit Ravichandran, Peter James Nee, Scott E. Field, Vijay Varma, Harald P. Pfeiffer, Andrea Ceja, Noora Ghadiri, Lawrence E. Kidder, Prayush Kumar, Marlo Morales, Abhishek Ravishankar, Antoni Ramos-Buades, Katie Rink, Hannes R. Ruter, Mark A. Scheel, Md Arif Shaikh, Daniel Tellez
Earth and Planetary Astrophysics
Producing High-Resolution Martian Surface Temperature Maps Using VIR-TIR Relationships
Michael A. Frazer, Eriita G. Jones, Katarina Miljkovic et al. (+1 more)
Thermal infrared data (TIR; 8 - 15 $\mu m$) has a wide range of applications in Earth and planetary remote sensing. On Mars, this includes deriving thermal inertia (TI), which describes surface physical characteristics (e.g. particle size, degree of cementation) and is key for understanding geologic processes, assessing in-situ resource utilisation (ISRU) environments, and assisting mission planning. However, TI data from the THEMIS instrument is limited to 100 m/pixel resolution. Hyperspectral visible and near-infrared data (VIR; 0.5 - 5 $\mu m$) compliments TIR data by providing information on surface composition and is provided by the CRISM instrument at 12 m/pixel. In this work, we generate a machine learning regressor-based model to constrain relationships between THEMIS TI and CRISM VIR images at THEMIS resolution, and predict TI values from CRISM spectra with high accuracy (R2 $\sim$ 0.90, RMSE $\sim$ 23.6 TIU). We use the model to produce a downscaled TI map at a spatial resolution of 12 m/pixel, an order of magnitude finer than currently available, revealing decametre-scale features previously unresolved in THEMIS data.
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All authors Michael A. Frazer, Eriita G. Jones, Katarina Miljkovic, Gretchen K. Benedix
High Energy Astrophysical Phenomena
Rotation-induced Relaxation of Supernova Constraints on Axionlike Particles
Tsurugi Takata, Kanji Mori, Ko Nakamura et al. (+1 more)
We study how rotation modifies the constraints on MeV-scale
axion-like particles (ALPs) coupled to
photons derived from SN 1987A. We constrain the ALP parameter space based on both the energy-loss argument and the gamma-ray limits, and examine how these constraints are affected by
stellar rotation. Adopting initial angular velocities of ${\Omega}_{0} = 0.0 and 1.0 rad s^{-1}$ in the iron core, we carry out two-dimensional core-collapse
supernova simulations for three progenitor models - a $14 + 9M_{\odot}$ binary and $13M_{\odot}$ and $18M_{\odot}$ single
stars with
solar metallicity - and estimate ALP emission rates through post-processing. We find that rotation suppresses ALP emission by reducing the core temperature via centrifugal support. Rotation also reduces the
neutrino luminosity, but the suppression of ALP emission is more effective, leading to relaxed constraints within a simplified criterion based on the energy-loss argument. This relaxation is particularly pronounced in the rotating $18M_{\odot}$ model, where a substantial decrease in the central temperature occurs at $t_{pb} = 0.8 - 1 s$. In this simplified criterion, such rapid temporal variations in temperature indicate that the resulting constraints depend sensitively on both the evaluation time and the underlying
supernova model. For a gamma-ray limit from the SN 1987A observation, rotation has a negligible impact on the constraint. This is because the ALP-induced gamma-ray fluence observed at Earth is proportional to the fourth power of the ALP-
photon coupling constant, making the constraint relatively insensitive to the rotational suppression of ALP emission.
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All authors Tsurugi Takata, Kanji Mori, Ko Nakamura, Kei Kotake
High Energy Astrophysical Phenomena
Three Subclasses of the Intensity-tracking Pattern in Gamma-Ray Burst Spectral Evolution
Liang Li
The properties of the spectral
evolution during the
prompt emission phase of gamma-ray bursts (GRBs), which are closely related to the radiation mechanism (synchrotron or photosphere), are still a subject of debate. Two spectral
evolution patterns (“hard-to-soft” and “intensity-tracking”) have been commonly observed in GRB
prompt emission spectra. Here we present a well-defined sample of 20 single-pulse GRBs detected by
Fermi whose
prompt emission spectra exhibit the intensity-tracking pattern. By performing a time-resolved spectral analysis, we derive $E_{\rm p}$ and the energy flux $F$ from the same time bins and introduce a matched-bin lag, $t_{\rm lag}^{\rm F} \equiv t_{\rm p}(E_{\rm p})-t_{\rm p}(F)$, where $t_{\rm p}$ denotes the time at which each quantity reaches its maximum. We find that the intensity-tracking pattern subdivides into three distinct subclasses: Type I (5/20), with aligned $E_{\rm p}$ and flux peaks; Type II (13/20), with $E_{\rm p}$ peaking before the flux; and Type III (2/20), with $E_{\rm p}$ peaking after the flux. The early-peaking Type~II subclass dominates the sample. The subclasses also exhibit systematic differences in their spectral and temporal properties. Type II bursts are systematically harder than Type I, show broader flux pulses, and more often display asymmetric rising and decaying $E_{\rm p}$-$F$ branches. Type I is consistent with tightly coupled spectral and power
evolution, whereas Type II is more naturally explained by nonthermal or hybrid
prompt-emission scenarios in which spectral hardening precedes the peak radiative output. Type III appears to form a rare positive-lag tail whose physical origin remains uncertain.
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Solar and Stellar Astrophysics
The effect of interstellar scattering on coherent radio emission from stars: the case of CU Vir
J.S. Morgan, B. Das and H.E. Bignall
A subset of
magnetic stars exhibit periodic
radio pulses produced by the coherent electron cyclotron maser mechanism. These pulses are known to exhibit both temporal and spectral variations, which have been attributed to phenomena intrinsic to the
stellar magnetosphere. However, in order to fully characterise the
radio pulses and use them as magnetospheric probes (as suggested by past studies), it is also important to consider the effects of phenomena extrinsic to the magnetosphere. In this paper, we investigate whether interstellar scintillation could be a relevant mechanism for explaining spectral and temporal variations observed for coherent
stellar radio emission. For that, we consider the case of the well-characterised
magnetic hot
star CU Vir. At 400 MHz, coherent
radio emission from the
star was reported to exhibit a peculiar spectral
evolution that remains unexplained. We show that a plausible level of
turbulence along the line of sight can produce the observed phenomenon of spectral features. Our analysis shows that diffractive interstellar scintillation can have a strong effect on the observed dynamic spectrum of
radio emission from
stars, for an assumed size of the emitting region of $0.01r_\odot$, and that caution should therefore be taken in separating intrinsic and extrinsic features, particularly at low frequencies. These results are preliminary and further work is required to fully model the scintillation of ECME from
stars (in particular the change in source location with frequency), and to explore the full range of plausible scintillation parameters. We suggest how further observations may be used to test the interstellar scintillation hypothesis.
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Earth and Planetary Astrophysics · Cross-listed from physics.space-ph
Inferring lunar wake potentials from electron phase space densities
Xin An, Shaosui Xu, Vassilis Angelopoulos et al. (+4 more)
Inferring electric potentials from electron phase space density measurements in the lunar wake is complicated by two challenges: the asymmetry between the sunward and anti-sunward sides of the wake driven by the
solar wind strahl, and the presence of ion acoustic shocks in the central wake. We develop the
Hamiltonian inversion method, which infers the full spatial electric potential profile by exploiting the quasi-static Vlasov
equilibrium condition $f = f(H)$, where $H$ is the electron
Hamiltonian. The method addresses both challenges through a domain-decomposition strategy: on the two sides of the wake the potential is inferred independently by minimizing the misfit between the observed phase space density and a self-consistently reconstructed $f_\mathrm{interp}(\tilde{H})$, while in the central wake where flat-top trapped electron distributions are present the potential is inferred directly from the flat-top width. We validate the method against particle-in-
cell simulation data at two evolutionary stages of the lunar wake: an early stage where strahl asymmetry is strong but no shocks have formed, and a later stage where ion acoustic shocks and flat-top distributions are present. We then apply the method to two ARTEMIS lunar wake crossings at the same evolutionary stages, inferring normalized potential drops of $e\Delta\varphi/T_e \sim 15$ and $\sim 5$ respectively and capturing shock-associated potential enhancements in the central wake. The method is broadly applicable to
plasma environments where electrons are in quasi-static
equilibrium with a field-aligned electric potential.
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All authors Xin An, Shaosui Xu, Vassilis Angelopoulos, Terry Z. Liu, Andrew R. Poppe, Jasper S. Halekas, Ferdinand Plaschke
Earth and Planetary Astrophysics
A scaling relation for core heating by giant impacts and implications for dynamo onset
You Zhou, Peter E. Driscoll, Mingming Zhang et al. (+2 more)
Accretional heating of Earth's interior during formation is pivotal to its subsequent thermal and chemical
evolution. In particular, impact heating of Earth's core is expected, but its amplitude and radial distribution within the core is unknown and could influence the onset of the geodynamo. The uncertainty is due, in part, to the lack of constraints on the temperature of the interior following formation due to the difficulty of preserving a record of such a high energy environment, and the assertion that super-heating during formation would be rapidly lost through magma ocean cooling. Here we systematically investigate core heating due to
giant impacts using a Smoothed Particle Hydrodynamics (SPH) code with simulations spanning a range of impact angles, velocities, and masses. From these simulations we derive a scaling relation for core heating that depends on the impact parameters and predicts the radial core temperature profile following the impact. Our findings show that a significant amount of heat is deposited into the core, with a canonical impact scenario resulting in an average core temperature increase of about 3000 K, approximately 500 K higher than that of the overlying mantle. In this case the heat distribution within the the core produces a strong thermal stratification. We use a parameterized cooling model to estimate that the core could have cooled to an adiabatic state 290 Myr after a canonical impact, which is consistent with the observed time span between the age of the Moon and evidence for an active geodynamo.
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All authors You Zhou, Peter E. Driscoll, Mingming Zhang, Christian Reinhardt, Thomas Meier
Solar and Stellar Astrophysics
Exploring Polarized Millimeter Emission from Protoplanetary Disks with Irregular Dust Grains
Jesús Miguel Jáquez-Domínguez, Carlos Carrasco-González, Daniel Guirado et al. (+4 more)
Polarization at millimeter wavelengths provides a powerful diagnostic of
dust grain properties in protoplanetary disks. Standard models based on solid spherical grains often struggle to reproduce the observed polarization fractions and morphologies in systems where self-scattering is expected to dominate. We investigate the impact of grain morphology on polarized millimeter emission by comparing models that adopt solid spherical grains with models that employ solid irregular hexahedral particles drawn from the TAMUdust2020 database. Both grain populations share identical size distributions, enabling us to isolate the effects of geometry while preserving the same internal structure and material density. We explore three optical-depth regimes-optically thick, optically thin, and an intermediate hybrid case-to assess how grain morphology modifies the polarization structure under different conditions. For size distributions with $a_{\mathrm{max}} \sim \lambda / 2\pi$, where scattering-induced polarization is expected to peak, we find that the polarization morphology and fraction are nearly indistinguishable between spherical and irregular grains. The primary quantitative difference is an enhancement of the scattering opacity by up to a factor of $\sim 2.5$ for irregular particles, implying that disk
dust masses inferred under the assumption of spherical grains may be systematically overestimated. Irregular grains also suppress the polarization reversal predicted by Mie theory at large size parameters ($x>1$). Nevertheless, modifying grain geometry alone is insufficient to reproduce the observed polarization fractions within a pure self-scattering framework. These results suggest that additional physical effects, such as
dust porosity, warrant dedicated investigation.
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All authors Jesús Miguel Jáquez-Domínguez, Carlos Carrasco-González, Daniel Guirado, Olga Muñoz, Enrique Macías, Gonzalo Vargas, Julia Martikainen
Instrumentation and Methods for Astrophysics
Clock Noise Cancellation in Heterodyne Links between Optical Cavities for Space-Borne Gravitational-Wave Telescopes
Yutaro Enomoto, Subaru Shibai and Kiwamu Izumi
Space-borne gravitational-wave
telescopes are key to extend the observation band below $10\,\mathrm{Hz}$. The use of inter-satellite optical cavities linked by heterodyne interferometry is a promising approach to reach the sensitivity level of $10^{-22}/\sqrt{\mathrm{Hz}}$ in the decihertz band. While heterodyne interferometry is advantageous for relaxing arm-length control requirements, it introduces susceptibility to clock jitter, which can be a significant noise source. In the back-linked Fabry–Perot (BLFP) interferometer aiming at the decihertz band, the required clock stability exceeds that of current space-qualified oscillators by more than an order of magnitude. We propose a clock noise cancellation scheme that uses two heterodyne signals with positive and negative beat-note frequencies, naturally obtained using both incoming and outgoing
laser beams of arm cavities without additional clock modulation schemes. By forming a weighted combination of these signals with time-dependent coefficients, clock jitter contributions are eliminated while preserving gravitational-wave information. We present the theoretical framework, analyze performance under realistic arm-length drifts, and validate the approach through time-domain simulations using parameters from the B-DECIGO concept. Results show that the synthesized signal recovers the original sensitivity and even improves the signal-to-noise ratio by a factor of $\sqrt{2}$ for shot noise.
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Astrophysics of Galaxies
The Quenching Mechanisms of Field Dwarf Galaxies
Zuoyu Wu, Yougang Wang and Shihong Liao
Isolated
dwarf galaxies are intrinsically faint and difficult to detect. The limited sample size makes it challenging to observationally constrain the physical mechanisms that quench their
star formation. To disentangle the quenching mechanisms of isolated
dwarfs, we identify a non-negligible population of such
galaxies in the TNG50 simulation. In addition to the previously discovered “backsplash"
galaxies that were quenched by environmental effects when they were once satellites in more massive
halos, we find another primary quenching channel in a population of
galaxies whose
star formation is suppressed by excessively strong gas
outflows that prevent the gas from cooling and collapsing to form
stars. We further demonstrate that these
outflows are highly likely driven by
stellar feedback and predominantly occur in high-gas-fraction
dwarfs, which within our studied
stellar mass range ($10^7$–$10^{9.5},M_\odot$) are always located toward the low-mass end.
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Cosmology and Nongalactic Astrophysics
Testing cosmological isotropy with gravitational waves and gamma-ray bursts
Brian H. Y. Cheng, Donniel C. Cruz, Otto A. Hannuksela et al. (+18 more)
The cosmological principle asserts that the Universe is homogeneous and isotropic on large enough scales. However, alternative cosmological models can bring about anisotropies through local inhomogeneities, anisotropic
evolution, or exotic physics. In addition, select studies have also hinted at mild evidence of anisotropies in SNe Ia, CMB, and GRB data, though these remain unconfirmed. In this work, we test for cosmological anisotropies using gravitational waves and gamma-ray bursts, adopting the latest O4a release from the LIGO-Virgo-KAGRA collaboration and GRBWeb (including all known GRBs since 1991). If the cosmological principle holds, the sky localisation and the characteristics of the GRBs and GWs (masses, luminosities,
redshifts) should be statistically isotropic when corrected for selection biases. We employ a couple statistical methods, including angular power spectra and two-point correlation functions, and compare the results against synthetic data. The work extends previous analyses by including the most recent
datasets, and the use of multiple complementary statistical tests. We find no significant evidence for anisotropy in the current GW and GRB
datasets, consistent with the cosmological principle.
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All authors Brian H. Y. Cheng, Donniel C. Cruz, Otto A. Hannuksela, Davendra S. Hassan, Christian Heiderijk, Leo Q. Hu, Souvik Jana, Jinwon Kim, Albert K. H. Kong, Peony K. K. Lai, Samuel C. Lange, Samson H. W. Leong, Matteo Lulli, Li-Ting Ma, Paul Martens, Boris H-L. Ng, Thomas C. K. Ng, Surojit Saha, Gwangeon Seong, Helen Xian, Yanyan Zheng
Solar and Stellar Astrophysics
Spatio-temporal Characteristics of Very Long-periodic Pulsations in Solar Metrewave Bursts: Implications for their Origins
Dong Li, Lei Lu, Jingye Yan et al. (+5 more)
We traced the origin of very long-periodic pulsations (VLPs) in type-I burst chains on 2024 February 14. Seven successive and repetitive pulsation structures appeared in
radio dynamic spectra in the metric waveband, which were simultaneously measured by CBSm, DART, and MUSER-L. A quasi-period at about 160$^{+11}_{-6}$ s, determined by the fast
Fourier transform, was detected in the frequency range of about 210-280 MHz. Imaging observations from DART and SDO reveal that the type-I burst chains occur above two groups of sunspot umbrae connected by coronal loops. A quasi-period of approximately 170 s was also identified in the sunspot umbrae and coronal loops. The burst chains exhibit strong circular polarization and high brightness temperature, and they show spatiotemporal correlation with emerging
magnetic flux. The number densities at the loop top and double footpoints can produce
radio emission and generate type-I burst chains in the frequency range of 210-280 MHz. Our observations support the scenario that
plasma emission serves as the primary generation mechanism of type-I bursts, with VLPs most likely being modulated by the slow magnetoacoustic waves originating from sunspot umbrae. The observed frequency drift of burst chains may reflect the density attenuation along coronal loops.
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All authors Dong Li, Lei Lu, Jingye Yan, Xinhua Zhao, Bing Wang, Chengming Tan, Jianping Li, Zongjun Ning
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Thermodynamic behavior of cosmological models with fractional entropy
Miguel Cruz, Diego da Silva, Simón González et al. (+3 more)
We investigate the thermodynamic and phenomenological implications of a cosmological model governed by fractional
entropy applied to the apparent horizon of a flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe. By utilizing the unified first law of thermodynamics alongside the Kodama-Hayward temperature, we derive a generalized set of Friedmann equations characterized by a fractional parameter $\alpha \in (1,2]$. The thermodynamic analysis reveals that the specific heats $C_V$ and $C_p$ share the same sign and depend solely on the deceleration parameter, demonstrating that the fractional model is thermodynamically stable during the late-time accelerated expansion and does not exhibit phase transitions. To constrain the background dynamics, we confront the truncated fractional model with a joint sample of late-time observational data, including
Cosmic Chronometers, Pantheon+SH0ES
supernovae, and the latest DESI DR2
Baryon Acoustic Oscillations. Exploring the physically motivated range $1<\alpha\le 2$, we find that the fit quality degrades monotonically as $\alpha$ decreases from the General Relativity limit. Rather than limiting the model's physical value, this demonstrates its theoretical robustness: the fractional framework acts as a continuous deformation parameter that preserves macroscopic thermodynamic stability. The data favors $\alpha$ close to 2 (yielding $H_0=69.50\pm 0.42$ km/s/Mpc and $\Omega_{m0}=0.292\pm 0.008$), revealing that while the late-time background expansion strongly constrains deviations from the standard area law, the fractional model smoothly and stably accommodates these constraints without exhibiting thermodynamic pathologies.
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All authors Miguel Cruz, Diego da Silva, Simón González, Samuel Lepe, Joel Saavedra, Manuel Gonzalez-Espinoza