Cosmology and Nongalactic Astrophysics
GAME: Genetic Algorithms with Marginalised Ensembles for model-independent reconstruction of cosmological quantities
Matteo Peronaci, Matteo Martinelli and Savvas Nesseris
Genetic
Algorithms (GA) are a powerful tool for
stochastic optimisation and non-parametric symbolic regression, already widely used in cosmology. They are capable of reconstructing analytical functions directly from data points without introducing new physical models. A limitation of this approach is that while the reconstructed function is very efficient at reproducing the behaviour of the data points, non-observable quantities involving derivatives are particularly sensitive to stochasticity, hyperparameters, and to the choice of the best-fit function obtained by the GA, which implies the risk of the
algorithm getting stuck in a local minimum. In this work we propose an update to the GA methodology for the reconstruction of analytical functions that involves computing a weighted average of an ensemble of GA configurations (GAME). We define the weights via a quantity that accounts for both the goodness-of-fit of the points and the smoothness of the resulting function. We also present a practical method to analytically estimate and correct the errors on the averaged function by combining a path-integral approach with an ensemble variance. We demonstrate the improvement offered by GAME methodology on a generic test function. We then apply the new methodology to a non-parametric reconstruction of the Hubble rate $H(z)$ using
Cosmic Chronometers data and, assuming a flat Friedmann-Lemaître-Robertson-Walker background and General Relativity, we infer the corresponding dark energy equation of state $w(z)$. Through consistency tests, we show that current data produces results compatible with $\Lambda$CDM, and that Stage IV cosmology surveys will allow GA reinforced with GAME methodology to become an even more competitive tool for discriminating between different models.
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Solar and Stellar Astrophysics
BSN-VI: Multiband Light Curve Modeling of Four W UMa-Type Contact Binaries I. Revisiting Energy Transfer Mechanisms and Luminosity Behavior
Elham Sarvari, Atila Poro, Raul Michel et al. (+5 more)
We presented the first high-precision, detailed photometric analysis of four W Ursae Majoris (W UMa)-type contact binaries, Linear 10772300, Linear 11150338, Linear 20372537 and DM Cir. In addition to ground-based multiband photometric observations, data from the Transiting
Exoplanet Survey Satellite (TESS) were employed for the analysis of the DM Cir system. New ephemeris and linear fit to the O-C diagrams were derived using extracted times of minima and additional literature. The light curve modeling was performed using the PHysics Of Eclipsing BinariEs (PHOEBE) Python code and the BSN application, employing a Markov Chain Monte Carlo approach. In each systems, the two
stellar components exhibited minimal temperature differences ($\Delta T<150$ K), confirming efficient energy exchange within their common convective envelopes. Absolute parameters were estimated using the
Gaia Data Release 3 (
Gaia DR3) parallax and astrophysical equations. Based on effective temperatures and component masses, two systems were classified as W-subtype systems, while others belonged to the A-subtype. We computed the initial masses of the primary ($M_{1i}$) and secondary ($M_{2i}$) components for four target systems using a method based on the observational properties of overluminous secondary components. We found initial primary masses in the range 0.6-1.0$M_\odot$ and initial secondary masses in the range 0.9-1.7$M_\odot$ with mass loss $<1.0M_{\odot}$. We investigated the relative energy transfer rates ($U_{1}$ and $U_{2}$) and
nuclear luminosities ($L_{10}$ and $L_{20}$) based on the physical parameters of 411 W UMa-type contact binaries, including the four systems analyzed in this study, through wide range of mass ratios. The results for all systems provided a comprehensive view of energy transfer behavior throughout different evolutionary stages of contact binaries.
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All authors Elham Sarvari, Atila Poro, Raul Michel, Anna Francesca Pala, Mehmet Tanriver, Ahmet Bulut, Ahmet Keskin, Mark G. Blackford
Cosmology and Nongalactic Astrophysics
Constraining Axion-like Particles through Multi-epoch Monitoring of Strong Gravitational Lenses
Shivani Deshmukh, Aritra Basu, Dominik J. Schwarz et al. (+2 more)
We present new constraints on ultralight
axion-like particles (ALPs) through multi-epoch measurements of differential birefringence induced due to a coupling ($g_{a\gamma}$) between the ALP and electromagnetic fields. Broadband polarimetric observations in the 2-8 GHz range of the gravitationally lensed system CLASS B1152+199 were carried out over five epochs spanning three months with a cadence of roughly 20 days, and the differential birefringence angle ($\Delta\,\theta_{a,{\rm lens}}$) between the lensed images were estimated. We also combined an archival observation that effectively increases the span to 9.5 yr to probe the effect of an oscillating ALP field imprinted as oscillating $\Delta\,\theta_{a,{\rm lens}}$ over time. Here we present a new technique for combining multi-epoch measurements of $\Delta\,\theta_{a,{\rm lens}}$ by considering the coherence of the ALP field, such that, $\Delta\,\theta_{a,{\rm lens}}$ over these observations are related. The time scale of coherence depends on the mass of the ALP field ($m_a$). Our results are consistent with non-detection and we constrain $g_{a\gamma} \leq 7.8\times 10^{-12} \,\left( {\rho_{a,\text{em}}}/{20 \text{ GeV cm}^{-3}} \right)^{-1/2}\;\mathrm{GeV}^{-1}$ to $\leq 3.2\times 10^{-8} \,\left( {\rho_{a,\text{em}}}/{20 \text{ GeV cm}^{-3}} \right)^{-1/2}\;\mathrm{GeV}^{-1}$ at 95% confidence for $m_a$ between $1.6\times 10^{-22}\;\mathrm{eV}$ and $3.8\times 10^{-18}\;\mathrm{eV}$, where $\rho_{a,{\rm em}}$ is the density of the ALP field at emission. This improves over the constraint provided by the CERN
Axion Solar Telescope by up to an order of magnitude in the $m_a$ range $1.6\times 10^{-22}\;\mathrm{eV}$ to $3\times 10^{-21}$ eV.
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All authors Shivani Deshmukh, Aritra Basu, Dominik J. Schwarz, Yuko Urakawa, Sui Ann Mao
Astrophysics of Galaxies
The optical-infrared relation for active galactic nuclei: The role of contaminations
Mateusz Rałowski, Krzysztof Hryniewicz, Katarzyna Małek et al. (+2 more)
The main objective is to calibrate the OPT-IR luminosity relation for
quasars, focusing on accurate estimations of dusty
torus and
accretion disk luminosities. We analyzed contaminations related to host
galaxies, particularly from polar
dust, the interstellar medium, and
stellar emission that affect the optical and infrared. We used a sample of nearly 400
quasars with photometrical observations and spectroscopical
redshift divided into four
redshift bins (0.7-2.4). Full spectral energy distribution (SED) fitting was performed with the CIGALE code, and results were compared with simplified photometric luminosity estimates. The impact of non-active
galactic nucleus components and the role of polar
dust in the fitting process were assessed. We show that for sources with a disk luminosity above 10^45 [erg/s], the photometric estimates are consistent with SED-based values. While polar
dust contributes marginally to luminosity, its presence significantly alters SED fitting, particularly the
torus opening angle and cold
dust properties. In the optical domain,
stellar emission is the dominant contamination. In the infrared, disk emission and cold
dust play major roles. We propose two empirical calibrations for the OPT-IR relation. We conclude that the optical band is dominated by the
accretion disk component above 10^45 or 10^46 [erg/s] depending on
redshift, while IR luminosity is dominated by the dusty
torus emission above 1.6 $\times$ 10^45 or 2 $\times$ 10^46 [erg/s] depending on the
redshift. In this high-luminosity regime, simplified photometric methods yield reliable disk and
torus luminosity estimates. The aim of the analysis we present is to test the parameter space in order to build a well behaving OPT-IR nonlinear luminosity relation for
quasars that could serve as a cosmological probe.
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All authors Mateusz Rałowski, Krzysztof Hryniewicz, Katarzyna Małek, Agnieszka Pollo, Guido Risaliti
High Energy Astrophysical Phenomena
Constraints on GRB Jet Properties from IceCube Upper Limits: Insights from GRB 221009A and GRB 240825A
Chiranjeet Pradhan, Khushboo Sharma, Abhijit Roy et al. (+1 more)
The IceCube
neutrino telescope has provided upper limits on
neutrino emission from gamma ray bursts. These constraints provided by the IceCube detector have been instrumental in investigating the properties of the GRB jet and its emission models. During the
prompt phase of gamma ray burst emission, intense radiation components are generated that interact with the shock-accelerated particles within the jet. We study various GRB emission models, such as the internal shock model, the photospheric models, and also include a model-independent case. Based on these models, we calculate the
neutrino fluence using the photo-hadronic interaction process. We estimate the bulk Lorentz factor using the well-known correlations between
prompt phase observables, which is then used to calculate the emission site for the model-dependent scenarios. For GRB 221009A, we find that a low
baryon loading scenario is consistent with the IceCube upper limits; however, for GRB 240825A, a higher value of
baryon loading is preferred. Also, the values of the microphysical parameters $\epsilon_e$ and $\epsilon_B$ for GRB 240825A are lower by factors of approximately 10 and 100, respectively, compared to those of GRB 221009A. Further, using
neutrino upper limits for these two sources, we estimate the lower limits on the dissipation radius for our models. The current TeV PeV upper limits for GRB 221009A are already useful for constraining parameter space for the BPH and MPH models.
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All authors Chiranjeet Pradhan, Khushboo Sharma, Abhijit Roy, Jagdish C. Joshi
Cosmology and Nongalactic Astrophysics
On The Stability Of $H_0$ And The Inverse Distance Ladder
B. Popovic and M. Sullivan
The `Inverse Distance Ladder' uses relative-distance measurements with type Ia
supernovae (SNe Ia), anchored to an absolute distance scale from
Baryon Acoustic Oscillations (BAO) and the
cosmic microwave background (CMB), to provide an alternative measurement technique for the local expansion rate $H_0$. Using SNe Ia from the Dark Energy Survey and BAO measurements from the Dark Energy Spectroscopic Instrument, we show that the inverse distance ladder is unable to explain the Hubble Tension, anchored as it is to the CMB and its value of $H_0 = 67.4 \pm 0.5$ kms$^{-1}$ Mpc$^{-1}$. To do so, we first show that the suite of systematics considered in cosmology analyses with SNe Ia only move the inferred $H_0$ by $<0.1$kms$^{-1}$ Mpc$^{-1}$, and second, we investigate the scale of
redshift-dependent magnitude changes necessary to change the inferred inverse distance ladder $H_0$ from $67$ to the local network of distance measurements value of $73$, and the impact that this would have on other cosmological inferences with SNe Ia. We find that a change of $d\mu/dz = 0.2$ mag would be necessary to infer an $H_0$ in concordance with local distance measurements, and that this $d\mu/dz$ value would result in a Flat $\Lambda$CDM $\Omega_M = 0.23$, $10\sigma$ discrepant with other cosmological probes, {indicating that the precision of SNe Ia measurements preclude the necessary
redshift evolution for an $H_0$ of 74 kms$^{-1}$ Mpc$^{-1}$}. Therefore, we conclude that current SN Ia cosmology leaves little freedom for the inverse distance ladder to yield $H_0$ values significantly different from $67$ kms$^{-1}$ Mpc$^{-1}$.
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High Energy Astrophysical Phenomena
X-ray line diagnostics of the multi-phase gas in the Centaurus cluster core with XRISM/Resolve
Marie Kondo, Kotaro Fukushima, Kazunori Suda et al. (+18 more)
We report the multi-temperature structure of the intracluster medium (ICM) in the Centaurus cluster core observed with XRISM/Resolve. Thanks to its high energy resolution, Resolve enables us to measure fine structures of highly ionized emission lines from Si to Fe and to directly determine the excitation temperature and the ionization temperature from the emission line ratio diagnostics. The observed spectrum in the Centaurus core is well-represented by a double-temperature thermal
plasma at collisional ionization
equilibrium state rather than an isothermal one. The line ratio diagnostics also support this biphasic temperature structure. Particularly, the observed line ratios show a trend of increasing ionization temperature with atomic mass, while the ionization and excitation temperatures of Fe show nearly the same temperature. The resultant line ratios, which are well-represented by the two temperatures ICM, ~ 1.6 and ~ 3 keV, are also fairly consistent with the expected numbers when assuming the radial single-temperature ICM was projected in the cluster core along the line of sight. Due to the limited low-energy sensitivity of the Resolve with the gate valve closed, we investigated the effect of the cool component using the XMM-Newton/RGS spectrum, but it ultimately did not affect our results. The observed flux ratio between the Fe XXV He alpha resonance and forbidden lines shows an about 20% reduction, suggesting the presence of resonant scattering.
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All authors Marie Kondo, Kotaro Fukushima, Kazunori Suda, Anwesh Majumder, Kosuke Sato, Kyoko Matsushita, François Mernier, Kazuhiro Nakazawa, Aurora Simionescu, Jean-Paul Breuer, Yasushi Fukazawa, Ryuichi Fujimoto, Isamu Hatsukade, Kokoro Hosogi, Michael Loewenstein, Tom'aš Plšek, Ming Sun, Misaki Urata, Norbert Werner, Noriko Y. Yamasaki, Yutaka Fujita
Instrumentation and Methods for Astrophysics
CHIME/Slow overview and pilot survey: A new backend to search for second-duration radio transients with the CHIME telescope
Sujay Mate, Kevin Luke, Yash Bhusare et al. (+23 more)
We present an overview of CHIME/Slow, a real-time transient search backend under development to search for second-duration
radio transients using the CHIME
telescope, and results obtained from a pilot survey carried out using the prototype version of the search pipeline. The prototype CHIME/Slow pipeline was tested on archival data obtained in December 2022, January 2023 and February 2023 with a total on-sky time of 17 days with an instantaneous Field of View (FoV) of $\sim$13 deg$^2$ . In this pilot survey, we detected nine bursts, one from a new non-repeating source and eight from the known hyperactive repeating source FRB 20220912A. Out of these nine bursts, two bursts from the repeater were not detected by CHIME/FRB, while the non-repeater was detected in the side-lobe of a beam in the CHIME/FRB exhibiting shorter pulse width and narrower bandwidth compared to the CHIME/Slow detection. Here we report properties of the bursts, discuss the sensitivity and completeness of the current version of the CHIME/Slow pipeline, and outline future development to improve its performance. Finally, based on these results, we report the all-sky rate (95% credible region) of
radio transients with pulse widths between 16 ms to 5 s, fluence above 5 Jy ms and observing frequency of 600 MHz to be between 184 and 4556 bursts sky$^{-1}$ day$^{-1}$.
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All authors Sujay Mate, Kevin Luke, Yash Bhusare, Arvind Balasubramanian, Ziggy Pleunis, Paul Scholz, Shriharsh P. Tendulkar, Mohit Bhardwaj, Charanjot Brar, Fengqiu Adam Dong, Emmanuel Fonseca, B. M. Gaensler, Jason Hessels, Jeff Huang, Naman Jain, Ronniy C. Joseph, Victoria M. Kaspi, Afrokk Khan, Robert Main, Bradley W. Meyers, Nikola Milutinovic, Kenzie Nimmo, Kaitlyn Shin, David Spear, Ingrid Stairs, Chia Min Tan
Astrophysics of Galaxies
Tracking the dynamical, chemical and spectral evolution of molecular cores with PrestaLine: Gorynych
Olga Kochina, Dmitri Wiebe, Yaroslav Pavlyuchenkov et al. (+1 more)
We present PrestaLine: Gorynych, a comprehensive numerical tool designed to model the dynamical, chemical, and spectral
evolution of collapsing molecular cores from the prestellar phase to protostellar
accretion. The code integrates three key components: (1) Kamelung, a 1D hydrodynamics module simulating gravitational collapse up to first hydrostatic core (FHSC) formation followed by an
accretion of envelope onto a young
star; (2) Presta, a chemical
evolution module post-processing density and temperature profiles to compute time-dependent molecular abundances; and (3) Uran(IA), a radiative transfer module generating synthetic molecular line spectra. We apply Gorynych to compare low-mass (5 Msun) and high-mass (50 Msun) cores, finding that their dynamical
evolution is remarkably similar, with differences primarily in spatial scaling. Chemical
evolution reveals sharp abundance changes during the FHSC transition, particularly for CO, H2O, and HCO+, though pre-collapse chemical initialization has minimal impact on most species. Spectral maps of 13CO(2-1), HCO+(3-2), and H2O(110–101) lines show distinct kinematic signatures of infall and depletion, with high-mass cores exhibiting spatially extended emission. Our results highlight Gorynych's utility to couple theoretical collapse models and observations, providing a framework to diagnose core
evolution and initial conditions from molecular line data.
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All authors Olga Kochina, Dmitri Wiebe, Yaroslav Pavlyuchenkov, Maria S. Kirsanova
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Statistics of time and frequency-averaged spectra in gravitational-wave background searches
Quentin Baghi, Nikolaos Karnesis and Jean-Baptiste Bayle
Time series analysis from gravitational-wave detectors often relies on the assumption that time chunks, or frequency bins, are uncorrelated. We discuss the validity of this approximation in the context of searches for
stochastic gravitational-wave backgrounds. We examine the impact of averaging over time and frequency, a reduction technique commonly employed to minimize the computational expense of likelihood evaluations. We introduce an analytical tool based on Fisher information to quantify the error in parameter inference arising from ignoring these effects. Finally, we address the issue of locally stationary processes and optimal time chunking.
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Solar and Stellar Astrophysics
A rotational line CO cooling rate prescription for AGB outflows
T. Ceulemans, F. De Ceuster, O. Vermeulen et al. (+1 more)
Asymptotic
Giant Branch (AGB)
stars significantly contribute to the chemical composition of the universe. In their
outflows, complex chemistry takes place, which critically depends on the local temperature. Therefore, if we want to accurately model the AGB environment, we need accurate cooling rates. The CO molecule is abundant in AGB
outflows, and has a dipole moment, which enables it to cool through emission from its rotational transitions. We therefore expect it to significantly contribute to cooling in this environment, even at low temperatures ($10$ K $\leqslant T\leqslant 3000$ K). Currently, CO cooling rates are available for ISM-like conditions, which encompasses a different parameter regime, with generally lower densities and velocity gradients, compared to AGB winds. Therefore, these ISM cooling rates might not be applicable to the AGB regime. In this paper, we compute CO cooling rates for hydrodynamics simulations of AGB
outflows. To evaluate the net cooling rate, we calculate the energy level distribution of CO self-consistently, using the non Local Thermodynamical
Equilibrium (NLTE) line radiative transfer code Magritte. We verify whether already existing CO cooling rate prescriptions for the interstellar medium (ISM) are applicable for this regime. We noticed minor differences between these prescriptions and our calculated cooling rates in general. However, when used far outside their originally intended parameter regimes, significant differences occur. Therefore, we propose a new CO cooling rate prescription for the AGB environment and we study how the computed cooling rate varies depending on input parameters.
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All authors T. Ceulemans, F. De Ceuster, O. Vermeulen, L. Decin
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Big Bang Nucleosynthesis and the Neutrino-Extended Standard Model Effective Field Theory
Pieter Braat, Jordy de Vries, Jelle Groot et al. (+2 more)
We study the impact of light GeV-scale heavy neutral
leptons (HNLs) on Big Bang nucleosynthesis (BBN) in the
neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT). We show that, based on very general considerations, BBN constraints complement laboratory searches at
colliders, beam dumps, and neutrinoless double beta decay, by providing an upper bound on the cut-off scale of the effective field theory for HNL masses above $\sim$100 MeV. We identify target regions for future laboratory probes of the $\nu$SMEFT parameter space that is bounded from above and below.
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All authors Pieter Braat, Jordy de Vries, Jelle Groot, Julian Y. Günther, Juraj Klarić
Instrumentation and Methods for Astrophysics
ESO White Paper on Intensity Interferometry: Cosmology, Fundamental Physics, Quantum Optics
Robin Kaiser, William Guerin, Farrokh Vakili et al. (+21 more)
In this whitepaper, we outline how recent technological advances and ongoing developments open qualitatively new science opportunities in cosmology, fundamental physics, and
quantum astrophysics. First, intensity interferometry can contribute to one of the most foundational observables in cosmology: the expansion rate of the Universe. Its angular resolution allows it to resolve the angular extent of extragalactic objects such as
supernovae or
quasars; combined with a physical scale local to the source, this yields an angular diameter distance and hence a 'Hubble diagram'. Second, the nature of dark matter can be probed via the astrometric
lensing signatures of tiny dark matter
halos. Third, intensity interferometry gives direct access to second-order coherence properties of astrophysical emission, opening a window onto genuinely
quantum aspects of astrophysical light.
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All authors Robin Kaiser, William Guerin, Farrokh Vakili, Jean-Philippe Berger, Andrei Nomerotski, Sergei Kulkov, Peter Svihra, Eva Santos, Colin Carlile, Dainis Dravins, Stefan Funk, Prasenjit Saha, Roland Walter, Marcelo Borges Fernandes, Alex G. Kim, David Dunsky, Ken Van Tilburg, Masha Baryakhtar, Marios Galanis, Robert V. Wagoner, Neal Dalal, Junwu Huang, Charles Gammie, Norman W. Murray
Instrumentation and Methods for Astrophysics
Murriyang cryogenic phased array feed: spectral-line results and noise-reduction methods
L. Staveley-Smith, S. Barker, R. Berangi et al. (+25 more)
Spectral-line results from a new cryogenic phased array feed (cryoPAF) on the Murriyang
telescope at Parkes are presented. This array offers a significant improvement in field of view, aperture efficiency, bandwidth, chromaticity and survey speed compared with conventional horn-fed receivers. We demonstrate this with measurements of sky calibrators and observations of 21-cm neutral hydrogen (HI) in the LMC and the nearby
galaxy NGC 6744. Within 0.3 deg of the optical axis, the ratio of system temperature to dish aperture efficiency is 25 K and the ratio with beam efficiency is 21 K (at 1.4 GHz). For the previously measured $T_{sys} = 17$ K, respective efficiency values 0.7 and 0.8 are derived. Our HI observational results are in good agreement with previous results, although detailed comparison with multibeam observations of the LMC suggests that the earlier observations may have missed an extended component of low-column-density gas ($8\times 10^{18}$ cm$^{-2}$). We use the cryoPAF zoom-band and wideband data to make a preliminary investigation of whether the large number of simultaneous beams (72) permits the use of novel data reduction methods to reduce the effects of foreground/background continuum contamination and RFI. We also investigate if these methods can better protect against signal loss for the detection of faint, extended cosmological signals such as HI intensity maps. Using robust higher-order singular value decomposition (SVD) techniques, we find encouraging results for the detection of both compact and extended sources, including challenging conditions with high RFI occupancy and significant sky continuum structure. Examples are shown that demonstrate that 3D SVD techniques offer a significant improvement in noise reduction and signal capture compared with more traditional layered 2D techniques.
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All authors L. Staveley-Smith, S. Barker, R. Berangi, A.B. Bolin, S. Broadhurst, J.D. Bunton, N. Carter, S. Castillo, W. Chandler, A. Chippendale, J.R. Dawson, F. Di Dio, A.R. Dunning, S. Gordon, J.A. Green, A. Hafner, D.B. Hayman, D. Humphrey, A. Jameson, S. Johnston, J.F. Kaczmarek, J. Ma, G. Perry, M. Pilawa, J. Rhee, L. Toomey, J. van Aardt, N. Wang
Astrophysics of Galaxies
ALMA Band 9 CO(6–5) Reveals a Warm Ring Structure Associated with the Embedded Protostar in the Cold Dense Core MC 27/L1521F
Kazuki Tokuda, Mitsuki Omura, Naoto Harada et al. (+9 more)
Infall and
outflows, coupled with
magnetic fields, rapidly structure the gas around newborn protostars. Shocks from interacting components encode the temperature and density distribution, offering a direct probe of the earliest
evolution history. However, interferometric observations characterizing warm envelopes using high-excitation lines remain scarce. We present ALMA Band 9 observations of the Taurus dense core MC 27/L1521F, which hosts a Class 0 protostar, targeting the CO($J$=6-5) line at an angular resolution of $\sim$2\arcsec\ ($\approx$300 au). We detect an off-centered ring-like structure with a diameter of $\sim$1000 au that was not identifiable in previous low-$J$ CO data, where emission close to the systemic velocity is strongly affected by optical depth. The ring shows a typical peak brightness temperature of $\sim$3 K at our resolution. Excitation considerations indicate that the detected CO($J$=6-5) emission likely arises from relatively warm ($T \gtrsim 20$ K) and dense ($n({\rm H_2}) \gtrsim 10^{5}$ cm$^{-3}$) gas embedded within the surrounding cold, dense core. The morphology and kinematics suggest an energetic and localized shock-heating event, potentially linked to dynamical gas–
magnetic-field interactions in the earliest protostellar phase. Our results demonstrate that high-$J$ CO observations provide a powerful new window on warm and dense gas components, enabling a more direct view of the physical processes operating at the onset of
star formation.
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All authors Kazuki Tokuda, Mitsuki Omura, Naoto Harada, Ayumu Shoshi, Naofumi Fukaya, Toshikazu Onishi, Kengo Tachihara, Kazuya Saigo, Tomoaki Matsumoto, Yasuo Fukui, Akiko Kawamura, Masahiro N. Machida
High Energy Astrophysical Phenomena
Ballistic Surfing Acceleration as a Coherent Mechanism for Electron Acceleration in Galaxy Cluster Shocks
Ji-Hoon Ha and Krzysztof Stasiewicz
Radio relics in merging
galaxy clusters are widely interpreted as synchrotron emission from relativistic electrons accelerated at large-scale shocks. However, the efficiency of diffusive shock acceleration (DSA) is expected to be suppressed in the low-Mach-number, weakly turbulent environments of cluster mergers; furthermore, recent theoretical insights suggest that DSA may not constitute a viable physical mechanism for such environments. In this work, we investigate ballistic surfing acceleration (BSA) as an electrodynamically grounded alternative for electron energization that bypasses the need for prescribed
diffusion coefficients. We formulate BSA under typical cluster shock conditions, deriving the balance between coherent acceleration by the convective electric field and radiative losses from synchrotron and inverse-Compton cooling. This
equilibrium defines the maximum reachable electron energy and constrains the resulting steady-state spectrum. By forward-modeling the associated synchrotron emission and comparing it with integrated
radio observations of the `Sausage' (CIZA J2242.8+5301) and `Toothbrush' (1RXS J0603.3+4214) relics, we find that the observed spectral
curvature and high-frequency steepening are consistent with BSA-limited energies, provided that active acceleration involves only a minute participation fraction ($10^{-9}$-$10^{-8}$) of the radiating electrons. Despite this high selectivity, BSA effectively produces Lorentz factors of $\gamma \sim 10^4$-$10^5$. Our results suggest that
radio relics serve as
prime astrophysical laboratories for probing coherent acceleration, with the BSA framework providing a robust and physically consistent explanation for electron energization in cluster shocks.
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Earth and Planetary Astrophysics
KMT-2016-BLG-1337L: A Saturn-mass planet orbiting within a binary system of low-mass stars
Cheongho Han, Chung-Uk Lee, Ian A. Bond et al. (+55 more)
We report the discovery and characterization of a planetary companion in the microlensing event KMT-2016-BLG-1337, which was produced by a binary system of low-mass
stars. The light curve of the event exhibits a short-term anomaly superposed on the profile of a binary-lens single-source (2L1S) model. To investigate the nature of this anomaly, we performed detailed modeling under both the binary-lens binary-source (2L2S) and triple-lens single-source (3L1S) interpretations. The 3L1S model provides a substantially better fit to the data, strongly favoring the presence of a planetary companion in the lens system. Two viable $3L1S$ solutions describe the event nearly equally well. In one solution, the
planet has a mass of $M_3 \sim 0.3~M_{\mathrm{J}}$ and lies at a projected separation of $a_{\perp,3} \sim 4~{\rm au}$ from the heavier member of the host binary. In the alternative solution, the
planet has a mass of $M_3 \sim 7~M_{\mathrm{J}}$ and a projected separation of $a_{\perp,3} \sim 1.5~{\rm au}$. The host binary consists of early M-type
dwarfs with masses of $M_1 \sim 0.54~M_\odot$ and $M_2 \sim 0.40~M_\odot$, separated in projection by $a_{\perp,2} \sim 3.5~{\rm au}$. The system is located at a distance of $D_{\rm L} \sim 7~{\rm kpc}$ toward the
Galactic bulge. This event demonstrates the sensitivity of microlensing to
planets in dynamically complex
stellar environments, including systems beyond the reach of other detection techniques. It thereby contributes to a more comprehensive understanding of
planet formation in multiple-
star systems.
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All authors Cheongho Han, Chung-Uk Lee, Ian A. Bond, Andrzej Udalski, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Hongjing Yang, Doeon Kim, Dong-Jin Kim, Sang-Mok Cha, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Fumio Abe, David P. Bennett, Aparna Bhattacharya, Ryusei Hamada, Yuki Hirao, Asahi Idei, Stela Ishitani Silva, Shota Miyazaki, Yasushi Muraki, Tutumi Nagai, Kansuke Nunota, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Takahiro Sumi, Daisuke Suzuki, Takuto Tamaoki, Sean K. Terry, Paul J. Tristram, Aikaterini Vandorou, Hibiki Yama, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radosław Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz
Astrophysics of Galaxies
Graph Neural Network Prediction of Infrared Spectra of Interstellar Polycyclic Aromatic Hydrocarbons
Guoqing Tang, Jiang He, Zhao Wang et al. (+1 more)
Polycyclic aromatic hydrocarbons (PAHs) are recognized as the primary contributors to the aromatic infrared bands (AIBs) widely observed in space. However, analyzing these AIBs remains challenging because of the immense structural diversity within the PAH family, which makes the computation of reliable reference spectra difficult. To address this, we developed an efficient graph neural network (GNN) framework that can predict PAH absorption spectra up to 10,000 times faster than traditional
quantum chemical methods. We evaluated four representative GNN architectures, including graph convolutional network (GCN), graph
attention network (GAT), message passing neural network (MPNN), and attentive fingerprint (AFP). The AFP model is found to deliver the best overall performance and is further trained using five different spectral distance metrics as loss functions, among which the Jensen-Shannon divergence yields the most accurate and stable results. The model performs best for PAHs containing 20-40 carbon atoms, while accuracy decreases for larger molecules, reflecting the limited availability of training data. Overall, this framework offers a fast method to generate approximate reference spectra for small- to medium-sized PAHs, supporting future AIB analysis.
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All authors Guoqing Tang, Jiang He, Zhao Wang, Dong Qiu
Earth and Planetary Astrophysics
Bundle adjustment of Hayabusa2's ONC images and controlled color mosaic map of Ryugu
Naoyuki Hirata, Eri Tatsumi, Mayumi Ichikawa et al. (+2 more)
JAXA's Hayabusa2 mission successfully returned samples from the asteroid Ryugu in December 2020. It executed two touchdowns to collect the surface and subsurface materials, one close to the crater created by an artificial impactor. The onboard camera system, Optical
Navigation Camera (ONC), with two wide-angle cameras and one narrow-angle camera with seven color filters, was crucial for mapping geomorphology and composition such as hydrated minerals during
navigation and scientific observation. More than 8,300 images revealed Ryugu's spinning-top shape and boulder-covered surface. However, most high-resolution images captured during descent/touchdown operations lacked precise location data and camera position/orientation information. Image geometry was refined using photogrammetric bundle adjustment. This method enabled the refinement of all high-resolution images captured during descent/touchdown operations. Furthermore, map-projected GeoTIFF images in GIS format containing geographic metadata were created for all ONC images, and these were integrated to construct global and regional mosaic maps. To facilitate scientific research on Ryugu, these refined image geometry information, maps, and mosaics are publicly available via https://doi.org/10.7910/DVN/WW3IH0
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All authors Naoyuki Hirata, Eri Tatsumi, Mayumi Ichikawa, Kazuhiro Honda, Sayuri Tanaka
Astrophysics of Galaxies
The Structure and Evolution of LRDs: Insights from JWST NIRSpec Medium and High Resolution Spectroscopy at $z\sim4$
Yuxuan Pang, Xin Wang, Cheng Cheng et al. (+5 more)
We present an analysis of medium/high-resolution JWST/NIRSpec spectra for 11 LRDs at $z \sim 4$. By decomposing the broad and narrow components of the Balmer emission lines, we investigate the connection between line emission and UV/optical continua for the LRD population. We find that the broad H$\alpha$ luminosity strongly correlates with the optical continuum (but not with the UV), indicating a common AGN origin for both. In contrast, the [O III] line strength is correlated with the UV continuum rather than the optical. Using the width and luminosity of the broad H$\alpha$ line, we estimate central black hole masses of $10^6-10^8 M_{\odot}$ accreting at high Eddington ratios, consistent with an early ($\lambda_{\rm Edd} \sim 0.6$), rapid-growth phase of AGN
evolution. Assuming a constant mass
accretion rate in the framework of slim-disk models, we infer growth timescales of $\sim 10^5-10^7\rm yr$, and suggest LRDs may evolve into narrow-line Seyfert 1
galaxies. Upper limits from our spectra indicate that LRDs exhibit intrinsically weak optical Fe II emission compared to typical AGN. To simultaneously account for the inferred broad-line region size and observed luminosity, we propose a "Clumpy Envelope" model in which the optical emission arises from an extended, clumpy gas with a characteristic radius of tens of light-days. The diversity in observed optical continuum shapes can be explained by radial temperature gradients and self-absorption effects within this structure. Our results demonstrate the power of JWST high-resolution spectroscopy in probing the central engines and physical nature of the LRD population.
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All authors Yuxuan Pang, Xin Wang, Cheng Cheng, Shengzhe Wang, Hang Zhou, Qianqiao Zhou, Xue-Bing Wu, Karl Glazebrook
Instrumentation and Methods for Astrophysics
Guangqi: A two-dimensional radiation hydrodynamic code with realistic equation of states
Zhuo Chen and Xue-Ning Bai
We present Guangqi, a new two-dimensional, finite-volume radiation hydrodynamics code designed for high-performance astrophysical simulations. The code simultaneously resolves the hydrodynamic equations for complex equations of state (EoS) and implicit radiation transport under the flux-limited
diffusion approximation. Written in Fortran and parallelized via the Message Passing Interface. Guangqi supports analytic hydrogen and helium EoS under the assumption of local thermal and chemical
equilibrium. The framework is compatible with both Cartesian and spherical-polar geometries – utilizing non-uniform grid spacing – and incorporates static (SMR) and adaptive mesh refinement to optimize computational efficiency. To address the inherent challenges of angular momentum conservation in spherical-polar coordinates, we implement a robust and consistent "passive scalar angular momentum
algorithm" (PSAMA). Domain decomposition is managed through both Z-order and
Hilbert space-filling curves to ensure scalability. The code has been rigorously verified against a suite of standard
benchmarks and newly designed test cases specifically intended to diagnose the non-linear coupling between gas dynamics, intricate EoS, radiation transport, and angular momentum conservation.
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Astrophysics of Galaxies
Full-spectrum infrared fingerprinting: A transformative AI paradigm for interstellar polycyclic aromatic hydrocarbons
Zhao Wang
In the era of high-sensitivity infrared (IR) astronomy, traditional manual diagnostics are no longer sufficient to harvest the complex physical insights hidden within interstellar spectra. We introduce a machine learning paradigm that bypasses the limitations of empirical band ratios by treating the complete IR spectrum of polycyclic aromatic hydrocarbons (PAHs) as a high-dimensional fingerprint. Using a random forest classifier trained on over 23000 spectra, we achieve a robust F1-score of 0.963 across 12 size and charge categories, maintaining high performance on unseen molecular mixtures. Interrogating the model's decision-making process reveals that PAH size diagnostics are charge-dependent. Neutral PAHs are traced by C-H modes, while ionized species rely on 6-8 micron C-C morphology; however, the 12.5micron feature remains a versatile tracer across multiple charge states. This AI-driven paradigm redefines our understanding of IR signatures, providing a transformative lens to probe the chemical complexity of the interstellar medium.
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Earth and Planetary Astrophysics
A Protoplanet Candidate in the PDS 66 Disk Indicated by Silicon Sulfide Isotopologues
Tomohiro C. Yoshida, Felipe Alarcón, Jaehan Bae et al. (+11 more)
Despite observational progress in
planet formation, the stage in which planetesimals grow into
planets remains poorly understood. During this phase, protoplanets may develop gaseous envelopes that are warmer than the surrounding disk gas, potentially providing observable signatures through molecules otherwise depleted in cold regions. In this Letter, we report the detection of the silicon sulfide isotopologues ${\rm ^{28}SiS}\ J{=}16{-}15$ and ${\rm ^{30}SiS}\ J{=}18{-}17$ in the protoplanetary disk around PDS 66 (MP Mus) at a significance of ${\sim}5{-}6\sigma$, using the Atacama Large Millimeter/submillimeter Array. These constitute the second and first detections of $\rm ^{28}SiS$ and $\rm ^{30}SiS$ in a protoplanetary disk, respectively. The emission appears as a compact source at $r \simeq 60$ au in the southwestern region of the disk, unresolved with a ${\sim}0.\!\!^{\prime\prime}5$ beam, and shows a velocity consistent with Keplerian rotation, suggesting a protoplanetary origin. By modeling the line fluxes, we constrain the emitting radius to ${\sim}0.5{-}4$ au and estimate an SiS mass of $10^{22}{-}10^{23}$ g, corresponding to at least ${\sim}10\%$ of the silicon contained in local
dust grains. Because complete sublimation of a substantial fraction of
dust grains by local processes is difficult to achieve, this result instead implies an accumulation of silicon from a larger region. We propose that a circumplanetary envelope surrounding a low-mass protoplanet, where pebble
accretion and subsequent sublimation of grains may enhance gaseus silicon abundance with respect to observable
dust grains around it, can account for the observed characteristics.
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All authors Tomohiro C. Yoshida, Felipe Alarcón, Jaehan Bae, Myriam Benisty, Kiyoaki Doi, Stefano Facchini, Charles J. Law, Hideko Nomura, Laura Perez, Giovanni Rosotti, Yuhito Shibaike, Richard Teague, Takashi Tsukagoshi, Yoshihide Yamato
Solar and Stellar Astrophysics
Unusual Circumstances of the 2024 June 8 GLE
Nat Gopalswamy, Pertti Makela, Hong Xie et al. (+3 more)
Ground Level Enhancement (GLE) in large
solar energetic particle (SEP) events is indicative of
protons accelerated to GeV energies. Almost all GLE events are associated with sustained gamma-ray emission (SGRE) from the Sun because the latter require >300 MeV
protons that are readily present during GLEs. Here we report on the 2024 June 8 GLE event, which has the distinction of not being associated with an SGRE event. All the associated phenomena typical of SGRE events were present: a fast and wide CME, a major
solar flare, and an intense type II
radio bursts that extend from the metric to kilometric wavelength domains. There was a data gap of ~51 min, but the SGRE is expected to last for hours. We suggest the east-west asymmetry in the flow of energetic particles from the shock is likely to be the reason for the lack of SGRE emission.
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All authors Nat Gopalswamy, Pertti Makela, Hong Xie, Sachiko Akiyama, Seiji Yashiro, Atul Mohan
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Bikai Gao
The “hyperon puzzle” remains a fundamental challenge in
nuclear astrophysics. We investigate hyperon emergence in
neutron star matter using the $SU(3)$ parity doublet model with
chiral representation $(3,\bar{3}) + (\bar{3},3)$. This framework naturally incorporates
chiral symmetry restoration and provides a systematic description of
baryon masses in dense matter through the interplay between the
chiral condensate and the
chiral invariant mass $m_0$. We find that the hyperon onset density exhibits strong sensitivity to $m_0$: for $m_0 = 500$ MeV, hyperons first appear at $1.9n_0$ while for $m_0 \gtrsim 750$ MeV, hyperons emerge only above $5n_0$. This delayed onset arises from the weakened density dependence of
baryon masses at larger $m_0$ values. When the hyperon onset density exceeds the expected
quark-
hadron transition range ($2$–$5n_0$), matter undergoes deconfinement before hyperons populate, avoiding the EoS softening while maintaining consistency with massive
neutron star observations. Our results demonstrate that
chiral dynamics provides a natural resolution to the hyperon puzzle without requiring ad hoc repulsive hyperon interactions.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Dark matter effects on the properties of hybrid neutron stars
Jin-Biao Wei, G. Wu, H. Chen et al. (+2 more)
We study the effects of dark matter on the properties of hybrid
neutron stars, in particular the influence on the mass-radius relation, the value of the maximum mass, and the
hadron-
quark phase transition. To single out the
equilibrium configurations of dark-matter-admixed hybrid
neutron stars (DHSs), we also study their radial oscillations. Both the
stellar structure equations and the radial oscillation equations are solved for the two-fluid system, where the ordinary matter component and dark matter component couple only through
gravity. For the ordinary matter components, we adopt the Brueckner-Hartree-Fock method for
nuclear matter, and the Dyson-Schwinger or the field-correlator model for
quark matter. For the dark matter component, we use a non-self-annihilating self-interacting fermionic model. We find that the presence of dark matter in DHSs leads to a decrease of the critical mass of the
hadron-
quark phase transition, a related possible onset of
quark matter in dark-matter accreting
stars, and a significant reduction of radial oscillation frequencies.
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All authors Jin-Biao Wei, G. Wu, H. Chen, G. F. Burgio, H.-J. Schulze