Instrumentation and Methods for Astrophysics
Earth Science Foundation Models: From Perception to Reasoning and Discovery
Xiangyu Zhao, Bo Liu, Yuehan Zhang et al. (+9 more)
Large foundation models (FMs) are transforming Earth science by integrating heterogeneous
multimodal data, such as multi-platform imagery, gridded reanalysis data, diverse geophysical and geochemical observations, and domain-specific text, to support tasks ranging from basic perception to advanced scientific discovery. This paper provides a unified review of Earth science foundation models (Earth FMs) through two complementary dimensions: depth, which traces the
evolution of model capabilities from perception to
multimodal reasoning and agentic scientific workflows, and breadth, which summarizes their expanding applications across the atmosphere, hydrosphere, lithosphere, biosphere, anthroposphere, and cryosphere, as well as coupled Earth system processes. Using this framework, we review representative
multimodal Earth foundation models and compile more than 200
datasets and
benchmarks spanning diverse Earth science tasks and modalities. We further discuss key challenges in
multimodal data heterogeneity, scientific reliability and continual updating, scalability and sustainability, and the transition from foundation models to agentic and
embodied Earth intelligence, and outline future directions toward more integrated, trustworthy, and actionable AI Earth scientists. Overall, this paper offers a structured roadmap for understanding the development of Earth foundation models from both capability depth and application breadth.
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All authors Xiangyu Zhao, Bo Liu, Yuehan Zhang, Zelin Song, Wanghan Xu, Feng Liu, Fengxiang Wang, Ben Fei, Fenghua Ling, Wangxu Wei, Wenlong Zhang, Xiao-Ming Wu
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Ronaldo V. Lobato, Geanderson A. Carvalho, Carlos E. C. Montaña et al. (+1 more)
We investigate a conservative formulation of $f(R,T)$
gravity motivated by a key limitation of several existing approaches: the gravitational function is often reconstructed from a chosen equation of state, making the
gravity sector EoS-dependent and compromising universality. To avoid this problem, we reformulate the theory in terms of an effective energy-momentum tensor, so that the conservation law follows from the field equations and Bianchi identities while the gravitational action remains independent of the microphysical EoS. We derive the modified
stellar structure equations, establish theoretical consistency conditions including coupling bounds and crust-singularity avoidance, and present the
tidal perturbation sector in terms of effective thermodynamic variables and an effective sound speed. We then compute
neutron star observables using realistic tabulated EoSs, including mass-radius relations and
tidal deformabilities, and compare the model with current astrophysical constraints from massive
pulsars, NICER radius measurements, and GW170817.
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All authors Ronaldo V. Lobato, Geanderson A. Carvalho, Carlos E. C. Montaña, Jose F. Rodriguez-Ruiz
Astrophysics of Galaxies
JWST observations and a model for the extremely luminous obscured quasar W2246-0526 at z=4.6
Charalambia Varnava, Andreas Efstathiou, Tanio Díaz-Santos et al. (+1 more)
We present new JWST/MIRI-MRS data of the z=4.601 extremely luminous obscured
quasar WISEA J224607.56-052634.9 (W2246-0526). Our fits of its spectral energy distribution (SED) with the SED fitting code SMART (Spectral energy distributions Markov chain Analysis with Radiative Transfer models) predict an active
galactic nucleus (AGN) fraction in the range 72-81 per cent, an intrinsic AGN luminosity of 4.2-7.2 x 10^14 Lo, a polar
dust luminosity of 1.6-1.7 x 10^14 Lo, a black hole mass of 1.3-2.3 x 10^10 Mo (assuming the
quasar is accreting at the Eddington limit), a
star formation rate (SFR) of 360-2900 Mo/yr and a
stellar mass of 4.8-5 x 10^11 Mo. The
stellar and black hole masses of W2246-0526 are typical of a
giant elliptical
galaxy at z=0. We find statistically significant evidence for the presence of a hot
dust component, which we interpret as polar
dust in the context of a
torus geometry, based on recent results obtained for nearby AGN. We explore two smooth and two two-phase models for the AGN
torus, to put constraints on the AGN fraction of the
galaxy, the black hole mass and its SFR. We show that the presence of polar
dust affects the estimate of the AGN luminosity and we recommend to take into account this component in SED fits of other high-
redshift obscured AGN/
quasars. Despite the large difference in luminosity, we discuss possible links between the presence of this hot
dust component in W2246-0526 and in some local AGN, suggesting that they may have a different origin.
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All authors Charalambia Varnava, Andreas Efstathiou, Tanio Díaz-Santos, Duncan Farrah
Earth and Planetary Astrophysics
Exploring Enceladus's Interior Structure Using Electromagnetic Induction
Alexander Grayver and Joachim Saur
Electromagnetic (EM) sounding can constrain the electrical structure of Enceladus and, in turn, the salinity of its ocean and the porosity, fluid content, and thermal state of its hydrothermally active core. Here, we assess the feasibility of EM sounding at Enceladus using both global (orbiter) and local (lander) EM induction transfer functions. We provide a physical framework for modeling EM induction for 1-D and 3-D subsurface conductivity models and discuss how transfer functions can be estimated from global or local measurements of the
magnetic and electric fields. We simulate 3-D induction effects arising from variations in ice-shell thickness. The magnitude of these effects in the
magnetic field correlates with the ice-shell thickness at the surface and is strongly dependent on the ocean's conductivity. These
magnetic variations, if observed, would favor a moderately to highly conductive ocean, providing lower bounds on salinity and volatile content. The absence of these effects indicates a thicker, more homogeneous ice shell and/or a lower-conductivity ocean. Given plausible magnitudes, a polar-orbiting mission with low-altitude measurements will be required to detect these effects. In summary, an orbiter will constrain global ocean conductivity using long-period induction and possibly map the ice thickness variations. The detailed EM sounding of both the hydrosphere and the core can be achieved by a lander-based broadband EM sounding at periods $\approx 10^1-10^5$ s to probe ocean salinity and thickness, as well as core properties including porosity, fluid content, and temperature.
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Astrophysics of Galaxies
Plato's view on supermassive black hole binaries: Exploring the faint limit of ESA's Plato space mission
Nicholas Jannsen, Pablo Huijse, Kevin Park et al. (+3 more)
The search for supermassive black hole binaries (SMBHBs) has, in recent years, seen the dawn of exploration with several hundred candidates claimed from photometric and spectroscopic surveys monitoring AGNs. While only a handful persist to date, the advent of upcoming high-precision wide-field photometric missions motivates continuing the pursuit of confirming SMBHBs in the optical. We explore the possibility of using the ESA Plato space mission to detect photometric signatures of SMBHBs. Motivated by the Kepler observation of Spikey, the best known self-
lensing flare (SLF) candidate to date, this work aims to
benchmark the scientific outcome if Plato were to observe Spikey-like objects via its Guest Observer programme. Starting from the
Gaia database, we assemble a catalogue of 12,226 bright ($G < 19$) high-probability
Quasars for the two pointing fields of Plato's nominal mission. This Plato
Quasar catalogue will be pivotal for future follow-up observations of larger photometric searches such as the Vera Rubin LSST survey. We use the Plato camera simulator, PlatoSim, to realistically explore the noise budget in Plato's faint limit, while generating mock light curves to
benchmark Plato's ability to recover signatures of SMBHBs. We show that, although not at all designed for the purpose, Plato is capable of detecting Spikey-like SMBHB candidates through their relativistic photometric signatures using
Bayesian inference and evidence. Plato will in particular be able to confirm or rule out Spikey and Spikey-like objects with a limiting magnitude of $G\leq18$. With a minimum 2-yr baseline per pointing field, we show that Plato not only could play an essential role in future SMBHB research, but may be an integrated part of the observational fleet of continuous high-precision facilities monitoring SMBHB candidates in the near future.
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All authors Nicholas Jannsen, Pablo Huijse, Kevin Park, Zoltan Haiman, Daniel J. D'Orazio, Conny Aerts
Cosmology and Nongalactic Astrophysics
Separate Universe Super-Resolution Emulator
Dennis Fremstad, Julian Adamek and David F. Mota
We present a machine-learning model for generating super-resolution $N$-body simulations with non-vanishing spatial
curvature, conditioned on a given low-resolution field, $\Omega_k$, $\Omega_\mathrm{m}$, $\sigma_8$, $h$, and
redshift. By upscaling the resolution of $N$-body simulations, such models can drastically reduce the computational cost of producing high-resolution simulations suitable for modelling current and future surveys of large-scale structure. Our model is trained as a generative
adversarial network, allowing injected noise to be interpreted as
stochastic structure and enabling the generation of an ensemble of plausible high-resolution realisations. We evaluate the model performance by comparing key cosmological summary statistics in the generated simulations to their high-resolution counterparts. We find that the model accurately reproduces large-scale statistics, robustly recovering most of the power that was missing from the low-resolution input, but exhibits a residual suppression of power on small scales of up to $\sim 10\%$ at $k \sim 1\,h\,\mathrm{Mpc}^{-1}$. The abundance of
halos around $10^{14}\,M_\odot$ is affected at a similar level, and we find that the profiles of these
halos have a lower central density. Although the overall performance is decent, we anticipate that the fidelity of the generative model can be further increased with more and better training data, as well as through improvements in the model architecture and training process. To show a production-scale use case, we apply our model to upscale the resolution of a light cone from a large-volume $N$-body simulation with spatial
curvature, producing a first-of-its-kind catalogue that simultaneously captures
geometric effects at large scales and accurate nonlinear structure at small scales.
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Astrophysics of Galaxies
Complexity and Multifractal Variability in Multi-Band Emission of Seyfert AGN
R. A. A. Souza, E. Hatziminaoglou, A. de Pádua Santos et al. (+1 more)
Active
galactic nuclei (AGNs) exhibit complex variability across multiple wavelengths, reflecting diverse physical processes near their central engines. This work investigates the temporal variability of four AGNs Mrk~509, NGC~5548, NGC~4151, and NGC~4593 using multifractal detrended moving average (MFDMA) analysis and Fisher-Shannon information plane applied to their X-ray, ultraviolet, and optical light curves. These methods quantify the scaling behavior and complexity of the variability, revealing persistent correlations and distinct variability patterns across energy bands. The Fisher-Shannon analysis further characterizes the degree of stochasticity and structural complexity in the emission processes. Our findings support the interpretation that multifractal and information-theoretic measures provide effective diagnostics of the physical mechanisms driving AGN variability. This study demonstrates the utility of advanced time series techniques as effective diagnostics of AGN variability mechanisms.
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All authors R. A. A. Souza, E. Hatziminaoglou, A. de Pádua Santos, T. Stosic
Astrophysics of Galaxies
Interstellar X-ray Absorption and Scattering
Linli Yan, Aigen Li and Fangjun Lu
Accurate estimates of the absorption of X-rays by interstellar gas and
dust are of crucial importance for the analysis and interpretation of almost all astronomical soft X-ray observations. However, the present X-ray absorption data extensively used by the community were derived from a reduced interstellar abundance (~70% of
solar) and ignoring
dust scattering. Therefore, these X-ray absorption data, although highly popular, could have been substantially underestimated. Here we update the interstellar X-ray absorption and scattering by making use of updated atomic cross sections, updated interstellar abundances, and realistic X-ray
dust physics, and appropriately distributing metal elements in gas and
dust. The resulting X-ray absorption and scattering data are publicly available on GitHub.
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Astrophysics of Galaxies
The MaNGA Low-mass disks HUnt for CO (MaLHUCO) Survey
M. Grossi, E. Corbelli, D. R. Gonçalves et al. (+1 more)
We present James Clerk Maxwell
Telescope (JCMT) observations of the $^{12}$CO(J = 2-1) emission of 42 low-mass,
star-forming disk
galaxies of morphological type Scd or later from the Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA) survey. The sample, which probes the M33-like
stellar-mass regime, is complemented with
metallicities,
star formation rates, and \hi\ masses used to investigate the
star formation process and to test scaling relations involving molecular gas mass in low-mass systems. We detect CO emission in 55% of the sample and derive H$_2$ masses using both a constant
Galactic and a
metallicity-dependent CO-to-H$_2$ conversion factor. The 12 $\mu$m luminosity, which includes polycyclic aromatic hydrocarbon features, exhibits a tight linear correlation with the CO line emission, making it a robust tracer of global molecular gas content. The molecular gas mass -
star formation rate relation, i.e. the Kennicutt-Schmidt law, is the most fundamental one and it is found to remain linear down to low
stellar masses. We also find that the mean molecular gas depletion time is slightly shorter in low-mass late-type
galaxies than in more massive systems, consistent with their higher specific
star formation rates. Finally, while the specific molecular gas mass ($M_{\rm H_2}/M_*$) shows no significant dependence on
stellar mass and a large intrinsic scatter, the HI-to-
stellar mass ratio ($M_{\rm HI}/M_*$) decreases with increasing
stellar mass and molecular fraction ($M_{\rm H_2}/M_{\rm gas}$), highlighting the progressive transition from atomic- to molecular-dominated interstellar medium along the
galaxy population.
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All authors M. Grossi, E. Corbelli, D. R. Gonçalves, E. D. Paspaliaris
Cosmology and Nongalactic Astrophysics
Reionisation time field reconstruction from 21-cm Maps: Investigating predictor coherence in WDM cosmology
Julien Hiegel, Dominique Aubert, Émilie Thélie et al. (+2 more)
The reionisation time field treion(r) captures the entire history of
cosmic reionisation by mapping the moment where each region of the Universe became ionised. Previous work has shown that treion(r) can be inferred from 21-cm observations, using convolutional neural networks (CNNs). However, these CNN predictors are trained on specific reionisation models, raising critical concerns about their reliability when applied to observational data potentially differing from their training assumptions. This paper aims to propose and test a method to evaluate the coherence of our CNN predictors with respect to their input model, thereby enabling the validation or exclusion of underlying reionisation models based on their reconstruction behaviour. By setting the CDM model as reference input, we evaluate the coherence of treion(r) reconstructions by comparing them across different
redshifts for several prediction models as the statistics of treion (r) reconstructions should be the same for every
redshift of the input maps. Our study particularly investigates CNNs trained on cold and warm dark matter (WDM) models, with WDM particle masses of 2, 3, 5, and 7 keV. We find that the predictors trained on 5 and 7 keV WDM models exhibit high-level self-consistency similar to the CDM predictor, while the 2 keV predictor, and to a lesser extent the 3 keV predictor, display significant deviations across several metrics. These findings seem to demonstrate that CNN predictors retain sensitivity to differences in the underlying reionisation model and can be used to assess model compatibility with observations. Our results highlight the necessity of validating machine-learning predictors against their input models before applying them to real data. The method proposed here offers a pathway to more trustworthy applications of CNNs in the study of reionisation.
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All authors Julien Hiegel, Dominique Aubert, Émilie Thélie, Rodrigo Ibata, Nicolas Mai
Earth and Planetary Astrophysics
BOCOSUR: An all sky network for fireball detection in Uruguay
M. Caldas, A. Guaimare, V. Abraham et al. (+4 more)
Over the past couple of decades, several networks for the automatic detection of fireballs have been deployed. Their primary scientific goal is to facilitate the rapid recovery of meteorites, determine their pre-atmospheric orbits, and look for possible dynamic links with parent bodies. The Bocosur network is a contribution to the global deployment of automated fireball networks and to the increase of the number of recoverable meteorite falls. It is located in Uruguay, South America (Lat: -30$^{\circ}$ to -35$^{\circ}$). Its main scientific goal is the detection of fireballs of asteroidal origin, massive enough to produce meteorites, and also to inspire secondary-level students and teachers through their involvement in this citizen-science oriented project. The deployment of this network started in 2019, and was completed in March, 2023, when we installed 20 stations separated $\sim 120$ km, covering an area of $\sim 180,000$ km$^2$. During this period of time, one major technological upgrade was made when we migrated from a well-known camera to a higher-resolution, more sensitive system. We were able to build a completely autonomous system at an affordable cost that can be replicated in all the stations. A comparison between the astrometric and photometric performance of these two detection systems is reported. Also, a photometric methodology for estimating the brightness of very bright fireballs is presented and validated against the known magnitudes of Jupiter and the full Moon. We obtain mean residuals of the astrometric reduction of $\sim$5', and the discrepancy between the obtained brightness of Jupiter and the Moon average to 0.18 and 1.2 magnitudes, respectively. Results on the processing of a very bright (M$_{peak}\sim$-9.0 mag) fireball detected in four stations are also presented.
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All authors M. Caldas, A. Guaimare, V. Abraham, L. Barrios, M. Hernández, L. Velasco, G. Tancredi
Cosmology and Nongalactic Astrophysics
The Status of Gravitational Vector Perturbations with Recent CMB Data
Ali Rida Khalife and Cyril Pitrou
We present new constraints on gravitational vector perturbations ($\mathcal{V}$-modes) using
Cosmic Microwave Background (CMB) data, including temperature and $E$-mode polarization from SPT-3G D1, ACT-DR6, and $Planck$, as well as $B$-mode data from BICEP/Keck and SPTpol, which provide the strongest constraints on $\mathcal{V}$-modes. We consider three initial conditions (ICs) that source $\mathcal{V}$-modes:
neutrino isocurvature (ISO),
neutrino octupole (OCT), and a sourced mode (SMD) generated by an anisotropic stress before matter-radiation equality. We also consider including tensor modes along with $\mathcal{V}$-modes for each of these ICs. Combining all
datasets, we obtain 95% confidence level upper limits of $r_\mathrm{v} < 1.3\times10^{-4}$ (ISO), $r_\mathrm{v} < 6.8$ (OCT), and $r_\mathrm{v} < 4.2$ (SMD), with slightly tighter bounds when tensors are included, at a pivot scale $k_p\ =\ 0.05$ Mpc$^{-1}$. Interestingly, for SMD without tensors, using SPTpol $B$-modes alone yields $r_\mathrm{v} = 4.7 \pm 2.1$, consistent with zero at $2.2\sigma$. Similar result is found for SMD when including tensor perturbations. No statistically significant deviation from $\Lambda$CDM is found. However, $\mathcal{V}$-modes are not fully excluded by current $B$-mode data and should be considered when interpreting
primordial signals.
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Cosmology and Nongalactic Astrophysics
Beyond power spectrum to unveil systematics on HI intensity maps
Pauline Gorbatchev, Jean-Luc Starck, Stefano Camera et al. (+1 more)
HI intensity mapping is a promising technique to probe large-scale structure, traditionally analyzed via two-point statistics such as the angular power spectrum. This technique has proven very powerful but may miss key non-Gaussian information present in the signal. We extend the starlet l1-norm, a multi-scale higher-order statistic previously applied to weak
lensing maps, to the brightness temperature fluctuations of the HI density field. The HI signal is highly non-Gaussian at late times (z < 1) due to nonlinear structure growth, motivating the use of advanced summary statistics. We simulated full-sky HI lognormal brightness temperature maps using CAMB and GLASS, generating 10,000 realizations with associated cosmological parameters. We extracted both the starlet l1-norm and angular power spectrum from these maps. Using the JaxILI framework, we performed neural density estimation for implicit likelihood inference. The analysis considered simulated maps incorporating realistic noise and
telescope beam, capturing the impact of observational effects on parameter inference. In this work, we focus on the
redshift range 0.4 < z < 0.45, chosen to match the interval already targeted by existing MeerKLASS observations. The starlet l1-norm significantly outperforms the angular power spectrum in constraining cosmological parameters, achieving almost a 3x improvement in the figure of merit relative to the angular power spectrum by capturing non-Gaussian features missed by two-point statistics. Moreover, our results suggest that the starlet l1-norm is robust to several of the systematic effects included in our simulations. Our findings highlight the potential of multi-scale higher-order statistics such as the starlet l1-norm to enhance cosmological inference from future HI intensity mapping surveys.
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All authors Pauline Gorbatchev, Jean-Luc Starck, Stefano Camera, Marta Spinelli
Earth and Planetary Astrophysics
Observations of the 2023 February 27 fireball in northern Sweden using the auroral imaging system ALIS_4D
Gabriel Borderes-Motta, Daniel Kastinen, Tima Sergienko et al. (+7 more)
On 2023 February 27 at 18:15:55.77 UT, a bright fireball streaked across the sky above northern Sweden. The event offered a valuable opportunity to study the phenomenon using an optical system primarily designed for auroral studies, the Auroral Large Imaging System (ALIS_4D), that captured the event. In this study we show the capability of ALIS_4D to perform observations in support of meteor event analysis. We estimated the trajectory from the recorded data and computed the orbit. In addition, we investigated the origin of the meteoroid searching for its parent body. Fitting the analytical ablation model known as $\alpha$-$\beta$ to the trajectory as well as incorporating local wind-field data in Monte-Carlo dark-flight simulations, strewn-fields were computed and physical properties of the meteoroid were estimated. Trajectory analyses delineate a strewn field along the border between Kiruna and Gällivare in northern Sweden. Our findings indicate that the meteoroid's parent body was likely an Apollo family object. We performed an orbital similarity analysis to identify candidate parent bodies of the fireball. Our simulations suggest that close approaches with Earth could have disrupted the meteoroid's orbit, placing it on a collision course.
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All authors Gabriel Borderes-Motta, Daniel Kastinen, Tima Sergienko, Urban Brändström, Johan Kero, Jaakko Visuri, Maria Gritsevich, Jarmo Moilanen, Daniela Cardozo Mourão, Barbara Celi Braga Camargo
Astrophysics of Galaxies
When Magnetic Fields Sculpt the Sky: The Riegel-Crutcher cloud in optical polarization
Gabriel A. P. Franco, Mayara Gomides, Zhi-Yun Li et al. (+2 more)
Filamentary structures are ubiquitous in the interstellar medium, yet the extent to which
magnetic fields influence the morphology of cold atomic gas remains an open question. The nearby Riegel-Crutcher cloud, composed of long and narrow H I filaments observed in self-absorption, provides a critical test case. We present the most extensive optical polarimetric survey of this region to date, comprising more than 90,000 high signal-to-noise
stellar polarization measurements combined with
Gaia DR3 data. Using
stellar polarization, extinction estimates, and archival Na I absorption data, we locate the cloud at a distance of $150 \pm 15$ pc, consistent with that of the Pipe Nebula. The plane-of-sky
magnetic field traced by optical starlight polarization closely matches that inferred independently from Planck 353 GHz
dust-emission polarization, revealing a coherent large-scale
magnetic field across the region. A Rolling Hough Transform analysis shows that the H I filaments are tightly aligned with this field orientation. Together, these results provide strong observational evidence that the structure of the cold neutral medium in the Riegel-Crutcher cloud is closely linked to a highly ordered
magnetic field. This level of coherence supports a scenario in which
magnetic fields play a dynamically important role in shaping the cloud structure, and suggests that the Riegel-Crutcher cloud is part of a larger magnetized complex influencing gas flows in the
solar neighborhood.
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All authors Gabriel A. P. Franco, Mayara Gomides, Zhi-Yun Li, Fabio P. Santos, Farideh S. Tabatabaei
Astrophysics of Galaxies
The evolution of C4H and c-C3H2 in molecular cores
Yijia Liu, Junzhi Wang, Ningyu Tang et al. (+8 more)
Linear C4H and cyclic c-C3H2, as small unsaturated hydrocarbons, are the key precursors to complex organic molecules and are critical components of the interstellar medium. We present on-the-fly mapping observations of C4H 9-8 lines, c-C3H2 2-1, H13CO+ 1-0, and H42 toward a sample of 22 massive
star-forming regions using the IRAM 30m
telescope. Our aim is to further explore the
evolution of these carbon-chain molecules by combining observational results obtained in cold cores. We employed H13CO+ 1-0 and H42 as tracers to probe the positions of molecular cloud cores and ionised hydrogen regions (HII regions), respectively. One chemical model in particular, which includes gas,
dust grain surface, and icy mantle phases for C4H and c-C3H2 molecules, was used to make comparisons with observed abundances. From mapping observations targeting 31 regions across 22 sources, C4H 9-8 (J = 19/2-17/2) and C4H 9-8 (J = 17/2-15/2) were detected in only 17 regions, while H13CO+ 1-0 and c-C3H2 2-1 were successfully detected in all 31 regions. We find that the emission of C4H 9-8 and c-C3H2 2-1 is concentrated at the edges of H42 emission regions. The C4H/H13CO+ and c-C3H2/H13CO+ relative abundance ratios range from 0.17 to 1.77 and 1.42 to 6.69, respectively, with a median C4H/c-C3H2 ratio of 0.13. By combining the observational results of cold cores, we find that C4H/H13CO+ and c-C3H2/H13CO+ ratios show a strong decreasing trend as molecular cores evolve. The decreasing trends in C4H/H13CO+ and c-C3H2/H13CO+ ratios imply that small unsaturated hydrocarbons can be consumed and converted into other organic molecules during the
evolution of molecular cores. The spatial concentration of C4H and c-C3H2 emission at the edges of H42 regions further supports their role as precursors in the chemical pathways that lead to complex organic molecules in the interstellar medium.
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All authors Yijia Liu, Junzhi Wang, Ningyu Tang, Yajiang Lu, Donghui Quan, Juan Li, Kai Yang, Shu Liu, Yuqiang Li, Siqi Zheng, Chao Ou
High Energy Astrophysical Phenomena
Chasing the neutrino blazar candidates II: SED modeling with hadronic model
Hubing Xiao, Zhihao Ouyang, Lili Yang et al. (+6 more)
Blazars are promising candidates for high energy
neutrino sources, yet the physical origin of their
neutrino emission remains uncertain. In this work, we extend our previous study by modeling the broadband spectral energy distributions (SEDs) of 103
neutrino blazar candidates (NBCs) within a hadronic framework. To estimate the maximum possible
neutrino output, we adopt an assumption in which the high energy emission is dominated by p gamma interactions and the contribution from leptonic inverse Compton scattering is strongly suppressed. From the SED modeling, we constrain nine key parameters describing the emission region and particle energy distributions. We perform a partial correlation analysis to investigate the relationship between
neutrino luminosity and electromagnetic emission, and we found a weak or moderate correlation between optical R band and
neutrino emission. Our model predicts prominent
proton synchrotron emission peaking in the MeV band for most sources, with 99 out of 103 NBCs exhibiting
proton synchrotron peaks within 0.1 to 100 MeV, highlighting the MeV band as a key window for distinguishing between leptonic and hadronic scenarios. Based on the model-predicted maximum
neutrino fluxes, we find that three NBCs are potentially detectable by IceCube, while up to 22, 45, and 62 sources may be detectable by KM3NeT, NEON, and TRIDENT, respectively. These results provide testable predictions for future multi-messenger observations and offer new insights into the composition and radiation mechanisms of blazar jets.
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All authors Hubing Xiao, Zhihao Ouyang, Lili Yang, Jingtian Zhu, Minfeng Gu, Liang Chen, Shaohua Zhang, Zhijian Luo, Junhui Fan
Solar and Stellar Astrophysics
The Stellar Abundances and Galactic Evolution Survey (SAGES). V. The First Data Release of the DDO51 Band
Qiqian Zhang, Zhou Fan, Gang Zhao et al. (+20 more)
We present the first public data release of DDO51 band from the
Stellar Abundances and
Galactic Evolution Survey (SAGES), based on Nanshan One-meter Wide-field
Telescope (NOWT) observations obtained between 2023 September and 2024 January. This release initiates the DDO51-band component of the survey, covering $\sim$ 2,500 deg$^2$ of the northern sky and including more than 10 million sources. The DDO51 filter is centered near the \ion{Mg}{1}~$b$ triplet and the adjacent MgH feature, offering sensitivity to
stellar surface
gravity. The data reduction pipeline incorporates an improved astrometric solution anchored to
Gaia DR3 and a photometric calibration strategy tied to synthetic photometry from
Gaia XP spectra. These procedures yield a point-source depth of $\sim$18.9 mag at S/N$\sim$10 and an internal photometric precision $\approx$6-7 mmag at the bright end. A preliminary color–color analysis using
Gaia broadband photometry confirms the expected sensitivity of the DDO51 band to
stellar surface
gravity, demonstrating a clear photometric separation between
dwarf and
giant sequences for late-type
stars. This
dataset, when combined with existing SAGES photometry in other bands, provides a crucial tool for disentangling the substructures of the Milky Way. All data products from this release upon publication will be available.
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All authors Qiqian Zhang, Zhou Fan, Gang Zhao, Kai Xiao, Wei Wang, Hongrui Gu, Jie Zheng, Jingkun Zhao, Chun Li, Yuqin Chen, Haibo Yuan, Haining Li, Kefeng Tan, Yihan Song, Ali Luo, Nan Song, Yujuan Liu, Yaqian Wu, Ali Esamdin, Hubiao Niu, Jinzhong Liu, Guojie Feng, Yu Zhang
Earth and Planetary Astrophysics
Coupling magma-ocean and atmospheres in spectral retrievals of sub-Neptunes
Yuichi Ito and Quentin Changeat
Recent high-precision atmospheric observations with JWST is enabling detailed characterization of sub-Neptune atmospheres and motivating efforts to understand and constrain their interiors. Theoretical studies suggest that sub-Neptunes possibly host hydrogen-dominated atmospheres that are chemically coupled with an underlying magma ocean. However, a quantitative
retrieval framework directly linking atmospheric spectra to magma ocean properties has yet to be established. Here we introduce MELTYQ, a coupled magma-atmosphere
retrieval framework that links transmission spectra to the oxidation state and volatile inventory of underlying magma oceans. MELTYQ combines a magma-atmosphere
equilibrium model, which includes the solubility of H-/O-/C-/N-bearing species in the melt and redox reactions, with a
Bayesian spectral
retrieval scheme. Using simulated
retrieval tests, we validate the approach and show that magma redox state and volatile content can be constrained under favorable observational conditions. As a proof of concept, we apply MELTYQ to JWST transmission spectra of the
benchmark sub-Neptunes K2-18 b and TOI-270 d. We find that coupled magma-atmosphere
retrievals are generally capable of reproducing the observed spectra of these
planets. However, we identify several key limitations in the current framework. Specifically: more flexible free-
retrieval approaches remain statistically preferred; the CO/CO$_2$ absorption feature near 4.5 $\mu$m for TOI-270 d is not fully captured; and a number of underlying model assumptions may not be strictly valid. Nevertheless,
embedding coupled magma-atmosphere models directly within
Bayesian retrievals enables quantitative assessment of degeneracies and sensitivities, establishing a pathway for directly connecting atmospheric spectra to magma composition in this underexplored
exoplanet regime.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
General Grad-Shafranov Equation
Ye Shen
To effectively describe the
plasma with strong
magnetic field, the force-free electrodynamics was introduced, within which the Grad-Shafranov equation plays the key role. The Grad-Shafranov equation governs the global structure of a electromagnetic field in
equilibrium with
symmetries. It is widely applicable in an amount of scenarios, such as the tokamak, the
solar corona, the magnetosphere of Earth,
neutron star and black hole, etc. However, in different situations, the Grad-Shafranov equation is expressed differently, and the derivations might be complicated. In this work, via the
language of differential form, we provide a general expression of Grad-Shafranov equation, from which the expression in any specific situation can be quickly obtained. Additionally, we present a Lagrangian density for a scalar field whose on-shell condition is precisely the Grad-Shafranov equation.
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Cosmology and Nongalactic Astrophysics
Gravitational-wave standard sirens and application in cosmology
Wen Zhao, Liang-Gui Zhu and Youjun Lu
The discovery of the gravitational-wave event GW170817 from a binary
neutron star merger, together with its multi-wavelength electromagnetic counterparts, marks the beginning of the era of multi-messenger gravitational-wave astronomy. Observations of gravitational-wave signals from compact binary mergers enable an independent measurement of the luminosity distance to the source. This implies that gravitational-wave sources can serve as "standard sirens" to probe the expansion history of the Universe, providing a new approach to constrain cosmological parameters. In this paper, we review the basic principles of using gravitational-wave standard sirens to constrain cosmology. We discuss various methods for determining the source distance and
redshift, as well as the capabilities of second- and third-generation ground-based detectors and space-based detectors in constraining cosmological parameters, especially the Hubble constant and dark energy parameters. By examining three types of standard sirens: binary
neutron star mergers with electromagnetic counterparts as bright sirens,
stellar-mass binary black hole mergers as dark sirens, and the dark lensed sirens, we illustrate the methodology, challenges, and future prospects of the standard siren approach.
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Instrumentation and Methods for Astrophysics · Cross-listed from cond-mat.supr-con
Quasiparticle Quality Factors in Superconducting Resonators: Effects of Bath Temperature and Readout Power
Zhenyuan Sun, S Withington and Songyuan Zhao
The performance of superconducting resonators underpins a wide range of modern
quantum technologies, yet their quality factor often deviates at low temperatures from standard Mattis-Bardeen predictions. This discrepancy is often attributed to nonthermal quasiparticles generated by microwave readout power, which limits the sensitivity of superconducting devices. We present a macroscopic model based on modified Rothwarf-Taylor equations that incorporates a power-dependent
phonon generation term, providing an explicit relationship between quality factor, bath temperature and readout power. The model shows excellent agreement with temperature sweep measurements of NbN microstrip resonators with e̱ta}-Ta terminations over a wide dynamic range of readout power levels, accurately capturing the transition between thermally-dominated and microwave-induced loss regimes. This framework provides a predictive tool for optimizing superconducting resonators and advancing the design of high-Q devices for
quantum sensing and
quantum information processing.
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