Instrumentation and Methods for Astrophysics
Ray-trax: Fast, Time-Dependent, and Differentiable Ray Tracing for On-the-fly Radiative Transfer in Turbulent Astrophysical Flows
Lorenzo Branca, Rune Rost and Tobias Buck
Radiative transfer is a key bottleneck in computational astrophysics: it is nonlocal, stiff, and tightly coupled to hydrodynamics. We introduce Ray-trax, a GPU-oriented, fully differentiable 3D ray tracer written in JAX that solves the time-dependent emission–absorption problem and runs directly on turbulent gas fields produced by hydrodynamic simulations. The method favors the widely used on-the-fly emission–absorption approximation, which is state of the art in many production hydro codes when scattering is isotropic. Ray-trax vectorizes across rays and sources, supports arbitrarily many frequency bins without architectural changes, and exposes end-to-end gradients, making it straightforward to couple with differentiable hydro solvers while preserving differentiability. We validate against analytical solutions, demonstrate propagation in turbulent media, and perform a simple inverse problem via gradient-based optimization. In practice, the
memory footprint scales as $\mathcal{O}(N_{\text{src}}\,N_{\text{cells}})$ while remaining highly efficient on accelerators.
Read the full abstract ▾
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Imaging and polarization patterns of various thick disks around Kerr-MOG black holes
Xinyu Wang, Huan Ye and Xiao-Xiong Zeng
We investigate the imaging and polarization properties of Kerr-MOG black holes surrounded by geometrically thick
accretion flows. The MOG parameter $\alpha$ introduces deviations from the Kerr metric, providing a means to test modified
gravity in the strong field regime. Two representative
accretion models are considered: the phenomenological radiatively inefficient
accretion flow (RIAF) and the analytical ballistic approximation
accretion flow (BAAF). Using general relativistic radiative transfer, we compute synchrotron emission and polarization maps under different
spins, MOG parameters, inclinations, and observing frequencies. In both models, the
photon ring and central dark region expand with increasing $\alpha$, whereas frame dragging produces pronounced brightness asymmetry. The BAAF model predicts a narrower bright ring and distinct polarization morphology near the event horizon. By introducing the net polarization angle $\chi_{\text{net}}$ and the second
Fourier mode $\angle\beta_2$, we quantify inclination- and frame-dragging-induced polarization features. Our results reveal that both $\alpha$ and
spin significantly influence the near-horizon polarization patterns, suggesting that high-resolution polarimetric imaging could serve as a promising probe of modified
gravity in the strong field regime.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Recombination Clumping Factor of Physically Defined Intergalactic Medium at the Epoch of Reionization
Yuri Oku and Renyue Cen
The recombination clumping factor, $C$, is a key parameter in modeling
cosmic reionization, but its value is sensitive to the definition of the Intergalactic Medium (IGM). We investigate the clumping factor using the Gamer-2 adaptive mesh refinement cosmological hydrodynamical simulation code. We introduce a new, physically-motivated definition of the IGM based on the effective transmission factor of ionizing
photons. We perform large-scale simulations with varying intensities of the uniform ultraviolet background, and we find that our physically-defined clumping factor is slightly lower than, yet comparable to, the values derived from traditional overdensity thresholds, within a factor of two. At $z=6$, we obtain a clumping factor of $C \sim 3$, consistent with previous studies, indicting that the clumping factor is robust to numerical resolution, box size, and the definition of the IGM. Our zoom-in simulations further show that
supernova feedback has two competing effects on reionization; it enhances recombination by increasing the density of ionized gas, while facilitating ionization by heating gas and reducing the neutral fraction. However, these effects are limited to the scales of $\sim$ 100 kpc and do not significantly alter the global clumping factor.
Read the full abstract ▾
Solar and Stellar Astrophysics
A magnetic field study of two fast-rotating, radio bright M dwarfs. StKM 1-1262 and V374 Peg
S. Bellotti, P.I. Cristofari, J.R. Callingham et al. (+8 more)
Radio observations at low frequencies are sensitive to the
magnetic activity of
stars and the
plasma environment surrounding them. The accurate interpretation of the processes underlying the
radio signatures requires a detailed characterisation of the
stellar magnetism. We study two M
dwarfs, StKM 1-1262 (M0 type, P$_\mathrm{rot}=1.24$ d) and V374 Peg (M4 type, P$_\mathrm{rot}=0.4455$ d), which were detected with the LOw Frequency ARray (LOFAR). StKM 1-1262 exhibited a type-II
radio burst, potentially resulting from a coronal mass ejection event. V374 Peg manifested low-frequency
radio emission typical of an electron-cyclotron maser instability emission mechanism. We analysed spectropolarimetric observations of these M
dwarfs collected with the SpectroPolarimètre InfraRouge (SPIRou). Firstly, we refined the
stellar parameters such as effective temperature, surface
gravity, and
metallicity, and measured the average surface
magnetic flux via modelling of Zeeman broadening in unpolarised spectra. We then applied Zeeman-Doppler imaging to least-squares deconvolution line profiles in circular polarisation to reconstruct their large-scale
magnetic fields. StKM 1-1262 has a total, unsigned
magnetic field of $3.53\pm0.06$ kG on average and the large-scale
magnetic field
topology is dipolar and moderately axisymmetric, with an average strength of 300 G. V374 Peg has an unsigned
magnetic field of $5.46\pm0.09$ kG and the large-scale field is dipolar and axisymmetric, with an average strength of 800 G. For StKM 1-1262, we found a strong anti-correlation between the total
magnetic field and the effective temperature which is reminiscent of the tight link between small-scale
magnetic fields and surface inhomogeneities. For V374 Peg, we found a moderate anti-correlation, possibly due to a more even distribution of surface features. (Abridged)
Read the full abstract ▾
All authors S. Bellotti, P.I. Cristofari, J.R. Callingham, J. Morin, P.Petit, A.A. Vidotto, M. Jardine, L. Arnold, R.D. Kavanagh, J. Llama, H. Vedantham
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A Unified Dark-Matter–Driven Relativistic Bondi Route to Black-Hole Growth from Stellar to Supermassive Scales
Chian-Shu Chen and Feng-Li Lin
Observations of luminous
quasars at $z\gtrsim7$ reveal supermassive black holes (SMBHs) with inferred masses $M_{\rm BH}\sim10^9 \, M_\odot$ formed within the first $\sim700$~Myr of
cosmic history. Standard growth channels – Eddington-limited gas
accretion and hierarchical mergers – face severe timescale restrictions. We consider a super-Eddington
accretion mechanism aided by the Bondi
accretion of a minimal model of self-interacting dark matter (SIDM). We demonstrate that in a critical regime with a near-relativistic sound speed, the Bondi
accretion yields an
accretion rate that depends only on the mass $m$ of SIDM, thus it is universal to the ambient environment. This critical
accretion mechanism for $m\gtrsim 10^{-2}\; {\rm eV}$ can grow seeds as small as $10\,M_\odot$
primordial black holes (PBH) in the early Universe into $10^9$ – $10^{10}\,M_\odot$ SMBHs by $z\sim7$ without fine-tuned environments. Therefore, given a mass distribution of PBHs and a value of $m$, the mass function of primary black holes at late time can be fully determined with masses ranging from
stellar to SMBHs. This connects the microscopic physics of dark matter to astrophysical observations of black holes.
Read the full abstract ▾
Astrophysics of Galaxies
Variability of optical spectral index to support a central sub-parsec binary black hole system in quasar SDSS J001224-102226.51
Zhang XueGuang
In this manuscript, variations in optical spectral index $\alpha_{5100}$ are applied for detecting central sub-parsec binary black hole systems (sub-pc BBHs) in broad line active
galactic nuclei (BLAGN), due to apparent effects of obscurations on central two BH accreting systems. For sub-pc BBHs in BLAGN, two main characteristics on $\alpha_{5100}$ can be expected. First, if a BLAGN harbours a central sub-pc BBH, the expected unique variability in $\alpha_{5100}$ should lead the BLAGN to be an outlier in the space of $\alpha_{5100}$ versus continuum luminosity $L_{5100}$ determined from normal BLAGN. Second, BLAGN harbouring central sub-pc BBHs could lead to periodic variations in $\alpha_{5100}$. Here, after checking the two-epoch SDSS spectra of
quasar SDSS J0012-1022 reported as a candidate of sub-pc BBH by large velocity offset between narrow and broad Balmer emission lines, unique variability of $\alpha_{5100}$ can be explained by effects of obscurations related to an assumed central sub-pc BBH. In the near future, to detect and report periodic variations of $\alpha_{5100}$ for sub-pc BBHs in BLAGN should be our main objective. The results provide a new method by applications of properties of optical continuum emissions for detecting sub-pc BBHs in BLAGN.
Read the full abstract ▾
Solar and Stellar Astrophysics
Occurrence rate of stellar Type II radio bursts from a 100 star-year search for coronal mass ejections
David C. Konijn, Harish K. Vedantham, Cyril Tasse et al. (+8 more)
Coronal mass ejections (CMEs) are major drivers of space weather in the
Solar System, but their occurrence rate on other
stars is unknown. A characteristic (deca-)metric
radio burst with a time-frequency drift, known as a Type II
radio burst, is a key observational signature of CMEs. We searched a total of 107 years of
stellar data using time-frequency spectra that targeted all known
stars within 100 parsecs in the LOFAR Two Metre Sky Survey (LoTSS) up to May 2023. This resulted in the largest unbiased search for circularly polarised
stellar Type II metric
radio bursts to date, with a typical 3$\sigma$ sensitivity of 2.5 mJy for an integration time of 1 minute. We detected two drifting
stellar radio bursts: the published 2-minute burst from the M
dwarf StKM 1-1262 and a new 13-minute burst from the M
dwarf LP 215-56. The new burst is characterised by a drift rate of $-0.060^{+0.002}_{-0.002}$ MHz s$^{-1}$, an average Stokes V flux density of $-4.5^{+1.4}_{-1.3}$ mJy, and a temporal duration of $63^{+31}_{-11}$ seconds. We constrained the occurrence rate of drifting
stellar bursts by calculating Poisson upper and lower limits based on the two drifting bursts. We also fitted a cumulative burst luminosity distribution to the data using the burst detections and the non-detections; this yielded a power law index ($\alpha$) of $-0.7^{+0.9}_{-0.6}$ and a normalisation point (N) of one burst per year with $E>6.8\times10^{13}$ erg s$^{-1}$ Hz$^{-1}$. We find an agreement between this and the cumulative luminosity distribution of decametric SOHO/LASCO
solar Type II data ($\alpha = -0.81 \pm 0.06 \pm 0.02$), which suggests that the current scarcity of detected
stellar Type II bursts is likely due to limited sensitivity rather than to the intrinsic rarity of these events. Additionally, we identify 19 circularly polarised
stellar radio bursts without a time-frequency drift.
Read the full abstract ▾
All authors David C. Konijn, Harish K. Vedantham, Cyril Tasse, Timothy W. Shimwell, Martin J. Hardcastle, Joseph R. Callingham, Ekaterina Ilin, Alexander Drabent, Philippe Zarka, Floris F.S. van der Tak, Sanne Bloot
Solar and Stellar Astrophysics
Radio Burst from a Stellar Coronal Mass Ejection
J. R. Callingham, C. Tasse, R. Keers et al. (+15 more)
Coronal mass ejections (CMEs) are massive expulsions of magnetised
plasma from a
star, and are the largest contributors to space weather in the
Solar System. CMEs are theorized to play a key role in planetary atmospheric erosion, especially for
planets that are close to their host
star. However, such a conclusion remains controversial as there has not been an unambiguous detection of a CME from a
star outside of our Sun. Previous
stellar CME studies have only inferred the presence of a CME through the detection of other types of
stellar eruptive events. A signature of a fast CME is a Type II
radio burst, which is emitted from the shock wave produced as the CME travels through the
stellar corona into interplanetary space. Here we report an analogue to a Type II burst from the early M
dwarf StKM 1-1262. The burst exhibits identical frequency, time, and polarisation properties to fundamental
plasma emission from a
solar Type II burst. We demonstrate the rate of such events with similar
radio luminosity from M
dwarfs are 0.84$^{+1.94}_{-0.69} \times$10$^{-3}$ per day per
star. Our detection implies that we are no longer restricted to extrapolating the
solar CME kinematics and rates to other
stars, allowing us to establish the first observational limits on the impact of CMEs on
exoplanets.
Read the full abstract ▾
All authors J. R. Callingham, C. Tasse, R. Keers, R. D. Kavanagh, H. Vedantham, P. Zarka, S. Bellotti, P. I. Cristofari, S. Bloot, D. C. Konijn, M. J. Hardcastle, L. Lamy, E. K. Pass, B. J. S. Pope, H. Reid, H. J. A. Röttgering, T. W. Shimwell, P. Zucca
Astrophysics of Galaxies
Little red dots as embryos of active galactic nuclei
Jian-Min Wang, Yi-Lin Wang, Yong-Jie Chen et al. (+7 more)
As an unprecedented large population in the early universe, the JWST-discovered little red dots (LRDs) have garnered much
attention for formation of massive black holes and
galaxies, but their nature remains a mystery. The LRDs appearing as “Chimeras" like both active
galactic nuclei (AGNs) and
galaxies have stimulated renewed interest in the roadmap of central massive black hole (cMBH) formation in AGNs. In this paper, we suggest that the LRDs contain $M_{\bullet}\lesssim 10^6\,M_{\odot}$ cMBHs as demonstrated by the Sołtan argument and there is a large population of
stellar-mass black holes (sMBHs with total mass of $\mathscr{M}_{m_{\bullet}}$) embedded inside cMBH
accretion disks (cMBH-disk) as motivated by anomalous reverberations of broad H$\beta$ line in local AGNs. This embryo structure of LRDs ($M_{\bullet}<\mathscr{M}_{m_{\bullet}}$) is formed as a consequence of gravitational collapse of
primordial clouds. In this Chimera,
accretion onto sMBHs powers the rest-frame optical continuum of the LRDs but the UV continuum is jointly contributed by slim parts of the cMBH-disks and
nuclear starbursts in the core of collapsing clouds governing the appearance of the observed V-shaped spectral energy distributions (SEDs). Outflowing clumped-envelopes are unavoidably formed by radiation pressure leading to absorption features of the Balmer lines. The present model works very well for LRDs' SEDs and avoids the issues of overly massive cMBHs.
Evolution of LRDs is briefly discussed including gravitational waves.
Read the full abstract ▾
All authors Jian-Min Wang, Yi-Lin Wang, Yong-Jie Chen, Jun-Rong Liu, Yu-Yang Songsheng, Cheng Cheng, Yan-Rong Li, Pu Du, Hao Zhang, Yu Zhao
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Impact of reactor antineutrinos on the neutrino floor in low-mass WIMP-like dark matter searches
S. Das, V. K. S. Kashyap and B. Mohanty
The sensitivity of conventional direct dark matter searches for weakly interacting massive particles (WIMPs) is ultimately limited by coherent elastic
neutrino-
nucleus scattering (CEvNS), which produces
nuclear recoils indistinguishable from WIMP signals and defines the so-called
neutrino floor. While the effects of
solar neutrinos, geoneutrinos, diffuse
supernova neutrinos, and atmospheric
neutrinos have been extensively studied in this context, the contribution from reactor antineutrinos has received comparatively little
attention. We present the first systematic evaluation of how reactor antineutrino fluxes, modeled as a function of reactor-detector distance, modify the
neutrino floor for low-mass WIMP searches using SuperCDMS-like high-voltage germanium detectors. Both discovery-limit and opacity-based formulations of the
neutrino floor are examined under consistent assumptions. We find that proximity to gigawatt-scale reactors within 10 km can raise the
neutrino floor by up to a few orders of magnitude, significantly reducing the sensitivity to sub-10 GeV/c^2 dark matter. Beyond 100 km, the reactor contribution becomes negligible. These conclusions hold for both definitions of the
neutrino floor and remain stable under reasonable variations in detector quenching, site-dependent geoneutrino flux, and reactor antineutrino flux uncertainties, emphasizing reactor proximity as a critical factor in site selection for future low-threshold dark matter experiments.
Read the full abstract ▾
Astrophysics of Galaxies
Interstellar medium phases and abundances in the central parsec: A JWST MIRI/MRS view of the Galactic center
P.Vermot, A. Ciurlo, D. Rouan et al. (+8 more)
We used newly obtained observations from the Mid-Infrared Instrument (MIRI) equipped with the Medium Resolution Spectrometer (MRS) aboard the James Webb Space
Telescope (JWST) to extract spectra covering the entire spectral range from 5 to 27~$\mu$m in the CND and in the CC. We used the photoionization code CLOUDY to generate synthetic spectra with the same spectral range and resolution, simulating a wide range of gas phases and abundances. We then determined the contribution of each phase to the spectra. Once the abundances and contribution from each phase of the gas were determined, we identified four dominant phases and performed a spatial analysis to determine their contribution to each spaxel of the datacubes. We find that in both the CND and the CC, the bulk of the emission originates from warm ionized gas with temperatures of between $10^4$ and $10^{4.8}$~K. In the CND, molecular gas contributes significantly to the flux and is spatially structured, while the CC shows minimal molecular gas content, as is expected from these regions. Coronal gas is detected in both regions at the interface between molecular and warm ionized gas. The observed abundance pattern (enhanced CNO and $\alpha$ elements with suppressed Fe) indicates a chemically young environment, recently enriched by core-collapse
supernovae and
stellar winds, with a limited contribution from older Type Ia
supernovae. This favors a scenario of massive, recent
star formation rather than cumulative long-term enrichment.
Read the full abstract ▾
All authors P.Vermot, A. Ciurlo, D. Rouan, M.R. Morris, E. Bron, J. Le Bourlot, F. Le Petit, J. Qiu, A. Togi, A. Ghez T. Do, J.R. Lu
Earth and Planetary Astrophysics
Numerical Simulation of Impact Cratering and Induced Seismic Waves in Sand Targets
Kenji Kurosaki and Masahiko Arakawa
Impact cratering plays a crucial role in shaping the surfaces of small bodies, satellites, and
planets, providing insights into their formation and the history of the
Solar System. Small bodies are often covered with low-cohesion regolith. Using sand as a model of regolith, we constructed a numerical model for simulating impact on a sand target to investigate the mechanisms of crater formation and impact-induced seismic waves. Soda-lime glass and quartz sand targets were used for comparison. The developed sand model successfully reproduced the sound velocity measured in an experimental study. Using the new sand model, the crater formation was simulated using Smoothed Particle Hydrodynamics with a material strength parameter. The crater radius and $\pi$-scaling law derived from the numerical simulation were consistent with the experimental study. The vertical acceleration around the surface of the crater was consistent with the experimentally measured acceleration for the impact-induced seismic wave. The developed model can provide insight for predicting the size of craters on unknown small bodies.
Read the full abstract ▾
Astrophysics of Galaxies
Emission-Line and Continuum Reverberation Mapping of the NLS1 Galaxy WPVS 48
M.A. Probst, W. Kollatschny, M.W. Ochmann et al. (+6 more)
WPVS 48 is a nearby narrow-line Seyfert 1
galaxy without previous analysis of the broad-line region (BLR) by means of optical spectroscopic reverberation mapping. By studying the continuum and emission line variability of WPVS 48, we aim to infer the BLR size as well as the mass of the central supermassive black hole (SMBH). We analyse data from a dedicated optical spectroscopic reverberation mapping campaign of WPVS 48 taken with the 10 m Southern African Large
Telescope (SALT) at 24 epochs over a period of 7 months between December 2013 and June 2014. WPVS 48 shows variability throughout the campaign. We find a stratified BLR, where the variability amplitude of the integrated emission lines decreases with distance to the ionizing continuum source. Specifically, the variable emission of H$\alpha$, H$\beta$, H$\gamma$, He I $\lambda5876$ originates at distances of $16.0^{+4.0}_{-2.0}$, $15.0^{+4.5}_{-1.9}$, $12.5^{+3.5}_{-2.5}$ and $14.0^{+2.5}_{-2.1}$ light-days, respectively, to the optical continuum at 5100 A. The He II $\lambda 4686$ lag is $\lesssim 5$ days. Based on the high S/N spectra, we identify variable emission of N III $\lambda4640$ and C IV $\lambda4658$ in the line complex with He II $\lambda 4686$. We derive interband continuum delays increasing with wavelength up to $\sim 8$ days. These delays are consistent with an additional diffuse continuum originating at the same distance as the variable Balmer emission. We derive a central black hole mass of $(1.3_{-0.6}^{+1.1})\times10^7M_{\odot}$ based on the integrated line-widths and distances of the BLR and discuss corrections for the inclination angle. This gives an Eddington ratio $L/L_{\text{Edd}}\approx 0.39$ without correction for inclination.
Read the full abstract ▾
All authors M.A. Probst, W. Kollatschny, M.W. Ochmann, C. Sobrino Figaredo, D. Chelouche, M. Haas, S. Kaspi, L. Meerwart, T.-O. Husser
High Energy Astrophysical Phenomena
Not all roads lead to merger: AGN disc properties influence the interactions of highly unequal mass black holes
Jordan W. N. Moncrieff, Evgeni Grishin, Alessandro A. Trani et al. (+2 more)
As the number of gravitational-wave detections of black hole binaries grows, so does the diversity of proposed formation channels. The growing sample of systems with highly unequal masses, such as GW190814 with $m_1=23.2\,M_{\odot}$ and $m_2=2.59\,M_{\odot}$ – corresponding to a mass ratio $q=0.112$ – cannot be readily explained by isolated binary
evolution and may originate through dynamical assembly in an active
galactic nucleus (AGN). We investigate AGN discs capable of producing GW190814-like mergers using pAGN to model self-consistent AGN torques, coupled with TSUNAMI, a regularised N-body code including post-Newtonian terms up to 3.5 order. Suites of N-body simulations reveal possible outcomes of binary capture and merger, mean-motion resonance interactions, and other novel dynamical pathways. We develop analytical models linking the branching ratios of captures and mergers to local disc properties, applicable to black hole populations across all mass ratios. Capture probability is primarily governed by $\mathscr{B}$, the ratio of libration time to resonance-width crossing, and is well-described by a log-Gaussian, $P(\rm{capture}|\mathscr{B}) = A \exp[-(\ln \mathscr{B}-\mu)^2/2\sigma^2]$, with $A = 0.41^{+0.04}_{-0.04}$, $\mu = 1.09^{+0.08}_{-0.07}$, $\sigma = 1.05^{+0.08}_{-0.07}$. This fit, while an upper limit, is useful for simplified population synthesis. Finally, we explore the mass ratio AGN luminosity parameter space and find that GW190814 may be formed in a low luminosity AGN of $L_{\rm AGN}\approx 10^{43.5}\ \rm erg\ s^{-1}$. A more systematic parameter space exploration and future population studies will further test our predictions.
Read the full abstract ▾
All authors Jordan W. N. Moncrieff, Evgeni Grishin, Alessandro A. Trani, Fiona H. Panther, Olga Pietrosanti
Solar and Stellar Astrophysics
Superhot (> 30 MK) flare observations with STIX: Joint spectral fitting
Muriel Zoë Stiefel, Natália Bajnoková and Säm Krucker
Spectroscopic analysis of large
flares (>X1) in the hard X-ray (HXR) range offers unique insights into the hottest (> 30 MK)
flare plasma, the so-called superhot thermal component. To manage the high count rates in large
flares, an attenuator is typically placed in front of the HXR detectors. However, this significantly limits the spectral diagnostic capabilities at lower energies, and consequently, it restricts the analysis of the lower temperatures in
flares. The Spectrometer/
Telescope for Imaging X-rays (STIX) on board the
Solar Orbiter mission was designed to observe
solar flares in hard X-rays. The imaging detectors use an attenuator during periods of high flux level. In contrast, the background (BKG) detector of STIX is never covered by the attenuator and is therefore dedicated to measure the unattenuated flux using differently sized apertures placed in front of the detector. We aim to demonstrate that joint spectral fitting using different detector configurations of STIX allows us to reliably diagnose both the hot and the superhot components in large
flares. We jointly fit the HXR spectra of the STIX BKG detector and the STIX imaging detectors using SUNKIT-SPEX software package to determine the spectral parameters of both the hot and superhot thermal components in
solar flares. Using joint fitting on 32 STIX
flares, we corroborate that for GOES X-class
flares, the HXR spectrum is better represented by two thermal components instead of an isothermal component. At the temperature peak time, the superhot HXR flux above 15 keV is typically stronger than the hot HXR flux. The GOES long-wavelength channel is dominated by the hot component with a superhot contribution up to 10%. This paper demonstrates that joint spectral fitting of the same detector type with different attenuation schemes is a simple and powerful method to monitor multithermal
flare plasma.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Detection of Multiband Lensed Gravitational Waves from Dark Matter Halos with Deep Learning
Mengfei Sun, Jie Wu, Qianning Hu et al. (+6 more)
Lensed gravitational waves acquire amplitude and phase modulations when propagating through the gravitational potential of dark matter
halos, producing interference structures in the observed waveform. However, these features are often difficult to identify in detector noise. In this work, we develop a deep learning framework for the automatic classification of lensed gravitational wave signals under multiband observations. We simulate binary
neutron star signals observed by the space based detector DECIGO and the ground based Einstein
Telescope, and construct five classes of data including pure noise, unlensed signals, and three lensed cases generated by the SIS, CIS, and NFW dark matter
halo models. By comparing single detector and joint detector configurations, we evaluate the classification performance under different observational settings. The results show that multiband observations significantly improve the identification of lensed signals and reduce confusion among different lens models. This approach provides an efficient method for automated recognition of lensed gravitational waves in future multiband gravitational wave observations.
Read the full abstract ▾
All authors Mengfei Sun, Jie Wu, Qianning Hu, Jin Li, Nan Yang, Xianghe Ma, Borui Wang, Minghui Zhang, Yuanhong Zhong
High Energy Astrophysical Phenomena
Multiwavelength spectral and temporal analysis of VHE Blazar 1ES 1959+650: Tracing emission mechanisms across flux states
Peer Anjum, Athar A. Dar, Zahir Shah et al. (+2 more)
The high-synchrotron-peaked BL Lac object 1ES\,1959+650 exhibited pronounced activity between MJD~60310 – 60603, including a very high energy (VHE) detection reported by LHAASO. To investigate the underlying emission mechanisms, we performed a comprehensive temporal and spectral analysis using multiwavelength data from Swift-XRT/UVOT and
Fermi-LAT, covering the optical/UV to GeV $\gamma$-ray bands. The source shows strong energy-dependent variability, with the largest fractional variability in $\gamma$-rays, followed by X-rays and UV/optical, consistent with leptonic emission scenarios. Based on the variability patterns, we identified distinct flux states (F1, F2, F3, F4, F5, VHE-FX1, and VHE-FX2). The X-ray spectra exhibit a clear “harder-when-brighter” trend across these states. We modeled the broadband spectral energy distributions (SEDs) using a one-zone model incorporating synchrotron and synchrotron self-Compton (SSC) emission, implemented in xspec using $\chi^{2}$ minimization. During the VHE detection, the corresponding X-ray/optical emission likely resembled the F2 state. Modeling the VHE SED using F1-state data led to an SSC overprediction of the VHE flux, whereas all other states were well described within the one-zone framework. Systematic trends in physical parameters are observed across flux states, including spectral hardening, increasing break energy, rising bulk Lorentz factor, and decreasing
magnetic field with increasing flux. These results suggest that enhanced particle acceleration efficiency and stronger Doppler boosting drive the observed flaring activity, while the decrease in
magnetic field indicates conversion of
magnetic energy into particle kinetic energy, consistent with shock-driven scenarios.
Read the full abstract ▾
All authors Peer Anjum, Athar A. Dar, Zahir Shah, Bari Maqbool, Ranjeev Misra
Astrophysics of Galaxies
J-PAS: A Neural Network Approach to Single Stellar Population Characterization
H. Domínguez Sánchez, P. Coelho, G. Bruzual et al. (+28 more)
J-PAS (Javalambre Physics of the Accelerating Universe Astrophysical Survey) will present a groundbreaking photometric survey covering 8500 deg$^2$ of the visible sky from Javalambre, capturing data in 56 narrow band filters. This survey promises to revolutionize
galaxy evolution studies by observing $\sim$10$^8$
galaxies with low spectral resolution. A crucial aspect of this analysis involves predicting
stellar population parameters from the observed
galaxy photometry. In this study, we combine the exquisite J-PAS photometry with state-of-the-art single
stellar population (SSP) libraries to accurately predict
stellar age,
metallicity, and
dust attenuation with a neural network (NN) model. The NN is trained on synthetic J-PAS photometry from different SSP librares (E-MILES, Charlot & Bruzual, XSL), to enhance the robustness of our predictions against individual SSP model variations and limitations. To create mock samples with varying observed magnitudes we add artificial noise in the form of random Gaussian variations within typical observational uncertainties in each band. Our results indicate that the NN can accurately estimate
stellar parameters for SSP models without evident degeneracies, surpassing a
bayesian SED-fitting method on the same test set. We obtain median bias, scatter and percentage of outliers $\mu$ = (0.01 dex, 0.00 dex, 0.00 mag), $\sigma_{NMAD}$ = (0.23 dex, 0.29 dex, 0.04 mag), f$_{o}$ = (17 %, 24 %, 1 %) at $ i \sim$17 mag for age,
metallicity and
dust attenuation, respectively. The accuracy of the predictions is highly dependent on the signal-to-noise (S/N) ratio of the photometry, achieving robust predictions up to $i$ $\sim$ 20 mag.
Read the full abstract ▾
All authors H. Domínguez Sánchez, P. Coelho, G. Bruzual, A. Hernán-Caballero, C. López Sanjuan, J. A. Fernandez-Ontiveros, L.A. Díaz-García, L. Suelves, A. Álvarez-Candal, I. Breda, S. Gurung-López, V. Placco, J. Vega-Ferrero, J. M. Vílchez, R. Abramo, J. Alcaniz, N. Benitez, S. Bonoli, S. Carneiro, J. Cenarro, D. Cristóbal-Hornillos, R. Dupke, A. Ederoclite, C. Hernández-Monteagudo, A. Marín-Franch, C. Mendes de Oliveira, M. Moles, L. Sodré Jr, K. Taylor, J. Varela, H. Vázquez Ramió
Instrumentation and Methods for Astrophysics
Mock Observations for the CSST Mission: HSTDM–Synthetic Data Generation
SiYuan Tan, WenYin Duan, YiLong Zhang et al. (+9 more)
The High Sensitivity Terahertz Detection Module (HSTDM), a key component of the backend modules on board the China Space Station
Telescope (CSST), will offer great opportunities for the discovery of Terahertz Astronomy, with implications that extend well beyond China to the global astronomical community. It is imperative that the raw data collected by HSTDM undergoes meticulous calibration and processing through the HSTDM data processing pipeline (HSTDM pipeline for short) to ensure the accuracy and effectiveness of the final science data to be archived for further research. This process necessitates that the HSTDM pipeline address instrumental artifacts and effects as well as the coordination of data flow of the scheduled observing sequences under all observing modes of HSTDM within the CSST automated processing environment. As the understanding of CSST HSTDM data processing develops during the pipeline development stage, it becomes essential to assess the accuracy, the robustness and the performance of the HSTDM pipeline under all observing modes of HSTDM so that components of the HSTDM pipeline be rationally added, removed, amended or extended within the modular framework. In this paper, we develop practical simulation methods to facilitate this need. The contribution of synthetic data generation of HSTDM observation includes two parts: 1. HSTDM instrumental effect simulation based on both real testing profiles and simulated models; 2. Observing data flow generation based on HSTDM observing mode scenario. The simulation methods have been implemented and shown to be practical in testing the HSTDM pipeline during the development stage.
Read the full abstract ▾
All authors SiYuan Tan, WenYin Duan, YiLong Zhang, YiPing Ao, Yan Gong, ZhenHui Lin, Xuan Zhang, Yong Shi, Jing Tang, Jing Li, RuiQing Mao, Sheng-Cai Shi
Solar and Stellar Astrophysics
Models of long-period variables of the globular cluster 47 Tuc
Yu.A. Fadeyev
Stellar evolution computations were carried out for
stars with a main sequence mass $M_\mathrm{ZAMS}=0.86M_\odot$ and initial metal abundance $Z=0.003$ and $Z=0.004$. Selected models of evolutionary sequences were used for calculation of radial pulsations in the RGB, eAGB and TP-AGB evolutionary stages. Not all pulsating red
giants of the globular cluster 47 Tuc are shown to belong to the Mira variables because the lower limit of pulsation periods at the TP-AGB stage is $\approx 70$ day, whereas during the eAGB evolutionary stage the periods of radial oscillations range from $\approx 5$ to $\approx 40$ day. Periods and luminosities of hydrodynamic models of eAGB and TP–AGB pulsating
stars locate along the common period-luminosity relation. Small masses of Mira variables in the globular cluster 47 Tuc ($0.54M_\odot\le M\le 0.70M_\odot$) is the main reason for irregular large-amplitude oscillations and the dynamical instability of outer
stellar layers at pulsation periods $\Pi > 200$ day.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Emergent Dark Matter
Christian Canete and Archil Kobakhidze
We entertain the possibility that the phenomena typically attributed to dark matter may have a fundamentally emergent nature, rather than arising from new particle degrees of freedom. To illustrate this idea, we consider a field-theoretic model of a three-form gauge field coupled to a cosmological fluid composed of ordinary matter and radiation. In the absence of interactions, the 3-form gauge theory describes only a global, non-propagating state, which can be associated with dark energy. However, when coupled to the
cosmic fluid, the theory gives rise to an emergent, dynamical in-medium state. We identify this emergent state of the 3-form gauge field with dark matter. Thus, our proposal provides a unified framework for the dark sector of the universe within the context of an interacting three-form gauge theory. Furthermore, we speculate that the three-form field may have a gravitational origin, potentially supported by the
lepton-number asymmetry in the
primordial plasma. If this scenario is correct, conventional direct and indirect searches for dark matter would likely be futile.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Evolution of the radio source position uncertainties in radio astrometric catalogs over the past three decades
Zinovy Malkin
In this paper, progress in improving the coordinates uncertainty of extragalactic
radio sources derived from astrometric and geodetic VLBI observations is investigated. For this purpose, 30 catalogs of
radio source positions computed in 1997-2025 were analyzed. Over these years, the median source position uncertainty represented by the semi-major axis of the error ellipse for 467 sources in common to all catalogs improved by one order of magnitude: from 0.156 mas to 0.015 mas. It was also found that the improvement in the position uncertainty over time follows a power law with high accuracy. The number of observations used for determination of the coordinates of the common sources in the input catalogs increased over time from 1.3 to 14.4 million, also following a power law. A discussion of the results led us to the conclusion that the number of observations is the primary factor in improving the source positions uncertainty compared to the number of sessions in which the source was observed.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Design of a Six-band, 2.4-Octave (80–420 GHz) Hierarchically Summed Phased-Array Slot-Dipole Antenna Array for NEW-MUSIC
Xiaolan Huang, Shibo Shu, Miao Li et al. (+2 more)
The Next-generation Extended Wavelength Multi-band Sub/millimeter Inductance Camera (NEW-MUSIC), located on the Leighton Chajnantor
Telescope (LCT), will be the first six-band trans-millimeter wave polarimeter. This paper proposes a broadband, hierarchical phased-array
antenna with integrated band-defining filters necessary to realize NEW-MUSIC. It covers a spectral bandwidth of 2.4 octaves from 80~GHz to 420~GHz, a frequency range ideal for studying trans-millimeter emission from a range of time-domain sources, using the Sunyaev-Zeldovich effects to study hot
plasmas in
galaxy clusters and
galaxies, and to observe dusty sources, from
star-forming regions in our
galaxy to high-
redshift dusty,
star-forming
galaxies. To achieve these goals, three groups of superconducting lumped-element on-chip low-pass/band-pass filter-banks were designed to hierarchically sum the superconducting, broadband, non-resonant, slot-dipole
antenna arrays and band-pass filter the trans-mm light before outputting it on microstripline to detectors (KIDs in the case of NEW-MUSIC).
Read the full abstract ▾
All authors Xiaolan Huang, Shibo Shu, Miao Li, Sunil R. Golwala, Feng Liu
Solar and Stellar Astrophysics
Mingfu Shao, Hui Wang, Yuyang Li et al. (+17 more)
Solar flares, the most powerful explosive phenomena in the
solar system, may pose significant hazards to spaceborne satellites and ground-based infrastructure. Despite decades of intensive research, reliable
flare prediction remains a challenging task. Large
Language Models, as a milestone in artificial intelligence, exhibit exceptional general knowledge and next-
token prediction capabilities. Here we introduce JW-
Flare, the first
Multimodal Large
Language Models (MLLMs) explicitly trained for
solar flare forecasting through fine-tuning on textual physic parameters of
solar active regions and
magnetic field images. This method demonstrates state-of-the-art (SOTA) performance for large
flares prediction on the test
dataset. It effectively identifies all 79 X-class
flares from 18,949 test samples, yielding a True Skill Statistic (TSS) of 0.95 and a True Positive Rate (TPR) of 1.00, outperforming traditional predictive models. We further investigate the capability origins of JW-
Flare through explainability experiments, revealing that
solar physics knowledge acquired during pre-training contributes to
flare forecasting performance. Additionally, we evaluate models of different parameter scales, confirming the Scaling_Law of Large
Language Models in domain-specific applications, such as
solar physics. This study marks a substantial advance in both the scale and accuracy of
solar flare forecasting and opens a promising avenue for AI-driven methodologies in broader scientific domains.
Read the full abstract ▾
All authors Mingfu Shao, Hui Wang, Yuyang Li, Jiaben Lin, Jifeng Liu, Baolin Tan, Juan Guo, Yin Zhang, Jing Huang, Jiangtao Su, Yingzi Sun, Haiqing Xu, Jie Chen, Suo Liu, Yuanyong Deng, Liyue Tong, Yang Bai, Cunshi Wang, Kaifan Ji, Yuqing Zhou
High Energy Astrophysical Phenomena
The Dawn of Gravitational Wave Astronomy at Light-year Wavelengths: Insights from Pulsar Timing Arrays
Stephen R. Taylor
Arrays of precisely-timed millisecond
pulsars are used to search for gravitational waves with periods of months to decades. Gravitational waves affect the path of
radio pulses propagating from a
pulsar to Earth, causing the arrival times of those pulses to deviate from expectations based on the physical characteristics of the
pulsar system. By correlating these timing residuals in a
pulsar timing array (PTA), one can search for a statistically isotropic background of gravitational waves by revealing evidence for a distinctive pattern predicted by General Relativity, known as the Hellings & Downs curve. On June 29 2023, five regional PTA collaborations announced the first evidence for GWs at light-year wavelengths, predicated on support for this correlation pattern with statistical significances ranging from $\sim\!2-4\sigma$. The amplitude and shape of the recovered GW spectrum has also allowed many investigations of the expected source characteristics, ranging from a
cosmic population of supermassive binary black holes to numerous processes in the early Universe. In the future, we expect to resolve signals from individual binary systems of supermassive black holes, and probe fundamental assumptions about the background, including its polarization, anisotropy, Gaussianity, and stationarity, all of which will aid efforts to discriminate its origin. In tandem with new facilities like DSA-2000 and the SKA, fueling further observations by regional PTAs and the International
Pulsar Timing Array, PTAs have extraordinary potential to be engines of nanohertz GW discovery.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Search for host galaxies of unlocalized Fast Radio Bursts in the SDSS IV catalog
Luz Ángela García, Eduard Piratova-Moreno, Felipe González-Alarcón et al. (+1 more)
This theoretical work investigates different models to predict the
redshift of Fast
Radio Bursts (FRBs) from their observed dispersion measure (DM) and other reported properties. We performed an extensive revision of the FRBs with confirmed
galaxy hosts in the literature and compiled an updated catalog. With this sample of FRBs, composed of 117 unique transients, we explore four physically motivated models that relate the DM and
redshift ($z$): a linear trend (inspired by the Macquart relation), a log-
parabolic function, a power-law, and a combined model from the above. We assess the success of these theoretical proposals by implementing different statistical metrics and ranking them. The DM-$z$ relations are also tested using 100 realizations of 500 simulated FRBs, which follow the observed DM trends. Relying on our theoretical modeling, we establish the probability of $\sim$1000 FRBs with unknown $z$ (from the latest CHIME data release) to be hosted by
galaxies in the SDSS archival
dataset. Our validation scheme allows us to predict the FRBs with a probability threshold of $\geq$0.95 to originate in these
galaxies, using their 2D angular position in the sky, magnitude in the r-band, and
redshift. This statistical proposal will be tested with upcoming data releases from DESI and new generations of
galaxy surveys, such as Euclid, and it opens brilliant possibilities to localize these transients in an automatic pipeline.
Read the full abstract ▾
All authors Luz Ángela García, Eduard Piratova-Moreno, Felipe González-Alarcón, Jhonier Rangel
Instrumentation and Methods for Astrophysics
Improved Modeling of Quasi-Static Thermal and Optical Response of Lumped-Element Aluminum Manganese KIDs
Adriana Gavidia, Sunil Golwala, Andrew D. Beyer et al. (+11 more)
We report on the optical characterization of the AlMn kinetic inductance detectors (KIDs) in development for use in the Next-generation Extended Wavelength-MUltiband Sub/millimeter Inductance Camera (NEW-MUSIC) on the Leighton Chajnantor
Telescope (LCT). NEW-MUSIC will cover 80-420 GHz, split into six spectral bands, with polarimetry. This broad spectral coverage will enable study of a range of scientific topics such as the
accretion and feedback in
galaxies and
galaxy cluster
evolution via the Sunyaev-Zeldovich effect, the transient synchrotron emission from the explosive deaths of massive
stars and other time-domain phenomena, and dusty sources from low to high
redshift (with polarization). Al KIDs have already been demonstrated for bands 2-5. AlMn KIDs will be used for the 90~GHz band, as Al's pair-breaking energy is too high. However, AlMn has only barely been explored as a KID material. To this end, we first improved the modeling techniques used for Al KIDs within BCS theory by eliminating the use of analytical approximations for the expressions of the complex conductivity and found these changes reduced fit parameter degeneracy in the analysis of AlMn. Then, we tested the addition of a gap smearing parameter, a standard extension to BCS theory in use for high kinetic inductance materials, and found it did not improve the fits.
Read the full abstract ▾
All authors Adriana Gavidia, Sunil Golwala, Andrew D. Beyer, Daniel Cunnane, Peter K. Day, Fabien Defrance, Clifford F. Frez, Xiaolan Huang, Junhan Kim, Jean-Marc Martin, Jack Sayers, Shibo Shu, Shiling Yu, Yann Sadou
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Progress on the ALETHEIA project and a new approach to mitigate events overlap
Junhui Liao
The ALETHEIA project aims to search for low-mass dark matter using
liquid helium (LHe)-filled time projection chambers (TPCs). While
liquid argon and
liquid xenon TPCs have been extensively employed in the field of direct dark matter detection, successful development of LHe TPCs has not yet been achieved. Launched in 2020, our project has made significant progress since then. These advancements have convinced us that a single-phase LHe TPC is technologically feasible. Compared to
liquid xenon and
liquid argon TPCs, one of the unique challenges for LHe TPCs is event overlap caused by the 13-second lifetime scintillation. We will demonstrate that this overlap can be entirely mitigated when the LHe temperature is maintained near 1.0 K. At this temperature, electron mobility is three orders of magnitude higher than at approximately 4.0 K, which is the temperature we initially proposed for the LHe TPC.
Read the full abstract ▾
Astrophysics of Galaxies
Continuum variability in multi-epoch quasar spectra from the Sloan Digital Sky Survey
Minjin Kim, Suyeon Son and Luis C. Ho
We examine the continuum variability of active
galactic nuclei (AGNs) by analyzing the multi-epoch spectroscopic data from the Sloan Digital Sky Survey. To achieve this, we utilized approximately 2 million spectroscopy pairwise combinations observed across different epochs for $\sim90,000$ AGNs. We estimate the ensemble variability structure function (SF) for subsamples categorized by various AGN properties, such as black hole mass, AGN luminosity ($L$), and Eddington ratio, to investigate how AGN variability depends on these parameters. We found that the SFs are strongly correlated with $L$, Eddington ratio, and rest-frame wavelength ($\lambda$). The analysis, with each parameter held fixed, reveals that SFs depend primarily on $L$ and $\lambda$, but not on the Eddington ratio. Consequently, under the assumption that AGNs follow a universal SF, we found that the variability timescale ($\tau$) is proportional to both $L$ and $\lambda$, expressed as $\tau \propto L^{0.62\pm0.07} \lambda^{1.74\pm0.23}$. This result is broadly consistent with predictions from the standard
accretion disk model ($\tau \propto L^{0.5} \lambda^{2}$). However, when considering only shorter wavelengths ($\lambda \leq 3050$ Å) to minimize contamination from the host
galaxy and the Balmer continuum, the power-law index for $\lambda$ drops significantly to $1.12 \pm 0.24$. This value is lower than predicted by approximately $3-$4\ \sigma$, suggesting that the radial temperature profile may be systematically steeper than that predicted by the standard disk model, although other mechanisms may also contribute to this discrepancy. These findings highlight the power of temporal spectroscopic data in probing AGN variability, as they allow robust estimation of continuum fluxes without interference from strong emission lines.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Low-Frequency Noise Performance of Microstrip-Coupled Lumped-Element Aluminum KIDs using Hydrogenated Amorphous Silicon Parallel-Plate Capacitors for NEW-MUSIC
Simon Hempel-Costello, Andrew D. Beyer, Dan Cunnane et al. (+11 more)
We present measurements of the low-frequency noise of microstrip-coupled, lumped-element aluminum kinetic inductance detectors that use hydrogenated amorphous silicon parallel-plate capacitors (Al/a-Si:H MS-PPC-LEKIDs), which are under development for the Next-generation Extended Wavelength Multiband Submillimeter Inductance Camera (NEW-MUSIC). We show that, under dark conditions, these devices are generation recombination (GR) noise dominated down to 0.1 Hz and, under optical load, they are likely dominated by GR and
photon noise down to tenths of a Hz and possibly lower, both in spite of the use of a-Si:H PPCs. Our measurements set limits on the low-frequency two-level-system (TLS) noise of the a-Si:H material that are consistent with higher frequency measurements in the 0.1-10 kHz regime. These results establish that our MS-PPC-LEKID design for NEW-MUSIC will be
photon-noise-limited under a range of observing conditions and, more generally, that a-Si:H PPC-KIDs are a viable new detector technology for even low modulation-rate applications such as astronomy.
Read the full abstract ▾
All authors Simon Hempel-Costello, Andrew D. Beyer, Dan Cunnane, Peter K. Day, Fabien Defrance, Cliff Frez, Adriana Gavidia, Sunil R. Golwala, Junhan Kim, Jean-Marc Martin, Yann Sadou, Jack Sayers, Shibo Shu, Shiling Yu