High Energy Astrophysical Phenomena · Cross-listed from physics.plasm-ph
Kinetic route to helicity-constrained decay
Dion Li
Through two-dimensional, three-velocity-component particle-in-
cell simulations of freely decaying subion
turbulence, intermittent localized regions with $\mathbf{E} \cdot \mathbf{B} \neq 0$ are found, in the early electron-scale interaction phase, to be statistically associated with decreases in $|H_{V_s}|$, the fixed-gauge structure-integrated
magnetic-helicity diagnostic. This structure-level behavior coincides with a decline of the Saffman helicity-variance plateau value $I_H$. Motivated by these observations, we propose a source-compensated, history-dependent helicity density that satisfies an exact local balance identity by construction, enabling Saffman-type two-point correlation integrals, which, under standard flux-decorrelation assumptions, can exhibit intermediate-scale plateaus that are roughly time independent. In the simulations, such plateaus are observed to remain approximately invariant over the measured kinetic interval even as $I_H$ evolves during the early kinetic stage. Under approximate single-scale self-similarity, the plateau behavior of the
magnetic integral is consistent with the two-dimensional decay constraint $BL \sim \text{const}$. For initially net-helical configurations, we observe rapid development of mixed-signed
magnetic-helicity patches and a decrease of the global fractional helicity, such that the decay over the kinetic interval is again most consistent with the cancellation-dominated scaling constraint.
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Astrophysics of Galaxies
UV slopes of Starforming Galaxies in Strong Lensing fields at the Epoch of Reionization with JWST
Giordano Felicioni, Maruša Bradač, Yoshihisa Asada et al. (+20 more)
UV slopes ($\beta$) are a powerful diagnostics for
galaxies at the Epoch of Reionization, tracing
star formation, ISM ionization, and the escape fraction $f_{esc}$ of ionizing
photons. Studies at low and intermediate z find a gradual $\beta$ reddening with time and steeper slopes for fainter
galaxies, however recent JWST studies reveal a flattening of this trend at $z>7$. We want measure $\beta$ for
galaxies at $z>7.5$ using the strong
lensing around massive
galaxy clusters to observe high-
redshift and faint
galaxies. The low-brightness regime is of particular interest for reionization, as most of the recent models of this process posit that numerous faint
galaxies are the
prime drivers of reionization. We use NIRCam and NIRSpec data from CANUCS, Technicolor, JUMPS, Silver Bullet, UNCOVER and MEGASCIENCE across 7 strong
lensing fields. We find
galaxies down to $M_{UV}\sim-16$ and 7.5<z<12.5. We measure e̱ta} with a forward-modelling procedure and estimate $f_{esc}$ for a subsample with emission line data using a relation, calibrated from a low-z sample, with UV slope,
galaxy size and H$\beta$ equivalent width. We find 378
galaxies (45 with spectrum), yielding average values $\beta=-2.3\pm0.4$, $z=8.5\pm1.0$, and $M_{UV}=-18\pm1$. We find no significant $\beta$
evolution across our
redshift range, suggesting a flattening of the $\beta-z$ trend above $z\sim7.5$. We find a weak negative trend between $\beta$ and $M_{UV}$. For 14
galaxies we estimate an average $f_{esc}=0.26\pm0.22$. The flat trend of $\beta$ at $z>7.5$ suggests similar properties between $300$ and $600 Myr$ after the Big Bang. The weak trend between $\beta$ and $M_{UV}$ suggests an analogous composition for low- and high-mass
galaxies' ISM, likely due to a lack of time for
dust buildup. While average $f_{esc}$ is higher than necessary to ionize the IGM by z~6, the model extrapolated at low-z may overestimate its value.
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All authors Giordano Felicioni, Maruša Bradač, Yoshihisa Asada, Nicholas S. Martis, Ghassan T. E. Sarrouh, Guillaume Desprez, Gregor Rihtaršič, Naadiyah Jagga, Anishya Harshan, Jon Judež, Chris J. Willott, Roberto Abraham, Gabriel Brammer, Vince Estrada-Carpenter, Jasleen Matharu, Adam Muzzin, Gaël Noirot, Marcin Sawicki, Sunna Withers, Vladan Markov, Rosa M. Mérida, Vesna Pirc Jevšenak, Roberta Tripodi
High Energy Astrophysical Phenomena
Modeling of Relativistic Plasmas with a Conservative Discontinuous Galerkin Method
James Juno, Grant Johnson, Alexander Philippov et al. (+3 more)
We present a new method for solving the relativistic Vlasov–Maxwell system of equations, applicable to a wide range of extreme high-energy-density astrophysical and laboratory environments. The method directly discretizes the kinetic equation on a high-dimensional phase-space grid using a discontinuous Galerkin finite element approach, yielding a high-order, conservative numerical scheme that is free from the Poisson noise inherent to traditional Monte-Carlo methods. A novel and flexible velocity-space mapping technique enables the efficient treatment of the wide range of energy scales characteristic of relativistic
plasmas, including QED pair-production discharges, instabilities in strongly magnetized
plasmas surrounding
neutron stars, and relativistic
magnetic reconnection. Our noise-free approach is capable of providing unique insight into
plasma dynamics, enabling detailed analysis of electromagnetic emission and fine-scale phase-space structure.
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All authors James Juno, Grant Johnson, Alexander Philippov, Ammar Hakim, Alexander Chernoglazov, Shuzhe Zeng
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Schwarzian Theory and Cosmological Constant Problem
Jun Nian
Observational data in cosmology indicate a small, positive, and nonvanishing cosmological constant that dominates the energy budget of the present universe. The origin of the cosmological constant from a
quantum perspective remains unresolved, with a discrepancy of approximately 120 orders of magnitude between its observed value and theoretical estimates. Motivated by earlier work of Gibbons, we analyze the cosmological constant problem within a
quantum-gravitational framework based on Schwarzian theory and its ensemble averaging. We then derive the phenomenological value of the dark energy density and obtain the corresponding equation of state. In this model, the cosmological constant arises from the ensemble average of time-reparametrization modes.
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Solar and Stellar Astrophysics
Lithium as a probe of stellar and galactic physics
C.Charbonnel and N.Prantzos
Lithium plays a unique role in astrophysics, as it is a powerful diagnostic for the physics and
evolution of low-mass
stars,
Galactic archaeology, and cosmology. We review the Li observations in
stars at different phases of their
evolution, the strengths and the limitations of the current theoretical
stellar models to explain the Li abundance data, our understanding of the Li sources and of the
evolution of Li through- out the
Galactic history. Key takeaways from the current state of the research in the field are: 1)
Stellar evolution models accounting for fundamental transport processes of chemical species and angular momentum hold the promise of providing a common
stellar Li depletion explanation to the Li abundance patterns observed in all
Galactic stellar populations, including the dip and the plateau(s). 2) Novae are most probably the main source of Li in the
Galaxy, on observational (but not yet theoretically established) grounds. 3) Radial migration of
stars in the
Galactic disk holds the key to understand many aspects of the Li
evolution in the Milky Way.
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Earth and Planetary Astrophysics
Terrestrial Analogs to Titan for Geophysical Research
Conor A. Nixon, Samuel Birch, Audrey Chatain et al. (+19 more)
Saturn's moon Titan exhibits remarkable parallels to the Earth in many geophysical and geological processes not found elsewhere in the
solar system at the present day. These include a nitrogen atmosphere with a condensible gas - methane - replacing the Earth's water, leading to an active meteorology with rainfall and surface manifestations including rivers, lakes and seas, and the dissolution of karstic terrain. Other phenomena such as craters, dunes, and tectonic features are found elsewhere - e.g. on Mars and Venus - but their continuing alteration by pluvial, fluvial and lacustrine processes can be studied only on Earth and Titan. Meanwhile Titan also hosts an interior
liquid water ocean with similarities to the Earth as well as to ocean worlds such as Europa and Enceladus. Our focus in this review paper is twofold: to describe the geophysical and geological parallels between Earth and Titan, and to evaluate the yet-underexploited possibilities for field analog research to gain new knowledge about these processes. To date, Titan's much colder temperature and different atmospheric and crustal materials have led to a skepticism that useful analogs can be found on Earth. Our conclusion, however, is that a much larger range of useful analog field work is possible and this work will substantially enhance our knowledge of both worlds. Such investigation will supplement the existing sparse data for Titan returned by space missions, will greatly enhance our understanding of such
datasets, and will help to provide science impetus and goals for future missions.
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All authors Conor A. Nixon, Samuel Birch, Audrey Chatain, Charles Cockell, Kendra K. Farnsworth, Peter M. Higgins, Stéphane Le Mouélic, Rosaly M.C. Lopes, Michael J. Malaska, Mohit Melwani Daswani, Kelly E. Miller, Catherine D. Neish, Olaf G. Podlaha, Jani Radebaugh, Lauren R. Schurmeier, Ashley Schoenfeld, Krista M. Soderlund, Anezina Solomonidou, Christophe Sotin, Nicholas A. Teanby, Tetsuya Tokano, Steven D. Vance
Instrumentation and Methods for Astrophysics · Cross-listed from nlin.CD
Design of low-energy transfers in cislunar space using sequences of lobe dynamics
Naoki Hiraiwa, Mai Bando, Yuzuru Sato et al. (+1 more)
Dynamical structures in the circular restricted three-body problem (CR3BP) are fundamental for designing low-energy transfers, as they aid in analyzing phase space transport and designing desirable trajectories. One of these dynamical structures, lobe dynamics, can be exploited to achieve local chaotic transport around celestial bodies. This study proposes and fully validates a systematic method for designing low-energy transfers by combining multiple sequences of lobe dynamics, building upon the authors' prior preliminary framework. A graph-based framework is developed to explore possible transfer paths between departure and arrival orbits, reducing the complexity of the combinatorial optimization problem for fuel-efficient transfer design. Using this graph, low-energy transfer trajectories are constructed by connecting chaotic orbits within lobes. The resulting optimal trajectory in the Earth–Moon CR3BP is then converted into an optimal transfer in the bicircular restricted four-body problem via multiple shooting. This transfer is compared with existing optimal solutions to demonstrate the effectiveness of the proposed method.
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All authors Naoki Hiraiwa, Mai Bando, Yuzuru Sato, Shinji Hokamoto
Earth and Planetary Astrophysics
Delivery of complex organic molecules to the system of Jupiter
T. Benest Couzinou, A. Amsler Moulanier and O. Mousis
Complex organic molecules are key markers of molecular diversity, and their formation conditions in protoplanetary disks remain an active area of research. These molecules have been detected on a variety of celestial bodies, including icy moons, and may play a crucial role in shaping the current composition of the Galilean moons. Experimental studies suggest that their formation could result from UV irradiation or thermal processing of NH3:CO2 ices. In this context, we investigate the formation of complex organic molecules in the protosolar nebula and their subsequent transport to the Jupiter system region. Lagrangian transport and irradiation simulations of 500 individual particles are performed using a two-dimensional disk
evolution model. Based on experiments with UV irradiation and thermal processing of CO2:NH3 ice, this model allows us to estimate the estimate the potential for the formation of complex organic molecules through these processes. Almost none of the particles released at a local temperature of 20 K (corresponding to ~12 AU from the Sun) reach the location of the system of Jupiter. However, when released at a local temperature of 80 K (~7 AU), approximately 45% of the centimetric particles and 30% of the micrometric particles can form complex organic molecules via thermal processing, subsequently reaching the location of the system of Jupiter within 300 kyr. Assuming that the Galilean moons formed in a cold circumplanetary disk around Jupiter, the nitrogen-bearing species potentially present in their interiors could have originated from the formation of complex organic molecules in the protosolar nebula.
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Instrumentation and Methods for Astrophysics · Cross-listed from stat.CO
Nested Sampling with Slice-within-Gibbs: Efficient Evidence Calculation for Hierarchical Bayesian Models
David Yallup
We present Nested Sampling with Slice-within-Gibbs (NS-SwiG), an
algorithm for
Bayesian inference and evidence estimation in high-dimensional models whose likelihood admits a factorization, such as hierarchical
Bayesian models. We construct a procedure to sample from the likelihood-constrained prior using a Slice-within-Gibbs kernel: an outer update of hyperparameters followed by inner block updates over local parameters. A likelihood-budget decomposition caches per-block contributions so that each local update checks feasibility in constant time rather than recomputing the global constraint at linearly growing cost. This reduces the per-replacement cost from quadratic to linear in the number of groups, and the overall algorithmic complexity from cubic to quadratic under standard assumptions. The decomposition extends naturally beyond independent observations, and we demonstrate this on Markov-structured latent variables. We evaluate NS-SwiG on challenging
benchmarks, demonstrating scalability to thousands of dimensions and accurate evidence estimates even on posterior geometries where state-of-the-art gradient-based samplers can struggle.
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Earth and Planetary Astrophysics
Analytical modeling of helium absorption signals of isothermal atmospheric escape
Hiroto Mitani and Rolf Kuiper
Atmospheric escape driven by extreme ultraviolet (EUV) radiation is a critical process shaping the
evolution of close-in
exoplanets. Recent observations have detected helium triplet absorption in numerous (>20) close-in
exoplanets, highlighting the importance of understanding upper atmospheric thermo-chemical structure. While super-
solar metallicity has been observed in the atmospheres of some close-in
exoplanets, the impact of metal species on both atmospheric escape dynamics and observed absorption features remains poorly understood. In this study, we derive a simplified yet accurate formula for the equivalent width of helium absorption in the limit of an isothermal temperature for the upper atmosphere. Our results demonstrate that
planets with lower temperature (metal-rich atmosphere) exhibit lower mass-loss rate although the equivalent width of helium triplet absorption remains largely independent of atmospheric temperature (
metallicity) because the low temperatures in these atmospheres enhance the fraction of helium in its triplet state. Additionally, we present a hydrodynamic model based on radiation-hydrodynamics simulations that incorporates the effects of metal cooling. Our analytical model can predict the helium triplet equivalent width of the atmosphere of simulations. The analytical model provides a comprehensive framework for understanding how metal cooling in the upper atmosphere influences the thermo-chemical structure and observable helium features of close-in exoplanetary atmospheres, offering valuable insights for interpreting current and future observational data.
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Astrophysics of Galaxies
Dynamical Modelling of Galactic Kinematics using Neural Networks
David A. Simon, Michele Cappellari, Shude Mao et al. (+2 more)
The advent of integral field data has revolutionised the study of
galaxy evolution. A key component of this is dynamical modelling methods which have allowed for crucial insights to be made from kinematic data. Despite this importance, most dynamical models make a number of key assumptions which do not hold for real
galaxies. These include assumptions about the geometry (axisymmetry or triaxiality), the shape of the velocity ellipsoid, and the shape of the underlying
stellar distribution. At the same time, machine learning methods are becoming increasingly powerful, with many applications appearing in astronomy. As a first step towards building new dynamical modelling methods with machine learning, it is important to understand the types of machine learning architectures that are best fit for dynamical modelling. To investigate this, we construct a training set of dynamical models of early-type
galaxies using Jeans Anisotropic Modelling (JAM). We then train a neural network on this data using the parameters of JAM and mock photometry as the input. We are able to accurately model JAM
galaxies with relatively simple machine learning architectures, leading to a significant speed increase over traditional JAM modelling.
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All authors David A. Simon, Michele Cappellari, Shude Mao, Jiani Chu, Dandan Xu
Earth and Planetary Astrophysics
A Collective Trigger for Widespread Planetesimal Formation Revealed by Accretion Ages
James Bryson, Hannah Sanderson, Francis Nimmo et al. (+4 more)
The formation of planetesimals was an integral part of the cascading series of processes that built the terrestrial
planets. To illuminate planetesimal formation, here we develop a refined thermal
evolution model to calculate the formation ages of meteorite parent planetesimals. This model includes chemical reactions and phase changes during heating, as well as natural variations in the proportions of the constituent phases of these planetesimals. We find that the parent bodies of non-carbonaceous (NC) and carbonaceous (CC) iron meteorites start forming at very similar times (~0.95 Myr after calcium-aluminium-rich inclusion [CAI] formation) and occupy overlapping time windows. NC and CC chondrite parent bodies formed later during non-overlapping periods. We combine these ages with proportions of isotopic end-members we recover from mixing models to construct records of motion throughout the protoplanetary disk. These records argue that NC and CC material traversed the barrier in the disk after ~0.95 Myr after CAI formation. The onset of this motion coincided with planetesimal formation, indicating that the phenomenon that drove motion also triggered planetesimal formation. We argue that this feature also served as the semi-permeable barrier in the disk. Although its identity is uncertain, the effects this phenomenon had on the timing of planetesimal formation and motion through the disk can now serve as constraints on models of disk
evolution. Models that reproduce these effects would elucidate the nature and implications of this phenomenon, which is key to unlocking a holistic model of terrestrial
planet building.
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All authors James Bryson, Hannah Sanderson, Francis Nimmo, Sanjana Sridhar, Gregory Brennecka, Yves Marrocchi, Jason Terry
Earth and Planetary Astrophysics · Cross-listed from physics.app-ph
g4chargeit: Geant4-based kinetic Monte Carlo simulations of charging in dielectric materials
Kush P. Gandhi, Advik D. Vira, William M. Farrell et al. (+5 more)
We present g4chargeit, a kinetic Monte Carlo framework built on Geant4 for self-consistent simulation of time-dependent electrostatic charging in dielectric materials. The model explicitly incorporates
stochastic particle transport and scattering processes using validated Geant4 cross-sections, while self-consistently evolving the electric potential and field. As a representative application, we simulate the charging of regolith grains under average dayside conditions on the Moon. The surface of the Moon, in addition to other airless planetary bodies, are regularly exposed to
solar ultraviolet
photons and
solar-wind
plasma, creating a radiation environment in which electrostatic interactions among regolith grains become significant. Until now, simulations of regolith charging have often relied on analytical approximations that oversimplify grain geometry and interaction mechanisms. Our Geant4-based simulations reveal charge accumulation within intergrain micro-cavities, leading to repulsive electrostatic forces consistent with experimental observations. The framework establishes a multiscale approach that links microscopic scattering events to the continuity equation of surface charge density and to the formation of macroscopic surface charge patches in complex grain geometries. Although demonstrated here for planetary regolith, the method is general and applicable to a broad range of dielectric charging problems. The code is openly available at https://github.com/kgandhi63/g4chargeit.git.
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All authors Kush P. Gandhi, Advik D. Vira, William M. Farrell, Nikolai Simonov, Alvaro Romero-Calvo, Thomas M. Orlando, Phillip N. First, Zhigang Jiang
Astrophysics of Galaxies
MIDIS: The identification of deep MIRI-red sources as candidates for extreme Balmer-break and line emitting galaxies at high-z
I. Jermann, G. Brammer, S. Gillman et al. (+27 more)
We investigate the detection and nature of 5.6~\mu m MIRI-red sources in the MIRI Deep Imaging Survey (MIDIS), covering 2.4~arcmin$^2$ in the Hubble Ultra Deep Field. MIDIS is the deepest JWST/MIRI survey to date, probing faint limits and enabling studies of rare high-
redshift galaxy populations. We define MIRI-red sources as those detected at 5$\sigma$ significance in MIRI/F560W with red colors: $m_{\rm F444W} - m_{\rm F560W} \ge 0.5$. Using an empirical methodology, we estimate the purity and completeness of MIRI detections and find that a 5-sigma detection at 28.75 mag has a purity of 92% and completeness of 54%. We identify seven MIRI-red
galaxy candidates, including an F115W dropout consistent with a high-
redshift galaxy candidate. We explore possible physical origins for the MIRI-red population, including active
galactic nuclei,
dust-obscured
galaxies, extreme emission-line
galaxies, evolved
stellar populations, and Little Red Dots (LRDs). Given the proximity of the F444W and F560W filters and the depth of MIDIS, MIRI-red
galaxies are consistent with emission-line
galaxies with $EW_0(H\alpha) \ge 750$ Å\ or $EW_0(H\beta + [OIII]) \ge 600$ Å, or high-
redshift Balmer breaks of at least 1.6. We also discuss an extreme MIRI-red
galaxy undetected in F444W, a potential MIRI-only source, for which we derive $EW_0(H\alpha) \sim 6000$ Å\ and $EW_0(H\beta + [OIII]) \sim 4000$ Å, or high-$z$ LRD analogs with Balmer breaks of 6.3. Finally, we find fewer MIRI-red detections than expected from extrapolations of the H$\alpha$ or H$\beta$+[OIII] line luminosity functions, consistent with previous deep searches, while the absence of $z>10$ LRD candidates agrees with theoretical expectations for the MIDIS volume.
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All authors I. Jermann, G. Brammer, S. Gillman, T. R. Greve, L. A. Boogaard, J. Melinder, R. A. Meyer, P. G. Pérez-González, P. Rinaldi, J. L. Colina, G. Östlin, G. Wright, J. Álvarez-Márquez, A. Bik, K. I. Caputi, A. Crespo Gómez, L. Costantin, J. Hjorth, E. Iani, S. Kendrew, A. Labiano, D. Langeroodi, F. Peissker, C. Prieto-Jiménez, J. P. Pye, T. V. Tikkanen, F. Walter, P. van der Werf, T. Henning, M. Shuntov
Cosmology and Nongalactic Astrophysics
The Epoch of Reionization 21 cm Bispectrum at $z=8.2$ from MWA data II: Smooth Component Filtering
Sukhdeep Singh Gill, Khandakar Md Asif Elahi, Somnath Bharadwaj et al. (+2 more)
The 21 cm bispectrum (BS) offers a powerful probe of the Epoch of Reionization (EoR), but its observational access is severely hindered by dominant astrophysical foregrounds. Considering Murchison Widefield Array (MWA) observations at $154.2~\mathrm{MHz}$ ($z=8.2$), we mitigate the foregrounds with Smooth Component Filtering (SCF) and estimate the 21 cm BS. We validate the pipeline using a simulated 21 cm signal and show that the input BS is recovered for modes $k_{\parallel} \ge [k_\parallel]_f=0.135~{\rm Mpc}^{-1}$. Applied to actual data, the SCF produces substantial foreground suppression, reducing the amplitude of the cylindrical BS $B(k_{1\perp},k_{2\perp},k_{3\perp},k_{1\parallel},k_{2\parallel})$ by $3-4$ orders of magnitude. The artifacts due to the missing frequency channels in the data are also suppressed. The resulting EoR window is significantly cleaner at small $k_{\perp}$. We adopt the region $(k_{1 \perp},k_{2 \perp},k_{3 \perp})\leq 0.026~{\rm Mpc}^{-1}$ and $(k_{1\parallel},k_{2\parallel},k_{3\parallel})>0.135~{\rm Mpc}^{-1}$ to evaluate the 3D spherical BS and constrain the EoR signal. By combining estimates over all triangle shapes, we place the lower and upper limits on the mean cube brightness temperature fluctuations $\Delta^3$. The estimates are consistent with statistical fluctuations from system noise. The most stringent lower limit $\Delta^3_{\rm LL}=-(1.25\times 10^4)^3~{\rm mK}^3$ and upper limit $\Delta^3_{\rm UL}=(1.22\times 10^4)^3~{\rm mK}^3$ are obtained at $k_1=0.281~{\rm Mpc}^{-1}$. Additional observing time will reduce the noise level and enable substantially tighter constraints on the EoR signal.
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All authors Sukhdeep Singh Gill, Khandakar Md Asif Elahi, Somnath Bharadwaj, Shiv K. Sethi, Akash Kumar Patwa
High Energy Astrophysical Phenomena
WFST Supernovae in the First Year: III. Systematical Study of the Photometric Behavior of Early-phase Core-collapse Supernovae
Junhan Zhao, Ji-an Jiang, Zelin Xu et al. (+22 more)
We investigate the multiband photometric properties of seven
supernovae (SNe) showing double-peaked light-curve
evolution and prominent shock-cooling emission, observed by the Wide Field Survey
Telescope (WFST) during its first year of operation. By jointly employing an analytic early shock-cooling model and the Arnett radioactive-
diffusion model, we fit the bolometric light curves and infer ejecta masses in the range $1.1$-$2.6 M_\odot$, consistent with a transitional population between ultra-stripped
supernovae (USSNe) and normal stripped-envelope
supernovae (SESNe). The envelope masses are estimated to be $M_{\rm env}=0.1$-$0.4 M_\odot$, while the progenitors are constrained to be yellow or blue supergiants (YSGs/BSGs) with radii of $R=120$-$300 R_\odot$. Using empirical relations, we estimate progenitor luminosities of $L=10^{4.6}$-$10^{4.9} L_\odot$, corresponding to zero-age main-sequence (ZAMS) masses of $8$-$20 M_\odot$. Theoretical models suggest that such progenitors are more naturally produced through binary
evolution channels, as single-
star evolutionary pathways are unable to yield ejecta masses this low.
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All authors Junhan Zhao, Ji-an Jiang, Zelin Xu, Yu-Hao Zhang, Qiliang Fang, Liang-Duan Liu, Qingfeng Zhu, Yun-Wei Yu, Keiichi Maeda, Lluís Galbany, Hanindyo Kuncarayakti, Željko Ivezić, Saurabh W. Jha, Peter Yoachim, Dezheng Meng, Weiyu Wu, Zhengyan Liu, Andrew J. Connolly, Ziqing Jia, Wen Zhao, Lulu Fan, Ming Liang, Hairen Wang, Jian Wang, Hongfei Zhang
High Energy Astrophysical Phenomena
WFST Supernovae in the First Year: II. SN 2024aedt: Systematical Study of a Transitional Type Ia Supernova
Dezheng Meng, Ji-an Jiang, Xu Kong et al. (+26 more)
We present comprehensive photometric and spectroscopic observations of a transitional type Ia SN 2024aedt, discovered by the 2.5-meter Wide Field Survey
Telescope (WFST) within one day of the explosion. Its light curve is characterized by a peak absolute magnitude of $M_B = -18.49 \pm 0.03$ mag and a decline rate of $\Delta m_{15}(B) = 1.53 \pm 0.36$ mag, placing the object on the $\Delta m_{15}(B)$–$M_B$ diagram in the transition region between normal and subluminous SNe Ia. Furthermore, the early-color
evolution and host
galaxy environment of SN 2024aedt underscore its transitional nature, sharing properties with both normal and 91bg-like SNe Ia. Light-curve modeling with MOSFiT yields a synthesized $^{56}\mathrm{Ni}$ mass of $0.414 \pm 0.042\,M_{\odot}$ and a total ejecta mass of $0.548 \pm 0.108\,M_{\odot}$. A comparison with theoretical models suggests that the evolutionary trend can be broadly explained by both delayed-detonation (DDT) and double-detonation (DDet) scenarios while possible early-excess emissions predicted by DDet cannot be identified given the limited detections soon after the SN explosion. Although the overall spectral
evolution of SN 2024aedt is similar to that of other transitional SNe Ia, the spectroscopic comparison reveals diversity in the early-phase blue-end features, which becomes more homogeneous at later phases. The result indicates the importance of early-time observations in understanding the origin of SN Ia diversity.
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All authors Dezheng Meng, Ji-an Jiang, Xu Kong, Zelin Xu, Keiichi Maeda, Hanindyo Kuncarayakti, Lluís Galbany, Saurabh W. Jha, Željko Ivezić, Peter Yoachim, Weiyu Wu, Zhengyan Liu, Junhan Zhao, Andrew J. Connolly, Ziqing Jia, Lei Hu, Weiyu Ding, Lulu Fan, Feng Li, Ming Liang, Jinlong Tang, Zhen Wan, Hairen Wang, Jian Wang, Yongquan Xue, Hongfei Zhang, Wen Zhao, Xianzhong Zheng, Qingfeng Zhu
High Energy Astrophysical Phenomena
WFST Supernovae in the First Year: I. Statistical Study of 16 Early-phase Type Ia Supernovae from the Pilot Survey
Weiyu Wu, Ji-an Jiang, Zelin Xu et al. (+27 more)
In this paper we present 16 early-phase type Ia
supernovae (SNe Ia) discovered during the pilot survey of the 2.5-meter Wide Field Survey
Telescope (WFST-PS) from March 4 to July 10, 2024, including three SNe Ia with early-excess emission features (EExSNe Ia). The discovery magnitude of the 16 WFST-PS early-phase SNe is at least 3 mag fainter than their peak brightness. A large scatter of color indices is found in approximately the first 10 days of
supernova explosions, indicating diverse photometric behaviors in the early phase. Three EExSNe Ia show relatively brighter peak luminosities and longer rise time compared to those of non-EExSNe Ia. The results indicate that current theoretical models require further refinement to fully capture the early photometric
evolution of SNe Ia. Based on the initial high-cadence ugr-band data from the WFST-PS survey, we emphasize that early near-ultraviolet (NUV) observations are indispensable for placing tight constraints on the explosion mechanisms and progenitor systems of SNe Ia.
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All authors Weiyu Wu, Ji-an Jiang, Zelin Xu, Dezheng Meng, Keiichi Maeda, Hanindyo Kuncarayakti, Lluís Galbany, Saurabh W. Jha, Željko Ivezić, Peter Yoachim, Zhengyan Liu, Junhan Zhao, Tinggui Wang, Xu Kong, Andrew J. Connolly, Ziqing Jia, Lei Hu, Lulu Fan, Ning Jiang, Feng Li, Ming Liang, Jinlong Tang, Zhen Wan, Hairen Wang, Jian Wang, Yongquan Xue, Hongfei Zhang, Wen Zhao, Xianzhong Zheng, Qingfeng Zhu
High Energy Astrophysical Phenomena
Illuminating the Mass Gap Through Deep Optical Constraint on a Neutron Star Merger Candidate S250206dm
Zhengyan Liu, Zelin Xu, Ji-an Jiang et al. (+35 more)
The gravitational wave (GW) event S250206dm, as the first well-localized
neutron star merger candidate potentially located in the mass gap, presented a unique opportunity to probe the electromagnetic signatures from such a system. Here we report a deep, multiband search with the new 2.5-meter Wide Field Survey
Telescope (WFST), covering about 64% of the localization region up to a 5-sigma limiting magnitude of 23 mag. In total, 12 potential candidates have been identified while none of them are likely related to S250206dm. This non-detection provides the most stringent constraint to date on any associated kilonova. Crucially, an AT 2017gfo-like event at 269 Mpc can be excluded by WFST observations alone. Based on ejecta mass limits, a
neutron star-black hole with a large mass ratio (Q >= 3.2) is disfavored. This optical-derived constraint on the mass ratio reaches, for the first time, a precision comparable to that inferred from the GW signal. This work presents the best observation of this type of events until now, and demonstrates the power of rapid, deep follow-up observations to constrain the properties of compact binary progenitors, offering key insights into the constituents of the mass gap.
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All authors Zhengyan Liu, Zelin Xu, Ji-an Jiang, Wen Zhao, Zhiping Jin, Zigao Dai, Dezheng Meng, Xuefeng Wu, Daming Wei, Runduo Liang, Lei He, Minxuan Cai, Lulu Fan, Weiyu Wu, Junhan Zhao, Ziqing Jia, Kexin Yu, Jinjun Geng, Di Xiao, Feng Li, Jinlong Tang, Yingxi Zuo, Xiaoling Zhang, Hao Liu, Jian Wang, Hongfei Zhang, Ming Liang, Hairen Wang, Dazhi Yao, Lei Hu, Xu Kong, Bin Li, Ning Jiang, Tinggui Wang, Zhen Wan, Yongquan Xue, Qingfeng Zhu, Xianzhong Zheng
Instrumentation and Methods for Astrophysics
Deeper detection limits in astronomical imaging using self-supervised spatiotemporal denoising
Yuduo Guo, Hao Zhang, Mingyu Li et al. (+10 more)
The detection limit of astronomical imaging observations is limited by several noise sources. Some of that noise is correlated between neighbouring image pixels and exposures, so in principle could be learned and corrected. We present an astronomical self-supervised
transformer-based denoising
algorithm (ASTERIS), that integrates spatiotemporal information across multiple exposures. Benchmarking on mock data indicates that ASTERIS improves detection limits by 1.0 magnitude at 90% completeness and purity, while preserving the point spread function and photometric accuracy. Observational validation using data from the James Webb Space
Telescope (JWST) and Subaru
telescope identifies previously undetectable features, including low-surface-brightness
galaxy structures and gravitationally-lensed arcs. Applied to deep JWST images, ASTERIS identifies three times more
redshift > 9
galaxy candidates, with rest-frame ultraviolet luminosity 1.0 magnitude fainter, than previous methods.
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All authors Yuduo Guo, Hao Zhang, Mingyu Li, Fujiang Yu, Yunjing Wu, Yuhan Hao, Song Huang, Yongming Liang, Xiaojing Lin, Xinyang Li, Jiamin Wu, Zheng Cai, Qionghai Dai
Instrumentation and Methods for Astrophysics
Kolmogorov analysis of pulsar TOA
N. Galikyan, A.A. Kocharyan and V.G. Gurzadyan
The Kolmogorov stochasticity parameter (KSP) as a sensitive descriptor of the degree of randomness of signals was used to analyze the properties of the NANOGrav
pulsar timing data associated with a
stochastic gravitational wave background. The time of arrival (TOA) data of white noise for 68
pulsars were analyzed regarding their KSP properties. The analysis enabled us to obtain the degree of randomness of the white noise for various
pulsars and to reveal its inhomogeneity, i.e.,
pulsars with low and high randomness of the white noise. The time dependence of the randomness in the white noise was also studied, indicating the existence of nonstationary physical processes influencing the
pulsar timing. The KSP is thus acting as an indicator for the degree of the agreement between the observations and the timing models and as a test in revealing the contribution of various physical processes in the
stochastic background signal.
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Astrophysics of Galaxies
PRODIGE - envelope to disk with NOEMA: VII. (Complex) organic molecules in the NGC1333 IRAS4B1 outflow: A new laboratory for shock chemistry
Laura A. Busch, J. E. Pineda, P. Caselli et al. (+20 more)
Shock chemistry is an excellent tool to shed light on the formation and destruction mechanisms of complex organic molecules (COMs). The L1157-mm
outflow is the only low-mass protostellar
outflow that has extensively been studied in this regard. Using the data taken as part of the PRODIGE (PROtostars & DIsks: Global
Evolution) large program, we aim to map COM emission and derive the molecular composition of the protostellar
outflow driven by the Class 0 protostar NGC1333 IRAS4B1 to introduce it as a new laboratory to study the impact of shocks on COM chemistry. In addition to typical
outflow tracers such as SiO and CO,
outflow emission is seen from H2CO, HNCO, and HC3N, as well as from the COMs CH3OH, CH3CN, and CH3CHO, and even from deuterated species such as DCN, D2CO, and CH2DOH. Maps of integrated intensity ratios between CH3OH and DCN, D2CO, and CH3CHO reveal gradients with distance from the protostar. Intensity ratio maps of HC3N and CH3CN with respect to CH3OH peak in the southern lobe where temperatures are highest. Rotational temperatures derived towards two positions, one in each lobe, are found in the range ~50-100 K. Abundances with respect to CH3OH are higher by factors of a few than for the L1157-B1. In conclusion, for the first time, we securely detected the COMs CH3CN, CH3CHO, and CH2DOH in the IRAS 4B1
outflow, serendipitously with limited sensitivity and bandwidth. Targeted observations will enable the discovery of new COMs and a more detailed analysis of their emission. Morphological differences between molecules in the IRAS 4B1
outflow lobes and their relative abundances provide first proof that this
outflow is a promising new laboratory for shock chemistry, which will offer crucial information on COM formation and destruction as well as
outflow structure and kinematics.
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All authors Laura A. Busch, J. E. Pineda, P. Caselli, D. M. Segura-Cox, S. Narayanan, C. Gieser, M. J. Maureira, T.-H. Hsieh, Y. Lin, M. T. Valdivia-Mena, L. Bouscasse, Th. Henning, D. Semenov, A. Fuente, Y.-R. Chou, L. Mason, P. C. Cortés, L. W. Looney, I. W. Stephens, M. Tafalla, A. Dutrey, W. Kwon, P. Saha
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Extreme-mass ratio inspirals in Schwarzschild - de Sitter spacetime I: Weak-field orbits
John Adrian N. Villanueva and Ian Vega
The inspiral of a compact object into a black hole is a key source of low - frequency gravitational waves for future space-based detectors like LISA. While models of this process have advanced considerably, they typically focus on asymptotically flat spacetimes. In this paper, we investigate how departures from asymptotic flatness, whether driven by
cosmic expansion or large-scale
galactic environments, alter adiabatic orbital
evolution. Using the Schwarzschild - de Sitter (SdS) metric, we parametrize these deviations via an `SdS parameter' ($\lambda$) and analyze its impact on bound orbits. We calculate how $\lambda$ shifts the separatrix between bound and plunging states and modifies the relationship between a binary's energy, angular momentum, and orbital geometry. By applying a modified quadrupole formula in the weak-field limit, we investigate the effect of $\lambda$ on circularization, plunge times, and orbital trajectories. We show that a positive SdS parameter accelerates eccentricity decay and shortens inspiral timescales. We also generate adiabatic waveforms from inspirals evolving under radiation reaction, exhibiting an increase in amplitude and a cumulative phase advance induced by $\lambda$. While these effects are negligible if $\lambda$ is strictly cosmological, they become observationally relevant if the parameter serves as a proxy for astrophysical environments that induce $\sim r^2$ potential corrections. Our results suggest that such environmental coupling could meaningfully bias event rate estimates and waveform templates for space-based gravitational-wave astronomy.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.CV
ComptonUNet: A Deep Learning Model for GRB Localization with Compton Cameras under Noisy and Low-Statistic Conditions
Shogo Sato, Kazuo Tanaka, Shojun Ogasawara et al. (+4 more)
Gamma-ray bursts (GRBs) are among the most energetic transient phenomena in the universe and serve as powerful probes for high-energy astrophysical processes. In particular, faint GRBs originating from a distant universe may provide unique insights into the early stages of
star formation. However, detecting and localizing such weak sources remains challenging owing to low
photon statistics and substantial background noise. Although recent machine learning models address individual aspects of these challenges, they often struggle to balance the trade-off between statistical robustness and noise suppression. Consequently, we propose ComptonUNet, a hybrid deep learning framework that jointly processes raw data and reconstructs images for robust GRB localization. ComptonUNet was designed to operate effectively under conditions of limited
photon statistics and strong background contamination by combining the statistical efficiency of direct reconstruction models with the denoising capabilities of image-based architectures. We perform realistic simulations of GRB-like events embedded in background environments representative of low-Earth orbit missions to evaluate the performance of ComptonUNet. Our results demonstrate that ComptonUNet significantly outperforms existing approaches, achieving improved localization accuracy across a wide range of low-statistic and high-background scenarios.
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All authors Shogo Sato, Kazuo Tanaka, Shojun Ogasawara, Kazuki Yamamoto, Kazuhiko Murasaki, Ryuichi Tanida, Jun Kataoka
Astrophysics of Galaxies
Under Pressure: UV Emission Line Ratios as Barometers of AGN Feedback Mechanisms
Elise Fuller, Sean D. Johnson, Jonathan Stern et al. (+16 more)
Feedback from active
galactic nuclei (AGN) is widely acknowledged to regulate the growth of massive
galaxies, though its driving mechanisms are debated. Prevailing theories suggest that AGN-driven
outflows are driven either by radiation pressure acting directly on the dusty interstellar medium (ISM) or by hot winds entraining cooler ISM gas, but the relative contribution of each mechanism remains uncertain. By combining optical emission line measurements with highly ionized UV emission lines, it is possible to constrain whether the pressure source applied to ionized clouds is primarily radiation or primarily hydrodynamic, and thus constrain the dominant driver. This study presents the first multi-object analysis of far-ultraviolet (FUV) spectra from
galactic-scale AGN-driven
outflows in obscured
quasars, based on
Cosmic Origins Spectrograph observations of five low-
redshift targets. By comparing narrow-line region UV emission line ratios to theoretical models that vary the importance of the two pressure sources, we find three out of five targets fall within the radiation pressure-dominated regime. A fourth target exhibits intermediate emission-line ratios that suggest radiation pressure and pressure from a hot wind are both dynamically important. Finally, the lowest-luminosity object in our sample may have a dynamically important hot wind component, but non-detections prevent a clear conclusion in this case. These results suggest radiation pressure dominates circum-
nuclear narrow-line region cloud dynamics, but pressure from a hot wind also plays a role in some cases. This is consistent with AGN feedback scenarios mediated by radiation pressure or a short-lived hot wind phase that dissipates after initially accelerating
outflows.
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All authors Elise Fuller, Sean D. Johnson, Jonathan Stern, Hsiao-Wen Chen, Ena Choi, Claude-André Faucher-Giguère, Massimo Gaspari, Andy Goulding, Jenny Greene, Timothy M. Heckman, Jennifer I-Hsiu Li, Zhuoqi Liu, Nishant Mishra, Kristina Nyland, Kate Rowlands, Gwen C. Rudie, Evan Schneider, Dominika Wylezalek, Nadia L. Zakamska
Earth and Planetary Astrophysics
Kuiper Belt Formation via Grainy Planetary Migration
Patryk Sofia Lykawka, Jonathan Horner and Pedro Bernardinelli
We used N-body simulations to model the 4.5 Gyr orbital
evolution of the early Kuiper Belt, incorporating a massive protoplanetary disk, the four
giant planets, and 1500
primordial Pluto-class bodies ("Plutos") that drove Neptune's grainy migration. The analysis of 67 simulated systems revealed key insights: (1) All systems featured the primary trans-Neptunian object (TNO) populations: cold/hot classical, resonant, scattered, and detached; (2) Captures into stable resonant orbits favored close Neptunian mean motion resonances (MMRs; e.g., 3:2, 2:1), while distant ones beyond 50 au (e.g., 5:2 MMR) were underpopulated; (3) Optimal matches to observed resonant fractions and the classical region (including the kernel) arose from models considering a jumping Neptune, self-gravitating Plutos, and an initial disk edge at 45-47 au; (4) Models including
primordial scattered disks boosted distant MMR captures but overproduced scattered objects; (5) All models were inefficient at producing the detached (q > 40 au) and high-i (i > 45 deg) populations and failed to populate observed niches, such as distant detached (a > 245 au), low-i detached (i < 20 deg), low-i scattered with q = 37-40 au (i < 20 deg), and extreme (q > 50 au or i > 50 deg) TNOs; (6) Grainy migration effects peaked early, fading as the Plutos were removed; (7) With a few
primordial Plutos surviving inside 50 au, the initial population was estimated at ~150-500 to explain Pluto's solitary status. Although our four-
giant-
planet models reasonably replicate the trans-Neptunian structure within 50 au, they fail to account for detached, high-i, and extreme TNOs. Additional processes (e.g., a distant undiscovered
planet) are required for a comprehensive outer
solar system framework.
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Astrophysics of Galaxies
Varstrometry for Off-nucleus and Dual Subkiloparsec AGN (VODKA): Three Quadruply Lensed Quasars at Cosmic Noon in HST and JWST
Mingrui Liu, Yu-Ching Chen, Nadia L. Zakamska et al. (+7 more)
We present results from imaging observations of three quadruply lensed
quasars by Hubble Space
Telescope (HST) and James Webb Space
Telescope (JWST) at
redshifts $z = 2.550$, 2.975, and 1.500. We model our targets assuming a singular isothermal ellipsoid mass profile and an elliptical SÃo̧pyright}rsic profile for the
lensing galaxies, and reconstruct the
geometric configuration of each system with measured Einstein radii of 0.44$'$, 0.58$'$, and 0.49$'$. While no spectroscopic measurements are available for the lenses, we constrain the
redshift of each lens to $0.5 < z < 1.2$, $1.0 < z < 1.5$, and $0.4 < z < 0.9$. For all three lenses, the best-fit light model yield a typical de Vaucouleurs $n_{\rm S\acute{e}rsic} \sim 4$ profile and an effective radius $R_e$ around $\sim 1.5 - 3.5$ kpc. We accordingly classify the three lenses as early-type
galaxies at an intermediate to high
redshift, a common type for strong
lensing galaxies. Compared to other known quadruple lenses, the
lensing galaxies in this work are at the lower end of the distribution of Einstein radii and upper end of the distribution of the lens
redshifts. They represent an interesting quadrant of subarcsecond-separation lenses in the population of single-
galaxy strong
lensing which have been largely unexplored yet and will be great targets of interest in upcoming high-resolution
lensing surveys.
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All authors Mingrui Liu, Yu-Ching Chen, Nadia L. Zakamska, Xin Liu, Yue Shen, Xuheng Ding, Arran Gross, Hsiang-Chih Hwang, Yuzo Ishikawa, Kedar A. Phadke
Solar and Stellar Astrophysics
Multiple shocks generated by the 2024 May 14 coronal mass ejection
Mohamed Nedal, Catherine Cuddy, David M. Long et al. (+3 more)
This study characterises a series of type~II
radio bursts associated with a CME that occurred on 14 May, focusing on the coronal conditions during the event and identifying the likely location of the shocks where the
radio bursts are generated. The CME was tracked using a combination of white light and extreme ultraviolet observations of the
solar corona taken by three instruments: GOES-SUVI, two coronagraphs of the SOHO-LASCO, together with ground-based
radio observations between 10-240~MHz from I-LOFAR. The radial distances of the
radio sources were examined using a series of density models, with both PFSS and MHD models used to examine the coronal
plasma conditions. Four type~II bursts were identified in the I$-$LOFAR
radio dynamic spectrum over $\sim$15~minutes, exhibiting features such as band splitting, herringbones, and fragmentation. The shocks were found to have speeds ranging between $\sim$443$-$2075~km s$^{-1}$, with drift rates of $\sim-$361 to -78~kHz~s$^{-1}$. The shocks were found to have a $M_A \approx$ 3.21$-$3.57. indicating that they were super-Alfvénic. The first type~II burst was triggered $\sim$18~minutes after the CME launch, with each burst appearing to have been generated at a different height in the corona. Analysis of the derived kinematics and modelling results suggests that the type~II bursts were likely produced at the shoulders of the CME near the flanks, where open
magnetic field lines and relatively low Alfvén speeds facilitated shock formation. This multi-instrument study shows that multiple type II bursts from a single CME originated at different coronal heights, with modelling indicating their generation near the CME flanks, where low Alfvén speeds and open
magnetic field lines facilitated shock formation.
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All authors Mohamed Nedal, Catherine Cuddy, David M. Long, Shilpi Bhunia, Pietro Zucca, Peter T. Gallagher