Earth and Planetary Astrophysics
Machine Learning as a Transformative Tool for (Exo-)Planetary Science
J. Davoult, V. T. Bickel, C. Haslebacher et al. (+11 more)
The exploration of planetary bodies in our
Solar system and beyond relies on the processing and interpretation of large, spatio-temporally inconsistent, and heterogeneous
datasets. Recent advances in machine learning (ML) provide unprecedented opportunities to address many fundamental challenges posed by these heterogeneous and hyper-dimensional
datasets. This review chapter highlights innovative ML methodologies that were developed and used by NCCR
PlanetS members to address three overarching challenges in (exo)planetary science. The first challenge is sequence modelling, which encompasses the intricate analysis of one-dimensional data such as time series of radial velocities and light curves, among other examples. Secondly, there is pattern recognition that involves studying correlations, leveraging convolutional neural networks for feature extraction, mapping and cross correlation among other examples., anomaly detection through variational autoencoders, and unsupervised clustering of mass spectrometric data. Lastly, there are generative models and emulation-based
Bayesian analysis, which encompass the development of predictive models for planetary interior structure, employing Deep Neural Networks to understand
planet formation mechanisms. These innovative ML methodologies herald a paradigm shift in the processing of data and numerical models that represent inherent challenges in planetary and exoplanetary science, paving the way for revolutionary discoveries and ideas in this field.
Read the full abstract ▾
All authors J. Davoult, V. T. Bickel, C. Haslebacher, Y. Alibert, D. Angerhausen, C. Cantero, J. A. Egger, R. Eltschinger, Y. Eyholzer, E. O. Garvin, S. Gruchola, A. Leleu, S. Marques, Y. Zhao
Cosmology and Nongalactic Astrophysics
The Cosmic Web and Its Filaments: Neutrino Mass from Topology and Persistent Homology
Graziano Rossi, Hogyun Yu and Michaël Michaux
We apply discrete Morse theory, global
topology, and persistent homology to characterize the impact of massive
neutrinos on the multiscale
cosmic web, focusing on filaments. The
topology of the
cosmic web is sensitive to
neutrino imprints, and persistence diagrams provide more information than commonly used summary statistics by quantifying the longevity of topological features across densities. This scale-adaptive, parameter-free formalism is powerful, as massive
neutrinos affect
halos, walls, filaments, and voids in distinct ways. Within this framework, we simultaneously assess their impact on tracers and skeleton structures and capture their multiscale signals across
cosmic time. Discrete Morse theory is also well suited for particle-based
neutrino implementations, often affected by Poisson shot noise, as it preserves the salient features of the underlying smooth field. Using two independent sets of N-body simulations, we present filament statistics and persistence diagrams in massive-
neutrino cosmologies. Our results show that
neutrinos leave distinct imprints on filaments and skeleton connectivity, producing mass-dependent signatures most pronounced at high
redshift (z~2) and detectable at the few-percent level for masses as small as $M_\nu \sim 0.1$ eV. Filaments thus provide an ideal environment for isolating
neutrino effects. We also compare two implementations of massive
neutrinos to assess systematics. Our study establishes a promising avenue for leveraging
cosmic web
topology, persistent homology, and environment-based statistics to constrain or directly detect
neutrino mass and infer the mass hierarchy - a long-standing challenge in particle physics and a major objective of ongoing and upcoming
galaxy redshift surveys (e.g., DES, DESI, Euclid, Rubin-LSST).
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Bounding axion dark energy
Gary Shiu, Flavio Tonioni and Hung V. Tran
We study cosmological solutions of (pseudo)scalar theories with periodic potentials, in the presence of arbitrary cosmological fluids – including a cosmological constant of either sign. Independently of the initial misalignment angle and field velocity, we derive an analytic bound that the
axion mass parameter and decay constant fulfill as the universe decreases its acceleration rate, finding a natural application in models of thawing quintessence. As a first application, we illustrate the analytic handle our bound provides in bounding
axion dark energy, after observational inputs from DESI and various
supernovae data sets are taken into account. As a second application, we argue that our analytic bounds in combination with proposed
quantum gravity constraints on
axions exclude vast regions of parameter space. The combined constraints push the
axion masses to be much larger than the Hubble scale, in tension with basic models of
axion quintessence.
Read the full abstract ▾
High Energy Astrophysical Phenomena
A New Measurement of the Extragalactic Background Light using 15\,yr of Fermi-Large Area Telescope Data
Anuvab Banerjee, Justin D. Finke, Marco Ajello et al. (+5 more)
The extragalactic background Light (EBL) from ultraviolet to infrared comprises the emission from all
stars,
galaxies, and actively accreting black holes in the observable Universe. A precise measurement of the EBL is critically important to probe models of
star formation and
galaxy evolution. The EBL can be measured via the absorption imprint left on the spectra of gamma-ray blazars. In this work, we rely on 15 years of
Fermi-LAT data and 1576 blazars to measure the EBL optical depth in the $0<z<4.3$ range. We detect the EBL attenuation with $\sim23\sigma$ significance and measure the optical depth in 19
redshift bins, extending the coverage and improving on our previous results. This allows us to reconstruct the EBL
evolution and find general consistency with recent EBL models. These results represent the most precise determination of the EBL with GeV $\gamma$ rays to date.
Read the full abstract ▾
All authors Anuvab Banerjee, Justin D. Finke, Marco Ajello, Alberto Domínguez, Abhishek Desai, Joshua Baxter, Dieter Hartmann, Vaidehi S. Paliya
Earth and Planetary Astrophysics
Dust Processing in Protoplanetary Discs From Infall to Dispersal: the Origin of Solar System Isotopic Heterogeneities
Mark A. Hutchison, Maria Schönbächler, Lucio Mayer et al. (+1 more)
The nucleosynthetic heterogeneity between different asteroids and
planets is well established. These isotopic variations manifest themselves at the part per millions level or larger, in isotopes that were synthesised in various
stellar environments. To escape homogenisation, some of these isotopic signatures must have been preserved in
dust, which ended up being heterogeneously distributed in the
solar protoplanetary disc. The origin of the nucleosynthetic heterogeneity is still poorly constrained, potentially reflecting inherited isotope variations from the Sun's parental molecular cloud and/or processing and redistribution during the subsequent protoplanetary disc phase with thermal processing and size sorting as major processes. This chapter aims to provide a broad review of the dynamical, collisional, and thermal processes in protoplanetary discs – from initial infall to gas dispersal – that may have influenced the distribution and survival of the anomalous carrier phases, which finally accreted into asteroids and
planets. While several of these mechanisms have been considered in past studies, they are often examined in isolation, which impedes the assessment of how their effects may be altered or amplified by additional disc processes. Size sorting in particular has received little
attention, and here we highlight that this process likely occurred in the disc and can induce nucleosynthetic heterogeneity. By placing previous studies within the context of a comprehensive overview, we aim to clarify the broader physical framework in which anomalous carrier transport occurs and identify previously underexplored mechanisms that may have contributed to the final isotopic structure of the
Solar System we see today.
Read the full abstract ▾
All authors Mark A. Hutchison, Maria Schönbächler, Lucio Mayer, Jean-David Bodénan
High Energy Astrophysical Phenomena
Radio Monitoring Campaign of Active Repeater FRB 20220912A with CHIME
Thomas C. Abbott, Aaron B. Pearlman, Victoria M. Kaspi et al. (+20 more)
FRB 20220912A is a highly active repeating fast
radio burst (FRB) source, discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) using its real-time FRB detection system (CHIME/FRB). Here, we present results from a
radio monitoring campaign of FRB 20220912A using CHIME, including ~200 hours of data collected by CHIME/
Pulsar, spanning 1.5 years following the source's discovery. We present an analysis of a sample of 828 CHIME-detected bursts from FRB 20220912A, in the 400-800 MHz
radio frequency band. The source remains highly active for ~10 weeks and has a bimodal wait-time distribution with peaks at $160^{+120}_{-70}$ ms and $306^{+14}_{-13}$ s. Assuming a
radio efficiency factor of $10^{-4}$ and a beaming angle of 0.1, we estimate the total emitted energy from the source over the entire observing campaign to be $2 \times 10^{43}$ ergs. We report a 2.3$\sigma$ detection of a linear increase in the DM of $1.4 \pm 0.6$ pc cm$^{-3}$ yr$^{-1}$, with no significant trend in rotation measure (with a 3$\sigma$ upper limit of 13.4 rad m$^{-2}$ yr$^{-1}$). We contrast our findings with other active repeaters, which exhibit different DM and RM
evolution to indicate that FRB 20220912A may reside in a unique local environment.
Read the full abstract ▾
All authors Thomas C. Abbott, Aaron B. Pearlman, Victoria M. Kaspi, Ayush Pandhi, Charanjot Brar, Alyssa Cassity, Amanda M. Cook, Alice P. Curtin, Emmanuel Fonseca, Bryan M. Gaensler, Deborah C. Good, Jason W. Hessels, Afrokk Khan, Calvin Leung, Robert A. Main, Ryan Mckinven, Bradley W. Meyers, Kenzie Nimmo, Mason Ng, Ziggy Pleunis, Paul Scholz, Vishwangi Shah, Kaitlyn Shin
Astrophysics of Galaxies
Optical identification of the FASHI sources: toward the extended Local Volume
Aleksandra E. Nazarova, Dmitry I. Makarov, Igor D. Karachentsev et al. (+3 more)
We extracted a list of 662 nearby (within $\sim16$ Mpc) HI-detection sources from the Five-hundred-meter Aperture Spherical
radio Telescope (FAST) All Sky HI Survey (FASHI) and made a visual identification of them with optical counterpart. This inspection led to the discovery of 71 new
dwarf galaxies. All of them are
dwarf irregular
galaxies with ongoing
star formation. They are characterized by the following median parameters: visual magnitude of $g=17.8$ mag and color $(g-r)=0.29$ mag, HI-flux $S_\mathrm{HI}=718$ mJy km/s, HI-mass $M_\mathrm{HI}=3.7\times10^7$ $M_\odot$, as well as the HI line-width of $W_{50}=37$ km/s.
Read the full abstract ▾
All authors Aleksandra E. Nazarova, Dmitry I. Makarov, Igor D. Karachentsev, Chuan-Peng Zhang, Maksim I. Chazov, Ming Zhu
High Energy Astrophysical Phenomena
The Northern High Time Resolution Universe pulsar survey: III. Single-pulse search continuation, follow-up observations, and initial results
L.J.M. Houben, H. Falcke, L.G. Spitler et al. (+5 more)
We continued the search for single pulses (SPs) in the northern part of the all-sky High Time Resolution Universe survey, whose aim is to detect
pulsars and other
radio transients. This search is now about 21% complete and has yielded the first discovery of a fast
radio burst (FRB) with the 100 m Effelsberg
Radio Telescope. FRB20110220A was detected with an S/N-optimised dispersion measure of 501.0 pc/cm$^{3}$ and a width of 11.9 $\pm$ 3.5 ms, for a fluence of 0.6 $\pm$ 0.1 Jy ms. We obtained the first L-band detection of the rotating
radio transient (RRAT) J2028+28, from which we obtained upper limits on the source's period and burst rate, as well as an improved position. We also discovered a new RRAT, J0404+53, which had previously been reported as an isolated SP candidate. Eight new SP trains and 272 faint isolated SP candidates were detected too. We used these candidates to demonstrate that their all-sky detection rates depend on
Galactic latitude and longitude. This direction dependence suggests the existence of a faint
Galactic SP population.
Read the full abstract ▾
All authors L.J.M. Houben, H. Falcke, L.G. Spitler, E.D. Barr, M. Berezina, D.J. Champion, R. Karuppusamy, M. Kramer
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Flux enhancement of corotating hot spots in accretion disks from the slow-light effect
Qing-Hua Zhu
With the Event Horizon
Telescope and future Very Long Baseline Interferometry arrays poised to image supermassive black holes, there is a strong motivation to understand the dynamic aspects of the
accretion flow near the black hole. Interestingly, in such highly relativistic regime, the finite light-travel time should be taken into account to correctly simulate the images, known as the slow-light effect. This paper investigates the impact of the slow-light effect on the observational signatures of hotspots corotating with the Keplerian disks. It is found that the magnification can be modulated by the hotspot's orbital velociy. Specifically, the corotating hotspots at the maxima of magnification are located at the image positions shifted relative to the positions behind the black hole. This subsequently causes the peak of the magnification profile to shift towards
alignment with the peak of the
redshift factor profile, ultimately leading to flux enhancement relative to the results of previous studies. This enhancement becomes particularly pronounced for corotating hotspots in the strong-field regime at large inclination angle, indicating that the slow-light effect is essential for accurately modeling high-energy emission in the vicinity of the black hole.
Read the full abstract ▾
Astrophysics of Galaxies
Beyond Mass and Multiscale Environments: What Shapes Low Surface Brightness Galaxies? Evidence from MaNGA
Mengting Shen, Hassen M. Yesuf, Lei Hao et al. (+4 more)
The origin of low surface brightness (LSB)
galaxies remains a key open question in
galaxy formation, reflecting the balance internal mechanisms and environmental influence. Using MaNGA integral-field spectroscopy, we investigate whether LSB and high surface brightness (HSB)
galaxies of comparable
stellar mass ($9 < \log M_\ast < 10$) occupy distinct environments or differ primarily through internal
evolution. Our late-type sample comprises 113 central and 29 satellite LSB
galaxies, and 374 central and 142 satellite HSB
galaxies. We characterize environments on scales from 100 kpc to 10 Mpc, analyzing radial profiles of
stellar mass surface density ($\Sigma_\ast$),
star formation activity, and gas-phase
metallicity. Central LSB and HSB
galaxies inhabit similarly low-density large-scale ($>$200 kpc) environments, but LSB
galaxies are more isolated on small scales ($\sim$100 kpc). Even after matching in
stellar mass and environment, LSB
galaxies show systematically lower $\Sigma_\ast$, $\Sigma_{SFR}$, and
metallicities, often hosting diffuse, weakly
star-forming bulges embedded in extended disks. These results indicate that LSB structure and
star formation are not primarily governed by large-scale environment or
halo mass. While secondary
halo properties such as
spin, concentration, or gas
accretion history are often invoked, their environmental dependence appears weak. Instead, LSB-HSB differences for centrals likely reflect divergent assembly or interaction histories and internal processes – such as angular momentum-driven disk
evolution or inefficient gas conversion – largely decoupled from large-scale environment. Nonetheless, environment still influences the observed
star formation and chemical differences between central and satellite LSB
galaxies.
Read the full abstract ▾
All authors Mengting Shen, Hassen M. Yesuf, Lei Hao, Chong Ge, Jun Yin, Junfeng Wang, Shiyin Shen
Earth and Planetary Astrophysics
Giant Planet Formation by Disk Instability
Ravit Helled, Oliver Schib, Christian Reinhardt et al. (+4 more)
The disk instability (DI) model for
giant planet formation remains an attractive alternative in explaining the formation of
giant planets at early times,
giant planets at large radial distances, and
giant planets orbiting M-
stars. In this review, we present recent developments in the disk instability model including hydrodynamical as well as magneto-hydrodynamical (MHD) disk simulations, populations synthesis models, and simulations of clump-clump collisions. We also discuss advances in observations that can be used to constrain and test this formation scenario.
Read the full abstract ▾
All authors Ravit Helled, Oliver Schib, Christian Reinhardt, Noah Kubli, Lucio Mayer, Christoph Mordasini, Gabriele Cugno
Instrumentation and Methods for Astrophysics
Recent development in high-precision high-fidelity spectrographs for exoplanet research and characterization
François Bouchy, Francesco Pepe, Xavier Dumusque et al. (+3 more)
High-precision high-fidelity spectrographs are the most powerful instruments for
exoplanets detection and characterization. The sub-m/s radial-velocity precision, required to detect Earth-mass
exoplanets, necessitates tackling all the sources of instrumental and
stellar instabilities. We present the new high-precision high-fidelity spectrographs ESPRESSO, NIRPS, ANDES and RISTRETTO designed, developed, and operated with support of
PlanetS.
Read the full abstract ▾
All authors François Bouchy, Francesco Pepe, Xavier Dumusque, Tobias Schmidt, Christophe Lovis, Stéphane Udry
Earth and Planetary Astrophysics
The formation of planetary systems: physics, populations, and architectures
Andrin Kessler, Jesse Weder, Jesse Polman et al. (+5 more)
We review the progresses made in global theoretical models of planetary system formation in the last decade using the example of the planetary system formation framework known as the Bern Model that has been continuously developed since before the beginning of the NCCR
PlanetS. We highlight major developments and applications that have since been implemented, reflecting important recent advancements of
planet formation theory overall, such as MHD wind-driven disk
evolution, planetesimal
evolution including fragmentation,
dust evolution and pebble
accretion, formation of
planets in structured disks, interior structure models allowing for compositional gradients, as well as the analysis of the emerging planetary system architectures and the identification of different classes of architectures. We discuss how these new models impact the formation and
evolution process and translate into different populations of
planets and planetary systems. We also discuss the major strengths of the Bern Model, including successful predictions of the break in the planetary mass function at 30 MEarth, the prevalence of low-mass
planets, the radius pile-up around 1 RJupiter, and the evaporation valley, with the recent New Generation Planetary Population Synthesis models with 100 seeds per disk providing quantitive matches to many RV-survey and Kepler diagnostics. This includes key characteristics of planetary system architectures. We also highlight the limitations of this model, some of them were addressed during the course of the NCCR
PlanetS: the inclusion of the early phases of
planet formation from
dust to planetesimals, the hybrid pebble-planetesimals
accretion of solids, simplified interior structure models, reliance on simplified parametrizations that may not encapsulate the full complexity of physical processes, and computational constraints.
Read the full abstract ▾
All authors Andrin Kessler, Jesse Weder, Jesse Polman, Nicolas Kaufmann, Jeanne Davoult, Alexandre Emsenhuber, Yann Alibert, Christoph Mordasini
Astrophysics of Galaxies
Photoionization modelling of circumstellar nebulae using irregular grains
P. Jiménez-Hernández, S.J. Arthur, D. Guirado et al. (+4 more)
We study the effects of using the optical properties of irregular hexahedral grains in photoionization models of circumstellar nebulae around evolved
stars.
Dust opacities for the irregular grains were obtained from the scattering properties available in the TAMUdust2020 database and these were implemented in the spectral synthesis code cloudy. A sample of photoionization models that use opacities from both spherical and irregular hexahedral grains across a standard MRN size distribution (0.005 to 0.25 um) was produced. We consider the optical properties of graphite, amorphous carbon and silicate
dust grains and find that differences between the model nebula continua calculated using spherical and irregular
dust grains increase with the grain size, especially for graphite. In particular, we find that the luminosities at the infrared peak for the hexahedral grain models can be up to 60% higher than those from the equivalent spherical grain models for the largest grains. This result suggests that traditional spherical grain assumptions may lead to an overestimate of the
dust mass in photoionized nebulae.
Read the full abstract ▾
All authors P. Jiménez-Hernández, S.J. Arthur, D. Guirado, O. Muñoz, J. Martikainen, L. Sabin, W.J. Henney
Earth and Planetary Astrophysics
Recent advances in modelling of global-scale collisions using smoothed particle hydrodynamics
Christian Reinhardt, Sabina D. Raducan, Thomas Meier et al. (+3 more)
Impacts play a fundamental role in shaping the physical and chemical properties of the objects in our
Solar System. Given the challenges in replicating such collisions through laboratory experiments, computer simulations are an important tool to investigate their outcomes. Accurately modelling material properties such as shear strength, porosity, and the formation of cracks is crucial for understanding impacts on small bodies like asteroids and comets. Very large and massive objects are dominated by self-
gravity and can be approximated as a fluid. In this regime the equation of state used to model the behaviour of the constituent materials plays a key role. However, for bodies of several hundred kilometres, which are already spheroidal due to self-
gravity, shear strength must still be considered. This impact regime is most challenging to model and therefore often overlooked in publications. In this review we present different impact regimes and the relevant physics that must be included. We then discuss their application to a variety of
Solar System objects and assess how recent observations and numerical simulations, focussing on the Smoothed Particle Hydrodynamics method, can be used to inform our understanding of impact processes and
solar system formation.
Read the full abstract ▾
All authors Christian Reinhardt, Sabina D. Raducan, Thomas Meier, Martin Jutzi, Joachim Stadel, Ravit Helled
Earth and Planetary Astrophysics
Spectral signatures from the habitable zone
Vincent Kofman
This work describes the context and approach for the detection of spectroscopic signatures from
planets in the habitable zone of nearby
stars. By understanding the limitations of current observatories, future
telescopes can be understood, and their ability to characterize the atmospheres of
exoplanets estimated. An example calculation is given for the signal-to-noise analysis for a
planet like the current Earth of oxygen as a biosignature, and (an enhanced abundance) of hydrogen iodine as a technosignature. In the optimistic estimate, Earth is easily detected, O2 characterized in 20 hours, but signals from enhance HI are only visible after hundreds of hours, indicating the signals are too weak to realistically constrain.
Read the full abstract ▾
Earth and Planetary Astrophysics
Polarimetry in Planetary Sciences and Astronomy
C.H. Lucas Patty, Jonathan Grone, Brice-Olivier Demory et al. (+7 more)
In recent decades, the relevance of polarimetry in planetary sciences and astronomy has increased rapidly. Polarization is a fundamental property of light and can be modified by any scattering event. As such, polarization yields additional information that cannot be obtained by only assessing light's scalar properties. For instance, the polarization state of starlight scattered by planetary surfaces can provide useful insights on the composition, size, morphology, and porosity of regolith particles and might even indicate the presence of life. Beside being useful for characterization, polarimetry can also greatly enhance the detection of
exoplanets. Here, polarization can be harnessed to enhance the contrast between the bright light of a
star, which can be considered to be fully unpolarized, and the very dim but polarized light reflected by an
exoplanet. In this paper, we discuss and review the current developments and advances in optical polarimetry and polarimetric instrumentation in Switzerland within the framework of the National Centre of Competence in Research
PlanetS. We focus on their implications for the vast range of science cases that polarimetry can address within the research fields of planetary science and astronomy.
Read the full abstract ▾
All authors C.H. Lucas Patty, Jonathan Grone, Brice-Olivier Demory, Jonas Kühn, Jie Ma, Willeke Mulder, Olivier Poch, Antoine Pommerol, Hans Martin Schmid, Stefano Spadaccia
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Probing the Kinematic Dipole with LISA: an analytical treatment
Jacopo Fumagalli, Giulia Cusin, Cyril Pitrou et al. (+1 more)
The motion of the
Solar System with respect to the
cosmic rest frame induces a kinematic dipole in the
stochastic gravitational-wave background (GWB). Detecting this signal with space-based interferometers would provide an independent measurement of our peculiar velocity and a GW probe of
cosmic anisotropies. We present a fully analytic derivation of the response of the
Laser Interferometer Space
Antenna (LISA) to a kinematic dipole, and construct an optimal
estimator for its detection. We show that the dipolar response is governed by a single frequency-dependent function fixed by
symmetry, and we compute its behaviour across the LISA band. Using Fisher forecasts, we find that for a scale-invariant background detectability requires $h^2\Omega_{\rm GW} \gtrsim 5\times 10^{-8}$ for fiducial LISA, and $h^2\Omega_{\rm GW} \gtrsim 5\times 10^{-10}$ for a detector with characteristic instrumental-noise amplitudes improved by an order of magnitude. Prospects are more favorable for signals with richer frequency profile. We also explore the potential of the kinematic dipole to break degeneracies, particularly in the presence of strong
galactic foregrounds or noise features that closely mimic the
primordial signal.
Read the full abstract ▾
All authors Jacopo Fumagalli, Giulia Cusin, Cyril Pitrou, Gianmassimo Tasinato
Solar and Stellar Astrophysics
A Convolutional Neural Network-Derived Catalog of Solar Flares from Soft X-Ray Observations
Nastaran Farhang, Michael. S. Wheatland and Andrew Melatos
A convolutional neural network (CNN) is used to construct a new catalog for
solar flares based on high resolution (1-s cadence) Geostationary Operational Environmental Satellites (GOES) soft X-ray data. The CNN is trained to identify
flare rise episodes. From 1 January 2018 to 22 August 2025, the
algorithm detects 111,580
flare candidates, compared with 14,612 events in the corresponding GOES catalog. For each candidate, the probability of being a true positive is quantified by
Bayesian inference based on the peak flux, rise time, and temporal coincidence with cataloged events where available. The
flare size and waiting-time distributions are studied and compared with the GOES catalog. The CNN catalog shows a steeper power-law index for raw peak fluxes (-2.59 -\+ 0.02) than GOES (-2.25 -\+ 0.04), indicating the CNN's higher sensitivity to small events. After background correction, the indices are -1.97 -\+ 0.02 (CNN) and -2.05 -\+ 0.04 (GOES). The CNN catalog extends the power-law distribution of
flare peak fluxes by one order of magnitude at the small-flux end compared with the GOES background-subtracted catalog. A
Bayesian blocks analysis of the waiting-time distributions from the GOES and CNN catalogs indicates broad consistency with a piecewise Poisson process. We find that previously reported correlations between
flare sizes and waiting times are significantly influenced by obscuration, that is, under-counting weaker or overlapping
flares during periods of elevated flux. The new CNN catalog provides a foundation for complete and consistent studies of
solar flare statistics.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Genericness of quantum damping of cosmological shear in modified loop quantum cosmology
Wen-Cong Gan, Leila L. Graef, Rudnei O. Ramos et al. (+2 more)
In arXiv:2603.18175, the authors argue, based on numerical studies of particular cases, that the
quantum damping of cosmological shear in a modified loop
quantum cosmological model (mLQC-I) that was recently found in arXiv:2510.14021 is not generic and that the universe never becomes truly classical. In this brief Note, we revisit these claims by carefully examining the underlying assumptions and the class of initial conditions considered. We show that the examples analyzed in arXiv:2603.18175 correspond to configurations that do not represent physically admissible collapsing Bianchi I universes, as they involve mixed expanding-contracting directions and lead to effectively lower-dimensional post-bounce geometries. Restricting to physically relevant initial conditions corresponding to genuine three-dimensional contraction, we find that the
quantum damping of cosmological shear is a robust dynamical feature. This conclusion is supported by both numerical and perturbative analyses, which demonstrate that the post-bounce
evolution admits an isotropic attractor, with anisotropies decaying exponentially and independently of the matter content, provided that the weak energy condition is satisfied. We further outline a plausible post-bounce mechanism for the onset of classicalization.
Read the full abstract ▾
All authors Wen-Cong Gan, Leila L. Graef, Rudnei O. Ramos, Gustavo S. Vicente, Anzhong Wang
Astrophysics of Galaxies
What Heats the Dense Gas in the Galactic Center?
Zhenyi Yue, Yiping Ao, Xindi Tang et al. (+3 more)
Previous studies using p-H$_2$CO $J=3$–$2$ transitions at 218 GHz suggested widespread high-temperature gas exceeding 60 K and even 100 K in the CMZ, with heating mechanisms possibly related to
cosmic rays or turbulent dissipation. However, at temperatures above 100 K, p-H$_2$CO $J=3$–$2$ line emission may lead to significant overestimates of kinetic temperature. This study combines o-H$_2$CO $J=5$–$4$ data from JCMT with p-H$_2$CO $J=3$–$2$ data from APEX to analyze three molecular clouds (The Brick, Sgr A1, and Sgr A2) with high temperatures. We used the non-LTE radiative transfer code RADEX to model spectral lines and constrain physical parameters with multiple line ratios, obtaining more reliable kinetic temperatures. Our results show that the previously reported extreme temperatures ($>100$ K) based on p-H$_2$CO $J=3$–$2$ line ratios are revised downward, with the average kinetic temperatures now constrained to 84–95 K using o-H$_2$CO $J=5$–$4$ line ratios, indicating systematic overestimation in the earlier studies. Further analysis reveals that the relationship between temperature and gas line width aligns more closely with predictions from models incorporating both high
cosmic ray ionization rate and turbulent heating, suggesting that these molecular clouds are likely heated by a combination of
cosmic-ray and turbulent dissipation mechanisms.
Read the full abstract ▾
All authors Zhenyi Yue, Yiping Ao, Xindi Tang, Xing Lu, Yan Gong, Christian Henkel
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
labrador: A domain-optimized machine-learning tool for gravitational wave inference
Javier Roulet, Marco Crisostomi, Lucy M. Thomas et al. (+1 more)
Fast and reliable inference of gravitational-wave source parameters is crucial for analyzing large catalogs that are reaching the size of hundreds of detections, and for identifying short-lived electromagnetic counterparts. Neural posterior estimation has emerged as a powerful inference method, where the model is trained on simulated gravitational-wave data at considerable computational cost, but thereafter enables extremely fast and inexpensive inference at test time. Here, we extend this approach by incorporating domain-specific physical insights and methods in the model architecture. These include compressing the data by heterodyning against a reference waveform chosen via approximate likelihood maximization, removing parameter degeneracies through tailored coordinate systems, and eliminating known multimodalities by folding the parameter space. As a result, the network is approximately equivariant to changes in the source parameters, and achieves a reduced training cost and improved model interpretability. Our implementation, called labrador, can be trained end-to-end on a 1-day timescale on $\sim 10^2$ CPU cores and a V100 GPU, achieving a median importance-sampling efficiency of 1% on quadrupolar, aligned-
spin signals in a broad mass range (chirp mass $\mathcal{M} \in 1\text{-}50\,\mathrm{M}_\odot$, mass ratio $q > 0.1$). labrador is the first neural inference code to achieve extensive coverage of long-duration signals with secondary masses $m_2 < 10\,\mathrm{M}_\odot$, rendered possible by its equivariance property. Among our novel contributions is a numerically stable procedure that enables neural posterior estimation when the simulation and inference priors differ.
Read the full abstract ▾
All authors Javier Roulet, Marco Crisostomi, Lucy M. Thomas, Katerina Chatziioannou
Cosmology and Nongalactic Astrophysics
FolpsD: combining EFT and phenomenological approaches for joint power spectrum and bispectrum analyses
P. Bansal, A. Aviles, H. E. Noriega et al. (+56 more)
We present a theoretical model for the power spectrum and bispectrum of
galaxy clustering that exploits the complementarity between small-scale power spectrum information and large-scale bispectrum measurements. We extend the FOLPS code by combining its one-loop EFT
galaxy power spectrum with a tree-level
galaxy bispectrum projected onto the tripolar spherical harmonics (Sugiyama) basis. To access additional small-scale information, we also consider a line-of-sight damping factor in both statistics, mirroring approaches commonly used in studies of
redshift-space distortions. We test the model using DESI DR2
galaxy mocks. Even without damping, the joint analysis of the EFT power spectrum and bispectrum significantly improves constraints and reduces parameter degeneracies relative to power spectrum analyses alone. For LRG-like samples, including the damping further extends the range beyond $k\sim 0.3 \,h \text{Mpc}^{-1}$ in the power spectrum and $k \sim 0.24 \,h \text{Mpc}^{-1}$ in the bispectrum without introducing statistically significant parameter biases. This leads to up to $\sim 30\%$ tighter constraints on $A_s$ and $\omega_{cdm}$. For low signal-to-noise tracers such as QSOs, however, the damping parameters are weakly constrained and can absorb noise fluctuations, leading to shifts in inferred parameters. Similar limitations may arise in models where cosmological information is encoded in power-spectrum shape features degenerate with the damping, such as scenarios with massive
neutrinos. In contrast, for $w_0w_a$CDM we obtain $15\%$ and $21\%$ tighter constraints on $w_0$ and $w_a$, respectively, yielding a deviation from constant dark energy at slightly more than the $1\sigma$ level using full-shape information alone. The code is publicly available at https://github.com/cosmodesi/FolpsD
Read the full abstract ▾
All authors P. Bansal, A. Aviles, H. E. Noriega, C. Guandalin, I. Garzon, G. Niz, M. S. Wang, U. Andrade, F. Beutler, A. de Mattia, D. Gonzalez, J. Hou, D. Huterer, E. Paillas, M. Pellejero Ibanez, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, B. Dey, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, C. Hahn, H. K. Herrera-Alcantar, K. Honscheid, C. Howlett, M. Ishak, R. Joyce, S. Juneau, D. Kirkby, A. Kremin, M. Landriau, L. Le Guillou, M. Manera, A. Meisner, R. Miquel, S. Nadathur, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, M. Schubnell, H. Seo, J. Silber, G. Tarlé, B. A. Weaver, P. Zarrouk, R. Zhou
Instrumentation and Methods for Astrophysics
cTreeBalls: a fast 3-point correlation function code for clustering measurements
Mario A. Rodriguez-Meza, Eladio Moreno, Alejandro Aviles et al. (+1 more)
cTreeBalls (cBalls for short) is a Python/C package useful to measure (2,3)-point clustering statistics. cBalls can efficiently calculate 3-point correlations of more than 200 million HEALPix pixels ( a full sky simulation with Nside = 4096) in less than 10 minutes on a single high-performance computing node, enabling a feasible analysis for the upcoming LSST data. It builds upon octree (Barnes & Hut, 1986) and kd-tree
algorithms (Bentley, 1975), and supplies a user-friendly interface with flexible input/output (I/O) of catalogue data and measurement results, with the built program configurable through external parameter files and tracked through enhanced logging and warning/exception handling. For completeness and complementarity, methods for measuring two-point clustering statistics for periodic boxes are also included in the package. cTreeBalls was developed for its use in the Dark Energy Science Collaboration (DESC) of the Rubin Observatory Legacy Survey of Space and Time (LSST).
Read the full abstract ▾
All authors Mario A. Rodriguez-Meza, Eladio Moreno, Alejandro Aviles, Gustavo Niz
Solar and Stellar Astrophysics
Validating a Non-conventional Method for Expansion of Coronal Mass Ejections (CMEs) and Investigating the Evolution of a CME Substructures Using Solar Orbiter and Wind Observations
Anjali Agarwal, Wageesh Mishra, Mathew J. Owens et al. (+1 more)
We present a validation of our recently proposed non-conventional method, Constant Acceleration Accounted Perspective (CAAP), for estimating the instantaneous expansion speed of coronal mass ejection (CMEs), even when only single-point in situ observations are available. This validation is enabled by the radial
alignment of SolO and Wind spacecraft (0.13 AU radial and 2.3 deg angular separation), providing simultaneous observations of the center (at Wind) and trailing edge (at SolO) of a CME associated
magnetic cloud (MC) during 3-5 November 2021, allowing a direct measurement of its instantaneous expansion speed. These measurements are compared with CAAP-derived instantaneous expansion speed estimates at both spacecraft. The favorable spacecraft configuration also enables tracking the temporal
evolution of CME substructures, including the shock, sheath, and MC. A discrepancy is noted between the low-inclination MC axis estimated from minimum variance analysis (MVA) and the highly inclined ENW-type MC axis suggested by visual inspection of in situ measurements. We also observe an apparent increase in the
magnetic flux within the MC from SolO to Wind, indicating a noticeable deviation from
magnetic flux conservation. During the CME's propagation from SolO to Wind, the shock becomes unexpectedly stronger at Wind, while the sheath thickness remains nearly the same, likely due to MC acceleration from back compression by a high-speed stream and ambient
solar wind variability. Our results demonstrate the applicability of the CAAP method and the importance of accounting for temporal
evolution in CME substructures for space weather studies.
Read the full abstract ▾
All authors Anjali Agarwal, Wageesh Mishra, Mathew J. Owens, Tanja Amerstorfer
Earth and Planetary Astrophysics
Overview of Hayabusa2 extended mission's flyby of Near-Earth Asteroid (98943) Torifune
Masatoshi Hirabayashi, Masahiko Hayakawa, Yuya Mimasu et al. (+18 more)
The Hayabusa2 extended mission, nicknamed Hayabusa2# (# is pronounced SHARP, which stands for the Small Hazardous Asteroid Reconnaissance Probe), is JAXA's small body explorer to conduct science and engineering investigations in space. After the successful return to the Earth with the samples from the carbonaceous asteroid (162173) Ryugu on December 6, 2020, Hayabusa2 diverted away from Earth to start its decade-long extended mission. The major scope includes engineering demonstration of long-term maintenance strategies for spacecraft and operation systems and scientific investigations during various mission phases. Major scientific investigations include spacecraft-based telescopic observations of
exoplanets and zodiacal
dust observations during the cruise phase, flyby observations of the near-Earth asteroid (98943) Torifune in July 2026, and rendezvous observations of near-Earth asteroid 1998 KY26 in 2031. This study overviews Hayabusa2#'s flyby and the physical properties of Torifune. Although the flyby operation planning is still ongoing, the mission will attempt to fly by the target at a distance (from the asteroid's center) of ~1-10 km. The flyby speed is planned to be 5.25 km/s, while the encounter location is 0.81 au from the sun. The mission plans to fix the spacecraft's orientation during the flyby, only allowing for a very limited pointing change to attain higher resolution imaging. The mission will attempt to obtain science and engineering returns during the flyby. The planned investigations will offer stronger insights into material transport mechanisms in the inner
solar system and a demonstration of planetary defense technologies.
Read the full abstract ▾
All authors Masatoshi Hirabayashi, Masahiko Hayakawa, Yuya Mimasu, Naru Hirata, Takuya Iwaki, Shunichi Kamata, Kohei Kitazato, Toru Kouyama, Naoya Sakatani, Hajime Yano, Koki Yumoto, Masahiro Fujiwara, Sumito Shimomura, Takanao Saiki, Hiroshi Takeuchi, Eri Tatsumi, Yuichi Tsuda, Yasuhiro Yokota, Makoto Yoshikawa, Satoshi Tanaka, Hayabusa2 Extended Mission Torifune Flyby Working Group