Earth and Planetary Astrophysics · Cross-listed from physics.flu-dyn
Influence of Rotation on Fingering Convection in Planetary Cores
Martin Gray, Celine Guervilly and Graeme Sarson
Stably stratified layers are thought to develop at the top of the
liquid metallic cores of many terrestrial
planets. We consider the case where the thermal gradient is stable but the compositional gradient is unstable, a situation particularly relevant to Mercury. The strong contrast between molecular diffusivities of temperature and composition leads to fingering convection. We investigate this process using hydrodynamical simulations in a rotating spherical shell, systematically varying the stratification strength N relative to the rotation rate $\Omega$. In all regimes, the primary fingering mode forms narrow, elongated structures that shift orientation from the rotation axis to the direction of
gravity as $N^2/\Omega^2$ exceeds 10. The fingers remain laminar, with transverse scales proportional to thermal stratification but independent of rotation. Fingering convection also drives secondary large-scale flows across most of the explored parameter space, producing diverse dynamics including zonal flows, hemispherical convection, axisymmetric poloidal bands, finger clusters, and toroidal gyres. In the rapidly-rotating regime, laterally inhomogeneous mixing generates zonal flows in thermo-compositional wind balance; zonal flow direction and amplitude depend on $N^2/\Omega^2$, with amplitude weakening for strong stratification $N^2/\Omega^2>10$. In the intermediate regime ($N^2/\Omega^2\sim 1$), axisymmetric or spiraling poloidal bands emerge within the tangent cylinder, gradually overtaking the primary fingers. For stronger stratification, finger clusters and weak, large-scale density anomalies surrounded by toroidal gyres form in the upper domain. These diverse large-scale flows may interact with the dynamo-generated
magnetic field in the deeper core, potentially influencing surface
magnetic fields.
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High Energy Astrophysical Phenomena
Star clusters in the gamma-ray sky
Giada Peron
Massive
Star Clusters (SCs) have been proposed as additional contributors to
Galactic Cosmic rays (CRs), to overcome the limitations of
supernova remnants (SNRs) to reach the highest energy end of the CR spectrum. Thanks to fast mass losses due to the collective
stellar winds, the environment around SCs is potentially suitable for particle acceleration up to PeV energies, and their energetics is enough to account for a non-negligible fraction of the
Galactic CRs. Anyhow, the theoretical expectations need to be corroborated by clear observations. Despite the increasing number of detections at different energies, the contamination of other sources often makes it difficult to constrain the contribution arising from
stellar winds only, unless one selects objects younger than a few million years, namely before
stars start to explode inside clusters. I will review the results obtained with gamma-ray data towards a few massive young
star clusters and discuss what implications these result have, especially concerning their contribution to the bulk of
Galactic CRs.
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Earth and Planetary Astrophysics
Smoothed Particle Hydrodynamics in pkdgrav3 for Shock Physics Simulations. I. Hydrodynamics
Thomas Meier, Douglas Potter, Christian Reinhardt et al. (+1 more)
We present pkdgrav3, a high-performance, fully parallel tree-SPH code designed for large-scale hydrodynamic simulations including self-
gravity. Building upon the long development history of pkdgrav, the code combines an efficient hierarchical tree
algorithm for
gravity and neighbor finding with a modern implementation of Smoothed Particle Hydrodynamics (SPH) optimized for massively parallel hybrid CPU/GPU architectures. Its hybrid shared/distributed
memory model, combined with an asynchronous communication scheme, allows pkdgrav3 to scale efficiently to thousands of CPU cores and GPUs. We validate the numerical accuracy of pkdgrav3 using a suite of standard tests, demonstrating excellent agreement with analytic or reference solutions. The code was already used in several peer-reviewed publications to model planetary-scale impacts, where SPH's Lagrangian nature allows accurate tracking of material origin and thermodynamic
evolution. These examples highlight pkdgrav3's robustness and efficiency in simulating highly dynamical, self-gravitating systems. pkdgrav3 thus provides a powerful, flexible, and scalable platform for astrophysical and planetary applications, capable of exploiting the full potential of modern heterogeneous high-performance computing systems.
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All authors Thomas Meier, Douglas Potter, Christian Reinhardt, Joachim Stadel
High Energy Astrophysical Phenomena
Modeling the Multi-Wavelength Afterglow of Short Gamma-Ray Bursts with a Plateau Phase
Chen Deng, Yong-Feng Huang, Abdusattar Kurban et al. (+6 more)
Short gamma-ray bursts (GRBs) exhibiting a plateau phase provide valuable insights into the post-merger activity of their central engines. Although the physical origin of the plateau remains uncertain, the magnetar energy injection model offers a compelling explanation that reproduces the observed temporal and luminosity features. However, previous studies relying solely on X-ray data have suffered from strong parameter degeneracies when constraining the magnetar parameters. Here we perform broadband afterglow modeling on seven short GRBs with plateau features by combining X-ray, optical, and
radio observations within the framework of the magnetar energy injection model. Key model parameters are derived by using the Markov Chain Monte Carlo method. It is found that the energy injection substantially modifies the afterglow dynamics in most events. Compared with X-ray-only analyses, our broadband modeling yields systematically a lower
magnetic field strength and a shorter
spin period for the central magnetar, corresponding to a higher injection luminosity. The study clearly shows that incorporating multi-wavelength data effectively alleviates the degeneracy between the magnetar parameters and X-ray radiative efficiency. In addition, the distribution of our short GRBs differs markedly from long GRBs when they are plotted on the initial Lorentz factor versus gamma-ray energy plane. This offset, consistent with the observed harder spectrum of short GRBs, may serve as a useful diagnostic for investigating the progenitor as larger samples are available.
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All authors Chen Deng, Yong-Feng Huang, Abdusattar Kurban, Jin-Jun Geng, Fan Xu, Xiao-Fei Dong, Hao-Xuan Gao, En-Wei Liang, Liang Li
Cosmology and Nongalactic Astrophysics
Boost operator approach to the relativistic polarized SZ effect
Erik Rosenberg and Jens Chluba
We extend the recent boost operator formalism for relativistic Compton scattering calculations to also account for polarization. This allows us to provide general, exact expressions for the polarized Sunyaev-Zeldovich (SZ) effect sourced both kinematically and from intrinsic anisotropies of the
Cosmic Microwave Background (CMB). The results are given in terms of rational operator functions that can be used to generate distortion spectra that describe the general SZ signal, reproducing the classical polarized SZ results in the appropriate limits. Our derivation allows for clear separation of physical effects in the generation of polarized SZ, and beyond the SZ application provides a general description of the Compton collision term in the Doppler-dominated regime. Through direct computation of important example cases we further illustrate the power of this new method.
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Earth and Planetary Astrophysics
Shadow-Induced Warps in Protoplanetary disks
Shangjia Zhang, Zhaohuan Zhu and Callum W. Fairbairn
Shadows are commonly observed in protoplanetary disks in near-infrared and (sub)millimeter images, often cast by misaligned inner disks or other obscuring material. While recent studies show that shadows can alter disk dynamics, only the case symmetric across the midplane (e.g., from a polar-aligned inner disk) has been studied. Here we study shadows cast by an inner disk with a $30^\circ$ mutual inclination using 3D radiation-hydrodynamical simulations. Given the same shadow shape and amplitude, the $30^\circ$ inclined shadow leads to a much stronger
accretion compared with the polar case, reaching $\alpha \sim$ 1, because the disk is squeezed twice in one azimuth, leading to shocks and strong radial flows near the midplane. The outer disk develops a warp: the inner disk region tilts toward
alignment with the shadow, while the outer, exponentially tapered disk tilts and twists in a different direction, inclined $\sim$ 32$^\circ$ relative to the inner region. Locally isothermal simulations with a prescribed temperature structure reproduce the effect, confirming that it is thermally driven.
Fourier-Hermite analysis shows that it is the m=1, n=1 temperature perturbation that drives the warp by launching bending waves, with the tilting response of the disk approximately proportional to the modal amplitude. This mode always exists unless the shadow is coplanar or polar. Given a fixed temperature contrast, the m=1,n=1 mode peaks at $\sim$15$^\circ$ mutual inclination, but still contributes substantially across 3$^\circ$ to 30$^\circ$. Shadows cause disk warps–they are not only a consequence of them. We discuss testable predictions for current and future ALMA and NIR observations.
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Cosmology and Nongalactic Astrophysics
Recalibrating Inflation: Insights from Starobinsky Gravity
Davood Momeni
Recent analyses of low-
redshift supernova and Cepheid data reveal localized shifts in the distance modulus, often interpreted as calibration anomalies or hints of new physics. We propose that these features may emerge naturally from environment-dependent modifications to
gravity. In particular, we examine the Starobinsky \(f(R) = R + \lambda R^2\) model, which introduces a scalar degree of freedom that couples to ambient matter density and alters
photon propagation in underdense regions. We derive the corresponding corrections to luminosity distance and show that they can reproduce the observed magnitude shifts without invoking discontinuities or empirical step functions. Statistical comparisons using AIC and BIC favor the Starobinsky framework over phenomenological models, supporting its role as a minimal,
geometric explanation for emergent calibration transitions.
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High Energy Astrophysical Phenomena
A glitch in the millisecond pulsar J0900$-$3144
Bhavnesh Bhat, Michael J. Keith, Ismaël Cognard et al. (+11 more)
We report the detection of a glitch in the millisecond
pulsar (MSP) PSR J0900$-$3144, which is included in the European, MeerKAT and Parkes
pulsar timing array experiments. The
dataset combines observations from the MeerKAT, Nançay, Lovell, and Murriyang
telescopes, spanning a total baseline of approximately 14 years. The glitch occurred on MJD~59942(17), with a measured fractional
spin frequency step of $\Delta \nu_g / \nu=1.15(13) \times 10^{-12}$. This event represents the third glitch detected in a MSP, following those in PSRs B1821$-$24A and J0613$-$0200. Although smaller in amplitude than the previous two, the glitch in PSR J0900$-$3144 is of a comparable order of magnitude. The updated MSP glitch rate is $2.5(1)\times 10^{-3}$ glitches per
pulsar per year, which suggests it is likely current PTAs will detect another MSP glitch within five years. Using simulations, we demonstrate that such small glitches can go undetected, especially in short
datasets such as those from new PTAs, and can bias the inferred achromatic noise model parameters, potentially leading to the down-weighting of the
pulsar in gravitational wave background searches.
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All authors Bhavnesh Bhat, Michael J. Keith, Ismaël Cognard, Lucas Guillemot, Marcus E. Lower, Matthew T. Miles, Daniel J. Reardon, Golam Shaifullah, Ryan M. Shannon, Benjamin W. Stappers, Gilles Theureau, Shuangqiang Wang, Andrew Zic, Benjamin Shaw
Earth and Planetary Astrophysics
Close-in compact super-Earth systems emerging from resonant chains: slow destabilization by unseen remnants of formation
Max Goldberg and Antoine C. Petit
Planet formation simulations consistently predict compact systems of numerous small
planets in chains of mean motion resonances formed by
planet-disk interaction, but transiting
planet surveys have found most systems to be non-resonant and somewhat dynamically excited. A scenario in which nearly all of the
primordial resonant chains undergo dynamical instabilities and collisions has previously been found to closely match many features of the observed
planet sample. However, existing models have not been tested against new observations that show a steep decline in the resonant fraction as a function of
stellar age on a timescale of ~100 Myr. We construct a simplified model incorporating Type I migration, growth from embryos, and N-body integrations continued to 500 Myr and use it to generate a synthetic
planet population. Nearly all systems exit the disk phase in a resonant configuration but begin slowly diffusing away from the center of the resonance. Dynamical instabilities can arise on timescales of tens or hundreds of Myr, especially when systems formed in disks with a convergent migration trap. In this case, a secondary chain of smaller
planets that remained at their birth location eventually breaks, destabilizing the inner resonant chain. We also show that the instability statistics are well modeled by a Weibull distribution, and use this to extrapolate our population to Gyr ages. The close match of our modeled systems to the observed population implies that the high resonance fraction predicted by this class of models is in fact consistent with the data, and the previously-reported overabundance of resonant systems was a consequence of comparing simulations of early
evolution to mature Gyr-old systems. This result also suggests that instabilities triggered by disk dissipation or other very early mechanisms are unlikely to be consistent with observed young systems.
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Earth and Planetary Astrophysics
Formation and disruption of resonant chains of super-Earths: Secular perturbations from outer eccentric embryos
Masahiro Ogihara and Masanobu Kunitomo
Recent observations have revealed the distribution of orbital period ratios of adjacent
planets in multiple super-Earth systems and how these distributions change with time. The aim of this study is to clarify under what conditions the observed features of orbital period ratios of super-Earths can be explained, and to identify what causes the dynamical instability of super-Earths captured into resonant chains. We perform N-body simulations for 100 Myr that follow the formation and orbital
evolution of super-Earths originating from a ring of planetary embryos at 1 au from the
star. The simulations show that super-Earths undergo inward migration in the disk and are captured into mean-motion resonances with their neighbors. As a result, several resonant pairs form a resonant chain. After disk dispersal, some of these chains become dynamically unstable. In such cases, the final distribution of orbital period ratios and their time
evolution can be consistent with recent observations. The instabilities of resonant chains are likely triggered by secular perturbations from embryos that remain on outer orbits beyond 1 au, indicating that not only
giant planets but also small embryos can disrupt the resonances among inner super-Earths. We therefore further investigate the secular perturbations from outer embryos using analytic formulas and additional orbital calculations. We discuss the conditions required to excite the eccentricities of inner super-Earths on a timescale of about 100 Myr. These conditions include the need for large eccentricities of the outer embryos, as well as constraints on their masses and semimajor axes.
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Astrophysics of Galaxies
Radiation magnetohydrodynamics simulations of Population III star formation during the Epoch of Reionization
Lisanne van Veenen, Piyush Sharda, Serena Viti et al. (+1 more)
Cosmological simulations find that pockets of
star-forming gas could remain pristine up until the Epoch of Reionization (EoR) due to the inhomogeneous nature of metal mixing and enrichment in the early Universe. Such pristine clouds could have formed Population III
stars, which could have distinct properties compared to their very high
redshift ($z \geq 20$) counterparts. We investigate how Population III
stars form and grow during the EoR, and whether the resulting mass distribution varies with environment or across
cosmic time. We perform high-resolution ($7.5\,\rm{au}$) radiation-magnetohydrodynamics simulations of identical
primordial clouds exposed to the CMB appropriate for $z=30$ and $z=6$, respectively, as part of the POPSICLE project. We also run a simulation at $z=6$ with a strong external Lyman-Werner (LW) background, to span across radiative environments which could host metal-free clumps during the EoR. In the limit of no external LW radiation, we find that while the
evolution of the most massive
star ($M_{\star} \approx 70\,\rm{M_{\odot}}$) is almost identical between $z=30$ and $z=6$, the latter exhibits less fragmentation, leading to a smaller cluster of
stars with a higher median
stellar mass. In the limit of high external LW radiation, we see vigorous
accretion and high
star formation efficiencies, leading to the formation of very massive ($M_{\star} > 100\,\rm{M_{\odot}}$)
stars. Our results suggest that Population III IMF could vary with
redshift simply due to the CMB, independent of the environment. We find that less massive and more compact Pop III
star clusters could form during the EoR as compared to $z \geq 20$, with the formation of very massive and supermassive
stars likely in strongly irradiated environments.
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All authors Lisanne van Veenen, Piyush Sharda, Serena Viti, Shyam H. Menon
Solar and Stellar Astrophysics
Evidence for the Keplerian orbit of a close companion around a giant star
Mats Esseldeurs, Leen Decin, Joris De Ridder et al. (+31 more)
Close companions influence
stellar evolution through
tidal interactions, mass transfer, and mass loss effects. While such companions are detected around young
stellar objects, main-sequence
stars, red
giants, and compact objects, direct observational evidence of close-in companions around asymptotic
giant branch (AGB)
stars has remained elusive. Here, we present (sub)millimeter time-domain imaging spectroscopy revealing the Keplerian motion of a close-in companion around the AGB
star pi1 Gruis. The companion, slightly more massive than the AGB
star, is likely a main-sequence
star. Unlike more evolved
stars with companions at comparable distances, pi1 Gru's companion follows a circular orbit, suggesting an eccentricity-generating mechanism late- or post-AGB. Our analysis suggests that model-predicted circularization rates may be underestimated. Our results highlight the potential of multi-epoch (sub)millimeter interferometry in detecting the Keplerian motion of close companions to
giant stars and open avenues for our understanding of
tidal interaction physics and binary
evolution.
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All authors Mats Esseldeurs, Leen Decin, Joris De Ridder, Yoshiya Mori, Amanda I. Karakas, Jolien Malfait, Taïssa Danilovich, Stéphane Mathis, Anita M. S. Richards, Raghvendra Saha, Jeremy Yates, Marie Van de Sande, Maarten Baes, Alain Baudry, Jan Bolte, Thomas Ceulemans, Frederik De Ceuster, Ileyk El Mellah, Sandra Etoka, Carl Gottlieb, Fabrice Herpin, Pierre Kervella, Camille Landri, Louise Marinho, Iain McDonald, Karl Menten, Tom Millar, Zara Osborn, Bannawit Pimpanuwat, John Plane, Daniel J. Price, Lionel Siess, Owen Vermeulen, Ka Tat Wong
Solar and Stellar Astrophysics
Empirical prediction of plasma emission measure distributions and X-EUV spectra of late-type stars
Antonio Maggio, Ignazio Pillitteri, Jorge Sanz-Forcada et al. (+1 more)
High-energy emission spectra from the outer atmospheres of late-type
stars represent an important feature of the
stellar activity in several contexts, such as the photoevaporation and photochemistry of planetary atmospheres or the modeling of irradiated circumstellar disks in young objects. An accurate determination of these spectra in the EUV and soft X-ray (XUV) band requires high-resolution spectroscopy, that is rarely feasible with current instrumentation. We employed a relatively large set of
plasma emission measure distributions (EMDs) as a function of temperature, derived from FUV and X-ray emission line spectra acquired with the Hubble Space
Telescope and Chandra or XMM-Newton, in order to devise a relatively simple recipe for predicting EMDs and XUV spectra of
stars of different spectral types, activity levels, and
plasma metallicity. We show that the EMDs in the range of temperatures between 10^4 K and 10^7.5 K can be described using the
stellar surface X-ray flux as a control parameter, but this parameterization also depends on the spectral type. In particular, we find that M-type
stars show slightly lower emission measure at temperatures below ~10^5 K and higher emission measures for T > ~10^6.5 K with respect to FGK
stars with similar surface X-ray fluxes. We evaluated the uncertainties in the broad-band EUV and X-ray fluxes derived from synthetic EMDs and spectra, considering in the error budget also the limited knowledge of the chemical abundances in
stellar outer atmospheres.
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All authors Antonio Maggio, Ignazio Pillitteri, Jorge Sanz-Forcada, Giuseppina Micela
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Dark Matter Capture in Supernovae Modifies Dark Photon Cooling Bounds
Aritra Gupta and Manibrata Sen
Core-collapse
supernovae serve as powerful probes of light, weakly coupled particles, such as dark
photons. The conventional SN1987A cooling bound constrains the dark
photon mass-mixing parameter space by requiring that the luminosity from the proto-
neutron star core not exceed the observed
neutrino emission. In this work, we revisit these limits by including the effect of dark matter (DM) captured inside the progenitor
star before collapse. The trapped DM acts as an additional scattering target for dark
photons, modifying their free-streaming length and, consequently, the
supernova cooling rate. We perform a self-consistent analysis for both annihilating and asymmetric DM scenarios, incorporating light-mediator effects in the capture rate calculation. For annihilating DM, the
equilibrium density remains too small to affect the bounds significantly. In contrast, asymmetric DM can accumulate to large densities, leading to the formation of a "dark photosphere" that suppresses the dark-
photon luminosity and reopens regions of parameter space previously excluded by
supernova cooling. The results presented are intended as a proof-of-principle demonstration of how astrophysical dark matter populations can alter
supernova cooling constraints and do not provide precision exclusion limits on any given model.
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Cosmology and Nongalactic Astrophysics
Constraints on the canonical single-field slow-roll inflation model from observations
Jun Li, Guanghai Guo, Pengfei Yan et al. (+1 more)
In this work, we employ two complementary approaches to constrain the canonical single-field slow-roll inflation scenario. The first method makes explicit use of the analytic dependence of the
primordial perturbations on the slow-roll parameters, whereas the second adopts a phenomenological parameterization of the
primordial scalar and tensor spectra. Using the latest observational
datasets, including Planck satellite data, BICEP/Keck measurements,
baryon acoustic oscillation data, and the recent DESI Data Release 2, we derive direct constraints on the slow-roll parameters. A key advantage of this strategy is that it allows us to compute the predictions of single-field slow-roll inflation directly from the constrained parameter values. We illustrate the resulting predictions for the parameters that characterize the scalar power spectrum and place constraints on several representative inflationary models. Our analysis shows that monomial-potential inflation is disfavored, while models with concave potentials, such as the Starobinsky model and brane inflation, are preferred. From the constraints on the slow-roll parameters, we obtain a tensor spectral index in the single-field slow-roll framework that is very small, $|n_t|\lesssim 4.9\times 10^{-3}$, a value that will be challenging to measure with CMB data alone in the foreseeable future. Moreover, the absolute value of the derived running of the tensor spectral index does not exceed $1.91\times 10^{-4}$ at $95\%$ confidence level, based on the combination of CMB+BAO+DESI
datasets.
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All authors Jun Li, Guanghai Guo, Pengfei Yan, Xiong Yang
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
NJL-Chiral Soliton and the Nucleon Equation of State at supra-saturation density: Impact of Chiral Symmetry Restoration
Bikram Keshari Pradhan, Guy Chanfray, Hubert Hansen et al. (+1 more)
It has been conjectured that, at sufficiently high
baryon densities, the equation of state (EoS) of bulk
nuclear matter can be identified with that of the nucleon core. In this work, we illustrate how the energy density and pressure distributions inside individual nucleons can be utilized to construct the EoS of supra-dense matter. In our framework, nucleons arise as topological
solitons stabilized by vector
mesons, which are dynamically generated through the path integral bosonization of an underlying Nambu-Jona-Lasinio (NJL) model. The restoration of
chiral symmetry is implemented dynamically via a self-consistent, density-dependent scalar field, which modifies the (isovector) and (isoscalar) channels of the
soliton. We analyze the resulting changes in
soliton properties for different NJL parameter sets and demonstrate that the progressive restoration of
chiral symmetry leads to a stiffening of the
soliton-based EoS, making it compatible with existing
neutron star EoSs. An EoS constructed from the solutions of the energy-density and pressure profiles at the center of the nucleon is also explored.
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All authors Bikram Keshari Pradhan, Guy Chanfray, Hubert Hansen, Jérôme Margueron
Cosmology and Nongalactic Astrophysics
Galactic foreground residue biases in cosmic-microwave-background lensing-convergence reconstruction and delensing of B-mode maps
Kishan Deka and Pawel Bielewicz
Diffuse contamination from
Galactic foreground emission is one of the main concerns for reconstruction of the
cosmic microwave background (CMB)
lensing potential for next-generation CMB polarisation experiments. Using realistic simulations, we investigated the impact of
Galactic foreground residuals from multi-frequency foreground-cleaning methods on CMB
lensing reconstruction and the de-
lensing of B-mode maps. We also assessed how these residuals affect constraints on the tensor-to-scalar ratio for a CMB-S4–like experiment. We paid special
attention to the errors coming from the small scale non-Gaussianity of the foreground residuals. We show that component separation is essential for the
lensing reconstruction that reduces
Galactic emission contribution to the
lensing reconstruction errors by one order of magnitude. The residual foreground contribution is dominated by terms coming from Gaussian components of the residual maps. Errors coming from non-Gaussian components are around three orders of magnitude smaller than the Gaussian one, even for recent and the most complex models of the
Galactic emission considered in this work. Although the bias in the reconstruction errors due to the Gaussian component of the residuals being small, it is comparable to the
cosmic variance limit for the
lensing power spectrum. For this reason, we corrected for this bias in the de-
lensing of B-mode maps and constraining the tensor-to-scalar ratio. We also show that for the de-lensed B-mode maps with a simple quadratic
estimator, that is, residuals of the
Galactic emission after component separation, errors are two orders of magnitude smaller than uncertainties from leftover of the
lensing signal. However, for high-sensitivity CMB experiments and more efficient de-
lensing algorithms that remove up to 90% of the
lensing signal, the foreground residuals will become one of the main sources of errors.
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Instrumentation and Methods for Astrophysics
A Simulation Platform for Small Solar System Bodies' Gravity Using the Einstein-Elevator
E. Tahtali, C. Kreuzig, G. Meier et al. (+3 more)
Small
solar system bodies (SSSB), which in this study are defined primarily as asteroids and comets, are becoming increasingly important as more data have become available for their study. Their significance is also highlighted by missions like NASA's OSIRIS-REx or ESA's Rosetta. However, the study of the characteristics and behavior of these objects on Earth is a challenge as the simulation of their environmental conditions are difficult. We present in this paper an approach to enable the
gravity simulation of SSSBs such as comets or asteroids in a drop tower facility on Earth, which is being addressed as part of the AKUS ("Activity of Comets under Partial
Gravity") project. This especially concerns
gravity levels between 10$^{-2}$~g and 10$^{-4}$~g, where the duration of the adjusted acceleration ranges from 2.5 to 3.2 seconds. In order to simulate the conditions of SSSB as accurately as possible, an acceleration system based on servo motors and spindle axes has been developed. The accelerations are transferred from the motors to the spindle axes containing a comet-like sample. The current dimensions of the total load (including sample, sample holder, data- and communication box) are 315~mm x 160~mm x 331~mm (w x d x h), with a total weight of approximately 15~kg. These are together placed inside a
vacuum chamber providing a
vacuum quality of 10$^{-6}$~mbar. The whole setup is installed inside the Einstein-Elevator. Our results show that, with the current setup, we are able to generate conditions from 10$^{-2}$~g down to 10$^{-3}$~g. The maximum deviations under these conditions are $\pm5$$\cdot 10^{-4}$~g.
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All authors E. Tahtali, C. Kreuzig, G. Meier, J. Blum, L. Overmeyer, C. Lotz
Astrophysics of Galaxies
The Spatial Evolution of Star Clusters in NGC 628 with JWST
Anne S. M. Buckner, Ana Duarte-Cabral, Angela Adamo et al. (+23 more)
We examine the spatial distribution of
star clusters in NGC 628 using the statistical tool INDICATE to quantify clustering tendencies. Our sample, based on HST and JWST observations, is the most complete to date, spanning ages from 1 Myr to >100 Myr. We find cluster spatial behaviour varies with
galactic position, age, and mass. Most emerging young clusters are tightly spatially associated with each other, while fully emerged clusters are in \sim1.5 times looser spatial associations, irrespective of age. Young Massive Clusters (YMCs \ge 10^4 M_{\odot}) tend to associate with lower-mass clusters but not strongly with other YMCs, implying that intense
star formation regions produce a few YMCs alongside many lower-mass clusters rather than multiple YMCs together. Young concentrated clusters show a wide radial distribution in the
galactic disk, which narrows with age; with concentrated clusters >100 Myr mostly residing between 2-6 kpc. This pattern may reflect either faster dispersal of isolated tight cluster spatial "structure" in a lower gas density outer disk or gradual inside-out growth, with the formation of this structure shifting outward over time. We also detect distinct spatial behaviours for clusters within 2 kpc, linked to the inner Lindblad resonance (\le1 kpc),
nuclear ring (\sim0.5-1 kpc), and the start of spiral arms (\sim1.25-2 kpc), suggesting these regions exhibit strong radial motions that could hinder clusters from forming and remaining in tight concentrations. Our results highlight how spatially-resolved studies of clusters can reveal the influence of
galactic dynamics on
star formation and cluster
evolution.
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All authors Anne S. M. Buckner, Ana Duarte-Cabral, Angela Adamo, Sean Linden, Michele Cignoni, Varun Bajaj, Arjan Bik, Giacomo Bortolini, Daniela Calzetti, Matteo Correnti, Bruce G. Elmegreen, Debra M. Elmegreen, Helena Faustino Vieira, John S. Gallagher III, Kathryn Grasha, Benjamin Gregg, Rob A. Gutermuth, Kelsey Johnson, Mark Krumholz, Drew Lapeer, Matteo M. Messa, Göran Östlin, Alex Pedrini, Jenna E. Ryon, Linda J. Smith, Monica Tosi
High Energy Astrophysical Phenomena
Highly Polarized Intrinsic Emission and its Orthogonal Counterpart in Vela X-1
WanYun Wu, Fei Xie, Long Ji et al. (+2 more)
Vela X-1 is one of the most archetypal wind-fed X-ray
pulsars (XRPs), and the emergence of its orthogonal polarization states reveals distinctive polarimetric properties. Using data from Imaging X-ray Polarimetry Explorer (IXPE) observations of Vela X-1, we perform a polarization analysis of Vela X-1 using a triple power-law spectral model absorbed by varying column densities, successfully isolating two physically distinct orthogonal polarized components. The first polarized component corresponds to emission from the
accretion mound surface that is not obscured by the wind clumps, with its polarization degree (PD) exceeding 30%. In specific phase intervals, the PD reaches \(50.9 \pm 10.7\%\). This marks the first detection of such highly polarized
neutron star emission in an XRP. The second polarized component likely originates from complex physical processes within or near the
accretion mound, with its PD showing a potential negative correlation with column density. Furthermore, by rotating the predicted polarization angle (PA) of the first polarized component by 90$^\circ$, we successfully achieve separate fitting and simultaneous fitting of the two orthogonal polarization states using the rotating vector model (RVM).
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All authors WanYun Wu, Fei Xie, Long Ji, Mingyu Ge, Fabio La Monaca
High Energy Astrophysical Phenomena
Measurement of cosmic-ray muon flux at CJPL-II
P. Zhang, H. Ma, W. Dai et al. (+5 more)
In China Jinping Underground Laboratory (CJPL), the deepest and largest underground laboratory globally, the
cosmic-ray
muon flux is significantly reduced due to the substantial shielding provided by the overlying mountain. From 2016 to 2020, we measured the
muon flux in the second phase of CJPL (CJPL-II) with a plastic scintillator
muon telescope system, detecting 161
muon events over an effective live time of 1098 days. The detection efficiency was obtained by simulating the underground
muon energy and angular distributions and the
telescope system's response to underground
muons. The
cosmic-ray
muon flux is determined to be (3.03 $\pm$ 0.24 (stat) $\pm$ 0.18 (sys)) $\times$ 10$^{-10}$ cm$^{-2}$s$^{-1}$, which is the lowest among underground laboratories worldwide.
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All authors P. Zhang, H. Ma, W. Dai, M. Jing, L. Yang, Q. Yue, Z. Zeng, J.Cheng
Instrumentation and Methods for Astrophysics
Surface figure metrology for reflective membrane mirrors based on phase-measuring deflectometry
Xin Yan, Zhi-Kang Zhuang, Fu-Jia Du et al. (+4 more)
Reflective membrane mirrors provide a lightweight, low-cost alternative to traditional optics for next-generation large-aperture
telescopes, but their non-rigid, thin structure poses challenges for surface metrology. We present a phase-measuring deflectometry (PMD) system enhanced with tailored ray-tracing and iterative reconstruction to enable non-contact measurement of large membrane optics. The system successfully characterizes the surface figure and evaluates the dynamic stability of a 1-meter Hencky-type membrane mirror. Our results demonstrate the effectiveness of PMD as a practical metrology tool for future membrane-based
telescope systems.
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All authors Xin Yan, Zhi-Kang Zhuang, Fu-Jia Du, Wen Duan, Peilin Yin, Mo-Nong Yu, Guang Yang
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
In-situ environmental radiation background measurement in the second phase of CJPL
P. Zhang, Z. Zeng, J. Cheng et al. (+1 more)
China Jinping Underground Laboratory (CJPL), the deepest and largest underground laboratory worldwide, provides a low radiation background environment, which is necessary to frontier scientific research, such as the experimental studies of rare-event physics. Due to the almost filled space of CJPL-I and the requirement of future physics experiments, the construction of the second phase of CJPL (CJPL-II) was started in 2020 and all finished in 2024. In this work, we report the measured results of major environmental radiation in CJPL-II, including
cosmic-ray
muons, radon, gamma rays, and
neutrons. Results indicate that the rock overburden and the radioactive background control effectively minimize the environmental radiation background. The scientific data presented also serve as an important basis to detector background modeling for the physics experiments in CJPL-II.
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All authors P. Zhang, Z. Zeng, J. Cheng, H. Ma
Solar and Stellar Astrophysics
SPICE – modelling synthetic spectra of stars with non-homogeneous surfaces
M. Jabłońska, T. Różański, L. Casagrande et al. (+4 more)
In the era of large time-domain spectro-photometric surveys, surface variations such as starspots, chemical inhomogeneities, pulsations, rotational distortions, and binary interactions can now be directly detected and modelled. Accurately interpreting these phenomena requires
stellar spectral synthesis frameworks that go beyond the assumption of homogeneous surface properties. Yet most existing tools remain limited by this simplification, hindering their applicability to
stars with complex surface structures. To address this need, we present SPICE (SPectral Integration Compiled Engine), an open-source Python package for generating high-resolution spectra and photometry from non-homogeneous
stellar surface models. SPICE integrates angle-dependent specific intensities from each surface element, enabling forward modelling of both photometric and spectroscopic variability. Case studies demonstrate applications to spotted
stars, Cepheid pulsations, and eclipsing binaries, making SPICE well-suited for analysing current and upcoming survey data. In addition, SPICE can directly import meshes from PHOEBE, enabling the modelling of complex binary configurations beyond these case studies.
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All authors M. Jabłońska, T. Różański, L. Casagrande, H. Shah, P. A. Kołaczek-Szymański, M. Rychlicki, Yuan-Sen Ting
High Energy Astrophysical Phenomena
Accuracy and Applicability of the Hartle-Thorne and Komatsu-Eriguchi-Hachisu Methods for Modeling Rotating Neutron Stars
Hyukjin Kwon, Kenta Yoshimura, Tsuyoshi Miyatsu et al. (+2 more)
Neutron stars, which are composed of extremely dense
nuclear matter, serve as natural laboratories to study
nuclear interactions beyond the terrestrial experiments. Recent researches have actively explored how the equation of state (EoS) can be constrained by observed
neutron star masses and radii, and how
nuclear interactions affect their macroscopic properties. Most of these studies, however, rely on the Tolman-Oppenheimer-Volkoff (TOV) equations, which assumed static, spherically symmetric
neutron stars. Since
neutron stars are rotating objects and thus axisymmetrically deformed, the TOV calculation may be insufficient to capture their realistic structure. In this work, we investigate the influence of
nuclear matter properties on the physical quantities of rotating
neutron stars using two approaches: the perturbative Hartle-Thorne (HT) method and fully general relativistic Komatsu-Eriguchi-Hachisu (KEH) method. For
nuclear EoS parameter sets, we emamine the OMEG series, in which the slope of the
symmetry energy $L$ is systematically varied. We find that rotational effects lead to a noticeable increase in the
stellar radius, which depends sensitively on values of $L$. Additionally, focusing on the rotational deformation, we show that the results obtained by these two methods deviate each other even for the slowly rotating case such as $\Omega=200$ Hz. These results reveal that, for detailed discussions on the internal structure and stability of rotating
neutron stars, the fully general relativistic method such as KEH is indispensable.
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All authors Hyukjin Kwon, Kenta Yoshimura, Tsuyoshi Miyatsu, Kazuyuki Sekizawa, Myung-Ki Cheoun
Cosmology and Nongalactic Astrophysics
Proposal to construct the dark-matter-only counterpart of the observed universe combining weak lensing and baryon censuses
Shuren Zhou and Pengjie Zhang
Baryonic effects such as AGN feedback can significantly impact the matter clustering, are harder to model from first principles, and emerge as a severe limiting factor in weak
lensing cosmology. To tackle this issue, we propose a generic relation of mapping the observed matter clustering to its counterpart in a dark-matter-only universe. We verify this relation to be accurate at better than $1\%$ level at $k<1\,h/$Mpc and $z\in [0,3]$ in both TNG and Illustris simulations, demonstrating its model-independence to the underlying baryonic physics. Implementing this relation in observations will be made possible by the specifically designed cross-correlation statistics and
baryon census (ionized diffuse gas through localized fast
radio bursts,
stellar mass through
galaxy surveys, and neutral hydrogen through 21cm mapping). It is capable of correcting the baryonic effect not only in the matter power spectrum, but also at the field level, as demonstrated by tests on the scattering transform statistics. This approach paves the way for constructing the dark-matter-only counterpart of the observed Universe, establishing an ideal cosmological laboratory for probing the dark universe.
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High Energy Astrophysical Phenomena
Discovery of an X-ray bridge between the comma-shaped gas and the main cluster in MCXC J0157.4-0550
Chong Yang, Nobuhiro Okabe and Yasushi Fukazawa
We report the discovery of a faint X-ray bridge connecting between the comma-shaped gas and the main cluster in MCXC J0157.4-0550, using XMM-Newton image. The filamentary structure is found in a model-independent manner in both topological features and Gaussian Gradient Magnitude filtering. The X-ray surface brightness profile perpendicular to the filament is detected at a $5.5\sigma$ level. Weak-
lensing (WL) analysis using the Subaru/HSC-SSP Survey archive data strongly supports the two mass components. Given a prior from the
stellar masses, we obtain $M_{200}^{\rm main}=2.68_{-0.92}^{+1.11}\times 10^{14}\,h_{70}^{-1}M_\odot$ and $M_{200}^{\rm sub}=0.46_{-0.22}^{+0.38}\times 10^{14}\,h_{70}^{-1}M_\odot$. The main axis of the projected
halo distribution is more likely to align with the direction of the main cluster than to be oriented perpendicularly. Similar X-ray distributions have been identified in the literature on numerical simulations. The filamentary structure forms in the following manner: as the gas is stripped by ram pressure near the pericenter, it gets dragged by
tidal rotation. Once free from this rotation, the gas moves inertially in a direction parallel to the tangential velocity at the pericenter. The comma-shaped gas, with tails pointing in the opposite direction to the main cluster, is also formed by the current
tidal rotation as it moves away from the main cluster. This warrants us that, although it is sometimes thought based on the X-ray morphology alone that the tail is pointing in the opposite direction to the merger motion, this is not necessarily the case. The information of the X-ray filamentary remnant from the cluster merger, together with the 2D WL shear data, provides constraints on the merger parameters, indicating an infalling velocity of approximately $1000\, {\rm km\, s^{-1}}$ and an impact parameter of $0.9$ Mpc.
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High Energy Astrophysical Phenomena
EUSO-SPB2 Cherenkov Telescope: Overview and First Neutrino Constraints
Tobias Heibges, Diksha Garg, Claire Guépin et al. (+5 more)
Earth-skimming tau
neutrinos with energies above $\sim 10$ PeV can convert to tau
leptons that decay in the atmosphere and initiate upward-going extensive air showers that generate optical Cherenkov signals. On a curtailed NASA balloon flight in May 2023, the Cherenkov
telescope (CT) on the Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) was launched and had a short flight at $\sim 30$ km altitude. With some time pointing below the Earth's limb, EUSO-SPB2 CT data allow searches for
neutrino events that yield optical flashes from the forward-beamed Cherenkov light. We present an overview of the CT and provide upper limits for the diffuse astrophysical
neutrino flux from flight data as a proof-of-principle demonstration. We also briefly describe how the methodology is extended to potential transient
neutrino point sources.
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All authors Tobias Heibges, Diksha Garg, Claire Guépin, Julia Burton-Heibges, John F. Krizmanic, Mary Hall Reno, Tonia M. Venters, Lawrence Wiencke
Earth and Planetary Astrophysics
A High-Precision Dynamical Model of Callisto: Incorporating Rotation Effects within Multi-Layer Internal Structure Models
Kai Huang, Yongzhang Yang, Yuhao Chen et al. (+2 more)
China is planing to launch the Tianwen-4 mission around the year 2030, with its aim being the exploration of Jupiter and its moon, Callisto. Within the realm of deep space exploration, the accuracy of ephemerides is of great importance. Current ephemerides employ a simplified rotation model for Callisto, which this study addresses by proposing a novel dynamical model. This model enhancesthe existing orbital dynamics by integrating Callisto's rotational motions influenced by gravitational torques from the Sun, Jupiter, and other Galilean moons within an inertial frame, capturing the intricate coupling between Callisto's orbital and rotational dynamics. The study establishes a full dynamical model by deriving analytical expressions for this coupling and developing an adjustment model for data fitting using precise orbit determination methods. Furthermore, the influence of
tidal effects on Callisto's motion is investigated, considering its multi-layered internal structure. Results demonstrate that the difference between the newly established full model and the model in current ephemerides is on the order of tens of meters. When calculating the impact of different internal structures of Callisto on its orbit, the influence of three-layered and two-layered structures is on the order of meters, suggesting that the development of a high-precision dynamical model requires additional constraints on the internal structure of Callisto. This research provides a novel alternative for a new generation of precise numerical ephemerides for Callisto. Additionally, these findings provide a testing platform for the data from the Tianwen-4 mission.
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All authors Kai Huang, Yongzhang Yang, Yuhao Chen, Yining Zhang, Yuqiang Li
Instrumentation and Methods for Astrophysics
PRIMA General Observer Science Book Volume 2
A. Moullet, D. Burgarella, T. Kataria et al. (+8 more)
The PRobe far-Infrared Mission for Astrophysics (PRIMA) mission concept is a proposed mission to NASA's Astrophysics Probe Explorer (APEX) call. The concept features a cryogenically cooled 1.8 m diameter
telescope, and is designed to carry two science instruments covering the 24 to 264 $\mu$m wavelength range: an imaging polarimeter (PRIMAger) and a spectrometer (FIRESS). The majority of PRIMA's time (75%) will be open to observations proposed by the community (General Observer science / GO), and all of data will be publicly available for archival research (Guest Investigator science / GI). Following up on the successful community engagement created by the first volume of the GO PRIMA Science Book (arXiv:2310.20572), Volume 2 gathers 120 new and updated contributed science cases which could be performed within the context of the PRIMA GO/GI program. This volume reflects the strong development of the community interest, awareness and involvement in PRIMA, and further develops how PRIMA's unprecedented capabilities can be leveraged for an impactful and innovative GO/GI program covering most areas of astrophysics and over 90% of the scientific questions and discovery areas in the Astro2020 decadal survey.
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All authors A. Moullet, D. Burgarella, T. Kataria, H. Beuther, C. Battersby, M. Cheng, T. Essinger-Hileman, H. Inami, E. Mills, T. Nagao, S. Unwin