Instrumentation and Methods for Astrophysics
White paper on the relevance of the European Solar Telescope (EST) for the French heliophysics
E. Pariat, Q. Noraz, B. Perri et al. (+61 more)
The project of the European
Solar Telescope aims to provide a state-of-the art infrastructure to study the Sun and its interactions with Earth and the heliosphere. This 4.2m aperture
telescope will be equipped with multi conjugate adaptive optics, light-polarisation analyser, imaging spectrograph and integral field unit spectrographs. It will provide unprecedented observations of the
solar photosphere and chromosphere and of the dynamical events and features that pertains to the low
solar atmosphere. The EST project is presently in a phase of crystallisation, aiming at the creation of an European Research Infrastructure Consortium. While the French community has continuously been associated with the development of the EST project, some specific scientific aspects are more particularly relevant for the French astrophysics and heliophysics communities. The present review highlights the scientific research axes of high interest from the French community that shall strongly benefit from EST. The later will not only advance numerous topics of
solar physics, as well as
solar adaptive optics developments, but will also provide unrivaled
datasets of high interest in the framework of space weather. This review also aims to highlight the space weather use that can be done with future EST observations, that will be particularly relevant for French heliophysicists.
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All authors E. Pariat, Q. Noraz, B. Perri, N. Poirier, C. Froment, L. Bigot, G. Aulanier, B. Gelly, J. Aboudarham, S. Aizawa, O. Alexandrova, S. Alqeeq, T. Amari, F. Auchère, G. Bernoux, M. Berthomier, V. Bommier, X. Bonnin, P. Boumier, A. S. Brun, I. Bualé, E. Buchlin, A. Canou P. Canu, T. Corbard, F. Cornu, C. Coustillet, G. Cozzani, L. D'herbomez, S. Diaz Castillo, T. Dudok de Wit, M. Faurobert, A. Finley, D. Fontaine, R. A. Garcia, R. Grappin, L. Hadid, K. H. Henadhira Arachchige, M. Janvier, L. Jouve, R. Kieokaew, H. Kirkwood, B. Lavraud, J.-P. Le Breton, O. Le Contel, N. Le Nestour, F. Leblanc, S. Masson, N. Meyer-Vernet, S. Parenti, F. Pitout, M. Rieutord, J. Romero Castañeda, A. Rouillard, C. Ruiz de Galarreta, F. Sahraoui, B. Schmieder, P. Simon, A. Strugarek, M. Tallon, P. Thepthong, J. Touresse, J.-C. Vial, N. Vilmer, A. Zaslavsky
High Energy Astrophysical Phenomena
Asteroseismology of neutron stars with both hyperons and $\Delta$ resonances
Hao Sun, Jia-Xing Niu, Yong Gao et al. (+2 more)
Employing various relativistic energy density functionals for nucleon-nucleon interactions, we investigate the impact of hyperons and $\Delta$ resonances on the frequencies of non-radial oscillations in
neutron stars, where the universal coupling scheme is adopted for the $\Delta$-
meson couplings. It is found that the inclusion of $\Delta$ resonances is essential for
neutron stars to accommodate the recent mass and radius measurements of PSR J0030+0451, PSR J0740+6620, PSR J0437-4715, PSR J0614-3329, and HESS J1731-347. As $\Delta$ resonances start to emerge in
neutron stars' inner core, the $g$-mode oscillation energy becomes concentrated within the $\Delta$-admixed region, leading to a sharp increase in the $g$-mode frequency. We also examine the $f$-mode and $p$-mode oscillations and find that the impact of $\Delta$ resonances on these modes is less pronounced than the $g$-modes. The oscillation frequencies calculated in the Cowling approximation are then compared with those from full general relativity, confirming that the Cowling approximation introduces an error of approximately 20% for the $f$-modes and within 10% for the $g$-modes. The notable effect of $\Delta$ resonances on
neutron stars' $g$-mode frequencies holds important implications for probing the internal composition of
neutron stars.
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All authors Hao Sun, Jia-Xing Niu, Yong Gao, Hong-Bo Li, Cheng-Jun Xia
High Energy Astrophysical Phenomena
EP251023a: A fast X-ray transient featuring a magnetar-powered optical internal plateau followed by a steep decay
Shuai-Qing Jiang, Dong Xu, Wei-Hua Lei et al. (+33 more)
EP251023a is an extragalactic fast X-ray transient (eFXT) detected solely by EP without a gamma-ray counterpart. The
prompt emission consists of a main emission with a duration $T_{90}=292\pm19$ s, followed by a long-lasting tail emission that persists until the observation ends at $T_0+1571$ s. With the upper limit of Konus–Wind, we derived a conservative upper limit on the isotropic gamma-ray energy $E_{\gamma,\rm{iso}}$ of $5.7 \times 10^{52}$ erg for the main emission phase. A
redshift of $z = 2.232\pm0.001$ is identified from strong absorption features in the Keck spectrum, which also indicate a relatively low host-
galaxy HI column density. Based on the broadband spectral energy distribution, the late-time light curves show an achromatic plateau, followed by an extremely steep decay with a slope of 3.99 after a break at about 49 ks, which is consistent with a rapidly spinning millisecond magnetar engine. Under the isotropic wind scenario, we obtain the initial period $P_0<2.27$~ms and the
magnetic field strength $B_p<8.33\times10^{14}$~G for the magnetar; whereas considering a jet collimation with a typical opening angle of 0.1 rad relaxes these constraints to $P_0<32.15$~ms and $B_p<1.18\times10^{16}$~G. Together with GRB\,070707, EP251023a may represent a rare class of optical magnetar-powered internal plateaus with little external-shock contamination, unlike previous examples detected primarily in X-rays. Future discoveries of similar events will help clarify the relationship between magnetar-powered internal emission observed in the optical band and that detected only in X-rays.
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All authors Shuai-Qing Jiang, Dong Xu, Wei-Hua Lei, Jie An, Yuan-Chuan Zou, Zi-Pei Zhu, Ryan Chornock, Dmitry Svinkin, Wen-Xiong Li, E. Fernández-García, Yue Wu, Wen-Da Zhang, Shao-Yu Fu, Xing Liu, Lin-Bo He, Moira Andrews, A. J. Castro-Tirado, Joseph R. Farah, Dmitry Frederiks, M. Gritsevich, D. Andrew Howell, Ding-Fang Hu, Alexandra L. Lysenko, A. Maury, Curtis McCully, S. B. Pandey, I. Pérez-García, Anna Ridnaia, Anastasia Tsvetkova, Mikhail Ulanov, S.-Y. Wu, Kathryn Wynn, D.-R. Xiong, Hao-Nan Yang, B.-B. Zhang, Tong Zhao
Solar and Stellar Astrophysics
Chinese Sunspot Drawings and Their Digitization-(VIII) Release of a Machine Readable Parameters Catalog
G.H. Lin and S. Liu
We present a systematically revised and manually verified digital catalog of historical sunspot drawing observations from Chinese observatories, encompassing sunspot number, sunspot group number, and sunspot area measurements. This represents an updated release of China's early sunspot drawings that have been utilized in numerous published studies over the years, with ongoing refinements and corrections progressively incorporated during the course of those studies and now consolidated through a systematic round of data revision aimed at improving internal consistency and usability for the broader research community. To facilitate scientific utilization, selected comparisons with international reference sunspot data are presented, focusing on relative sunspot numbers (RSN) and sunspot group numbers (GN) from Yunnan Observatory (YNO) and Purple Mountain Observatory (PMO), while sunspot area measurements are also included in this release but are not compared with international
datasets in the present work. For RSN, both raw and k-corrected values are analyzed; for GN, only raw counts are used as no dedicated correction factor exists in the Chinese records. The results demonstrate strong positive correlations, with correlation coefficients consistently exceeding 0.95 for all comparisons, confirming the reliability and scientific value of these historical records. Systematic differences are observed: raw YNO RSN values are systematically higher than SIDC by about 17.6%, while raw PMO RSN values are about 6.0% lower. After k-correction, YNO shifts to a 20.9% deficit, suggesting over-correction, while PMO remains lower with a 15.5% deficit. Notably, GN exhibits smaller systematic offsets (16.5% for YNO and 8.5% for PMO) and serves as a more robust index for long-term
solar cycle studies.
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Cosmology and Nongalactic Astrophysics
The large scale structure probes of dark energy
Pengjie Zhang and Shang Li
We present a brief review on the large scale structure (LSS) probes of dark energy. We cover probes that directly constrain dark energy such as
baryon acoustic oscillation,
redshift space distortion, weak
lensing and cluster number count. We also review auxiliary probes that mitigate systematics in dark energy constraints, such as the SZ effect to constrain baryonic effect and broadband
galaxy clustering to calibrate photometric
redshift. We demonstrate the synergy between these probes in delivering dark energy constraint of both high precision and high accuracy.
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Cosmology and Nongalactic Astrophysics
Extragalactic test of General Relativity with time-delay gravitational lenses
Wuzheng Guo, Shuo Cao, Qiumin Wang et al. (+4 more)
Strong gravitational
lensing, a key prediction of General Relativity (GR), offers a unique environment for examining alternative modified
gravity theories. In this Letter, we employ a model-independent approach to estimate the parameterized post-Newtonian parameter $\gamma_{\rm PPN}$ using the time-delay measurements from H0LiCOW strong
lensing systems. To minimize potential biases from cosmological models in testing GR, we use Gaussian Process regression (GPR) to reconstruct angular diameter distances ($D_{\rm A}$) from the newest
baryon acoustic oscillation (BAO) measurements, provided by the Dark Energy Spectroscopic Instrument (DESI) DR2 data. Based on the reconstructed angular diameter distances and four H0LiCOW lenses, we directly estimate the post-Newtonian parameter $\gamma_{\rm PPN}=0.93^{+0.16}_{-0.17}$ and the sound horizon scale $r_{\rm d}=136.36^{+5.14}_{-3.20}~{\rm Mpc}$. This is the first simultaneous measurement of $\gamma_{\rm PPN}$ and $r_{\rm d}$ without any assumptions about the contents of the universe or the theory of
gravity. In the new framework of distance ratio $D_{\Delta t}/D_{\rm l}$ which avoids the bias introduced by $r_{\rm d}$, the $\gamma_{\rm PPN}$ constraint can be further improved to $\gamma_{\rm PPN}=0.89^{+0.19}_{-0.15}$. Our results provide a direct test of GR at the extragalactic scale, which is well consistent with the prediction of GR within $1\sigma$.
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All authors Wuzheng Guo, Shuo Cao, Qiumin Wang, Yun Chen, Marek Biesiada, Tonghua Liu, Yujie Lian
Astrophysics of Galaxies
A comprehensive Gaia DR3 study of the open cluster NGC 6134: Bayesian distances, present-day mass function, mass segregation, and structural decomposition
Agus T. P. Jatmiko, Teduh Perhati, Dhimaz G. Ramadhan et al. (+7 more)
Open clusters are key laboratories for studying the formation and dynamical
evolution of
stellar populations. We present a comprehensive characterization of the intermediate-age open cluster NGC 6134 using
Gaia DR3 astrometry and photometry. Adopting the 890-member Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) membership catalog, we determine the cluster distance and individual member distances with the
Bayesian hierarchical code Kalkayotl under a King spatial prior, derive the fundamental parameters with the automated isochrone-fitting code ASteCA, quantify mass segregation, and decompose the projected spatial distribution into structural components. We obtain a
Bayesian cluster distance of $1070.8^{+21.0}_{-19.0}$ pc (mode and 68% credible interval), consistent with the ASteCA value ($d = 1064.4 \pm 15.2$ pc), with member distances peaking at $1071.2 \pm 2.5$ pc. ASteCA yields $\mathrm{[Fe/H]} = 0.08 \pm 0.06$, $\log(t) = 9.14 \pm 0.01$, and $A_\mathrm{V} = 1.03 \pm 0.05$ mag. The present-day mass function (PDMF) follows a broken power law with slopes $\Gamma_A = -2.10^{+0.10}_{-0.10}$ and $\Gamma_B = 1.59^{+0.14}_{-0.14}$ and break mass $M_c = 0.95^{+0.02}_{-0.02}\ M_\odot$, with a negative low-mass slope and a high-mass slope steeper than the canonical Salpeter value ($\Gamma = 1.35$), consistent with the preferential loss of the most massive
stars through
stellar evolution rather than with dynamical depletion. The observed mass segregation is consistent with an origin in long-term dynamical
evolution. The cluster comprises a core, a diffuse
halo, and a coherent plane-of-sky elongated feature that is unlikely to arise from noise based on a size-matched isotropic null test, and that lies beyond the radius at which masses are available. The observed main-sequence gap is closely linked to the cluster's binary fraction.
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All authors Agus T. P. Jatmiko, Teduh Perhati, Dhimaz G. Ramadhan, Muhammad Yusuf, Denny Mandey, Mochamad I. Arifyanto, Premana W. Premadi, Sahlan Ramadhan, Ferry Yap, Laksma Satya
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Low-mass X-ray binaries as a probe of Kerr-MOG black hole spacetime
Bakhodirkhon Saidov, Bakhtiyor Narzilloev, Ibrar Hussain et al. (+1 more)
We investigate the astrophysical implications of rotating black holes in modified
gravity by studying the Kerr-MOG spacetime and applying it to several
stellar-mass black hole candidates: A0620-00, H1743-322, XTE J1550-564, GRS1124-683, GRO J1655-40, and GRS1915+105. The Kerr-MOG geometry is characterized by the black hole mass, the
spin parameter $a$, and the modified
gravity parameter $\alpha$. We analyze how the presence of the MOG parameter modifies the spacetime structure and the location of the innermost stable circular orbit (ISCO). Within the Novikov–Thorne
accretion disk model, we show that $\alpha$ significantly affects the radiative efficiency of
accretion disks and introduces a degeneracy between the
spin and the modified
gravity parameter. Using observational estimates of radiative efficiencies inferred from the continuum-fitting method, we constrain the allowed regions in the $(a,\alpha)$ parameter space for each source. We further examine the relativistic jet power using the Blandford–Znajek mechanism and compare the theoretical predictions with the observed transient jet energetics, considering two representative jet Lorentz factors, $\Gamma=2$ and $\Gamma=5$. By combining the constraints from the radiative efficiency and jet power, we identify regions where both observables can be simultaneously reproduced. For several sources significant overlap regions appear, while for the highly spinning source GRS1915+105 the compatibility occurs only within a narrow range of Kerr–MOG parameters. These results suggest that the Kerr–MOG spacetime can provide a viable framework for interpreting the observed properties of several black hole X-ray binaries.
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All authors Bakhodirkhon Saidov, Bakhtiyor Narzilloev, Ibrar Hussain, Bobomurat Ahmedov
Cosmology and Nongalactic Astrophysics
Late-Time Oscillating Quintessence in Light of DESI
Jun-Qian Jiang, Mustafa A. Amin and Arman Shafieloo
Recent DESI
baryon acoustic oscillation measurements, especially when combined with Type Ia
supernova and CMB data, sharpen the case for possible low-
redshift dynamics in the dark energy sector. We study a simple and physically transparent realization of such dynamics: a quintessence field that is Hubble frozen for most of
cosmic history and starts to oscillate around its minimum recently (at a
redshift $z\approx 0.1$). This late onset of oscillations can occur in a broad class of models where the quintessence potentials have a shallow slope away from the minimum and steepen near it. This class of models can improve the fit relative to $\Lambda$CDM, with $\Delta\chi^2\simeq -9$, while remaining competitive with common phenomenological dark energy parameterizations with the same number of parameters. The preference is driven mainly by the background expansion history, and near the best-fit region the resonant growth of quintessence perturbations and the associated Integrated Sachs-Wolfe (ISW) contribution remain small. More precise low-
redshift distance measurements, together with late-time probes such as the ISW effect and
lensing, may help distinguish this oscillating quintessence scenario from other forms of late-time dark energy dynamics.
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Astrophysics of Galaxies
Jet-ISM Interaction and Multi-channel AGN Feedback in the Post-merger Galaxy 4C+29.30
Xiao Cao, Junfeng Wang, Yan-Mei Chen et al. (+5 more)
4C+29.30 is a post-merger
galaxy hosting a rejuvenated active
galactic nucleus (AGN) with a complex multi-scale
radio morphology, making it an ideal laboratory to study the interplay between different AGN feedback modes. We present a multi-wavelength analysis combining optical integral field spectroscopy (SDSS/MaNGA and CFHT/SITELLE) with
radio continuum imaging (VLASS) to map the ionized gas kinematics and ionization structure across the
galaxy. We uncover a
galaxy-scale, biconical ionized gas
outflow whose axis is misaligned by $\sim$26$^\circ$ from the
radio jet. This
outflow, characterized by broad line widths and Seyfert-like ionization, is mostly consistent with a radiatively driven wind from the central supermassive black hole, which is accreting at a relatively high Eddington ratio ($L_{\mathrm{bol}}/L_{\mathrm{Edd}} \gtrsim 0.1$). In contrast, the northern
radio lobe clearly drives localized gas acceleration and increased velocity dispersion, indicative of jet-driven shocks interacting with the interstellar medium, consistent with previous X-ray findings. The coexistence of a radiatively driven
galactic-scale
outflow and a distinct, misaligned
radio jet demonstrates that multiple AGN feedback channels can operate simultaneously within the same system, providing new evidence for the concurrent action of radiative and mechanical feedback.
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All authors Xiao Cao, Junfeng Wang, Yan-Mei Chen, Min Bao, Xiaoyu Xu, Chunyi Zhang, Taotao Fang, Jianfeng Wu
Instrumentation and Methods for Astrophysics
Widefield Spectroscopic Telescope (WST): coating strategy to achieve high optical throughput
Benoit Sassolas, Matthieu Coulon, Christophe Michel et al. (+4 more)
The Wide-field Spectroscopic
Telescope (WST) is a 12-m class facility designed for simultaneous wide-field multi-object and integral-field spectroscopy across 370-1600 nm, targeting a throughput above 83% its wide-field focus and 76% at its integral field one. Its 13 mirrors and 5 lenses require optimized coatings balancing feasibility, operational needs, and long-term durability. Large mirrors (>2 m) may use enhanced metallic coatings, such as the protected-silver solution from the Vera C. Rubin Observatory, achieving over 90% reflectivity in UV and above 99% in NIR. Smaller mirrors would use Nb2O5/SiO2 dielectric stacks, offering 99% reflectivity, tunable spectral response, and excellent stability. Coating the large lenses (up to 1.6 m) is challenging due to the ultra-broadband range, traditional multilayer antireflective coatings show limitations from manufacturing and incidence-angle effects. Graded-index AR coatings are being explored for superior performance across broad wavelengths and angles.
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All authors Benoit Sassolas, Matthieu Coulon, Christophe Michel, Laurent Pinard, Roland Bacon, Corentin Cudennec, Philippe Dierickx
Astrophysics of Galaxies
A First Measurement of Circumgalactic Dust Reddening from Only 4.6 deg$^2$ of the Rubin Observatory's Data Preview 1
John Franklin Crenshaw, Matthew McQuinn and Jessica K. Werk
We present the first measurement of circumgalactic
dust reddening from the Vera C. Rubin Observatory, using only 4.6 deg$^2$ of ComCam Data Preview 1 — roughly $0.03\%$ of the final LSST footprint. Using photometric
redshifts, we stack background-
galaxy colors around foreground-
galaxy positions and detect a chromatic reddening profile from $r_\perp \simeq 10$ kpc to $1$ Mpc. Interpreting average $E(g-z)$ with a Milky Way extinction curve, we find $A_V = (1.3 \pm 0.4) \times 10^{-1} (r_\perp / 20 \mathrm{kpc})^{-1.8 \pm 0.4}$ within $120$ kpc. The amplitude and radial dependence agree with earlier Sloan Digital Sky Survey (SDSS), KiDS, and Dark Energy Survey (DES) results despite the $\sim1000\times$ smaller survey area and a foreground sample extending 3–6 mag fainter and 1–2 dex lower in
stellar mass. The innermost 10–15 kpc bin reaches $A_V \simeq 0.3$ mag, comparable to high-latitude extinction through the Milky Way disk near the
solar circle; the steep power-law slope implies a
dust distribution that does not simply trace the
halo-gas profile. Splitting by rest-frame $g-r$ shows stronger extinction around red foreground
galaxies (rest-frame $g-r > 0.5$), although the blue subsample is too noisy to establish a significant color dependence. This red sample, with median
halo mass $5 \times 10^{11} M_\odot$, shows substantially more reddening within 50 kpc than previously measured around more massive LRGs and implies a
dust-to-
stellar-mass ratio of $\sim 2\%$, nearly saturating the
dust budget allowed by
stellar metal yields. These pathfinder data demonstrate LSST's promise for high-precision
galaxy–
dust measurements across
galaxy mass, environment, and
redshift.
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Astrophysics of Galaxies
Dual-disk galaxies and thermal states of circumgalactic medium
Masafumi Noguchi
Disk
galaxies often have dual-disk structures composed of thin disks and thick disks. Recent observations reveal that such duality is ubiquitous across broad
galaxy mass and
cosmic time. It is suggested that more massive
galaxies have smaller mass fractions of thick disks and undergo a transition from thick (or single) disk states to dual-disk states at earlier times. Previous studies suggest that the circumgalactic medium (CGM) in
halos above the critical mass is heated by the development of stable shocks and feedback from active
galactic nuclei. It has been argued that this thermal change of the CGM causes the transition of the
accretion of CGM from the fast cold mode to the slow hot mode driven by the radiative cooling of heated CGM. We consider here the hypothesis that the cold and hot modes promote the formation of thick and thin disks, respectively. Previous theoretical studies showed that this hypothesis explains the age and chemical bimodality of the Milky Way disk as well as the mass dependence of disk duality observed for local
galaxies. Using simple
galaxy evolution models, we show that this hypothesis also reproduces the thick-to-thin disk mass ratios observed for high-
redshift galaxies up to $z=2$. Earlier transition to dual disks in more massive
galaxies is explained as the outcome of earlier crossing of the critical
halo mass by more massive
halos. The caveat here is that this interpretation is not applicable to bulge-dominated
galaxies at the high-mass end because present models do not include
galaxy mergers, which likely act as the primary route to bulge formation. It should also be noted that the link between the disk duality and gas
accretion modes may be indirect and multiple processes may transform accreted material into different types of disks in real
galaxies.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics
A Novel Arm-Length Stabilization Scheme for Gravitational-Wave Detectors with AlGaAs/GaAs Coated Mirrors
Jian Liu, Juntao Pan, Carl Blair et al. (+7 more)
The arm length stabilisation system is employed in gravitational-wave detectors to reduce the velocity of the mirrors such that the arm cavities can be brought onto resonance in a controlled manner required to attain the detector operating point. For future upgrades of current gravitational wave detectors such as A#, which will incorporate AlGaAs/GaAs coatings, the current frequency-doubled arm length stabilisation system is unsuitable due to excessive absorption of the frequency-doubled 532nm beam by the AlGaAs/GaAs coating. We propose a novel multi-wavelength arm length stabilisation scheme that uses both frequency-doubled and frequency-tripled beams. The 1596nm auxiliary locking beam is outside the absorption bands of AlGaAs/GaAs coating. It is frequencytripled to 532nm and phase-locked with the 1064nm science
laser through its second harmonic at 532 nm. In a tabletop setup, we experimentally demonstrated the stable cavity detuning and robust cavity locking transition by controlling the 1596nm
laser and 1064nm
laser phase locked loop. This demonstration confirmed that the proposed novel arm length stabilisation scheme is compatible with future upgrades or third-generation gravitational wave detectors that use AlGaAs/GaAs-coated test masses.
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All authors Jian Liu, Juntao Pan, Carl Blair, Chiara Di Fronzo, Li Ju, Chunnong Zhao, Sheon S. Y. Chua, Bram J. J. Slagmolen, Nutsinee Kijbunchoo, David Ottaway
Cosmology and Nongalactic Astrophysics
CHEX-MATE: AMALGAM weak-lensing analysis of 41 Planck Sunyaev-Zel'dovich-selected galaxy clusters
Keiichi Umetsu, Raphael Gavazzi, Mauro Sereno et al. (+20 more)
We present a weak-
lensing shear analysis of 41 Planck SZ-selected
galaxy clusters at $0.11\le z\le 0.55$ from the CHEX-MATE sample, using wide-field Subaru/Suprime-Cam and CFHT/MegaPrime imaging from the AMALGAM project. We detect the azimuthally averaged weak-
lensing signal around the X-ray peak of each cluster, achieving a median S/N of 6.5 per cluster. The $45^\circ$-rotated component has a median S/N of -0.1 and ranges from -1.8 to +1.8, consistent with zero. We model the excess surface mass density profile of each cluster with an NFW profile to infer weak-
lensing mass and concentration constraints. The total systematic uncertainty in the weak-
lensing mass calibration is assessed to be $8\%$. Using a hierarchical
Bayesian framework, we then derive weak-
lensing-calibrated scaling relations for the
halo concentration, $c_{200}$, as a function of $M_{200}$ and
redshift, and for the Planck SZ mass proxy, $M_{SZ}$, as a function of $M_{500}$ and
redshift, while accounting for sample selection effects, weak-
lensing modelling biases, and residual calibration uncertainty. At $M_{200}=10^{15}M_\odot$ and $z=0.25$, we find $c_{200}=3.53\pm0.71$ with an intrinsic scatter of $0.22\pm0.04$ dex. The inferred normalisation and scatter are consistent with recent $\Lambda$CDM predictions for massive
haloes, with no significant mass or
redshift dependence over the probed range. For the Planck mass proxy, our baseline regression yields $M_{SZ}/M_{500}=0.83\pm0.09$ at $M_{500}=7\times10^{14}M_\odot$ and $z=0.25$, with an intrinsic scatter of $0.10\pm0.02$ dex. A restricted model with fixed unit mass slope and no
redshift evolution gives $1-b=0.72\pm0.11$. We also provide weak-
lensing-calibrated posterior estimates of $M_{500}$ for the sample based on the baseline $M_{SZ}$–$M_{500}$–$z$ relation. These results provide an initial weak-
lensing mass calibration for CHEX-MATE multi-probe cluster studies.
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All authors Keiichi Umetsu, Raphael Gavazzi, Mauro Sereno, Nobuhiro Okabe, Emmanuel Bertin, Gianluca Castignani, Stefano Ettori, Fabio Gastaldello, Carlo Giocoli, Scott T. Kay, Junhan Kim, Maggie Lieu, Lorenzo Lovisari, Ben J. Maughan, Mario Nonino, Lorenzo Pizzuti, Etienne Pointecouteau, Gabriel W. Pratt, Mario Radovich, Elena Rasia, Mariachiara Rossetti, Harshda Saxena, Jack Sayers
Earth and Planetary Astrophysics
Bayesian analysis of Gaia epoch astrometry and radial velocities with kima
Thomas A. Baycroft, João P. Faria and Jean-Baptiste Delisle
Context. The next data release from the
Gaia space
telescope is expected to result in tens of thousands of newly detected
exoplanets, as well as detection and 3D orbital constraints on binary
stars and even black holes. Many of these will warrant in-depth analyses of the astrometric data, as well as radial velocity follow-up. This will require dedicated tools to exploit this wealth of data. Aims. We provide open-source software to analyse epoch astrometric data from
Gaia, both alone and simultaneously with radial velocities. Methods. We add two models to the open-source orbit-fitting codebase kima, and test these on both real an simulated data. This code uses diffusive nested sampling to explore the parameter space, calculate evidences for model comparison, and perform parameter estimation. Results. We show that the results obtained are consistent with published/expected values, validating the use of kima for analysis of
Gaia data. We explore various attributes of kima's
Gaia model including using it to potentially distinguish true orbits from scan-angle dependent signals.
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Cosmology and Nongalactic Astrophysics
Minimal Extensions of the $\alpha$-Starobinsky Model: Reconciling ACT DR6 and Reheating Constraints
Nehla Shobcha, Norma Sidik Risdianto and Romy Hanang Setya Budhi
The latest combined data from the Atacama Cosmology
Telescope (ACT) DR6, Planck, and DESI yields a scalar spectral index $n_s = 0.9743 \pm 0.0034$, which lies approximately $2\sigma$ above the prediction of the standard $\alpha$-Starobinsky inflation model. To address this tension, we propose two minimal extensions that preserve the model's plateau structure and attractor properties: a multiplicative exponential modification and an additive
polynomial deformation, both governed by a single small perturbative parameter $\delta>0$. We analytically derive the slow-roll parameters and inflationary observables up to second order in $\delta$ and integrate them with reheating dynamics via the consistency equation. It is shown that the $\delta$ term effectively shifts $n_s$ into the $1\sigma$ confidence region of the joint P-ACT-LB-BK18
dataset without violating the tensor-to-scalar ratio bound ($r < 0.038$). The viable parameter space at $1\sigma$ requires $\alpha \lesssim 35$ with $\delta \sim \mathcal{O}(10^{-2})$ for the exponential model, while the additive model requires $\delta \sim \mathcal{O}(10^{-3})$ for $p=1$ and $\delta \sim \mathcal{O}(10^{-4})$ for $p=2$. For the e-folding range $N_k \in [50, 65]$, the relevant reheating equation of state is $0<\omega_{\mathrm{re}}\le1$. All viable scenarios yield a reheating temperature $T_{\mathrm{re}} \sim 10^9$ GeV, which is safely above the Big Bang Nucleosynthesis (BBN) bound and below the gravitino overproduction limit.
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Instrumentation and Methods for Astrophysics
Improving Radio Source Count Estimation Using Kernel Density Estimation
Luozhenhan Liu, Zunli Yuan, Wenjie Wang et al. (+1 more)
Radio source counts provide a fundamental census of
cosmic radio emission, yet their estimation is usually based on coarse histograms that suffer from bin-choice bias, boundary effects, and survey incompleteness. We apply and rigorously evaluate kernel density estimation (KDE) as a anonparametric alternative to the conventional binned method for estimating differential
radio source counts. Using simulated flux-limited samples derived from an input luminosity function model, we compare the performance of standard KDE, adaptive KDE, and traditional binning methods. Our results show that KDE-based approaches yield more accurate and stable estimates, particularly in the high-flux regime where data are sparse and conventional methods struggle. We also apply the adaptive KDE method to real observational data from the LOFAR Two-Metre Sky Survey Deep Fields. Our analysis robustly confirms the pronounced “drop and bump" feature at sub-mJy flux densities, but also reveals that a secondary, modest bump seen in the binned data at ~ $\sim 10$ mJy is likely a binning artifact. We also demonstrate the flexibility of KDE in addressing observational incompleteness through weighted estimation, which applies weights continuously at the level of individual sources rather than averaging them in discrete bins. These strengths make KDE a powerful tool for source-count analyses in current and future
radio surveys and, more broadly, in analogous studies at other wavelengths. All computations in this study are implemented with AstroKDE, a Python package we have developed for astronomical applications.
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All authors Luozhenhan Liu, Zunli Yuan, Wenjie Wang, Chuanqi Li
Solar and Stellar Astrophysics
Kepler Image-Subtracted Light Curves and Variable Star Catalog of NGC 6819
Melinda Soares-Furtado, Rianna Kuenzi, Rachel Lee McClure et al. (+11 more)
Variable
stars in open clusters are valuable probes of
stellar evolution. They provide precise measurements of
stellar properties, constrain cluster ages and distances, and trace the angular momentum
evolution of
stellar populations. To advance these studies, we applied image subtraction and systematic reduction techniques to the NGC 6819 Kepler superstamp time-series data (Quarters 1-16), using the
Gaia DR3 catalog to identify the positions of individual sources. We produce 81,498 high-precision light curves for 11,055 sources in the crowded field harboring the 2.5 Gyr open cluster NGC 6819. Our detrended light curves achieve a best root-mean-square precision of 33 ppm (6.5-hour bins) for
stars with Kepler magnitudes 12 - 12.5 mag, falling to 79 ppm at 14 - 14.5 mag. Using
Gaia DR3 proper motions, and parallaxes, we distinguished likely cluster members from field
stars. We identified and classified 87 periodic variables that are potential members of NGC 6819, including 26 newly-discovered variables. We make our light curves and variable classifications publicly available to enable further studies of
stellar variability and angular momentum
evolution in this intermediate-aged open cluster.
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All authors Melinda Soares-Furtado, Rianna Kuenzi, Rachel Lee McClure, Nicholas T. Marston, Evan Linck, Robert D. Mathieu, Andrew Vanderburg, Joel D. Hartman, Kyle Cudworth, Robert Gagliano, Thomas Jacobs, Martti H. Kristiansen, Mark Omohundro, Hans Martin Schwengeler
Cosmology and Nongalactic Astrophysics
Constant-Roll Inflation: Analytical Formulae for Power Spectrum and Implications for Induced Gravitational Waves
Hayato Motohashi, Shi Pi, Yuichiro Tada et al. (+1 more)
Constant-roll inflation provides a simple and analytically tractable framework for describing transient departures from slow roll, including non-attractor phases that can enhance the
primordial curvature perturbation on small scales. In this work, we investigate the
curvature power spectrum generated in a slow-roll–constant-roll–slow-roll scenario, focusing on the positions and amplitudes of the two characteristic peaks associated with the two transitions. We show that, in the parameter range where both peaks are well separated and sufficiently pronounced, the underlying constant-roll parameters can be reconstructed from the peak positions and amplitudes without performing a brute-force parameter scan. In addition, we construct a smoothed analytic approximation to the power spectrum, designed for efficient estimates of scalar-induced gravitational waves and related phenomenological applications.
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All authors Hayato Motohashi, Shi Pi, Yuichiro Tada, Jianing Wang
Astrophysics of Galaxies
Radial gradients revealed by mutliscale outflows from down-the-barrel spectroscopy toward a quasar at redshift 3.4
Weimin Yi, Paola Rodriguez Hidalgo, Chen Chen et al. (+9 more)
Active
galactic nucleus(AGN) feedback is a key ingredient in
galaxy formation models and simulations. From an observational point of view, however, the channels of AGN feedback coupling to the interstellar medium (ISM) and circumgalactic medium (CGM) and hence the impact on
galaxy evolution, are largely uncertain and remain fiercely debated, due primarily to the huge gap from
nuclear to CGM scales. Here we present multi-epoch, down-the-barrel spectroscopy toward a luminous
quasar at $z=3.409$ over two decades, which reveals multiscale
outflows expanding from
nuclear to CGM scales along with characteristic radial gradients. Most strikingly, the trends of trough depth across three different-scale, freely expanding
outflows are opposite between N V and C IV, regardless of the spectral normalization and short-term variability, leading to a tenable gradient of N/C and signaling a critical transition from ejective feedback on small scales to regulative feedback on large scales. Our observations of this
quasar offer valuable diagnostics to explore the realistic wind-ISM/CGM coupling, one of the most challenging tasks in state-of-the-art simulations of feedback.
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All authors Weimin Yi, Paola Rodriguez Hidalgo, Chen Chen, P. B. Hall, Zhicheng He, R. P. Easton, D. P. Schneider, W. N. Brandt, Xue-Bing Wu, Kai-Xing Lu, Chuanjun Wang, Yuanjie Feng
Cosmology and Nongalactic Astrophysics
Universal Fitting Formulae for the Peak Concentration of Dark Matter Halos
Dao-zhou Wang, Weipeng Lin and Tian-Cheng Luan
The prediction of the structural properties of dark matter
halos is crucial for studies in modern cosmology and
galaxy formation. Utilizing a comprehensive suite of N-body simulations spanning diverse cosmologies and box sizes, we derive a universal
halo concentration prescription aligned with the excursion set theory framework. The
halo peak-height parameter is revised to incorporate the linear growth factor at the
halo formation epoch, enhancing its physical relevance to assembly history tracking. For fixed
halo mass, we fit the distributions of the
halo concentration and revised peak height to lognormal functions to extract their peak values. We find that these peaks follow a universal, tight relation invariant to
redshift, box size, initial power spectrum, and cosmology, exhibiting remarkably small scatter. In particular, the relation flattens systematically with increasing revised peak height, approaching an asymptotic value of ~2.54, consistent with previous reports of a concentration floor. The fitting formula consistently describes both the mass-concentration and peak height-concentration relations, easily quantifying how these relations depend on
redshift and cosmological parameters. This universal framework enables robust prediction of the most probable (peak)
halo concentration using our fitting formula or theoretical/semianalytical mass assembly histories. A software package for calculating peak concentrations is publicly available online.
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High Energy Astrophysical Phenomena
Radio eclipse of the slowest spinning Galactic-field spider pulsar PSR J1932+2121 and its X-ray emission prospect
Ze-Xin Du, Yun-Wei Yu, Zong-Lin Yang et al. (+5 more)
PSR J1932$+$2121 is a newly discovered spider
pulsar with a pronounced
radio eclipse identified by the Five-hundred-meter Aperture Spherical
radio Telescope (FAST); it provides an ideal laboratory for studying the eclipse mechanism and high-energy emission from its intrabinary shock (IBS). By modeling the orbital-phase-dependent dispersion measure variations and flux profiles during the eclipse region with the wind interaction and IBS geometry, we constrain the system to a nearly edge-on inclination ($i_{\mathrm{o}} \simeq 88.55^{\circ}$) and a weak
stellar wind from a low-mass main-sequence companion. Our analysis of the eclipse mechanism suggests that synchrotron absorption by nonthermal electrons can reproduce the observed flux variations with reasonable parameters for the eclipsing medium. We further predict the synchrotron emission from the IBS in PSR J1932$+$2121, showing that its X-ray flux, particularly near the inferior conjunction of the companion
star, could be detectable with XMM/EPIC, EP/FXT, or eXTP/SFA and should exhibit double-peaked orbital modulation by Doppler boosting. These results provide a theoretical framework for understanding this system and for guiding future multiwavelength probes of spider
pulsars.
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All authors Ze-Xin Du, Yun-Wei Yu, Zong-Lin Yang, Aming Chen, Peng-Fei Wang, Jin-Lin Han, De-Jiang Zhou, Xiao-Peng You
Cosmology and Nongalactic Astrophysics
Probing Baryonic Feedback Effect with CSST Weak Lensing and Future FRB Measurements
Shuai Feng, Yan Gong, Qi Xiong et al. (+4 more)
We explore the joint probe on the baryonic feedback effect using the weak
lensing measurement from the upcoming Chinese Space-station Survey
Telescope (CSST) photometric survey and the dispersion measure (DM) statistics of the fast
radio bursts (FRBs) from next-generation
radio telescopes, i.e., the Square Kilometre Array (SKA) and the Deep Synoptic Array (DSA-2000). By employing the baryonic
halo model, we compute the matter, electron, and matter–electron power spectra, and generate mock data considering realistic noise and systematic effects based on the designs of the
telescopes. These mock data are then analyzed using the Markov Chain Monte Carlo (MCMC) method to investigate the parameter constraints. We find that CSST weak
lensing alone can constrain the baryonic feedback parameter $\log_{10} T_{\text{AGN}}$ to an accuracy of $3.1\%$, with the sum of
neutrino mass bound $\sum m_{\nu} < 0.53\,\mathrm{eV}$. When performing the $3\times2 \,\mathrm{pt}(e,\mathrm{m})$ analysis, the inclusion of FRB DM measurements can significantly improve the precision of $\log_{10} T_{\text{AGN}}$ to $0.4\%$, and will lead to a better constraint on $\sum m_{\nu}$ with an upper limit $< 0.47\,\mathrm{eV}$ by effectively breaking the degeneracy. Our results demonstrate that the joint observation of future FRB DM and weak
lensing surveys is a powerful tool for probing the baryonic feedback effect, which is helpful in obtaining robust constraints on the
neutrino mass and other important cosmological parameters.
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All authors Shuai Feng, Yan Gong, Qi Xiong, Xiaohui Liu, Hengjie Lin, Dingao Hu, Xuelei Chen
Astrophysics of Galaxies
The MASSIVE SURVEY XXI: Local Variations in the Stellar Initial Mass Function of MASSIVE Early-Type Galaxies
Meng Gu, Jenny E. Greene, Andrew B. Newman et al. (+2 more)
Extensive evidence suggests that the
stellar initial mass function (IMF) varies among early-type
galaxies (ETGs), but spatially resolved studies within individual
galaxies are limited in sample size. We investigate radial variations in the low-mass ($\leq1M_{\odot}$) IMF and its connection to
stellar populations in 37 nearby massive ETGs from the MASSIVE survey. Using high-quality Magellan/LDSS-3 long-slit spectroscopy spanning $0.4\mu$m$-1.01\mu$m, we extract spectra in radial bins reaching outermost radii of 0.2-1.1Re across the sample. We find that the IMF becomes less bottom-heavy with increasing radius in most
galaxies. The sample-averaged IMF mismatch parameter, $\alpha_{\rm IMF}=(M/L)/(M/L)_{\rm Kroupa}$, decreases from 2.16 within Re/8 to 1.74 in the Re/4-Re/2 bin, with
galaxy-to-
galaxy scatters of 0.50 and 0.42, respectively. Thus, the average IMF remains more bottom-heavy than Kroupa and approximately Salpeter-like or more bottom-heavy over these radii. The radial gradients of $\log(\alpha_{\rm IMF})$ anti-correlate with the central value of $\alpha_{\rm IMF}$, indicating that
galaxies with more bottom-heavy central IMFs decline more steeply toward less bottom-heavy, approximately Salpeter-like values at larger radii. We find mild positive local correlations between $\alpha_{\rm IMF}$ and
stellar metallicity, but no significant local correlation with [Mg/Fe] or [Na/Fe]. Together with the approximately flat profiles of several [$\alpha$/Fe], this suggests that IMF variation in massive ETGs is more closely linked to
metallicity than to the
star-formation timescale traced by [$\alpha$/Fe]. Finally, the radial variation in
stellar $M/L_r$ is dominated by the IMF gradient rather than by the
stellar-population gradient. A fixed Kroupa IMF underestimates
stellar masses by factors of 1.7 and 1.5 within Re/2 and Re in massive ETGs.
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All authors Meng Gu, Jenny E. Greene, Andrew B. Newman, Chung-Pei Ma, John P. Blakeslee
Instrumentation and Methods for Astrophysics
Carruthers Data Processing Pipeline: Photon Background Removal
Alex Zhang, Heather Filippini, Jackson Craig et al. (+4 more)
The Carruthers Geocorona Observatory, launched in September 2025, is NASA's first mission devoted to investigating the fundamental nature of Earth's exosphere from its distant vantage in
halo orbit around the Earth-Sun Lagrange 1 (L1) point. Its primary payload, the GeoCoronal Imager, consists of two coaligned photometric imagers that measure ultraviolet Lyman-alpha emission radiance from exospheric hydrogen simultaneously at wide- and narrow- fields of view. These observations will map the exosphere's global spatial structure and observe its temporal variability in response to geomagnetic storms. However, a critical step in that analysis is isolating the in-band exospheric hydrogen Lyman-alpha signal from any other source of
photons, including in-band InterPlanetary Hydrogen
photon background and out-of-band
photon backgrounds, which are emitted from Earth's limb. This paper details the
algorithms used to retrieve and remove
photon backgrounds from the GCI science images acquired on-orbit. Finally, the science data processing pipeline that transforms instrument-effect corrected images (L1B science data product) into absolutely-calibrated exospheric H measurements in physical units (L1C science data product) is detailed. Evaluation of
algorithm performance based on a realistic pre-flight case study using synthetic data demonstrates that these
photon background removal
algorithms achieve high accuracy, leaving a residual systematic bias in isolated exospheric Lyman-alpha of only 3% under beginning-of-life conditions.
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All authors Alex Zhang, Heather Filippini, Jackson Craig, Lara Waldrop, John Clarke, Farzad Kamalabadi, Pratik Joshi
Earth and Planetary Astrophysics
Micron-Scale Technosignatures: How a Cubic Metre of Lunar Regolith May Begin to Constrain the Number of Past Technological Civilisations in the Galaxy
Lewis J. Pinault, Brian C. Lacki, Ian A. Crawford et al. (+1 more)
Building on Arkhipov's proposal that technogenic artefacts may survive natural interstellar transport and accumulate on
Solar System surfaces, we examine the prospects for identifying micron-scale engineered particulate material within the lunar regolith. We analyse the transport of micron and submicron grains through the interstellar medium, including gas drag, sputtering, and ISM phase-dependent survival, and show that refractory particles with characteristic radii of order 0.3 microns may traverse kiloparsec scales over residence times of 0.1-1 Gyr.
Solar radiation pressure and heliospheric filtering define a dynamically constrained slow-arrival channel in which a small fraction of grains reach the Earth-Moon system at relative velocities compatible with survival upon impact. Combining these properties with regolith-mixing constraints yields quantitative upper limits on the cumulative undirected technomaterial output of large-scale spacefaring civilisations: a null detection in a cubic metre of regolith excludes scenarios in which
Solar-type
stars typically disperse more than approximately 0.10 Earth mass equivalents of long-lived artificial particulate debris over
Galactic history. Deliberate targeting of the inner
Solar System with artificial particulate matter defines a complementary regime characterised by the visitation frequency and deposited mass of such releases, for which the probabilities of detection may be orders of magnitude higher. We outline a multi-modal detection strategy integrating machine-
vision triage with laboratory forensic techniques to identify anomalous grains within a well-characterised natural background. Particulate technosignatures thus establish an experimentally accessible form of exo-archaeology, capable of placing meaningful constraints – and, in favourable cases, yielding direct material evidence – of the
Galaxy's technological history.
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All authors Lewis J. Pinault, Brian C. Lacki, Ian A. Crawford, Andrew P. V. Siemion