Solar and Stellar Astrophysics
Characterizing the Low-Mass Pre-Main-Sequence Population in the Low-Metallicity Star-Forming Region Dolidze 25 Using VLT-MUSE
Mizna Ashraf, Jessy Jose, Gregory J. Herczeg et al. (+6 more)
The
metallicity of the
star-forming environment is a fundamental parameter shaping the
evolution of protoplanetary disks and the formation of planetary systems, yet its influence remains poorly constrained. We present a spectroscopic study of low-mass pre-main sequence (PMS)
stars ($M < 1 \, M_\odot$) in the exceptionally metal-poor cluster Dolidze~25 ($Z \approx 0.2 \, Z_\odot$), using VLT/MUSE observations to probe
accretion processes and disk
evolution in a subsolar environment. We identify 132 cluster members using a combination of
Gaia astrometry and spectroscopic youth indicators, including lithium absorption and Balmer emission. The
stellar parameters are derived using low-
metallicity BT-Settl models yielding effective temperatures, extinctions, luminosities enabling robust estimates of
stellar masses and ages. Mass
accretion rates ($\dot{M}_\mathrm{acc}$) derived from H$\alpha$ emission span $10^{-10}$–$10^{-8} \, M_\odot\,\mathrm{yr}^{-1}$ with a median value of \(8 \times 10^{-10}\,M_\odot\,\mathrm{yr}^{-1}\). These rates are comparable to those in
solar-
metallicity regions of similar age, such as Lupus and Orion, indicating minimal
metallicity dependence in
accretion processes. Our analysis shows that using
solar-
metallicity templates to fit low-
metallicity stars leads to systematic overestimations of \(T_\mathrm{eff}\) (by approximately \(300\,\mathrm{K}\)) and \(A_V\) (by around \(0.5\,\mathrm{mag}\)), underscoring the importance of employing
metallicity-matched models for reliable characterization in low-\(Z\) environments. We present flux-calibrated, extinction-corrected spectra of these metal-poor PMS
stars as a valuable resource for future investigations of disk
evolution in subsolar regimes.
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All authors Mizna Ashraf, Jessy Jose, Gregory J. Herczeg, Min Fang, Varsha Ramachandran, Carlo F. Manara, Christian Schneider, Megan Reiter, Kiran Kumar Sunil
Solar and Stellar Astrophysics
Connections between the cycle-to-cycle light curve and O-C variations of the Blazhko RR Lyrae stars
József M. Benkő
Recent studies have shown that the irregular O-C variations observed in many non-Blazhko RR Lyrae
stars may result from random, cycle-to-cycle (C2C) variations in their light curves. However, centuries-long data series reveal that the O-C diagrams of Blazhko
stars exhibit particularly large-amplitude, irregular variations. In this Letter, we extend the previous investigation of non-Blazhko
stars to Kepler Blazhko
stars to explore the role of C2C variations in the O-C diagrams. We derived the O-C diagrams from Kepler space
telescope light curves using a precise template-fitting method. Based on their
Fourier analyses, we also constructed residual O-C diagrams that were pre-whitened for frequencies associated with the Blazhko effect. We then fitted the same statistical models to both types of O-Cs that we had previously applied to non-Blazhko
stars. The optimal statistical model includes the C2C variation for 74% of the O-C curves in our Blazhko sample, and the parameter describing the strength of the C2C variation is significantly larger than that obtained for non-Blazhko
stars. This may explain the strong irregular O-C variations previously observed in Blazhko
stars. Furthermore, we found a strong positive correlation between the C2C variation strength and the amplitude of the frequency-modulation component of the Blazhko effect, indicating a connection between the two phenomena.
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Earth and Planetary Astrophysics
The GAPS programme at TNG LXX. HD 128717 B/Gaia-6 B: a long-period eccentric low-mass brown dwarf from astrometry and radial velocities
M. Pinamonti, A. Sozzetti, D. Barbato et al. (+24 more)
The transition regime between
giant planets (GPs) and brown
dwarfs (BDs) is still an open subject of study in exoplanetary science. A complete understanding of the population of long-period GPs and BDs would be pivotal in understanding this topic, but the number of such objects with precisely measured orbital and physical parameters is still small. Moreover, their dynamical influence on smaller companions in inner orbits is still unclear. Within the GAPS programme, we aim to confirm and characterize sub-
stellar companion candidates from
Gaia DR3, and to study the potential presence of additional lower-mass
planets in their systems. We present the results of an intensive high-precision RV monitoring of HD 128717, which hosts the astrometric candidate
Gaia-ASOI-009. We used the HARPS-N spectrograph at TNG to collect a high-cadence RV time series of the target. We used MCMC analyses to refine the
Gaia DR3 orbital solution of the companion and, finally, performed a combined model of RV and proper motion anomaly (PMa) to derive the complete 3-D orbit of the companion. We also ran a suite of numerical simulations to confirm our results. We confirm the sub-
stellar nature of
Gaia-ASOI-009, i.e.
Gaia-6 B: from the combined RV+PMa fit, we confirm that it is a high-eccentricity low-mass brown
dwarf with $P_\text{B} = 9.37^{+0.06}_{-0.05}$ yr, $M_\text{B} = 19.8 \pm 0.5$ $M_\text{J}$, $e_\text{B}=0.85$, $i_\text{B} = 130^{\circ}$. The derived orbital solution differs significantly from the one published in
Gaia DR3. Through a series of dedicated simulations, we demonstrate that this discrepancy arises from a degeneracy in the
Gaia DR3 astrometric solution. Specifically, the combination of
Gaia-6 B long orbital period and high eccentricity, both poorly constrained by the limited timespan of DR3, led to an incorrect solution characterized by a shorter period and lower eccentricity.
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All authors M. Pinamonti, A. Sozzetti, D. Barbato, S. Desidera, K. Biazzo, A. S. Bonomo, A. F. Lanza, L. Naponiello, L. Affer, R. M. Anche, G. Andreuzzi, M. Basilicata, M. Brinjikji, M. Brogi, L. Cabona, E. Carolo, S. Colombo, M. Damasso, M. D'Arpa, S. Di Filippo, A. Harutyunyan, J. Hom, L. Mancini, G. Mantovan, D. Nardiello, K. K. R. Santhakumari, T. Zingales
Astrophysics of Galaxies
The dynamical memory of tidal stellar streams: Joint inference of the Galactic potential and the progenitor of GD-1 with flow matching
Giuseppe Viterbo and Tobias Buck
Stellar streams offer one of the most sensitive probes of the Milky Way`s gravitational potential, as their phase-space morphology encodes both the
tidal field of the host
galaxy and the internal structure of their progenitors. In this work, we introduce a framework that leverages Flow Matching and Simulation-Based Inference (SBI) to jointly infer the parameters of the GD-1 progenitor and the global properties of the Milky Way potential. Our aim is to move beyond traditional techniques (e.g. orbit-fitting and action-angle methods) by constructing a fully
Bayesian, likelihood-free posterior over both host-
galaxy parameters and progenitor properties, thereby capturing the intrinsic coupling between
tidal stripping dynamics and the underlying potential. To achieve this, we generate a large suite of mock GD-1-like streams using our differentiable N-body code \textsc{Odisseo}, sampling self-consistent initial conditions from a Plummer sphere and evolving them in a flexible Milky Way potential model. We then apply conditional Flow Matching to learn the vector field that transports a base Gaussian distribution into the posterior, enabling efficient, amortized inference directly from stream phase-space data. We demonstrate that our method successfully recovers the true parameters of a fiducial GD-1 simulation, producing well-calibrated posteriors and accurately reproducing parameter degeneracies arising from progenitor-host interactions. Flow Matching provides a powerful, flexible framework for
Galactic Archaeology. Our approach enables joint inference on progenitor and
Galactic parameters, capturing complex dependencies that are difficult to model with classical likelihood-based methods.
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High Energy Astrophysical Phenomena
The role of distant pulsars in the detectability of continuous gravitational waves
Kathrin Grunthal, Nataliya Porayko, David J. Champion et al. (+1 more)
One of the imminent science goals of
pulsar timing arrays (PTAs) is the detection of a continuous gravitational wave (CGW) emitted by an individual supermassive black hole binary (SMBHB). SMBHBs that cause CGWs with GW frequencies $f_\mathrm{GW} > 10 \text{nHz}$ have undergone significant orbital
evolution, hence a change of $f_\mathrm{GW}$ over time. In PTA data sets with sufficiently long observational time span, this means that the Earth and
pulsar terms' contributions to the CGW signal signature can eventually become resolvable. Since the
pulsar term is accumulated incoherently and thus often treated as an additional source of noise, this separation can prove to be beneficial for the detection of the CGW signal in the PTA data set. We aim to investigate to what extent resolvable Earth and
pulsar terms affect currently used techniques for CGW searches with PTA data sets, that treat the
pulsar term as an additional source noise. We focus on the dependency of the
pulsar term frequencies on the
pulsar's distance. We aim to answer the question of whether adding more distant
pulsars to a PTA data set can mitigate biases and improve the detection of CGWs. We show that under ideal conditions, more distant
pulsars can facilitate the CGW search with PTA data sets.
Bayesian parameter estimation is yielding better parameter constraints and the frequentist per-frequentist optimal statistic search becomes more stable. However, using the realistic data set simulations, it was found that other configuration parameters of a PTA, such as the anisotropic distribution of
pulsars and the effective number of
pulsars in a PTA, can play a crucial role to the importance of this effect.
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All authors Kathrin Grunthal, Nataliya Porayko, David J. Champion, Michael Kramer
Astrophysics of Galaxies
Investigating the H i mass-size relation using the Simba cosmological simulations
Omphile Rabyang and Ed Elson
Observational studies have established a remarkably tight power-law relationship between the H I masses and sizes of late-type
galaxies, known as the H I mass-size relation. This relation has been shown to persist across various models of a
galaxy's H I surface density profile. Using the Simba cosmological simulations, we investigate the robustness of this relation under different feedback prescriptions, including cases where specific feedback mechanisms are absent. While the global properties of
galaxies are significantly affected by changes in feedback, the H I mass-size relation remains intact. Moreover, its parameters consistently align with the best available empirical measurements. We analyze the H I mass distributions of
galaxies and demonstrate that, regardless of the feedback scenario,
galaxies within a given H I mass bin exhibit outer H I radial profiles well approximated by an exponential function. Furthermore, the exponential decline rate remains remarkably similar across different physical prescriptions. We attribute the persistence of the H I mass-size relation to this inherent self-similarity in the H I mass distributions.
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Instrumentation and Methods for Astrophysics
Towards Baikal-Top: Feasibility study of an onshore detector system for the joint registration of EAS with Baikal-GVD
E.A. Kravchenko, G.I. Rubtsov and D.S. Zhadan
We study the possibility of registering high-energy extensive air showers (EAS) by the onshore detector facility simultaneously with the trigger of the Baikal-GVD
neutrino telescope. The location of the surface detector array on the shore of Lake Baikal is motivated by the fact that permanent placement of detectors on the surface of the lake is challenging. Within the given geometry, simultaneous registration is possible for EAS with a zenith angle of about 76 degrees within the limited solid angle. The corresponding inclined EAS are dominated by
muons and significantly attenuated. The installation will make it possible to obtain an estimate of the number of high-energy
muons in EAS. This, subsequently, would make it possible to verify EAS modeling and calculations of the atmospheric
neutrino flux. The detector may also be used for cross-calibration of energy and direction measurements by the
neutrino telescope. We use the CORSIKA program to simulate the registration of EAS on the shore close to the Baikal-GVD. The propagation of ultra-high energy
muons produced by EAS through 3.5 km of water and their registration by Baikal-GVD is simulated using the PROPOSAL package. We calculate the minimal total area of the onshore detectors suitable for several
cosmic ray energy thresholds, starting from 1 PeV. The report presents estimates of the number of events jointly registered by the onshore installation and the Baikal-GVD the EAS registration detector systems with different areas.
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Cosmology and Nongalactic Astrophysics
Constraining regular primordial black holes with isocurvature gravitational waves
Ngo Phuc Duc Loc
We find the constraint on the population of ultra-light regular
primordial black holes (RPBHs) by using isocurvature gravitational waves (GW). If ultra-light RPBHs dominated the early Universe, the initial isocurvature perturbation is converted into
curvature perturbation that induce second-order GW background upon evaporation of RPBHs. The upper limit of extra relativistic degrees of freedom $\Delta N_{\rm eff}$, which could be inferred from Big Bang Nucleosynthesis or
Cosmic Microwave Background observations, places a constraint on the maximum energy density of GW, which in turn can be used to constrain the RPBH population. As RPBHs have different lifetime from their singular counterparts, the constraint must be modified accordingly. While the formalism that we provide is generic, we work out explicitly the case of Simpson-Visser metric for demonstration. The RPBHs associated with this metric have lower Hawking temperature and smaller horizon size, leading to a longer lifetime than the singular Schwarzschild black holes. This implies a stronger constraint on RPBH population as they dominate the Universe for a longer period of time and generate stronger GW.
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Solar and Stellar Astrophysics
A Morpho-kinematic Study of Galactic High-ADF PNe Based on the VLT/UVES Deep Spectroscopy
Haomiao Huang, Xuan Fang, Jorge Garcia-Rojas et al. (+3 more)
We report detailed analyses of deep, high-resolution spectra of three
Galactic planetary nebulae (PNe) with high abundance discrepancy factors (ADFs), Hf2-2, M1-42 and NGC6153, obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES) on the 8.2m Very Large
Telescope (VLT). These spectra were carefully reduced, including rigorous absolute flux calibration, yielding detections of ~410-800 emission lines in each PN.
Plasma diagnostics and abundance calculations were critically performed using nebular lines. In all three PNe, the electron temperatures derived using the collisionally excited lines (CELs) are higher than those yielded by the HI Balmer and Paschen jumps, while the temperatures yielded by the OII and NII optical recombination lines (ORLs) are very low, <2000 K, indicating that the heavy-element ORLs probe cold nebular regions. The ORL abundances of N, O and Ne are systematically higher than the corresponding CEL values, confirming high ADFs in the three objects. Position-velocity (PV) diagrams were created, and spatio-kinematical studies show that CELs come from the outer nebular regions, while the ORL-emitting regions are close to nebular center. Additionally, the velocity indicated by CEL line-splitting decreases with ionization potential, which was not obvious in ORLs. These spatial and kinematic differences support two distinct components of ionized gas: a cold, metal-rich component and a warmer component with normal
metallicity. Heavy elements are strongly enriched in the cold gas, while its H^+ fraction is low but still produces significant HI emission, affecting CEL abundance estimates.
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All authors Haomiao Huang, Xuan Fang, Jorge Garcia-Rojas, Zhijun Tu, Jifeng Liu, Xiaowei Liu
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Searching for binary black hole mergers with deep learning in Advanced LIGO's third observing run
Damon Beveridge, Alistair McLeod, Linqing Wen et al. (+2 more)
The detection of gravitational waves from compact binary coalescences has provided significant insights into our Universe, and the discovery of new and unique gravitational wave candidates from independent searches remains an ongoing field of research. In this work, we built a hybrid search pipeline that combines matched filtering and deep learning to identify
stellar-mass binary black hole candidates from detector strain data. We first present results from a targeted injection study to
benchmark the sensitivity of our method and compare it with existing search pipelines. We demonstrate that our hybrid approach has comparable sensitivity for injections with a source-frame chirp mass greater than 25$\,$M$_{\odot}$, and below this threshold our sensitivity drops off for signals with a network SNR less than 15. We also observe that our search method can identify a significant population of unique candidates. Furthermore, we conduct an offline search for gravitational wave candidates in the third observing run of the LIGO-Virgo-KAGRA Collaboration (LVK), yielding 31 candidates previously reported by the LVK with a probability of astrophysical origin $p_{\rm astro}\geq0.5$. We identify two other candidates: one previously reported only in a search conducted by the Institute for Advanced Study, and one previously unreported promising new candidate with a $p_{\rm astro}$ of 0.63. This unique candidate has a high chirp mass and a high probability that the primary black hole is an intermediate-mass black hole.
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All authors Damon Beveridge, Alistair McLeod, Linqing Wen, Weichangfeng Guo, Andreas Wicenec
High Energy Astrophysical Phenomena
Chlorine and Potassium Enrichment in the Cassiopeia A Supernova Remnant
XRISM collaboration
The elements in the universe are synthesized primarily in
stars and
supernovae, where
nuclear fusion favors the production of even-Z elements. In contrast, odd-Z elements are less abundant and their yields are highly dependent on detailed
stellar physics, making theoretical predictions of their
cosmic abundance uncertain. In particular, the origin of odd-Z elements such as phosphorus (P), chlorine (Cl), and potassium (K), which are important for
planet formation and life, is poorly understood. While the abundances of these elements in Milky Way
stars are close to
solar values,
supernova explosion models systematically underestimate their production by up to an order of magnitude, indicating that key mechanisms for odd-Z nucleosynthesis are currently missing from theoretical models. Here we report the observation of P, Cl, and K in the
supernova remnant Cassiopeia A using high-resolution X-ray spectroscopy with XRISM, with the detection of K at above the 6$\sigma$ level being the most significant finding.
Supernova explosion models of normal massive
stars cannot explain the element abundance pattern, especially the high abundances of Cl and K, while models that include
stellar rotation, binary interactions or shell mergers agree closely with the observations. Our observations suggest that such
stellar activity plays a significant role in supplying these elements to the universe.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Koichi Saito, Tsuyoshi Miyatsu and Myung-Ki Cheoun
We unite the dual quarkyonic model with the
quark-
meson coupling (QMC) model to construct a novel
nuclear model based on the
quark degrees of freedom, which can cover a wide range of
nuclear densities, from low density to the crossover region. In the model, the relativistic, gaussian
quark wavefunction is used to describe the nucleon structure. We first evaluate the energy density, chemical potential, pressure and sound velocity within the ideal
Fermi gas picture. In this case, those physical quantities are discontinuous or divergent at the
quark saturation density, where the quarkyonic phase emerges. To remove such singular behavior, we next introduce an infrared regulator, and combine the dual quarkyonic model and the QMC model to include the
nuclear interaction – we call it the quarkyonic
quark-
meson coupling (QQMC) model. In this model, the
quark saturation density depends strongly on the nucleon size. For example, when $r_p = 0.6\, (0.8)$ fm, where $r_p$ is the root-mean-square radius of the
proton, the
quark saturation density is about $3.6\,(1.5) \times \rho_0$ in symmetric
nuclear matter, where $\rho_0$ is the
nuclear saturation density. Furthermore, the
nuclear interaction plays an important role in considering physical quantities quantitatively. In fact, the QQMC model can produce the sound velocity which is consistent with that inferred from the observed data of several
neutron stars. Furthermore, pressure in symmetric or pure
neutron matter deduced from the experiments of heavy-ion collisions at high energy can be explained by the QQMC model as well. We discuss in detail the formulation for the QQMC model and the physical quantities calculated by the model.
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Solar and Stellar Astrophysics
The Binary Fraction of Stars in the Dwarf Galaxy Ursa Minor via Dark Energy Spectroscopic Instrument
Tian Qiu, Wenting Wang, Sergey Koposov et al. (+45 more)
We utilize multi-epoch line-of-sight velocity measurements from the Milky Way Survey of the Dark Energy Spectroscopic Instrument to estimate the binary fraction for member
stars in the
dwarf spheroidal
galaxy Ursa Minor. Our
dataset comprises 670 distinct member
stars, with a total of more than 2,000 observations collected over approximately one year. We constrain the binary fraction for UMi to be $0.61^{+0.16}_{-0.20}$ and $0.69^{+0.19}_{-0.17}$, with the binary orbital parameter distributions based on
solar neighborhood observation from Duquennoy & Mayor (1991) and Moe & Di Stefano (2017), respectively. Furthermore, by dividing our data into two subsamples at the median
metallicity, we identify that the binary fraction for the metal-rich ([Fe/H]>-2.14) population is slightly higher than that of the metal-poor ([Fe/H]<-2.14) population. Based on the Moe & Di Stefano model, the best-constrained binary fractions for metal-rich and metal-poor populations in UMi are $0.86^{+0.14}_{-0.24}$ and $0.48^{+0.26}_{-0.19}$, respectively. After a thorough examination, we find that this offset cannot be attributed to sample selection effects. We also divide our data into two subsamples according to their projected radius to the center of UMi, and find that the more centrally concentrated population in a denser environment has a lower binary fraction of $0.33^{+0.30}_{-0.20}$, compared with $1.00^{+0.00}_{-0.32}$ for the subsample in more outskirts.
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All authors Tian Qiu, Wenting Wang, Sergey Koposov, Ting S. Li, Nathan R. Sandford, Joan Najita, Songting Li, Jiaxin Han, Arjun Dey, Constance Rockosi, Boris Gaensicke, Jesse Han, Benjamin Alan Weaver, Adam Myers, Jessica Nicole Aguilar, Steven Ahlen, Carlos Allende Prieto, Davide Bianchi, David Brooks, Todd Claybaugh, Axel de la Macorra, Peter Doel, Andreu Font-Ribera, Jaime Forero-Romero, Enrique Gaztanaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Jorge Jimenez, Dick Joyce, Theodore Kisner, Claire Lamman, Martin Landriau, Laurent Le Guillou, Aaron Meisner, Ramon Miquel, Seshadri Nadathur, Will Percival, Claire Poppett, Francisco Prada, Ignasi Perez-Rafols, Graziano Rossi, Eusebio Sanchez, David Schlegel, Joseph Harry Silber, David Sprayberry, Gregory Tarle, Rongpu Zhou, Hu Zou
Astrophysics of Galaxies · Cross-listed from gr-qc
On angular dependent response to gravitational-wave signals for time-delay interferometry combinations
Pan-Pan Wang, Hao-Kang Chen, Wei-Liang Qian et al. (+5 more)
Space-based gravitational wave (GW) detectors are designed for wave sources in the millihertz band with different locations and orientations. Time-delay interferometry (TDI) technique is an indispensable ingredient in space-borne GW detection that effectively suppresses the
laser phase noise. The abundant TDI solutions derived in the literature also feature distinct angular-dependent sensitivities. Because a GW source's angular location is unknown prior to the signals' detection, a solid-angle average is often performed when analyzing the sensitivity function of a given TDI combination. The present study explores the angular dependence of the detector's sensitivity. This detail is relevant, because once the initial detection is achieved, the source's location can be extracted and used to provide information on a refined TDI combination tailored for the specific GW source. As the TDI technique is a post-processing
algorithm, such a procedure can be implemented in practice. We evaluate the angular dependence of the detector's response function to the GW signals for different TDI combinations as a function of the orientation angles. Moreover, we classify the response functions into seven categories at the low-frequency limit, leveraging the characteristics of the underlying geometrical TDI combinations. By further averaging out the azimuthal angle $\phi_D$ in the detector's plane, the main features of the resulting response functions and their zenithal dependence with respect to the GW source are scrutinized. The findings presented in this work provide pertinent insights for ongoing space-borne detector programs.
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All authors Pan-Pan Wang, Hao-Kang Chen, Wei-Liang Qian, Rui Luo, Jing Zhou, Wei-Sheng Huang, Yu-Jie Tan, Cheng-Gang Shao
Earth and Planetary Astrophysics
JWST Exoplanetary Worlds and Elemental Survey (JEWELS) I: High-Precision Chemical Abundances of 20 FGK Planet-Hosting Stars from JWST Cycle 2
Qinghui Sun
We present high-precision chemical abundances for 20 FGK
stars hosting
planets observed in JWST Cycle 2 GO programs. Using high-resolution, high-signal-to-noise ratio spectra from the ESO and Keck archives, we perform a strict line-by-line differential analysis relative to the Sun to derive
stellar parameters and abundances of 19 elements from C to Zn. The
stars span effective temperatures of 4500-6500 K and
metallicities from -0.57 to +0.50 dex. The sample includes hosts of both gas
giants and terrestrial
planets, allowing direct comparison between
stellar composition and planetary properties. Several of the
giant planets orbit metal-rich
stars. The detailed abundance patterns show clear chemical diversity, including carbon-enhanced but mildly metal-poor
stars (TOI-824, TOI-1130, GJ 9827) and $\alpha$-enhanced metal-poor
stars (TOI-561, GJ 9827, TOI-824). These variations trace differences in protoplanetary disk composition and may influence planetary interiors and atmospheric chemistry. The
planet-hosts show a range of [C/O] ratios, and the diverse [Mg/Si] ratios may suggest varied interior compositions for their rocky
planets. This homogeneous
stellar abundance, together with future uniform JWST planetary atmosphere measurements, provides a foundation for exploring the
planet mass-
metallicity relation and the connection between
stellar chemistry and planetary formation pathways. These results constitute the first step in a larger survey spanning multiple JWST cycles to systematically examine how host
star composition shapes exoplanetary systems.
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High Energy Astrophysical Phenomena
Mini-supernovae from white dwarf-neutron star mergers: Viewing-angle-dependent spectra and lightcurves
Yacheng Kang, Jin-Ping Zhu, Lijing Shao et al. (+3 more)
Unstable mass transfer may occur during white
dwarf-
neutron star (WD-NS) mergers, in which the WD can be tidally disrupted and form an
accretion disk around the NS. Such an
accretion disk can produce unbound wind ejecta, with synthesized $^{56}\mathrm{Ni}$ mixed in. Numerical simulations reveal that this unbound ejecta should be strongly polar-dominated, which may cause the following radioactive-powered thermal transient to be viewing-angle-dependent. This issue has so far received limited investigation. We investigate how the intrinsically non-spherical geometry of WD-NS wind ejecta affects the viewing-angle dependence of the thermal transients. Using a two-dimensional axisymmetric ejecta configuration and incorporating heating from the radioactive decay of $^{56}\mathrm{Ni}$, we employ a semi-analytical discretization scheme to simulate the observed viewing-angle-dependent photospheric
evolution, as well as the resulting spectra and lightcurves. The observed photosphere evolves over time and depends strongly on the viewing angle: off-axis observers can see deeper, hotter inner layers of the ejecta and larger projected photospheric areas compared to on-axis observers. For a fiducial WD-NS merger producing 0.3
solar mass of ejecta and 0.01
solar mass of synthesized $^{56}\mathrm{Ni}$, the resulting peak optical absolute magnitudes of the transient span from ~ -12 mag along the polar direction to ~ -16 mag along the equatorial direction, corresponding to luminosities of $10^{40}$-$10^{42}$ erg s$^{-1}$. The typical peak timescales are expected to be 3-10 d. We for the first time explore the viewing-angle effect on WD-NS merger transients. Since their ejecta composition and energy sources resemble those of
supernovae, yet WD-NS merger transients are dimmer and evolve more rapidly, we propose using "mini-
supernovae" to describe the thermal emission following WD-NS mergers.
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All authors Yacheng Kang, Jin-Ping Zhu, Lijing Shao, Jiahang Zhong, Jinghao Zhang, Bing Zhang
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Linear stability of nonrelativistic Proca stars
Emmanuel Chávez Nambo, Galo Diaz-Andrade, Alberto Diez-Tejedor et al. (+3 more)
We study the linear stability of nonrelativistic Proca
stars under generic perturbations. Using a combination of analytic and numerical methods, we demonstrate that, as expected, the ground state is always mode-stable. Additionally, we identify several mode-stable spherically symmetric excited states, including stationary states of constant and radial polarization, as well as multi-frequency states in case that the
spin-
spin selfinteraction vanishes. The existence of stable excited states may have implications for
spin-$1$ ultralight dark matter models.
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All authors Emmanuel Chávez Nambo, Galo Diaz-Andrade, Alberto Diez-Tejedor, Edgar Preciado-Govea, Armando A. Roque, Olivier Sarbach
Instrumentation and Methods for Astrophysics
Design and dynamics experiment of filter wheel mechanism of space coronagraph
Wei Guo, Jiangpei Dou, Mingming Xu et al. (+4 more)
In order to realize multi-spectral imaging of space coronagraph, a compact filter wheel mechanism is designed. The filters with different spectral transmittance can be cut into the optical path at different times by this mechanism. Because the image contrast of space coronagraph is very high, the high stability requirement for the optical unit of coronagraph is put forward. Small modulus worm gear and worm are taken by the mechanism, in order to realize compact structure, high stiffness, the unidirectional 360 degrees rotation and reverse self-locking function. The precision, stiffness, mechanical properties and reliability of the mechanism are analyzed in the paper. The results show that the position accuracy of the filter wheel can meet the requirement of 0.5mm. The first order modal of the mechanism is 313Hz. The results of vibration test indicate that stiffness, dynamic performance and reliability of the mechanism can be meet. Therefore, the design of filter wheel in this paper can ensure the multi-spectral imaging requirements under complex spatial conditions.
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All authors Wei Guo, Jiangpei Dou, Mingming Xu, Linyi Kong, Baolu Liu, Bo Chen, Shu Jiang
Astrophysics of Galaxies
ELG$\times$LRG distribution through dark matter halo dynamics
Ginevra Favole, Francisco-Shu Kitaura, Boryana Hadzhiyska et al. (+3 more)
We investigate the clustering and
halo occupation distribution (HOD) of DESI Y1 emission-line (ELGs) and luminous red (LRGs)
galaxies at $0.8<z<1.1$, including their cross-correlation (ELG$\times$LRG), using the AbacusSummit suite and a new
Halo Occupation Model (HOMe) for
galaxy multi-tracers. This integrates intra-
halo dynamics,
halo exclusion, and quenching, bridging insights from hydrodynamical, HOD, abundance-matching, and semi-analytic studies. Leveraging full phase-space information from the Uchuu N-body simulation, and sampling satellites from dark-matter particle positions via physically motivated prescriptions, HOMe reproduces the anisotropic clustering down to $s=200\,h^{-1}$kpc with unprecedented accuracy. Model parameters are inferred solely from two-point statistics using a two-level
Bayesian framework, yielding high-fidelity ELG, LRG and cross-reference catalogs. We find that satellite ELGs behave as incoherent flows within their parent
halos, dominating the clustering below $4\,h^{-1}$Mpc. The HOD from the best-fit HOMe has the following properties: (i) 90.50% (85.91%) of ELGs (LRGs) are central
galaxies without satellites, residing in
halos of $M_{\rm vir}\sim6.6\times10^{11}\,(1.2\times10^{13})\,h^{-1}{\rm M}_\odot$; (ii) the ELG$\times$LRG cross-correlation is governed by central-central pairs and shaped by
halo exclusion on $2-5\,h^{-1}$Mpc scales; (iii) 9.50% (14.09%) of ELGs (LRGs) are satellites, of which 1.09% (3.52%) inhabit
halos with a central
galaxy of the same species in a maximally conformal configuration, 7.02% (0.005%) orbit complementary hosts in a minimally conformal state, and 0.58% (10.57%) are orphans. The high sensitivity of HOMe precisely captures the dynamics of satellites in different host environments, opening a promising avenue for understanding systematics, the dynamical nature of dark matter, potentially distinguishing
gravity models.
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All authors Ginevra Favole, Francisco-Shu Kitaura, Boryana Hadzhiyska, Daniel J. Eisenstein, Lehman H. Garrison, Sownak Bose
High Energy Astrophysical Phenomena
Solar Cycle Variation of Sustained Gamma Ray Emission from the Sun
Nat Gopalswamy, Pertti Mäkelä, Seiji Yashiro et al. (+3 more)
We investigated the occurrence rate of the sustained gamma ray emission (SGRE) events from the Sun using data obtained by
Fermi Large Area
Telescope (LAT) since its launch in 2008. Only 16 SGRE events were observed during the first 61 months of
solar cycle (SC) 25, likely due to the
solar array drive assembly's malfunction in 2018; 27 SGRE events were observed in SC 24 over the corresponding epoch. The average sunspot number (SSN) increased from 56.9 in SC 24 to 79.0 in SC 25. Fast and wide (FW) CMEs and decameter-hectometric (DH) type II bursts increased significantly in SC 25 by 29% and 33%, respectively when normalized to SSN. Therefore, we expect a higher number of SGREs in SC 25. We estimated the number of SGREs in SC 25 using three methods. (i) If the SGRE number varies commensurate with SSN, we should have 38 SGRE events in SC 25. However, FW CMEs and DH type II bursts in SC 25 were overabundant by 29% and 33%, so the number SGRE events should be 48 or 50. (ii) In SC 24, ~18% of FW CMEs and 27% of DH type II bursts were associated with SGRE events. At this rate SC 25 should have 48 and 49 SGRE events. (iii) Since SGRE events are invariably associated with >100 keV hard X-ray (HXR) bursts, we identified DH type II bursts associated with >100 keV HXR bursts from
Fermi's Gamma ray Burst Monitor (GBM) during LAT data gaps. Almost all SGRE events in SCs 24 and 25, and 27 of the 79 LAT-gap type IIs were associated with HXR bursts of duration > ~5 min. These DH type II bursts are indicative of SGRE, bringing the total number of SGRE events to 43 (16 + 27). Thus, the three methods provide similar estimates of the number of SGRE events in SC 25. We, therefore, conclude that SC 25 is stronger than SC 24 based on the estimated number SGRE events.
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All authors Nat Gopalswamy, Pertti Mäkelä, Seiji Yashiro, Sachiko Akiyama, Hong Xie, G. Sindhuja
High Energy Astrophysical Phenomena
Asymptotic constraints for 1D planar grey photon diffusion from linear transport with special-relativistic effects
Ryan T. Wollaeger, Jim E. Morel, Kendra P. Long et al. (+2 more)
We derive a grey linear
diffusion equation for
photons with respect to inertial (or lab-frame) space and time, using asymptotic analysis in 1D planar geometry. The solution of the equation is the comoving radiation energy density. Our analysis does not make use of assumptions about the magnitude of velocity; instead we derive an asymptotic scaling in the lab frame such that we avoid apparent non-physical pathologies that are encountered with the standard static-matter scaling. We permit the
photon direction to be continuous (as opposed to constraining the analysis to discrete ordinates). The result is a drift-
diffusion equation in the lab frame for comoving radiation energy density, with an adiabatic term that matches the standard semi-relativistic
diffusion equation. Following a recent study for discrete directions, this equation reduces to a pure advection equation as the velocity approaches the speed of light. We perform preliminary numerical experiments comparing solutions to relativistic lab-frame Monte Carlo transport and to the well-known semi-relativistic
diffusion equation.
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All authors Ryan T. Wollaeger, Jim E. Morel, Kendra P. Long, Mathew A. Cleveland, Robert B. Lowrie