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Edge-On Disk Study (EODS): I. Thermal structure of the Flying Saucer disk
No full textInternational audienceContext. The dust and gas temperature in protoplanetary disks play critical roles in determining their chemical evolution and influencing planet formation processes.Aims. We attempted an accurate measurement of the dust and CO temperature profile in the edge-on disk of the Flying Saucer.Methods. We used the unique properties of the Flying Saucer – its edge-on geometry and its fortunate position in front of CO clouds with different brightness temperatures – to provide independent constraints on the dust temperature. We compared it with the dust temperature derived using the radiative transfer code DISKFIT and the CO gas temperature.Results. We find clear evidence of a substantial gas temperature vertical gradient, with a cold (10 K) disk mid-plane and a warmer CO layer where T(r)≈27 (r/100 au)−0.3 K. Direct evidence of CO depletion in the mid-plane, below about 1 scale height, is also found. At this height, the gas temperature is 15–20 K, consistent with the expected CO freeze-out temperature. The dust disk appears optically thin at 345 GHz, and exhibits moderate settling
Converging on the Cepheid Metallicity Dependence: Implications of Non-Standard Gaia Parallax Recalibration on Distance Measures
No full textInternational audienceBy comparing Cepheid brightnesses with geometric distance measures including Gaia EDR3 parallaxes, most recent analyses conclude metal-rich Cepheids are brighter, quantified as mag/dex. While the value of has little impact on the determination of the Hubble constant in contemporary distance ladders (due to the similarity of metallicity across these ladders), plays a role in gauging the distances to metal-poor dwarf galaxies like the Magellanic Clouds and is of considerable interest in testing stellar models. Recently, Madore & Freedman (2025, hereafter MF25) recalibrated Gaia EDR3 parallaxes by adding to them a magnitude offset to match certain historic Cepheid parallaxes which otherwise differ by . A calibration which adjusts Gaia parallaxes by applying a magnitude offset (i.e., a multiplicative correction in parallax) differs significantly from the Gaia Team's calibration (Lindegren et al. 2021), which is additive in parallax space - especially at distances much closer than 1 kpc or beyond 10 kpc, outside the 2-3 kpc range on which the MF25 calibration was based. The MF25 approach reduces to zero. If extrapolated, it places nearby cluster distances like the Pleiades too close compared to independent measurements, while leaving distant quasars with negative parallaxes. Further, by shortening the Milky Way distance scale, the MF25 calibration raises the local Hubble constant by 1 km/s/Mpc, increasing the Hubble tension significantly. We conclude that the MF25 proposal for Gaia calibration and produces farther-reaching consequences, many of which are strongly disfavored by the data
Optical spectroscopy of blazars for the Cherenkov Telescope Array Observatory- IV
No full textInternational audienceBlazars, including BL Lacs and FSRQs, are the most luminous extragalactic γ-ray sources. They account for about 56% of the sources listed in the recent Fermi-LAT catalog (4FGL-DR4). The optical and UV spectra of BL Lacs are nearly featureless, making it difficult to precisely determine their redshifts. Consequently, nearly half of the γ-ray BL Lacs lack reliable redshift measurements. This poses a major challenge, since redshift is crucial for studying the cosmic evolution of the blazar population and γ-ray propagation studies such as indirect evidence of EBL, placing constraints on IGMF and searches for LIV and ALPs. This paper is the fourth in a series dedicated to determining the redshift of a sample of blazars identified as key targets for future observations with the Cherenkov Telescope Array Observatory (CTAO). We performed Monte Carlo simulations to select γ-ray blazars detected by Fermi-LAT with hard spectra, that lack redshift measurements. These blazars are expected to be detectable by CTAO within 30 hours or less of exposure assuming an average flux state. In this fourth paper, we report the results of detailed spectroscopic observations of 29 blazars using the ESO/VLT, Keck II, and SALT telescopes. Our analysis involved a thorough search for spectral lines in the spectra of each blazar, and when features of the host galaxy were identified, we modeled its properties. We also compared the magnitudes of the targets during the observations to their long-term light curves. In the sample studied, 9 of 29 sources were observed with a high signal-to-noise ratio (S/N > 100), while the remaining 20 were observed with a moderate or low S/N. We successfully determined firm redshifts for 12 blazars, ranging from 0.1636 to 1.1427, and identified two lower limit redshifts at z > 1.0196 and z > 1.4454. The remaining 15 BL Lac objects exhibited featureless spectra
Real-Space Chemistry on Quantum Computers: A Fault-Tolerant Algorithm with Adaptive Grids and Transcorrelated Extension
No full textFirst-quantized, real-space formulations of quantum chemistry on quantum computers are appealing: qubit count scales logarithmically with spatial resolution, and Coulomb operators achieve quadratic instead of quartic computational scaling of two-electron interactions. However, existing schemes employ uniform discretizations, so the resolution required to capture electron-nuclear cusps in high-density regions oversamples low-density regions, wasting computational resources. We address this by deploying non-uniform, molecule-adaptive grids that concentrate points where electronic density is high. Using Voronoi partitions of these grids, the molecular Hamiltonian is expressed in a Hermitian form and in a transcorrelated, isospectral form that eliminates Coulomb singularities and yields cusp-free eigenfunctions. Both formulations slot naturally into quantum eigenvalue solvers: Hermitian Quantum Phase Estimation (QPE) and the recent generalised Quantum Eigenvalue Estimation (QEVE) protocol for its non-Hermitian, transcorrelated counterpart. Numerical validation on benchmark systems confirms that this non-heuristic ab initio framework offers a promising path for accurate ground-state chemistry on quantum hardware
Analyse et identification de Plans de Gestion de Données disciplinaires pouvant être utilisés comme exemple: Produit du Groupe de Travail PGD Disciplinaires de RDA France
No full textRDA France, le chapitre français de la Research Data Alliance (RDA), a mis en place en mars 2023 le groupe de travail RDA France – Plans de Gestion de Données disciplinaires (GT PGD-DISC), avec l’objectif de constituer un corpus de plans de gestion des données (PGD) disciplinaires pouvant être utilisés comme exemple. Ce document décrit en introduction les raisons pour lesquelles RDA France a créé ce groupe de travail et la manière dont le groupe a été constitué (Section 1), puis la méthodologie employée pour élaborer le corpus (Section 2) et le contenu de celui-ci, en termes de données et de métadonnées (Section 3). La maintenance envisagée pour le corpus est décrite en conclusion (Section 4).La Version 1 de la liste de plans de gestion de données disciplinaires résultant du travail du groupe est publiée dans l’entrepôt de l’infrastructure Recherche Data Gouv (https://doi.org/10.57745/ZSWLYJ)
Study of Higgs boson pair production in the final state with 308 fb of data collected at TeV and 13.6 TeV by the ATLAS experiment
No full textInternational audienceA search for Higgs boson pair production in the final state is performed. The proton-proton collision dataset in this analysis corresponds to an integrated luminosity of 308 fb, consisting of two samples, 140 fb at a centre-of-mass energy of 13 TeV and 168 fb at 13.6 TeV, recorded between 2015 and 2024 by the ATLAS detector at the CERN Large Hadron Collider. In addition to a larger dataset, this analysis improves upon the previous search in the same final state through several methodological and technical developments. The Higgs boson pair production cross section divided by the Standard Model prediction is found to be ( expected), which translates into a 95% confidence-level upper limit of . At the same confidence level the Higgs self-coupling modifier is constrained to be in the range ( expected)
The Impact of the Transport of Chemicals and Electronic Screening on Helioseismic and Neutrino Observations in Solar Models
No full textInternational audienceThe transport of chemical elements in stellar interiors is one of the greatest sources of uncertainties of solar and stellar modelling. The Sun, with its exquisite spectroscopic, helioseismic and neutrino observations, offers a prime environment to test the prescriptions used for both microscopic and macroscopic transport processes. We study in detail the impact of various formalisms for atomic diffusion on helioseismic constraints in both CLES (Scuflaire et al. 2008a) and Cesam2k20 (Morel and Lebreton 2008; Marques et al. 2013; Deal et al. 2018) models and compare both codes in detail. Moreover, due to the inability of standard models using microscopic diffusion to reproduce light element depletion in the Sun (Li, Be), another efficient process must be included to reproduce these constraints (rotation-induced: Eggenberger et al. 2022, overshooting -or penetrative convection- below the convective envelope: Thévenin et al. 2017, or ad hoc turbulence: Lebreton and Maeder 1987; Richer, Michaud, and Turcotte 2000). However, introducing such an extra mixing leads to issues with the CNO neutrino fluxes (see Buldgen et al. 2023), which seem to be systematically lower than the Borexino observations (Appel et al. 2022). Another key aspect to consider when reconciling models with neutrino fluxes is the impact of electronic screening (Mussack and Däppen 2011)
Gaps in stellar streams as a result of globular cluster flybys: The case of Palomar 5
No full textInternational audienceContext. Thin stellar streams, such as those resulting from the tidal disruption of globular clusters, have long been known and used as probes of the gravitational potential of our Galaxy, both its visible and dark contents. The literature commonly interprets the presence of underdensity regions, or gaps, along these streams as being due to the close passage of dark matter subhalos.Aims. In this work, we investigate the perturbations induced on streams by the passage of dense stellar systems, such as globular clusters themselves, to test the possibility that they may cause the formation of gaps as well. In particular, we focus on the study of the stream generated by a cluster with characteristics (mass, size, and orbit) similar to those of Palomar 5, a well-known globular cluster in the Galactic halo that has particularly long tidal tails.Methods. For this purpose, we used a particle-test code to simulate the formation and evolution of the stream when subjected to the Galaxy’s gravitational field plus its whole system of globular clusters.Results. Our study shows that such a stream can be strongly perturbed by the close passage of other clusters, in particular NGC 2808, NGC 7078, and NGC 104, and that these perturbations induce the formation of gaps in the tails.Conclusions. The results of this work show that globular clusters can induce gaps in cold streams–just as it has been demonstrated in the literature for that other baryonic components, such as giant molecular clouds and the Galactic bar. Therefore, a future work that attempts to infer the dark matter subhalo distribution from stellar stream gaps must include the contributions from globular clusters
Modeling Particle Acceleration and Release from Solar Eruptions
No full textInternational audienceDetermining the relative contribution of solar flares versus coronal mass ejections in large solar energetic particle (SEP) events is a long-standing problem. Flare-accelerated particles may travel through complex magnetic fields in the eruption region and escape into interplanetary space, thereby contributing to large SEP events. The process by which flare accelerated particles are released into the heliosphere is poorly understood and yet is critical to advancing our understanding of SEPs. In this work, we address the release problem by solving the focused transport equation in the context of a 2.5D ARMS magnetohydrodynamic simulation of a breakout coronal mass ejection (CME)/flare event. We find that particles accelerated by flare reconnection can be released into interplanetary space through interchange reconnection between closed and open field lines. These particles can contribute directly to SEP events and may become an important seed population for further acceleration by CMEdriven shocks. Additionally, we find that the energetic particle fluxes in the inner heliosphere remain elevated for an extended period, allowing them to contribute to SEP acceleration by subsequent CMEs. This study represents the first direct particle modeling of how flare-accelerated particles can contribute to major SEP events.Unified Astronomy Thesaurus concepts: Interplanetary particle acceleration (826); Solar magnetic reconnection (1504); Solar flares (1496); Solar corona (1483); Space plasmas (1544)</div
