Evolutionary tracks, ejecta, and ionizing photons from intermediate-mass to very massive stars with PARSEC

International audienceRecent advancements in stellar evolution modeling offer unprecedented accuracy in predicting the evolution and deaths of stars. We present new stellar evolutionary models computed with the updated PARSEC V2.0 code for a comprehensive and homogeneous grid of metallicities and initial masses. Nuclear reaction networks, mass loss prescriptions, and the treatment of elemental mixing have all been updated in PARSEC V2.0. We computed models for thirteen initial metallicities spanning $Z = 10^{-11}$ to $Z = 0.03$, with masses ranging from 2.0 M$_{\odot}$ to 2000 M$_{\odot}$, consisting of a library of over 1,100 ($\sim 2100$ tracks including pure-He models) full stellar evolution tracks. For each track, the evolution is followed from the pre-main-sequence to the most advanced early-asymptotic-giant-branch or the pre-supernova phases, depending on the stellar mass. Here, we describe the properties of the tracks and their chemical and structural evolution. We computed the final fates and the remnant masses and built the mass spectrum for each metallicity, finding that the combined black hole (BH) pair-instability mass gap spans just between 100 and 130 M$_{\odot}$. Moreover, the remnant masses provide models consistent with observed BH masses, such as those from the primaries of GW190521, Cygnus X-1, and $\textit{Gaia}$ BH3 binary systems. We computed and provided the chemical ejecta from stellar winds and explosive final fates, along with the ionizing photon rates. Our results show strong overall consistency with other tracks computed with different codes. A comparison with a large sample of observed massive stars in the Tarantula Nebula of the Large Magellanic Cloud shows that our tracks nicely reproduce the majority of stars that lie on the main sequence. All the models are publicly available and can be retrieved on the PARSEC database

Vulnerability of benthic trait diversity across the Mediterranean Sea following mass mortality events

International audienceUnraveling the functional future of marine ecosystems amid global change poses a pressing challenge. This is particularly critical in the Mediterranean Sea, which is highly impacted by global and local drivers. Utilizing extensive mass mortality events (MMEs) datasets spanning from 1986 to 2020 across the Mediterranean Sea, we investigated the trait vulnerability of benthic species that suffered from MMEs induced by nine distinct mortality drivers. By analyzing changes in ten ecological traits across 389 benthic species—constituting an extensive compendium of Mediterranean ecological traits to date—we identified 228 functional entities (FEs), defined as groups of species sharing the same trait values. Our findings indicate that of these 55 FEs were impacted by MMEs, accentuating a heightened vulnerability within specific trait categories. Notably, more than half of the mortality records showed severe impacts on calcifying and larger species with slower growth which mostly account for tree-like and massive forms. Altogether, we highlight that 29 FEs suffered extreme mortality, leading to a maximum increase of 19.1% of the global trait volume vulnerability over 35 years. We also reveal that 10.8% of the trait volume may have been temporarily lost over the last five years, emphasizing the risk of a rapid ecological transformation in the Mediterranean Sea

The EXOD search for faint transients in XMM-Newton observations. Part II

International audienceThe XMM-Newton observatory has accumulated a vast archive of over 17,000 X-ray observations over the last 25 years. However, the standard data processing pipelines may fail to detect certain types of transient X-ray sources due to their short-lived or dim nature. Identifying these transient sources is important for understanding the full range of temporal X-ray behaviour, as well as understanding the types of sources that could be routinely detected by future missions such as Athena. This work aims to reprocess XMM-Newton archival observations using newly developed dedicated software in order to identify neglected and missed transient X-ray sources that were not detected by the existing pipeline. We use a new approach that builds upon previous methodologies, by transforming event lists into data cubes, which are then searched for transient variability in short time windows. Our method enhances the detection capabilities in the Poisson regime by accounting for the statistical properties of sparse count rates, and allowing for transient search in previously discarded periods of high background activity. Our reprocessing efforts identified 32,247 variable sources at the 3-sigma level and 4,083 sources at the 5-sigma level in 12,926 XMM archival observations. We highlight four noteworthy sources: A candidate quasi-periodic eruption (QPE), a new magnetar candidate, a previously undetected Galactic hard X-ray burst and a possible X-ray counterpart to a Galactic radio pulsar. Our method demonstrates a new, fast, and effective way to process event list data from XMM-Newton, which is efficient in finding rapid outburst-like or eclipsing behaviour. This technique can be adapted for use with future telescopes, such as Athena, and can be generalised to other photon counting instruments operating in the low-count Poisson regime

Ecological impacts, efficacy and economic feasibility of algal mat removal from temperate intertidal mudflats under blue nitrogen trading schemes

International audienceDriven by eutrophic conditions, AM (algal mat) proliferation is now ubiquitous in coastal areas generating significant ecological and economic impacts. The need to mitigate negative effects has prompted the exploration of removal methods, but neither the success nor the impacts on intertidal mudflats have been assessed. Limited success using a specially-adapted vessel, prompted a shift to manual removal by hand-rake at two UK (Portsmouth and Poole) and two French study sites (Brittany and Normandy). Significant reductions in AM biomass and percentage cover were only observed at one site (Portsmouth), in contrast to significant temporal effects throughout the 180 days at each site. Significant effects of removal on the benthos and birds were also limited to an increase in organic content at Brittany and a reduction in macrofaunal abundance at Poole but with all sites dominated by temporal effects. To assess if AM removal can be used to ameliorate excess nitrogen (N) we calculated the amount of N that could be removed from a site and its potential cost-effectiveness (price of N credit after subtraction of removal costs) within an NTS (Nutrient Trading Scheme). N export by AM removal is influenced by site and season, for example, 66 kg N ha- 1 yr- 1 (winter) to 95 kg N ha- 1 yr- 1 (summer) at Poole. N removal rates from some sites (Poole, all seasons; Brittany, autumn) are comparable to other Nature-Based Solutions (NBSs) such as clam aquaculture. However, a single annual AM harvest at these sites yields lower N removal rates compared to seaweed, mussel, and oyster aquaculture. Using a global mean N credit price, the removals at Poole and Portsmouth have medium/high cost-effectiveness across all seasons, potentially generating up to half a million pounds of N credits, which could be increased if post-harvesting value-chains were maximised e.g. biofuel production. Although, implementation at scale could rapidly reduce the many impacts of AMs and contribute to the blue-green bioeconomy revolution, to improve water quality, AM removal must be framed within a multifaceted management process

Ohmic heating in the upper atmosphere of hot exoplanets: The influence of a time-varying magnetic field

International audienceContext. Exoplanets on close-in orbits are subject to intense X-ray and ultraviolet (XUV) irradiation from their star. Their atmosphere heats up, sometimes to the point where it will thermally escape from the gravitational potential of the planet. Nonetheless, XUV is not the only source of heating in such atmospheres. Indeed, close-in exoplanets are embedded in a medium (the stellar wind) with strong magnetic fields that can significantly vary along the orbit. Variations in this magnetic field can induce currents in the upper atmosphere, which dissipate and locally heat it up through Ohmic heating.Aims. The aim of this work is to quantify Ohmic heating in the upper atmosphere of hot exoplanets, due to an external time-varying magnetic field, and to compare it to the XUV heating.Methods. Ohmic heating depends strongly on the conductivity properties of the upper atmosphere. We developed a 1D formalism to assess the level and the localization of Ohmic heating depending on the conductivity profile. The formalism is applied to the specific cases of Trappist-1 b and π Men c.Results. Ohmic heating can reach values up to 10−3 erg s−1 cm−3 in the upper atmospheres of hot exoplanets. It is expected to be stronger the closer the planet and the lower its central star mass, as these conditions maximize the strength of the ambient magnetic field around the planet. The location of maximal heating depends on the conductivity profile (but does not necessarily occurs at the peak of conductivity) and, in particular, on the existence and strength of a steady planetary field. Such extra heating can play a role in the thermal budget of the escaping atmosphere when the planetary atmospheric magnetic fields is between 0.01 and 1 G.Conclusions. We confirm that Ohmic heating can play an important role in setting the thermal budget of the upper atmosphere of hot exoplanets and can even surpass the XUV heating in the most favorable cases. When it is strong, a corollary is that the upper atmosphere screens efficiently time-varying external magnetic fields, preventing them from penetrating deeper in the atmosphere or even within the planet itself. We find that both Trappist-1b and π Men c are likely being subjected to intense Ohmic heating

The DESI-Lensing Mock Challenge: large-scale cosmological analysis of 3x2-pt statistics

International audienceThe current generation of large galaxy surveys will test the cosmological model by combining multiple types of observational probes. Realising the statistical promise of these new datasets requires rigorous attention to all aspects of analysis including cosmological measurements, modelling, covariance and parameter likelihood. In this paper we present the results of an end-to-end simulation study designed to test the analysis pipeline for the combination of the Dark Energy Spectroscopic Instrument (DESI) Year 1 galaxy redshift dataset and separate weak gravitational lensing information from the Kilo-Degree Survey, Dark Energy Survey and Hyper-Suprime-Cam Survey. Our analysis employs the 3x2-pt correlation functions including cosmic shear and galaxy-galaxy lensing, together with the projected correlation function of the spectroscopic DESI lenses. We build realistic simulations of these datasets including galaxy halo occupation distributions, photometric redshift errors, weights, multiplicative shear calibration biases and magnification. We calculate the analytical covariance of these correlation functions including the Gaussian, noise and super-sample contributions, and show that our covariance determination agrees with estimates based on the ensemble of simulations. We use a Bayesian inference platform to demonstrate that we can recover the fiducial cosmological parameters of the simulation within the statistical error margin of the experiment, investigating the sensitivity to scale cuts. This study is the first in a sequence of papers in which we present and validate the large-scale 3x2-pt cosmological analysis of DESI-Y1

Spectroscopic approach to chlorine local environment in aluminoborosilicate glasses

International audienceChlorine local environment has been investigated using spectroscopic approach (XAS and XPS) for Na-and Ca-bearing aluminoborosilicate glasses synthesised at 1.0 GPa. Based on Cl K-edge EXAFS results, Cl appears to show two local environments in glasses: one at long distance ~2.7 Å assigned to Cl -species charge compensated by Na + and/or Ca 2+ and one at short distance ~1.8 Å assigned to Cl-Cl and Si-Cl species. The Cl 2p XPS results cannot unambiguously confirm the presence of Si-Cl overlapped with Na + /Ca 2+ …Cl -species

Mars as a Planet B?

International audienceThe concept of terraforming Mars has been popularized in pop culture and recently by Elon Musk. The objective is to transform Mars into a planet suitable for habitation by living organisms and humans. Conceptually, this may be achieved in different steps: firstly, by increasing the atmospheric pressure of the whole planet to allow human beings to perform outdoor activities, possibly equipped with only an oxygen mask and without a pressurized suit. Secondly, by transforming the environment to make terrestrial organisms able to survive and proliferate. Thirdly, by creating a breathable atmosphere. The process would require a strong thickening of the atmosphere. A method to restore the early Mars CO2 atmosphere had been hypothesized in the 1990s, but after 30 years of Mars exploration, its feasibility is strongly questioned. Even if terraforming became possible, implementing it would violate many principles of modern environmental ethics. Assuming it is done for the purpose of habitation, it would also raise many legal and societal issues, pertaining notably to the relationships between communities on Mars and the Earth’s populations, structures, and rules

Evaluation of three modelling frameworks of thermal infrared radiative transfer for directional anisotropies of temperatures

International audienceRadiative transfer models (RTMs) designed to reproduce the anisotropy of surface brightness temperature are particularly useful for applications on Earth’s energy budget when using remote sensing data sets. Despite the fact that several thermal infrared (TIR) RTMs have been developed, a quantitative analysis comparing the benefits and limits of these models remains necessary. Herein, three modeling frameworks (physical hybrid, analytical parameterization, kernel-driven) have been evaluated comparatively for a homogeneous vegetation, a row-planted crop and a sparse forest. Airborne measurements and the Discrete Anisotropy Radiative Transfer (DART) model simulations were retained as the benchmark. Forward modeling and inverse fitting schemes were proposed for the sake of comparison. Results reveal that: 1) in the forward modeling scheme, from airborne measurements, the hybrid model performs better with RMSEs of 0.17℃, 1.57℃, and 0.38℃ for homogenous, row-planted vineyard and sparse forest scenes, respectively; the analytical model appears similar performant (0.17℃, 0.40 ℃) for the homogeneous and sparse forest scenes, but less performant (2.39℃) for the row-planted scene; 2) In the inverse fitting scheme, the uncertainties (95% of probability) of model coefficients and predicted directional anisotropies were considered. The kernel-driven model has fewer modeling constraints and statistically performs better for the homogeneous and sparse forest scenes with RMSEs of 0.07 ℃ and 0.19 ℃, respectively whereas it is less efficient for the row-planted scene with RMSE of 0.80 ℃. This study highlights the differences of accuracy between models of different complexity, and provides reference information for researchers to improve existing models and for users to choose their best modeling solution