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A High Geometric Albedo for LTT9779b Points Towards a Metal-rich Atmosphere and Silicate Clouds
No full textInternational audienceAims: In this work, we aim to confirm the high albedo of the benchmark ultrahot Neptune LTT9779b using 20 secondary eclipse measurements of the planet observed with CHEOPS. In addition, we perform a search for variability in the reflected light intensity of the planet as a function of time. Methods: First, we used the TESS follow-up data of LTT9779b from three sectors (2, 29, and 69) to remodel the transit signature and estimate an updated set of transit and ephemeris parameters, which were directly used in the modeling of the secondary eclipse lightcurves. This involved a critical noise-treatment algorithm, including sophisticated techniques such as wavelet denoising and Gaussian Process (GP) regression, to constrain noise levels from various sources. In addition to using the officially released reduced aperture photometry data from CHEOPS DRP, we also reduced the raw data using an independent PSF photometry pipeline, known as PIPE, to verify the robustness of our analysis. The extracted secondary eclipse lightcurves were modeled using the PYCHEOPS package, where we have detrended the background noise correlated with the spacecraft roll angle, originating from the inhomogeneous and asymmetric shape of the CHEOPS point spread function, using an N-order glint function. Results: Our independent lightcurve analyses have resulted in consistent estimations of the eclipse depths, with values of 89.913.7 ppm for the DRP analysis and 85.213.1 ppm from PIPE, indicating a high degree of statistical agreement. Adopting the DRP value yields a highly constrained geometric albedo of 0.730.11. No significant eclipse depth variability is detected down to a level of 37 ppm. Conclusions: Our results confirm that LTT9779b exhibits a strikingly high optical albedo, which substantially reduces the internal energy budget of the planet compared to more opaque..
Validation of the DESI DR2 Ly BAO analysis using synthetic datasets
No full textInternational audienceThe second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI), containing data from the first three years of observations, doubles the number of Lyman- (Ly) forest spectra in DR1 and it provides the largest dataset of its kind. To ensure a robust validation of the Baryonic Acoustic Oscillation (BAO) analysis using Ly forests, we have made significant updates compared to DR1 to both the mocks and the analysis framework used in the validation. In particular, we present CoLoRe-QL, a new set of Ly mocks that use a quasi-linear input power spectrum to incorporate the non-linear broadening of the BAO peak. We have also increased the number of realisations used in the validation to 400, compared to the 150 realisations used in DR1. Finally, we present a detailed study of the impact of quasar redshift errors on the BAO measurement, and we compare different strategies to mask Damped Lyman- Absorbers (DLAs) in our spectra. The BAO measurement from the Ly dataset of DESI DR2 is presented in a companion publication
Symbolic Regression and Differentiable Fits in Beyond the Standard Model Physics
No full textInternational audienceWe demonstrate the efficacy of symbolic regression (SR) to probe models of particle physics Beyond the Standard Model (BSM), by considering the so-called Constrained Minimal Supersymmetric Standard Model (CMSSM). Like many incarnations of BSM physics this model has a number (four) of arbitrary parameters, which determine the experimental signals, and cosmological observables such as the dark matter relic density. We show that analysis of the phenomenology can be greatly accelerated by using symbolic expressions derived for the observables in terms of the input parameters. Here we focus on the Higgs mass, the cold dark matter relic density, and the contribution to the anomalous magnetic moment of the muon. We find that SR can produce remarkably accurate expressions. Using them we make global fits to derive the posterior probability densities of the CMSSM input parameters which are in good agreement with those performed using conventional methods. Moreover, we demonstrate a major advantage of SR which is the ability to make fits using differentiable methods rather than sampling methods. We also compare the method with neural network (NN) regression. SR produces more globally robust results, while NNs require data that is focussed on the promising regions in order to be equally performant
High alpine preglacial caves modified by glacial processes and late condensationcorrosion in the Scerscen Valley (Valmalenco, Western Alps, Italy)
No full textInternational audienceThe Scerscen Valley (western Italian Alps) is home to caves at an altitude of around 2600 m, opening close to the Speleogenesis edge of a glacier. The aim of the research as part of a multi-disciplinary project was to reconstruct the evolution Alpine Cosmogenic GeomorphologyHydrogeologyglaciersburial dating of cosmonucleide some the of caves the related most burial recent to dating, the processes, geological recorded such and morphology paleoenvironmental as condensation-corrosion and micrometeorology, evolution and of sediment the carried area deposition. and out mineralogical to evaluate We the performed identifirole of cation by XRD, and hydrogeology using dye tracing and physical and chemical analyses. The cosmonucleide dating of quartz pebbles showed that the Veronica Cave is the oldest, with deposits dated at 1.3 ± 0.4 Ma, and possibly even older. It certainly formed at a much lower altitude (approx. 1300 m a.s.l. or lower) during the Alpine uplift. The Morgana and Marsooi caves, given the smaller volume of their phreatic conduits (1/3 of Veronica), are possibly more recent, formed during interglacials and evolved close to a glacial body. The caves initiated in dolomitic marble under the influence of sulfuric acid speleogenesis (SAS) due to pyrite oxidation. The conduits were then enlarged dramatically under phreatic conditions. The caves have evolved since their preglacial formation, with phases of filling by fluvio-glacial sediments and unclogging. Water tracing and physico-chemical analysis attest to a well-karstified aquifer, with rapid water circulation (>20 m/h) and low temperatures (~2 °C), draining towards the main spring, "La Prediletta", located at the foot of the dolomitic marbles. Microclimatic records (cave temperature and humidity) show seasonal cycles of condensation and evaporation, influenced by air exchanges with the outside atmosphere. These processes contributed to the formation of secondary minerals by evaporation (gypsum, hydromagnesite…) and, above all, to the significant enlargement of passages by the retreat of walls with characteristic morphologies (facets and grooved walls). The Scerscen caves bear witness to a long geological and climatic history, from their formation before the Mid-Pleistocene ice ages to their present-day evolution. They offer valuable insights into karst processes in the high mountains, and interactions between glaciers and aquifers
Long-term monitoring of coastal boulder deposits on Banneg Island: A good proxy for detection of extreme oceanic storms off West Brittany (France)
No full textInternational audienceCoastal boulder deposits (CBD) provide relevant information on coast-erosion wave events, -defined here as extreme events combining energetic storm wave and high spring tide level-, and are crucial for understanding giant storm wave impacts on coastal geomorphology. Banneg Island, located off the coast of Brittany (France), faces Atlantic storm waves that are not attenuated in this highly exposed area. This island is characterised by CBD resulting from the erosion of western cliffs, that have accumulated at the top of the island as a result of storm wave/inudation processes. These accumulations have been subjected to topo-morphological survey for the last two decades (using GNSS measurements from 2005-2012, and using UAV-based measurements since 2012). Hydrodynamic conditions (wave and water levels) were also analyzed. We used these data to analyse the frequency of extreme events over the last 20 years. The results show a good relationship between boulder transport (measured as volume of boulder displacement) and the frequency of extreme events inundating the island. Over the survey period, we found significant interannual variability in the occurrence of these extreme events, depending on winter weather conditions. This storminess variability is significantly correlated with the WEPA climatic index, calculated on the 3 winter months (December to February). Finally, the results from Banneg Island were compared with long-term monitoring carried out in other sectors along the coast of Brittany, to build a comprehensive picture of storminess and its impact on coastal change in Brittany over the last 20 years
Aetheras: Characterising exoplanetary atmospheric escape with NIR and UV spectroscopy
No full textInternational audienceTo date, many exoplanets have been discovered which exhibit distinct characteristics not observed within our own Solar System, raising numerous unresolved questions regarding their compositions, atmospheres, formation processes, and evolutionary pathways.Several missions have been dedicated to enhance the understanding of the exoplanets like James Webb and Hubble Space Telescopes. However, they have a limited spectral range and resolution to allow for a complete characterisation of atmospheric dynamics. The Aetheras mission proposal was developed at the Summer School Alpbach 2023 and presents a satellite mission to overcome these limitations to better understand the formation, evolution and characteristics of exoplanets. This mission aims to unravel key enigmas in contemporary</p
LiteBIRD Science Goals and Forecasts. -mode Anomalies
No full textInternational audienceVarious so-called anomalies have been found in both the WMAP and Planck cosmic microwave background (CMB) temperature data that exert a mild tension against the highly successful best-fit 6 parameter cosmological model, potentially providing hints of new physics to be explored. That these are real features on the sky is uncontested. However, given their modest significance, whether they are indicative of true departures from the standard cosmology or simply statistical excursions, due to a mildly unusual configuration of temperature anisotropies on the sky which we refer to as the "fluke hypothesis", cannot be addressed further without new information. No theoretical model of primordial perturbations has to date been constructed that can explain all of the temperature anomalies. Therefore, we focus in this paper on testing the fluke hypothesis, based on the partial correlation between the temperature and -mode CMB polarisation signal. In particular, we compare the properties of specific statistics in polarisation, built from unconstrained realisations of the CDM cosmological model as might be observed by the LiteBIRD satellite, with those determined from constrained simulations, where the part of the -mode anisotropy correlated with temperature is constrained by observations of the latter. Specifically, we use inpainted Planck 2018 SMICA temperature data to constrain the -mode realisations. Subsequent analysis makes use of masks defined to minimise the impact of the inpainting procedure on the -mode map statistics. We find that statistical assessments of the -mode data alone do not provide any evidence for or against the fluke hypothesis. However, tests based on cross-statistical measures determined from temperature and modes can allow this hypothesis to be rejected with a moderate level of probability
GW231123: Binary Black Hole Merger or Cosmic String?
No full textInternational audienceThe LIGO-Virgo-KAGRA Collaboration recently reported an exceptional gravitational-wave event, GW231123. This gravitational-wave signal was assumed to be generated from the merger of a binary black hole system, with source frame masses of and (90% credible intervals). As seen by the two LIGO detectors, the signal has only cycles, between 30 and 80 Hz, over ms. It is of critical importance to confirm the origin of this signal. Here we present the results of a Bayesian model comparison to test whether the gravitational-wave signal was actually generated by a binary black hole merger, or emitted from cusps or kinks on a cosmic string. We find significant evidence for a binary black hole merger origin of the signal
Hydrolytic weakening controls Jurassic to early Cretaceous mylonitisation in the basement of the Pyrenees
No full textInternational audienceThe age of the mylonite belts in the basement rocks of the Pyrenees is a subject of debate in the structural geology and petrology communities because of its potential implication on the regional tectono-thermal history and on the tectonic evolution of SW Europe. Here we address when and how mylonitisation took place in two key areas of the Eastern Pyrenees, where shear zones are associated with Giant Quartz Veins (GQVs). We conducted zircon U-Pb and muscovite 40 Ar/ 39 Ar dating coupled with structural, textural, and crystallographic preferred orientation (CPO) analyses of mylonites from the Cap de Creus and Canigó Massifs. U-Pb zircon dating of a dacite porphyry dyke crosscut by GQVs and mylonitic bands yields a maximum shear zone and GQV formation age of ca. 292 ± 3 Ma. 40 Ar/ 39 Ar analyses of muscovite within mylonitised GQVs yield initial crystallisation ages between ca. 164 and 188 Ma, as well as younger recrystallisation ages of ca. 110-118 Ma. A qualitative assessment of the GQV history is inferred from stepheating spectra of muscovite and quartz CPOs. The results indicate that GQV formation and mylonitisation were coupled, coeval, and long-lasting processes that took place from early Jurassic to early Cretaceous times. A comparative evaluation of quartz CPOs reveals inconsistencies regarding the strain distribution, quartz slip systems activity, and deformation temperatures depending on the deformed rock type. Quartz mylonites have stronger CPOs dominated by basal <a>, prism <a> or prism <c> slip systems, whilst phyllonites and granite mylonites show weaker fabrics mostly dominated by mixed <a> slip. This apparently suggests higher deformation temperatures in quartz mylonites than those inferred from more reliable proxies, such as mineral assemblages, brittle behaviour of K-feldspar, and fluid inclusion data. We suggest that the water-weakening effect caused by coeval formation and deformation of GQVs enabled easier dislocation glide and creep, allowing strain localisation and transitions between slip systems at lower temperatures than commonly inferred due to enhanced ductility. U-Pb zircon dating further suggests the existence of an early Carboniferous (ca. 332 ± 4 Ma; Visean) magmatic episode in the Pyrenees, in agreement with a cyclic, rather than a progressive, geodynamic history of the region during Variscan times.The present work challenges classical interpretations stating that Pyrenean mylonite belts developed during the retrograde stages of the Variscan Orogeny, highlighting that the structural evolution of this region during Mesozoic times deserves further investigation. Results have implications for interpreting deformation localisation mechanisms and conditions in crustal rocks, for the formation mechanisms of GQVs in worldwide orogenic belts, and for the tectono-thermal history of the Pyrenees since late-Variscan times.</div
Global drivers of variation in blood mercury of seabirds revealed by a meta-analysis
No full textInternational audienceMercury (Hg) is a global contaminant that biomagnifies in marine food webs. Seabirds can serve as valuable bioindicators of marine Hg pollution due to their high trophic positions and broad distributions. However, the biological and spatial drivers of variation in seabird Hg levels remain unclear, and few studies have validated whether seabird-derived estimates of the spatial distribution of Hg are consistent with predictions from biogeochemical-ocean models. We conducted a global meta-analysis of total Hg (THg) concentrations in adult seabird blood. Based on our own fieldwork and a literature review, we compiled 478 mean THg values from 108 species representing >11,000 individuals. Blood THg increased in species feeding at higher trophic levels, with larger body mass, and those more likely to consume mesopelagic prey in oceanic waters. Additionally, blood THg might further increase in regions with low chlorophyll-a level, likely due to greater methylmercury uptake in areas with low-productivity. We subsequently developed models to predict global spatial variation in seabird blood THg, either from all species or only epipelagic prey feeders. Only our epipelagic prey feeder-based model showed a weak significant positive correlation with THg in particulate organic matter from biogeochemical- ocean models. However, the low correlation coefficient (r =0.23) indicates potential discrepancies between the two models. We suggest that future studies adopt our integrative approach, combining biological data and large-scale modeling, to improve our understanding of global marine Hg pollution. Together, these findings clarify the biological and environmental drivers of Hg exposure in seabirds and highlight the value of seabirds for global monitoring of marine Hg pollution