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Search for Axion-Like Particles from Nearby Pre-Supernova Stars
No full textInternational audienceAxion-like particles (ALPs) are hypothetical pseudoscalar bosons that arise in many extensions of the Standard Model and are well-motivated dark matter candidates. Nearby massive stars in the late stages of stellar evolution provide a promising environment for enhanced ALP production due to their high core temperatures and densities. We search for a combined signal of ALP-induced hard X-ray and soft -ray emission from 18 nearby pre-supernova stars using the full public 22-year INTEGRAL/SPI dataset, construct individual stellar spectra and link them in a coherent analysis. A maximum-likelihood approach is used to extract fluxes in the 20--2000 keV energy range. Stellar evolution models are employed to obtain the expected spectral shapes of ALP production processes peaking between 50--500 keV, depending on stellar mass and evolutionary stage. We construct a joint likelihood that incorporates uncertainties in stellar parameters to derive combined constraints on the coupling constants and as a function of the ALP mass . The hard X-ray and soft -ray fluxes of all selected stars are consistent with zero within uncertainties. We provide upper limits on the continuum emission and on the 511 keV and 1809 keV line fluxes. The combined upper limit on is GeV (95% C.I.) while the ALP-photon coupling is constrained to GeV (95% C.I.) for eV, depending on the time to core collapse and magnetic field assumptions. Conservative limits of GeV (95% C.I.) are obtained assuming all but one star are in the early He-burning phase. These results rank among the strongest limits on ALP couplings to date and demonstrate the importance of soft -ray observations for probing ALPs and massive star evolution
Holocene climatic changes in the Kerguelen archipelago (South Indian Ocean) based on marine and lacustrine palaeoclimatic archives
No full textInternational audienceClimatic variability in the Southern Hemisphere is largely controlled by the latitudinal position of the Southern Hemisphere Westerly Winds (SHW), whose migration influences precipitation, temperature, and Antarctic upwelling. This study presents the results of analyses of two lacustrine sediment cores from Lake Armor, located on the subantarctic Kerguelen Islands (49 • 15′S, 69 • 10′E), within the SHW belt. Lipid biomarkers (Glycerol Dialkyl Glycerol Tetraethers, n-alkanes, and their hydrogen isotopes) were used to reconstruct mean annual air temperature above freezing (MAF) and humidity conditions. These records are compared with a high-resolution diatom-based summer sea surface temperature (SST) reconstruction from marine core MD11-3353, situated 150 km southwest of Lake Armor. In the late glacial and Early Holocene, our results reveal a period of warm air temperature, comparable to current values and very warm sea surface temperature, 5°C above the current values. Around 9000 cal a BP, an abrupt transition occurred, marked by a cooling of 5°C in SST and 1.5°C in MAF, interpreted as a northward migration of the SHW and associated oceanic fronts. The Mid-to-Late Holocene period is characterized by pronounced MAF variability, including a notably warm interval between 3000 and 2000 cal a BP, when n-alkane dD suggests the prevalence of wetter conditions. Since ~250 cal a BP, a southward migration of the SHW has produced a 2.5°C rise in MAF. Our findings are overall consistent with previous studies from the Indian Ocean, but permit us to go a step further as by comparing SSTs and air temperatures. This suggests that SST is not a reliable predictor of air temperature on the Kerguelen Islands, particularly during the Early Holocene. We hence argue that Kerguelen air temperature is predominantly controlled by the position of westerly winds, as an indicator of reorganisations in air mass trajectories
Exploring the freeze-in mechanism for scotogenic singlet dark matter
No full textInternational audienceWe present an exploratory study of the freeze-in mechanism within a scotogenic framework, where dark matter can either be a scalar singlet or a fermion singlet. Based on a random parameter scan, we show that large portions of the parameter space feature a dark matter relic density in agreement with the limits derived by Planck. Moreover, constraints related to lepton flavour violation are mostly respected within such parameter regions. Our study shows that it will be worth to further investigate the freeze-in mechanism within scotogenic frameworks
Understory plant indicator values poorly perform at monitoring temporal changes in French forest soil chemical properties
No full textInternational audienceUnderstory plant communities are widely used to infer soil conditions through species indicator values (IVs), scores reflecting species’ ecological preferences for factors such as soil acidity, moisture, or nutrient levels. While their reliability to describe soil conditions along spatial gradients is well established, their ability to capture temporal changes in soil chemistry remains largely untested at both temporal and geographical scales. We combined 26 years of vegetation monitoring with two French national soil surveys (1993–1997; 2007–2012) across 102 permanent forest plots to assess the reliability of community soil indices (CSIs) as bioindicators of soil pH, carbon-to-nitrogen ratio (C/N), and extractable phosphorus. CSIs were computed by averaging species IVs for each plot and survey. Temporal dynamics of measured soil properties and CSIs were analyzed using mixed-effects models at the national scale, while local trends were estimated separately for each plot to directly compare measured and vegetation-inferred changes. CSIs showed strong spatial correlations with measured pH and C/N, but weaker relationships for phosphorus. In contrast, no significant coupling was found between temporal changes in CSIs and measured soil parameters, with frequent mismatches in both direction and magnitude at the plot level. Measured soil dynamics were mainly driven by initial edaphic conditions and stand age, whereas CSI dynamics responded primarily to canopy openness and anthropogenic disturbances such tree harvesting. These findings confirm the value of IVs for spatial bioindication but highlight their limited sensitivity for detecting long-term soil changes, especially where soil changes remain modest
Sediment routing and palaeogeographic evolution of the Western Alpine Foreland Basin during the early collisional stage
No full textInternational audienceIn the Western Alpine Foreland Basin (WAFB), Late Eocene and Miocene periods were characterized by longitudinal sediment routing systems: The first one was situated within the turbidite basin during the underfilled phase and exhibited a northward orientation toward the Swiss Basin, whereas the second was located in the Rhône Valley during the overfilled phase and was directed southward toward the Mediterranean Sea. The transition between these two periods occurred during the Oligocene, which corresponds to both the underfilled/ overfilled transition and the early overfilled period. In this study, we provide new fieldwork observations, seismic and well data interpretations, biostratigraphic analyses and a literature synthesis to reconstruct the palaeogeographic and source-to-sink evolution of the WAFB from Priabonian to Aquitanian. The aim is to discuss this reorganisation of sediment routing in relation to the evolution of the Alpine orogenic wedge, as well as the structural inheritance and the suite of geodynamic events that affected southeastern France during the mid-Cenozoic. We divided the WAFB sedimentary formations into four depositional sequences (S1 to S4). During the deposition of the first two sequences (Priabonian to early late Rupelian; ~37.4-28.8 Ma), the WAFB routing system was influenced by the end of the Pyrenean-Provençal orogeny, the European Cenozoic Rifting System (controlling the Rhône Valley s.l.) and the Alpine orogenic wedge (controlling the Alpine foredeep). The very first connection between the Alpine domain and the Rhône Valley is established at ~30 Ma, during the late Rupelian (S2 highstand), controlled by E-W inherited Pyrenean-Provençal structures implying a 'broken foreland'. In the meanwhile, from the Dévoluy Basin and northward, the orogenic wedge controlled a classical, although thin, foreland basin characterized by a northward sediment routing connected to the Northern Alpine Foreland Basin. Most of the S3 sequence (Latest Rupelian to middle Chattian; ~28.8-23.25 Ma) corresponds to a decrease of clastic Alpine inputs throughout SE France caused by a reorganisation of the drainage network related with the exhumation of the southern External Crystalline Massifs. S3 highstand and S4 sequence (late Chattian to Aquitanian; from ~23.25 Ma) correspond to the establishment of a longitudinal sediment routing system in the Rhône Valley, with material flowing southwards toward the Gulf of Lion, and supplied by the Palaeo-Isère to the north and potentially by the Palaeo-Durance to the south. This final stage in the reorganisation of the drainage network is clearly associated with the post-rift phase of the Gulf of Lion, which facilitated the opening of a new sink and the ultimate southward migration of the sedimentary area
Search for gravitational waves emitted from SN 2023ixf
No full textInternational audienceWe present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19th, during the LIGO-Virgo-KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz where we assume the GW emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy and luminosity for a source emitting at 50 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as , at frequencies above Hz, surpassing results from SN 2019ejj
First evidence for direct CP violation in beauty to charmonium decays
No full textInternational audienceThe asymmetry and branching fraction of the CKM-suppressed decay are precisely measured relative to the favoured decay , using a sample of proton-proton collision data corresponding to an integrated luminosity of recorded at center-of-mass energy of during 2016--2018. The results of the asymmetry difference and branching fraction ratio are \begin{align*} \Delta\mathcal{A}^{C\!P} &\equiv \mathcal{A}^{C\!P}(B^+ \to J\mskip -3mu/\mskip -2mu\psi\,\pi^+) - \mathcal{A}^{C\!P}(B^+ \to J\mskip -3mu/\mskip -2mu\psi\,K^+) = (1.29 \pm 0.49 \pm 0.08) \times 10^{-2}, \end{align*}\begin{equation*} \mathcal{R}_{\pi/K} \equiv \frac{\mathcal{B}(B^+ \!\to J\mskip -3mu/\mskip -2mu\psi\,\pi^+)}{\mathcal{B}(B^+ \!\to J\mskip -3mu/\mskip -2mu\psi\,K^+)} = (3.852 \pm 0.022 \pm 0.018) \times 10^{-2}. \end{equation*} where the first uncertainties are statistical and the second systematic. A combination with previous LHCb results based on data collected at and in 2011 and 2012 yields and . The combined value deviates from zero by 3.2 standard deviations, providing the first evidence for direct violation in the amplitudes of beauty decays to charmonium final states
Study of in decays
No full textInternational audienceAn amplitude analysis of the transition is performed simultaneously in , , and decays. The study is based on a data sample of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of and TeV, corresponding to a total integrated luminosity of . A clear double-peak structure is observed in the spectrum of the decay. The data can be described either with a model including , and resonances, in which the contributions of and are unexpectedly large, or with a model including , a doubly charged open-charm tetraquark state and its isospin partner . If the former is considered implausible, the states are observed with high significance, and the data are consistent with isospin symmetry. When imposing isospin constraints between the two states, their mass and width are determined to be MeV and MeV, respectively, where the first uncertainty is statistical and the second is systematic. The mass is slightly below the threshold, and a spin-parity of is favoured with high significance
Visual attention matters during word recognition: A Bayesian modeling approach
No full textInternational audienceIt is striking that visual attention, the process by which attentional resources are allocated in the visual field so as to locally enhance visual perception, is a pervasive component of models of eye movements in reading, but is seldom considered in models of isolated word recognition. We describe BRAID, a new Bayesian word Recognition model with Attention, Interference and Dynamics. As most of its predecessors, BRAID incorporates three sensory, perceptual and orthographic knowledge layers together with a lexical membership submodel. Its originality resides in also including three mechanisms that modulate letter identification within strings: an acuity gradient, lateral interference and visual attention. We calibrated the model such that its temporal scale was consistent with behavioral data, and then explored the model's capacity to generalize to other, independent effects. We evaluated the model's capacity to account for the word length effect in lexical decision, for the optimal viewing position effect and for the interaction of crowding and frequency effects in word recognition. We further examined how these effects were modulated by variations in the visual attention distribution. We show that visual attention modulates all three effects and that a narrow distribution of visual attention results in performance patterns that mimic those reported in impaired readers. Overall, the BRAID model could be conceived as a core building block, towards the development of integrated models of reading aloud and eye movement control, or of visual recognition of impaired readers, or any context in which visual attention does matter
