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Modelling approaches for assessing the possibilities of re-locating vegetable supply of public schools - learning from Guadeloupe Island
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Origin of Phobos and Deimos: Orbital Evolution Shortly after Formation from a Potential Dislocation
No full textInternational audienceThis paper deals with the formation and evolution of Mars' moons, Phobos and Deimos, assuming the dislocation of a larger progenitor as the origin of these moons. The study by R. Hyodo et al. argues that under somewhat simplistic modeling, the postdislocation orbits of Phobos and Deimos inevitably collide within 10,000 yr, leading to their mutual annihilation. These findings are based on -body simulations, accounting for Mars' J2 and J4 gravitational perturbations and mutual perturbations between the moons. In this paper, we challenge these findings by extending their work. We incorporate important perturbations such as solar perturbations, Mars' axial precession and nutation, and its deformation along three axes. We also extend some of the hypotheses made by R. Hyodo et al. concerning the initial distribution of Phobos and Deimos after the dislocation. Our analysis reveals that including these additional perturbations, as well as the possibility of having more than two fragments after the dislocation, does not alter the ultimate fate of Phobos and Deimos. The moons still converge towards collision within comparable timescales, supporting R. Hyodo et al.'s conclusions that the dislocation hypothesis under the dynamical scenario developed by A. Bagheri et al. has, in the best conditions, about a 10% chance of surviving after the first 100,000 yr following their formation
Neutrino non-radiative decay in matter: constraints and prospects
No full textInternational audienceNeutrinos, being massive, can decay. A heavier neutrino could decay into a lighter one and a massless scalar or pseudoscalar boson, such as the Majoron. Two-body non-radiative decay could occur in dense matter, such as in the inner dense regions of a core-collapse supernova. We first derive novel bounds on neutrino-Majoron couplings using the spectral distortions induced by neutrino non-radiative two-body decay in matter, and two-dimensional likelihood analyses of the 24 events from SN1987A. We then explore the prospects of neutrino-Majoron couplings from a future galactic core-collapse supernova, leaving either a neutron star or a black-hole. To this aim, we use information from detailed one-dimensional supernova simulations. We consider the supernova neutrino signal associated with inverse-beta decay in the upcoming JUNO and Hyper-Kamiokande detectors, with neutrino-argon scattering in DUNE, or with coherent neutrino-nucleus scattering in the DARWIN experiment. In a full 3 framework, based on the spectral distortions induced by neutrino decay in matter, we perform two-dimensional likelihood analyses and provide prospects for the limits on neutrino-Majoron couplings. Our results show that the observation of a future supernova will significantly improve on the current bounds, in particular from SN1987A and neutrinoless double-beta decay. Finally, we explore the impact of neutrino decay in matter on the diffuse supernova neutrino background formed by past supernova explosions. We show for the first time that the effects on black-hole contributions are important and modify the DSNB number of events by several tens of percent in Hyper-Kamiokande
Improved upper limits on the 21-cm signal power spectrum at and from an optimal field observed with NenuFAR
No full textInternational audienceWe report the deepest upper limits to date on the power spectrum of the 21-cm signal during the Cosmic Dawn (redshifts: z>15), using four nights of observations with the NenuFAR radio interferometer. The limits are derived from two redshift bins, centred at and , with integration times of 26.1 h and 23.6 h, from observations of an optimal target field chosen to minimise sidelobe leakage from bright sources. Our analysis incorporates improvements to the data processing pipeline, particularly in subtracting strong radio sources in the primary beam sidelobes and mitigating low-level radio frequency interference, yielding a 50-fold reduction in the excess variance compared to a previous analysis of the north celestial pole field. At , we achieve a best upper limit of Δ^{2}_{21}<4.6 \times 10^5 \, \textrm{mK}^{2} at , while at , the best limit is Δ^{2}_{21}<5.0 \times 10^6 \, \textrm{mK}^{2} at . These are the strongest constraints on the 21-cm power spectrum at the respective redshifts, with the limit at being deeper by more than an order of magnitude over all previous Cosmic Dawn power spectrum limits. Comparison against simulated exotic 21-cm signals shows that while the limits begin to exclude the most extreme models predicting signals stronger than the EDGES detection, an order-of-magnitude improvement would constrain signals compatible with EDGES. A coherence analysis reveals that the excess variance is largely incoherent across nights for the redshift bin, suggesting that deeper integrations could yield significantly stronger constraints on the 21-cm signal from the Cosmic Dawn
Search for the Higgs boson decay to a boson and a photon in collisions at TeV and TeV with the ATLAS detector
No full textInternational audienceA search for the Higgs boson decay to a boson and a photon in the () final state is performed using collisions at TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022-2024, corresponding to an integrated luminosity of 165 fb. The signal yield, normalised to the Standard Model prediction, is measured to be , compared to an expected value of . This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations for the background-only hypothesis. This result is combined with that of a similar search performed with 140 fb of TeV collisions to provide the most stringent expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of (), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation
Bursty acceleration and 3D trajectories of electrons in a solar flare
No full textInternational audienceContext. During a solar flare, electrons are accelerated to non-thermal energies as a result of magnetic reconnection. These electrons then propagate upwards and downwards from the energy release site along magnetic field lines and produce radio and X-ray emission. Aims. On 11 November 2022, an M5.1 solar flare was observed by the Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter together with various ground-and space-based radio instruments. The flare was associated with several fine hard X-ray (HXR) structures and a complex set of metric radio bursts (type III, J, and narrowband). By studying the evolution of X-ray, extreme ultraviolet, and radio sources, we aim to study the trajectories of the flare-accelerated electrons in the lower solar atmosphere and low corona. Methods. We used observations from the STIX on board Solar Orbiter to study the evolution of X-ray sources. Using radio imaging from the Nançay Radio heliograph (NRH) and the Newkirk density model, we constructed 3D trajectories of 14 radio bursts. Results. Imaging of the HXR fine structures shows several sources at different times. The STIX and NRH imaging shows correlated changes in the location of the HXR and radio source at the highest frequency during the most intense impulsive period. Imaging and 3D trajectories of all the bursts show that electrons are getting accelerated at different locations and along several distinct field lines. Some of the trajectories from the same origin show expansion on the order of 4 over a height of ∼110 Mm. The longitude and latitude extent of the trajectories are ∼30 and ∼152 . Conclusions. We find that the electrons producing HXR and radio emission have similar acceleration origins. Importantly, our study supports the scenario that the flare acceleration process is temporally and spatially fragmentary, and during each of these small-scale processes, the electron beams are injected into a very fibrous environment and produce complex HXR and radio emission.</div
Characterization of low energy argon recoils with ReD and ReD+
No full textInternational audienceThe Recoil Directionality project (ReD) within the DarkSide-20k Collaboration characterizedthe response of a liquid argon (LAr) dual-phase Time Projection Chamber (TPC) to neutron induced nuclear recoils,to measure the ionization yield at low-energy. The ionization yield is a critical parameter for the experiments searchingfor Dark Matter in the form of low-mass WIMPs and measurements in Ar below 10 keV are scarce in theliterature. ReD was designed to cover the gap down to 2 keV. The ReD data taking took place in 2023 at the INFNSezione di Catania. The TPC was irradiated by neutrons from an intense Cf fission source in orderto produce Ar recoils inthe energy range of interest. The energy of the nuclear recoils produced within the TPC by (n,n')scattering was determined by detecting the outgoing neutrons with a dedicated neutron spectrometermade of 18 plastic scintillators. The kinetic energy of neutrons interacting in the TPC was evaluatedevent-by-event by measuring the time of flight. ReD collected and characterized a sample of nuclearrecoils down to 2 keV, thus meeting its design goal.The ReD effort will be further extended by a new project, ReD+, funded by a PRIN grant from theItalian Ministry of Research. ReD+ is designed to push the sensitivity down to 0.5 keV, by using thesame conceptual design of ReD and improved components. A new TPC is being re-designed andoptimized in order to increase the signal rate and the signal-to-background ratio, which limited thesensitivity of ReD
Simulation-based population inference of LISA's Galactic binaries: Bypassing the global fit
No full textInternational audienceThe Laser Interferometer Space Antenna (LISA) is expected to detect thousands of individually resolved gravitational wave sources, overlapping in time and frequency, on top of unresolved astrophysical and/or primordial backgrounds. Disentangling resolved sources from backgrounds and extracting their parameters in a computationally intensive "global fit" is normally regarded as a necessary step toward reconstructing the properties of the underlying astrophysical populations. Here, we show that it is possible to infer the properties of the most numerous population of LISA sources - Galactic double white dwarfs - directly from the frequency (or, equivalently, time) strain series, by using a simulation-based approach that bypasses the global fit entirely. By training a normalizing flow on a custom-designed compression of simulated LISA frequency series from the Galactic double white dwarf population, we demonstrate how to infer the posterior distribution of population parameters (e.g., mass function, frequency, and spatial distributions). This allows for extracting information on the population parameters from both resolved and unresolved sources simultaneously and in a computationally efficient manner. Our approach to target population properties directly can be readily extended to other source classes (e.g., massive and stellar-mass black holes, extreme mass ratio inspirals), provided fast simulations are available, and to scenarios involving non-Gaussian or non-stationary noise (e.g., data gaps)
3C 403: a candidate neutrino-emitting radio galaxy
No full textInternational audience3C 403 is a well known FRII radio galaxy, whose jets extend up to the kpc scale. In this letter, we present its identification as the second most significant source among the more than 150 inspected using the 15-year neutrino dataset of the ANTARES Collaboration, possibly making it the first radio galaxy with neutrino emission. Following the previous association of blazars with netrinos events, we aimed at studying the jet properties and its possible role in neutrino production. We collected multi-scale radio observations to assess the properties of the jet from the kpc to pc scale. Moreover, the high-energy properties of its AGN were inspected. Through the analysis of the jet orientation on the different scales, we verified that neither the inner nor the extended jet seems to have a viewing angle close to the line of sight. Instead, the jet seems to lie on the plane of the sky. In addition, we tested the recently proposed scaling relation between neutrino and hard X-rays fluxes, identified for blazars and Seyfert galaxies, against the measured fluxes for 3C 304. We found that the source lies in the region between blazars and Seyferts, altough the current upper limit on neutrino flux does not allow us to be conclusive on the correlation. In these regards, 3C 403 is an intermediate case between the previous cases of neutrino associations, providing a useful test case for future models
Onset of strong Iceland-Scotland overflow water 3.6 million years ago
No full textInternational audienceNorth Atlantic Deep Water (NADW), the return flow component of the Atlantic Meridional Overturning Circulation (AMOC), is a major inter-hemispheric ocean water mass with strong climate effects but the evolution of its source components on million-year timescales is poorly known. Today, two major NADW components that flow southward over volcanic ridges to the east and west of Iceland are associated with distinct contourite drift systems that are forming off the coast of Greenland and on the eastern flank of the Reykjanes (mid-Atlantic) Ridge. Here we provide direct records of the early history of this drift sedimentation based on cores collected during International Ocean Discovery Programme (IODP) Expeditions 395C and 395. We find rapid acceleration of drift deposition linked to the eastern component of NADW, known as Iceland–Scotland Overflow Water at 3.6 million years ago (Ma). In contrast, the Denmark Strait Overflow Water feeding the western Eirik Drift has been persistent since the Late Miocene. These observations constrain the long-term evolution of the two NADW components, revealing their contrasting independent histories and allowing their links with climatic events such as Northern Hemisphere cooling at 3.6 Ma, to be assessed