The Chinese-French SVOM mission for GRBs studies

We present the SVOM (Space-based multi-band astronomical Variable Objects Monitor) mission that the Chinese National Space Agency and the French Space Agency have decided to jointly implement. SVOM has been designed to detect all known types of gamma-ray bursts (GRBs), to provide fast and reliable GRB positions, to measure the broadband spectral shape and temporal properties of the GRB prompt emission, and to quickly identify the optical/near-infrared afterglows of detected GRBs, including high-redshift ones. Scheduled to be in orbit in the second half of the present decade, the SVOM satellite will carry a very innovative scientific payload combining for the first time a wide field X- and gamma-ray coded mask imager for GRB real-time localizations to few arcmin, a non-imaging gamma-ray monitor, and two narrow-field instruments for the study of the GRB early afterglow emission in the X-ray and visible bands. The SVOM payload is complemented by ground-based instruments including a wide-field camera to catch the GRB prompt emission in the visible band and two robotic telescopes to measure the photometric properties of the early afterglow. A particular attention is paid to the GRB follow-up in facilitating the observation of the SVOM detected GRB by the largest ground based telescopes.Comment: 13 pages, 3 figures. To appear in a special issue of Comptes Rendus Physique "GRB studies in the SVOM era", Eds. F. Daigne, G. Dubu

Search for non-standard neutrino interactions with 10 years of ANTARES data

Non-standard interactions of neutrinos arising in many theories beyond the Standard Model can significantly alter matter effects in atmospheric neutrino propagation through the Earth. In this paper, a search for deviations from the prediction of the standard 3-flavour atmospheric neutrino oscillations using the data taken by the ANTARES neutrino telescope is presented. Ten years of atmospheric neutrino data collected from 2007 to 2016, with reconstructed energies in the range from ~16 GeV to 100 GeV, have been analysed. A log-likelihood ratio test of the dimensionless coefficients eµt and ett-eµµ does not provide clear evidence of deviations from standard interactions. For normal neutrino mass ordering, the combined fit of both coefficients yields a value 1.7s away from the null result. However, the 68% and 95% confidence level intervals for eµt and ett-eµµ, respectively, contain the null value. Best fit values, one standard deviation errors and bounds at the 90% confidence level for these coefficients are given for both normal and inverted mass orderings. The constraint on eµt is among the most stringent to date and it further restrains the strength of possible non-standard interactions in the µ-t sector.Postprint (published version

SN 1994W: An Interacting Supernova or Two Interacting Shells?

We present a multi-epoch quantitative spectroscopic analysis of the Type IIn SN 1994W, an event interpreted by Chugai et al. as stemming from the interaction between the ejecta of a SN and a 0.4Msun circumstellar shell ejected 1.5yr before core collapse. During the brightening phase, our models suggest that the source of optical radiation is not unique, perhaps associated with an inner optically-thick Cold Dense Shell (CDS) and outer optically-thin shocked material. During the fading phase, our models support a single source of radiation, an hydrogen-rich optically-thick layer with a near-constant temperature of ~7000K that recedes from a radius of 4.3x10^15 at peak to 2.3x10^15cm 40 days later. We reproduce the hybrid narrow-core broad-wing line profile shapes of SN 1994W at all times, invoking an optically-thick photosphere exclusively (i.e., without any external optically-thick shell). In SN 1994W, slow expansion makes scattering with thermal electrons a key escape mechanism for photons trapped in optically-thick line cores, and allows the resulting broad incoherent electron-scattering wings to be seen around narrow line cores. In SNe with larger expansion velocities, the thermal broadening due to incoherent scattering is masked by the broad profile and the dominant frequency redshift occasioned by bulk motions. Given the absence of broad lines at all times and the very low 56Ni yields, we speculate whether SN 1994W could have resulted from an interaction between two ejected shells without core collapse. The high conversion efficiency of kinetic to thermal energy may not require a SN-like energy budget for SN1994W.Comment: 36 pages (includes online tables), 16 figures, paper accepted to MNRAS, discussion section expanded, title re-worde

CAGIRE: a wide-field NIR imager for the COLIBRI 1.3 meter robotic telescope

The use of high energy transients such as Gamma Ray Bursts (GRBs) as probes of the distant universe relies on the close collaboration between space and ground facilities. In this context, the Sino-French mission SVOM has been designed to combine a space and a ground segment and to make the most of their synergy. On the ground, the 1.3 meter robotic telescope COLIBRI, jointly developed by France and Mexico, will quickly point the sources detected by the space hard X-ray imager ECLAIRs, in order to detect and localise their visible/NIR counterpart and alert large telescopes in minutes. COLIBRI is equipped with two visible cameras, called DDRAGO-blue and DDRAGO-red, and an infrared camera, called CAGIRE, designed for the study of high redshift GRBs candidates. Being a low-noise NIR camera mounted at the focus of an alt-azimutal robotic telescope imposes specific requirements on CAGIRE. We describe here the main characteristics of the camera: its optical, mechanical and electronics architecture, the ALFA detector, and the operation of the camera on the telescope. The instrument description is completed by three sections presenting the calibration strategy, an image simulator incorporating known detector effects, and the automatic reduction software for the ramps acquired by the detector. This paper aims at providing an overview of the instrument before its installation on the telescope.Comment: Accepted by Experimental Astronom

Superstelle in esplosione: fare cosmologia con le supernovae e i gamma-ray burst

Le supernovae e i gamma-ray burst, gli eventi più catastrofici che si verificano nell’Universo, sono oggetto di studio nei campi più dinamici della moderna ricerca astronomica. Dei secondi ancora non conosciamo con precisione i meccanismi che li innescano e tuttavia forti indizi suggeriscono che, come nelle supernovae, la causa scatenante sia il collasso esplosivo di stelle di grande massa. Nell’ultimo decennio, questi fenomeni sono diventati strumenti molto efficaci nello studio dell’origine e dell’evoluzione dell’Universo. I cosmologi li utilizzano come "fari" cosmici che illuminano i loro immediati dintorni e anche come sonde per ricostruire la dinamica dell’espansione dell’Universo. Grazie ad essi, oggi sappiamo che circa il 70% del contenuto di energia-materia dell’Universo è costituito di un’energia oscura la cui natura ci è ancora completamente ignota. Questo libro getta un po’ di luce sui curiosi destini delle superstelle in esplosione e sulle affascinanti conclusioni cosmologiche che possiamo trarre dalla loro osservazione

Exploding superstars: understanding supernovae and gamma-ray bursts

The exceptional cosmic history and the fabulous destinies of exploding stars – supernovae and gamma-ray bursters – are highly fertile areas of research and are also very special tools to further our understanding of the universe. In this book, cosmologists Dr Alain Mazure and Dr Stéphane Basa throw light on the assemblage of facts, hypotheses and cosmological conclusions and show how these ‘beacons’ illuminate their immediate surroundings and allow us to study the vast cosmos, like searchlights revealing the matter comprising our universe