The ANTARES collaboration has performed a series of in-situ measurements to study the background light for a planned undersea neutrino telescope. Such background can be caused by
40
K
decays or by ...biological activity. We report on measurements at two sites in the Mediterranean Sea at depths of 2400 m and 2700 m, respectively. Three photomultiplier tubes were used to measure single counting rates and coincidence rates for pairs of tubes at various distances. The background rate is seen to consist of three components: a constant rate due to
40
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decays, a continuum rate that varies on a time scale of several hours simultaneously over distances up to at least 40 m, and random bursts a few seconds long that are only correlated in time over distances of the order of a meter. A trigger requiring coincidences between nearby photomultiplier tubes should reduce the trigger rate for a neutrino telescope to a manageable level with only a small loss in efficiency.
ANTARES is a project leading towards the construction and deployment of a neutrino telescope in the deep Mediterranean Sea. The telescope will use an array of photomultiplier tubes to detect the ...Cherenkov light emitted by muons resulting from the interaction with matter of high energy neutrinos. In the vicinity of the deployment site the ANTARES Collaboration has performed a series of in situ measurements to study the change in light transmission through glass surfaces during immersions of several months. The average loss of light transmission is estimated to be only ∼2% at the equator of a glass sphere one year after deployment. It decreases with increasing zenith angle, and tends to saturate with time. The transmission loss, therefore, is expected to remain small for the several year lifetime of the ANTARES detector whose optical modules are oriented downwards. The measurements were complemented by the analysis of the
210Pb activity profile in sediment cores and the study of biofouling on glass plates. Despite a significant sedimentation rate at the site, in the 0.02–0.05 cm
yr
−1 range, the sediments adhere loosely to the glass surfaces and can be washed off by water currents. Further, fouling by deposits of light-absorbing particulates is only significant for surfaces facing upwards.
The recently commissioned Dark Energy Spectroscopic Instrument (DESI) will measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million ...galaxies and quasars over 14000 sqdeg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope delivers light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with LPNHE (CNRS, IN2P3, Sorbonne Université and Université de Paris) and the WINLIGHT Systems company based in Pertuis (France), were in charge of integrating and validating the performance requirements of the ten full spectrographs, equipped with their cryostats, shutters and other mechanisms. We present a summary of our activity which allowed an efficient validation of the systems in a short-time schedule. We detail the main results. We emphasize the benefits of our approach and also its limitations.
Since July 2014, the ESA Gaia mission has been surveying the entire sky down to magnitude 20.7 in the visible. In addition to the millions of stars, thousands of Solar System Objects (SSOs) are ...observed daily. By comparing their positions to those of known objects, a daily processing pipeline filters known objects from potential discoveries. However, owing to Gaia's specific scanning law designed for stars, potential newly discovered moving objects are characterized by very few observations, acquired over a limited time. This aspect was recognized early in the design of the Gaia data processing. A daily processing pipeline dedicated to these candidate discoveries was set up to release calls for observations to a network of ground-based telescopes. Their aim is to acquire follow-up astrometry and to characterize these objects. From the astrometry measured by Gaia, preliminary orbital solutions are determined, allowing to predict the position of these potentially new discovered objects in the sky accounting for the large parallax between Gaia and the Earth (separated by 0.01 au). A specific task within the Gaia Consortium has been responsible for the distribution of requests for follow-up observations of potential Gaia SSO discoveries. Since late 2016, these calls for observations (called alerts) are published daily via a Web interface, freely available to anyone world-wide. Between November 2016 and July 2020, over 1700 alerts have been published, leading to the successful recovery of more than 200 objects. Among those, six have provisional designation assigned with the Gaia observations, the others being previously known objects with poorly characterized orbits, precluding identification at the time of Gaia observations. There is a clear trend for objects with a high inclination to be unidentified, revealing a clear bias in the current census of SSOs against high inclination populations.
Aims. We investigate the stellar and circumstellar properties of the bright southern T Tauri star RY Lup, a G-type star showing type III variability. Methods. We report simultaneous BV polarimetric ...and UBV photometric observations obtained during 12 consecutive nights on the 1.0 m and 50 cm telescopes of the European Southern Observatory at La Silla. We compare these data to models. Results. The polarization is high (≈3.0%) when the star is faint and red ($V \approx 12.0$, $B-V \approx 1.3$), and it is low (≈0.5%) when it is bright and bluer ($V \approx 11.0$, $B-V \approx 1.1$). The photometric and polarimetric variations share a common period of 3.75 d. Irregular light variations, larger at shorter wavelengths, are also superposed on the cyclic variations and may be due to processes different than the one producing the periodic variations. The linear polarization is produced by dust scattering in an asymmetric (flat) circumstellar envelope. The photometric and polarimetric variations can be explained with an almost edge-on circumstellar disk that is warped close to the star, where it interacts with the star's magnetosphere. The inhomogeneous disk matter contained in the warp corotates with the star and partially occults it during part of the rotation period, which explains the dips in luminosity and the accompanying increase in polarization. All the information available on RY Lup is consistent with a system comprising a G8 star surrounded by an edge-on disk, and we find that the mass of RY Lup is $M_{\rm star}/M_{\odot}= 1.71 \pm 0.43$, while its age is $(1.2\pm 0.4) \times 10^7 \rm{yr}$.
The ANTARES Collaboration is operating the largest water Cherenkov neutrino telescope in the Northern hemisphere, installed in the Mediterranean Sea. One of the objectives of ANTARES is the search ...for neutrinos produced in self-annihilation of Dark Matter particles. The results on the search for Dark Matter annihilations in the Sun and in the Galactic Centre with the data recorded between 2007 and 2012 are presented. The search on the Sun has resulted in competitive limits on the WIMP-proton cross-section, and they are compared to the ones of other indirect and direct detection experiments as well as to predictions of SUSY models. Results of ANTARES on Dark Matter searches towards the Galactic Centre have concluded with competitive limits on the annihilation cross-sections for high mass WIMPs that disfavours the interpretation of the PAMELA electron/positron excesses (constrained by Fermi-LAT and H.E.S.S.) as a signal from dark matter self-annihilations.
The Provence Adaptive optics Pyramid Run System (PAPYRUS) is a pyramid-based Adaptive Optics (AO) system that will be installed at the Coude focus of the 1.52m telescope (T152) at the Observatoire de ...Haute Provence (OHP). The project is being developed by PhD students and Postdocs across France with support from staff members consolidating the existing expertise and hardware into an R&D testbed. This testbed allows us to run various pyramid wavefront sensing (WFS) control algorithms on-sky and experiment on new concepts for wavefront control with additional benefit from the high number of available nights at this telescope. It will also function as a teaching tool for students during the planned AO summer school at OHP. To our knowledge, this is one of the first pedagogic pyramid-based AO systems on-sky. The key components of PAPYRUS are a 17x17 actuators Alpao deformable mirror with a Alpao RTC, a very low noise camera OCAM2k, and a 4-faces glass pyramid. PAPYRUS is designed in order to be a simple and modular system to explore wavefront control with a pyramid WFS on sky. We present an overview of PAPYRUS, a description of the opto-mechanical design and the current status of the project.
A project has been approved by the ATLAS Collaboration for the design and implementation of a Data Acquisition and Event Filter prototype, based on the functional architecture described in the ATLAS ...Technical Proposal. The prototype consists of a full “vertical” slice of the ATLAS Data Acquisition and Event Filter architecture, including all the hardware and software elements of the data flow, its control and monitoring as well as all the elements of a complete on-line system. This paper outlines the project, its goals, structure, schedule and current status and describes details of the system architecture and its components.
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