| 6411. |
- Becherini, Yvonne, et al.
(författare)
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HESS-II reconstruction strategy and performance in the low-energy (20-150 GeV) domain
- 2009
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Ingår i: HIGH ENERGY GAMMA-RAY ASTRONOMY. - : American Institute of Physics (AIP). - 9780735406162 ; , s. 738-741
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Konferensbidrag (refereegranskat)abstract
- In mid-2009 a notable upgrade of the H.E.S.S. telescope system will take place: a new telescope with a 600 m(2) mirror area and very-high-resolution camera (0.07 degrees) will be positioned at the centre of the present configuration, with the aim of lowering the threshold and enhance its sensitivity in the 100 GeV to several TeV energy range. HESS-II will permit the investigation of the lower energy gamma-ray spectra in various cosmic accelerators, giving information on the origin of the gamma-rays observed, and will detect AGNs with a redshift greater than 0.2 (being less affected by absorption by Extragalactic Background Light - EBL - in this energy range) and will search for new classes of very high energy gamma-ray emitters (pulsars, microquasars, GRB, and dark matter candidates).
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| 6412. |
- Becherini, Yvonne, et al.
(författare)
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Status report of the ANTARES experiment
- 2006
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Ingår i: Taup 2005. - : IOP Publishing. ; , s. 444-446
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Konferensbidrag (refereegranskat)abstract
- The ANTARES Collaboration is building an underwater neutrino telescope in the Mediterranean sea. The telescope is designed to search for high energy (E > I TeV) galactic and extra-galactic neutrino sources, but could also be sensitive to neutrinos originating from the decay of neutralino and exotic particles. The detector is a 3-dimensional array of photomultipliers located at a depth of 2500 m, 40 km from the La Seyne sur Mer shore (near Toulon, France). During the year 2005 a full scale test line and an instrumented line have been successfully operated. In the winter '05-'06 the first full 480 m line will be deployed and connected to the shore station.
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| 6413. |
- Becherini, Yvonne
(författare)
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The ANTARES neutrino telescope
- 2003
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Ingår i: Neutrino Physics. - Amsterdam : IOS Press. ; , s. 275-279
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 6414. |
- Becherini, Yvonne, et al.
(författare)
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The CoMET multiperspective event tracker for wide field-of-view gamma-ray astronomy
- 2022
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Ingår i: Proceedings of Science. - : Scuola Internazionale Superiore di Studi Avanzati (SISSA).
-
Konferensbidrag (refereegranskat)abstract
- The ALTO project aims to build a particle detector array for very high energy gamma ray observations optimized for soft spectrum sources. The accurate reconstruction of gamma ray events, in particular their energies, using a surface array is an especially challenging problem at the low energies ALTO aims to optimize for. In this contribution, we leverage Convolutional Neural Networks (CNNs) to improve reconstruction performance at lower energies ( smaller 1 TeV ) as compared to the SEMLA analysis procedure, which is a more traditional method using mainly manually derived features.rnWe present performance figures using different network architectures and training settings, both in terms of accuracy and training time, as well as the impact of various data augmentation techniques.
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| 6415. |
- Becherini, Yvonne, et al.
(författare)
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Time correlations of high energy muons in an underground detector
- 2005
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Ingår i: Astroparticle physics. - : Elsevier. - 0927-6505 .- 1873-2852. ; 23:3, s. 341-348
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Tidskriftsartikel (refereegranskat)abstract
- We present the result of a search for correlations in the arrival times of high energy muons collected from 1995 till 2000 with the streamer tube system of the complete MACRO detector at the underground Gran Sasso Lab. Large samples of single muons (8.6 million), double muons (0.46 million) and multiple muons with multiplicities from 3 to 6 (0.08 million) were selected. These samples were used to search for time correlations of cosmic ray particles coming from the whole upper hemisphere or from selected space cones. The results of our analyses confirm with high statistics a random arrival time distribution of high energy cosmic rays. (c) 2005 Elsevier B.V. All rights reserved.
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| 6416. |
- Becherini, Yvonne, et al.
(författare)
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Time variations in the deep underground muon flux measured by MACRO
- 2005
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Ingår i: 29th International Cosmic Ray Conference. - Mumbai : Tata Institute of Fundamental Research. ; , s. 157-160
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- More than 30 million high-energy muons collected with the MACRO detector at the underground Gran Sasso Laboratory have been used to search for flux variations of different nature. Two kinds of studies were carried out: search for periodical variations and for the occurrence of clusters of events. Different analysis methods, including Lomb-Scargle spectral analysis and scan statistics have been applied to the data.
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| 6417. |
- Becherini, Yvonne, et al.
(författare)
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Very-High-Energy gamma-ray astronomy with the ALTO observatory
- 2018
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Ingår i: 35th International Cosmic Ray Conference;ICRC2017, Busan, Korea, July 10-20, 2017. - Trieste : Sissa Medialab.
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Konferensbidrag (refereegranskat)abstract
- ALTO is a concept/project in the exploratory phase since 2013 aiming to build a wide-field Very-High-Energy gamma-ray observatory at very high altitude in the Southern hemisphere. The operation of such an observatory will complement the Northern hemisphere observations performed by HAWC and will make possible the exploration of the central region of our Galaxy and the hunt for PeVatrons, and to search for extended Galactic objects such as the Vela Supernova Remnant and the Fermi bubbles. The ALTO project is aiming for a substantial improvement of the Water Cherenkov Detection Technique by increasing the altitude of the observatory in order to lower the energy threshold, by using a layer of scintillator below the water tank to optimize the signal over background discrimination, by minimizing the size of the tanks and having a more compact array to sample the air-shower footprints with better precision, and by using precise electronics which will provide time-stamped waveforms to improve the angular and energy resolution. ALTO is designed to have as low an energy threshold as possible so as to act as a fast trigger alert to other observatories -- primarily to the Southern part of CTA -- for transient Galactic and extra-galactic phenomena. The wide field-of-view resulting from the detection technique allows the survey of a large portion of the sky continuously, thus giving the possibility to access emission from Gamma-Ray Bursts, Active Galactic Nuclei and X-ray binary flares, and extended emissions of both Galactic (Vela SNR, Fermi bubbles) and extra-galactic (AGN radio lobes) origin. The ALTO observatory will be composed of about a thousand detection units, each of which consists of a Water Cherenkov Detector positioned above a liquid Scintillation Detector, distributed within an area of about 200 m in diameter. The project is in the design study phase which is soon to be followed by a prototyping phase. The ALTO concept, design study and expected sensitivity together with the prototype status and plans for final deployment in the Southern hemisphere will be the subjects of this presentation.
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| 6418. |
- Beck, Melanie, et al.
(författare)
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SPECTROPOLARIMETRY CONFIRMS CENTRAL POWERING IN A Ly alpha NEBULA AT z=3.09
- 2016
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 818:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a follow-up study to the imaging polarimetry performed by Hayes et al. on LAB1 in the SSA22 protocluster region. Arguably the most well-known Ly alpha blob, this radio-quiet emission-line nebula likely hosts a galaxy that. either is. undergoing significant star formation or hosts an active galactic nucleus, or both. We obtain deep, spatially resolved spectropolarimetry of the Ly alpha. emission and detect integrated linear polarization of 9%-13% +/- 2%-3% at a distance of approximately 15 kpc north and south of the peak of the Ly alpha. surface brightness with polarization vectors lying tangential to the galactic central source. In these same regions, we also detect a wavelength dependence in the polarization that. is low at the center of the Ly alpha. line profile and rises substantially in the wings of the profile. These polarization signatures are easily explained by a weak outflowing shell model. The spectral dependence of the polarization presented here provides a framework for future observations and interpretations of the southern portion of LAB1 in that any model for this system must be able to reproduce this particular spectral dependence. However, questions still remain for the northernmost spur of LAB1. In this region we detect total linear polarization of between 3% and 20% at the 5% significance level. Simulations predict that polarization should increase with radius for a symmetric geometry. That the northern spur does not suggests either that this region is not symmetric (which is likely) and exhibits variations in columns density. or that it is kinematically distinct from the rest of LAB1 and powered by another mechanism altogether.
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| 6419. |
- Becker, Julia K.
(författare)
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Status of neutrino astronomy
- 2008
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596. ; 136
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 6420. |
- Becker, Tracy M., et al.
(författare)
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HST UV Observations of Asteroid (16) Psyche
- 2020
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Ingår i: The Planetary Science Journal. - : American Astronomical Society. - 2632-3338. ; 1:3
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Tidskriftsartikel (refereegranskat)abstract
- The Main Belt Asteroid (16) Psyche is the target object of the NASA Discovery Mission Psyche. We observed the asteroid at ultraviolet (UV) wavelengths (170–310 nm) using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope during two separate observations. We report that the spectrum is very red in the UV, with a blue upturn shortward of ∼200 nm. We find an absorption feature at 250 nm and a weaker absorption feature at 275 nm that may be attributed to a metal-oxide charge transfer band. We find that the red-sloped, relatively featureless spectrum of (16) Psyche is best matched with the reflectance spectrum of pure iron; however, our intimate mixture models show that small grains of iron may dominate the reflectance spectrum even if iron only comprises up to 10% of the material on the surface. We also stress that there is a limited database of reflectances for planetary surface analogs at UV wavelengths for comparison with the spectrum of (16) Psyche. The mid- and far-UV spectra (<240 nm) are markedly different for each of the four asteroids observed at these wavelengths so far, including ones in the same spectral class, indicating that UV observations of asteroids could be used to better understand differences in the composition and processing of the surfaces of these small bodies.
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