A Cerenkov imaging telescope for high energy gamma rays

A large area gamma ray telescope based on the gas Cerenkov imaging technique is presented. The performances of the instrument for the observation of high energy gamma ray point sources are discussed

On the importance of interstellar helium for the propagation of heavy cosmic rays

The influence of interstellar He on the fragmentation of heavy cosmic rays in the interstellar medium (ISM) has long been a controversial subject. While H-induced cross section data are now avialable over broad mass and energy ranges, little data for He-induced fragmentation exists. With the recent reports of accurate measurements of the secondary/primary ratios in cosmic rays and of H-induced cross sections the problem of including interstellar He in propagation calculations becomes even more critical. As is argued the escape lengths lambda e deduced from the B/C+) and Sc-Cr/Fe ratios cannot be reconciled within the frame of a simple leaky box model assuming the ISM composed of pure H. It is quite remarkable that the discrepancy is especially large in the GeV region where (1) secondary/primary ratios measured by several groups agree fairly well and (2) fragmentation cross sections have been recently measured with good accuracy

Radio to Gamma-Ray Emission from Shell-type Supernova Remnants: Predictions from Non-linear Shock Acceleration Models

Supernova remnants (SNRs) are widely believed to be the principal source of galactic cosmic rays. Such energetic particles can produce gamma-rays and lower energy photons via interactions with the ambient plasma. In this paper, we present results from a Monte Carlo simulation of non-linear shock structure and acceleration coupled with photon emission in shell-like SNRs. These non-linearities are a by-product of the dynamical influence of the accelerated cosmic rays on the shocked plasma and result in distributions of cosmic rays which deviate from pure power-laws. Such deviations are crucial to acceleration efficiency and spectral considerations, producing GeV/TeV intensity ratios that are quite different from test particle predictions. The Sedov scaling solution for SNR expansions is used to estimate important shock parameters for input into the Monte Carlo simulation. We calculate ion and electron distributions that spawn neutral pion decay, bremsstrahlung, inverse Compton, and synchrotron emission, yielding complete photon spectra from radio frequencies to gamma-ray energies. The cessation of acceleration caused by the spatial and temporal limitations of the expanding SNR shell in moderately dense interstellar regions can yield spectral cutoffs in the TeV energy range; these are consistent with Whipple's TeV upper limits on unidentified EGRET sources. Supernova remnants in lower density environments generate higher energy cosmic rays that produce predominantly inverse Compton emission at super-TeV energies; such sources will generally be gamma-ray dim at GeV energies.Comment: 62 pages, AASTeX format, including 1 table and 11 figures, accepted for publication in The Astrophysical Journal (Vol 513, March 1, 1999

Considérations et essais statistiques sur les séro-réactions appliquées au diagnostic de la maladie de Rubarth et des leptospiroses canines

Goret Pierre. Considérations et essais statistiques sur les séro-réac-tions appliquées au diagnostic de la maladie de Rubarth et des leptospiroses canines. In: Bulletin de l'Académie Vétérinaire de France tome 110 n°8, 1957. pp. 427-430

Observations sur l’ovoculture du virus de Carré (à propos de la note de M. Velu) et sur le syndrome « Hard Pad Disease » (à propos de la note de M. Lebeau)

Goret Pierre. Observations sur l’ovoculture du virus de Carré (A propos de la note de M. Velu) - et sur le syndrome « Hard Pad disease » (A propos de la note de M. Lebeau). In: Bulletin de l'Académie Vétérinaire de France tome 106 n°9, 1953. pp. 521-523