3 research outputs found
Constraining the Cosmic Background Light with four BL Lac TeV spectra
The intrinsic BL Lac spectra above few hundreds GeV can be very different
from the observed ones due to the absorption effects by the diffuse
Extragalactic Background Light (EBL), at present poorly known. With the recent
results, there are now 4 sources with good spectral information: Mkn 421
(z=0.031), Mkn 501 (z=0.034), 1ES 1426+428 (z=0.129) and 1ES 1959+650
(z=0.047). Making simple assumptions on the shape of the intrinsic spectra
(according to the present blazar knowledge), we have considered the effects of
different EBL spectral energy distributions (SED) for the first time on all 4
objects together, deriving constraints for the EBL fluxes. These resulted
significantly lower than many direct estimates.Comment: 4 pages, 8 figures; to appear in the proceedings of the 2nd Veritas
Symposium: "TeV Astrophysics of extragalactic sources". April 2003, Chicag
The CAT Imaging Telescope for Very-High-Energy Gamma-Ray Astronomy
The CAT (Cherenkov Array at Themis) imaging telescope, equipped with a
very-high-definition camera (546 fast phototubes with 0.12 degrees spacing
surrounded by 54 larger tubes in two guard rings) started operation in Autumn
1996 on the site of the former solar plant Themis (France). Using the
atmospheric Cherenkov technique, it detects and identifies very high energy
gamma-rays in the range 250 GeV to a few tens of TeV. The instrument, which has
detected three sources (Crab nebula, Mrk 421 and Mrk 501), is described in
detail.Comment: 24 pages, 15 figures. submitted to Elsevier Preprin
A new analysis method for very high definition Imaging Atmospheric Cherenkov Telescopes as applied to the CAT telescope
A new method of shower-image analysis is presented which appears very
powerful as applied to those Cherenkov Imaging Telescopes with very high
definition imaging capability. It provides hadron rejection on the basis of a
single cut on the image shape, and simultaneously determines the energy of the
electromagnetic shower and the position of the shower axis with respect to the
detector. The source location is also reconstructed for each individual
gamma-ray shower, even with one single telescope, so for a point source the
hadron rejection can be further improved. As an example, this new method is
applied to data from the CAT (Cherenkov Array at Themis) imaging telescope,
which has been operational since Autumn, 1996.Comment: 22 pages. submitted to Elsevier Preprin