Automate de maitrise thermique des fermentations Grenier, P; Davenel, A; Gehin, I ...
Automatic control and optimisation of food processes / edited by M. Renard and J.J. Bimbenet,
1988
Publication
Astron.Astrophys. 350 (1999) 17-24 The BL Lac object Mrk 501 went into a very high state of activity during
1997, both in VHE gamma-rays and X-rays. We present here results from
observations at ...energies above 250 GeV carried out between March and October
1997 with the CAT Cerenkov imaging Telescope. The average differential spectrum
between 30 GeV and 13 TeV shows significant curvature and is well represented
by phi_0 * E_TeV^{-(alpha + beta*log10(E_TeV))}, with: phi_0 = 5.19 +/- 0.13
{stat} +/- 0.12 {sys-MC} +1.66/-1.04 {sys-atm} * 10^-11 /cm^2/s/TeV alpha =
2.24 +/- 0.04 {stat} +/- 0.05 {sys} beta = 0.50 +/- 0.07 {stat} (negligible
systematics). The TeV spectral energy distribution of Mrk 501 clearly peaks in
the range 500 GeV-1 TeV. Investigation of spectral variations shows a
significant hardness-intensity correlation with no measurable effect on the
curvature. This can be described as an increase of the peak TeV emission energy
with intensity. Simultaneous and quasi-simultaneous CAT VHE gamma-ray and
BeppoSAX hard X-ray detections for the highest recorded flare on 16th April and
for lower-activity states of the same period show correlated variability with a
higher luminosity in X-rays than in gamma-rays. The observed spectral energy
distribution and the correlated variability between X-rays and gamma-rays, both
in amplitude and in hardening of spectra, favour a two-component emission
scheme where the low and high energy components are attributed to synchrotron
and inverse Compton (IC) radiation, respectively.
Nucl.Instrum.Meth. A416 (1998) 425-437 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.
The CAT Imaging Telescope has observed the BL Lac object Markarian 501
between March and August 1997. We report here on the variability over this time
including several large flares. We present also ...preliminary spectra for all
these data, for the low emission state, and for the largest flare.
The CAT imaging telesope, which uses the Atmospheric Cherenkov Technique to
observe TeV gamma-ray sources, has been operating since September 1996. Located
in southern France, it features a fine ...grained camera consisting of 546 PMT
with a pixel size of 0.12 degrees. Strong gamma-ray signals from Mkn 501 above
200 GeV were detected during observations made in April 1997. The high
signal/noise ratio for these data enables direct characterization of the
gamma-ray images as recorded in the camera. These results are used to validate
the Monte-Carlo simulations of the response of the telescope to gamma-ray
showers and to improve its performances. Observational results on Mkn 180 and
the Crab nebula spectrum are presented.
The CAT imaging telescope, recently built on the site of the former solar
plant Themis (French Pyrenees), observed gamma-rays from the Crab nebula from
October 1996 to March 1997. This steady source, ...often considered as the
standard candle of very-high-energy gamma-ray astronomy, is used as a test-beam
to probe the performances of the new telescope, particularly its energy
threshold (220 GeV at 20 degrees zenith angle) and the stability of its
response. Due to the fine-grain camera, an accurate analysis of the
longitudinal profiles of shower images is performed, yielding the source
position in two dimensions for each individual shower.
The CAT Imaging Telescope Barrau, A; Bazer-Bachi, R; Cabot, H ...
arXiv (Cornell University),
05/1997
Journal Article
Open access
The VHE gamma-ray imaging telescope CAT started taking data in October 1996.
Located at the Themis solar site in southern France, it features a 17.7 m^2
Davies-Cotton mirror equipped with 600 PMT ...camera at the focal plane. The
mechanics and optics, the PMTs and the electronics are presented. The
performance, based on the first 7 months of operation, is discribed.
The CAT imaging telescope on the site on the former solar plant Themis has
been observing gamma-rays from Mrk501 above 220 GeV in March and April 1997.
This source is shown to be highly variable and ...the light curve is presented.
The detected gamma-ray rate for the most intense flare is in excess of 10 per
minute.
