Author(s): Smith D.A., Brion E., Britto Richard, Bruel P., Gordo J. Bussons, Dumora D., Durand E., Eschstruth P., Espigat P., Holder J., Jacholkowska Agnieszka, Lavalle J., Le Gallou R., Lott B., Manseri H., Munz F., Nuss E., Piron F., Rannot R.C., Reposeur T., Sako T.
(Article) Published:
Astronomy & Astrophysics, vol. 459 p.453-464 (2006)
Links openAccess full text : 
Ref HAL: in2p3-00113422_v1
Ref Arxiv: astro-ph/0608247
DOI: 10.1051/0004-6361:20065884
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
14 citations
Abstract:
We have measured the gamma-ray fluxes of the blazars Mrk 421 and Mrk 501 in the energy range between 50 and 350 GeV (1.2 to 8.3 x 10^25 Hz). The detector, called CELESTE, used first 40, then 53 heliostats of the former solar facility "Themis" in the French Pyrenees to collect Cherenkov light generated in atmospheric particle cascades. The signal from Mrk 421 is often strong. We compare its flux with previously published multi-wavelength studies and infer that we are straddling the high energy peak of the spectral energy distribution. The signal from Mrk 501 in 2000 was weak (3.4 sigma). We obtain an upper limit on the flux from 1ES 1426+428 of less than half that of the Crab flux near 100 GeV. The data analysis and understanding of systematic biases have improved compared to previous work, increasing the detector's sensitivity.
Comments: 15 pages, 14 figures, accepted by A&A (July 2006) August 19 -- corrected error in author list