Observations of the gamma-Ray Emission Above 250 Gev from the Blazars Markarian 501 and Markarian 421 by the Cat Cherenkov Atmospheric Imaging Telescope

摘要

The Very High Energy (VHE) gamma-ray emission of the closest BL Lacertaeobjects Markarian 501 and Markarian 421 has been observed by the CAT telescopein 1997 and 1998. In 1997 Mrk 501 exhibited a remarkable series of flares, witha VHE emission peaking above 250 GeV. The source showed correlated emissions inthe X-ray and VHE gamma-ray bands, together with intensity-spectral hardnesscorrelation in the latter energy range. During small flares in 1998, Mrk 421became the second extragalactic source detected by CAT. Its spectral propertiesare compared to those of Mrk 501. Theoretical implications for jet astrophysicsare briefly discussed.