Periodicity of TeV γ Rays from Mrk 501 observed with Cherenkov Telescopes in 1997

林 清一


   The BL Lacertae object Markarian 501 has shown very high activity from March to October in 1997. During this period the gamma ray emission was detected with ground based observations by the Utah Seven Telescope Array (USTA), Whipple, HEGRA, and CAT in the TeV energy range. We find evidence for periodicity of 23.9 days from TeV gamma ray light curves using the USTA data, and about 24 days using other group's data. This periodicity may be related with the dynamics of the central engine of the AGN, the rotation of the central black hole(s) or accretion disk, or the precession of a jet.