1998A&A...334L..29X

We report the observation of a dramatic outburst in the optical band from the active galaxy Markarian 421 (Mrk 421). During this outburst, the brightness of Mrk 421 increased rapidly by 1.34mag from B=15.67 to B=14.32 in 26 minutes. Another interesting fact is that this extremely rapid burst in the optical band is similar to the dramatic outburst of TeV photons which was obtained by Gaidos et al. (1996) in every essential respect, for example, the time scales on which they vary, and the shapes of the light curves. These data in the optical band and TeV γ-ray suggest that they are both produced in the same emission region, and that the emission region is extremely small, R≃1.23x10¹⁴cm. With these results, we prove that there is a massive black hole with M=2x10⁶M_☉ in the centre of Mrk 421. We obtained also a important result R=205R_g>200R_g (Sunyaev 1975). This could provide a new challenge for current theoretical model of such emissions. We prove that the origin of TeV γ-ray is by Synchrotron self-Compton.