A Structured Leptonic Jet Model of the “Orphan” TeV Gamma‐Ray Flares in TeV Blazars

The emission spectra of TeV blazars extend up to tens of TeV and the emissionmechanism of the TeV $\gamma$-rays is explained by synchrotron self-Comptonscattering in leptonic models. In these models the time variabilities of X-raysand TeV $\gamma$-rays are correlated. However, recent observations of 1ES1959+650 and Mrk 421 have found the ``orphan'' TeV $\gamma$-ray flares, i.e.,TeV $\gamma$-ray flares without simultaneous X-ray flares. In this paper wepropose a model for the ``orphan'' TeV $\gamma$-ray flares, employing aninhomogeneous leptonic jet model. After a primary flare that accompaniesflare-up both in X-rays and TeV $\gamma$-rays, radiation propagates in variousdirections in the comoving frame of the jet. When a dense region in the jetreceives the radiation, X-rays are scattered by relativisticelectrons/positrons to become TeV $\gamma$-rays. These $\gamma$-ray photons areobserved as an ``orphan'' TeV $\gamma$-ray flare. The observed delay timebetween the primary and ``orphan'' flares is about two weeks and this isaccounted for in our model for parameters such as $\Gamma = 20$, $d = 4 \times10^{17}$cm, $\alpha = 3$, and $\eta = 1$, where $\Gamma$ is the bulk Lorentzfactor of the jet, $d$ is the distance between the central black hole and theprimary flare site, $\alpha/\Gamma$ is the angle between the jet axis and thedirection of the motion of the dense region that scatters incoming X-raysproduced by the primary flare, and $\eta/\Gamma$ is the angle between the jetaxis and the line of sight.Comment: 12page, 6 figures, accepted by Ap