X-ray outburst of the quasar 3C 279

Abstract

A large X-ray flare-up of the quasar 3C 279, coinciding with an unusual multifrequency outburst, was detected with X-ray astronomy satellite Ginga. Observations carried out on two occasions (1987 June and 1988 July) indicate that the 2-20 keV flux has increased by a factor of more than 4, from 1.2 to 5.3 μJy at 2 keV, within about a year. During the outburst, the X-ray spectrum became slightly harder than that in the quiet period, the photon index changing from {GAMMA} = 1.70 +/- 0.06 to 1.58 +/- 0.03. The X-ray flux varied by 20% during the outburst within a period as short as 45 minutes, which indicates {DELTA}L/{DELTA}t > 2 x 10^42^ ergs s^-2^ for H_0_ = 100 km s^-1^ Mpc^-1^ and q_0_ = 0.5, the largest value ever observed for a quasar. The observed {DELTA}L/{DELTA}t suggests that the X-ray-emitting region is moving with a relativistic velocity toward us. These results suggest that a relativistic jet is being formed.