Electron-positron annihilation radiation from 3C 273

Z. ABRAHAM; ROMERO, G. E.; DUROUCHOUX, P.

Alicante, España

Workshop; Fourth INTEGRAL Workshop; 2000

The nature of the matter content of relativistic jets in quasars and other AGNs is a long-standing problem in extragalactic astrophysics. The recent detection of circularly polarized radio emission in the quasar 3C 273 and the discovery of MeV blazars by COMPTEL instrument of the Compton Gamma Ray Observatory strongly support the possibility that the relativistic plasma fluid in at least some AGNs is mainly formed by electron-positron pairs. In this paper we discuss some observational signatures of the expected annihilation line in 3C 273, based on the recent determiantion of a processing behaviour of the inner jet in this object by Abraham & Romero (1999). We present calculations of the Doppler factor time evolution and the expected position of the blueshifted annihilation line peak for the years 2002-2008, when the INTEGRAL spectrometer SPI and imager IBIS will be able to detect it. We also discuss how the observations can be used to impose bounds on the Hubble constant.