"40 years of research in Radioastronomy, 25 at IAG/USP"

A workshop in honor of Zulema Abraham


HIGHLIGHTS


BEAMING AND PRECESSION IN THE INNER JET OF 3C273







The quasar 3C 273 is a well-known superluminal source. Zulema Abraham & Gustavo Romero (1999) investigated the effects of precession in the inner jet of 3C 273 on its beaming properties and high energy emission.
All available VLBI data were used to determine the kinematic evolution of the  jet.
The position angles, velocities and formation epochs of different superluminal components are consistent
 with a precessing inner jet.
The time-dependence of the Doppler factor for this jet was computed
 and the implications for the gamma -ray emission are discussed.
Additionally, the model, when considered along with simultaneous radio and X-ray variability observations,
provides an upper bound to the possible values of the Hubble constant (H₀<80 km/s/Mpc).
In a subsequent paper, Abraham & Romero (2000) proposed a binary black hole model for the central engine
of 3C 273 where  the rapid precession is tidally induced in the primary accretion disk inner region
 by a secondary black hole in a non-coplanar orbit.
Using γ- and X-ray data they estimated upper limits for the mass of the primary,
and then computed the relevant parameters of the system for a variety of disk models.
They also discussed some of the implications of the model for the electromagnetic and gravitational radiation from 3C 273.