The binary black hole scenario for the BL Lacertae object AO 0235+16

Abstract

Recent analysis of the long term radio lightcurve of the extremely variable BL Lacertae object AO 0235+16 by Raiteri et al. (2001) have revealed the presence of recurrent outbursts in this source with a period of ~ 5.7 +/- 0.5 yr. Periodicity analysis of the optical lightcurve also show evidence for a shorter period. Here we discuss whether such a behavior can be explained by a binary black hole model where the accretion disk of one of the supermassive black holes is precessing due to the tidal effects of the companion. We estimate the mass of the accreting hole and analyze under what constraints onto the secondary mass and the orbital parameters of the system it is possible to provide a viable interpretation of the available multiwavelength data.