Warping and Precession in Galactic and Extragalactic Accretion Disks

The Bardeen-Petterson general relativistic effect has been suggested as themechanism responsible for precession in some accretion disk systems. Here weexamine separately four mechanisms (tidally-induced, irradiation-induced,magnetically-induced and Bardeen-Petterson-induced) that can lead to warpingand precession. We use a sample of eight X-ray binaries and four ActiveGalactic Nuclei (AGNs) that present signatures of warping and/or precession intheir accretion disks to explore the viability of the different mechanisms. Forthe X-ray binaries SMC X-1 and 4U 1907+09 all four mechanisms provideprecession periods compatible with those observed, while for Cyg X-1 and theactive galaxies Arp 102B and NGC 1068, only two mechanisms are in agreementwith the observations. The irradiation-driven instability seems incapable ofproducing the inferred precession of the active galaxies in our sample, and thetidally-induced precession can probably be ruled out in the case of Arp 102B.Perhaps the best case for a Bardeen-Petterson precession can be achieved forNGC 1068. Our results show that given the many observational uncertainties thatstill exist, it is extremely difficult to confirm unambiguously that theBardeen-Petterson effect has been observed in any of the other sources of oursample.Comment: 35 pages, 8 figures, accepted for publication in The Astrophysical Journa