X-ray dips in the Seyfert Galaxy Fairall 9: Compton-thick "comets" or a
  failed radio galaxy?
  We investigate the spectral variability of the Seyfert galaxy Fairall 9 using
almost 6 years of monitoring with the Rossi X-ray Timing Explorer (RXTE) with
an approximate time resolution of 4 days. We discover the existence of
pronounced and sharp dips in the X-ray flux, with a rapid decline of the 2--20
keV flux of a factor 2 or more followed by a recovery to pre-dip fluxes after
~10 days . These dips skew the flux distribution away from the commonly
observed log-normal distribution. Dips may result from the eclipse of the
central X-ray source by broad line region (BLR) clouds, as has recently been
found in NGC 1365 and Mrk 766. Unlike these other examples, however, the clouds
in Fairall 9 would need to be Compton-thick, and the non-dip state is
remarkably free of any absorption features. A particularly intriguing
alternative is that the accretion disk is undergoing the same cycle of
disruption/ejection as seen in the accretion disks of broad line radio galaxies
(BLRGs) such as 3C120 but, for some reason, fails to create a relativistic jet.
This suggests that a detailed comparison of Fairall 9 and 3C120 with future
high-quality data may hold the key to understanding the formation of
relativistic jets in AGN.
