Abstract for Proposal 090022
Catching AGN in Deep Minimum States to Unveil Their Core Environment
The deep minimum state of AGN is characterized by a strongly suppressed or
even absent primary continuum. As the continuum disappears weak spectral
features like relativistic iron lines or narrow soft X-ray emission lines
from ionised plasmas become highly significant and their parameters can
be determined. Therefore deep minimum states offer unique possibilities
to investigate in detail the physics of the reprocessed components in AGN,
including the immediate vicinity of the supermassive black hole. Applying
our experience (several deep minimum observations) we propose 2 triggered
10ks XMM snapshot, one 80ks XMM follow-up simultaneous with one 80ks
NuSTAR one 2-orbit HST observation of an AGN in deep minimum state.
Details on Observing Strategy and Trigger Criteria
Beside a serendipitous approach (e.g. ATel) we search systematically
using two resources: Swift Fill-in and serendipitous observations of AGNs
(Grupe et al. 2010, ApJS, 187, 64): based on previous years experience
and taking into account XMM-Newton visibility we expect to detect 1.5
low-state AGN visible per year. XMM-Newton slews: All slew sources
are public in the XMM-Newton web-page within 1 - 2 weeks. We check all
sources found in XMM-Newton slews and search for AGNs which are at least
10 times fainter than they were during ROSAT measurements. We expect
one candidate every two years. Depending on the count rate detected by
Swift or XMM-Newton slew we will decide about the (short) XMM-Newton
follow-up observation duration. If the short XMM-Newton observation
shows spectral complexity, then we plan to trigger a further, deeper
observation with an exposure time of 80 ks. Contemporaneously we want to
trigger a simultaneous 80ks NuSTAR observation and we want to trigger
a 2 orbit long HST Cosmic Origins Spectrograph (COS) observation with
E130M and G160M. The reaction time for the triggers can be some weeks
depending on the visibility of the target.