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.