Abstract for Proposal 094134

Mapping the evolving gas flows in the AGN Mrk 817 with XMM-Newton and HST

The AGN STORM 2 Team has conducted the largest, cadenced multi-wavelength campaign of an AGN to date. This includes a Large HST Program, a Large XMM Program (AO20), a Swift Key Project, NICER and ground based monitoring. The campaign (which started in Dec 2020) has revealed a wealth of information on the structure and dynamics the AGN, including an unexpected obscuring outflows visible in X-ray and far-UV spectra. The success of this campaign has led to the continuation of the campaign. Now, we appear to be entering a new phase, where the obscuration from the outflow is diminishing. Here, we request to also extend the XMM-Newton+NuSTAR campaign, with one 120 ks ToO observation to catch the AGN in a new, truly unobscured state. This observation would take place with a pre-approved HST observation.

Details on Observing Strategy and Trigger Criteria
When the Swift 0.3–2 keV count rate exceeds 0.7 c/s,and the hardness ratio falls to HR < −0.4 for a full month (corroborated by NICER spectra showing the neutral hydrogen column density NH returning to its historical value and no clear signatures of an Fe UTA), we will trigger HST, and we request XMM-Newton+NuSTAR observations to be taken as close to simultaneous as possible