NICER observation list: Target ID 557001

We propose ToO monitoring observations (2x300s per day for 200 d~120 ks) of a future stellar tidal disruption event (TDE). Our main goals are 1) to identify and study accretion states, transitions and accompanying corona formation around a supermassive black hole (SMBH) in a TDE. This follows NICER's recent success in doing so for the TDE AT2018fyk. 2) to search for the precession period of a newly formed accretion disk in soft X-rays to measure the SMBH spin. This is motivated by theoretical studies and NICER's detection of a 1.34 d quasi-periodicity in ASASSN-18EL: a changing-look AGN likely triggered by a TDE. Both our goals require excellent maneuverability, monitoring capability and a large soft X-ray effective area. At present, only NICER has all these capabilities.