16943

An unexpected luminous optical flare (peak Mg=-21.4) turns up in ULIRG F01004-2237 since 2021 September comma revealed by its ATLAS and ASASSN light curves. This nearby galaxy once held a candidate tidal disruption event (TDE) because a luminous flare occurred in 2010 comma and now it brightens up again. The Gaia has also detected the new flare and pinpointed it at the galaxy.s center. The flare is now UV bright yet X-ray weak comma and its optical spectrum shows extremely broad Balmer emission lines. These observations have ruled out a supernova as its origin comma and therefore the flare is likely to be associated with the central supermassive black hole (SMBH). Such recurrent flares are rare as only few reported recurrent flares in other galaxies with diverse time intervals. Their nature are still ambiguous. They may be caused by repeated TDEs comma partial TDE comma SMBH binary or peculiar accretion disk instabilities. The timely discovery of the ongoing recurring flare in F01004-2237 offers a unique opportunity to acquire useful clues. Aiming to further explore the mechanism that drives the second flare as well as its connection with the first one comma we here propose to conduct STIS UV spectroscopic observations on F01004-2237 with 5 orbits time. Because the flare is darkening comma we require the observation to be done as early as possible within the upcoming two visbility windows. The immediate objectives are mainly in three foldsdoublePoint 1) to better map the flare.s SED and thus distinguish between the powerlaw (AGN) and blackbody (TDE) scenarios 2) to detect possible characteristic UV emission lines of either TDEs or AGNs 3) to detect possible UV absorption lines which might address the X-ray weakness.