Dear There, This is a resubmission of the DDT proposal to get the UV spectroscopy of the intriguing target F01004-2237, in which we have shown that the target is still UV bright and thus allows us to get a valuable UV spectra with reasonable time. In addition to the new UV photometry, the optical light curves have been also significantly updated by including ATLAS and Gaia data. Moreover, the scheduling requirement this time is not as pressing as last submission, when it was very close to the end of the last visibility window. Thus we really hope you can consider our new request, thanks a lot! Cheers, Ning Jiang 1208939990 Assigned ID: 2655 ----- Attempting Submission 1 (Fri Jan 14 15:27:50 GMT 2022) ----- HST Phase I Proposal 2655 successfully submitted. Receipt: # 2655-1 ----- Attempting Submission 2 (Thu May 12 15:11:14 GMT 2022) ----- HST Phase I Proposal 2655 successfully submitted. Receipt: # 2655-2 ----- Attempting Submission 3 (Thu May 12 15:14:45 GMT 2022) ----- HST Phase I Proposal 2655 successfully submitted. Receipt: # 2655-3 0 ----- Attempting Submission 1 (Thu Jun 09 00:51:36 GMT 2022) ----- HST Phase II Proposal 16943 successfully submitted. Receipt: # 16943-1 ----- Attempting Submission 2 (Wed Jun 22 00:38:10 GMT 2022) ----- An unexpected luminous optical flare (peak Mg=-21.4) turns up in ULIRG F01004-2237 since 2021 September, 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, 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, and its optical spectrum shows extremely broad Balmer emission lines. These observations have ruled out a supernova as its origin, 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, partial TDE, 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, we here propose to conduct STIS UV spectroscopic observations on F01004-2237 with 5 orbits time. Because the flare is darkening, we require the observation to be done as early as possible within the upcoming two visbility windows. The immediate objectives are mainly in three folds: 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. We request a single epoch (that could be split into multiple visits, if necessary) of UV spectroscopy of the recurring TDE candidate in IRAS F01004-2237, over the wavelength range from 1200-3000A. HST, with its sensitive UV spectrographs and exquisite angular resolution, is the only facility that can conduct such observations. We assume a spectrum proportional to lambda^(-2.2) and an AB magnitude of 18.4 in UVW1 band as suggested by the latest Swift observation. We assume that our targets are visible for 53 minutes each orbit. After including overheads for guide-star acquisition (6 min for the first orbit, 4 min for the subsequent orbits), target acquisition (~ 8 min for an extended source, no peak-up required for 0.2" slit width), and wavelength calibration (4 min per orbit), we find that we can obtain 35 min of exposure in the first orbit (43 in subsequent orbits). We request to allocate three-orbit time for G230L and two-orbit time for G140L, which will result in 7260 and 4680 second exposure time, respectively. According to the exposure time calculator by inputting our assumed SED, we would expect a SNR per resolution element >=10 for the range from 1650-3100 A. In addition, we use the actual data of iPTF16fnl on +51 day (Brown et al. 2018) as a reference. During this observation, iPTF16fnl had a UVW1 magnitude of 18.1 and a UV spectrum consistent with a blackbody curve with TBB ~32000 K, indicating that it is ~30% brighter than our target in the FUV band. The exposure time of iPTF16fnl is 4785 seconds and 5500 seconds for the G140L and G230L gratings, respectively, similar to our requested time. The SNR of the actual spectrum of iPTF16fnl meets our requirements. To summarize, we request a single epoch of STIS spectroscopy of F01004-2237, for a total of 5 orbits (2 FUV + 3 NUV). Our team has been focusing on various transients associated with supermassive black holes (SMBHs) in the past five years, particularly on tidal disruption events (TDEs). Dr.Bradley Cenko is the PI of at least two HST/STIS proposals (propID:13853 & 15331) on TDEs. Dr. Ning Jiang is the co-author of two TDE publications basing on HST/STIS UV spectra (Yang et al.2017,ApJ,846,150; Sheng et al.2021,ApJL,920,25). Other CoIs are also experts on multi-wavelength observations of TDEs and AGN outbrusts.. Supermassive Black Holes and Active Galaxies 6 false SUPPORTED GALAXY ACCRETION DISK NUCLEUS SEYFERT This object was generated by the targetselector and retrieved from the NED database.This object was generated by the targetselector and retrieved from the NED database. J2000 J2000 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 POS-TARG DITHER 0.4165 LINE false false 3 90.0 STIS-ALONG-SLIT 1 false /tmp/OPVisit13134526467680489947.xml 1655858201180 The scheduling data was generated by CASM 30.1. CASM was run in Phase II mode. 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