0 Assigned ID: 298 ----- Attempting Submission 1 (Fri Apr 05 00:01:06 GMT 2019) ----- HST Phase I Proposal 298 (sn2017ein.apt) successfully submitted. Receipt: # 298-1 ----- Attempting Submission 2 (Fri Apr 05 08:32:59 GMT 2019) ----- HST Phase I Proposal 298 (sn2017ein.apt) successfully submitted. Receipt: # 298-2 ----- Attempting Submission 3 (Fri Apr 05 19:24:22 GMT 2019) ----- HST Phase I Proposal 298 (sn2017ein.apt) successfully submitted. Receipt: # 298-3 0 ----- Attempting Submission 1 (Fri Jul 19 21:17:18 GMT 2019) ----- ----- Attempting Submission 2 (Mon Aug 12 21:06:10 GMT 2019) ----- HST Phase II Proposal 15853 (15853_phase2.v2.apt) successfully submitted. Receipt: # 15853-2 ----- Attempting Submission 3 (Wed Aug 14 18:36:57 GMT 2019) ----- SN 2017ein in NGC 3938 represents the first-ever case in which a credible progenitor candidate has been identified for a Type Ic supernova, after nearly two decades of searching for such progenitors. The candidate was isolated in pre-explosion archival HST WFPC2 imaging of the host galaxy from 2007. Although the host galaxy distance and line-of-sight extinction to the progenitor candidate are not known well, the evidence points to the candidate being very blue, and therefore hot, and also quite luminous. The inference from these properties is that the progenitor would have to be very massive, at >45 solar masses, whether a single star or a member of a binary system. Such a high mass is a conundrum, given that the supernova ejecta mass inferred from observations of the otherwise-normal SN 2017ein is about 1 solar mass, more consistent with expectations if the progenitor were of significantly lower mass. Alternative explanations include that the candidate is a blue compact stellar cluster, of which the progenitor may have been a member, or that the progenitor had no physical connection whatsoever to the candidate, but was just situated within its PSF. We propose to reimage the SN site with WFC3/UVIS to determine whether the candidate has vanished completely, indicating that it was the actual progenitor, which would be astounding and potentially game-changing; or, whether the candidate persists, either unchanged in brightness or dimmed somewhat from its pre-SN state due to the demise of the real, unseen progenitor. SN 2017ein should have faded sufficiently by Cycle 27. The SN 2017ein progenitor candidate is currently the most intriguing and compelling such object for study. We will image the site of SN 2017ein with WFC3/UVIS in band F336W in one orbit. We will split the total exposure time into 3 line-dithered frames of 875 sec each. The frame pointing is offset some from the nominal SN position. Reduced gyro operations should have minimal effect. All members of this team were authors on the paper on the discovery of the SN 2017ein progenitor, Van Dyk et al. (2018, ApJ, 860, 90). The progenitor candidate was identified by this team based on observations of the SN as part of the successful ToO program GO-14645. Each team member lent their expertise to the publication of that paper and now have a vested interest in the results of the proposed observations. Each member of this team will likewise lend their expertise once again toward the completion of the subsequent paper that would arise from analysis of the new observations. Team contributions, in brief, to Van Dyk et al.: Dr. Jennifer Andrews, MMT spectroscopic observations, reduction, and analysis; assessment of spectral features indicative of interstellar extinction. Dr. Thomas Brink, Lick spectroscopic observations and reduction. Professor Alexei Filippenko, editing of and input to the submitted and resubmitted manuscripts, and PI of the Lick observations. Dr. Ori Fox, analytical contributions to the manuscript text. Professor Patrick Kelly, analytical contributions to the manuscript text. Professor Dan Milisavljevic, extensive analytical contributions to the manuscript text. Professor Nathan Smith, lead of the MMT observations, and extensive contributions to the manuscript regarding the reddening of the SN and considerations of the SN progenitor. Dr. Schuyler Van Dyk, lead author. Dr. WeiKang Zheng, Lick KAIT and Nickel observations and reduction. Stellar Physics Stellar Populations 6 false false false false false false false SUPPORTED STAR SUPERNOVA This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F814W POS-TARG DITHER 0.135 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE-3PT 1 false 1565804616207 /Users/vandyk/Documents/proposals/hst/cycle27/OP-cache/15853_phase2-v01.xml The scheduling data was generated by CASM 27.2. CASM was run in Phase II mode. 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