15853( 5) - 14-Aug-2019 18:46:27 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15853 Version: 5 Check-in Time: 14-Aug-2019 18:46:27 STScI Edit Number: 1 Title Did SN 2017ein Arise From A Very Massive Star? ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Schuyler D. Van Dyk California Institute of Technology Y CoI: Dr. Jennifer Andrews University of Arizona N CoI: Dr. Thomas G Brink University of California - Berkeley N CoI: Prof. Alex V. Filippenko University of California - Berkeley N CoI: Dr. Ori Dosovitz Fox Space Telescope Science Institute N CoI: Dr. Patrick Kelly University of Minnesota - Twin Cities N CoI: Dr. Dan Milisavljevic Purdue University N CoI: Dr. Nathan Smith University of Arizona N CoI: Dr. WeiKang Zheng University of California - Berkeley N ------------------------------------------------------------------------------------ Abstract 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. ------------------------------------------------------------------------------------ Observations Description ------------------------ 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. ------------------------------------------------------------------------------------ 15853( 5) - 14-Aug-2019 18:46:27 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN2017EIN STAR, SUPERNOVA RA=11H52M59.0530S +/- 0.5", J2000 V = 34 +/- 1 DEC=+44D06'18.63" +/- 0.5" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 15853( 5) - 14-Aug-2019 18:46:27 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15853( 5) - 14-Aug-2019 18:46:27 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SN2017EIN WFC3/UVI ACCUM UVIS F336W FLASH=9 1 875 S PATTERN 1 1 S (2625 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SN2017EIN 1 WFC3/UVI ACCUM UVIS F336W 1 none none none 1 N/A S SN2017EIN 1 WFC3/UVI ACCUM UVIS F336W 2 none none none 1 N/A S SN2017EIN 1 WFC3/UVI ACCUM UVIS F336W 3 none none none 1 N/A S 15853( 5) - 14-Aug-2019 18:46:27 - [ 5] Summary Form for Proposal 15853 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=9 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN2017EIN ------------------------------------------------------------------------------------------------------------------------------------