15222( 2) - 17-Jul-2017 16:41:21 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15222 Version: 2 Check-in Time: 17-Jul-2017 16:41:21 STScI Edit Number: 0 Title What Type of Star Made the One-of-a-kind Supernova iPTF14hls? ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Iair Arcavi University of California - Santa Barbara Y CoI: Dr. Curtis McCully Las Cumbres Observatory Global Telescope N Network CoI: Dr. Dale Andy Howell Las Cumbres Observatory Global Telescope N Network CoI: Dr. Avishay Gal-Yam Weizmann Institute of Science N CoI: Dr. Daniel Kasen University of California - Berkeley N CoI: Griffin Hosseinzadeh Las Cumbres Observatory Global Telescope N Network CoI: Dr. Xiaofeng Wang Tsinghua University N CoI: Dr. Jesper Sollerman Stockholm University N CoI: Igor Andreoni Swinburne University of Technology N ------------------------------------------------------------------------------------ Abstract iPTF14hls is an onging nearby supernova with spectral features identical to those of the common Type IIP class but more slowly evolving, remaining luminous for over 600 days with at least five distinct peaks in its light curve and showing evidence for multiple pre-explosion eruptions. The observed properties of iPTF14hls are unique among all known supernovae, challenge all existing explosion models and likely indicate pre-explosion eruptions with time scales and energies never observed before. Such eruptions are theorized to occur in ~95-130 solar mass stars which experience the pulsational pair instability. If iPTF14hls is indeed the first observed case of such a supernova, then determining its progenitor mass and metallicity will provide the first observational constraints of stellar evolutionary models in these mass ranges. Since no pre-explosion high-resolution imaging of the location of iPTF14hls exist, the only way to constrain the progenitor properties (independent of the supernova) is through HST studies of the site after the event fades. Such studies will require knowing the position of iPTF14hls to few-parsec precision. We propose a single-orbit HST observation to obtain high resolution localization of iPTF14hls before it fades. These images will serve as registration anchors for future post-event observations at the required precision (not possible with ground-based AO imaging). These observations will also allow us to measure the very late-time decline rate of iPTF14hls, constraining possible power sources, and to test an alternative explanation for iPTF14hls as a lensed normal supernova, by constraining any departure from point-source emission. ------------------------------------------------------------------------------------ Observations Description ------------------------ This is a single orbit imaging observation of a supernova in two filters (F475W and F625W) with UVIS. We implement a 3-point dither patern for each exposure to improve spatial 15222( 2) - 17-Jul-2017 16:41:21 - [ 2] resolution while still maintaining a minimum exposure time above 350s (to enable buffer readout during the next exposure). We also wish to capture the overall morphology of the host galaxy, which is approximately 10 arcseconds across. In addition, we require a large number of sources around the supernova to be able to register the current images to any future HST images taken of the host galaxy after the supernova fades, in order to study the supernova's immediate environment. To make sure that the galaxy is far enough from any chip edge and that we have enough registration sources in all directions around the supernova, we choose the UVIS2 aperture. ------------------------------------------------------------------------------------ 15222( 2) - 17-Jul-2017 16:41:21 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 IPTF14HLS EXT-STAR, SUPERNOVA RA=09H20M34.3000S +/- 0.1", J2000 V = 20 +/- 0.1 TYPE II DEC=+50D41'46.80" +/- 0.1" Reference Frame: ICRS Comments: The magnitude estimate depends on the epoch of observations as the supernova continues to fade. ------------------------------------------------------------------------------------------------------------------------------------ 15222( 2) - 17-Jul-2017 16:41:21 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 1.813 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.759 Angle_Between_Sides Center_Pattern YES Pattern_Comments: We choose a dither pattern that will also cover the chip gap to increase the availability of registration stars in that area. ------------------------------------------------------------------------------------------------------------------------------------ 15222( 2) - 17-Jul-2017 16:41:21 - [ 5] Visit: 01 (iPTF14hls) 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 IPTF14HLS WFC3/UVI ACCUM UVIS2 F475W FLASH=5 1 348 S PATTERN 3 1 S see below (1185 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 IPTF14HLS WFC3/UVI ACCUM UVIS2 F625W FLASH=2 1 348 S PATTERN 3 2 S see below (1185 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 | ------------------------------------------------------------------------------------------------------------------------------------ IPTF14HLS 1 WFC3/UVI ACCUM UVIS2 F475W 1 none none none 1 395.0 S S IPTF14HLS 1 WFC3/UVI ACCUM UVIS2 F475W 2 none none none 1 395.0 S S IPTF14HLS 1 WFC3/UVI ACCUM UVIS2 F475W 3 none none none 1 395.0 S S IPTF14HLS 2 WFC3/UVI ACCUM UVIS2 F625W 1 none none none 1 395.0 S S IPTF14HLS 2 WFC3/UVI ACCUM UVIS2 F625W 2 none none none 1 395.0 S S IPTF14HLS 2 WFC3/UVI ACCUM UVIS2 F625W 3 none none none 1 395.0 S S 15222( 2) - 17-Jul-2017 16:41:21 - [ 6] Summary Form for Proposal 15222 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=2, FLASH=5 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 3 1, PATTERN 3 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F475W, F625W ------------------------------------------------------------------------------------------------------------------------------------ Target Names IPTF14HLS ------------------------------------------------------------------------------------------------------------------------------------