15236( 3) - 10-Nov-2017 20:32:36 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15236 Version: 3 Check-in Time: 10-Nov-2017 20:32:36 STScI Edit Number: 0 Title The mystery of a supposed massive star exploding in a brightest cluster galaxy ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Griffin Hosseinzadeh Las Cumbres Observatory Global Telescope Y Network CoI: Dr. Iair Arcavi University of California - Santa Barbara N CoI: Dr. Dale Andy Howell Las Cumbres Observatory Global Telescope N Network CoI: Dr. Curtis McCully Las Cumbres Observatory Global Telescope N Network CoI: Dr. Stefano Valenti University of California - Davis N CoI: Dr. Katheryn Decker French Carnegie Institution of Washington N CoI: Prof. Ann Zabludoff University of Arizona N ------------------------------------------------------------------------------------ Abstract Most of the diversity of core-collapse supernovae results from late-stage mass loss by their progenitor stars. Supernovae that interact with circumstellar material (CSM) are a particularly good probe of these last stages of stellar evolution. Type Ibn supernovae are a rare and poorly understood class of hydrogen-poor explosions that show signs of interaction with helium-rich CSM. The leading hypothesis is that they are explosions of very massive Wolf-Rayet stars in which the supernova ejecta excites material previously lost by stellar winds. These massive stars have very short lifetimes, and therefore should only found in actively star-forming galaxies. However, PS1-12sk is a Type Ibn supernova found on the outskirts of a giant elliptical galaxy. As this is extraordinary unlikely, we propose to obtain deep UV images of the host environment of PS1-12sk in order to map nearby star formation and/or find a potential unseen star-forming host. If star formation is detected, its amount and location will provide deep insights into the progenitor picture for the poorly-understood Type Ibn class. If star formation is still not detected, these observations would challenge the well-accepted hypothesis that these are core-collapse supernovae at all. ------------------------------------------------------------------------------------ Observations Description ------------------------ SUMMARY: We plan to map the star formation rate in the region surrounding the explosion location of PS1-12sk now that the supernova has faded. This will be accomplished with 4.5 orbits of UV imaging of the field with WFC3+F300X. We need very deep ultraviolet images with very low sky background to detect low-surface-brightness star-forming regions. In the event that we find an unseen host galaxy, we will also need an optical image that matches HST's resolution to aid in registration with the ground-based localization. We will therefore obtain an additional half orbit in 15236( 3) - 10-Nov-2017 20:32:36 - [ 2] SDSS r' (WFC3+F625W). In addition, HST will likely be able to resolve the nearby dwarf galaxy, which is a possible host, and any potential gas flows leading toward the supernova location from either the brightest cluster galaxy or the dwarf galaxy. DETAILS: We have separated each of our five orbits into a separate visit for flexibility. However, scheduling the orbits together would save some time reacquiring, which could be added to the UV exposure for deeper limits. Because we are searching for a low-surface-brightness source, CTE losses may be important. We have used the FLASH settings recommended by the APT to reach 12 electrons per pixel. However, because we are potentially interested in sources up to ~30" from the supernova location, we cannot move the target closer to the amplifiers (i.e., we choose the UVIS2 aperture). We choose a three-point dither for each of the first four orbits in order to (1) break up the exposures for cosmic ray rejection, (2) better sample the PSF, and (3) cover the chip gap. For the fifth orbit, we use the three-point dither for F625W but only a two-point dither for F300X to save time spent on overhead. Ultimately, we will stack all 14 exposures in F300X for analysis. ------------------------------------------------------------------------------------ 15236( 3) - 10-Nov-2017 20:32:36 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PS1-12SK CLUSTER OF GALAXIES, RA=08H44M54.8592S, J2000 V = 26.5 BCM, COOLING FLOW, STAR DEC=+42D58'16.90" FORMING REGION Reference Frame: Other: NED Comments: This object was generated by the target selector and retrieved from the NED database. ------------------------------------------------------------------------------------------------------------------------------------ 15236( 3) - 10-Nov-2017 20:32:36 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 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_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 1.82 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.759 Angle_Between_Sides Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 15236( 3) - 10-Nov-2017 20:32:36 - [ 5] 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 PS1-12SK WFC3/UVI ACCUM UVIS2 F300X FLASH=8 1 896 S PATTERN 1 1 S (2688 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 | ------------------------------------------------------------------------------------------------------------------------------------ PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 1 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 2 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 3 none none none 1 N/A S 15236( 3) - 10-Nov-2017 20:32:36 - [ 6] Visit: 02 Visit Requirements: SAME ORIENT AS 01 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 PS1-12SK WFC3/UVI ACCUM UVIS2 F300X FLASH=8 1 896 S PATTERN 1 1 S (2688 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 | ------------------------------------------------------------------------------------------------------------------------------------ PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 1 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 2 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 3 none none none 1 N/A S 15236( 3) - 10-Nov-2017 20:32:36 - [ 7] Visit: 03 Visit Requirements: SAME ORIENT AS 01 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 PS1-12SK WFC3/UVI ACCUM UVIS2 F300X FLASH=8 1 896 S PATTERN 1 1 S (2688 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 | ------------------------------------------------------------------------------------------------------------------------------------ PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 1 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 2 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 3 none none none 1 N/A S 15236( 3) - 10-Nov-2017 20:32:36 - [ 8] Visit: 04 Visit Requirements: SAME ORIENT AS 01 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 PS1-12SK WFC3/UVI ACCUM UVIS2 F300X FLASH=8 1 896 S PATTERN 1 1 S (2688 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 | ------------------------------------------------------------------------------------------------------------------------------------ PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 1 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 2 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 3 none none none 1 N/A S 15236( 3) - 10-Nov-2017 20:32:36 - [ 9] Visit: 05 Visit Requirements: SAME ORIENT AS 01 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 PS1-12SK WFC3/UVI ACCUM UVIS2 F300X FLASH=9 1 675 S PATTERN 2 1 S (1350 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 PS1-12SK WFC3/UVI ACCUM UVIS2 F625W FLASH=2 1 350 S PATTERN 1 2 S (1050 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 | ------------------------------------------------------------------------------------------------------------------------------------ PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 1 none none none 1 N/A S PS1-12SK 1 WFC3/UVI ACCUM UVIS2 F300X 2 none none none 1 N/A S PS1-12SK 2 WFC3/UVI ACCUM UVIS2 F625W 1 none none none 1 N/A S PS1-12SK 2 WFC3/UVI ACCUM UVIS2 F625W 2 none none none 1 N/A S PS1-12SK 2 WFC3/UVI ACCUM UVIS2 F625W 3 none none none 1 N/A S 15236( 3) - 10-Nov-2017 20:32:36 - [ 10] Summary Form for Proposal 15236 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=2, FLASH=8, FLASH=9 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 1 2, PATTERN 2 1, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F300X, F625W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PS1-12SK ------------------------------------------------------------------------------------------------------------------------------------