15709( 2) - 18-Mar-2019 15:52:30 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15709 Version: 2 Check-in Time: 18-Mar-2019 15:52:30 STScI Edit Number: 0 Title An extreme interacting supernova from a very massive star: probing the immediate and galaxy-scale environment of a new pair-instability candidate ------------------------------------------------------------------------------------ Type Cycle GO 26 ------------------------------------------------------------------------------------ Investigators Contact? PI: Matt Nicholl Royal Observatory Edinburgh Y CoI: Prof. Edo Berger Harvard University N CoI: Mr. Peter Blanchard Harvard University N CoI: Sebastian Gomez Harvard University N CoI: Griffin Hosseinzadeh Harvard University N CoI: Prof. Ryan Chornock Ohio University N ------------------------------------------------------------------------------------ Abstract Supernovae that strongly interact with their immediate environments offer a unique way to probe mass loss from very massive stars, with critical implications for understanding stellar evolution and the expected distribution of remnant masses. We have discovered one of the most extreme interacting supernovae to date, PS16aqy, at a redshift of 0.265 but with no detectable host galaxy in ground-based imaging. We have conducted a multi-year follow-up campaign revealing a very slowly fading light curve and a radiated energy well in excess of the canonical 1e51 erg supernova explosion energy. It may in fact exceed the electromagnetic output of any previous SN. Spectroscopy shows narrow and intermediate Balmer emission lines that persist throughout its evolution. The combination suggests ongoing interaction with several tens of solar masses of circumstellar medium. This requirement for very high mass and explosion energy may be indicative of an extremely massive star and possibly a pair instability or pulsational pair instability supernova, critical for our understanding of stellar evolution. The transient is now sufficiently faint that it can only be studied using HST. A single optical image will extend our temporal baseline for light curve modelling by 50%, enabling much tighter constraints on the properties of the CSM, which is the key to understanding this event. At the same time a high resolution UV image of the host galaxy will allow us to determine the star-formation rate at the explosion site as a clue to the progenitor mass. This proposal could not be submitted during the regular Call for Proposals as no Small Programs were permitted in the original Cycle 26 call. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain an optical image of supernova PS16aqy in Cycle 26 using the Advanced Camera for Surveys (ACS) in the F775W filter, where we expect the transient to be brightest due to the presence of H-alpha emission, and a UV image of the host galaxy using Wide Field Camera 3 (WFC3) in the F390W filter, corresponding to rest-frame 3000 Angstroms. Taking into account the visibility window per orbit of 60 min, and the time 15709( 2) - 18-Mar-2019 15:52:30 - [ 2] needed for guide star acquisition, dithering (in a standard 4 point pattern) and per-exposure overheads for each instrument, the available time per orbit for integration on the target is about 2500s for ACS, and 2700s for WFC3. We expect to detect the transient with S/N > 20 and the galaxy with S/N > 10. ------------------------------------------------------------------------------------ 15709( 2) - 18-Mar-2019 15:52:30 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PS16AQY EXT-STAR, SUPERNOVA RA=10H19M2.1700S, J2000 V = 26 DEC=+74D42'24.67" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15709( 2) - 18-Mar-2019 15:52:30 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.262 Line_Spacing 0.192 Coordinate_Frame POS-TARG Pattern_Orient 18.39 Angle_Between_Sides 68.14 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15709( 2) - 18-Mar-2019 15:52:30 - [ 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 PS16AQY ACS/WFC ACCUM WFC1 F775W 1 500 S PATTERN 1 1 see below (2496 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 PS16AQY WFC3/UVI ACCUM UVIS1 F390W FLASH=6 1 500 S PATTERN 2 2 S see below (2784 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 | ------------------------------------------------------------------------------------------------------------------------------------ PS16AQY 1 ACS/WFC ACCUM WFC1 F775W 1 none none none 1 624.0 S PS16AQY 1 ACS/WFC ACCUM WFC1 F775W 2 none none none 1 624.0 S PS16AQY 1 ACS/WFC ACCUM WFC1 F775W 3 none none none 1 624.0 S PS16AQY 1 ACS/WFC ACCUM WFC1 F775W 4 none none none 1 624.0 S PS16AQY 2 WFC3/UVI ACCUM UVIS1 F390W 1 none none none 2 696.0 S S PS16AQY 2 WFC3/UVI ACCUM UVIS1 F390W 2 none none none 2 696.0 S S PS16AQY 2 WFC3/UVI ACCUM UVIS1 F390W 3 none none none 2 696.0 S S PS16AQY 2 WFC3/UVI ACCUM UVIS1 F390W 4 none none none 2 696.0 S S 15709( 2) - 18-Mar-2019 15:52:30 - [ 6] Summary Form for Proposal 15709 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=6 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, PATTERN 2 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F390W, F775W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PS16AQY ------------------------------------------------------------------------------------------------------------------------------------