16215( 2) - 03-Jun-2020 16:34:37 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16215 Version: 2 Check-in Time: 03-Jun-2020 16:34:37 STScI Edit Number: 1 Title UV to NIR Study of the the First Robust Pulsational or Pair Instability Supernova and its Low Metallicity Environment ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Sebastian Gomez Harvard University Y CoI: Prof. Edo Berger Harvard University N CoI: Dr. Peter Blanchard Northwestern University N CoI: Dr. Matt Nicholl University of Birmingham N CoI: Ms. Ashley Villar Harvard University N CoI: Locke Patton Smithsonian Institution Astrophysical N Observatory CoI: Dr. Griffin Hosseinzadeh Harvard University N CoI: Dr. Philip Cowperthwaite Carnegie Institution of Washington N CoI: Prof. Ryan Chornock Ohio University N ------------------------------------------------------------------------------------ Abstract SN2016iet is an unprecedented supernova in terms of its temporal evolution, spectra, and environment. The light curve exhibits two distinct peaks separated by 100 days, and slowly decline by only 5 mag in 2.5 years. The spectra are dominated by a blue continuum and low velocity calcium and oxygen lines with an unusually high Ca/O ratio, but lack hydrogen or helium. The SN is located at an unusually large offset (16 kpc, 5 effective radii) from a low metallicity dwarf galaxy (0.1 Zsun, 3e8 Msun). Modeling of the SN data indicates that it is powered by interaction of 20-85 Msun of ejecta with 35 Msun of H/He-free circumstellar material (CSM), ejected in the final decade before explosion. Thus, the progenitor's CO core shortly before explosion was 55-120 Msun, placing it in the regime of pulsational pair instability or pair instability explosions, further supported by the low metallicity. This is the first robust case for such an origin based directly on a large progenitor mass and low metallicity. We request observations of this unprecedented SN to achieve several goals that can only be done with HST: (i) track the SN emission at >1000 days post explosion, as it fades below ground-based capabilities, to track the large-scale CSM; (ii) use NIR data to search for the first time for evidence of dust formation in H/He-poor CSM interaction; (iii) measure the UV brightness of the host galaxy to precisely determine its star formation activity and escape fraction of ionizing radiation; and (iv) search for a potential underlying galaxy at the SN position, which from existing limits will be <1e-3 L*. This will be accomplished with 4 orbits in Cycle 27 and 3 orbits in Cycle 28. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request 4 orbits in Cycle 27 to observe SN2016iet at R.A.=12:32:33.23, decl.=+27:07:15.49 (J2000) to be observed during the early half of cycle 27, due to the fading nature of the source. The 4 orbits need not be done consequtively nor in a particular order, but they should be done within 30 days of each other. We split the 4 orbits into 2 distinct visits of 2 orbits each to 16215( 2) - 03-Jun-2020 16:34:37 - [ 2] aid the scheduler without increasing the overheads to much. One visit with WFC3/IR with one orbit dedicated to the F110W filter, and one orbit to the F160W filter. For the second visit one orbit should be done with ACS/WFC with the F625W filter, and a second orbit with WFC3/UVIS wit the F225W filter. For each orbit we request 4 individual exposures, dithered with a box pattern. Both visits should be scheduled within 30 days of each other, due to the fading nature of the supernova. This multi-cycle proposal has three additional orbits scheduled during Cycle 28 to obtain templates after the supernova has faded. We request these during the late half of Cycle 28. One ACS/WFC orbit with filter F625W, one WFC3/IR orbit with filter F110W, and one orbit with the F160W filter. ------------------------------------------------------------------------------------ 16215( 2) - 03-Jun-2020 16:34:37 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN2016IET STAR, SUPERNOVA RA=12H32M33.2300S, J2000 V = 27.0 +/- 0.5 DEC=+27D07'15.49" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 16215( 2) - 03-Jun-2020 16:34:37 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-UVIS Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 23.02 Line_Spacing 35.212 Coordinate_Frame POS-TARG Pattern_Orient 0.713 Angle_Between_Sides 89.287 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 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 ------------------------------------------------------------------------------------------------------------------------------------ 16215( 2) - 03-Jun-2020 16:34:37 - [ 5] Visit: 01 Visit Requirements: GROUP 01, 02 WITHIN 30D 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 SN2016IET WFC3/IR MULTIAC IR F110W NSAMP=7, SAMP-SEQ=SPARS100 1 DEF GS ACQ SCENARIO BASE1B3; CUM (2411.737 PATTERN 1 1 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2016IET WFC3/IR MULTIAC IR F160W NSAMP=7, SAMP-SEQ=SPARS100 1 DEF PATTERN 1 2 CUM (2411.737 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2016IET 1 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM SN2016IET 1 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM SN2016IET 1 WFC3/IR MULTIAC IR F110W 3 none none none 1 N/A CUM SN2016IET 1 WFC3/IR MULTIAC IR F110W 4 none none none 1 N/A CUM SN2016IET 2 WFC3/IR MULTIAC IR F160W 1 none none none 2 N/A CUM SN2016IET 2 WFC3/IR MULTIAC IR F160W 2 none none none 2 N/A CUM SN2016IET 2 WFC3/IR MULTIAC IR F160W 3 none none none 2 N/A CUM SN2016IET 2 WFC3/IR MULTIAC IR F160W 4 none none none 2 N/A CUM 16215( 2) - 03-Jun-2020 16:34:37 - [ 6] Visit: 02 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 SN2016IET ACS/WFC ACCUM WFC2 F625W 1 522 S PATTERN 3 1 (2088 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2016IET 1 ACS/WFC ACCUM WFC2 F625W 1 none none none 1 N/A SN2016IET 1 ACS/WFC ACCUM WFC2 F625W 2 none none none 1 N/A SN2016IET 1 ACS/WFC ACCUM WFC2 F625W 3 none none none 1 N/A SN2016IET 1 ACS/WFC ACCUM WFC2 F625W 4 none none none 1 N/A 16215( 2) - 03-Jun-2020 16:34:37 - [ 7] Summary Form for Proposal 16215 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, WFC2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=7, SAMP-SEQ=SPARS100 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 01, 02 WITHIN 30D, GS ACQ SCENARIO BASE1B3, PATTERN 1 1, PATTERN 1 2, PATTERN 3 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W, F160W, F625W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN2016IET ------------------------------------------------------------------------------------------------------------------------------------