17706( 6) - 18-Sep-2025 13:49:30 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17706 Version: 6 Check-in Time: 18-Sep-2025 13:49:30 STScI Edit Number: 0 Title Finding Supernova Progenitor Stars in HST and JWST Imaging ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Charles Kilpatrick Northwestern University Y CoI: Prof. Ryan Foley University of California - Santa Cruz N CoI: jason vazquez University of Illinois at Urbana - N Champaign CoI: Dr. Alexander Thomas Gagliano Massachusetts Institute of Technology N CoI: Kyle Davis University of California - Santa Cruz N CoI: Dr. Kirsty Taggart University of California - Santa Cruz N CoI: Dr. Wynn Vicente Jacobson-Galan California Institute of Technology N ------------------------------------------------------------------------------------ Abstract Many open questions in supernova (SN) physics rely on the connection between SNe and their progenitor stars. HST and now JWST provide a vast imaging archive of galaxies in the local Universe in which individual supernova progenitor stars can be isolated soon after they explode. Each new such event is a rare and unique opportunity in which we can compare a supernova explosion to the mass, metallicity, and local environments of the star that exploded. In many cases however, it is only possible to isolate the supernova progenitor star with high-resolution imaging follow up where local astrometric calibrators can be used to precisely align the supernova position with <0.1 arcsec precision. When adaptive optics imaging is not possible due to a lack of available guide stars, HST is the best available resource to obtain such follow-up imaging of the supernova. We propose a target-of-opportunity program to obtain such imaging with HST for 2 nearby (<40 Mpc) supernova targets during Cycle 32 that have pre-explosion HST or JWST imaging and precisely isolate the progenitor systems of these stellar explosions. ------------------------------------------------------------------------------------ Observations Description ------------------------ This is a target-of-opportunity proposal to observe up to 2 supernovae at <40 Mpc with pre-explosion HST and/or JWST imaging. The goal of the proposal is to obtain imaging at the site of each supernova in order to precisely align to the pre-explosion imaging and identify or rule out the presence of a counterpart in the pre-explosion data. We are requesting a 3 week minimum response time from the time of trigger in order to guarantee that we can calibrate our exposures to the expected brightness of the supernova at the time of observation and avoid either saturating or failing to detect the primary supernova target. Our fiducial observation setup assumes that we will observe the supernova around or slightly after maximum light, with a required brightness of >16.5 mag to avoid saturating this source, which would limit the astrometric precision in centroiding on the supernova. We therefore use 68s exposures in F555W and use the UVIS2-C1K1C-SUB readout mode to reduce overheads between individual 17706( 6) - 18-Sep-2025 13:49:30 - [ 2] exposures. As we are targeting sources in galaxies at <40 Mpc, we expect the field around the supernova to be crowded with astrometric calibrators, and so the smaller readout region will not limit our science case. We have also adjusted FLASH=15 to avoid CTE losses. To improve PSF sampling, we use 4 iterations of a WFC3-UVIS-DITHER-BOX pattern for a total of 16 individual exposures. ------------------------------------------------------------------------------------ 17706( 6) - 18-Sep-2025 13:49:30 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2025PHT STAR, SUPERNOVA RA=04H41M28.8340S, J2000 V = 14 DEC=-02D51'55.87" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2025QGD STAR, SUPERNOVA RA=10H27M51.0660S, J2000 V = 20 DEC=-43D54'20.96" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 17706( 6) - 18-Sep-2025 13:49:30 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 17706( 6) - 18-Sep-2025 13:49:30 - [ 5] Visit: 01 Visit Requirements: ON HOLD ; TOO RESPONSE TIME 21.0D On Hold Comments: Target of Opportunity Requirement is 21-60 days from initial trigger 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 SN2025PHT WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=16 4 68 S PATTERN 1 1 S 1C-SUB see below (1120 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none 1 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none 2 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none 3 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none 4 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none 1 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none 2 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none 3 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none 4 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none 1 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none 2 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none 3 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none 4 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 4 none 1 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 4 none 2 none 1 70.0 S S K1C-SUB SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 4 none 3 none 1 70.0 S S K1C-SUB 17706( 6) - 18-Sep-2025 13:49:30 - [ 6] 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2025PHT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 4 none 4 none 1 70.0 S S K1C-SUB 17706( 6) - 18-Sep-2025 13:49:30 - [ 7] Visit: 02 Visit Requirements: ON HOLD ; TOO RESPONSE TIME 21.0D On Hold Comments: Target of Opportunity Requirement is 21-60 days from initial trigger 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 SN2025QGD WFC3/UVI ACCUM UVIS2-C1K F555W FLASH=15 4 68 S PATTERN 1 1 S 1C-SUB see below (1120 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none 1 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none 2 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none 3 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none 4 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none 1 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none 2 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none 3 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none 4 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 3 none 1 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 3 none 2 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 3 none 3 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 3 none 4 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 4 none 1 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 4 none 2 none 1 70.0 S S K1C-SUB SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 4 none 3 none 1 70.0 S S K1C-SUB 17706( 6) - 18-Sep-2025 13:49:30 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2025QGD 1 WFC3/UVI ACCUM UVIS2-C1 F555W 4 none 4 none 1 70.0 S S K1C-SUB 17706( 6) - 18-Sep-2025 13:49:30 - [ 9] Summary Form for Proposal 17706 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=15, FLASH=16 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ON HOLD , PATTERN 1 1, TOO RESPONSE TIME 21.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W, F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN2025PHT, SN2025QGD ------------------------------------------------------------------------------------------------------------------------------------