17777( 7) - 16-Mar-2026 17:36:39 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17777 Version: 7 Check-in Time: 16-Mar-2026 17:36:39 STScI Edit Number: 1 Title Confirming the first progenitor candidate of a rare type Ibn supernova ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Kirsty Taggart University of California - Santa Cruz Y CoI: Kyle Davis University of California - Santa Cruz N CoI: Dr. Samaporn Tinyanont National Astronomical Research Institute N of Thailand CoI: Prof. Ryan Foley University of California - Santa Cruz N ------------------------------------------------------------------------------------ Abstract Type Ibn supernovae (SN Ibn) are hydrogen-poor SNe that interact with their hydrogen-poor circumstellar medium (CSM). They probe the advanced and little-understood stage of mass loss that strips helium from a massive star. SN 2023fyq is the closest SN Ibn to date at 18.2 Mpc. The explosion site of SN 2023fyq was imaged with HST in several filters (UV through NIR) 12 years before explosion, revealing a blue (B - V = 0.2) and luminous point source with M = -9.5 mag, consistent with either a WC/O-type star or a young cluster with a turnoff mass of >20 Msun. We propose to obtain 4 orbits of deep HST imaging approximately two years after explosion to confirm the progenitor of SN 2023fyq and to discern its cluster or single stellar system nature -- yielding the first progenitor identification for a SN Ibn. Such a discovery would be crucial to understanding the mass loss mechanism responsible for stripping 1/3 of all core-collapse supernova progenitors of their hydrogen and/or helium, and to understanding what a stripped star looks like before its explosion. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request 4 orbits of HST imaging in Cycle 32 to observe SN 2023fyq in 5 filters, 2 years after explosion. There filters will achieve a depth of ~26 mag (M=-6), and will allow us to confirm that the progentor candidate for SN 2023fyq.s ------------------------------------------------------------------------------------ 17777( 7) - 16-Mar-2026 17:36:39 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN2023FYQ EXT-STAR, SUPERNOVA RA=12H25M45.8700S, J2000 V = 26 TYPE IB DEC=+12D39'48.68" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 17777( 7) - 16-Mar-2026 17:36:39 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 4 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17777( 7) - 16-Mar-2026 17:36:39 - [ 4] Visit: 01 (Visit 1 -(F336W, F438W, F814W, F606W)) Visit Requirements: AFTER 01-JAN-2025:00:00:00 On Hold Comments: Additional Comments: Estimates magnitudes (all AB mag): - WFC3_UVIS1/F336W 26.28 - WFC3_UVIS1/F438W 26.28 - WFC3_UVIS1/F814W 26.20 - WFC3_UVIS1/F606W 26.05 For SNR 8: F336W = 1, 756 s - https://etc.stsci.edu/etc/results/WFC3UVIS.im.1923282/ F814W = 2, 210 s - https://etc.stsci.edu/etc/results/WFC3UVIS.im.1923285/ F606W = 571 s - https://etc.stsci.edu/etc/results/WFC3UVIS.im.1923288/ F438W = 2, 083 s - https://etc.stsci.edu/etc/results/WFC3UVIS.im.1923294/ Compared to previous imaging in 12185, the indidual exposure times are increased by: F336W 585s - 1.32 times longer than GO-12185, AGN is fainter here, star cluster near SN is brighter at 3, 366, so scaling counts is 4, 443 F438W 694s - 5.07 times longer than GO-12185, AGN is fainter here, star cluster near SN is brighter at 2, 933, scaling counts is 14, 870 F814W 736s - 1.51 times longer than GO-12185, AGN maximum counts were 5, 680, scaling up counts should be 8, 580, less than the 48, 000 DN Kept similar or same to previous program: F606W 270s in the middle betweem 160s and 400s, so kept the same F160W - kept the same because the AGN is already saturated in the previous exposures 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 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=15 1 585 S PATTERN 3 1-4 S 1C-SUB (1755 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F438W FLASH=15 1 694 S S 1C-SUB (2082 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F814W 1 736 S S 1C-SUB (2208 S) Comments: 552 ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F606W FLASH=8 1 190 S S 1C-SUB see below (770 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 | ------------------------------------------------------------------------------------------------------------------------------------ 17777( 7) - 16-Mar-2026 17:36:39 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023FYQ 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none none none 1 N/A S K1C-SUB SN2023FYQ 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none none none 2 N/A S K1C-SUB SN2023FYQ 1 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none none none 3 N/A S K1C-SUB SN2023FYQ 2 WFC3/UVI ACCUM UVIS2-C1 F438W 1 none none none 1 N/A S K1C-SUB SN2023FYQ 2 WFC3/UVI ACCUM UVIS2-C1 F438W 2 none none none 2 N/A S K1C-SUB SN2023FYQ 2 WFC3/UVI ACCUM UVIS2-C1 F438W 3 none none none 3 N/A S K1C-SUB SN2023FYQ 3 WFC3/UVI ACCUM UVIS2-C1 F814W 1 none none none 1 N/A S K1C-SUB SN2023FYQ 3 WFC3/UVI ACCUM UVIS2-C1 F814W 2 none none none 2 N/A S K1C-SUB SN2023FYQ 3 WFC3/UVI ACCUM UVIS2-C1 F814W 3 none none none 3 N/A S K1C-SUB SN2023FYQ 4 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none none none 1 270.0 S S K1C-SUB SN2023FYQ 4 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none none none 2 250.0 S S K1C-SUB SN2023FYQ 4 WFC3/UVI ACCUM UVIS2-C1 F606W 3 none none none 3 250.0 S S K1C-SUB 17777( 7) - 16-Mar-2026 17:36:39 - [ 6] Visit: 02 (Visit 2 - (F160W)) Visit Requirements: AFTER 01 BY 0 D TO 14 D On Hold Comments: Additional Comments: WFC3_IR/F160W - estimated magnitude (AB) : 25.807 For SNR 8 we need: ~1, 692 s - https://etc.stsci.edu/etc/results/WFC3IR.im.1923281/ In the previous F160W imaging, AGN counts of 51, 310 are indeed higher than the full-well saturation level of ~34, 000 DN. We choose the same NSAMP as the previous imaging, and do an 9-point dither patter using pos-targ, with each dither point having 2 exposures. To measure the time-varying SED, we ideally require observations to be performed taken as close together, at least within 2 months of each other. 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 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.0000, 0.0000 CUM (211.037 S) Comments: Since we are measuring the SED, which is varying in time, we group the two visits with the first visit occuring after January 2025, and the second visit occuring <2 weeks after the first. We use a 2 x 9-point dither pattern. ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.317, 0.041 CUM (211.037 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.635, 0.081 CUM (211.037 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.952, 0.041 CUM (211.037 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.046, 0.324 CUM (211.037 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.364, 0.365 CUM (211.037 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.682, 0.446 CUM (211.037 S) ------------------------------------------------------------------------------------------------------------------------------------ 17777( 7) - 16-Mar-2026 17:36:39 - [ 7] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 8 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.999, 0.365 CUM (211.037 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 SN2023FYQ WFC3/IR MULTIAC IRSUB512 F160W NSAMP=9, SAMP-SEQ=STEP25 2 DEF POS TARG 0.228, 0.527 CUM (211.037 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023FYQ 1 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 1 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM SN2023FYQ 2 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 2 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM SN2023FYQ 3 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 3 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM SN2023FYQ 4 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 4 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM SN2023FYQ 5 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 5 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM SN2023FYQ 6 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 6 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM SN2023FYQ 7 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 7 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM SN2023FYQ 8 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 8 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM 17777( 7) - 16-Mar-2026 17:36:39 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023FYQ 9 WFC3/IR MULTIAC IRSUB512 F160W none none 1 none 1 N/A CUM SN2023FYQ 9 WFC3/IR MULTIAC IRSUB512 F160W none none 2 none 1 N/A CUM 17777( 7) - 16-Mar-2026 17:36:39 - [ 9] Visit: 03 (Repeat of failed Visit 01 Orbit 1 - (F336W, F438W, F814W, F606W)) Visit Requirements: SCHED 100%; BEFORE 15-APR-2026:00:00:00 On Hold Comments: Additional Comments: Scheduling this repeat as soon as possible without causing disruption to the HST schedule and no later than April 15, 2026. I used SCHED 100 special observation requirement on the repeat. 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 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F438W FLASH=15 1 694 S S 1C-SUB see below (652 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=2 1 736 S S 1C-SUB see below (694 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F606W FLASH=11 1 190 S S 1C-SUB see below (148 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2023FYQ WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=16 1 293 S PATTERN 4 4 S 1C-SUB see below (540 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023FYQ 1 WFC3/UVI ACCUM UVIS2-C1 F438W none none none none 1 652.0 S S K1C-SUB SN2023FYQ 2 WFC3/UVI ACCUM UVIS2-C1 F814W none none none none 1 694.0 S S K1C-SUB SN2023FYQ 3 WFC3/UVI ACCUM UVIS2-C1 F606W none none none none 1 148.0 S S K1C-SUB SN2023FYQ 4 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none none none 1 270.0 S S K1C-SUB SN2023FYQ 4 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none none none 1 270.0 S S K1C-SUB 17777( 7) - 16-Mar-2026 17:36:39 - [ 10] Summary Form for Proposal 17777 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IRSUB512, UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=11, FLASH=15, FLASH=16, FLASH=2, FLASH=8, NSAMP=9, SAMP-SEQ=STEP25 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 0 D TO 14 D, AFTER 01-JAN-2025:00:00:00, BEFORE 15-APR-2026:00:00:00, PATTERN 3 1-4, PATTERN 4 4, POS TARG 0.0000, 0.0000, POS TARG 0.046, 0.324, POS TARG 0.228, 0.527, POS TARG 0.317, 0.041, POS TARG 0.364, 0.365, POS TARG 0.635, 0.081, POS TARG 0.682, 0.446, POS TARG 0.952, 0.041, POS TARG 0.999, 0.365, SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160W, F336W, F438W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN2023FYQ ------------------------------------------------------------------------------------------------------------------------------------