17907( 2) - 22-Jan-2025 13:43:54 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17907 Version: 2 Check-in Time: 22-Jan-2025 13:43:54 STScI Edit Number: 0 Title One Last Time: HST/ACS Imaging of the Peculiar White Dwarf Supernova 2012Z ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Michaela Grace Schwab Rutgers the State University of New Jersey Y CoI: Dr. Saurabh W. Jha Rutgers the State University of New Jersey N CoI: Dr. Huei Sears Rutgers the State University of New Jersey N CoI: Dr. Lindsey Kwok Northwestern University N CoI: Dr. Curtis McCully Las Cumbres Observatory Global Telescope N Network CoI: Prof. Ryan Foley University of California - Santa Cruz N CoI: Conor Larison Rutgers the State University of New Jersey N CoI: Dr. Or Graur University of Portsmouth N ------------------------------------------------------------------------------------ Abstract Type Ia supernovae (SNe Ia) play a central role in cosmology, stellar evolution, and cosmic chemical enrichment. Nonetheless, their progenitors and explosion mechanisms remain uncertain. The classic model -- a Chandrasekhar-mass white dwarf (WD) accreting mass from a non-degenerate companion -- may not explain normal SNe Ia, but aligns well with observations of the peculiar Type Iax supernova (SN Iax) subclass. Intriguingly, pure deflagration (subsonic) explosion models of SNe Iax predict that the WD may not be completely disrupted, potentially leaving behind a bound remnant. SN Iax 2012Z offers an exceptional opportunity to stringently test this scenario. Deep pre-explosion HST ACS/WFC imaging of its host galaxy, NGC 1309, revealed a luminous, blue helium star thought to be the companion of the exploding WD. Subsequent ACS/WFC imaging at the location of SN 2012Z in 2016 and 2019 revealed that, remarkably, this source is still visible with a persistent flux excess beyond that expected from the companion star alone. We propose one final ACS/WFC observation, six years after the last, allowing for image subtraction to conclusively determine whether this mysterious flux excess originates from a bound remnant driving a radioactive wind or from shock-heating of the ejecta-blasted companion star. This observation will cement the legacy of HST in elucidating the origins of SNe Iax. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain late-time optical ACS/WFC BVI images at the location of SN 2012Z in NGC 1309 to look for further changes in the system. We have constructed our proposed observations to match the ACS/WFC data from Cycles 22 and 25 in filters and depth, allowing us to also compare with the pre-explosion ACS images and photometry of S1. Our best measurement of any changes from the pre-explosion and Cycle 22 or 25 images will come from image-subtraction analysis, so we request a similar orientation range as those data. We will use dithering and subsampling to improve the spatial resolution 17907( 2) - 22-Jan-2025 13:43:54 - [ 2] of the ACS images, as we did in our previous observations, and thus request the same orientation for all visits. We divide our 14-orbit allocation into 5 visits, 4 visits of 3 orbits each in all three filters (F435W, F555W, and F814W) and 1 visit of 2 orbits in two filters (F555W and F814W). This yields a total exposure time of over 9000 sec in F435W and approximately 11500 sec in F555W and F814W. ------------------------------------------------------------------------------------ 17907( 2) - 22-Jan-2025 13:43:54 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN-2012Z EXT-STAR, SUPERNOVA RA=03H22M5.3500S, J2000 V = 27.6 +/- 2.0 DEC=-15D23'15.60" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 17907( 2) - 22-Jan-2025 13:43:54 - [ 4] Visit: 01 Visit Requirements: SCHED 70%; ORIENT 240D TO 80 D 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 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG 0.000, 0.000 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG 0.247, 0.094 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG 0.247, 0.094 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG 0.000, 0.000 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG 0.000, 0.000 (1153 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG 0.247, 0.094 (1153 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN-2012Z 1 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 2 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 3 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 4 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 5 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A SN-2012Z 6 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A 17907( 2) - 22-Jan-2025 13:43:54 - [ 5] Visit: 02 Visit Requirements: SCHED 70%; 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 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG 0.124, 0.232 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG -0.124, 0.138 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG -0.124, 0.138 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG 0.124, 0.232 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG 0.124, 0.232 (1153 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG -0.124, 0.138 (1153 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN-2012Z 1 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 2 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 3 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 4 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 5 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A SN-2012Z 6 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A 17907( 2) - 22-Jan-2025 13:43:54 - [ 6] Visit: 03 Visit Requirements: SCHED 70%; 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 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG 0.000, 0.000 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG 0.247, 0.094 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG 0.247, 0.094 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG 0.000, 0.000 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG 0.000, 0.000 (1153 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG 0.247, 0.094 (1153 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN-2012Z 1 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 2 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 3 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 4 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 5 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A SN-2012Z 6 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A 17907( 2) - 22-Jan-2025 13:43:54 - [ 7] Visit: 04 Visit Requirements: SCHED 70%; 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 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG 0.124, 0.232 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2012Z ACS/WFC ACCUM WFC1 F435W 1 1132 S POS TARG -0.124, 0.138 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG -0.124, 0.138 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1162 S POS TARG 0.124, 0.232 (1162 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG 0.124, 0.232 (1153 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1153 S POS TARG -0.124, 0.138 (1153 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN-2012Z 1 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 2 ACS/WFC ACCUM WFC1 F435W none none none none 1 N/A SN-2012Z 3 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 4 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 5 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A SN-2012Z 6 ACS/WFC ACCUM WFC1 F555W none none none none 3 N/A 17907( 2) - 22-Jan-2025 13:43:54 - [ 8] Visit: 05 Visit Requirements: SCHED 70%; 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 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1132 S POS TARG 0.000, 0.000 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2012Z ACS/WFC ACCUM WFC1 F555W 1 1132 S POS TARG 0.247, 0.094 (1132 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1153 S POS TARG 0.247, 0.094 (1153 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2012Z ACS/WFC ACCUM WFC1 F814W 1 1153 S POS TARG 0.000, 0.000 (1153 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN-2012Z 1 ACS/WFC ACCUM WFC1 F555W none none none none 1 N/A SN-2012Z 2 ACS/WFC ACCUM WFC1 F555W none none none none 1 N/A SN-2012Z 3 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A SN-2012Z 4 ACS/WFC ACCUM WFC1 F814W none none none none 2 N/A 17907( 2) - 22-Jan-2025 13:43:54 - [ 9] Summary Form for Proposal 17907 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 240D TO 80 D, POS TARG -0.124, 0.138, POS TARG 0.000, 0.000, POS TARG 0.124, 0.232, POS TARG 0.247, 0.094, SAME ORIENT AS 01, SCHED 70% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F435W, F555W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN-2012Z ------------------------------------------------------------------------------------------------------------------------------------