17300( 3) - 28-Apr-2023 15:22:15 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17300 Version: 3 Check-in Time: 28-Apr-2023 15:22:15 STScI Edit Number: 1 Title Probing the Post-genitor System of Calcium-rich Transient SN 2021gno ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Wynn Vicente Jacobson-Galan University of California - Berkeley Y CoI: Dr. Raffaella Margutti University of California - Berkeley N CoI: Prof. Ryan Foley University of California - Santa Cruz N CoI: Dr. Charles Kilpatrick Northwestern University N CoI: David Coulter University of California - Santa Cruz N CoI: Dr. Armin Rest Space Telescope Science Institute N CoI: Dr. Yossef Zenati The Johns Hopkins University N CoI: Dr. Ken Shen University of California - Berkeley N CoI: Huei Sears Northwestern University N CoI: Dr. Katie Auchettl University of Melbourne N CoI: Prof. Ashley Villar The Pennsylvania State University N ------------------------------------------------------------------------------------ Abstract Supernova (SN) 2021gno in NGC 4165 (D=30.5 Mpc) is the second closest known Calcium-rich (Ca-rich) transient and only the second object in this class with an X-ray detection. Prompt, high-cadence follow-up of this transient across the EM spectrum indicated that the progenitor star was likely low mass (e.g., a white dwarf or a <10 Msun star) and surrounded by a dense shell of circumstellar material (CSM) whose geometry/density was capable of producing luminous X-ray emission as well as a double-peaked optical light curve. The close proximity of SN 2021gno provided only the second opportunity to obtain multi-color HST observations out to ~450 days post explosion, which indicate a pure radioactive decay power source. Ca-rich transients typically decrease in magnitude rapidly and therefore their extremely late-time decline rate and power source at t>700 days is completely unknown. Here we propose multi-color imaging of SN 2021gno in order to search for emission from a bound remnant white dwarf as predicted by a favored progenitor model for this explosion. Detection and characterization of such a remnant will be the most substantial proof of a WD origin for a Ca-rich transient to date and will provide a novel window into the explosion mechanism. Additionally, these observations will provide one of the best constraints to date on a potential non-degenerate companion star in any thermonuclear SN progenitor system, such as Ca-rich SNe. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to observe nearby supernova 2021gno with WFC3/UVIS in filters F555W and F814W in the first of our two allocated orbits. In the second orbit, we will observe SN 2021gno with WFC3/IR in filter F160W. Our optimal observing window is between 07-May-2023 and 18-June-2023, however, 22-June-2023 to 27-July-2023 is another acceptable scheduling window. We have requested that IR imaging be taken within 3 days of the UVIS imaging orbit. Below is our observing plan for each filter in each orbit: 17300( 3) - 28-Apr-2023 15:22:15 - [ 2] Orbit 1: F555W: Total Exposure time = 1500s; Split into two 750s exposures using WFC3-UVIS-DITHER-LINE pattern F814W: Total Exposure time = 900s; Split into two 450s exposures using WFC3-UVIS-DITHER-LINE pattern Orbit 2: F160W: Eight ~300s individual exposures for each filter using the WFC3-IR-DILTER-BOX-MIN pattern. ------------------------------------------------------------------------------------ 17300( 3) - 28-Apr-2023 15:22:15 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN2021GNO STAR, SUPERNOVA RA=12H12M10.2900S, J2000 V = 25 g ~ 26-27, r ~ 25, i/z ~ 24 DEC=+13D14'57.04" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 17300( 3) - 28-Apr-2023 15:22:15 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 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 ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.572 Line_Spacing 0.365 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17300( 3) - 28-Apr-2023 15:22:15 - [ 5] Visit: 01 (UVIS/IR Orbits) Visit Requirements: On Hold Comments: Additional Comments: Orbit 1: Filters: F555W, F814W Orbit 2: Filters: F160W 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 SN2021GNO WFC3/UVI ACCUM UVIS F814W FLASH=10 1 450 S PATTERN 1 1-2 S see below (864 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2021GNO WFC3/UVI ACCUM UVIS F555W 1 750 S S see below (1460 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2021GNO WFC3/IR MULTIAC IR F160W NSAMP=13, SAMP-SEQ=SPARS25 1 DEF PATTERN 2 3-4 CUM (1211.754 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2021GNO WFC3/IR MULTIAC IR F160W NSAMP=13, SAMP-SEQ=SPARS25 1 DEF CUM (1211.754 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2021GNO 1 WFC3/UVI ACCUM UVIS F814W 1 none none none 1 432.0 S S SN2021GNO 1 WFC3/UVI ACCUM UVIS F814W 2 none none none 1 432.0 S S SN2021GNO 2 WFC3/UVI ACCUM UVIS F555W 1 none none none 1 730.0 S S SN2021GNO 2 WFC3/UVI ACCUM UVIS F555W 2 none none none 1 730.0 S S SN2021GNO 3 WFC3/IR MULTIAC IR F160W 1 none none none 2 N/A CUM SN2021GNO 3 WFC3/IR MULTIAC IR F160W 2 none none none 2 N/A CUM SN2021GNO 3 WFC3/IR MULTIAC IR F160W 3 none none none 2 N/A CUM SN2021GNO 3 WFC3/IR MULTIAC IR F160W 4 none none none 2 N/A CUM 17300( 3) - 28-Apr-2023 15:22:15 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2021GNO 4 WFC3/IR MULTIAC IR F160W 1 none none none 2 N/A CUM SN2021GNO 4 WFC3/IR MULTIAC IR F160W 2 none none none 2 N/A CUM SN2021GNO 4 WFC3/IR MULTIAC IR F160W 3 none none none 2 N/A CUM SN2021GNO 4 WFC3/IR MULTIAC IR F160W 4 none none none 2 N/A CUM 17300( 3) - 28-Apr-2023 15:22:15 - [ 7] Summary Form for Proposal 17300 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, UVIS ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=10, NSAMP=13, SAMP-SEQ=SPARS25 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-2, PATTERN 2 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160W, F555W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN2021GNO ------------------------------------------------------------------------------------------------------------------------------------