17596( 6) - 12-Jul-2024 20:32:33 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17596 Version: 6 Check-in Time: 12-Jul-2024 20:32:33 STScI Edit Number: 2 Title Revealing the Powering Mechanisms of Type Icn Supernovae through Late-time Observations ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Craig Pellegrino The University of Virginia Y CoI: Prof. Maryam Modjaz The University of Virginia N CoI: Dr. Tyler Pritchard New York University N CoI: Kyle Davis University of California - Santa Cruz N CoI: Prof. Ryan Foley University of California - Santa Cruz N ------------------------------------------------------------------------------------ Abstract We propose to obtain two epochs of HST imaging of supernova (SN) 2023xgo, the closest Type Icn SN to date (d = 62 Mpc), between 120 to 300 days after explosion in order to constrain its late-time powering mechanism. Type Icn SNe are a rare but astrophysically-interesting class of transients powered by interaction with H- and He-poor circumstellar material-- evidence that their uncertain progenitor stars underwent extraordinary mass loss before explosion. A better understanding of their progenitors and mass-loss mechanisms will impact theories of stellar evolution and the formation of gravitational wave sources. Modeling the light curves of these objects has surprisingly revealed that their explosions produce little, if any, radioactive 56Ni. Progenitor scenarios that permit such little 56Ni include the explosion of a massive Wolf-Rayet star undergoing significant fallback accretion, or of an ultra-stripped, lower-mass (<= 12 Msun) star. We request late-time photometric observations in order to differentiate between the proposed progenitor scenarios by estimating the explosive nucleosynthetic yields and by searching for evidence of ongoing interaction with material at larger distances from the progenitor star. These observations will further constrain radioactive decay as a powering mechanism for synthesized 56Ni masses >= 0.001 Msun. The low redshift of SN 2023xgo and its optimal phase throughout Cycle 31 offer the first possibility to observe the late-time light curve of a Type Icn SN to date. These observations will directly probe the progenitor properties of these rare and exotic transients, informing our understanding of the extremes of mass loss in massive stars. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose two visits, each comprising of two orbits, to image the nearby supernova SN 2023xgo with the WFC3/UVIS F606W and F814W bands as well as the WFC3/IR F125W and F160W bands. We will use the first orbit in each visit to image SN 2023xgo with WFC3/UVIS in the F606W and F814W filters, and the second orbit in each visit to image SN 2023xgo with WFC3/IR in the F125W and F160W filters. We request that our first visit be scheduled on 22 March 2024 and our second visit on 20 July 2024. This window fits our criterion of having two visits separated by at most 120 days. During this time frame we expect the brightness 17596( 6) - 12-Jul-2024 20:32:33 - [ 2] of SN 2023xgo to be within our proposed range of V band magnitude 24.0 +/- 2.0. In particular, obtaining our first observation on 22 March is vital as the supernova will not be visible to HST again until mid July. Waiting until that time for our first visit runs the risk that the supernova will be too faint to observe by the second visit. For each visit, our observation plan is as follows. In our first orbit, we will utilize the WFC3-UVIS-DITHER-LINE pattern with the F606W and F814W filters. We request a total of 1200s of exposure time in F606W and 1432s of exposure time in F814W, each split evenly between two exposures. In our second orbit, we will utilize the WFC3-IR-DITHER-BOX-MIN pattern with the F125W and F160W filters. For each filter, we request a total of ~1312s of exposure time, split evenly into four exposures. We expect these observations to be unaffected by the possibility of reduced gyro operations during Cycle 31. These observations do not rely on utilizing HST's full field of view, nor on its normal spatial scan speed. ------------------------------------------------------------------------------------ 17596( 6) - 12-Jul-2024 20:32:33 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN2023XGO EXT-STAR, EJECTA, RA=05H04M19.1900S +/- 1", J2000 Z = V = 24.0 +/- 2.0 SUPERNOVA DEC=+67D37'21.10" +/- 1" 0.014 Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 17596( 6) - 12-Jul-2024 20:32:33 - [ 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 1.716 Line_Spacing 1.095 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17596( 6) - 12-Jul-2024 20:32:33 - [ 5] Visit: 01 Visit Requirements: BETWEEN 12-MAR-2024:00:00:00 AND 20-JUL-2024:00:00:00 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 SN2023XGO WFC3/UVI ACCUM UVIS2-C1K F606W 1 600 S PATTERN 1 1-2 S 1C-SUB (1200 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2023XGO WFC3/UVI ACCUM UVIS2-C1K F814W 1 716 S S 1C-SUB (1432 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2023XGO WFC3/IR MULTIAC IR F125W NSAMP=14, SAMP-SEQ=SPARS25 1 DEF PATTERN 2 3-4 CUM (1311.756 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2023XGO WFC3/IR MULTIAC IR F160W NSAMP=14, SAMP-SEQ=SPARS25 1 DEF CUM (1311.756 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023XGO 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none none none 1 N/A S K1C-SUB SN2023XGO 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none none none 1 N/A S K1C-SUB SN2023XGO 2 WFC3/UVI ACCUM UVIS2-C1 F814W 1 none none none 1 N/A S K1C-SUB SN2023XGO 2 WFC3/UVI ACCUM UVIS2-C1 F814W 2 none none none 1 N/A S K1C-SUB SN2023XGO 3 WFC3/IR MULTIAC IR F125W 1 none none none 2 N/A CUM SN2023XGO 3 WFC3/IR MULTIAC IR F125W 2 none none none 2 N/A CUM SN2023XGO 3 WFC3/IR MULTIAC IR F125W 3 none none none 2 N/A CUM SN2023XGO 3 WFC3/IR MULTIAC IR F125W 4 none none none 2 N/A CUM SN2023XGO 4 WFC3/IR MULTIAC IR F160W 1 none none none 2 N/A CUM SN2023XGO 4 WFC3/IR MULTIAC IR F160W 2 none none none 2 N/A CUM SN2023XGO 4 WFC3/IR MULTIAC IR F160W 3 none none none 2 N/A CUM 17596( 6) - 12-Jul-2024 20:32:33 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023XGO 4 WFC3/IR MULTIAC IR F160W 4 none none none 2 N/A CUM 17596( 6) - 12-Jul-2024 20:32:33 - [ 7] Visit: 02 Visit Requirements: AFTER 01 BY 30 D TO 120 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 SN2023XGO WFC3/UVI ACCUM UVIS2-C1K F606W 1 551 S PATTERN 1 1-2 S 1C-SUB (1102 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2023XGO WFC3/UVI ACCUM UVIS2-C1K F814W 1 667 S S 1C-SUB (1334 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2023XGO WFC3/IR MULTIAC IR F125W NSAMP=13, SAMP-SEQ=SPARS25 1 DEF PATTERN 2 3-4 CUM (1211.754 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2023XGO WFC3/IR MULTIAC IR F160W NSAMP=12, SAMP-SEQ=SPARS25 1 DEF CUM (1111.752 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023XGO 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none none none 1 N/A S K1C-SUB SN2023XGO 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none none none 1 N/A S K1C-SUB SN2023XGO 2 WFC3/UVI ACCUM UVIS2-C1 F814W 1 none none none 1 N/A S K1C-SUB SN2023XGO 2 WFC3/UVI ACCUM UVIS2-C1 F814W 2 none none none 1 N/A S K1C-SUB SN2023XGO 3 WFC3/IR MULTIAC IR F125W 1 none none none 2 N/A CUM SN2023XGO 3 WFC3/IR MULTIAC IR F125W 2 none none none 2 N/A CUM SN2023XGO 3 WFC3/IR MULTIAC IR F125W 3 none none none 2 N/A CUM SN2023XGO 3 WFC3/IR MULTIAC IR F125W 4 none none none 2 N/A CUM SN2023XGO 4 WFC3/IR MULTIAC IR F160W 1 none none none 2 N/A CUM SN2023XGO 4 WFC3/IR MULTIAC IR F160W 2 none none none 2 N/A CUM SN2023XGO 4 WFC3/IR MULTIAC IR F160W 3 none none none 2 N/A CUM 17596( 6) - 12-Jul-2024 20:32:33 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023XGO 4 WFC3/IR MULTIAC IR F160W 4 none none none 2 N/A CUM 17596( 6) - 12-Jul-2024 20:32:33 - [ 9] Visit: 03 Visit Requirements: AFTER 02 BY 30 D TO 60 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 SN2023XGO WFC3/UVI ACCUM UVIS2-C1K F606W 1 600 S PATTERN 1 1-2 S 1C-SUB see below (1102 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2023XGO WFC3/UVI ACCUM UVIS2-C1K F814W 1 716 S S 1C-SUB see below (1334 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2023XGO 1 WFC3/UVI ACCUM UVIS2-C1 F606W 1 none none none 1 551.0 S S K1C-SUB SN2023XGO 1 WFC3/UVI ACCUM UVIS2-C1 F606W 2 none none none 1 551.0 S S K1C-SUB SN2023XGO 2 WFC3/UVI ACCUM UVIS2-C1 F814W 1 none none none 1 667.0 S S K1C-SUB SN2023XGO 2 WFC3/UVI ACCUM UVIS2-C1 F814W 2 none none none 1 667.0 S S K1C-SUB 17596( 6) - 12-Jul-2024 20:32:33 - [ 10] Summary Form for Proposal 17596 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=12, NSAMP=13, NSAMP=14, SAMP-SEQ=SPARS25 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 30 D TO 120 D, AFTER 02 BY 30 D TO 60 D, BETWEEN 12-MAR-2024:00:00:00 AND 20-JUL-2024:00:00:00, PATTERN 1 1-2, PATTERN 2 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F125W, F160W, F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN2023XGO ------------------------------------------------------------------------------------------------------------------------------------