18349( 2) - 18-Aug-2026 14:57:12 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18349 Version: 2 Check-in Time: 18-Aug-2026 14:57:12 STScI Edit Number: 0 Title Echoes of Dying Breaths: Measuring Mass Loss with Late-time Observations of SN 2023ixf and SN 2024ggi ------------------------------------------------------------------------------------ Type Cycle GO 34 ------------------------------------------------------------------------------------ Investigators Contact? PI: Jeniveve Pearson University of Arizona Y CoI: Dr. Jennifer Andrews NOIRLab - Gemini North (HI) N CoI: Brian Hsu University of Arizona N CoI: Prof. Griffin Hosseinzadeh University of California - San Diego N CoI: Dr. Sergiy Sergiyovich Vasylyev University of California - San Diego N CoI: Prof. David J. Sand University of Arizona N CoI: Dr. Bhagya Subrayan University of Arizona N CoI: Dr. Kyra Azalee Bostroem California Institute of Technology N CoI: Dr. Conor Ransome University of Arizona N CoI: Dr. Aravind Pazhayath Ravi University of California - Davis N CoI: Prof. Stefano Valenti University of California - Davis N CoI: Mr. Nicolas Eduardo Meza Retamal University of California - Davis N CoI: Ms. Darshana Mehta University of California - Davis N CoI: Dr. Manisha Shrestha Monash University N ------------------------------------------------------------------------------------ Abstract A growing number of Type IIP supernovae (SNe IIP) display early and sustained circumstellar medium (CSM) interaction, requiring CSM masses that challenge the observed mass-loss rates of their red supergiant progenitors. This suggests red supergiants may experience a period of enhanced mass loss at the end of their lives. SN 2023ixf and SN 2024ggi, the nearest and best-observed SNe IIP in the past decade, provide the ideal laboratory to understand this phenomenon. We propose multi-cycle HST imaging in the UV and optical to map the distribution and composition of the CSM surrounding SN 2023ixf and SN 2024ggi. These observations target two complementary probes: UV emission from ongoing ejecta-CSM interaction and optical light echoes from more distant material. Together, this data will constrain the geometry, radial extent, and density of the CSM, ultimately providing critical insight into the mechanisms that drive late-stage mass loss. Long-term HST imaging will add to existing and planned multi-wavelength observations and establish SN 2023ixf and SN 2024ggi as benchmark SNe IIP for decades to come. ------------------------------------------------------------------------------------ Observations Description ------------------------ In order to moniter the evolution of SN 2023ixf and SN 2024ggi we request 4 orbits total of WFC3/UVIS imaging. One for each supernovae to get F275W and F390W imaging (therefore 2 total) that will assess the evolution of any Mg II resulting from interaction between the circumstellar material and supernova ejecta. An additional orbit for each supernovae (2 total) will be for F438W, F555W, and F814W imaging to map the optical evolution and the creation of any light echoes. Both SN 2023ixf and SN 2024ggi are located in star forming regions in their respective host galaxies, we therefore opt to use the sub 18349( 2) - 18-Aug-2026 14:57:12 - [ 2] array to allow for shorter exposures of the regions. ------------------------------------------------------------------------------------ 18349( 2) - 18-Aug-2026 14:57:12 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN-2024GGI STAR, SUPERNOVA, RA=11H18M22.0870S, J2000 V = 21.5 SUPERNOVA TYPE II DEC=-32D50'15.27" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2023IXF STAR, SUPERNOVA, RA=14H03M38.5620S, J2000 V = 21.5 SUPERNOVA TYPE II DEC=+54D18'41.94" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 18349( 2) - 18-Aug-2026 14:57:12 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 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 ------------------------------------------------------------------------------------------------------------------------------------ 18349( 2) - 18-Aug-2026 14:57:12 - [ 5] Visit: 01 (23ixf UV) Visit Requirements: GROUP 01, 02 WITHIN 2 Orbits 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-2023IXF WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=20 1 604 S PATTERN 2 1-2 S 1C-SUB (1208 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2023IXF WFC3/UVI ACCUM UVIS2-C1K F390W 1 580 S S 1C-SUB (1160 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-2023IXF 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A S K1C-SUB SN-2023IXF 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A S K1C-SUB SN-2023IXF 2 WFC3/UVI ACCUM UVIS2-C1 F390W 1 none none none 1 N/A S K1C-SUB SN-2023IXF 2 WFC3/UVI ACCUM UVIS2-C1 F390W 2 none none none 1 N/A S K1C-SUB 18349( 2) - 18-Aug-2026 14:57:12 - [ 6] Visit: 02 (23ixf Opt) Visit Requirements: GROUP 02, 01 WITHIN 2 Orbits 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-2023IXF WFC3/UVI ACCUM UVIS2-C1K F438W 1 362 S (724 PATTERN 2 1-3 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2023IXF WFC3/UVI ACCUM UVIS2-C1K F555W 1 362 S (724 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2023IXF WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 362 S (724 S 1C-SUB 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-2023IXF 1 WFC3/UVI ACCUM UVIS2-C1 F438W 1 none none none 1 N/A S K1C-SUB SN-2023IXF 1 WFC3/UVI ACCUM UVIS2-C1 F438W 2 none none none 1 N/A S K1C-SUB SN-2023IXF 2 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none none none 1 N/A S K1C-SUB SN-2023IXF 2 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none none none 1 N/A S K1C-SUB SN-2023IXF 3 WFC3/UVI ACCUM UVIS2-C1 F814W 1 none none none 1 N/A S K1C-SUB SN-2023IXF 3 WFC3/UVI ACCUM UVIS2-C1 F814W 2 none none none 1 N/A S K1C-SUB 18349( 2) - 18-Aug-2026 14:57:12 - [ 7] Visit: 03 (24ggi UV) Visit Requirements: GROUP 03, 04 WITHIN 2 Orbits 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-2024GGI WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=20 1 600 S PATTERN 2 1-2 S 1C-SUB see below (1234 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2024GGI WFC3/UVI ACCUM UVIS2-C1K F390W 1 530 S S 1C-SUB see below (1094 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-2024GGI 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 617.0 S S K1C-SUB SN-2024GGI 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 617.0 S S K1C-SUB SN-2024GGI 2 WFC3/UVI ACCUM UVIS2-C1 F390W 1 none none none 1 547.0 S S K1C-SUB SN-2024GGI 2 WFC3/UVI ACCUM UVIS2-C1 F390W 2 none none none 1 547.0 S S K1C-SUB 18349( 2) - 18-Aug-2026 14:57:12 - [ 8] Visit: 04 (24ggi Opt) Visit Requirements: GROUP 04, 03 WITHIN 2 Orbits 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-2024GGI WFC3/UVI ACCUM UVIS2-C1K F438W 1 356 S (712 PATTERN 2 1-3 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2024GGI WFC3/UVI ACCUM UVIS2-C1K F555W 1 356 S (712 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2024GGI WFC3/UVI ACCUM UVIS2-C1K F814W FLASH=5 1 356 S (712 S 1C-SUB 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-2024GGI 1 WFC3/UVI ACCUM UVIS2-C1 F438W 1 none none none 1 N/A S K1C-SUB SN-2024GGI 1 WFC3/UVI ACCUM UVIS2-C1 F438W 2 none none none 1 N/A S K1C-SUB SN-2024GGI 2 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none none none 1 N/A S K1C-SUB SN-2024GGI 2 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none none none 1 N/A S K1C-SUB SN-2024GGI 3 WFC3/UVI ACCUM UVIS2-C1 F814W 1 none none none 1 N/A S K1C-SUB SN-2024GGI 3 WFC3/UVI ACCUM UVIS2-C1 F814W 2 none none none 1 N/A S K1C-SUB 18349( 2) - 18-Aug-2026 14:57:12 - [ 9] Summary Form for Proposal 18349 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=20, FLASH=5 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 01, 02 WITHIN 2 Orbits, GROUP 02, 01 WITHIN 2 Orbits, GROUP 03, 04 WITHIN 2 Orbits, GROUP 04, 03 WITHIN 2 Orbits, PATTERN 2 1-2, PATTERN 2 1-3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F275W, F390W, F438W, F555W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN-2023IXF, SN-2024GGI ------------------------------------------------------------------------------------------------------------------------------------