18109( 5) - 30-Jan-2026 16:34:07 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18109 Version: 5 Check-in Time: 30-Jan-2026 16:34:07 STScI Edit Number: 0 Title Lightning Strikes Twice: A Panchromatic View of Shock Power in the Closest Type II Supernovae of the Decade ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Wynn Vicente Jacobson-Galan California Institute of Technology Y CoI: Dr. Luc Dessart CNRS, Institut d'Astrophysique de Paris N CoI: Dr. Mansi Kasliwal California Institute of Technology N CoI: Dr. Ori Dosovitz Fox Space Telescope Science Institute N CoI: Dr. Armin Rest Space Telescope Science Institute N CoI: Prof. Ryan Chornock University of California - Berkeley N CoI: Prof. Ryan Foley University of California - Santa Cruz N CoI: Dr. Suvi Gezari University of Maryland N CoI: Dr. Matthew Ryan Siebert Space Telescope Science Institute N CoI: Prof. Alex V. Filippenko University of California - Berkeley N CoI: Dr. Melissa Shahbandeh Space Telescope Science Institute N CoI: Dr. Qinan Wang Massachusetts Institute of Technology N CoI: Kyle Davis University of California - Santa Cruz N CoI: Dr. Raffaella Margutti University of California - Berkeley N CoI: Nayana AJ University of California - Berkeley N CoI: Dr. Charles Kilpatrick Northwestern University N ------------------------------------------------------------------------------------ Abstract Late-time observations of type II supernovae (SNe II) are a window into the uncertain mass-loss history of their red supergiant (RSG) star progenitors as well as a direct probe of the physics of shock interaction as SN ejecta collide with distant circumstellar material (CSM). We propose a long term monitoring program to obtain HST UV spectroscopy of SNe II 2023ixf and 2024ggi, the closest SNe of the decade, that currently show excess X-ray-to-radio emission at late-times from on-going CSM interaction. This unprecedented multi-wavelength campaign will enable the first spectral energy distributions of their kind, capable of directly constraining the unknown thermalization efficiency of radiation produced by the SN shock and the characterization of UV emission line spectra from the post-shock gas. These observations will also directly constrain the highly debated mass-loss histories of RSGs in the final centuries-to-millenia before core-collapse. ------------------------------------------------------------------------------------ Observations Description ------------------------ This program is to observe SN 2023ixf and SN 2024ggi in the FUV and NUV. Each object will be observed once during Cycle 33 with 4 orbits (2 FUV, 2 NUV) per object. The faintest SN 2023ixf will be during the cycle is V=20mag and the faintest SN 2024ggi will be is V=21 mag. ------------------------------------------------------------------------------------ 18109( 5) - 30-Jan-2026 16:34:07 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN-2023IXF EXT-STAR, SUPERNOVA RA=14H03M38.5620S, J2000 V = 19.5 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 ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2024GGI EXT-STAR, SUPERNOVA RA=11H18M22.0870S, J2000 V = 18 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 ------------------------------------------------------------------------------------------------------------------------------------ 3 SN23IXF-OFFS EXT-STAR, K V-IV RA=14H03M39.8499S +/- 0.03", J2000 V = 20.5 ET-LEGACY531 DEC=+54D18'6.99" +/- 0.03" 3 Reference Frame: ICRS Comments: g=20.48, r=20.43, z=20.39 ------------------------------------------------------------------------------------------------------------------------------------ 18109( 5) - 30-Jan-2026 16:34:07 - [ 3] Visit: 01 (2023ixf - Epoch 1 - FUV) Visit Requirements: 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 SN23IXF-OFF STIS/CCD ACQ F28X50LP MIRROR 1 50 S (50 SET-LEGACY5 S) 313 ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2023IXF STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=8000 1 1919 S -MAMA G (1919 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN23IXF-OFF STIS/CCD ACQ F28X50LP MIRROR 1 50 S (50 SET-LEGACY5 S) 313 ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2023IXF STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=8000 1 1755 S -MAMA G (1755 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN23IXF-OFFSET-LEGA 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A CY5313 SN-2023IXF 2 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 1 N/A -MAMA G SN23IXF-OFFSET-LEGA 3 STIS/CCD ACQ F28X50LP MIRROR none none none none 2 N/A CY5313 SN-2023IXF 4 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 2 N/A -MAMA G 18109( 5) - 30-Jan-2026 16:34:07 - [ 4] Visit: 02 (2023ixf - Epoch 1 - NUV) Visit Requirements: 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 SN23IXF-OFF STIS/CCD ACQ F28X50LP MIRROR 1 50 S (50 SET-LEGACY5 S) 313 ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2023IXF STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=1200 1 1919 S -MAMA G (1919 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN23IXF-OFF STIS/CCD ACQ F28X50LP MIRROR 1 50 S (50 SET-LEGACY5 S) 313 ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2023IXF STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=1200 1 1735 S -MAMA G (1735 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN23IXF-OFFSET-LEGA 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A CY5313 SN-2023IXF 2 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 N/A -MAMA G SN23IXF-OFFSET-LEGA 3 STIS/CCD ACQ F28X50LP MIRROR none none none none 2 N/A CY5313 SN-2023IXF 4 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 2 N/A -MAMA G 18109( 5) - 30-Jan-2026 16:34:07 - [ 5] Visit: 03 (2024ggi - Epoch 1 - FUV) Visit Requirements: 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 STIS/CCD ACCUM F28X50LP MIRROR 1 50 S (50 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2024GGI STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=8100 1 2092 S -MAMA G (2092 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2024GGI STIS/CCD ACCUM F28X50LP MIRROR 1 50 S (50 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2024GGI STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=8100 1 1951 S -MAMA G (1951 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 STIS/CCD ACCUM F28X50LP MIRROR none none none 1 1 N/A SN-2024GGI 1 STIS/CCD ACCUM F28X50LP MIRROR none none none 2 1 N/A SN-2024GGI 2 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 1 N/A -MAMA G SN-2024GGI 3 STIS/CCD ACCUM F28X50LP MIRROR none none none 1 2 N/A SN-2024GGI 3 STIS/CCD ACCUM F28X50LP MIRROR none none none 2 2 N/A SN-2024GGI 4 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 2 N/A -MAMA G 18109( 5) - 30-Jan-2026 16:34:07 - [ 6] Visit: 04 (2024ggi - Epoch 1 - NUV) Visit Requirements: 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 STIS/CCD ACCUM F28X50LP MIRROR 1 50 S (50 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2024GGI STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=1600 1 2092 S -MAMA G (2092 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2024GGI STIS/CCD ACCUM F28X50LP MIRROR 1 50 S (50 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN-2024GGI STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=1600 1 1931 S -MAMA G (1931 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 STIS/CCD ACCUM F28X50LP MIRROR none none none 1 1 N/A SN-2024GGI 1 STIS/CCD ACCUM F28X50LP MIRROR none none none 2 1 N/A SN-2024GGI 2 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 N/A -MAMA G SN-2024GGI 3 STIS/CCD ACCUM F28X50LP MIRROR none none none 1 2 N/A SN-2024GGI 3 STIS/CCD ACCUM F28X50LP MIRROR none none none 2 2 N/A SN-2024GGI 4 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 2 N/A -MAMA G 18109( 5) - 30-Jan-2026 16:34:07 - [ 7] Summary Form for Proposal 18109 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1200, BUFFER-TIME=1600, BUFFER-TIME=8000, BUFFER-TIME=8100 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN-2023IXF, SN-2024GGI, SN23IXF-OFFSET-LEGACY5313 ------------------------------------------------------------------------------------------------------------------------------------