17533( 10) - 08-Sep-2025 13:17:57 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17533 Version: 10 Check-in Time: 08-Sep-2025 13:17:57 STScI Edit Number: 6 Title Identifying a New Source of r-Process Nucleosynthesis with HST ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Jillian Rastinejad University of Maryland Y CoI: Dr. Wen-fai Fong Northwestern University N CoI: Prof. Andrew James Levan Radboud University Nijmegen N CoI: Prof. Nial Rahil Tanvir University of Leicester N CoI: Dr. Peter Blanchard Harvard University N CoI: Prof. Ashley Villar Harvard University N ------------------------------------------------------------------------------------ Abstract The origin of the Universe's heavy r-process elements is a fundamental issue which affects chemical enrichment across cosmic time and the development of complex life. It is now confirmed that neutron star mergers are responsible for at least some of the r-process budget, but there is gaining observational and theoretical support for an additional and faster production channel: the core-collapse of rapidly-rotating, massive stars. In particular, energetic supernovae with associated long-duration gamma-ray bursts (GRB-SNe) are the strongest candidates for a fast channel. Here, their massive neutronized accretion disks mix with the outer, Ni-dominated ejecta producing dramatic reddening at late times (~50-200 days). Even for the most nearby events, HST is necessary to detect the SN at these epochs when the color of an r-process enriched SN will be distinguishable from an event with no r-process, especially against the background light of a star-forming host galaxy. Yet, as these GRB-SNe r-process models gain traction, no tailored observations with the relevant sensitivity or wavelength coverage exist. We propose a first-of-its-kind study to monitor the late-time evolution of one nearby (z<0.3) GRB-SN as a crucial test of current models. We will obtain 12 HST orbits over 5 epochs in F606W and F160W. The detection of r-process nucleosynthesis in a GRB-SN would be transformative for our understanding of when and where heavy elements enter galaxies like our Milky Way. Given both the long time baseline and rarity of neary LGRBs, we request long-term and carry-over status. ------------------------------------------------------------------------------------ Observations Description ------------------------ This is a non-disruptive target-of-opportunity proposal with long-term and carry-over status. This proposal is for 12 orbits (8 orbits awarded in Cycle 31, 4 in Cycle 32) of HST imaging of a nearby GRB supernova (SN), a promising but untested site to observe the formation of elements via rapid neutron capture (r-process) nucleosynthesis. These observations will observe the SN's color evolution by observing contemporaneously in one optical (F606W) filter and one near-IR (F160W) filter over ~50 - 600 days following the GRB, when ground-based telescopes are no longer sensitive to the SN's expected brightness. Observations will be obtained across 5 visits, with the first 4 visits consisting of one orbit each of WFC3/UVIS F606W and WFC3/IR F160W 17533( 10) - 08-Sep-2025 13:17:57 - [ 2] imaging. The final visit will be 2 orbits in each filter in order to provide a deep template for image subtraction with earlier epochs, intended to remove host galaxy light contamination. ------------------------------------------------------------------------------------ 17533( 10) - 08-Sep-2025 13:17:57 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 3 250108A STAR, GAMMA RAY RA=03H42M28.3900S, J2000 V = 27 +/- 0.5 BURSTER, SUPERNOVA DEC=-22D30'21.20" Reference Frame: ICRS Comments: Expected magnitude based on supernova modeling. We have not been able to get ground-based imaging since March due to Sun constraint. ------------------------------------------------------------------------------------------------------------------------------------ 17533( 10) - 08-Sep-2025 13:17:57 - [ 4] TARGET LIST Generic Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria | Flux data No | Name | Description | | ------------------------------------------------------------------------------------------------------------------------------------ 1 LGRB1 EXT-STAR, GAMMA RAY A GRB SN AT APPROXIMATELY Z < 0.3 V = 26 +/- 2 BURSTER, SUPERNOVA ------------------------------------------------------------------------------------------------------------------------------------ 17533( 10) - 08-Sep-2025 13:17:57 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 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 ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17533( 10) - 08-Sep-2025 13:17:57 - [ 6] Visit: 05 (F606W visit 05) Visit Requirements: BETWEEN 01-NOV-2025:00:00:00 AND 25-NOV-2025:00:00:00; TOO RESPONSE TIME 15.0D 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 250108A WFC3/UVI ACCUM UVIS-CENT F606W 2 540 S POS TARG -65, -65; GS S ER (4320 S) ACQ SCENARIO ONEB1O3; PATTERN 3 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none 1 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none 2 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none 1 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none 2 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 3 none 1 none 2 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 3 none 2 none 2 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 4 none 1 none 2 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 4 none 2 none 2 N/A S TER 17533( 10) - 08-Sep-2025 13:17:57 - [ 7] Visit: 06 (F160W visit 06) Visit Requirements: AFTER 05 BY 0 D TO 3 D; TOO RESPONSE TIME 15.0D 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 250108A WFC3/IR MULTIAC IR-FIX F160W NSAMP=12, SAMP-SEQ=SPARS50 2 DEF POS TARG 40, 35; PATTERN CUM (4423.498 1 1 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 | ------------------------------------------------------------------------------------------------------------------------------------ 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 1 none 1 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 1 none 2 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 2 none 1 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 2 none 2 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 3 none 1 none 2 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 3 none 2 none 2 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 4 none 1 none 2 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 4 none 2 none 2 N/A CUM 17533( 10) - 08-Sep-2025 13:17:57 - [ 8] Visit: 07 (F606W visit 07) Visit Requirements: BETWEEN 01-APR-2026:00:00:00 AND 31-AUG-2026:00:00:00; TOO RESPONSE TIME 15.0D On Hold Comments: Additional Comments: Deep template observations for image subtraction 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 250108A WFC3/UVI ACCUM UVIS-CENT F606W 2 540 S POS TARG -65, -65; S ER (4320 S) PATTERN 3 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none 1 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none 2 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none 1 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none 2 none 1 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 3 none 1 none 2 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 3 none 2 none 2 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 4 none 1 none 2 N/A S TER 250108A 1 WFC3/UVI ACCUM UVIS-CEN F606W 4 none 2 none 2 N/A S TER 17533( 10) - 08-Sep-2025 13:17:57 - [ 9] Visit: 08 (F160W visit 08) Visit Requirements: AFTER 07 BY 0 D TO 31 D; TOO RESPONSE TIME 15.0D 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 250108A WFC3/IR MULTIAC IR-FIX F160W NSAMP=12, SAMP-SEQ=SPARS50 2 DEF POS TARG 40, 35; GS ACQ CUM (4423.498 SCENARIO ONEB1O3; S) PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 1 none 1 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 1 none 2 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 2 none 1 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 2 none 2 none 1 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 3 none 1 none 2 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 3 none 2 none 2 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 4 none 1 none 2 N/A CUM 250108A 1 WFC3/IR MULTIAC IR-FIX F160W 4 none 2 none 2 N/A CUM 17533( 10) - 08-Sep-2025 13:17:57 - [ 10] Summary Form for Proposal 17533 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR-FIX, UVIS-CENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=12, SAMP-SEQ=SPARS50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 05 BY 0 D TO 3 D, AFTER 07 BY 0 D TO 31 D, BETWEEN 01-APR-2026:00:00:00 AND 31-AUG-2026:00:00:00, BETWEEN 01-NOV-2025:00:00:00 AND 25-NOV-2025:00:00:00, GS ACQ SCENARIO ONEB1O3, PATTERN 1 1, PATTERN 3 1, POS TARG -65, -65, POS TARG 40, 35, TOO RESPONSE TIME 15.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160W, F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 250108A ------------------------------------------------------------------------------------------------------------------------------------