17819( 4) - 12-Sep-2025 20:11:16 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17819 Version: 4 Check-in Time: 12-Sep-2025 20:11:16 STScI Edit Number: 0 Title WD0106-038: the first variable metal polluted white dwarf? ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Laura Rogers NOIRLab - (AZ) Y CoI: Dr. Amy Bonsor University of Cambridge N CoI: Dr. Siyi Xu NOIRLab - Gemini North (HI) N CoI: Dr. John Henry Debes Space Telescope Science Institute - ESA - N JWST CoI: Dr. Michael Shara American Museum of Natural History N CoI: Dr. Simon Hodgkin University of Cambridge N CoI: Ms. Mariona Badenas Agusti Massachusetts Institute of Technology N CoI: Dr. Patrick Dufour Universite de Montreal N ------------------------------------------------------------------------------------ Abstract This proposal aims to re-observe a white dwarf polluted with planetary material to confirm whether the amount of planetary material in the atmosphere has changed over time. This would be the first confirmed variable metal polluted white dwarf. Ground based observations revealed an increase of 35% in the equivalent width of the Mg II doublet over a timescale of 10 years. However, this is based off of one spectral line. A previous UV spectrum of WD0106-038 has been obtained which revealed a plethora of absorption lines; by obtaining a follow up UV spectrum we will confirm whether this is the first variable metal polluted white dwarf. Due to the short sinking timescales of approximately days-weeks depending on the element, we propose 2 observations to assess both the long-term (yearly) and short-term (monthly) variability of the absorption lines. This would be the first evidence for sporadic accretion and will have a significant impact on how we use metal polluted white dwarfs to measure bulk planetary compositions. ------------------------------------------------------------------------------------ Observations Description ------------------------ Technical Set-up: We propose to use the G130M grating in the FUV module with a central wavelength of 1291 A. In accordance with the COS2025 policies, we will only use two FP-POS positions (3 and 4). COS safety: Our target is sufficiently faint that COS safety is not a problem. Reduced gyro observations: our observations are not time critical, we just require the 2 visits to be separated by more than 60 days, so reducing the possible observing windows will not affect this proposal. Using the visit planner tool, there are plenty of schedulable opportunities across the cycle for the target. Target acquisition is required in order to sucessfully complete the proposed observations. Scheduling: This proposal observes the same object to search for variability, 17819( 4) - 12-Sep-2025 20:11:16 - [ 2] therefore the gap between observations needs to be at leat 2 months. SNR: We require a SNR of at least 30 around 1320A, close to important lines of carbon. ------------------------------------------------------------------------------------ 17819( 4) - 12-Sep-2025 20:11:16 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 TON-S-193 STAR, DA, DZ RA=01H08M36.0346S +/- 0.0291", J2000 V = 15.26 FUV=15.22 DEC=-32D37'43.38" +/- 0.0182" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0021025535912669903 -0.021664000000000003 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 17819( 4) - 12-Sep-2025 20:11:16 - [ 4] Visit: 01 (WD0106-038-Obs1) Visit Requirements: On Hold Comments: Additional Comments: First visit for WD0106-038 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 TON-S-193 COS/NUV ACQ/IMA PSA MIRRORB 1 10 S (10 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 TON-S-193 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=1511, FP-POS=3 1 2056 S G (2056 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 TON-S-193 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=1511, FP-POS=4 1 2055 S G (2055 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 | ------------------------------------------------------------------------------------------------------------------------------------ TON-S-193 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE TON-S-193 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G TON-S-193 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G 17819( 4) - 12-Sep-2025 20:11:16 - [ 5] Visit: 02 (WD0106-038-Obs2) Visit Requirements: AFTER 03 BY 60 D TO 1000 D On Hold Comments: Additional Comments: Second visit for WD0106-038, needs to be > 60 days after the first visit. 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 TON-S-193 COS/NUV ACQ/IMA PSA MIRRORB 1 10 S (10 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 TON-S-193 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=1511, FP-POS=3 1 2056 S G (2056 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 TON-S-193 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=1511, FP-POS=4 1 2055 S G (2055 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 | ------------------------------------------------------------------------------------------------------------------------------------ TON-S-193 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE TON-S-193 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G TON-S-193 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G 17819( 4) - 12-Sep-2025 20:11:16 - [ 6] Visit: 03 (WD0106-038-Obs1) Visit Requirements: On Hold Comments: Additional Comments: First visit for WD0106-038 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 TON-S-193 COS/NUV ACQ/IMA PSA MIRRORB 1 10 S (10 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 TON-S-193 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=1511, FP-POS=3 1 2056 S G (2056 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 TON-S-193 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=1511, FP-POS=4 1 2055 S G (2055 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 | ------------------------------------------------------------------------------------------------------------------------------------ TON-S-193 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE TON-S-193 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G TON-S-193 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G 17819( 4) - 12-Sep-2025 20:11:16 - [ 7] Summary Form for Proposal 17819 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1511, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 03 BY 60 D TO 1000 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names TON-S-193 ------------------------------------------------------------------------------------------------------------------------------------