17828( 2) - 08-Aug-2024 12:25:08 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17828 Version: 2 Check-in Time: 08-Aug-2024 12:25:08 STScI Edit Number: 0 Title An HST probe of JWST white dwarf debris disk mineralogies: energetic impacts or extrasolar crusts? ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Carl Melis University of California - San Diego Y CoI: Prof. Jay Farihi University College London N CoI: Dr. Kate Y.L Su Space Science Institute N CoI: Dr. Patrick Dufour Universite de Montreal N CoI: Dr. Seth Redfield Wesleyan University N ------------------------------------------------------------------------------------ Abstract Recent JWST MIRI spectroscopic observations covering 5-12 microns unveil a dramatic excess of dusty debris over the well-characterized photosphere of three polluted white dwarf stars. The JWST spectra reveal solid-state emission features that require glassy silica (SiO2) species associated with energetic impacts or differentiation processes that produced Earth-like crustal material. Ultraviolet spectroscopic observations will provide measurements and constraints on the elemental constituents of the debris, including those that dominate terrestrial rocks (Si, Mg, Fe), as well as other important tracers of planetary assembly and structure. The proposed experiment will distinguish between Fe-poor material in a planetary crust, where the high silica content has resulted from (past) differentiation, and silica resulting from highly energetic impacts between primitive material that may have occurred during the post-main sequence phase. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our primary goal is to detect Fe, Mg, and Si in two white dwarf stars, GaiaJ0547-4847 and WDJ0802+5631. This goal will require ultraviolet spectroscopy of each white dwarf using their own specific instrumental setup. GaiaJ0547-4847 will be observed with STIS/G230L as low resolution coverage over the 1800-3000 Ang range is sufficient to probe all desired elements (and will additionally yield detection of or a stringent limit on C). We use the GALEX-measured NUV magnitude of 17.08 to estimate how much time on source is necessary to obtain our desired signal-to-noise assuming a small amount of interstellar reddening (consistent with the location of the star in the Galaxy). Focusing on the spectral region around C, we find that with 4, 700 seconds of integration time we can obtain signal-to-noise ~35 per resolution element near 1960 Ang which should lead to signal-to-noise per resolution element of ~60 for spectral regions around Mg, Fe, and Si. The requested signal-to-noise values will allow us to robustly distinguish between a giant impact between primitive rocky bodies and a planetary crust interpretation for the material orbiting and polluting GaiaJ0547-4847. WDJ0802+5631 will be observed with STIS/E230M to assess narrow absorption lines 17828( 2) - 08-Aug-2024 12:25:08 - [ 2] of Fe, Mg, and Si in the atmosphere of this DA white dwarf. There is no UV flux measurement available for WDJ0802+5631 so we estimate its expected flux level based off of spectral energy distribution fitting to optical and infrared data combined with an accurate atmospheric model that fits them. To distinguish between the two competing models (crustal material or a giant impact) we need to obtain signal-to-noise >~5 per resolution element in the 2500-2800 Ang region. With 25, 000 seconds on source we find that we can obtain signal-to-noise between 6-10 in the desired region and thus will be able to achieve our science goals. All exposure time estimates are made using the STIS ETC assuming standard background parameters and with a white dwarf spectral energy distribution matched to the parameters and flux level of our targets. Our requested time estimates for STIS are increased assuming 21 minutes of overhead (including all spacecraft, acquisition, and exposure overheads as suggested in the STIS manual) per visit and 6.5 minutes of observatory overhead per additional orbit (spacecraft acquisition). We split visits for WDJ0802+5631 into groups of 3 or 4 orbits to aid in scheduling and maintain the health of the MAMA detector. In sum, we request 2 orbits total for STIS observations of GaiaJ0547-4847 and 10 orbits total for WDJ0802+5631. Observations will be done in the TIME-TAG mode and use the STIS CCD for acquisition. We opt for the 50CCD acquisition filter for our generally bluer target stars. The target white dwarf stars are ICRS objects (Gaia DR3 position with less than 0.1" positional uncertainty), are the brightest sources within a 7" radius (and thus should dominate the 5"x5" acqusition field-of-view regardless of where they land in it), have an estmated or measured UV flux, and are safe for STIS detectors in our desired setups. ------------------------------------------------------------------------------------ 17828( 2) - 08-Aug-2024 12:25:08 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 UCAC4-207-00 STAR, DZ RA=05H47M25.6166S +/- 0.00003", J2000 V = 15.8 mNUV=17.08 6574 DEC=-48D47'20.83" +/- 0.00003" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016 -0.008671907930711063 0.09162300000000001 0.0215077 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAIA-DR2-108 STAR, DA RA=08H02M27.6740S +/- 0.00003", J2000 V = 16.04 150448346771 DEC=+56D31'55.24" +/- 0.00003" 4176 Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016 -0.004409297978847065 -0.013368 0.0159494 ------------------------------------------------------------------------------------------------------------------------------------ 17828( 2) - 08-Aug-2024 12:25:08 - [ 4] Visit: 01 (GaiaJ0547STIS) 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 UCAC4-207-0 STIS/CCD ACQ 50CCD MIRROR 1 5 S (5 S) 06574 ------------------------------------------------------------------------------------------------------------------------------------ 2 UCAC4-207-0 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=700 1 2058 S 06574 -MAMA G (2058 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 UCAC4-207-0 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=700 1 2654 S 06574 -MAMA G (2654 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 | ------------------------------------------------------------------------------------------------------------------------------------ UCAC4-207-006574 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A UCAC4-207-006574 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G UCAC4-207-006574 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G 17828( 2) - 08-Aug-2024 12:25:08 - [ 5] Visit: 02 (WDJ0802STIS1) 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 GAIA-DR2-10 STIS/CCD ACQ 50CCD MIRROR 1 7 S (7 S) 81504483467 714176 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2163 S 81504483467 -MAMA G (2163 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2689 S 81504483467 -MAMA G (2689 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 4 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2689 S 81504483467 -MAMA G (2689 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GAIA-DR2-1081504483 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A 467714176 GAIA-DR2-1081504483 2 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 1 N/A 467714176 -MAMA G GAIA-DR2-1081504483 3 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 2 N/A 467714176 -MAMA G GAIA-DR2-1081504483 4 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 3 N/A 467714176 -MAMA G 17828( 2) - 08-Aug-2024 12:25:08 - [ 6] Visit: 03 (WDJ0802STIS2) 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 GAIA-DR2-10 STIS/CCD ACQ 50CCD MIRROR 1 7 S (7 S) 81504483467 714176 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2163 S 81504483467 -MAMA G (2163 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2689 S 81504483467 -MAMA G (2689 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 4 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2689 S 81504483467 -MAMA G (2689 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GAIA-DR2-1081504483 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A 467714176 GAIA-DR2-1081504483 2 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 1 N/A 467714176 -MAMA G GAIA-DR2-1081504483 3 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 2 N/A 467714176 -MAMA G GAIA-DR2-1081504483 4 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 3 N/A 467714176 -MAMA G 17828( 2) - 08-Aug-2024 12:25:08 - [ 7] Visit: 04 (WDJ0802STIS3) 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 GAIA-DR2-10 STIS/CCD ACQ 50CCD MIRROR 1 7 S (7 S) 81504483467 714176 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2163 S 81504483467 -MAMA G (2163 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2689 S 81504483467 -MAMA G (2689 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 4 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2689 S 81504483467 -MAMA G (2689 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 5 GAIA-DR2-10 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 BUFFER-TIME=950 1 2689 S 81504483467 -MAMA G (2689 S) 714176 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GAIA-DR2-1081504483 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A 467714176 GAIA-DR2-1081504483 2 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 1 N/A 467714176 -MAMA G GAIA-DR2-1081504483 3 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 2 N/A 467714176 -MAMA G GAIA-DR2-1081504483 4 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 3 N/A 467714176 -MAMA G GAIA-DR2-1081504483 5 STIS/NUV TIME-TA 0.2X0.2 E230M 2561 none none none none 4 N/A 467714176 -MAMA G 17828( 2) - 08-Aug-2024 12:25:08 - [ 8] Summary Form for Proposal 17828 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.2, 50CCD, 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=700, BUFFER-TIME=950 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E230M, G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAIA-DR2-1081504483467714176, UCAC4-207-006574 ------------------------------------------------------------------------------------------------------------------------------------