15817( 5) - 28-Oct-2019 16:39:46 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15817 Version: 5 Check-in Time: 28-Oct-2019 16:39:46 STScI Edit Number: 2 Title The chemical diversity of planetary cores ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Carl Melis University of California - San Diego Y CoI: Dr. Patrick Dufour Universite de Montreal N CoI: Dr. Beth Klein University of California - Los Angeles N CoI: Prof. Ben M. Zuckerman University of California - Los Angeles N CoI: Dr. Siyi Xu Gemini Observatory, Northern Operations N CoI: Dr. Alycia J. Weinberger Carnegie Institution of Washington N ------------------------------------------------------------------------------------ Abstract White dwarf stars are now known to regularly accrete material from their extant planetary systems. We have identified two new polluted white dwarf star that are accreting extremely iron-rich material, suggesting that they are being polluted by the core of a massive, differentiated rocky body. We propose COS FUV spectroscopic observations of these two stars that will allow us to peer into the heart of Earth-like rocky exoplanets and explore the range of elemental compositions they may have. These observations will address questions pertaining to terrestrial planet structure and formation processes and the question of what mixture of elements is responsible for Earth's under-dense outer core. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our primary goal is to confirm the Fe-rich nature of GaiaJ0707-7438 and GaiaJ0649-7624 and simultaneously ensure that the Fe originates from an O-poor core-like environment. Our secondary goal is then to characterize additional elements. Modeling of absorption lines shows that the desired elements can be measured or sufficiently strongly constrained with observations in the 1130-1433 Angstrom range. We will perform medium spectral resolution ultraviolet spectroscopy with COS and the G130M grating to cover the 1130-1433 Angstrom range. In accordance with the COS2025 policies, we will only use two FP-POS positions (3 and 4). For the UV flux levels of each white dwarf star (given in their target information areas) it should be possible to obtain average S/N~30 in the 1130-1433 Angstrom wavelength range with total on-source exposure time of approximately 2, 500 seconds. These estimates are made using the COS ETC assuming standard background parameters and with a white dwarf spectral energy distribution matched to the parameters and flux level of our target. A signal-to-noise ratio of ~30 for the 1130-1433 Angstrom wavelength range will enable detection or tight limits on the abundances of oxygen and iron. Such a signal-to-noise ratio will also enable the detection or constraint of other elements (e.g., carbon, aluminum, phosphorus, sulfur, chromium, manganese, or nickel). Our requested time estimates for COS are increased assuming 20 minutes 15817( 5) - 28-Oct-2019 16:39:46 - [ 2] of instrument overhead (including all acquisition and exposure overheads as suggested in the COS manual) per visit and 6 minutes of observatory overhead per orbit (spacecraft acquisition). In sum, we request 1 orbit for each white dwarf (separate visits) and a total of 2 orbits for this project. Observations will be done in the TIME-TAG mode using TAG-FLASH wavelength calibration. Each white dwarf is an ICRS object (Gaia DR2 position with less than 0.4" positional uncertainty), has a measured UV flux, and is safe for the COS detectors in our desired setups. ------------------------------------------------------------------------------------ 15817( 5) - 28-Oct-2019 16:39:46 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAIAJ0707-74 STAR, DA RA=07H07M54.8448S +/- 0.0380", J2000 V = 14.95 +/- 0.06 mFUV=14.65+/-0.01, 38 DEC=-74D38'27.91" +/- 0.0377" mNUV=14.77+/-0.01 Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 -0.01713478565136224 -0.024394 0.017 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAIAJ0649-76 STAR, DA RA=06H49M34.8524S +/- 0.0427", J2000 V = 16.46 +/- 0.08 mNUV=15.6 (from MSX) 24 DEC=-76D24'58.11" +/- 0.0514" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 -0.013642824378669155 0.123158 0.007 ------------------------------------------------------------------------------------------------------------------------------------ 15817( 5) - 28-Oct-2019 16:39:46 - [ 4] Visit: 01 (GaiaJ0707-7438) 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 GAIAJ0707-7 COS/NUV ACQ/IMA BOA MIRRORA 1 42 S (42 438 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 GAIAJ0707-7 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=720, FP-POS=3, 1 1280 S 438 G FLASH=YES (1280 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 GAIAJ0707-7 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=720, FP-POS=4, 1 1288 S 438 G FLASH=YES (1288 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 | ------------------------------------------------------------------------------------------------------------------------------------ GAIAJ0707-7438 1 COS/NUV ACQ/IMA BOA MIRRORA none none none none 1 N/A GE GAIAJ0707-7438 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G GAIAJ0707-7438 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G 15817( 5) - 28-Oct-2019 16:39:46 - [ 5] Visit: 02 (GaiaJ0649-7624) 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 GAIAJ0649-7 COS/NUV ACQ/IMA PSA MIRRORB 1 10 S (10 624 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 GAIAJ0649-7 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=850, FP-POS=3, 1 1320 S 624 G FLASH=YES (1320 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 GAIAJ0649-7 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=850, FP-POS=4, 1 1331 S 624 G FLASH=YES (1331 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 | ------------------------------------------------------------------------------------------------------------------------------------ GAIAJ0649-7624 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE GAIAJ0649-7624 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G GAIAJ0649-7624 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G 15817( 5) - 28-Oct-2019 16:39:46 - [ 6] Summary Form for Proposal 15817 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures BOA, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=720, BUFFER-TIME=850, FLASH=YES, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORA, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAIAJ0649-7624, GAIAJ0707-7438 ------------------------------------------------------------------------------------------------------------------------------------