15080( 3) - 09-Aug-2018 18:55:29 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15080 Version: 3 Check-in Time: 09-Aug-2018 18:55:29 STScI Edit Number: 1 Title Is SDSSJ195750.83+340404.4 accreting a planetary core? ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Carl Melis University of California - San Diego Y CoI: Dr. Patrick Dufour Universite de Montreal N ------------------------------------------------------------------------------------ Abstract White dwarf stars are now known to regularly accrete material from their extant planetary systems. We have identified a new polluted white dwarf star that is accreting extremely iron-rich material, suggesting that it is being polluted by the core of a massive, differentiated rocky body. We propose COS FUV spectroscopic observations of SDSSJ1957+3404 that will allow us to peer into the heart of Earth-like rocky exoplanets. 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 SDSSJ1957+3404 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 GALEX-measured NUV flux of SDSS J1957+3404 (NUV AB magnitude of 16.66+/-0.03) and FUV-NUV colors for comparable temperature white dwarf stars we estimate the FUV AB magnitude to be 16.5 (GALEX observations of SDSS J1957+3404 were performed after the failure of the FUV channel, hence why only an NUV measurement is available). With such a magnitude, it should be possible to obtain average S/N~15 in the 1130-1433 Angstrom wavelength range with total on-source exposure time of approximately 4, 000 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 ~15 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 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 15080( 3) - 09-Aug-2018 18:55:29 - [ 2] 2 orbits total for COS observations of SDSS J1957+3404. Observations will be done in the TIME-TAG mode using TAG-FLASH wavelength calibration. SDSSJ1957+3404 is an ICRS object (SDSS position with less than 0.4" positional uncertainty), has a measured GALEX UV flux, and is safe for the COS detectors in our desired setups. ------------------------------------------------------------------------------------ 15080( 3) - 09-Aug-2018 18:55:29 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSSJ1957+34 STAR, DA RA=19H57M50.8313S +/- 0.066", J2000 V = 16.58 +/- 0.02 GALEX NUV = 16.66 04 DEC=+34D04'4.41" +/- 0.059" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2006.4019 -0.0012876625431878482 -0.013 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 15080( 3) - 09-Aug-2018 18:55:29 - [ 4] Visit: 01 (SDSSJ1957FUV) Visit Requirements: On Hold Comments: Additional Comments: COS/FUV observations of SDSSJ1957+3404. 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 SDSSJ1957+3 COS/NUV ACQ/IMA PSA MIRRORB 1 30 S (30 404 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSSJ1957+3 COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=2495, 1 2537 S 404 G FLASH=YES (2537 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSSJ1957+3 COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=2495, 1 2954 S 404 G FLASH=YES (2954 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSSJ1957+3404 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE SDSSJ1957+3404 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G SDSSJ1957+3404 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G 15080( 3) - 09-Aug-2018 18:55:29 - [ 5] Visit: Z1 (SDSSJ1957FUV) Visit Requirements: On Hold Comments: Additional Comments: THis is a HOPR repeat of failed visit 01 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 SDSSJ1957+3 COS/NUV ACQ/IMA PSA MIRRORB 1 30 S (30 404 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSSJ1957+3 COS/FUV TIME-TA PSA G130M 1291 FP-POS=3, BUFFER-TIME=2495, 1 2537 S 404 G FLASH=YES (2537 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSSJ1957+3 COS/FUV TIME-TA PSA G130M 1291 FP-POS=4, BUFFER-TIME=2495, 1 2954 S 404 G FLASH=YES (2954 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSSJ1957+3404 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE SDSSJ1957+3404 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G SDSSJ1957+3404 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G 15080( 3) - 09-Aug-2018 18:55:29 - [ 6] Summary Form for Proposal 15080 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=2495, FLASH=YES, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names SDSSJ1957+3404 ------------------------------------------------------------------------------------------------------------------------------------