0 Assigned ID: 700 ----- Attempting Submission 1 (Fri Mar 06 19:32:33 GMT 2020) ----- HST Phase I Proposal 700 successfully submitted. Receipt: # 700-1 ----- Attempting Submission 2 (Fri Mar 06 23:21:31 GMT 2020) ----- HST Phase I Proposal 700 successfully submitted. Receipt: # 700-2 0 ----- Attempting Submission 1 (Thu Jun 18 20:25:58 GMT 2020) ----- The biological potential of other worlds: comparing the phosphorus content of wet and dry exoplanetary crusts Life on Earth as we know it requires water and reliable access to phosphorus to drive basic biological processes. Studies of polluted white dwarf stars are able to detect both water and phosphorus in the accreted material from their extant planetary systems. In this proposal we seek to carefully examine the phosphorus content of a set of polluted white dwarf stars that are accreting the crust and mantle regions (the surface) of massive, differentiated rocky bodies. COS FUV spectroscopic observations of three white dwarf stars -- one water-rich and two relatively water-poor -- along with available data for another water-rich white dwarf will allow us to robustly assess their phosphorus content and compare the biological potential of very wet and more Earth-like worlds. Our primary goal is to detect or tightly constrain phosphorus for three polluted white dwarf stars: GD 61, SDSSJ0731+2417, and SDSSJ1043+0855. A secondary goal is to measure carbon to a sufficient level in SDSSJ0731+2417 as it cannot be characterized from optical data. Modeling of absorption lines shows that phosphorus has its strongest transitions for the target stars near 1540 Angstroms. Carbon 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 G160M grating to cover the 1410-1800 Angstrom range for all three targets to measure phosphorus and with the G130M grating to cover the 1130-1433 Angstrom range to measure carbon in SDSSJ0731+2417. For the measured UV flux of each target (given in their information areas) and based on past COS observations of GD 61 and SDSSJ1043+0855 we expect to obtain near the 1540 Angstrom phosphorus transition S/N~15 for SDSSJ1043+0855 (2 orbits), S/N~22 for SDSSJ0731+2417 (2 orbits), and S/N~22 for GD 61 (1 orbit). Near the 1330 carbon transition for SDSSJ0731+2417 we expect to obtain S/N~15 (1 orbit). 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 targets. These signal-to-noise ratios will enable detection or tight limits on the abundances of phosphorus for all targets and additionally carbon for SDSSJ0731+2417. 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 a total of 6 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. Reduced-gyro impact: we do not forsee any significant impact on this program due to reduced-gyro operations. Each visit has a wide range of observing windows, loss of ~50% of these would still leave ample opportunity to obtain each target. There are no orientation restrictions for this program nor does it use spatial scanning. The proposal team has extensive experience with obtaining, reducing, and analyzing COS data. We have been working closely as a team to produce such results since 2011 and are world experts in investigating the mineralogy of white dwarf atmospheric pollutants (the main scientific goal of the proposed project). Dr. Carl Melis has led 6 separate COS polluted white dwarf projects, one of which has been published (Melis & Dufour 2017, ApJ 834, 1), another is soon to be published (Todd et al. 2020 submitted), and the others are in preparation to be submitted in 2020 as of the writing of this statement. Drs. Zuckerman, Xu, and Klein (with now-deceased Prof. Mike Jura) have been obtaining COS spectra of polluted white dwarfs for several years and have produced a similar number of publications (Jura et al. 2012, ApJ 750, 69; Xu et al. 2013, ApJL 766, 18; Xu et al. 2013, ApJ 766, 132; Xu et al. 2014, ApJ 783, 79; Xu et al. 2017, ApJL 836, 7). Dr. Weinberger is an expert in exoplanetary systems and spectroscopy. Ms. Schneider is a graduate student at UCLA specializing in geophysics. Prof. Dufour has substantial experience in modeling white dwarf spectra, especially to get atmospheric parameters and abundances, and has also led his own COS projects that have resulted in publications (e.g., Dufour et al. 2011, ApJL 733, 19). All members of the proposal team are devoting significant fractions of their time to studying polluted white dwarf stars. They will continue to do so with this project if time is awarded. Drs. Melis, Klein, Xu, and Weinberger will contribute to data reduction and analysis. Prof. Dufour will be responsible for modeling spectra and measuring abundances. All will contribute to interpretation and publication. Exoplanets and Exoplanet Formation Stellar Physics and Stellar Types 6 false false true false false false false SUPPORTED STAR DB NO J2000 J2000 mNUV=14.70+/-0.05 STAR DA NO J2000 J2000 mFUV=16.02+/-0.05 STAR DA NO J2000 J2000 mFUV=16.92+/-0.05 The scheduling data was generated by CASM 28.0. CASM was run in Phase I mode. COS/FUV Spectroscopic No No G160M 1600 The scheduling data was generated by CASM 28.0. CASM was run in Phase I mode. COS/FUV Spectroscopic No No G160M 1600 The scheduling data was generated by CASM 28.0. CASM was run in Phase I mode. COS/FUV Spectroscopic No No G130M 1291 The scheduling data was generated by CASM 28.0. CASM was run in Phase I mode. COS/FUV Spectroscopic No No G160M 1600 /Users/cmelis/observing/hst/cycle28/phoscrust/phaseii/OP-cache/phoscrust_cycle28_phaseii-v01.xml The scheduling data was generated by CASM 28.2. 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