0 Assigned ID: 557 ----- Attempting Submission 1 (Fri Apr 05 17:21:24 GMT 2019) ----- 0 ----- Attempting Submission 1 (Thu Jul 25 05:20:40 GMT 2019) ----- HST Phase II Proposal 15817 (corelike_cycle27_phaseii.apt) successfully submitted. Receipt: # 15817-1 ----- Attempting Submission 2 (Thu Jul 25 05:30:05 GMT 2019) ----- HST Phase II Proposal 15817 (corelike_cycle27_phaseii.apt) successfully submitted. Receipt: # 15817-2 ----- Attempting Submission 3 (Thu Jul 25 05:34:58 GMT 2019) ----- HST Phase II Proposal 15817 (corelike_cycle27_phaseii.apt) successfully submitted. Receipt: # 15817-3 ----- Attempting Submission 4 (Mon Oct 28 15:41:39 GMT 2019) ----- HST Phase II Proposal 15817 (corelike_cycle27_phaseii.apt) successfully submitted. Receipt: # 15817-4 ----- Attempting Submission 5 (Mon Oct 28 16:16:30 GMT 2019) ----- 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. 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 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. 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 4 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. 2019 submitted), and the other two are in preparation to be submitted in 2019 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. 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. Planets and Planet Formation Solar System 6 false false true false false false false SUPPORTED STAR DA NO J2000 J2000 mFUV=14.65+/-0.01, mNUV=14.77+/-0.01 STAR DA NO J2000 J2000 mNUV=15.6 (from MSX) COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G130M 1291 1564032774900 /Users/cmelis/observing/hst/cycle27/phaseii/OP-cache/corelike_cycle27_phaseii-v01.xml The scheduling data was generated by CASM 27.2. CASM was run in Phase II mode. 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