The composition of exoplanetary bodies - as probed in accreting white dwarfs with gaseous emission

0 Assigned ID: 1703 ----- Attempting Submission 1 (Thu Apr 08 20:40:11 GMT 2021) ----- 0 ----- Attempting Submission 1 (Wed Jul 28 14:46:13 GMT 2021) ----- ----- Attempting Submission 2 (Mon Aug 02 16:31:10 GMT 2021) ----- The composition of exoplanetary bodies - as probed in accreting white dwarfs with gaseous emission As we move into an epoch of rocky planet detection, white dwarfs that have accreted exoplanetary bodies are unique laboratories to directly study the bulk composition of exoplanetary material and deduce the geological processes in exoplanets. Gas and dust observed close to the white dwarfs trace the accretion of this planetary material into the atmosphere of the white dwarf. The recent three-fold increase in the number of known white dwarfs with gaseous emission (including emission features from O, Na, Mg, Si, Ca, Fe) provides a unique opportunity to study the composition of planetary material in two ways. Abundances can be derived from the gas exterior to the white dwarf, and they can then be compared to the abundances determined from the accreted material in the photosphere of the white dwarf. We propose to obtain abundances of the accreted exoplanetary material from FUV spectra of four recently discovered, heavily polluted white dwarfs with at least O, Ca, and Fe in circumstellar gaseous emission. By comparing the composition of the circumstellar gas with the composition of the material that has accreted onto the atmosphere of the white dwarf, we can probe whether volatiles are accreted simultaneously with refractories. This is crucial to using the observed abundances in the white dwarf photosphere to probe the volatile content of exoplanetary bodies, and to understand how planetary bodies lose (gain) volatiles. We propose to obtain HST/COS spectra of 4 recently identified heavily polluted white dwarfs with both circumstellar gas and dust to obtain photospheric abundances of: O, Fe, and C, so we can compare the composition of the circumstellar gas and the accreted material in the atmosphere of the white dwarfs. Technical Set-up: We propose to use the G130M grating in the FUV module with a central wavelength of 1291 A to parallel the analysis by Jura et al. (2012) and Gaensicke et al. (2012). In accordance with the COS2025 policies, we will only use two FP-POS positions (3 and 4). CVZ: One of our targets is located in the continuous viewing zone, but we do not require continuous uninterrupted observations. Using the visit planner tool, we find our target is schedulable. Exposure Times: We scaled the Mg/H abundance determined from ground based optical observations to calculate model spectra for each white dwarf. This gives us expected abundances and line strengths for C, N, O, Si, S, Fe in the UV. For all 4 targets we will confidently detect C, O, and Fe using HST/COS. For each object, we input the model spectra into the COS ETC version 29.1.1 to determine the required on-target observing time. We aim to achieve a signal-to-noise ratio of 20 at 1320 A, close to the wavelengths of the important C II lines. We use average sky background conditions, and include the overheads for target acquisition and instrumental set-up to determine the requested number of orbits. Reduced gyro observations: our observations are not time critical, and can be scheduled any time, so reducing the possible observing windows will not affect this proposal. Using the visit planner tool, there are plenty of schedulable opportunities across the cycle for all 4 targets. Target acquisition is required for all of our targets in order to sucessfully complete the proposed observations. Dr Siyi Xu, Dr Beth Klein, Dr Carl Melis, Prof Ben Zuckerman, and Prof Patrick Dufour have been PI or CoI on a number of successful HST/COS proposals related to polluted white dwarfs, and have extensive experience with the preparation of observations, data reduction, and data analysis. Prof Patrick Dufour is an expert on models of white dwarfs, and will fit models to the obtained FUV spectra in order to get updated white dwarf parameters, and the abundances of the exo-planetary material that has polluted the atmospheres of the white dwarfs. Ms Laura Rogers has worked on the optical VLT/X-shooter and KECK/HIRES data of all our targets to obtain line strengths and, in collaboration with Prof Patrick Dufour, abundances of the exo-planetary material using the limited available optical lines. Ms Laura Rogers has vast experience analysing spectra and will perform a similar analysis on the HST/COS data. Dr Siyi Xu is an expert at radiative transfer models and is performing the models of the gaseous emission for all our targets, imperative for our comparison between the circumstellar gas composition and the photospheric composition. Dr Amy Bonsor is an expert in understanding the composition and geological history of the exo-planetary bodies that have been accreted, crucial to understanding the obtained abundances from Hubble. All team members have experience with and knowledge of observations of polluted white dwarfs, gas discs, and dust discs, and will all be of valuable help with the analysis. Everyone will contribute to the analysis of the data and the preparation of the publication. Exoplanets and Exoplanet Formation 6 false false true false false false false SUPPORTED STAR ACCRETION DISK DA EXTRA-SOLAR PLANETARY SYSTEM NO Target information from Simbad (Gaia DR2). J2000 J2000 Galex FUV = 15.8 STAR ACCRETION DISK DA EXTRA-SOLAR PLANETARY SYSTEM NO Target information from Simbad (Gaia DR2). GAIA-DR2-3415788525598117248 J2000 J2000 Galex FUV = 14.1 STAR ACCRETION DISK DA EXTRA-SOLAR PLANETARY SYSTEM NO Target information from Simbad (Gaia DR2). J2000 J2000 Galex FUV= 16.6 STAR ACCRETION DISK DB EXTRA-SOLAR PLANETARY SYSTEM NO Target information from Simbad (Gaia DR2). GAIA-DR2-1623866184737702912 WD-1622+587 J2000 J2000 Galex FUV = 16.26 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G130M 1291 1636117377219 /System/Volumes/Data/solaris/user1/wskipper/OP-cache/16752-v01.xml The scheduling data was generated by CASM 29.2. 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