Cannot find file /home/astro/btg/HST_midcycle_27.pdf 0 Assigned ID: 1164 ----- Attempting Submission 1 (Fri Sep 27 23:52:12 GMT 2019) ----- 0 ----- Attempting Submission 1 (Wed Nov 13 14:48:55 GMT 2019) ----- ----- Attempting Submission 2 (Mon Apr 20 10:00:04 GMT 2020) ----- Exploring evolved planetary systems: three new gaseous debris discs It is now established that planets survive the evolution of their host star into a white dwarf. Planetary remnants around a number of these ancient stars are revealed by compact debris disks, formed from the tidal disruption of planetesimals, which are detectable as IR flux excess. Accretion from these disks results in metal pollution of the otherwise pristine H or He white dwarf atmospheres, and the analysis of adequate optical and UV spectroscopy of these systems allows to reconstruct the bulk composition of the disrupted planetesimals. Deeper insight into the properties of the parent bodies arises from mineralogical studies of the dusty disks, but requires sensitive IR spectroscopy - available currently only for one single system. The imminent launch of JWST will enable revolutionary IR spectroscopic studies, and now is the time to identify the best targets for these JWST observations. White dwarf debris disks which contain copious amounts of metallic gas in addition to circumstellar dust are ideal targets, as they are actively undergoing planetesimal disruption events right now. However, these systems are extremely elusive, and so far, only three such systems were amenable to COS ultraviolet studies of their elemental abundances. We have identified three new gaseous debris disks, and request here COS spectroscopy to fully characterise the elemental abundances of the debris. With the atomic abundances in hand, these systems are prime targets for JWST IR spectroscopy, which will enable the detailed mineralogical modelling of the dusty debris. Combined, these observations will dramatically augment our knowledge of the composition and structure of rocky exo-planets. The goal of these observations is to obtain high signal-to-noise far-ultraviolet spectra of three white dwarfs which are accreting planetary debris from circumstellar debris disks. The planned COS spectroscopy will be used to measure the abundances of that material from the sharp photospheric metal lines. We use the G130M grating with two central wavelengths to maximise the wavelength covered by these observations, and to achieve gap-less coverage. We make use of all permitted FP-POS positions, i.e. 3 & 4 for @1291A, and 1,2,3,4 @ 1222A. The @1291A and @1222A observations are split into two separate visits to facilitate the scheduling. This program should not be affected in case that HST moves to a 2-gyro mode. Gentile Fusillo has been using large astronomical surveys to (a) identify white dwarfs, most recently producing the first all-sky catalogue of white dwarfs using Gaia DR2, and (b) to then search for white dwarfs with signature of evolved planetary systems. He identified the target of this proposal. Gaensicke has been PI of 20 HST programs, carrying out far-ultraviolet spectroscopy of white dwarfs, including large, medium, small GO programs and several snapshot programs. He has in-depth experience in the analysis and interpretation of the observations of accreting white dwarfs, both in binary systems, and evolved planetary systems. He will implement the observations, and lead the analysis. Koester has developed the model atmosphere code that will be used for this project, and he will provide guidance on the use of the code. Toloza is an expert in the analysis of COS time-tag observations. She will carry out the data reduction and the computation of white dwarf model atmospheres using the code of Detlev Koester. Manser is an expert on gaseous debris disks at white dwarfs, and he will contribute to the discussion of the line morphology. He recently identified the first spectroscopic signature of a solid planetesimal. Planets and Planet Formation 0 false false true false true false false SUPPORTED STAR DA NO J2000 J2000 GALEX FUV=16.7 STAR DA NO J2000 J2000 STAR DA NO J2000 J2000 GALEX FUV=16.9 COS/FUV Spectroscopic No No G130M 1222 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G130M 1222 COS/FUV Spectroscopic No No G130M 1291 COS/FUV Spectroscopic No No G130M 1222 COS/FUV Spectroscopic No No G130M 1291 The scheduling data was generated by CASM 28.0. CASM was run in Phase II mode. 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(Tic-Visit :proposal-id 16035 :visit-id "H1" :proposal-version -1 :trans-version "20191203" :date "20-Apr-2020 11:57:02.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 147936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16035 :visit-id "H1" :obset-id "H1" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16035 :visit-id "H1" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2787 :al-overhead-at-end 0 :internal-dur-at-end 379 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3180 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 28.0. 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