0 Assigned ID: 7703 ----- Attempting Submission 1 (Thu Apr 16 22:01:46 GMT 2026) ----- First Phase II submission -1374835017 ----- Attempting Submission 1 (Sun Aug 09 21:48:21 GMT 2026) ----- Rockin' photospheres: how White Dwarf stars respond to heavy metal accretion Metal-polluted WDs are important laboratories for studying the composition of exoplanets and the evolution of the planetary systems, where these metals originated. The far-UV wavelength range is crucial for these studies, as they host a large number of metal-line transitions that provide subtle diagnostics of the WD photospheric properties, yet only a handful have been observed at wavelengths below 1140 Angstroms. We propose to use the Cosmic Origins Spectrograph to observe five metal-line WDs with a wide range of inferred accretion rates using the G130M/1055 mode, which spans the Lyman Ultraviolet (~912 to 1200 A) and includes lines from several elements including N, P, S and Si. We will also observe a comparison set of four pristine WDs, which will allow us to accurately flux-calibrate our entire sample and investigate how the photospheres of WDs with Teff~20,000 K behave under different accretion conditions. All targets will be acquired using NUV ACQ/IM using the BOA. MIRROR A will be used for all targets except WD 1134+300 (GD 140, Target 6, Visit 06), which will use MIRROR B. The exposure times have been rounded up slightly to ensure the acquisitions are successful ------------------- The science exposure will use G130M/1055 at the default lifetime position, LP7. The ETC numbers reported are those using synthetic models and specifying S/N=10 at 1085A. Note that the S/N changes sharply around this wavelength for all targets because of the throughput cliff at 1150A as well as their intrinsic spectra. The spectral region of interest extends down to the Lyman limit (for WD models), and to approximately 1050A for observing the photospheric metal lines. Therefore the exposure times from the ETC runs are minimum required values. (They provide the correct buffer fill times and the correct brightest pixel rates.) For most of the target we have chosen exposure times that are within the orbit allocation, but do not fill the orbits. The exceptions are for the faintest targets/visits 04 and 07 where we have used the auto-adjust feature to maximize exposure times. ------------------- We note that the orbit request in the Phase I proposal used v33.1 of the exposure time calculator. The new synphot files along with the expected time-dependent sensitivity trend used in v34.2 have resulted in moderate increases in the exposure times, but more importantly in significant decreases in the brightest pixel count-rates. Our Phase I proposal reported a COS lifetime impact measure of 153 counts based on those minimum required exposure times. Our actual exposure times used in the Phase II yield a slightly lower impact measure of 144 counts. T. Cunningham is an expert on the high energy signatures of white dwarf accretion. J. Debes is a COS instrument scientist, an expert in white dwarf spectroscopy and planetary systems in orbit around white dwarfs S. Deustua's principal research area at present is precision spectrophotometric calibration of astrophysical sources, with a focus on establishing flux standard stars with high accuracy. She has extensive experience with UV to IR imaging and spectroscopy using ground-based telescopes and HST instruments, and with instrument calibration. She is PI of the CANDLE and NIST Stars projects. P. Dufour and E. Le Bourdais are experts in white dwarf modeling, with a focus on determining the abundances of metal pollution as well as modeling circumstellar disks around WDs J. Holberg is one of the world's experts in WD astrophysics. He is an expert in UV astronomy and has led and participated in several key programs undertaken with HST/STIS, FUSE, IUE and other instruments. R. Sankrit is a COS instrument scientist and has extensive experience with flux calibration of the instrument using standard white dwarfs. He led the study to understand the impact of model uncertainties on the calibration in the short-wavelength regime. S. Xu has worked extensively on high resolution spectroscopic studies of polluted white dwarfs and led the publication of the first detection of Nitrogen in a polluted white dwarf (Xu, S. et al. 2017, ApJL, 836, L7) Stellar Physics and Stellar Types 6 false true false false false false false SUPPORTED STAR DA DZ NO 2026_Jul_24: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. GD683 J2000 J2000 STAR DA NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. EGGR150 J2000 J2000 STAR DA DZ NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. LAWD52 J2000 J2000 STAR DA DB DZ NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. GD378 J2000 J2000 STAR DA DZ NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. KPD0420+5203 J2000 J2000 STAR DA NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. GD140 J2000 J2000 STAR DA NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. LB769 J2000 J2000 STAR DA NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. TON556 J2000 J2000 STAR DB NO 2026_Jul_27: target information verified RS This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. WG7 J2000 J2000 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. 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CASM was run in Phase II mode. (Tic-Visit :proposal-id 18370 :visit-id "02" :proposal-version -1 :trans-version "20260618" :date "09-Aug-2026 17:03:08.0" :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 435008 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18370 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18370 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2571 :al-overhead-at-end 0 :internal-dur-at-end 423 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2979 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. 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(Tic-Visit :proposal-id 18370 :visit-id "04" :proposal-version -1 :trans-version "20260618" :date "09-Aug-2026 17:14:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 843936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18370 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18370 :visit-id "04" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2621 :al-overhead-at-end 0 :internal-dur-at-end 2268 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3001 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18370 :visit-id "04" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2612 :al-overhead-at-end 0 :internal-dur-at-end 2277 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3001 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18370 :visit-id "04" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2621 :al-overhead-at-end 0 :internal-dur-at-end 703 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3001 :pcs-gap 0 ) false 3 0 The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. 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CASM was run in Phase II mode. (Tic-Visit :proposal-id 18370 :visit-id "06" :proposal-version -1 :trans-version "20260618" :date "09-Aug-2026 17:05:12.0" :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 435008 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18370 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18370 :visit-id "06" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2541 :al-overhead-at-end 0 :internal-dur-at-end 423 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2983 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 34.2. CASM was run in Phase II mode. 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CASM was run in Phase II mode. 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