6455( 4) - 07/31/96 15:56 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6455 Version: 4 Check-in Date: 31-Jul-1996 16:49:50 1.Proposal Title: Metal diffusion and radiative levitation in hot helium-rich white dwarfs ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle HOT STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Klaus Werner UNIVERSITAET POTSDAM CoI: Stefan Dreizler Universitaet Kiel N CoI: Ulrich Heber Universitaet Erlangen-Nuernberg N CoI: Ralf Napiwotzki Universitaet Erlangen-Nuernberg N CoI: Thomas Rauch Universitaet Potsdam N ------------------------------------------------------------------------------------ 6. Abstract We propose to observe five helium-rich (DO) white dwarfs in order to determine their photospheric CNO abundances. High- resolution high-S/N ultraviolet spectroscopy with the GHRS shall be performed in order to detect weak absorption lines. The data will be analysed with non-LTE metal line blanketed model atmospheres. The results will be compared to predictions from state-of-the-art diffusion/radiative levitation theory. In parallel, we will perform self-consistent diffusion calculations under non-LTE conditions. The observed metal abundances will serve as bench-marks for such kind of new calculations. As a basis for this work we have obtained high- S/N optical spectra of almost all known DO white dwarfs within the last five years. A comprehensive analysis of the atmospheric parameters is now available. For the present proposal we have selected five targets which represent the non -DA white dwarf cooling sequence from the hot end down to the DB gap. HST UV observations are crucial because the DO white dwarfs are generally too faint for high-S/N spectroscopy with IUE. No metal lines except from carbon in some stars were detected in the optical spectra. UV spectra allow the detection of metals at very low abundances. ------------------------------------------------------------------------------------ 6455( 4) - 07/31/96 15:56 - [ 2] Observations Description ------------------------ We want to obtain high-resolution UV spectra with the GHRS of five DO white dwarfs. Each target is observed in two wavelength regions which cover N and O lines. In a single case (HD149499B) the NIV resonance line is observed in addition, because enough time is available during one orbit to observe 3 spectral ranges. The regions to be covered are: Lambda 1 = 1229--1264Angstrom , This comprises the NV resonance doublet and the CIII singlet UV9. Lambda 2 = 1340--1375Angstrom , Here we cover two components of the OIV UV17 triplet and the OV 1371Angstrom line. Depending on T(eff) we expect to see either OIV or OV or both. In the latter case an independent check of T(eff) is possible. Lambda 3 = 1700--1735Angstrom , Covers the NIV 1718Angstrom line. begintableh caption The five proposed targets and detailed exposure times vspace0.3cm begintabular|lc|c|l|c| target & T(eff)/kK & V-mag & t_ exp/min & orbits , \\doacht & 95 & 15.6 & Lambda 1: 46 & 2 , & & & Lambda 2: 33 & , \\re & 70 & 13.7 & Lambda 1: 16 & 1 , & & & Lambda 2: 14 & , HS 0111+0012 & 65 & 14.8 & Lambda 1: 46 & 2 , HZ 21 & 53 & 14.2 & Lambda 1: 47 & 2 , & & & Lambda 2: 34 & , HD 149499 B & 49 & 11.7 & Lambda 1: 8 & 1 , & & & Lambda 2: 8 & , & & & Lambda 3: 14 & , endtabular endtable The photospheric NV resonance line can be blended by interstellar/circumstellar components. This can be corrected for, because the spectra cover lines which can unambigously be attributed to the photosphere (e.g.\\ OV) or to the interstellar system (low ionisation features), allowing to determine their relative velocity shifts. The G160M grating shall be used and we aim at a S/N of 30. For the faintest target we reduce our demand to S/N=20 in order to avoid excessive exposure times. For the brightest object a higher S/N (about 50) is achieved during a single-orbit visit. Table 2 summarizes the observations. The exposure times were estimated from our Cycle 4 observations of the hot DO white dwarf KPD0005+5106 with the identical instrumental set-up. They were then slightly changed to fit optimally within whole orbits. In all cases the LSA shall be used, including HD 149499 B. The light of the close cool companion is completely negligible in the UV below 2200Angstrom. The total number of requested orbits is 8. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6455( 4) - 07/31/96 15:56 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PG0108+101 STAR,WDO RA=01H 11M 06.58S +/- J2000 V = 15.6+/-0.2 0.1S,DEC=10D 21' 38.86" +/- B-V = -0.3+/-0.1 0.1",PLATE-ID=00GR 2 RE0503-289 STAR,WDO RA=05H 03M 55.39S +/- 0.1S,DEC=- J2000 V = 13.7+/-0.2 28D 54' 36.40" +/- 0.1",PLATE- B-V = -0.3+/-0.1 ID=04WB 3 HS0111+0012 STAR,WDO RA=01H 13M 46.81S +/- J2000 V = 14.8+/-0.2 0.1S,DEC=00D 28' 28.01" +/- B-V = -0.3+/-0.1 0.1",PLATE-ID=00WT 4 HZ21 STAR,WDO RA=12H 13M 56.41S +/- J2000 V = 14.2+/-0.2 0.1S,DEC=32D 56' 30.79" +/- B-V = -0.3+/-0.1 0.1",PLATE-ID=00Y2 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.133 -0.0067 0.0707 0.0 5 HD149499B STAR,WDO RA=16H 38M 31.24S +/- 0.1S,DEC=- J2000 V = 11.7+/-0.2 57D 28' 10.63" +/- 0.1" B-V = -0.3+/-0.1 6455( 4) - 07/31/96 15:56 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PG0108+101 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3,BRIGHT=RETURN 1 1.8 S ONBOARD ACQ FOR 2 Comments: STEP-TIME=0.2S, EXPECT 1600 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 PG0108+101 HRS ACCUM 2.0 G160M 1229-12 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 2502.4 64 ------------------------------------------------------------------------------------------------------------------------------------ 3 PG0108+101 HRS ACCUM 2.0 G160M 1340-13 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 1849.6 75 ------------------------------------------------------------------------------------------------------------------------------------ 6455( 4) - 07/31/96 15:56 - [ 5] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 RE0503-289 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3,BRIGHT=RETURN 1 1.8 S ONBOARD ACQ FOR 2 Comments: STEP-TIME=0.2S, EXPECT 20000 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 RE0503-289 HRS ACCUM 2.0 G160M 1229-12 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 761.6 S 64 ------------------------------------------------------------------------------------------------------------------------------------ 3 RE0503-289 HRS ACCUM 2.0 G160M 1340-13 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 761.6 S 75 ------------------------------------------------------------------------------------------------------------------------------------ 6455( 4) - 07/31/96 15:56 - [ 6] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HS0111+0012 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3,BRIGHT=RETURN 1 1.8 S ONBOARD ACQ FOR 2 Comments: STEP-TIME=0.2S, EXPECT 2400 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 HS0111+0012 HRS ACCUM 2.0 G160M 1229-12 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 4569.6 64 ------------------------------------------------------------------------------------------------------------------------------------ 6455( 4) - 07/31/96 15:56 - [ 7] Visit: 04 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HZ21 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3,BRIGHT=RETURN 1 1.8 S ONBOARD ACQ FOR 2 Comments: STEP-TIME=0.2S, EXPECT 4000 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 HZ21 HRS ACCUM 2.0 G160M 1229-12 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 2502.4 64 ------------------------------------------------------------------------------------------------------------------------------------ 3 HZ21 HRS ACCUM 2.0 G160M 1340-13 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 1958.4 75 ------------------------------------------------------------------------------------------------------------------------------------ 6455( 4) - 07/31/96 15:56 - [ 8] Visit: 05 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD149499B HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3,BRIGHT=RETURN 1 1.8 S ONBOARD ACQ FOR 2 Comments: STEP-TIME=0.2S, EXPECT 40000 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 HD149499B HRS ACCUM 2.0 G160M 1229-12 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 435.2 S 64 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD149499B HRS ACCUM 2.0 G160M 1340-13 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 435.2 S 75 ------------------------------------------------------------------------------------------------------------------------------------ 4 HD149499B HRS ACCUM 2.0 G160M 1700-17 FP-SPLIT=STD,COMB=FOUR,DOPPLER=ON 1 544.0 S 35 ------------------------------------------------------------------------------------------------------------------------------------ 6455( 4) - 07/31/96 15:56 - [ 9] Summary Form for Proposal 6455 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN DOPPLER=ON COMB=FOUR FP-SPLIT=STD ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names PG0108+101 RE0503-289 HS0111+0012 HZ21 HD149499B ------------------------------------------------------------------------------------------------------------------------------------