5866( 0) - 07/18/95 18:22 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5866 Version: ********** Check-in Date: ********** 1.Proposal Title: NLTE spectral analysis of PG1159 stars: Finding the limits of the GW Vir instability strip ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Hot Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Ulrich Heber Astronomisches Institut der Universitaet Erlangen-Nuernberg CoI: Stefan Dreizler Astronomisches Institut der Universitaet N Erlangen-Nuernberg CoI: Klaus Werner Institut fuer Theoretische Physik u. N Sternwarte der Universitaet Kiel CoI: Thomas Rauch Institut fuer Theoretische Physik u. N Sternwarte der Universitaet Kiel ------------------------------------------------------------------------------------ 6. Abstract The PG1159 stars form a new class of hydrogen deficient pre white dwarfs (PWD) representing the hottest stage of PWD evolution. Quan\-titative spectral analyses of all known PG1159 stars have been carried out by the proposers from optical, UV (IUE + HST-FOS) and EUV (EUVE) observations. It has been shown that these stars have atmospheres dominated by C and He. In the hottest stars also a significant amount of O is present. About every other member of the PG1159 stars is a non-radial, multi- periodic g-mode pulsator driven by cyclic ionization of C and O. Modelling of the pulsations allows the stellar mass to be determined very accurately and the stellar interior to be probed (asteroseismology). A prerequisite for such modelling is a precise determination of the photospheric parameters. We propose to obtain UV observations of 8 PG1159 stars (4 pulsators and 4 non-pulsators) in order to trace differences in photospheric parameters and composition (especially O). The spectra will be analysed with new highly sophisticated NLTE line blanketed model atmospheres, which allow the synthetic spectrum to be calculated and line blending of iron group elements to be included self\- consistently. The results will allow us to determine the position of the new instability strip (defined by the pulsating PG1159 stars) in the HRD. This is an updated version of cycle3 proposal 4263 which was awarded 9.48 hours FOS observing time (medium priority) but no observations were carried out. ------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 2] Observations Description ------------------------ Therefore we propose the following observations: , i) The ionOV 1371Angstrom\ line together with UV-ionOIV lines (1340Angstrom) are the only means to determine the O abundance and will reduce the uncertainties in T(eff) considerably. Fig.15 in WHH predicts an extreme temperature sensitivity of the ionOV line. It follows that the determination of T(eff) with a precision of 1\ can be measured to an accuracy of about 10\ ii) The ionNV, 1240Angstrom\ resonance line is the only means to determine the nitrogen abundance (no other N lines are detectable). Many other lines of CIV and OVI can be identified in the UV (see WHH) and will allow to determine abundances with unprecedented precision. Because of the high gravity, all spectral features are relatively broad and shallow. Hence a spectral resolution of about 1Angstrom\ is sufficient, which can be reached with the low dispersion GHRS grating (G140L) and the large science aperture. A high S/N ratio is necessary, however, in order to perform detailed line profile fits (S/N=60 to 90 is aimed at). IUE low resolution spectra exist of all targets, but they are too noisy and of too low resolution for a quantitative analysis. The resulting atmospheric parameters and abundances will constrain the position of the GW Vir instability strip in the HRD, probably as a function of the stellar surface abundances, especially of the O abundance. Exposure times and S/N have been calculated from available IUE fluxes, visibility periods, overhead times and the sensitivities given in the handbook. One visit is necessary for each star and we propose to observe each target for one orbit. An example: PG1707+427 is visible for 54 min. during one orbit; subtracting the overhead time for guide star and target acquisition as well as the instrument overhead (12 + 11 + 4 = 27 min.) 27 minutes of exposure time remain. PG1707+427 has a measured flux at 1350Angstrom\ of 1.5* 10^-13 erg/cm/cm/s/Angstrom. With a sensitivity of the G140L grating of S=166times10^11 S/N=64 is calculated from the equation on page 29 of the handbook. One target (HS0704+6153) lies in the continuous viewing zone and, hence, can be observed for 96 min. several times in the year. Since it is also the faintest of our programme stars, the S/N will benefit from the longer exposure time for HS0704. Two other targets (PG1424+535 and HS1517+7403) lie marginally in the CVZ. However the possibility to observe them during the entire orbit occurs only once or twice per year. Moreover, the stars are relatively bright, so that S/N~100 is reached within ~ 30 min. and the CVZ opportunity is not essential for these two stars. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: , ------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR- STAR,PG1159 STAR RA=15H 21M 46.542S +/- 0.013S, J2000 V = 15.5 +/- 0.2 1520+525 DEC=+52D 22' 3.85" +/- 0.2", B-V=-0.3 +/-0.1 PLATE-ID=01RT Comments: Coordinates have been measured by GASP in cycle 3 2 STAR- STAR,PG1159 STAR RA=14H 25M 55.412S +/- 0.013S, J2000 V = 16.2 +/- 0.2 1424+535 DEC=+53D 15' 24.76" +/- 0.2", B-V=-0.3 +/-0.1 PLATE-ID=01AL Comments: Coordinates have been measured by GASP in cycle 3 3 STAR- STAR,PG1159 RA=17H 8M 47.697S +/- 0.013S, J2000 V = 16.4 +/- 0.2 1707+427 STAR,PULSATING VARIABLE DEC=+42D 40' 59.95" +/- 0.2", B-V=-0.3 +/-0.1 PLATE-ID=009J Comments: Coordinates have been measured by GASP in cycle 3 4 STAR- STAR,PG1159 RA = 1H 25M 22.49S +/- 0.04S, J2000 V = 16.7 +/- 0.2 0122+200 STAR,PULSATING VARIABLE DEC = 20D 17' 56.9" +/- 0.5", B-V=-0.3 +/-0.1 PLATE-ID = 021K Comments: Coordinates are from an inventory GASP measurement by Karla Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.890 0.0 0.0 0.0 5 STAR-0130- STAR,PG1159 STAR RA = 1H 32M 39.32S +/- 0.02S, J2000 V = 16.2 +/- 0.2 1937 DEC = -19D 21' 40.6" +/- 0.32", B-V=-0.3 +/-0.1 PLATE-ID = 02J7 Comments: Coordinates are from GSC Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1980.787 0.0 0.0 0.0 6 STAR- STAR,PG1159 STAR RA = 7H 9M 32.24S +/- 0.07S, DEC J2000 V = 17.2 +/- 0.2 070459+61530 = 61D 48' 19.4" +/- 0.5", PLATE- B-V=-0.3 +/-0.1 9 ID = 034U Comments: Coordinates are from an inventory GASP measurement by Karla Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.850 0.0 0.0 0.0 7 STAR- STAR,PG1159 STAR RA = 15H 16M 46.36S +/- 0.11S, J2000 V = 16.7 +/- 0.2 151709+74030 DEC = 73D 52' 5.9" +/- 0.5", B-V=-0.3 +/-0.1 0 PLATE-ID = 01L5 Comments: Coordinates are from an inventory GASP measurement by Karla Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.294 0.0 0.0 0.0 8 STAR- STAR,PG1159 RA = 21H 34M 8.22S +/- 0.03S, J2000 V = 16.7 +/- 0.2 2131+066 STAR,PULSATING VARIABLE DEC = 6D 50' 57.4" +/- 0.5", B-V=-0.3 +/-0.1 PLATE-ID = 02V9 Comments: Coordinates are from an inventory GASP measurement by Karla Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.849 0.0 0.0 0.0 5866( 0) - 07/18/95 18:22 - [ 5] 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 STAR- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 9S ONBOARD ACQ FOR 2 1520+525 SIZE=3,BRIGHT=R ETURN Comments: STEP-TIME=1.0s, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1510.5S 1520+525 1456 SPLIT=STD,COMB= FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 6] 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 STAR- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 14.4S ONBOARD ACQ FOR 2 1424+535 SIZE=3,BRIGHT=R ETURN Comments: STEP-TIME=1.6S, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1443S 1424+535 1456 SPLIT=STD,COMB= FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 7] 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 STAR- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 20.7S ONBOARD ACQ FOR 2 1707+427 SIZE=3,BRIGHT=R ETURN Comments: STEP-TIME=2.3S, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1275S 1707+427 1456 SPLIT=STD,COMB= FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 8] 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 STAR- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 20.7S ONBOARD ACQ FOR 2 0122+200 SIZE=3,BRIGHT=R ETURN Comments: STEP-TIME=2.3S, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1158S 0122+200 1456 SPLIT=STD,COMB= FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 9] 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 STAR-0130- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 13.5S ONBOARD ACQ FOR 2 1937 SIZE=3,BRIGHT=R ETURN Comments: STEP-TIME=1.5S, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-0130- HRS ACCUM 2.0 G140L 1170- FP- 1 1239.6S 1937 1456 SPLIT=STD,COMB= FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 10] Visit: 06 Visit Requirements: CVZ On Hold Comments: Additional Comments: Without CVZ requirement the available exposure time for this faint target is too short for the desired SNR Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 32.4S ONBOARD ACQ FOR 2-3 070459+6153 SIZE=3,BRIGHT=R 09 ETURN Comments: STEP-TIME=3.6S, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1659S 070459+6153 1456 SPLIT=STD,COMB= 09 FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 3 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1659S 070459+6153 1456 SPLIT=STD,COMB= 09 FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 11] Visit: 07 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 STAR- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 20.7S ONBOARD ACQ FOR 2 151709+7403 SIZE=3,BRIGHT=R 00 ETURN Comments: STEP-TIME=2.3S, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1487.4S 151709+7403 1456 SPLIT=STD,COMB= 00 FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 12] Visit: 08 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 STAR- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 20.7S ONBOARD ACQ FOR 2 2131+066 SIZE=3,BRIGHT=R ETURN Comments: STEP-TIME=2.3S, EXPECT 500 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR- HRS ACCUM 2.0 G140L 1170- FP- 1 1150.8S 2131+066 1456 SPLIT=STD,COMB= FOUR,DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5866( 0) - 07/18/95 18:22 - [ 13] Summary Form for Proposal 5866 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 CVZ ONBOARD ACQ FOR 2-3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N1 G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names STAR-1520+525 STAR-1424+535 STAR-1707+427 STAR-0122+200 STAR-0130-1937 STAR-070459+615309 STAR-151709+740300 STAR-2131+066 ------------------------------------------------------------------------------------------------------------------------------------