Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2741c Report Date: 09-May-96:17:17 Version: ********** Check-in Date: ********** 1.Proposal Title: NLTE SPECTRAL ANALYSIS OF THE PRE WHITE DWARF PG1159-035 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GO Sub Category ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Prof. K. Hunger KIEL UNIVERSITY FRG 431-880-4110 DIRECTOR ------------------------------------------------------------------------------------ 7. Abstract PG1159-035 is the prototype of a new class of hydrogen-deficient pre white dwarfs (PWD) representing the hottest episode (Teff.GE.100,000K) of PWD-evolution. It also shows low-amplitude multi-periodic variations which have been identified as non- radial g-mode pulsations. Because of these properties, PG1159-035 is a rosetta stone for our understanding of the late phase of stellar evolution. Modelling of the pulsations not only allows the stellar mass to be determind but also the internal structure to be probed. However, the position of PG1159-035 in the HR diagram and its chemical surface composition are a prerequisite for the pulsational models as well as for the discussion of its evolutionary status. Due to the lack of adequate model atmospheres, these basic atmospheric parameters have not yet been determined. To construct such models is a challenging problem because non-LTE effects are large and a very peculiar composition (He-, C- and O-rich) has to be accounted for. Since available model atmosphere techniques fail, we have developed a new computer code based on operator perturbation techniques which gave way to a new generation of highly sophisticated non-LTE model atmospheres. Proposed HST spectroscopy of crucial UV lines will allow the basic atmospheric parameters to be determined with high precision. These will set important constraints to be met by pulsational and evolutionary models. ------------------------------------------------------------------------------------ 8. Scientific Key Words: STARS: WHITE DWARFS; NON-LTE ANALYSIS ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 2.25 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2741c PI: Prof. K. Hunger Proposal Title: NLTE SPECTRAL ANALYSIS OF THE PRE WHITE DWARF PG1159-035 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ P.I. K. Hunger KIEL UNIVERSITY FRG X U. Heber KIEL UNIVERSITY FRG X Th. Rauch KIEL UNIVERSITY FRG X K. Werner KIEL UNIVERSITY FRG X ------------------------------------------------------------------------------------ 3. Description of proposed observations. The ST High Resolution Spectrograph (HRS) shall be used to obtain ultraviolet spectroscopy of PG1159-035. Scientific spectra to be obtained with the HRS (large science aperture, LSA, 2*2 arcsec.) are as follows: i) Low resolution spectrum (grating G140L) in the wavelength range 115 nm - 143.6 nm in order to observe the NV resonance doublet at 124 nm. (optimum) S/N = 60 is aimed at. Low resolution (R = 2000) suffices since IUE high resolution spectra show the lines to be relatively strong and unblended. ii) Medium resolution spectrum (grating G160M) in the wavelength range 135.3 nm to 138.6 nm in order to measure the crucial OV, 137.1 nm line. S/N = 30 is aimed at. Medium resolution (R = 20000) is required since IUE high dispersion spectra indicate that the line is weak. Proper continuum placement will be assured from the low resolution spectrum (i). iii) Medium resolution spectrum (grating G160M) in the wavelength range 153.3 nm to 156.6 nm in order to measure the profile of the CIV resonance doublet at 155 nm. S/N = 30 is aimed at. Medium resolution (R = 20000) is required because the photospheric lines are blended with interstellar components. Proper continuum placement will be assured from summed low resolution spectra, which will become available during GTO-program No. 1148. It is intended to utilize these spectra when officially released to the public. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Optical spectra of high S/N ratio (near 100) have been obtained at ESO, 3.6 m telescope and at DSAZ-3.5 m telescope, covering the wavelength range 400 nm to 700 nm at a spectral resolution of 0.3 nm. These spectra have been used for an exploratory NLTE analysis (see Sect. 2 and Werner et al., 1988). Well exposed low resolution IUE spectra (optained with the SWP and LWR cameras) required 15 min and 30 min of exposure time, respectively. However, extremely long high- resolution IUE spectrum (1020 min) allowed crucial lines to be detected. However, S/N is too low for a quantitative analysis. Therefore, the UV lines of crucial importance for the analysis (see Sect. 2) can only be observed with HST/HRS. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. 1 Object (PG1159-035) shall be observed with the HRS (3 images). Blind acquisition appears to be possible since the stars lies in an uncrowded field and will have been observed with HST/HRS before the proposed observations (GTO proposal No. 1148). Exposure times can be estimated from absolutely calibrated UV fluxes (IUE) and the HRS efficiency (Duncan and Turnshek, 1988, STScI-Newsletter, Vol. 5, No 3). These values are listed below: Wavelength S/N grating S- lambda F-lambda (erg/ t (nm) (flux) cm/cm/s/0.1nm) (min.) 137 30 G160M 5.6E11 9.4E-13 28 155 30 G160M 8.2E11 5.5E-13 33 124 60 G140L 1.18E13 1.3E-12 4 Page 3 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Data reduction of HRS spectra will be carried out using procedures implemented in the MIDAS package of the European Coordinated Facility (Garching), which will be installed on the VAX 8550 of the "Rechenzentrum der Universitaet Kiel". Observed profiles will be compared to theoretical predictions in order to derive Teff, log g and abundances. To this end, the model atmosphere calculations described in sect. 2 will be extended. Numerical calculations will be carried out using the Cray X-MP 216 computer of the "Rechenzentrum der Universitaet Kiel". ------------------------------------------------------------------------------------ 8. Additional comments or special requests. No special requests. References: Auer, L.H., Mihalas, D.: 1969, Astrophys. J. 158, 641 Fontaine, G., Wesemael, F.: 1987, IAU coll. No. 95, 319 Heber, U., Hunger, K.: 1987, IAU coll. No. 95, 599 Heber, U., Hunger, K., Rauch, T., Werner, K.: 1987, IAU Symp. 132, 117 Heber, U., Hunger, K., Werner, K.: 1987, IAU Symp. No. 132, 389 Heber, U., Werner, K., Drilling, J.S.:1988, Astron. Astrophys. 194, 223 Kawaler, S.D.: 1987, IAU coll. No. 95, 297 Liebert, J.W.: 1988, IAU Symp. No. 131, in press Rauch, T., Werner, K.: 1988, Astron. Astrophys. 202, 159 Sahal- Brechot, S., Segre, E.R.A.: 1971, Astron. Astrophys. 13, 161 Starrfield, S.: 1987, IAU coll. No. 95, 309 Vidal, C.R., Cooper, J., Smith, E.W.: 1969, Phys. Rev. 185, 140 Werner, K.: 1987, in "Numerical Radiative Transfer", Cambridge Univ. Press p. 67 Werner, K.: 1988, Astron. Astrophys. 204, 159 Werner, K., Heber, U., Hunger, K.: 1988, IAU coll. No. 114 in press Winget, D., Kepler, S.O., Robinson, E., Nather, R.E., O'Donoghue, D.: 1985, Ap. J. 292, 606 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Computer resources: i) VAX 8550 of the "Rechenzentrum der Universitaet Kiel"; MODCOMP CLASSIC of the "Physikzentrum der Universitaet Kiel"; to be used for data reduction. ii) CRAY X-MP 216 of the "Rechenzentrum der Universitaet Kiel" to be used for NLTE model atmosphere calculations. Research assistance: Dipl. Ing. G. Jonas (data reduction specialist) . Two graduate students will assist the proposers in the spectral analysis. ------------------------------------------------------------------------------------ 11. Address Information Name: K. HUNGER Category: PI Institution: KIEL UNIVERSITY Address: INSTITUT F. THEOR. PHYSIK OLSHAUSENSTRASSE 40 City: KIEL D-2300 State: Zip Code: Country: F.R. GERMANY Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2741c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 GW-VIR STAR; TYPE=DOZ PRE- RA = 12H 1M 45.981S +/- 2000 1 V = 14.87 +/- 0.2, TYPE=DOZ, E(B- PG1159-035 WHITE-DWARF 0.013S, 2 V)=0.00 DEC = -3D 45' 40.74" +/- 3 F-CONT(1370) = 9.4 +/- 1.0 E-13 0.2", 4 F-CONT(1550) = 5.5 +/- 0.6 E-13 PLATE-ID=0309 F-CONT(1240) = 1.3 +/- 0.1 E-12 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2741c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GW-VIR FOS/BL ACQ/ 4.3 MIRROR FAINT=780 1 0.66S 1 CYCLE 1 BINARY BRIGHT=39000 ONBOARD ACQ FOR 1.100 ------------------------------------------------------------------------------------------------------------------------------------ 1.1 GW-VIR FOS/BL ACQ/ 0.25X2. MIRROR TYPE=UP 1 3S 1 CYCLE 1 PEAK 0 SPATIAL SCAN ONBOARD ACQ FOR 2. ------------------------------------------------------------------------------------------------------------------------------------ 2 GW-VIR FOS/BL ACCUM 0.25X2. G130H 1200- 1 103M 120 4 1 CYCLE 1 0 1600 ------------------------------------------------------------------------------------------------------------------------------------ Scan Paramters Form Proposal ID: 2741c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 1.1 FGS Scan: DWELL Dwell Only: dwell points/line: 11 Seconds per dwell: 0.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 0.5500 Angle between sides (degrees) 0.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 90.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 0.2250 Width Offset (arc-sec): 0. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2741c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FAINT=780 BRIGHT=39000 TYPE=UP ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 2.25 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 1; ONBOARD ACQ FOR 1.100 SPATIAL SCAN ; ONBOARD ACQ FOR 2. CYCLE 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names GW-VIR PG1159-035 ------------------------------------------------------------------------------------------------------------------------------------