Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5339 Report Date: 18-Jul-95:17:12 Version: ********** Check-in Date: ********** 1.Proposal Title: CENTRAL STARS OF PLANETARY NEBULAE: A TEST OF THE RADIATIVELY DRIVEN WIND THEORY: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category SUBDWARFS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Roberto Mendez 5588 GERMANY +49-89-9220944 ------------------------------------------------------------------------------------ 7. Abstract We propose to test the radiatively driven wind theory for central stars of planetary nebulae (CSPN). The test is interesting because CSPN differ substantially from the luminous and massive Pop.I stars. There is a clear discrepancy between spectroscopic+wind masses versus evolutionary masses of Pop.I OB stars. The result of the CSPN test would help to decide which masses need correction, with obvious impact on stellar atmosphere and stellar evolution theory. A well-tested and confirmed wind theory would become a powerful tool for stellar spectroscopic mass, radius, distance and luminosity determinations throughout the Local Group. In order to make this test with maximum efficiency we have selected a sample of CSPN with temperatures similar to those of Pop.I OB stars and showing a variety of wind strengths. We wish to obtain high S/N ultraviolet spectrograms with HST+FOS. Our list of CSPN necessarily includes faint and reddened objects which can only be observed with HST. FOS spectra in the range from 1150 to 2300 Angstroms, combined with existing high resolution optical data, will provide reliable values of Teff, log g, photospheric abundances and mass loss rates, using sophisticated NLTE "unified" models and NLTE metal line formation calculations including wind effects. This input will be used to predict, from wind models, the P Cygni profiles of UV resonance lines, to be compared with the observed ones. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 0.63 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5339 PI: Roberto Mendez Proposal Title: CENTRAL STARS OF PLANETARY NEBULAE: A TEST OF THE RADIATIVELY DRIVEN WIND THEORY: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Roberto Mendez 5588 GERMANY X Rolf-Peter Kudritzki 5588 GERMANY X Rudi Gabler 5588 GERMANY X Keith Butler 5588 GERMANY X Sylvia Becker 5588 GERMANY X Adi Pauldrach 5588 GERMANY X Joachim Puls 5588 GERMANY X Daniel Lennon 5588 GERMANY X Dirk Husfeld 5588 GERMANY X ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will observe the central star of the planetary nebula He 2-108. This star has a Teff of 33000 K and a strong wind, as indicated by the presence of emission at the wind-sensitive stellar line He II 4686. The V magnitude is 12.7, and E(B-V) = 0.4. We can take one spectrogram of this star, using the FOS and the blue detector with grating G130H. The S/N ratio must be at least 70. The spectral coverage will run from 1150A to 1600A and will contain all the important wind lines needed for our analysis: NV 1239,1243; CII 1334,1336; SiIV 1394,1403; CIV 1548,1551; plus a large number of photospheric lines due to Fe and Ni. The resolution of FOS (approximately 200 km/s) is not a problem for the analysis of the wind features. The photospheric line spectrum suffers from such blending problems that spectral synthesis techniques are necessary to derive abundances in any case. A very high S/N ratio is essential for such studies. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The UV spectrum is essential for our analysis, because it provides crucial information about the atmosphere and wind of our object. The UV stellar wind lines provide estimates of Vinfinity, and their profiles will be compared with the predicted ones in the last step of the analysis. The iron group elements do not show adequate optical lines for an abundance analysis, but have a rich UV spectrum. Several UV lines will be useful for ionization equilibrium studies which will provide additional constraints on the stellar Teff. Our object is too faint and reddened to be observed with IUE at the required signal-to-noise ratio. HST/FOS observations are therefore necessary for this project. In the last 5 years we have published a number of papers on the NLTE model atmosphere analysis of CSPN, based on high-resolution optical spectrograms obtained with the ESO 3.6m telescope and the INT telescope at La Palma, Canary Islands. In particular our target in this proposal has already been observed from a ground-based observatory at high spectral resolution, and the corresponding first-step (plane-parallel, hydrostatic) NLTE model atmosphere study has been made. We have estimated the HST/FOS exposure time using observed UV stellar fluxes (IUE low-resolution spectra). The requested signal to noise ratio (at least 70) is based upon previous experience gained with this instrumentation and is necessary to enable us to measure terminal velocities, by fitting the wind lines, to within 150 km/s and for the synthesis of line blends in the UV. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. No special scheduling requirements. Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. No special calibrations required. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. No additional comments. ------------------------------------------------------------------------------------ 9. Description of previous HST work. GTO No. 1215 ULTRAVIOLET SPECTRAL ATLAS OF O-STARS IN THE MILKY WAY AND MAGELLANIC CLOUDS (RPK). GO No. 2233/4110 THE PHYSICS OF MASSIVE O-STARS IN DIFFERENT PARENT GALAXIES (RPK, KB, DH, AP, JP). GO No. 2581 STELLAR WINDS OF MASSIVE STARS IN NEARBY GALAXIES (RPK). GO No. 4550 MASSIVE STAR EVOLUTION FROM CARBON AND OXYGEN ABUNDANCES IN LMC WC STARS (RPK, KB, DJL). The present proposal is not directly related to any of the above proposals except in so far as it concerns the same general topic of quantitative spectroscopy of hot stars. The present proposal is specifically aimed at the analysis of central stars of planetary nebulae, a problem none of the above proposals deals with. GTO proposal 1215 and GO proposal 2581 are completed and results have been published in the literature (see below for examples). GO proposals 2233/4110 and 4550 are incomplete. The former still has observations of 4 early O-stars in the SMC outstanding which are crucial to interpretation of the metallicity dependence of mass loss rates in the galaxy, LMC and SMC. Nevertheless preliminary results for some stars have been published. To date no data for proposal 4550 have been obtained. (1) First Results from the GHRS: Spectroscopic determination of stellar parameters of an O3f star, Melnick 42, in the Large Magellanic Cloud: Heap, S.R., Altner, B., Ebbets, D., Hubeny, I., Hutchings, J.S., Kudritzki, R.P. Voels, S.A., Haser, S., Pauldrach, A., Puls, J., Butler, K., 1991., Ap. J. Let., 377, L29. (2) Hot stars and the Hubble Space Telescope: Kudritzki, R.P., Lennon, D.J. Becker, S.R., Butler, K., Gabler, R., Haser, S., Husfeld, D., Pauldrach, A., Puls, J., Voels, S., 1993, in: Science with the Hubble Space Telescope, ESO Wokshop and Conference Series No 44, p279. (3) The stellar wind of an O8.5Ia(f) stars in M31 - no evidence for abnormally low mass loss: Haser, S.M., Lennon, D.J., Kudritzki, R.P., Puls, J., Astron. Astrophys., submitted, 1993. (4) Radiation driven winds of hot stars. XII. A first step towards detailed UV line diagnostics of O-stars: Pauldrach, A.W.A., Kudritzki, R.P., Puls, J., Butler, K., Hunsinger, J., Astron. Astrophys., in press, 1993. (5) Quantitative spectroscopy of O-stars in the Magellanic Clouds. II. The O3 stars Sk-67 211 and Sk-68 137 in the LMC: Husfeld, D., Lennon, D.J., Kudritzki, R.-P., Gabler, R., Pauldrach, A.W.A., Puls, J., Voels, S., Conti, P.S., Wachter, S., Astron. Astrophys. in press. 1993. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Munich University: data reduction and analysis facilities and personnel are described under section 7. There are no problems with the funding of the necessary computer calculations required for this project. Funds for travel, preparation of observations, reduction, etc will also be available. ------------------------------------------------------------------------------------ 11. Address Information Name: ROBERTO MENDEZ Category: PI Institution: 5588 Address: INSTITUT F ASTRON U ASTROPHYS DER UNIVERSITAET SCHEINERSTRASSE 1 81679 MUENCHEN City: MUNICH State: Zip Code: Country: GERMANY Telephone: +49-89-92209442 Telex (or e-mail): MENDEZ@USM.UNI-MUENCHEN.DE ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5339 [ 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 PK316+8D1 A,184 PLATE-ID=039T, 2000 V = -8 1 V=12.7,B-V=0.1,E(B-V)=0.4 HE2-108 RA = 14H 18M 8.79S +/- 0.1S, 2 F-CONT(1400) = 15 +/- 3 E-14 GSC8289- DEC = -52D 10' 39.7" +/- 00125 0.2" ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5339 [ 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 PK316+8D1 FOS/BL ACQ/ 4.3 G190H SCAN-STEP- 1 5S 2 1 ONBOARD ACQ FOR 2 PEAK Y=1.204 CYCLE 4 / 1-5 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 PK316+8D1 FOS/BL ACQ/ 1.0 G190H SCAN-STEP- 1 6S 2 1 ONBOARD ACQ FOR 3 PEAK X=0.602 SCAN-STEP- Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 PK316+8D1 FOS/BL ACQ/ 0.3 G190H SCAN-STEP- 1 7S 2 1 ONBOARD ACQ FOR 4 PEAK X=0.172 SCAN-STEP- Y=0.172 SEARCH-SIZE-X=5 SEARCH-SIZE-Y=5 ------------------------------------------------------------------------------------------------------------------------------------ 4 PK316+8D1 FOS/BL ACQ/ 0.3 G190H SCAN-STEP- 1 7.0S 2 1 ONBOARD ACQ FOR 5 PEAK X=0.052 SCAN-STEP- Y=0.052 SEARCH-SIZE-X=5 SEARCH-SIZE-Y=5 ------------------------------------------------------------------------------------------------------------------------------------ 5 PK316+8D1 FOS/BL ACCUM 0.3 G130H 1 2280.0S 70 2 1 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5339 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.204 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-X=0.602 SCAN-STEP-Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 SCAN-STEP-X=0.172 SCAN-STEP-Y=0.172 SEARCH-SIZE-X=5 SEARCH-SIZE-Y=5 SCAN-STEP-X=0.052 SCAN-STEP-Y=0.052 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 0.63 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category SUBDWARFS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2; CYCLE 4 / 1-5; ONBOARD ACQ FOR 3; ONBOARD ACQ FOR 4; ONBOARD ACQ FOR 5; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G190H G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names PK316+8D1 HE2-108 GSC8289-00125 ------------------------------------------------------------------------------------------------------------------------------------