Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5319 Report Date: 18-Jul-95:17:09 Version: ********** Check-in Date: ********** 1.Proposal Title: THE SULFUR AND IRON ABUNDANCE OF THE PECULIAR SDO STAR FEIGE 46: A CRUCIAL TEST OF THE DUST FRACTIONATION HYPOTHESIS CYC4 - MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category LATE EVOLUTION ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Ulrich Heber 5578 GERMANY +49 951 952221 ------------------------------------------------------------------------------------ 7. Abstract Feige 46 is a helium rich, subluminous O star that displays a very peculiar abundance pattern dissimilar to all other sdO stars analysed so far. C and N are almost solar whereas Mg and Si are deficient by a factor of 7 and 50, respectively. Its abundance pattern bears strong resemblence to that found in peculiar post-AGB F stars. Their depletion pattern are qualitatively similar to that found in the interstellar medium and therefore dust fractionation has been proposed as the origin of these pecularities. The same mechanism was recently suggested to explain the C/Si anticorrelation and the Si/Fe correlation found in normal A and Lambda Boo stars. This proposals sets out to test whether the dust fractionation mechanism can explain the abundance pattern of Feige 46. The measurement of the abundance of a volatile element such as Ar, S or Zn is necessary. For Feige 46 only S is accessible to a NLTE analysis at present via its strongest UV line at 1501.8 Angstroem. In addition the Fe/Si ratio shall be derived from UV spectra to check whether the A star correlation is also valid for Feige 46. Existing IUE spectra are of insufficient quality and the GHRS is required to obtain suitable data. If proven Feige 46 would be the first highly-evolved O-type star whose surface composition is governed by the separation of gas and dust. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 4.58 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5319 PI: Ulrich Heber Proposal Title: THE SULFUR AND IRON ABUNDANCE OF THE PECULIAR SDO STAR FEIGE 46: A CRUCIAL TEST OF THE DUST FRACTIONATION HYPOTHESIS CYC4 - MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Ulrich Heber 5578 GERMANY Stefan Dreizler 5578 GERMANY X Thomas Rauch 5584 GERMANY X Klaus Werner 5584 GERMANY X Keith Butler 5588 GERMANY X ------------------------------------------------------------------------------------ 3. Description of proposed observations. The GHRS equipped with the G160M grating shall be used to obtain UV spectral of the following four wavelength regions: i) 1485-1518 Angstroem to measure the crucial sulfur line , SV 1501.8 A ii) 1440-1473 Angstroem to measure the iron lines plotted in Fig. 4 iii) 1380-1413 Angstroem to measure the resonance doublet Si IV, 1392,1402A iv) 1325-1358 Angstroem to measure the OIV multiplet UV17 at 1338.6, 1343.0 and 1343.5A In order to measure well defined line prifiles a S/N of 40 per resolution element is aimed at. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. High resolution optical spectra of Feige 46 have been obtained with the ESO CASPEC spectrograph at the 3.6m telescope and were analysed by means of Non-LTE model atmospheres techniques. Ultraviolet spectroscopy of Feige 46 has been carried out with the IUE satellite. The star has been observed in the low resolution mode (about 0.5nm). These spectra of too low spectral resolution and too small S/N for the proposed investigation. Feige 46 has in addition been observed in the high resolution mode. However, the spectrum is very noisy and cannot be used to measure line profiles because the star is faint (V=13.3mag), see also Fig.3. ------------------------------------------------------------------------------------ 9. Description of previous HST work. ID 2741: A FOS spectrum with the blue detector, grating G130H and the 0.25"*1.4" aperture has been obtained on May 8, 1992. It has been analysed by comparing the normalized spectrum to synthetic spectra calculated From our NLTE model grid. The effective temperature has been determined with unprecedented accuracy (better than 3%) to be 140,000K). This fully confirmed the result of a previous optical nalysis and showed that systematic errors in that analysis are non-existent. Determination of C,N and O abundances is in progress. Due to better known Teff and the larger number of spectral lines the analysis will give much more reliable abundances that the early results based on optical spectroscopy. ID 3513: The observations have been carried out in May 1993 ID 4263: Observations are presently scheduled for December 93 and Januar 94. Archival FOS spectra: The hot DO star KPD0005+5106 has been analysed from HST-FOS spectra collected from the archive and using the same NLTE model atmosphere techniques as for PG1159-035 and proposed here for Feige 46. The photospheric parameters (Teff=120000K, log g=7) are derived from the He II lines in the UV and demonstrate that KPD0005+5106 is the hottest DO star known today. C and N abundance was also determined from the FOS spectra. KPD0005+5106 is of particular interest, since it is the first white dwarf to show ultra-high ionisation emission features (OVIII) in the optical and HST-FOS spectra. ROSAT observations shall help to identify the origin of the ultrahigh-ionisation lines. A prerequiste for such an investigation, however, is the precise knowledge of the photospheric X-ray spectrum. Page 3 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Computer resources: i) Micro VAX 3300 + 2 VAX Station 3100 of the DAN node Bamberg ii) Cray YMP/EL of the Universitaet Erlangen-Nuernberg iii) Cray YMP, Landesvektorrechner Muenchen iv) VAX 8550 of the "Rechenzentrum der Universitaet Kiel" v) Cray X-MP of the "Rechenzentrum der Universitaet Kiel" vi) Cluster of Unix-Workstations of the Institut fuer Theoretische Physik und Sternwarte der Universitaet Kiel Research assistance: Dr. H. Drechsel (system manager of the Bamberg DAN node), Dipl.Ing. G.Jonas (Kiel, data reduction specialist), ------------------------------------------------------------------------------------ 11. Address Information Name: ULRICH HEBER Category: PI Institution: 5578 Address: City: D State: Zip Code: Country: GERMANY Telephone: +49 9519522214 Telex (or e-mail): HEBER@STERNWARTE.UNI-ERLANGEN.D400.DE ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5319 [ 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 FEIGE46 A,108 RA= 11H37M26.450S +/- 0.1S, 2000 1 V=13.3 +/- 0.2, TYPE=SDO DEC=+14D10'15.20" +/- 0.1", 2 F-CONT(1500)=1.1 +/- 0.2E-12 PLATE-ID=019N 3 F-CONT(1460)=1.2 +/- 0.2E-12 4 F-CONT(1400)=1.4 +/- 0.2E-12 5 F-CONT(1340)=1.7 +/- 0.2E-12 6 B-V=-0.3+/-0.1 7 E(B-V)=0.0+/-0.1 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5319 [ 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 FEIGE46 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3 1 1.8S 3 1 CYCLE 4 BRIGHT=RETURN ONBOARD ACQ FOR LOCATE=YES 1.1 MAP=DEF Comments: STEP TIME = 0.2S; EXPECTED COUNTRATE 33000 C/S ------------------------------------------------------------------------------------------------------------------------------------ 1.1 FEIGE46 HRS ACQ/ 2.0 MIRROR-N2 1 61.2S 3 1 CYCLE 4 PEAKUP ONBOARD ACQ FOR 1.2-1.5 Comments: STEP TIME = 0.6S; EXP. COUNTRATE 33000 C/S TOO BRIGHT FOR STEP-TIME 1.6S? ------------------------------------------------------------------------------------------------------------------------------------ 1.2 FEIGE46 HRS ACCUM 2.0 G160M 1485- FP-SPLIT=FOUR 4 22.5M 50 2 1 CYCLE 4 1518 ------------------------------------------------------------------------------------------------------------------------------------ 1.3 FEIGE46 HRS ACCUM 2.0 G160M 1440- FP-SPLIT=FOUR 2 21.5M 40 3 1 CYCLE 4 1473 ------------------------------------------------------------------------------------------------------------------------------------ 1.4 FEIGE46 HRS ACCUM 2.0 G160M 1380- FP-SPLIT=FOUR 2 18M 40 4 1 CYCLE 4 1413 ------------------------------------------------------------------------------------------------------------------------------------ 1.5 FEIGE46 HRS ACCUM 2.0 G160M 1325- FP-SPLIT=FOUR 1 26M 30 5 1 CYCLE 4 1358 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5319 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN LOCATE=YES MAP=DEF FP-SPLIT=FOUR ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 4.58 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category LATE EVOLUTION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; ONBOARD ACQ FOR 1.1; ONBOARD ACQ FOR 1.2-1.5; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names FEIGE46 ------------------------------------------------------------------------------------------------------------------------------------