Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2282c Report Date: 09-May-96:17:01 Version: ********** Check-in Date: ********** 1.Proposal Title: SENSITIVE UV SPECTROSCOPY OF A HELIUM ATMOSPHERE DEGENERATE STAR ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GO 1 Long Term yrs Sub Category LATE EVOLUTION ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr Charles Alcock INST. OF GEOPHYS. AND PLANET USA 415-423-0666 ASTROPHYS CTR HEAD ------------------------------------------------------------------------------------ 7. Abstract We propose a sensitive search using the FOS for Lyman alpha absorption in the spectrum of a DB white dwarf star whose visible spectrum shows only helium absorption lines. The observed absence of H alpha and H beta absorption already shows that the N(H) to N(He) ratio is less than or equal to 10E(-4). The Lyman alpha line is approximately 100 times stronger than H alpha (for a given hydrogen abundance) so the potential upper limit to the hydrogen content is 100 times stronger than presently available. At the same time, we would obtain senstitive measurements of (or upper limits to) the UV resonance lines of carbon, magnesium, aluminum, silicon and iron. Detection of or upper limits to any of these lines would place significant constraints on the models of the atmospheres of this star, its accretion of interstellar and circumstellar material, and indirectly on their ages. ------------------------------------------------------------------------------------ 8. Scientific Key Words: WHITE DWARFS ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 4.60 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2282c PI: Dr Charles Alcock Proposal Title: SENSITIVE UV SPECTROSCOPY OF A HELIUM ATMOSPHERE DEGENERATE STAR ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr Charles Alcock LAWRENCE LIVERMORE NATL. LAB. USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will observe a white dwarf with the FOS using the G160L disperser. We wish to use the smallest aperature practical for this star in order to minimize geocoronal Lyman alpha. Since sky subtraction will be necessary, we will use a pair of aperatures to collect both object and sky spectra. The potential target is in the guide star catalog which should facilitate acquisition. Although we specify a single long exposure in the exposure sheet, the exposure can be broken up as appropriate for occultation or spacecraft efficiency. ------------------------------------------------------------------------------------ 11. Address Information Name: CHARLES ALCOCK Category: PI Institution: IGPP - LLNL Address: L-413 , P.O.BOX 808 City: LIVERMORE State: CA Zip Code: 94550 Country: USA Telephone: 415-423-0666 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2282c [ 3] ------------------------------------------------------------------------------------------------------------------------------------ 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 WD1645+325 STAR PLATE-ID = 01G4, J1984.0 1 V=13.5+/-0.5 RA=16H 47M 18.559S +/- 0.5", DEC=+32D 28' 32.57" +/- 0.5" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1984.00 -0.0093 +/- 0.0067 0.0600 +/- 0.0400 0.0000 +/- 0.0000 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2282c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 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 WD1645+325 FOS/BL ACQ/ 4.3 MIRROR BRIGHT=33000 001 0.35S 01 ONBOARD ACQ FOR 2 BINARY ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1645+325 FOS/BL ACCUM 0.25- G160L 1150- STEP-PATT=STAR- 001 15238S 1 PAIR 2524 SKY Comments: THE EXPOSURE CAN BE BROKEN UP AS APPROPRIATE. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2282c [ 5] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=33000 STEP-PATT=STAR-SKY ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 4.60 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category LATE EVOLUTION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names WD1645+325 ------------------------------------------------------------------------------------------------------------------------------------