5893( 0) - 07/18/95 18:29 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5893 Version: ********** Check-in Date: ********** 1.Proposal Title: Deuterium in the local interstellar medium toward hot stars ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Interstellar Medium GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Alfred Vidal-Madjar Institut d'Astrophysique de Paris CoI: J. Webb University of New South Wales N CoI: J. Audouze Institut d'Astrophysique de Paris N CoI: M. Casse Service d'Astrophysique DAPNIA, Saclay N CoI: R. Ferlet Institut d'Astrophysique de Paris N CoI: C. Gry Laboratoire d'Astrophysique de Marseille N CoI: D. Koester Universitaet Kiel N CoI: M. Lemoine Institut d'Astrophysique de Paris N CoI: E. Vangioni-Flam Institut d'Astrophysique de Paris N ------------------------------------------------------------------------------------ 6. Abstract The proposed observations are the necessary continuation of an approved Cycle 1 proposal aiming at deriving the deuterium abundance in the local interstellar medium toward nearby hot stars. The present D/H ratio within the galaxy is one of the key- parameters of galactic evolution models. Although a very accurate measurement of the interstellar D/H ratio was made recently toward Alpha Aur using HST-GHRS (Linsky et al., 1993), it seems to us that the value of the present D/H ratio is not settled as yet. Many data set, as well as our recent Cycle 1 data toward G191-B2B, have suggested the possible existence of variations of this ratio, which might have some consequence on the galactic evolution of deuterium. These same Cycle 1 data seem to indicate also that a refined estimate of the Linsky et al. value should lie closer to 1.4 times 10^-5 than to 1.7 times 10^-5. We propose to carry out new and highly accurate measurements of the D/H ratio in the local medium by complementing our Cycle 1 observations toward G191-B2B with observations of two extremely important spectral regions using the Ech-A grating, namely the N I triplet (1200Angstrom) and the Lyman-alpha line where our previous G160M grating prevented us from constraining more tightly the D/H ratios. The efficiency and the availability of the Ech-A grating, as well as the quality of our already acquired data provides exceptional opportunities for carrying out precise measurements of D/H ratios in a relatively short integration time. ------------------------------------------------------------------------------------ 5893( 0) - 07/18/95 18:29 - [ 2] Observations Description ------------------------ We plan to perform the following observations using the Small Science Aperture (SSA): Object Wavelength Grating count/s/d G191-B2B N I 1200A Ech-A47 0.3 H I 1216A Ech-A46 0.07 O I 1302A Ech-A43 0.42 The fluxes of G191-B2B at 1200Angstrom, 1215Angstrom, 1302Angstrom were taken from our previous HST-GHRS observations and from Snow & Jenkins (1977). These fluxes were converted into counts/s/diode using the Post- Costar GHRS Instrument Handbook data (table 8.3 for Ech-A, table 8.4 for Ech-B and table 8.2 for G160M) taking into account the blaze function of the Echelle gratings and a throughput of 50\ Epsilon CMa flux at 1200Angstrom is 2.2times10^-8 erg.s^-1.cm^-2.AA^-1, the sensitivity of Ech-A in the 47th order is 0.46times10^11 counts/s/diode/(erg.s^-1.cm^-2.AA^-1), with a factor 0.96 arising from the blaze function and a factor 0.5 to convert to the use of the SSA, gives 486 counts/s/diode., We then convert these counts into integration time by requiring a signal-to-noise ratio at least S/N=20 per pixel, i.e. S/N=40 per diode. The photon noise is dominating in all considered settings. The orbits are calculated following the instructions of the Phase I Proposal Handbook:, - G191-B2B will be acquired with the N1-N2 mirrors, which asks for 31 minutes during the first orbit for each, i.e. 12 mn for acquiring the guide star, 11 mn for acquiring the target and another 8 mn for peak-up. Each exposure will be preceded by a WAVE exposure (3 mn) in order to have accurate radial velocities for each interstellar component in each setting, and 4 mn overhead are taken into account in the ACCUM mode. Three additional minutes are considered for each change in wavelength, and 6 mn per additional orbit for re- acquisition. Real Time Justification ----------------------- There are optimum times in the year (typically a three month window) for obtaining Lyman-alpha observations toward white dwarfs. These times are when the velocity of the Earth is such that the geocoronal Lyman alpha emission (arising in the Earth atmosphere) is centered in the core of the \hi\ absorption profile, so that it may be easily isolated and removed. This strategy has been used for our Cycle 1 observations of G191-B2B (see fig.1) where the geocoronal emission is correctly centered but however almost affected the \la\ blue wing. For Cycle 5 observations we will locate the geocoronal emission further away from both \la\ wings to better avoid any contamination. Calibration Justification ------------------------- None. Additional Comments ------------------- ------------------------------------------------------------------------------------ 5893( 0) - 07/18/95 18:29 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5893( 0) - 07/18/95 18:29 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 G191-B2B STAR, DA RA = 05H 05M 30.62S +/- 0.02S, J2000 V=11.88 +/- 0.40 DEC = 52D 49' 54.0" +/- 0.2", B-V=-0.32 PLATE-ID = 0005 F(1199) = 13. +/- 3. E-12 F(1215) = 4. +/- 2. E-13 F(1304) = 10. +/- 2. E-12 Comments: Coordinates are from GSC 5893( 0) - 07/18/95 18:29 - [ 5] Visit: 01 Visit Requirements: BETWEEN 18-JUL-95 AND 7-SEP-95 On Hold Comments: Additional Comments: Dates to avoid geocorona Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 G191-B2B HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 9S ONBOARD ACQ FOR 11 SIZE=3,BRIGHT=R ETURN,LOCATE=YE S Comments: STEP-TIME=1S ------------------------------------------------------------------------------------------------------------------------------------ 11 G191-B2B HRS ACQ/PEA 0.25 MIRROR-N1 SEARCH-SIZE=5 1 25S ONBOARD ACQ FOR 12-19 KUP Comments: STEP-TIME=1S ------------------------------------------------------------------------------------------------------------------------------------ 12 WAVE HRS ACCUM SC2 ECH-A 1200.0 1 DEF Comments: WAVE CALIBRATION FOR 13 ------------------------------------------------------------------------------------------------------------------------------------ 13 G191-B2B HRS ACCUM 0.25 ECH-A 1200.0 FP- 9 544S SPLIT=STD,STEP- PATT=DEF,SPYBAL =NO Comments: N I ------------------------------------------------------------------------------------------------------------------------------------ 14 WAVE HRS ACCUM SC2 ECH-A 1303.0 1 DEF Comments: WAVE CALIBRATION FOR 15 ------------------------------------------------------------------------------------------------------------------------------------ 15 G191-B2B HRS ACCUM 0.25 ECH-A 1303.0 FP- 7 652.8S SPLIT=STD,STEP- PATT=DEF,SPYBAL =NO Comments: O I, Si II ------------------------------------------------------------------------------------------------------------------------------------ 16 G191-B2B HRS ACCUM 0.25 ECH-A 1203.72 FP- 6 652.8S SPLIT=STD,STEP- PATT=DEF Comments: N I , Si III ------------------------------------------------------------------------------------------------------------------------------------ 17 G191-B2B HRS ACCUM 0.25 G140M 1216.0 FP- 2 435.2S SPLIT=STD,STEP- PATT=DEF Comments: H I, D I ------------------------------------------------------------------------------------------------------------------------------------ 18 G191-B2B HRS ACCUM 0.25 G140M 1200.0 FP- 3 652.8S SPLIT=STD,STEP- PATT=DEF Comments: N I ------------------------------------------------------------------------------------------------------------------------------------ 5893( 0) - 07/18/95 18:29 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 19 G191-B2B HRS ACCUM 0.25 G140M 1216.0 FP- 1 544S SPLIT=STD,STEP- PATT=DEF Comments: H I, D I ------------------------------------------------------------------------------------------------------------------------------------ 5893( 0) - 07/18/95 18:29 - [ 7] Visit: 02 Visit Requirements: BETWEEN 18-JUL-95 AND 7-SEP-95 On Hold Comments: Additional Comments: Dates to avoid geocorona Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 36 G191-B2B HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 9S ONBOARD ACQ FOR 37 SIZE=3,BRIGHT=R ETURN,LOCATE=YE S Comments: STEP-TIME=1S ------------------------------------------------------------------------------------------------------------------------------------ 37 G191-B2B HRS ACQ/PEA 0.25 MIRROR-N1 SEARCH-SIZE=5 1 25S ONBOARD ACQ FOR 38-43 KUP Comments: STEP-TIME=1S ------------------------------------------------------------------------------------------------------------------------------------ 38 WAVE HRS ACCUM SC2 ECH-A 1215.6 1 DEF Comments: WAVE CALIBRATION FOR 39 ------------------------------------------------------------------------------------------------------------------------------------ 39 G191-B2B HRS ACCUM 0.25 ECH-A 1215.6 FP- 12 544S SPLIT=STD,STEP- PATT=DEF,SPYBAL =NO Comments: D I, H I ------------------------------------------------------------------------------------------------------------------------------------ 40 WAVE HRS ACCUM SC2 ECH-A 1215.6 1 DEF Comments: WAVE CALIBRATION FOR 41 ------------------------------------------------------------------------------------------------------------------------------------ 41 G191-B2B HRS ACCUM 0.25 ECH-A 1215.6 FP- 12 544S SPLIT=STD,STEP- PATT=DEF,SPYBAL =NO Comments: D I, H I ------------------------------------------------------------------------------------------------------------------------------------ 42 WAVE HRS ACCUM SC2 ECH-A 1215.6 1 DEF Comments: WAVE CALIBRATION FOR 43 ------------------------------------------------------------------------------------------------------------------------------------ 43 G191-B2B HRS ACCUM 0.25 ECH-A 1215.6 FP- 12 544S SPLIT=STD,STEP- PATT=DEF,SPYBAL =NO Comments: D I, H I ------------------------------------------------------------------------------------------------------------------------------------ 5893( 0) - 07/18/95 18:29 - [ 8] Summary Form for Proposal 5893 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN LOCATE=YES SEARCH-SIZE=5 SPYBAL=NO STEP-PATT=DEF FP-SPLIT=STD ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Interstellar Medium ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 18-JUL-95 AND 7-SEP-95 ONBOARD ACQ FOR 11 ONBOARD ACQ FOR 12-19 ONBOARD ACQ FOR 37 ONBOARD ACQ FOR 38-43 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N1 ECH-A G140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names G191-B2B WAVE ------------------------------------------------------------------------------------------------------------------------------------