6800( 7) - 10/25/96 13:29 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6800 Version: 7 Check-in Date: 25-Oct-1996 13:25:06 1.Proposal Title: Deuterium in the local interstellar medium towards hot stars ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle INTERSTELLAR MEDIUM GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Alfred Vidal-Madjar INSTITUT D'ASTROPHYSIQUE DE PARIS CoI: John Webb University of New South Wales N CoI: Don York University of Chicago N CoI: Jean Audouze Institut d'Astrophysique de Paris N CoI: Michel Casse Institut d'Astrophysique de Paris N CoI: Roger Ferlet Institut d'Astrophysique de Paris N CoI: Scott Friedman Johns Hopkins University N CoI: Cecile Gry Laboratoire d'Astronomie Spatiale de N Marseille CoI: Detlev Koester Universitaet Kiel N CoI: Martin Lemoine Institut d'Astrophysique de Paris N CoI: Warren Moos Johns Hopkins University N CoI: George Sonneborn Goddard Space Flight Center N CoI: Elisabeth Vangioni-Flam Institut d'Astrophysique de Paris N ------------------------------------------------------------------------------------ 6. Abstract The proposed observations are the necessary continuation of previous approved proposals aiming at deriving the deuterium abundance in the local interstellar medium toward nearby hot stars. This estimate is of prime importance for the determination of the present D abundance within the Galaxy, one of the key-parameter of galactic evolution models. From Cycle 1 observations, we proved the efficiency of using nearby hot stars as targets. The data, in particular in the direction of G191- B2B (Lemoine et al., 1995), also have demonstrated the extreme importance of observing, beside the HI and DI lines, the spectral region around the NI triplet. Very new observations just obtained (ID 5893) with GHRS ECH-A at the highest resolution constrain more tightly the evaluated D/H ratio. A significant variation (factor ~3) of the D/H ratio from one component to the other is strongly infered toward G191-B2B. Although being a long lasting question, such a variability -- if true -- needs to be confirmed and understood to be able to estimate the really representative present day deuterium abundance, which may very well be different from the precise measurement in the direction of Capella (Linsky et al., 1993). This motivates the present proposal aimed to derive D/H toward another white dwarf and its companion star for which the velocity structure is already rather well known: Sirius A and B. ------------------------------------------------------------------------------------ Observations Description ------------------------ We plan to observe Sirius-A and its white dwarf companion with ECH-A, at the highest possible S/N within the number of selected orbits. We plan to observe with ECH-A the NI triplet at 1200Angstrom\\ , the SiIII line at 1206Angstrom\\ , the \\ly\\ HI and DI lines, the OI 1302Angstrom\\ and SiII 1304Angstrom\\ lines and the CII 1332Angstrom\\ line. All these observations should constrain very precisely the line of sight structure and give us first indications about the possible cause of the \\dsh\\ variations. Also two G160M settings, centered at 1203.5Angstrom\\ and at 1316Angstrom\\ will be made to have a precise evaluation of the zero flux level since this information is not easilly accessible from ECH-A spectra alone (see the incorect zero in Figure 1). Information from ECH-B spectra is already available. These observations should perfectly complement our original HST observations and allow us to evaluate precisely the \\dsh\\ ratio in these lines of sights., We are aware from our Cycle 1 observations (and others) of some of the difficulties involved in such observations (granularities of the photocathode, importance of frequent calibrations, sampling of the spectrum in 1/4 diode steps). As well, we estimated the scattered light due to Sirius-A when observing Sirius-B to be of minor importance. In effect, using the SSA, the separation between both stars being more than 3 arcsec in 1996, the ratio of the fluxes F(Sirius-A)/F(Sirius- B) in the spectrograph is much less than 7. 10^-5 times the ratio of the fluxes F(Sirius- A)/F(Sirius-B) in front of the entrance slit, as given by the spatial Post-Costar PSF. Due to the spectral types of both stars, this latter ratio is higher the longer the wavelength, and is only ~100 at 2800Angstrom, which is the far longer than we consider here. Therefore, the contamination by Sirius -A should represent much less than 7. 10^-3 times the signal of Sirius-B, which is clearly negligible. The strong flux of Sirius-B at \\ly\\ allows us to have short exposure times while keeping a high signal-to-noise ratio (S/N ~\\ 40 per diode) at the bottom of the \\ly\\ line, about as well as at the continuum of other observed lines. We obtained flux at each chosen wavelength for Sirius-B from theoretical calculations, as well as from the IUE spectra (Wegner &\\ Swanson, 1991). We converted these fluxes into counts using the sensitivity tables of the instrument and, where appropriate the Ripple function, given in the Post- Costar GHRS Instrument Handbook. These counts were calibrated to the use of the SSA, whose throughput is 2/3 that of the LSA. As an example, the flux at the bottom of the \\ly\\ line (1215.67Angstrom) toward Sirius-B is 2. 10^-12 erg.cm^-2.s^- 1.ang^-1. Taken the sensitivity of the ECH-A (order 46) at this wavelength using the SSA, the count rate is therefore sim 0.1 c.s^-1.d^-1, which gives a signal-to-noise ratio S/N ~ 20 per diode in 4000 s. Taking into account the several count rates at 1200Angstrom\\ (Sirius A, 3.0 c.s^-1.d^-1, Sirius B, 0.72 c.s^-1.d^-1), at 1216Angstrom\\ (Sirius A, 0.56 c.s^-1.d^-1, Sirius B, 0.1 c.s^-1.d^-1), at 1302Angstrom\\ (Sirius A, 380.0 c.s^-1.d^-1, Sirius B, 8.4 c.s^-1.d^-1), and the nearby wavelength, shows that all the requested exposures translate into 8 orbits including overheads. Real Time Justification ----------------------- There are optimum times in the year (typically a three month window) for obtaining \\ly\\ observations toward white dwarfs. These times are when the velocity of the Earth is such that the geocoronal \\ly\\ 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 without affecting the \\di\\ absorption. This strategy has been successfully used for our previous observations of G191-B2B. We will need an accurate acquisition of Sirius-B, due to the presence of Sirius-A, whose flux can be as high as 10 times the flux of Sirius-B at the wavelengths we consider. We estimate this contamination to be negligible if Sirius-B is well centered on the entrance slit. Calibration Justification ------------------------- Additional Comments ------------------- The position of Sirius-B is calculated relative to the Sirius-A one. There are two relatively short observing windows centered on September 10, 1996 and on November 5, 1996. The RA and DEC offsets given correspond to the September 10 centered window. Here are the calculated RA and DEC for the two possible windows: Window centered on September 10, 1996, Sirius-B position should be RA = 06H 45M 08.796S +/- 0.03", DEC = -16D 43' 01.49" +/- 0.04" Window centered on November 5, 1996, Sirius-B position should be RA = 06H 45M 08.806S +/- 0.03", DEC = -16D 43' 01.57" +/- 0.04" Note that the RPS2 calculation produces a slightly different estimation of the declination. The RA and DEC given are from the Hipparcos catalogue. The RPS2 software does not accept an Epoch later than 1996.1, although it seems that the Epoch of the catalogue seems to be 2000. This is why the value 1996 was arbitrarily put in, since I was unable to figure out to what evaluation of the Epoch I should refer, corresponding to the used catalogue, some information leading to 1990, and others to year 2000. ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6800( 7) - 10/25/96 13:29 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD48915 STAR, A0-A3 V-IV RA = 06H 45M 08.88S +/- 0.03", J2000 V = -7.6 V = -1.45+/-0.01 DEC = -16D 42' 56.9" +/- 0.04" B-V = 0.009 F(1199)=5.+/-1.e-11 F(1206)=2.5+/-1.e-11 F(1215)=1.+/-0.5e-11 F(1302)=5.+/-1.e-09 F(1334)=1.+/-1.e-09 Comments: Binary at 3.69", V=8.9. THE COORDINATES ARE FROM HIPPARCOS CATALOGUE. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.038 -1.205 0.374 2 SIRIUS-B STAR, DA RA-OFF = -0.0753S +/- 0.006S, J2000 V = -3 V = 8.9+/-0.2 DEC-OFF = -3.50" +/- 0.045", B-V = -0.12 FROM 1 F(1199)=2.6+/-0.5e-11 F(1206)=1.7+/-0.5e-11 F(1215)=2.5+/-1.e-12 F(1302)=1.2+/-1.e-10 F(1334)=1.2+/-1.e-10 Comments: ON SEPT 10, POSITION ANGLE=197.19 DEG, OFFSET FROM SIRIUS-A IS 3.67 ARCSEC. GIVEN POSITIONS CORRESPOND TO SEPT 10. SHOULD BE APPLIED TO FIRST OBSERVING WINDOW. ON NOV 5, POSITION ANGLE=194.52 DEG, OFFSET FROM SIRIUS-A IS 3.70 ARCSEC. FOR THE SECOND OBSERVING WINDOW, POSITIONS ARE: RA-OFF = -0.0646S, DEC-OFF = - 3.58". 3 SIRIUS-B-51 STAR, DA RA-OFF = -0.0620S +/- 0.006S, J2000 V = -3 V = 8.9+/-0.2 DEC-OFF = -3.60" +/- 0.045", B-V = -0.12 FROM 1 F(1199)=2.6+/-0.5e-11 F(1206)=1.7+/-0.5e-11 F(1215)=2.5+/-1.e-12 F(1302)=1.2+/-1.e-10 F(1334)=1.2+/-1.e-10 Comments: New offset calculated for repeat visit 51 for 11/18/96 timeframe 6800( 7) - 10/25/96 13:29 - [ 2] Visit: 01 Visit Requirements: BETWEEN 31-AUG-96 AND 26-SEP-96 On Hold Comments: Additional Comments: Dates to avoid geocorona. Second choice is between 10/26-11/21/96. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 9 HD48915 HRS ACQ 2.0 MIRROR-A1 SEARCH-SIZE=3,BRIGHT=RETURN, 1 1.8 S ONBOARD ACQ FOR 10 LOCATE=YES Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 10 HD48915 HRS ACQ/PEA 0.25 MIRROR-A1 SEARCH-SIZE=5 1 5 S ONBOARD ACQ FOR 11 KUP Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 11 HD48915 HRS ACQ/PEA 0.25 MIRROR-A1 SEARCH-SIZE=5 1 5 S ONBOARD ACQ FOR 12-42 KUP Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 12 WAVE HRS ACCUM SC2 ECH-A 1204.75 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 13 ------------------------------------------------------------------------------------------------------------------------------------ 13 HD48915 HRS ACCUM 0.25 ECH-A 1204.75 FP-SPLIT=STD,STEP-PATT=DEF, 2 435.2 S SPYBAL=NO Comments: Si III ------------------------------------------------------------------------------------------------------------------------------------ 15 WAVE HRS ACCUM SC2 ECH-A 1199.5 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 16 ------------------------------------------------------------------------------------------------------------------------------------ 16 HD48915 HRS ACCUM 0.25 ECH-A 1199.5 FP-SPLIT=STD,STEP-PATT=DEF, 3 435.2 S SPYBAL=NO Comments: N I ------------------------------------------------------------------------------------------------------------------------------------ 18 WAVE HRS ACCUM SC2 ECH-A 1302.0 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 19 ------------------------------------------------------------------------------------------------------------------------------------ 19 HD48915 HRS ACCUM 0.25 ECH-A 1302.0 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: O I, Si II ------------------------------------------------------------------------------------------------------------------------------------ 21 WAVE HRS ACCUM SC2 ECH-A 1335.0 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 22 ------------------------------------------------------------------------------------------------------------------------------------ 22 HD48915 HRS ACCUM 0.25 ECH-A 1335.0 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: C II, C II* ------------------------------------------------------------------------------------------------------------------------------------ 24 WAVE HRS ACCUM SC2 ECH-A 1215.6 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 25 ------------------------------------------------------------------------------------------------------------------------------------ 25 HD48915 HRS ACCUM 0.25 ECH-A 1215.6 FP-SPLIT=STD,STEP-PATT=DEF, 7 435.2 S SPYBAL=NO Comments: H I, D I ------------------------------------------------------------------------------------------------------------------------------------ 6800( 7) - 10/25/96 13:29 - [ 3] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 28 HD48915 HRS ACCUM 0.25 G140M 1204.0 FP-SPLIT=STD,STEP-PATT=DEF 3 544.0 S Comments: HI, DI ------------------------------------------------------------------------------------------------------------------------------------ 31 HD48915 HRS ACCUM 0.25 G140M 1293.0 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: OI, SiII ------------------------------------------------------------------------------------------------------------------------------------ 34 HD48915 HRS ACCUM 0.25 G140M 1322.5 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: CII, CII* ------------------------------------------------------------------------------------------------------------------------------------ 42 SIRIUS-B HRS ACQ/PEA 0.25 MIRROR-N1 SEARCH-SIZE=5 1 15 S ONBOARD ACQ FOR 44-48 KUP Comments: STEP-TIME=0.6S, EXPECTED COUNT RATE=16500 S-1 ------------------------------------------------------------------------------------------------------------------------------------ 44 WAVE HRS ACCUM SC2 ECH-A 1215.6 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 45 ------------------------------------------------------------------------------------------------------------------------------------ 45 SIRIUS-B HRS ACCUM 0.25 ECH-A 1215.6 FP-SPLIT=STD,STEP-PATT=DEF, 8 435.2 S SPYBAL=NO Comments: H I, D I ------------------------------------------------------------------------------------------------------------------------------------ 47 WAVE HRS ACCUM SC2 ECH-A 1199.5 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 48 ------------------------------------------------------------------------------------------------------------------------------------ 48 SIRIUS-B HRS ACCUM 0.25 ECH-A 1199.5 FP-SPLIT=STD,STEP-PATT=DEF, 5 435.2 S SPYBAL=NO Comments: N I ------------------------------------------------------------------------------------------------------------------------------------ 6800( 7) - 10/25/96 13:29 - [ 4] Visit: 51 Visit Requirements: On Hold Comments: Additional Comments: HOPR repeat of Visit 1 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 9 HD48915 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=5,BRIGHT=RETURN, 1 5.0 S ONBOARD ACQ FOR 10 LOCATE=YES Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 10 HD48915 HRS ACQ/PEA 0.25 MIRROR-A2 SEARCH-SIZE=5 1 5 S ONBOARD ACQ FOR 15-42 KUP Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 15 WAVE HRS ACCUM SC2 ECH-A 1199.5 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 16 ------------------------------------------------------------------------------------------------------------------------------------ 16 HD48915 HRS ACCUM 0.25 ECH-A 1199.5 FP-SPLIT=STD,STEP-PATT=DEF, 3 435.2 S SPYBAL=NO Comments: N I ------------------------------------------------------------------------------------------------------------------------------------ 17 WAVE HRS ACCUM SC2 ECH-A 1204.75 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 18 ------------------------------------------------------------------------------------------------------------------------------------ 18 HD48915 HRS ACCUM 0.25 ECH-A 1204.75 FP-SPLIT=STD,STEP-PATT=DEF, 2 435.2 S SPYBAL=NO Comments: Si III ------------------------------------------------------------------------------------------------------------------------------------ 20 HD48915 HRS ACCUM 0.25 ECH-A 1302.0 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: O I, Si II ------------------------------------------------------------------------------------------------------------------------------------ 22 HD48915 HRS ACCUM 0.25 ECH-A 1335.0 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: C II, C II* ------------------------------------------------------------------------------------------------------------------------------------ 24 WAVE HRS ACCUM SC2 ECH-A 1215.6 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 25-26 ------------------------------------------------------------------------------------------------------------------------------------ 25 HD48915 HRS ACCUM 0.25 ECH-A 1215.6 FP-SPLIT=STD,STEP-PATT=DEF, 3 435.2 S SPYBAL=NO Comments: H I, D I ------------------------------------------------------------------------------------------------------------------------------------ 26 HD48915 HRS ACCUM 0.25 ECH-A 1215.6 FP-SPLIT=STD,STEP-PATT=DEF, 4 435.2 S SPYBAL=NO Comments: H I, D I ------------------------------------------------------------------------------------------------------------------------------------ 32 HD48915 HRS ACCUM 0.25 G140M 1204.0 FP-SPLIT=STD,STEP-PATT=DEF 3 544.0 S Comments: HI, DI ------------------------------------------------------------------------------------------------------------------------------------ 33 HD48915 HRS ACCUM 0.25 G140M 1293.0 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: OI, SiII ------------------------------------------------------------------------------------------------------------------------------------ 6800( 7) - 10/25/96 13:29 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 34 HD48915 HRS ACCUM 0.25 G140M 1322.5 FP-SPLIT=STD,STEP-PATT=DEF 2 108.8 S Comments: CII, CII* ------------------------------------------------------------------------------------------------------------------------------------ 42 SIRIUS-B-51 HRS ACQ/PEA 0.25 MIRROR-N1 SEARCH-SIZE=5 1 15 S ONBOARD ACQ FOR 43 KUP Comments: STEP-TIME=0.6S, EXPECTED COUNT RATE=16500 S-1 ------------------------------------------------------------------------------------------------------------------------------------ 43 SIRIUS-B-51 HRS ACQ/PEA 0.25 MIRROR-N1 SEARCH-SIZE=5 1 15 S ONBOARD ACQ FOR 44-48 KUP Comments: STEP-TIME=0.6S, EXPECTED COUNT RATE=16500 S-1 ------------------------------------------------------------------------------------------------------------------------------------ 44 WAVE HRS ACCUM SC2 ECH-A 1215.6 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 45 ------------------------------------------------------------------------------------------------------------------------------------ 45 SIRIUS-B-51 HRS ACCUM 0.25 ECH-A 1215.6 FP-SPLIT=STD,STEP-PATT=DEF, 8 435.2 S SPYBAL=NO Comments: H I, D I ------------------------------------------------------------------------------------------------------------------------------------ 47 WAVE HRS ACCUM SC2 ECH-A 1199.5 SPYBAL=YES 1 DEF Comments: WAVE CALIBRATION FOR 48 ------------------------------------------------------------------------------------------------------------------------------------ 48 SIRIUS-B-51 HRS ACCUM 0.25 ECH-A 1199.5 FP-SPLIT=STD,STEP-PATT=DEF, 5 435.2 S SPYBAL=NO Comments: N I ------------------------------------------------------------------------------------------------------------------------------------ 6800( 7) - 10/25/96 13:29 - [ 6] Summary Form for Proposal 6800 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=YES SPYBAL=NO STEP-PATT=DEF FP-SPLIT=STD ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 31-AUG-96 AND 26-SEP-96 ONBOARD ACQ FOR 10 ONBOARD ACQ FOR 11 ONBOARD ACQ FOR 12-42 ONBOARD ACQ FOR 44-48 ONBOARD ACQ FOR 15-42 ONBOARD ACQ FOR 43 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-A1 ECH-A G140M MIRROR-N1 MIRROR-A2 ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD48915 WAVE SIRIUS-B SIRIUS-B-51 ------------------------------------------------------------------------------------------------------------------------------------