! Proposal 6418, submission 1 ! PI: David M. Meyer ! Received Thu Jan 25 11:05:02 EST 1996 ! From: hrsmeyer@hrssun.gsfc.nasa.gov ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Alice Berman ! Phone: 410-338-4462 , E-mail: aberman@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Proposal_Information ! Section 4 Title: Small-Scale ISM Structure: The Remarkable Sightline Toward Mu Cru Proposal_Category: GO Scientific_Category: INTERSTELLAR MEDIUM Cycle: 6 Investigators PI_name: David M. Meyer PI_Institution: Northwestern University CoI_Name: J. Chris Blades CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to use the GHRS on HST to accurately measure and compare the interstellar Zn II, Cr II, Mg I, and C I absorption line profiles toward both members of the binary Mu Cru. Recent optical observations of Na I at very high spectral resolution (Deltav = 0.3 km s^-1) toward this system reveal line strength variations in at least 4 velocity components indicative of ISM structure on scales less than the projected binary separation of 6600 AU. Based on similar observations toward other binaries, such structure now appears to be a common feature of the cold diffuse gas in the local ISM and detectable toward systems with projected separations as small as 1000 AU. The Mu Cru sightline provides an ideal laboratory to study the nature of this small-scale ISM structure with high S/N GHRS echelle observations of key interstellar ions. In particular, comparisons between the optically thin Zn II and Cr II lines will allow us to assess how the clumpiness of the gas is reflected in the dust. Observations of the C I fine -structure excitation will provide good estimates of the pressures in the cold clumps whose small scale lengths suggest high gas densities in a very diffuse ambient medium. In summary, our proposed GHRS observations of Mu Cru will provide the first quantitative steps toward understanding how small- scale structure forms and evolves in the diffuse ISM. Questions ! Free format text (please update) Observing_Description: Our goal is to obtain high S/N GHRS echelle observations of the interstellar Zn II, Cr II, Mg I, and C I absorption line profiles toward both members of the binary Mu Cru. All observations will be made using the SSA and a sampling strategy of four substeps per diode in order to maximize the spectral resolution needed for good profile comparisons. The observations of Zn II LambdaLambda2026.14, 2062.66, Cr II LambdaLambda2062.23, 2066.16, and Mg I LambdaLambda2026.48, 2852.96 will involve three ECH-B wavelength setups per star. Based on the IUE fluxes for Mu Cru and accounting for the effects of the ECH-B blaze efficiency as well as the reduced SSA throughput on the sensitivities listed in the Cycle 6 GHRS Handbook, we can achieve spectra of all of these lines at a S/N ratio of 150 in a total integration time of 39 min. (3 exposures) on Mu^1 Cru and 160 min. (9 exposures) on Mu^2 Cru. We plan to use the FP-Split option in all of our exposures in order to better assess and remove the effects of fixed pattern noise. In the case of C I, the multiplets centered near 1277 and 1280 Angstrom\ can both be covered with one ECH-A wavelength setup per star. Since the oscillator strengths and wavelength separations of the various J = 0, 1, 2 transitions in these multiplets are quite different, it will be possible to make an accurate comparison of the C I fine-structure excitation as a function of velocity in the Mu Cru line profiles. We can obtain a C I spectrum with a S/N ratio of 150 toward Mu^1 Cru in a total integration time of 19 min. (1 exposure) and one with a S/N ratio of 100 toward Mu^2 Cru in a time of 64 min. (4 exposures). The C I sensitivity goal is somewhat lower for Mu^2 Cru because this star is appreciably fainter in the far- UV and the key component (-9 km s^-1) to be studied is in the Mu^1 Cru sightline. Allowing for all of the acquisition and exposure overheads (including the 45 min. GHRS side change from ECH-A to ECH-B which can occur mostly during occultation), our proposed observations will require 2 orbits on Mu^1 Cru and 6 orbits on Mu^2 Cru given a visibility window of 57 min. per orbit. Real_Time_Justification: None. None. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: HD112092 Alternate_Names: mu1-cru Description: STAR, B0-B2 V-IV Position: RA=12H 54M 35.64S +/- 0.03S, DEC=-57D 10' 39.8" +/- 0.5" Equinox: J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=4.03, B-V=-0.17 Comments: Target_Number: 2 Target_Name: HD112091 Alternate_Names: mu2-cru Description: STAR, BE Position: RA=12H 54M 36.91S +/- 0.03S, DEC=-57D 10' 06.7" +/- 0.5" Equinox: J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=5.17, B-V=-0.12 Comments: ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 1 ! Section 6.5 Target_Name: HD112092 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N1 Wavelength: Optional_Parameters: BRIGHT=RETURN,SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 1.8S Special_Requirements: ONBOARD ACQ FOR 2 ! Section 7.2 Comments: Exposure_Number: 2 ! Section 6.5 Target_Name: HD112092 Config: HRS Opmode: ACQ/PEAKUP Aperture: 0.25 Sp_Element: MIRROR-N1 Wavelength: Optional_Parameters: SEARCH-SIZE=5 Number_of_Iterations: 1 Time_Per_Exposure: 5.0S Special_Requirements: ONBOARD ACQ FOR 3-6 ! Section 7.2 Comments: Exposure_Number: 3 ! Section 6.5 Target_Name: HD112092 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-A44 Wavelength: 1278.7 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 2 Time_Per_Exposure: 544.0S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 4 ! Section 6.5 Target_Name: HD112092 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-B28 Wavelength: 2026.0 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 4 Time_Per_Exposure: 652.8S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 5 ! Section 6.5 Target_Name: HD112092 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-B27 Wavelength: 2063.0 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 3 Time_Per_Exposure: 544.0S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 6 ! Section 6.5 Target_Name: HD112092 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-B20 Wavelength: 2853.0 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 2 Time_Per_Exposure: 435.2S Special_Requirements: ! Section 7.2 Comments: Visit_Number: 2 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Visit_Comments: Exposure_Number: 7 ! Section 6.5 Target_Name: HD112091 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N1 Wavelength: Optional_Parameters: BRIGHT=RETURN,SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 1.8S Special_Requirements: ONBOARD ACQ FOR 8 ! Section 7.2 Comments: Exposure_Number: 8 ! Section 6.5 Target_Name: HD112091 Config: HRS Opmode: ACQ/PEAKUP Aperture: 0.25 Sp_Element: MIRROR-N1 Wavelength: Optional_Parameters: SEARCH-SIZE=5 Number_of_Iterations: 1 Time_Per_Exposure: 5.0S Special_Requirements: ONBOARD ACQ FOR 9-12 ! Section 7.2 Comments: Exposure_Number: 9 ! Section 6.5 Target_Name: HD112091 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-A44 Wavelength: 1278.7 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 4 Time_Per_Exposure: 979.2S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 10 ! Section 6.5 Target_Name: HD112091 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-B28 Wavelength: 2026.0 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 4 Time_Per_Exposure: 870.4S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 11 ! Section 6.5 Target_Name: HD112091 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-B27 Wavelength: 2063.0 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 3 Time_Per_Exposure: 870.4S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 12 ! Section 6.5 Target_Name: HD112091 Config: HRS Opmode: ACCUM Aperture: 0.25 Sp_Element: ECH-B20 Wavelength: 2853.0 Optional_Parameters: FP-SPLIT=STD,STEP-PATT=7 Number_of_Iterations: 2 Time_Per_Exposure: 979.2S Special_Requirements: ! Section 7.2 Comments: Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 ! 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