! Proposal 6154, submission 1
! PI: Blair Savage
! Received Tue Mar 14 12:06:39 EST 1995
! From: sembach@sundoggie.mit.edu
Proposal_Information                         
              Title:  High-Resolution Observations of Highly Ionized Gas
                      Toward the Halo Star HD 119608
  Proposal_Category:  GTO/HRS
Scientific_Category:  Interstellar Medium
             Cycle:    5

Investigators
     PI_name:         Blair Savage
     PI_Institution:  University of Wisconsin-Madison

          CoI_Name:   Kenneth Sembach
   CoI_Institution:   Massachusetts Institute of Technology
           Contact:   Y         

          CoI_Name:   Limin Lu
   CoI_Institution:   California Institute of Technology
           Contact:   N        

          CoI_Name:   The GHRS Team
   CoI_Institution:   Many Institutions
           Contact:   N        

Abstract:                        
We will use the echelle mode of the GHRS to obtain high-resolution,
high S/N (40-50:1) absorption line observations of the Si IV, C IV, and N V 
lines toward HD 119608, a halo star at 4.4 kpc in the direction l = 320, 
b = +43.  We will compare the fully resolved high ion profiles to determine 
which ionization mechanisms give rise to highly ionized gas in the Galactic 
halo in this direction.  In particular, we will search for 1) the narrow 
structured absorption associated with interface phenomena that gives rise to 
the ubiquitous N(C IV)/N(Si IV) ~ 3.5 ratio in the Galaxy and 2) a more highly 
ionized (and presumably hotter) type of gas that we have detected toward the 
inner Galaxy HD 167756 sight line.  The relative fractions of the gas describe
in (1) and (2) have implications for the thermal stability, filling fraction of
hot gas, and energetics in the Galactic halo.

Questions                       

     Observing_Description:
We will use the Ech-A grating of the GHRS to provide 3.5 km/sec (FWHM)
resolution spectra of the interstellar Si IV 1393, C IV 1548,1550, and 
N V 1238,1240 lines in the spectrum of HD 119608.  All observations will
be obtained in the large science aperture.  FP-SPLIT=4, COMB=4, and 
STEP-PATT=7 will be used.  We expect S/N = 45, 42, and 50 for Si IV,
C IV, and N V, respectively.  These S/N values are 1/2 diode values.  Since
we are quarter stepping, we will bin the data by two pixels (without 
loss of resolution).

   Real_Time_Justification:
    No special scheduling requirements are necessary.

Calibration_Justification:           
    No special scheduling requirements are necessary.  

      Additional_Comments:
    No additional comments at this time.

Fixed_Targets  

! Target coordinates updated 6/12/95 - AFB

  Target_Number: 1
    Target_Name: HD119608
Alternate_Names: BD-17D3918, GSC6127-00863
    Description: STAR, B0-B2 III-I
       Position: RA = 13H 44M 31.29S +/- 0.01S,
                 DEC = -17D 56' 13.5" +/- 0.2"
        Equinox: J2000
        RV_or_Z: V = +25
          RA_PM: -0.001                        
         Dec_PM:  0.005                       
          Epoch: 2000.000   
Annual_Parallax: 
           Flux: V = 7.50,    
                 B-V = -0.07 +/- 0.05,
                 F-CONT(1240) = 1.8 +/- 0.2 E-11,
                 F-CONT(1550) = 2.3 +/- 0.2 E-11,
       Comments: Coordinates, flux are from Hipparcos INCA

! Original values:
!       Position:  RA=13H 41M 48.2S +/- 0.05S, 
!                  DEC=-17D 41' 10.8" +/- 0.5"
!        Equinox:  1950
!           Flux:  V = 7.57 +/- 0.10,

Visits   
!Visit Number 1                               
      Visit_Number:  1
Visit_Requirements:                     
  On_Hold_Comments:
    Visit_Comments:  Number exposures beginning with 10.

!Line 1
     Exposure_Number: 10
         Target_Name: HD119608
              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 20-40
            Comments: Expect about 50,000 cnt/s using mirror N1.
                      STEP-TIME = 0.2 seconds.  Ok as long as
                      BRIGHT=RETURN is used.

!Line 2
     Exposure_Number: 20
         Target_Name: HD119608
              Config: HRS
              Opmode: ACCUM
            Aperture: 2.0
          Sp_Element: ECH-A
          Wavelength: 1240.9
 Optional_Parameters: FP-SPLIT=FOUR, COMB=FOUR, STEP-PATT=7, DOPPLER=ON
Number_of_Iterations: 2
   Time_Per_Exposure: 979.2S  !(S/N=40 @ 20.1M)
Special_Requirements: 
            Comments: Lines = N V, Mg II

!Line 3
     Exposure_Number: 30
         Target_Name: HD119608
              Config: HRS
              Opmode: ACCUM
            Aperture: 2.0
          Sp_Element: ECH-A
          Wavelength: 1391.8
 Optional_Parameters: FP-SPLIT=FOUR, COMB=FOUR, STEP-PATT=7, DOPPLER=ON
Number_of_Iterations: 4                          ! Changed 6/28/95
   Time_Per_Exposure: 870.4S  !(S/N=40 @ 40.1M)  
Special_Requirements: 
            Comments: Lines = Si IV

!Line 4
     Exposure_Number: 40
         Target_Name: HD119608
              Config: HRS
              Opmode: ACCUM
            Aperture: 2.0
          Sp_Element: ECH-A
          Wavelength: 1548.9
 Optional_Parameters: FP-SPLIT=FOUR, COMB=FOUR, STEP-PATT=7, DOPPLER=ON
Number_of_Iterations: 5
   Time_Per_Exposure: 1414.4S  !(S/N=40 @ 103.9M)
Special_Requirements: 
            Comments: Lines = C IV


Data_Distribution                       

         Medium:        8MM             
Blocking_Factor:        10 

        Ship_To:        Kenneth Sembach
                        Center for Space Research
                        MIT 6-216
                        77 Massachusetts Avenue
                        Cambridge, MA  02139

       Ship_Via:        UPS            

Recipient_Email:        sembach@sundoggie.mit.edu