Proposal_Information

              Title: THE ULTRAVIOLET SPECTRUM OF THE CRAB PULSAR
  Proposal_Category: GTO/HSP
Scientific_Category: HOT STARS,NEUTRON STARS
              Cycle: 5


Investigators

        PI_name: ROBERT BLESS
 PI_Institution: UNIVERSITY OF WISCONSIN
       CoI_Name: EDWARD L. ROBINSON
CoI_Institution: UNIVERSITY OF TEXAS
        Contact: Y


Questions

   Observing_Description:  We will measure the time-averaged ultraviolet spectrum of
                           the Crab pulsar with the Faint Object Spectrograph in the
                           ACCUM mode using the BLUE detector and the G160L grating.
                           This grating and detector combination covers from 1150 A
                           to 2510 A with a dispersion of 6.87 A/diode.  The 0.3 arcsec
                           aperture will be used in order to exclude as much of the
                           surrounding nebula as possible.  The time averaged fluxes 
                           from the Crab pulsar should be F(2000.0) = 3.7 +/- 1.0 E-16
                           and F(1300.0) = 1.0 +/- 1.0 E-16 erg/cm^2/sec/A.  Using 
                           Figure 1.2.3 in Version 5.0 of the FOS Instrument Handbook,
                           we estimate that the pulsar will give a signal of
                           0.036 counts/sec/diode at 2000 A and 0.004 counts/sec/diode
                           at 1300 A.  We will integrate the Crab spectrum for
                           15,000 seconds and expect to detect ~550 counts/diode at
                           2000 A and 60 counts/diode at 1300 A.

   Real_Time_Justification:

   Calibration_Justification:

   Additional_Comments: The Crab pulsar is in the Crab nebula.


Abstract:               The time-averaged ultraviolet spectrum of the Crab pulsar will be
                        measured with the FOS using the G160L grating in the ACCUM mode.
                        The grating covers from 1150 A to 2510 A at a dispersion of
                        6.87 A/diode.  The 0.3 arcsec diameter aperture will be used in
                        order to exclude as much as possible of the surrounding nebula.
                        The observed spectrum will be corrected for interstellar extinction;
                        It will be necessary to investigate whether a standard interstellar
                        extinction curve is appropriate for the pulsar.  The expected results
                        are: 1) A measurement of the ultraviolet spectrum from the Crab pulsar.
                        2) A measurement of the interstellar extinction to the Crab pulsar,
                        and a measurement of -- or a limit on -- any difference between the
                        extinction of the pulsar and the extinction of the surrounding nebula.
                        This will allow some estimates of the internal extinction in the nebula.
                        3) A measurement of the de-extincted ultraviolet spectrum from the
                        pulsar and thus a measurement of the slope of the spectrum.


Fixed_Targets

  Target_Number: 1
    Target_Name: PSR0531+21
Alternate_Names: CRAB-PULSAR
    Description: STAR,PULSAR,
       Position: RA=5H 34M 31.973S +/- 0.005S,
                 DEC= 22D 0' 52.06" +/-  0.06"
        Equinox: J2000
          RA_PM: 0.0
         Dec_PM: 0.0
Annual_Parallax: 0.0
           Flux: V = 16.75 +/- 0.2,
                 F(2000.0) = 3.7 +/- 1.0 E-16,
                 F(1300.0) = 1.0 +/- 1.0 E-16


Visits

      Visit_Number: 1

     Exposure_number: 10
         Target_Name: PSR0531+21
              Config: FOS/BL
              Opmode: ACQ/PEAK
            Aperture: 4.3
          Sp_Element: MIRROR
 Optional_Parameters: SEARCH-SIZE-Y=3,
                      SEARCH-SIZE-X=1,
                      SCAN-STEP-Y=1.204
Number_of_iterations: 1
   Time_Per_Exposure: 2.5S
Special_Requirements: ONBOARD ACQ FOR 20
            Comments: PULSAR IS IN THE CRAB NEBULA. BACKGROUND FLUCTUATIONS EXPECTED.

     Exposure_number: 20
         Target_Name: PSR0531+21
              Config: FOS/BL
              Opmode: ACQ/PEAK
            Aperture: 1.0
          Sp_Element: MIRROR
 Optional_Parameters: SEARCH-SIZE-Y=2,
                      SEARCH-SIZE-X=6,
                      SCAN-STEP-Y=0.602,
                      SCAN-STEP-X=0.602
Number_of_iterations: 1
   Time_Per_Exposure: 2.5S
Special_Requirements: ONBOARD ACQ FOR 30

     Exposure_number: 30
         Target_Name: PSR0531+21
              Config: FOS/BL
              Opmode: ACQ/PEAK
            Aperture: 0.5-PAIR
          Sp_Element: MIRROR
 Optional_Parameters: SEARCH-SIZE-Y=3
                      SEARCH-SIZE-X=3
                      SCAN-STEP-Y=0.29
                      SCAN-STEP-X=0.29
Number_of_iterations: 1
   Time_Per_Exposure: 2.5S
Special_Requirements: ONBOARD ACQ FOR 40

     Exposure_number: 40
         Target_Name: PSR0531+21
              Config: FOS/BL
              Opmode: ACQ/PEAK
            Aperture: 0.25-PAIR
          Sp_Element: MIRROR
 Optional_Parameters: SEARCH-SIZE-Y=5,
                      SEARCH-SIZE-X=5,
                      SCAN-STEP-Y=0.052
                      SCAN-STEP-X=0.052
Number_of_iterations: 1
   Time_Per_Exposure: 25S
Special_Requirements: ONBOARD ACQ FOR 50
            Comments: CRITICAL ACQ/PEAK STAGE. EXPOSURE TO PRODUCE 10000 COUNTS

     Exposure_number: 50
         Target_Name: PSR0531+21
              Config: FOS/BL
              Opmode: ACCUM
            Aperture: 0.25-PAIR-A
          Sp_Element: G160L
          Wavelength: 1500.0
 Optional_Parameters: STEP-PATT=SINGLE
Number_of_iterations: 1
   Time_Per_Exposure: 250M


Data_Distribution

         Medium: 8MM
Blocking_Factor: 10
        Ship_To: PI_Address
       Ship_Via: UPS