! Proposal 6694, submission 1
! PI: Phil Charles
! Received Fri Feb 16 07:17:08 EST 1996
! From: p.charles1@physics.oxford.ac.uk
!  +====================+
!  | PED OUTPUT PRODUCT |
!  +====================+
!
!  /auto/home/mdl/pac/m33/6694.prop
!  Generated by PREPROCESSOR, version 6.0e
!  Date: Thu Feb 15 15:38:18 GMT 1996

Proposal_Information
              Title: High resolution UV imaging of M33-X8, the nuclear X-ray source in M33
  Proposal_Category: GO
Scientific_Category: GALAXIES & CLUSTERS
              Cycle: 6


Investigators

            PI_Name: Phil Charles
     PI_Institution: Oxford University


           CoI_Name: Pasi Hakala
    CoI_Institution: Oxford University
            Contact: 

           CoI_Name: Knox Long
    CoI_Institution: Space Telescope Science Institute
            Contact: 


Abstract:
The nucleus of M33 is known to contain the most luminous
steady X-ray source in the Local Group (Long et al.,1981). Our
recent ROSAT observations, however, indicate that the X-ray
emission shows peculiar variability at short, less than an
hour, timescales. The identification and study of the X-ray
source at optical wavelengths is impossible using ground based
techniques, as the (almost) stellar nucleus (V ~ 14.9)
dominates the flux. However, the nuclear X-ray source has L_X
~ 10^39 erg s^-1, which means that, if it has a typical
L_X/L_opt of ~ 500 (a conservative assumption), the expected V
magnitude (at the distance of M33) would be ~ 22.  However,
most of the optical light comes from late type stars, in a
slightly extended core, which means that high resolution far
UV imaging with HST provides the only means for identifying
M33-X8. This source could be the crucial link between luminous
X-ray binaries and ``micro-''AGN, and is by far the closest of
its type.


Questions


    Observing_Description:
We will use the WFPC2 with F170BW, F300W, F439W and F555W
filters. The identification of the X-ray source will be based
on its extreme UV colour and possible variability. We
estimate that given the distance of 720kpc, X-ray luminosity
of 10^39 erg sec^-1 and a typical L_X/L_opt of 500, we will
achieve 1000 and 4600 counts in 1000 seconds for the F170W
and F300W filters respectively. For F439W we will detect 1500
cts in 500 sec and for the F555W 1200 counts in 100 secs. The
table below gives the estimated count rates in 1000 sec
exposure for both M33-X8 and the rest of the nucleus. These
estimates, however, give the total number of counts. Earlier
ground based observations by Gallagher  et al (1982) have
shown that even at 1" seeing the nucleus is not a point
source (approximate extent ~ 1"). This results in a reduction
of counts per pixel by a factor of ~ 100, when compared to a
point source like M33-X8. We propose to obtain three 800 sec
FW170BW images during the first orbit and single images with
the rest of the filters during the second orbit.
begintabularlll &                    &        , Filter   &
M33-X8             & M33 core, &                    &     ,
F170W    & 1032 cts           & 1407 cts, F300W    & 4625
& 3925, F439W    & 3032        & 147607, F555W    & 11900
& 1004101 endtabular

  Real_Time_Justification:
We have already received further ROSAT HRI time (50ksec) to
continue our study of the X-ray variability of M33-X8.

Calibration_Justification:


      Additional_Comments:



Fixed_Targets

  Target_Number: 1
    Target_Name: M33-X8
Alternate_Names: 
    Description: STAR,LMXB,GALAXY,SPIRAL
       Position: RA=1H 33M 50.85S +/- 0.5",DEC=30D 39' 36.8" +/- 0.5"
        Equinox: J2000
        RV_or_Z: 
          RA_PM: 
         Dec_PM: 
          Epoch: 
Annual_Parallax: 
           Flux: 
                SURF-BKG(B) = 14.5+/-0.2
                V = 21.9+/-0.5
                B-V = 0.0
       Comments: 


Solar_System_Targets


Generic_Targets


Scan_Data


Visits

      Visit_Number: 01
Visit_Requirements: 
  On_Hold_Comments: 
    Visit_Comments: 

     Exposure_Number: 1
         Target_Name: M33-X8
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1
          Sp_Element: F160BW
          Wavelength: 
 Optional_Parameters: 
Number_of_Iterations: 1
   Time_Per_Exposure: 2500S
Special_Requirements: 
            Comments: 

     Exposure_Number: 2
         Target_Name: M33-X8
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1
          Sp_Element: F300W
          Wavelength: 
 Optional_Parameters: 
Number_of_Iterations: 1
   Time_Per_Exposure: 1700S
Special_Requirements: 
            Comments: 

     Exposure_Number: 3
         Target_Name: M33-X8
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1
          Sp_Element: F439W
          Wavelength: 
 Optional_Parameters: 
Number_of_Iterations: 1
   Time_Per_Exposure: 500S
Special_Requirements: 
            Comments: 

     Exposure_Number: 4
         Target_Name: M33-X8
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1
          Sp_Element: F555W
          Wavelength: 
 Optional_Parameters: 
Number_of_Iterations: 1
   Time_Per_Exposure: 100S
Special_Requirements: 
            Comments: 

Data_Distribution         ! Defaults indicated; change if desired

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

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