Subject: IAU174 - abstract

From: [email-masked] (Greg Fahlman)
Date: Sun, 13 Aug 1995 13:14:02 +0800

Dear Jun:

 I am enclosing a preliminary abstract for my talk at IAU174. I
 trust it will not be too late to be of use to you. 
 
Best wishes:

Greg Fahlman.

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New Observations of M4 with HST

G.G. Fahlman.
Univeristy of British Columbia

A Canadian-American consortium has used the WFPC2 Camera on HST 
to obtain deep photometric observations 
in three radial fields of the nearby globular cluster M4. 
Recent progress with the analysis of this data will be described. 

The observations have clearly revealed an extensive white dwarf
sequence whose locus in the cluster colour-magnitude diagram 
corresponds closely to the cooling sequence expected of 
0.5 solar mass degenerate configurations. The observed 
cumulative luminosity function also 
agrees with the theory at least to the point where data incompleteness
becomes important. 

The cluster main sequence is very well defined below our data 
saturation level and can be used to place limits on the fraction of
nearly equal mass binaries among these stars. The apparent 
main sequence luminosity function shows a sharp break at an absolute
visual magnitude of about 12. However, the data clearly shows that a
sparsely populated 
main sequence continues to the limit of our data at V = 28. Therefore we
have not yet reached the end of the hydrogen burning main sequence
in this cluster. 

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