\newcommand{\msol}{M$_\odot$}

<HEADER><TITLE>UV and optical photometry of 508 stars in 37 M31 OB associations.</TITLE>

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<DL><DT><B>Session 49 -- Associations and Clusters</B>

<DT><I>Display presentation, Wednesday, 9:20-6:30, Pauley Room</I>

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<H2>[49.05] UV and optical photometry of 508 stars in 37 M31 OB associations.</H2>

<I>J. K. Hill, J. E. Isensee (Hughes STX), R. C. Bohlin (STScI), K. P. Cheng, M. N. Fanelli, P. M. N. Hintzen, Andrew M. Smith, Eric P. Smith (NASA/GSFC), R. W. O'Connell (University of Virginia), M. S. Roberts (NRAO), T. P. Stecher (NASA/GSFC)</I>

<P>Magnitudes are measured in up to 5 bands (far-UV, near-UV, U, B, and R)

for 508 massive stars in 37 M31 OB Associations.

${m_{249}}-B$ vs. ${m_{249}}$ and ${m_{152}-m_{249}}$ vs. ${m_{152}}$

color magnitude diagrams are presented.  Comparison with the evolutionary

tracks of massive stars show that the likely mass range of the brightest

association stars is 60-70 \msol in NGC 206 (A78) and A69, and 20-40 \msol

in the other associations.  Ages for the most recent star formation in the

24 associations with both near-UV and far-UV stellar photometry are estimated

at 3--10 Myr, by assuming the star with the largest far-UV flux to be a

supergiant at the age of maximum luminosity. Maximum stellar masses are also

estimated for each association, under this assumption.



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