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A&A Supplement series, Vol. 123, June II 1997, 455-471

Received May 13, accepted October 10, 1996

A photometric and spectroscopic study of the association LH47 in the superbubble N44 in the LMCgiftex2html_wrap_inline2101

J.-M. Willtex2html_wrap2147gif - D.J. Bomanstex2html_wrap2149gif - A. Dieballtex2html_wrap2151

Send offprint request: J.-M. Will,
Sternwarte der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany - University of Illinois at Urbana-Champaign, Department of Astronomy, 1002 West Green Street, Urbana, IL 61801, U.S.A.


The OB association LH47 inside the superbubble N44 in the Large Magellanic Cloud (LMC) is analyzed with CCD photometry. For the bright blue stars spectra in the optical and UV have been taken. The observed U, B, and V magnitudes and colours are converted to tex2html_wrap_inline2121 and L. From isochrone fits to the colour magnitude diagram (CMD), we find an age of the association of about 5 to 6 Myr. The stellar population outside the shell is of similar age, so there is no direct evidence for sequential star formation.

The slope of the luminosity function (tex2html_wrap_inline2125) agrees with what has been found for other young associations. We compare two methods to derive the slope of the initial mass function (IMF). First we count all stars along the main sequence in the BV CMD. Second we count the stars between stellar evolutionary tracks in the Hertzsprung-Russell diagram (HRD). Both methods give mainly the same result, i.e. x=1.37 and x=1.22, respectively. The IMF of the stars outside the shell shows a slightly steeper slope than inside the shell. The slope of the IMF is very similar to values found for other associations and open clusters as well as in the solar neighborhood, thus supporting the idea of an universal shape of the IMF. LH47 turns out to be a well behaved young association embedded in a molecular cloud.

keywords: stars: early-type -- Hertzsprung-Russell (HR) diagram -- stars: luminosity function, mass function -- open clusters and associations: individual: LH47 -- Magellanic Clouds

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