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Astron. Astrophys. 325, L25-L28


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Letter to the Editor

The effect of rotation on the absolute visual magnitudes
of OB stars measured with Hipparcos*

H.J.G.L.M. Lamers1,2, J.M.A.G. Harzevoort1,2, H. Schrijver2, R. Hoogerwerf3, and R.P. Kudritzki4,5

1Astronomical Institute, University of Utrecht, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
2SRON Laboratory for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands
3Leiden Observatory, PO Box 9513, 2300 RA, Leiden, The Netherlands
4Institut for Astronomie und Astrophysik der Universität München, Scheinerstrasse 1, D-81679 München, Germany
5Max Planck Institut für Astrophysik, Karl-Schwarzschild-Str.1, D-85740 Garching bei München, Germany

Received 6 June 1997 / Accepted 10 June 1997

Abstract

We derive the absolute visual magnitudes of 14 OB-stars of luminosity class III to V from the parallaxes measured by Hipparcos. The values of MV can differ by as much as 1.m5 from the MV-spectral type calibration. Slowly rotating stars, v sin i < 100 km s-1, are significantly fainter in MV than stars with v sin i > 100 km s-1 of the same spectral type by about 1 magnitude. We discuss this effect and argue that it is due to the influence of rotation on the assignment of spectral types and luminosity class. Slowly rotating stars are also fainter than the standard MV-spectral type relation. This effect has important consequences on the distance determinations of stars and clusters from Mv and V.

*Based on data from the ESA Hipparcos astrometry satellite


© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 28, 1998
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