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Astron. Astrophys. 325, L25-L28 (1997)

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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. Lamers 1, 2, J.M.A.G. Harzevoort 1, 2, H. Schrijver 2, R. Hoogerwerf 3 and R.P. Kudritzki 4, 5

1 Astronomical Institute, University of Utrecht, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
2 SRON Laboratory for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands
3 Leiden Observatory, PO Box 9513, 2300 RA, Leiden, The Netherlands
4 Institut for Astronomie und Astrophysik der Universität München, Scheinerstrasse 1, D-81679 München, Germany
5 Max 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 [FORMULA] can differ by as much as [FORMULA] 5 from the [FORMULA] -spectral type calibration. Slowly rotating stars, [FORMULA] [FORMULA] 100 km s-1, are significantly fainter in [FORMULA] than stars with [FORMULA] [FORMULA] 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 [FORMULA] -spectral type relation. This effect has important consequences on the distance determinations of stars and clusters from [FORMULA] and V.

* Based on data from the ESA Hipparcos astrometry satellite

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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