A&A Supplement series, Vol. 128, February II 1998, 29-33

Received February 3; accepted June 16, 1997

X-ray/optical observations of stars with shallow convection zones

A.J.M. Piters - J. van Paradijs - J.H.M.M. Schmitt

Send offprint request: J. van Paradijs

  Astronomical Institute "Anton Pannekoek" / CHEAF, Kruislaan 403, NL-1098 SJ Amsterdam, The Netherlands
  Physics Department UAH, Huntsville, AL 35899, U.S.A.
  Max Planck Institut für Extraterrestrische Physik, Giessenbachstraße 1, 8046 Garching bei München, Germany

Abstract:

We present Walraven photometry and ROSAT All-Sky Survey data for a sample of 173 bright main-sequence stars with spectral types between A8V and G2V. These observations are part of a study of the onset of magnetic surface activity along the main sequence. Values for the effective temperature, surface gravity and interstellar reddening have been obtained from a comparison of the observed Walraven colours with theoretical values. These parameters have been used to derive accurate X-ray surface flux densities.

keywords: stars: activity; fundamental parameters -- X-rays: stars

• 1. Introduction
• 2. Walraven photometry
• 3. Stellar parameters
• 4. The X-ray data
• References