Coronal activity in F-, G-, and K-type stars |
| |
Authors: | R Mewe C J Schrijver C Zwaan |
| |
Institution: | (1) Space Research Laboratory, Beneluxlaan 21, 3527 Utrecht, HS;(2) Observatory, Zonnenburg 2, 3512 Utrecht, NL |
| |
Abstract: | Summary Soft X-ray (0.3–3.5 keV) observations with the Imaging Proportional Counter (IPC) onboard Einstein Observatory are presented for a sample of some 20 cool stars of luminosity classes III–V. The results are compared with the Ca II H and K emission, which had served as a selection criterion.The specific X-ray flux FX is an increasing function of the specific Ca II H and K line-core flux FH+K. This correlation can be considerably improved by replacing FH+K by the excess flux (FH+K) above a certain lower limit which varies with B-V. This relation holds with little scatter over the two decades in FX in our sample. The FX-FH+K relation shows no significant dependence on spectral type or luminosity class, it suits close binaries as well as single stars. However, the coronal X-ray temperature Tc strongly depends on the luminosity class: Tc 3 106 K for dwarfs and 107 K for giants.The results are interpreted in the framework of magnetic activity. The X-ray emission and the excess Ca II H and K flux are attributed to magnetic structure in the corona and chromosphere, the magnetic features emerging from the stellar convective envelope, where they are generated by dynamo action. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|