|
If you are seeing this message, you may be experiencing temporary network problems. Please wait a few minutes and refresh the page. If the problem persists, you may wish to report it to your local Network Manager.
It is also possible that your web browser is not configured or not able to display style sheets. In this case, although the visual presentation will be degraded, the site should continue to be functional. We recommend using the latest version of Microsoft or Mozilla web browser to help minimise these problems.
Wiley InterScience | |||
  Monthly Notices of the Royal Astronomical SocietySee Also: Volume 297 Issue 2, Pages 388 - 398 Published Online: 4 Apr 2002 Journal compilation © 2010 RAS A Journal of the Royal Astronomical Society
Abstract | Full Text: PDF (Size: 6145K) | Related Articles | Citation Tracking  Chromospheric Ca II H and K emission among subdwarfs Copyright 1998 RAS KEYWORDS stars: activity • stars: chromospheres • stars: late-type • subdwarfs. ABSTRACTEchelle spectra have been obtained of the Ca II H and K lines for a sample of metal-poor subdwarf stars as well as for a number of nearby Population I dwarfs selected from among those included in the Mount Wilson HK survey. The main conclusion of this paper is that Ca II H- and K-line emission does occur among subdwarfs. It is particularly notable among those subdwarfs with colours of B−V≥0.75; all such stars observed exhibit chromospheric emission, although emission is observed among some subdwarfs bluer than this colour. The Ca II K emission profile in most subdwarfs exhibits an asymmetry of V/R>1, similar to that seen in the integrated light of the solar disc. Two quantitative indicators of the contrast between the peaks in the emission profile and the neighbouring photospheric line profile are introduced. Measurements of these indicators show that the level of Ca II emission among the subdwarfs is similar to that among low-activity Population I dwarfs.
| 
|
