Astron. Astrophys. 337, 757-771 (1998)

Prominence and plage activity in the recently discovered late-type rapid rotator, RE 1816+541

M.T. Eibe

Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland

Received 6 May 1998 / Accepted 30 June 1998

Abstract

The rapidly-rotating, chromospherically active late-type star RE 1816+541 has shown signs of intense magnetic activity in various forms. Time-series of high resolution spectra have been obtained during three nights and several important events were detected. Observations contained several chromospheric lines, allowing us investigate simultaneously the response of the chromosphere at different heights.

A detailed analysis of the H line behaviour, in particular, has revealed prominence clouds and plage-like regions in this star. Rapid rotation favours detection and further investigation of these features. Prominence clouds are seen to lie below the co-rotation radius. A bright plage-like region was well resolved on the first night. The feature disappeared temporarily during meridian crossing, coinciding with the passage of a cloud. Complete obscuration of the plage by the cloud proves that the emission feature is located on or near the stellar surface, whereas the cloud is at larger height and is seen in projection onto it. A very large flare was also detected during the observations, having strong effects in all the chromospheric lines selected for study.

Key words: stars: activity stars: chromospheres stars: individual: RE 1816+541 starspots

Present address: LAEFF, Apdo 50727, E-28080 Madrid, Spain

Send offprint requests to: M.T. Eibe

SIMBAD Objects

Contents

• 1. Introduction
• 2. RE 1816+541
• 3. Observations and data reduction
• 4. Calculation of the stellar velocity
  • 4.1. Radial velocity
    • 4.1.1. Rotational velocity
• 5. Variability of chromospheric emission
  • 5.1. The H emission line
  • 5.2. Other spectral lines
• 6. Analysis of the H variations
  • 6.1. Absorption features
    • 6.1.1. Transient A
    • 6.1.2. Transient B
    • 6.1.3. Transient C
  • 6.2. Emission features
    • 6.2.1. Transient a
    • 6.2.2. The strong emission on June 27
• 7. Discussion
  • 7.1. Prominence clouds
    • 7.1.1. The cloud detected as transient A
    • 7.1.2. Transient B
    • 7.1.3. Transient C
  • 7.2. Plage activity
• 8. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: August 27, 1998
helpdesk.link@springer.de