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An EXOSAT Observation of Spectral Variability From the RS CVn Binary AR LAC

Published online by Cambridge University Press:  12 April 2016

N.E. White ,
R.A. Shaffer ,
A.N. Parmar ,
K. Horne  and
J.L. Culhane
N.E. White
Affiliation:
EXOSAT Observatory, ESTEC, Noordwijk, The Netherlands
R.A. Shaffer
Affiliation:
EXOSAT Observatory, ESTEC, Noordwijk, The Netherlands Present address: GSFC, Greenbelt, Maryland, USA
A.N. Parmar
Affiliation:
EXOSAT Observatory, ESTEC, Noordwijk, The Netherlands
K. Horne
Affiliation:
Space Telescope Science Institute, Baltimore, Maryland, USA
J.L. Culhane
Affiliation:
Mullard Space Science Laboratory, Holmbury St Mary, Surrey, UK

Abstract

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The eclipsing RS CVn system AR Lac (G2IV+K0IV) has been observed continuously for one 2 day binary cycle with the EXOSAT observatory. Below 1 keV a factor of two intensity modulation is seen with a flat bottomed minimum around the time of primary eclipse and a shallow dip preceeding primary eclipse. Above 1 keV, where only emission with temperatures > 107 K would be detected, no orbital modulation or eclipse is seen. This suggests that the > 20 million degree emission comes from a large region, comparable in size to the binary seperation. The modulation in the < 1 keV lightcurve has been modelled by x2 fitting to X-ray bright spots and by using maximum entropy deconvolution. The lower temperature emission is found to orginate in compact regions with a pressure and temperature similar to that of the flaring sun.

Type
5. Compact Binaries
Information
International Astronomical Union Colloquium , Volume 115: High Resolution X-ray Spectroscopy of Cosmic Plasmas , 1990 , pp. 175 - 186
Copyright
Copyright © Cambridge University Press 1990

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