Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1988
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988a%26a...192..281d&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 192, no. 1-2, March 1988, p. 281-284.
Astronomy and Astrophysics
Astrophysics
7
Binary Stars, Chromosphere, Iue, Starspots, Light Curve, Stellar Spectra
Scientific paper
IUE observations of the RS CVn star II Peg in the upper chromospheric and transition regions lines Mg II k, C IV, and He II in 1981, 1983 and 1985 shows evidence for increased activity at certain phases. The Mg II k line flux shows an above average value between phases 0.0 and 0.5. This is largely biased by the 1981 and 1983 data-sets, although the 1985 data is consistent with a flux increase in this phase interval. The C IV and He II flux show quite clear evidence of an active hemisphere, although the 1985 data is less convincing than the combined 1981 and 1983. This is perhaps explained by the reduced number of observations in 1985, although an alternative explanation may be a more even distribution of plages during 1985. The above would therefore imply the presence of a long-lived plage region. The optical spot migration rate from late 1981 to early 1986 was only 0.03 rotations per year. The increase in the ultraviolet emission level occurs at the time of the minimum in the optical light curve, therefore implying a hot plage region overlying one of the cool optical spots.
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