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Astron. Astrophys. 340, 437-446 (1998)


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The active RS Canum Venaticorum binary II Pegasi

II. Surface images for 1992-1996 *

S.V. Berdyugina 1, 2, A.V. Berdyugin 1, 2, 3, I. Ilyin 1 and I. Tuominen 1

1 Astronomy Division, University of Oulu, P.O. Box 333, FIN-90571 Oulu, Finland (e-mail: sveta@ukko.oulu.fi)
2 Crimean Astrophysical Observatory, P.O. Nauchny, Crimea, 334413 Ukraine
3 Tuorla Observatory, University of Turku, Väisäläntie 20, FIN-21500 Piikkiö, Finland

Received 7 July 1998 / Accepted 21 August 1998

Abstract

Using new high-resolution and high signal-to-noise ratio spectroscopic observations carried out in 1992-1996, nine surface images of II Peg are obtained. The inversion technique applied is the recently developed Occamian approach, which does not put any artificial constraints on the solution and provides an error analysis of the solution. The surface imaging is applied to Ca I , Fe I , and Ni I lines simultaneously, a number of blending atomic and molecular lines being included into the line list.

Two high-latitude active regions are found to dominate in all seasons, which determine the spectroscopic and photometric variability. No cool polar cap is seen. The positions of the spots are constantly migrating to earlier orbital phases with approximately the same rate. This motion of the spot configuration means a shorter rotational period, which is just about the mean photometric period. The mean longitude separation between the active regions is about [FORMULA]. This is considered as two active longitudes. The largest of the two spots seems to be close to the central meridian, i.e. tends to be faced toward the secondary. In 1994 it changed its position from one active longitude to another, showing the effect of switching the activity between the longitudes.

Key words: stars: activity – stars: imaging – stars: individual: II Peg – stars: late-type – stars: starspots

* based on observations collected at the Nordic Optical Telescope (NOT), La Palma, Spain; the McMath telescope of the National Solar Observatory, USA; the 2.6 m and 1.25 m telescopes of the Crimean Astrophysical Observatory, Ukraine; the 2m telescope of the National Astronomical Observatory, Rozhen, Bulgaria; the 2m telescope of the Pic du Midi Observatory, France

Send offprint requests to: S.V. Berdyugina

© European Southern Observatory (ESO) 1998

Online publication: November 9, 1998

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