Study of FK Comae Berenices^*,**

III. Photometry for the years 1993-2001

¹ Astronomy Division, PO Box 3000, 90014 University of Oulu, Finland
² Observatory, PO Box 14, 00014 University of Helsinki, Finland
³ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁴ Astronomical Institute of the Academy of Sciences of Uzbekistan, Astronomicheskaya 33, Tashkent 700052, Uzbekistan
⁵ Tuorla Observatory, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
⁶ Dipartemento di Fisica, Universita degli Studi di Padova, Via 8 Febbraio, 2, 35122 Padova, Italy

Corresponding author: H. Korhonen, heidi.korhonen@oulu.fi

Received: 5 March 2001
Accepted: 30 May 2001

Abstract

We present 8 years of previously unpublished photometric observations of FK Com together with the determination of the stability of the primary comparison star HD 117567. The observations have been carried out between 1993 and 2001 at four different observatories and they consist of 5157 data points in total: U(903), B(994), V(1643), R(166), I_c(573), b(461) and y(417). We also analyse this new data together with the previously published photometric observations. The V magnitude shows variations with dominant periods of about 3, 6, 12, 14 and 31 years. The short-term light curve variations appear to be caused by rearrangement of approximately constant amount of cool spots. From the values for different colours obtained during the brightest season observed, corresponding to the supposedly unspotted surface, the spectral type of FK Com is determined to be G7 III.