PHOTOMETRY AND GEOMETRICAL ELEMENTS OF CC COMAE.

Abstract

ABSTRACT The average color indices (B- V) = + and (U- B) = + and short period (F = 0d2207) place this system at the lower temperature end of the period-color relation for the W UMa-type binaries. During minima the indices change to (B- V) = + 1'P29 and (U- B) = + 100; however, the (U- B) index reveals rather large scatter and was also observed to decrease abnormally to (U - B) = + 0' '93 during one primary minimum. It is unclear whether these abnormal variations in (U- B) are related to an ultraviolet excess of about + 0.1 (unfortunately no red-leak corrections were applied) although some support for that can be found in the fragmentary uvhy photometry. Small night-to-night changes might be present in the V-light curve as well. The large amplitude of light variation (0.85 and 0.75 magnitude in V) and the presence of a total eclipse with semiduration of totality of about 8 permit one to determine the geometrical elements with rather high accuracy, in spite of relatively large photometric errors due to the faintness of the system (+ 11.3 V + 12.2). CC Com belongs to the W-type systems, with a relative temperature excess of the secondary component X = 0.051 :::: 0.002. Other elements are: i = 900 ::::: 02, (1 = 0.521 l 0.004,f = 0.765 j 0.013 for the assumed Te = 4300 K. The membership of CC Com in the Coma Cluster (Mel 111) is discussed and shown to be very likely, but its acceptance must await further proper-motion studies. The individual times of minimum light of CC Com, and the new ephemeris, are given. Key words: light-curve synthesis - contact binaries