Luminosity and colour distribution in the interacting system NGC 7770-71. I: Surface photometry of NGC 7771

Based on photographs collected with the 74-in. telescope of Kottamia Observatory, Egypt, isophotes, luminosity profiles, and photometric parameters for the SB(s)a galaxy NGC 7771 have been obtained in the blue spectral band. The absolute magnitude is found to be -21.70 for a distance of 90.2 Mpc, and an equivalent effective radius of 0.29 arcmin and an effective surface brightness of 22.30 mag/sq s are derived. The major axis is shown to be in a position angle of 69.5 + or - 1 deg, and the mean axis ratio of the outer regions of 0.45 corresponds to an inclination of 66 deg. The equivalent luminosity distribution is decomposed into two main components, an r exp 1/4 spheroid contributing 31 percent to the total blue luminosity, and an exponential disk contributing 69 percent. Results suggest that the galaxy is bluer toward the center than the normal galaxies of the same type, supporting its classification as a Markarian galaxy. (R.R.)