STUDIES OF LARGE-AMPLITUDE DELTA-SCUTI VARIABLES - III - DY PEGASI

This is the third in a series of papers on large-amplitude delta Scuti and related stars intended to determine Baade-Wesselink radii and lum inosities with precision. The first two papers discussed our method of analysis and its application to the delta Scuti variables EH Librae a nd DY Herculis: in the present paper we discuss the observations and a nalysis of the SX Phoenicis variable DY Pegasi. Optical (BVI) and infr ared (JH) photometry and cross-con-elated radial velocity data have be en obtained and analyzed. Fourier representations for the BVIH light c urves and for the radial velocity curve were used to derive a value fo r the minimum radius for each of 22 combinations of flux and color ind ex, from which we obtain a mean value for the minimum radius of R-min = 2.09 +/- 0.25 R.. When combined with effective temperatures from Bur ki & Meylan, we find a mean bolometric luminosity of [L-bol] = 11.34 L . and a mean absolute magnitude of [M-bol] = 2.11. The radial excursio n (R-max -R-min) is 0.073 R..