The Nature of the Dwarf CepheidXX-Cygni

Photometry of XX Cyg in the uvby and β systems has been secured and analyzed. A reddening value, E(b - y) = + 0.m057, is derived from the photometry. Intrinsic (b - y) and c1 values are used to determine a mean effective temperature, eff> = 7530 K, and a mean surface gravity, = 3.66. XX Cyg is found to be a metal-poor dwarf cepheid with [Fe/H] = -0.49. A radius of 2.4 Rsun has been found from the Wesselink method. The radius and effective temperature indicate that bol> = + 1.7. A mass of 1.0 Msun is found from the radius and effective gravity. The radial-velocity data yield a mean radial velocity of -108 km s-1 and a total velocity range of 37 km s-1.