THE ORBIT AND COMPANION OF THE CEPHEID S-SGE - A PROBABLE TRIPLE SYSTEM

New radial velocities for the classical Cepheid S Sge have been obtain ed and combined with previous observations to derive a new orbit. The revised orbital elements are: gamma, -10.3+/-0.4 km s-1; K, 15.5 +/- 0 .2 km s-1; e, 0.23 +/- 0.02; omega, 203.1 +/- 4.2-degrees; T0, 39902.3 +/- 6.6 JD; P, 675.79 +/- 0.18 days; f(m), 0.239 +/- 0.010M.; a sin i , 0.935 AU = 139.9 +/- 2.0 X 10(6) km; s.e., 1.2 km s-1. The revised e lements differ very little from the orbit determined by Herbig & Moore [ApJ, 116, 348 (1952)]. We have also obtained low resolution Internat ional Ultraviolet Explorer (IUE) spectra to search for the companion. The IUE spectra show excess flux at 1800 angstrom when compared with s pectra of the single Cepheid delta Cep at the same (B-V)0. The spectra l type of the companion determined from this flux excess is A7 V to F0 V. However, the mass of such a companion (1.7 to 1.5 M.) is smaller t han the minimum mass (2.8M.) required by the mass function and an evol utionary mass of the Cepheid. We infer that the companion is itself a short period binary.