Publication
The system V350 Sgr has a classical Cepheid for the primary. Interferometry is presented for the system, and the full orbit is determined. The mass of the companion has been determined from an International Ultraviolet Explorer spectrum and comparison with the mass-temperature relation from detached eclipsing binaries. Combined with the mass of the companion (2.6 +/- 0.2 M circle dot), the mass of the Cepheid is determined to be 4.7 +/- 0.8 M circle dot. For systems with less complete information, Cepheid masses can be determined from a single-lined spectroscopic orbit, Gaia proper motion anomalies, and the mass of the companion from the ultraviolet. Uncertainties resulting from different approaches to mass determination are discussed and are expected to be reduced after the Gaia DR4 release. Temperatures for Morgan-Keenan standard stars from the ultraviolet are also provided.