UV, optical and IR observations of cepheid R Mus.

Ultraviolet IUE spectra, optical 12 A/mm red and blue spectra, optical BV photometry and infrared JHKL photometry of the 7.5-d classical Cepheid R Muscae equals HD 110 311 are presented and discussed together with some earlier photometric and radial velocity data. Using the CORS method, a newly derived radius is given, as well as new values for effective temperature and log g. The UV spectra confirmed the predicted trend to increasing amplitudes with decreasing wavelength and indicate that R Mus has a shallow chromosphere, while no transition region lines could be detected. From all the data from 1200 A to 5 microns it is concluded that R Mus does not have a companion detectable with the sensitivity given, contrary to earlier results.