Radio observations of the binary stars UX Ari and HR 1099.

Abstract

The binary stars UX Arietis and HR 1099 have been observed at 2380 and 1400 MHz and UX Arietis was searched for at 430 MHz. A comparison of our observations with previous studies indicates that the radio spectra of these stars are typically flat from 1400 to 8085 MHz. A significant upper limit to the 430-MHz emission from UX Arietis was obtained, showing that the spectrum turns over between 1400 and 430 MHz. Circular polarization was detected in the 1400-MHz radiation from UX Arietis at a level of about 5%, and from HR 1099 at about 20%. It is suggested that the radio emission from these binaries is due to a gyrosynchrotron source which is optically thick to free--free absorption. Model-dependent source parameters are derived.