Radio Observations of O-Type Stars

Abstract

Eight O-type giants and supergiants, selected for being relatively isolated in the sky, have been observed at 5 GHz with 17 antennae of the partially completed VLA (NRAO, Socorro, New Mexico: The National Radio Astronomy Observatory is operated by Associated Universities under contract with the National Science Foundation) on October 7 and 8, 1979. The integration times ranged between 38 and 187 minutes. The results are displayed in Table 1. Most of the stars (6 out of 8) were not detected. The upper limits given in Table 1 for these stars correspond to the 3σ noise level. Possible detection has been achieved for the two supergiants HD 225160 and HD 30614 both with a flux density of 0.15 mJy. Although this flux is equal to the 3σ noise level, the detections can be considered to be real because 1) Excellent positional coincidence is found between stars and the radio peaks (better than 1") 2) The observed source pattern corresponds very well to the expected response to a point-like source.