High-velocity interstellar gas in the line of sight to the Wolf-Rayet star HD 50896

Abstract

A large, high-velocity interstellar shell has been discovered in the direction of the Wolf-Rayet star HD 50896. Two distinct high-velocity interstellar components at approximately -80 and -125 km s^-1 were detected in the low-ionization resonance lines of IUE spectra for HD 50896 and 11 neighboring field stars, precluding the possibility that this high-velocity gas is related to S308, the prominent ring nebula surrounding HD 50896. The data collected for HD 50896, at a distance of 1.5 kpc, and for 19 field stars located up to 4° from HD 50896 with distances ranging from 0.6 to 2.9 kpc, indicate that the high-velocity interstellar gas lies at a distance of 1.0±0.2 kpc, has a diameter in excess of 90 pc, and is probably physically associated with the cluster Cr 121. The authors conclude that this high-velocity expanding interstellar shell represents a previously unidentified, well-evolved supernova remnant. Implications for a possible association of the supernova remnant with HD 50896 and its suspected binary companion are discussed.