R 127 : an S DOR type variable intermediate between Of and WN.

Abstract

The results of extensive photometric and high resolution spectroscopic observations of the S Dor variable R 127 are presented and discussed. These observations show the star to be hotter than any of its type previously discovered. Its bolometric magnitude is 10.6, its effective temperature is 16,000 K, and its radius is 150 solar radii. The stellar wind has a small mean velocity of 110 km/s, a high mass loss rate of 6 x 10 to the -5th solar mass per year, and a decelerated velocity field. The optical spectra show strong Balmer lines with P Cygni profiles. The H I lines changed during the one-year observational period from strong P Cygni type lines to complex line profiles with extremely wide shallow emission line wings. The IUE spectra are dominated by crowded absorption lines of singly ionized metals whose multiple substructure suggests a very complex shell. It is suggested that R 127 is evolving to a WN star via a short S Dor phase.