Expanding shell and P Cygni profiles of 27 Canis Majoris

Abstract

H-alpha and He I profiles of 27 CMa obtained between January 1985 and February 1989 are presented. Velocities of blue absorption and red emission components of H-alpha were different from that of He I, suggesting that the regions of formation of H-alpha and He I were different in the expanding shell of 27 CMa. Velocities of all the components of H-alpha were variable between April 16 and 18, 1989. But, from April 18, when the blue emission velocities were almost unchanged, the blue absorption and red emission velocities were decreasing and those for He I components were increasing. Equivalent widths of blue emission components of He I lines were almost constant during the observational interval, while red emission strengths of H-alpha profile displayed weak variations between April 16 and 26. He I and H-alpha profiles clearly show that 27 CMa has entered into a new shell phase.