Photometry of the 4686 A emission line of gamma(2) Velorum from the South Pole

• Main Author: Taylor, Maryjane
• Format: Other/Unknown Material
• Language: unknown
• Published: 1990
• Subjects: 89; Austral; South Pole; Amundsen-Scott; Amundsen Scott South Pole Station; Amundsen-Scott South Pole Station; Antarc*; Antarctica; South pole
• Online Access: http://ntrs.nasa.gov/search.jsp?R=19900066041

An automated optical telescope located at the Amundsen-Scott South Pole station on Antarctica, has been used to obtain more than 78 h of photometry of the He II emission line (4686 A) of the spectroscopic binary gamma(2) Velorum. These data were obtained on seven different days during the 1987 austral winter; the longest continuous run spans 19 h. Two independent period search techniques have been used to search for periodic behavior in the strength of the He II emission line of this Wolf-Rayet star. They are: (1) power spectrum analysis and (2) a first-order sine function fit to the data using least squares. Various multiplicities of a period on the order of 1.3 h with amplitudes of a few percent are found in most of these data. According to recent theoretical models of Wolf-Rayet stars, fluctuations in the He II emission line may indicate vibrational instability in gamma(2) Vel. These pulsations may, in turn, give rise to shocks which propagate outward and which may provide the necessary conditions for periodic changes in the state of a given region of the atmosphere to occur.