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Session 26 - Stars in the Visible & IR.
Display session, Tuesday, June 10
South Main Hall,
The bright star Spica is one of the more interesting of the first magnitude stars. First it is a spectroscopic binary consisting of two B stars revolving about a common center of mass with a period of approximately 4.01 days. The two components are deformed by their mutual gravitational interaction into oblate spheroids which are tidally locked to each other. The fact that in part of the orbit we observe the two stars edge on and in another part we observe then pole on leads to a variation in the brightness making Spica an ellipsoidal variation. In the late 1960šs it was discovered that Spica was also a pulsating variable of the Beta Cephei type the strongest excited period approximate 0.174 days. Even stranger in the early 1970šs the pulsation apparently ceased. Since then Spica has been monitored sporadically both photometrically and spectroscopically in attempt to observe a resumption of the pulsation. To date this has been unsuccessful. This paper reports on the most recent of these attempts carried on during the 1995- 96 observing season and continued until the present. Spica has been observed with the Four College Consortium APT located on Mt. Hopkins during the 1995-96 season and at the Fairborn Observatory Station at Washington Camp, AZ during the 1996-97 season. The work has been supported in part by NSF grants AST86-16362, AST91-15114, USE91056184, and AST95-28506 to the College of Charleston.
