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Physics Colloquium
Friday, Jan. 25th, 2008, 4:00 P.M.

E300 Math/Science Center; Refreshments at 3:30 P.M. in Room E200

Horace Dale

Department of Physics
Emory University

The Discovery of a New δ-Scuti Variable in Cassiopeia

Star variability not only gives us a greater understanding of distances in our universe but also an insight into how stars behave at different evolutionary stages. There are roughly 40,000 known variables in our galaxy, of which, there are only a handful of pulsating variables that can be used to determine distances based on their period-luminosity relation. The introduction of the CCD detectors along with improvements to instrumentation has led to the discovery of a sub-class of pulsators known as δ-Scutis which occupy the extreme lower end of the instability strip on the Hertzsprung-Russell diagram. Since δ-Scutis have pulsation periods along the order of 1 to 3 hours and amplitudes no greater than 0.1 magnitude, CCD photometry has played a vital role in their detection. Given the comparatively small population of only 540, very little is known about δ-Scutis because they are difficult to detect and exhibit both radial and non-radial pulsation modes. Therefore it is important for our understanding of this under-studied type of variable to collect and analyze a much larger sample. On October 4th, 2007 a new 12th magnitude δ-Scuti was discovered and added to the list by Emory Universitys Physics Department. Proving that even through modest light pollution a viable scientific contribution can be made towards the study of stellar pulsation.

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