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Variable Stars of Globular Clusters in the Large Magellanic Cloud
Evan McClellan (FSU)
Horace Smith (advisor) (MSU)
Charles Kuehn (MSU)
August 6th, 2008
Outline
• Background-– RR Lyrae Variables– The Hertzsprung-Russell diagram– Globular Clusters– Satellite Galaxies– Galaxy Formation– Oosterhoff Dichotomy
• NGC2210-– Instruments– Procedure– Results
RR Lyrae Variables
• Low mass ~0.8 solar masses• Population II - ~10Gyr old• Radial Pulsation• RRab example: Fundamental Mode
Satellite Galaxies• Large and Small Magellanic Clouds, other
dwarf spheroidal galaxies
• Role in formation of Galactic Halo?
NASA/ESA 2008
Oosterhoff Dichotomy• Bimodal Period Distribution for Galactic GCs• OoI: average ‘ab’ P~0.55 days• OoII: average ‘ab’ P~0.65 days• Oosterhoff Gap: 0.58 < P < 0.62• What about globular clusters in satellite galaxies?
Catelan2005
NGC2210-Instruments• SOAR-
– 4.1m mirror– Feb. 5-18, 2008
• SMARTS-– 1.3m mirror– Sep. 4-Dec. 31, 2006
MSU 2005 SMARTS Consortium 2008
Procedure
• For each set of data-– Define “star”– Find stars– Align images– Combine– Make CMD
• Putting it all together-– Synch star names– Calibrate brightness– Find “variables”– Filter out non-RR-Lyrae– Combine lightcurves– Plot period vs.
amplitude
References
• Carrol and Ostlie, An Introduction to Modern Astrophysics, Addison-Wesley, 2007
• Catelan, M. 2005, astro-ph/0507464
• Catelan, M. 2006, astro-ph/0604035
• De Lee, N. Variable Stars in NGC6304, MSU 2004
• MSU, 2005, http://www.pa.msu.edu/soarmsu/
• NASA/ESA, 2008, http://www.spacetelescope.org/
• SMARTS Consortium Website, 2008, http://www.astro.yale.edu/smarts/
• Smith, H.A. RR Lyrae Stars, Cambridge University Press, 1995