Variable Stars of Globular Clusters in the Large Magellanic Cloud

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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

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Outline

• Background-
• RR Lyrae Variables
• The Hertzsprung-Russell diagram
• Globular Clusters
• Satellite Galaxies
• Galaxy Formation
• Oosterhoff Dichotomy
• NGC2210-
• Instruments
• Procedure
• Results

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RR Lyrae Variables

• Low mass 0.8 solar masses
• Population II - 10Gyr old
• Radial Pulsation
• RRab example Fundamental Mode

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RRc

• First Overtone

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The Hertzsprung-Russell Diagram

• Temperature vs. Luminosity

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Globular Clusters

• Globular Cluster H-R Diagram

Soar image of NGC2210
(Smith 1995)
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Satellite Galaxies

• Large and Small Magellanic Clouds, other dwarf
  spheroidal galaxies
• Role in formation of Galactic Halo?

NASA/ESA 2008
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Oosterhoff Dichotomy

• Bimodal Period Distribution for Galactic GCs
• OoI average ab P0.55 days
• OoII average ab P0.65 days
• Oosterhoff Gap 0.58 lt P lt 0.62
• What about globular clusters in satellite
  galaxies?

Catelan 2005
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NGC2210-Instruments

• SOAR-
• 4.1m mirror
• Feb. 5-18, 2008

• SMARTS-
• 1.3m mirror
• Sep. 4-Dec. 31, 2006

MSU 2005
SMARTS Consortium 2008
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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

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Lightcurves

• Type ab lightcurve

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Lightcurves

• Type c lightcurve

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Results

• Soar Color-Magnitude Diagram

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Results

• Smarts Color-Magnitude Diagram

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Results

• Average ab Period0.596 days

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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

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Thanks

• Special thanks to Dr. Horace Smith and Charles
  Kuehn