By Lindsey A. Whitesides and Florin D. Ciocanu
University of Northern Colorado
Frontier of Science Institute
OBSERVING THE MIRA VARIABLE STARS LEO USING CCD PHOTOMETRY
PURPOSE• Observe the Mira variable S Leo
• Obtain accurate data
• Create a partial light curve
• Find the faintest point of the period
• Submit results to AAVSO
• Contribute to scientific community
INTRODUCTION• Variable star
• Mira variable
• Long period
• Red giants
• Cool (3500 K)
• Magnitude scale
• Magnitude varies 2.5 to 10
INTRODUCTION• Charge-coupled device (CCD)
• Photoelectric effect
• Pattern of electrons
translated into image
• Photometry
• Eliminates most error
Figure 1: CCD chip.
INTRODUCTION• CCD importance to astronomers
• Amateur astronomers
• Professional-Amateur collaborations
• AAVSO
• VPhot
METHODS• Global Rent a Scope (GRAS)
• Telescopes G1 & G7
Figure 2: Global Rent a Scope website.
Figures 3a & 3b: Global Rent a Scope telescopes.
METHODS• Generate a plan
• Coordinates of the star
• Picture count
• Filter
• Exposure time
• Plate-solve
• Automatically upload to VPhot
METHODS• Reservation
• Local time and date
• Weather forecast
• Position compared to moon
• Load plan
• Images taken by UNC students
• Process replicated with different star (TrES-3)
METHODS• VPhot
• Load GCVS
• Load AAVSO comp stars
• Aperture and sky annulus
• Removing useless comp stars
• Check star
• Photometry Report
Figure 5: VPhot program.
RESULTS
RESULTS• Magnitude increased then decreased
• Faintest day about March 26th
• Partial light curve constructed
• Average error
• Standard deviation
RESULTS
Figure 6: A graph of magnitude vs. time for S Leo.
RESULTS
Figure 7: Results plotted against data from AAVSO light curve.
DISCUSSION• Very low error
• Accurate enough for AAVSO
• Partial light curve matches
• Some images were unusable
• More images should have been taken
ACKNOWLEDGEMENTS• Sponsors:
• Dr. Richard Dietz
• Lori Ball
• Nick True
• Abby Davidson, Nathan Kirkley and Zabedah Saad
• Karen Allnut and Klois Broeker
REFERENCESBucheim, R.K. (2007). The sky is your laboratory: Advanced astronomy projects for amateurs. Chichester, UK: Springer-PraxisClayton, M.L. & Feast M.W. (August 11, 1969). Absolute magnitudes of Mira variables from
statistical parallaxes. Monthly Notices of the Royal Astronomical Society, vol. 146, p.411-421. doi: 1969MNRAS.146..411C
O’Connell, Robert (September 8, 2003). Magnitude and color system. Retrieved from http://www.astro.virginia.edu/class/oconnell/astr511/lec14-f03.pdf
Richmond, M. Introduction to CCDs. Retrieved from http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.htmlRobertson, B.S.C. & Feast M.W. (July 16, 1980). The bolometric, infrared and visual
absolute magnitudes of Mira variables. Monthly Notices of the Royal Astronomical Society, Monthly Notices, vol. 196, July 1981, p. 111-120. doi: 1981MNRAS.196..111R
Roger A. Freedman, William J. Kaufmann III (2008). Universe: Stars and Galaxies (3rd edition). New York, NY: W.H. Freeman and Company
Templeton, M. (April 14, 2011). Variable stars and the stories they tell. Retrieved from http://www.aavso.org/variable-stars
Templeton, M. (September 13, 2010). Stellar evolution. Retrieved from http://www.aavso.org/stellar-evolution