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