By Lindsey A. Whitesides and Florin D. Ciocanu University of Northern Colorado Frontier of Science...

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