Determining Properties of the Eclipsing Binary CV Boo Using Differential Photometry

1. Determining Properties of the Eclipsing Binary CV Boo Using Differential Photometry Shelby L. Walters Benedictine College sxw01@uark.edu Arkansas-Oklahoma Center for Space and Planetary Sciences July 29, 2004 Fayetteville, AR 1

2. Presentation Overview XThe study of binary star systems is a worthwhile cause. XDifferential photometry was used to analyze images of CV Boo. XLight curve analysis was used to determine the properties of the stars in CV Boo. XLearning more about stars in binary systems will enable scientists to understand how most stars in the universe evolve. 2

3. Some Binary Basics XThe majority of stars in the universe belong to a binary system. X Scientists do not fully understand how binaries spend their lifetimes. X First major study of binaries was by Harvard Observatory from 1888 to 1962. X Photographic plates yield very inaccurate results. 3

4. Objectives Long-term: To determine which stellar evolution models for binary stars are accurate. Short-term: To determine the properties of CV Boo in order to contribute data used to test stellar evolution models. Primary Eclipse 4

5. Data Collection Dr. C.H.S. Lacy with the URSA telescope at the University of Arkansas in Fayetteville. 5

6. Differential Photometry Var = Variable Comp = Comparison Ck = Check 6

7. Software 7a

8. Night of eclipse as viewed in Measure: 7b

9. Software 7c

10. Light Curve Analysis X What is a light curve, anyway?A light curve is a plot of magnitude as a function of orbital phase. X What affects the shape of the light curve? A number of factors, including: mass ratio radii ratio luminosity temperature inclination eccentricity 8

11. EBOP Eclipsing Binary Orbit Program by Paul Etzel (1975) Parameters: Central Surface Brightness of Secondary Equivalent Spherical Radius of Primary Ratio of radii Limb-Darkening coefficients Orbital Inclination Orbital Eccentricity Gravity-Darkening coefficients Mass ratio Third Light Luminosity Scaling Factor 9

12. The first CV Boo light curve: 10

13. Evidence of star spots? Note: X magnitude outside of eclipse 11

14. Evidence of star spots? Note: X magnitude outside of eclipse X different magnitude on different nights 12

15. Light curve after normalization: 13

16. MRLcalc Similar to EBOP – it is designed specifically for the study of eclipsing binaries. Calculates: Absolute Visual Magnitude Mass Radius Log Surface Gravity Log Luminosity 14

17. Meet CV Boo… *Sun facts from The New Solar System written by Beatty and Chaikin. ‡Temperature for G0 stars from Popper (2000), AJ, 119:2391-2402. † Coefficients from Claret (1998), A&AS, 131:395-400. 15

18. Determining Age References: Schaller et al. (1992), A&AS, 96:269-331. Claret & Giminez (1992), A&AS, 96:255-268. Hejlesen (1987), A&AS, 69:251-262. Mengel (1979), ApJS, 40:733-791. Knowing properties MRLcalc found, the age was determined using interpolation and extrapolation: 10.3 billion years old! …but only 0.1% heavy elements 16

19. CV Boo plotted with other accurate binary data and Schaller et al’s theoretical ZAMS for binaries: 17

20. Future Work X Observe a predicted eclipse. X Confirm age with spectroscopic data. X Study more binaries to get accurate data and reject models that do not agree with it. X Refine models that correlate with accurate data. 18

21. Summary XThe majority of stars in the universe are part of a binary system, like CV Boo. XStudying eclipsing binaries yields the desired information relatively quickly and accurately. XLight curve analysis was used to determine that CV Boo is a star similar to our sun. XLearning more about stars in binary systems will enable scientists to understand how the majority of stars in the universe evolve. 19

22. Determining Properties of the Eclipsing Binary CV Boo Using Differential Photometry Shelby L. Walters Benedictine College sxw01@uark.edu Arkansas-Oklahoma Center for Space and Planetary Sciences July 29, 2004 Fayetteville, AR 20