Eclipsing Binary Worksheet.docx

Eclipsing Binary Star Systems Worksheet These lab activities have evolved over years of use in Clemson University’s Department of Physics and Astronomy general astronomy laboratory. Contributors include Tom Collins, Mark Leising, Neil Miller, Peter Milne, Grant Williams, Donna Mullenax, Jessica Crist, Keith Davis, Amber Porter, Lea Marcotulli, and David Connick. Please direct all questions, complaints, and corrections to David Connick (dconnic@clemson.edu) who is responsible for all errors and omissions. Name, section__ Andrew Birchler _____________ ____________ Basics 1: Roughly describe where the center of mass is located relative to the two stars that make up a binary system. The center of mass of a binary star system is located somewhere between the two stars which depends on the mass of the two stars and their distance from one another 2: Complete the following table related to the location of the center of mass. Systems Star 1 Star 2 Mass(M sun ) x Mass(M sun ) x X CM System A 6 0 6 10 5 System B 4 0 2 6 2 System C 3 0 6 6 4 3: If a small O2 spectral type star is completely obscured by a large M4 spectral type star, the drop in total luminosity of the binary system would be best described as … a) very large b) around 50% c) very small 4: Complete the following table related to stellar luminosities. Luminosity, Radius and Temperature values are all relative to the sun. Star Luminosity Radius Temperature A 9 3 1 B 16 1 2 C 4 1/2 2

Star Size 5: Describe how the relative size of the binary stars affects the light curve graph. The larger the difference between the size of the two stars is, the smaller the decrease is on the light curve graph. Star Temperature 6: What parameter changed between Example 1 and Example 3? Temperature of star 1 was increased 7: Which star is closer to the Earth during the primary eclipse? Star 2, the cooler of the two stars 8: What about the system causes the primary eclipse to be deeper than the secondary eclipse? (think about the relative luminosities of the stars) The fact that the hotter star is the one that is being blocked from view, because it has a larger luminosity because it is much hotter, so it has more on an impact on the depth of the drop in the graph. Star Mass 9: How does the position of the center of mass change when you increase the mass of star 1? The center of mass shifts closer to star 1 10: Why does the light curve remain constant as you change the mass of star 1? Because the radius is staying the same. Mass doesnt effect luminosity, radius and temperature do. Elliptical Orbits 11: How does the light curve change as the eccentricity increases? As eccentricity increase, the time of the two eclipses gets closer and closer together. Inclination Relative to Earth 12: When the inclination is set to 90 are the eclipses total or partial? Explain Total, because on star is completely blocking out the other star because it is moving directly between earth and the star on the same plane. 13: At what inclination do the eclipses become partial? (Use what you see in the plot and star simulation to support your answer) At about 66, that is the point in which the dips in the curve become rounded on the bottom and not flat 14: At what inclination do the eclipses cease to occur? (Use what you see in the plot and star simulation to support your answer) At roughly 48, that is where the light curve becomes completely flat with no dips Set the system to Example 8. Note that this system also has circular orbits, an inclination of 90°, and stars of 3R ⊙ and 1R ⊙ but now the separation has been increased to 25R ⊙ . Explore how changing the inclination affects the type of eclipse. 15: At what inclination do the eclipses become partial? Roughly 85 16: At what inclination do the eclipses cease to occur? Roughly 81

R2 1.7 T2 5326 Separation 4 26: With a top down view of this binary system do you think mass is transferred from one star to the other in this binary system? Why? Mass will be transferred because one star is much more massive so the gravity of the larger star will influence the gravity of the smaller star