1. X-Ray Binaries Aisling Hunt, Andrew Caide Cambridge Rindge and Latin School May 12, 2007 Chandra Astrophysics Institute

2. Outline • Introduce our models on what goes on in an X-Ray binary system. • Data found to prove one of our two current models • Our final proven model

3. Introduction and Background • A Variable star = inconsistent flux (over a certain period the flux, or brightness, will change) • Variable star can be caused by a binary star system - two stars orbiting around each other

4. Models The binary star system we observed is a Neutron star accreting matter from a blocking star The star system in a black hole accreting matter from a blocking star

5. Why a Neutron Star and Black Hole? • Neutron Stars give off x-ray light due to high temperatures • Massive • Have a surface • Black holes • Massive • Accreted matter caught in accretion disk heats up and produces x-ray light • No surface

6. Data/Methods • Ds9 Image Analysis Software • Observed a binary star system’s light curve • orbital period • Duration of eclipse • Fit the spectrum of the x-ray source • Radius of the x-ray emitter • Kepler’s 3rd law: • 4 pi^2/ Gravitational Constant (Mass Star1+Mass Star 2) Radius of orbit^3= Period of Orbit^2 • We used Kepler’s law to find the Radius of the Orbit Light curve plot, ds9

8. SAME LIGHT CURVE Results • LIGHT CURVE: -orbit period=20,000s -Duration of eclipse= 1,700s

9. Results

10. Results of Spectral Fit • Flux (amount of light reaching Chandra) = 1.08x10-13 ergs/cm2/s • Temperature = .24KeV = 3x106K • Total luminosity = 2.43x1032ergs/s • Radius of x-ray emitting source is about 1 km

11. First Claim • 3 Possibilities for size: • Blocker>>Source • Source>>Blocker • Source ~Blocker DIAGRAM OF ECLIPSE Comparison of light curves

12. Second Claim • The x-ray emitting object in binary star system 4u2129 is a Neutron Star • Main pieces of evidence: • Radius of the x-ray object • Radius of blocking star

13. Radius of X-ray Object • Actual size of object= 1km • Size of 10 solar mass black hole is approx 30 km + the size of the accretion disk • Average size of neutron star is approx 10 km • But they are not an exact fit… • Measuring only 1/10 of actual neutron star • Not possible to only measure 1 km of a black hole

14. Radius of Blocking • Estimated size of a .5 solar mass star~ .5 Solar radii The radius of the visible light star in the neutron star model is a closer fit To the estimated size than the radius of the star in the BH model.

15. Conclusions • We have come to the conclusion that the model that best represents our data is that a neutron star is the x-ray object accreting matter from a blocking star in binary star system 4u2129 • Size of the x-ray emitting source • Size of the visible light star

16. Acknowledgements • The creators of ds9 • Chandra x-ray observatory • Special thanks to Mark Hartman, Irene Porro and our mentor, Mike Nowak. • And, of course, the audience