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Period Analysis of Eclipsing Binaries

Period Analysis of Eclipsing Binaries. Patricia Skelton MSc Prof. D.P. Smits UNISA . SKA Postgraduate Bursary Conference The Wallenberg Centre, sti s 5 December 2009. W UMa -type Variable Stars. Common Envelope Binaries P < 1 day. Spectral Range A – K

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Period Analysis of Eclipsing Binaries

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  1. Period Analysis of Eclipsing Binaries Patricia Skelton MSc Prof. D.P. Smits UNISA SKA Postgraduate Bursary Conference The Wallenberg Centre, stis 5 December 2009

  2. W UMa-type Variable Stars • Common Envelope • Binaries • P < 1 day • Spectral Range A – K • ΔK ≈ few hundred • degrees

  3. W UMa-type Variable Stars

  4. Sources of Data All Sky Automated Survey Wide Angle Search for Planets ASAS Enclosure Las Campanas, Chile SuperWASP South SAAO, Sutherland

  5. Sources of Data SuperWASP ASAS

  6. Period Analysis • Changes in orbital period: may be a result of mass transfer or LTTE • O – C diagram used to determine if period is changing

  7. Var(Tmin)

  8. O – C Diagram: Part 1 • Used TminandASAS P to construct O – C diagram • Correct period: O – C values scattered about O – C = 0 • Positive or Negative slope – Different period P = 0.313670d • (O – C) = Tmin – T0 – εP

  9. Least Squares Analysis • Analysis returns a new Pand T0 • Obtain linear or quadratic ephemeris: • Tmin = T0 + εP • Tmin = T0 + εP + aε2 • Constructed new O – C diagrams

  10. O – C diagram: Part 2 Linear Ephemeris : P = 0.31366012 d Σ(O – C)2 = 3.22 × 10-6 Quadratic Ephemeris : P = 0.3136592 d Σ(O – C)2 = 2.94 × 10-6

  11. ASAS 002328-2041.8

  12. Way Forward - PhD • Continue monitoring stars of interest • Automate the procedures of the period analysis • Extend project to a multi-wavelength study – Infrared, X-ray and Radio • Stars modelled with stellar spots – potential targets for observations with the SKA

  13. THANK YOU!

  14. Summary - MSc • Modelled selected ASAS contact binary stars • 1 shallow-contact, 1 deep-contact • Stellar spots improved models of 2 stars • Period analysis of 8 contact binaries • 5 systems – period decreased • 3 systems – period increased

  15. Minima Influenced by Spots • Stellar spots can affect shapes of minima.

  16. Step 1: Time of minimum • Small phase interval, minimum parabolic in shape • Second-order polynomial:

  17. Minima Influenced By Spots • Stellar spots can affect shapes of minima. • Asymmetrical minima can be useful when modelling systems. • Help to identify systems that are magnetically active.

  18. ASAS 150452-3757.7 ASAS 150934-3348.5

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