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Modelling of W UMa -type Variable Stars

Modelling of W UMa -type Variable Stars. Patricia Skelton MSc UNISA Prof. Derck Smits SKA Postgraduate Bursary Conference The Wallenberg Centre, sti s 1 – 5 December 2008. Over-Contact System. Properties of W UMa-type Stars. Overcontact binary: Common Envelope binary

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Modelling of W UMa -type Variable Stars

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  1. Modelling of W UMa-type Variable Stars Patricia Skelton MSc UNISA Prof. Derck Smits SKA Postgraduate Bursary Conference The Wallenberg Centre, stis 1 – 5 December 2008

  2. Over-Contact System

  3. Properties of W UMa-type Stars Overcontact binary:Common Envelope binary Period < 1 day Spectral Range: A - K ΔT approximately a few hundred degrees Subclasses : A-Type and W-Type

  4. ASAS • Las Campanas Observatory, Chile • 7cm aperture telescope • Observe once every 1 – 3 days • 50,000+ variable stars discovered • Over 5000 are EW stars

  5. SuperWASP Monitor sky for planetary transits Two robotic observatories: North: La Palma, South: SAAO Eight wide angle cameras. Camera aperture 11.1cm Observe on a daily basis

  6. ASAS WASP

  7. PHOEBE

  8. Stars Of Interest Stars that display period changes Stars that may be magnetically active: Search for radio emission Previous surveys for radio emission used distance as a search criterion. Flare detected from VW Cep. Goal: Evidence for magnetic activity in light curves.

  9. The O’Connell Effect • Maxima Different Height • Magnetic Activity: Spots

  10. Flux Changes ASAS 133246-1745.5 Decrease in flux ASAS 062426-2044.9 Increase in flux

  11. Flux Changes ASAS 002328-2041.8 ASAS data WASP data Combined increase & decrease in flux

  12. Interesting star ASAS 002328-2041.8

  13. Period Changes ASAS Data WASP Data

  14. Unanswered Questions • EW stars: How do they form and what do they become? • Complex pattern of period changes • Common Envelope: Uniform temperature. Why?

  15. Future Research • Period changes: O-C diagram • APT observations • Radial velocity measurements: Mass ratios • Surveys for radio emission from spots: VLA, SKA

  16. Image adapted from Binary Maker 3

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