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Periodic Variables and Gyrochronology in NGC2301

Periodic Variables and Gyrochronology in NGC2301. Tuguldur Sukhbold. Dr.Steve Howell NOAO. Howell et. al. (2005) , Tonry et.al.(2005) Search for Planetary Occultation in Open Cluster NGC2301. Open Cluster . Formed in the same Gas cloud Loosely Gravitationaly Bound Few 1000 stars

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Periodic Variables and Gyrochronology in NGC2301

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  1. Periodic Variables and Gyrochronology in NGC2301 TuguldurSukhbold

  2. Dr.Steve Howell NOAO Howell et. al. (2005) , Tonry et.al.(2005) Search for Planetary Occultation in Open Cluster NGC2301

  3. Open Cluster • Formed in the same Gas cloud • Loosely Gravitationaly Bound • Few 1000 stars • Few Hundred My

  4. Why “Open”?

  5. NGC2301

  6. Howell et.al.(2005)

  7. University of Hawaii 88” (2.2m) 14 days

  8. Planetary Occultation

  9. Light Curve

  10. Light Curve Why non-continuous?

  11. Phase Plot “Raw” Light Curve Phased Light Curve

  12. Stat.Analysis of 4078starsTonry et.al.(2005) • Prob.periodicity ; Prob.exoplanet….

  13. Goal 1: Find Eclipsing Binaries (EBs) • So that I can measure the distance

  14. What is EB

  15. Contact EB

  16. How can I measure the Distance? • Take Spectra => • Measure Doppler Shifts => • Derive Radial Velocity Curve => • Find Mass, Radius of Component Stars => • Distance

  17. Radial Velocity Curve M=m-5(logDL-1) Berg et.al.(2001)

  18. Pool of data of 4078

  19. EBs are periodic variables => find Periodic Variables first and then look for EBs in the list

  20. Used prob.periodicity P=1-Pf Decreasing Probability of Periodicity ------------------------------->

  21. 2 Rejected Stars Variables, but not periodic on the time-sclale of 14day observing run

  22. EB ~ Unequal Minima

  23. Found 5 candidates!!! :D SE292

  24. Notice!

  25. Periods are Extremely short!!! • 0.24-0.34days ~ 6-8hours! • Same Mass, Circular Orbit: Crude Radial Velocity Estimation: ~200km/sec!!!

  26. Assuming real EBs are they real Members?

  27. CMD isochrones, Yi et.al.(2003)

  28. CMD of NGC 2301 Yale Isochrones, Yi et.al.(2003)

  29. Grubissich& Prugathofer (1962) Cluster Apparent Radius ~18 arcminutes

  30. Goal 2: Gyrochronology • How old is the cluster? • How “well” does Gyrochronology work?

  31. Skumanich Law Andrew Skumanich, 1972

  32. Sydney Barnes (2003)

  33. Empirical Isochrones • I sequence <=> • C sequence

  34. Population (time)

  35. Meibom et.al.(2008) – M35

  36. Color Conversion (B-V)  (B-R) • Values from Cox (2000)

  37. Period – Color Plane for NGC2301 200My

  38. Filtering: • 7 stars (B-R) < 1.00 • 5 stars EBs • 10 stars Pulsators

  39. Left with 116 stars: Still mess…

  40. Previously Determined Ages • ~164My – Unknown Method /WEBDA/ • 250+/-45My – Kim et.al.(2001) • ~205My – Kharchenko et.al.(2006)

  41. Isochrones of Previous ages:

  42. What can I do? 1) Fit Isochrones on subjectively defined sequence regions 2) Direct application of Skumanich Relation

  43. 1. Isochrone Fits • Only on I sequence, because contamination in C sequence ------------------------------ PNyquist 

  44. P=5.5(B-R)-4.5

  45. P=6.5(B-R)-4.5

  46. PN

  47. Grubissich& Prugathofer (1962) Cluster Apparent Radius ~18 arcminutes

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