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Microlensing with CCDs

This presentation by Philip Yock from the University of Auckland at the NZ-Australia Semiconductor Instrumentation Workshop in June 2004 discusses the principles and significance of microlensing in astronomical observations. It emphasizes how CCD technology enables precision measurements of celestial bodies, facilitates the detection of extra-solar planets, and captures light curves crucial for deciphering lens geometries. Key examples of microlensing events, such as MACHO 98-BLG-35, showcase the capabilities of current CCD arrays in monitoring stars across vast cosmic distances.

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Microlensing with CCDs

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  1. Microlensing with CCDs Philip Yock University of Auckland, NZ http://www.physics.auckland.ac.nz/moa/index.html NZ-Australia Semiconductor Instrumentation Workshop, June 2004

  2. Why microlensing? – Why CCDs? • Precision measurements can be made on stars • Highest precision measurements on planets • Many stars must be monitored – CCDs essential

  3. Basics of microlensing Lens Source Earth EINSTEIN RING

  4. Demonstration with a glass lens • CourtesySidney Liebes, Princeton

  5. Typical astronomical dimensions 10,000 ly 20,000 ly 2 AU 1 mas

  6. Detectable in the Galactic Bulge

  7. The need for CCDs Required separation ~ 1mas, but typical separation ~1as “No chance of observing this phenomenon” - Einstein (1936)

  8. Typical CCD arrays MOA-II MOA-I 24 million pixels 80 million pixels

  9. Ground versus space MACHO 98-BLG-35 HST MOA Difference imaging essential from the ground

  10. Light curve Typical transverse velocity ~ 200 km/sec

  11. Light curve Liebes-Paczynski light curve versus data

  12. Planetary microlensing Planets perturb the Einstein ring

  13. Comparison with Rutherford scattering

  14. Planetary perturbations Neptune at 2 AU Perturbation ~ 5%

  15. Neptune at ~ 2AU at different 

  16. Earth at ~ 2 AU Perturbation ~ 0.5%

  17. Two planets Detectable if  > 20°

  18. MACHO 98-BLG-35  Magnification = 80  Possible Earth-mass planet

  19. MOA 2003-BLG-32/OGLE 2003-BLG-219 Magnification = 520 e-4 = Neptune e-5 = Earth e-6 = Mars (preliminary)

  20. MOA 2003-BLG-32/OGLE 2003-BLG-219 e-4 = Neptune e-3 = Saturn

  21. Binary lens A “caustic” is formed

  22. MOA 2002-BLG-33 MOA 0.6m 480 exp Wise 1m 20 exp MDM 2.4m 260 exp EROS 1m 186 exp Boyden 1.5m 473 exp HST 2.4m 5 exp

  23. MOA 2002-BLG-33  The light curve determines the lens geometry  The lens profiles the source

  24. MOA 2002-BLG-33  Caustic crossed in 15.6 hours  Profiles obtained, on entry and on exit

  25. Stellar profile MOA 2002-BLG33 Another star  Stellar atmosphere theory confirmed  Precision comparable to that of the VLTI - Very Large Telescope Interferometer at ESO

  26. Conclusions •  Stellar gravitational lenses exist •  Extra-solar planets detectable •  Stars resolvable •  Nature helpful!

  27. 64 million dollar question Is SU(3)SU(2)U(1) being studied on other planets?

  28. Acknowledgements •  Ian Bond & Nick Rattenbury •  John Hearnshaw & Yasushi Muraki •  Colleagues in MOA, MACHO, EROS, OGLE, FUN, PLANET •  Marsden Fund, Department of Education of Japan

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