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Other Science from Microlensing Surveys I or

Other Science from Microlensing Surveys I or. Microlenses as Stellar Probes By Jonathan Devor. Overview of the talk. The problem with “vanilla” microlensing “Non-vanilla” microlensing effects: (1) Parallax (2) Limb darkening (3) A planet around the lens

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Other Science from Microlensing Surveys I or

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  1. Other Science from Microlensing Surveys Ior Microlenses as Stellar Probes By Jonathan Devor

  2. Overview of the talk • The problem with “vanilla” microlensing • “Non-vanilla” microlensing effects: (1) Parallax (2) Limb darkening (3) A planet around the lens (4) A planet around the source

  3. The problem with vanilla Paczynski curves: 0.1 • Observable parameters: • Time of max (t0) • Time scale (tE) • Max magnification 0.3 0.5 Not enough information in “vanilla” lensing events. PLANET data + fits

  4. …now add some sprinkles and fudge EROS BLG-2000-5 tstar tE

  5. The solution Dsource Rsource θsource Source star characteristics: {color, magnitude and spectrum} Scale of source: Relative proper motion (lens-source): Dlens Mlens Scale of lens: Rlens Astrometry:

  6. Astrometry of weighted mean position Lens at origin Source at origin

  7. SIM: “Will determine the positions and distances of stars several hundred times more accurately than any previous program.”

  8. (1) Parallax Centroid path images Astrometric path centroid source

  9. Observations: OGLE 99-BLG-32

  10. (2) Limb darkening • You see deeper into a star at the center of it’s disk, then you see at it’s edge. Cool Hot • The limb of a stellar disk is almost always redder/dimmer than the center.

  11. Chromatic Lensing

  12. Observations of Hα absorption line equivalent widths

  13. Binary Lenses – brief recap

  14. Choose the line of sight

  15. Observation: EROS BLG-2000-5

  16. (3) Planet around the lens

  17. …animated

  18. Planet inside the Einstein radius

  19. …now take a closer look

  20. Changing the location of the planet

  21. (4) A planet around the source Source: G0 V star at 8 kpc

  22. Planet finding comparison

  23. Summary • Very little information can be learned from purely “vanilla” lensing. You need other effects to break the degeneracy and pin down the system’s physics. • The parallax effect occurs in all cases, but can only be readily detected in very long time scale events (~year) and when the lens is relatively nearby. • Through lensing it is possible to learn about source star’s limb darkening, surface features and planets. Unfortunately the latter is very difficult to do. • Planets around the lensing star should be far easier to detect, unfortunately we won’t be able to learn that much about them. • A microlensing event only happens once, so “real-time astronomy” is required to gather enough data before it’s gone. (You snooze- you loose)

  24. References • Afonso, C., et al., Photometric constraints on microlens spectroscopy of EROS-BLG-2000-5, Astronomy and Astrophysics, v.378, p.1014-1023 (2001) • An, J. H., First Microlens Mass Measurement: PLANET Photometry of EROS BLG-2000-5, The Astrophysical Journal, Volume 572, Issue 1, pp. 521-539 (2002) • Cassan, A., Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlense H alpha line, astro-ph/0401071 (2004) • Evans, N. W., The First Heroic Decade of Microlensing, astro-ph/0304252 (2002) • Gaudi, B. S., Microlensing Searches for Extrasolar Planets: Current Status and Future Prospects, astro-ph/0207533 (2002) • Gaudi, B. S. et al., Microlensing Constraints on the Frequency of Jupiter-Mass Companions: Analysis of 5 Years of PLANET Photometry, The Astrophysical Journal, Volume 566, Issue 1, pp. 463-499 (2002) • Gaudi, B. S. et al., Angular Radii of Stars via Microlensing, The Astrophysical Journal, Volume 586, Issue 1, pp. 451-463 (2003) • Gould, A., Applications of Microlensing to Stellar Astrophysics, The Publications of the Astronomical Society of the Pacific, Volume 113, Issue 786, pp. 903-915 (2001) • Graff, D. S., and Gaudi, B. S., Direct Detection of Large Close-in Planets around the Source Stars of Caustic-crossing Microlensing Events, The Astrophysical Journal, Volume 538, Issue 2, pp. L133-L136 (2000) • SIM homepage: http://planetquest.jpl.nasa.gov/SIM/sim_index.html • The animations were created by Scott Gaudi

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