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Other Science from Microlensing Surveys I or

Explore the challenges and solutions in microlensing surveys, including parallax, limb darkening, and planet detection effects. Learn to analyze source stars' characteristics and uncover stellar probes' potentials. Dive into the world of microlensing with this informative talk overview.

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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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