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Microlensing Working Group Review

Microlensing Working Group Review. David Bennett (Notre Dame ) . MicroFUN M icrolensing F ollow- U p N etwork. Features of Microlensing. General consensus on forward directions . Exoplanet Forum + Pale Blue Dot Reviews Two (and only two) paths forward Both Recommended by ExoPTF

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Microlensing Working Group Review

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  1. Microlensing Working Group Review David Bennett (Notre Dame) MicroFUN Microlensing Follow-Up Network

  2. Features of Microlensing • General consensus on forward directions. • Exoplanet Forum + Pale Blue Dot Reviews • Two (and only two) paths forward • Both Recommended by ExoPTF • Ground based 1.5-2m wide-FOV telescope network • 1-5 years, ~$20M • Now funded: Korea Microlensing Telescope Network (KMTNet) • Frequency of planets  1 M beyond the snow line. • Space based, 5-10 years, ~$300M + Launch • Complete census of planets with mass greater than Mars and a 0.5 AU, including habitable planets. • Possible joint Exoplanet + Dark Energy mission 

  3. Microlensing Discoveries vs. Other Techniques • Microlensing discoveries in red • Doppler discoveries in black • Transit discoveries shown as blue squares • Direct detection, timing and astrometry are magenta,green, and orange triangles • Microlensing opens a new window on exoplanets at 1-5 AU • Sensitivity approaching 1 Earth-mass Most planets here!

  4. Ground-based µlensing surveys probe planets with M 1 M beyond the snow-line. • A space-based survey will provide a complete census of planetary systems with mass greater than Mars and a 0.5 AU (from 0 to  with Kepler), including habitable planets.

  5. The Physics of Microlensing • Foreground “lens” star + planet bend light of “source” star • Multiple distorted images • Only total brightness change is observable • Sensitive to planetary mass • Low mass planet signals are rare – not weak • Stellar lensing probability ~a few 10-6 • Planetary lensing probability ~0.001-1 depending on event details • Peak sensitivity is at 2-3 AU: the Einstein ring radius, RE Einstein’s telescope

  6. Microlensing Target Fields are in the Galactic Bulge Galactic center Sun 8 kpc 1-7 kpc from Sun Light curve Source star and images Lens star and planet Telescope 10s of millions of stars in the Galactic bulge in order to detect planetary companions to stars in the Galactic disk and bulge.

  7. How Low Can We Go? Limited by Source Size angular Einstein radius angular source star radius (Bennett & Rhie 1996) For E  * : low-mass planet signals are rare and brief, but not weak Mars-mass planets detectable if solar-type sources can be monitored!

  8. NextGen Lensing Survey • For significant sensitivity increase over current Alert & Follow-up effort • Requirements to detect ~3 (cold) Earth-mass planets per year: • Continuous monitoring of all ~800 microlensing events detected per year • Monitor ~16 square degrees of the Galactic bulge continuously with ~10 minute sampling using 1-2m class telescopes, distributed longitudinally throughout the southern hemisphere. • Large FOV (2-4 square degree) cameras needed.

  9. Microlensing Telescope Locations KMTNet High Magnification Alert!! KMTNet FUN Network CTIO Survey Telescopes PLANET Network KMTNet MOA OGLE

  10. Hardware Funded Internationally • MOA-II (NZ, currently operating) • 1.8m telescope, 2.18 sq. degree camera • MOA-III upgrade to 10 sq. degree camera proposed • OGLE -IV (Chile, 2009) • 1.3m telescope, upgrade to 1.4 sq. degree camera • KMTNet (South Africa, Chile, Australia) • 1.6m telescopes, 4 sq. degree cameras • Funded in Dec., 2008 ExoPTF: “Recommendation A. II. 1 Increase dramatically the efficiency of a ground-based microlensing network by adding a single 2 meter telescope.” 

  11. Lens System Properties • Einstein radius : E= *tE/t* and projected Einstein radius, • * = the angular radius of the star • from the microlensing parallax effect (due to Earth’s orbital motion).

  12. Finite Source Effects & Microlensing Parallax Yield Lens System Mass • If only E or is measured, then we have a mass-distance relation. • Such a relation can be solved if we detect the lens star and use a mass-luminosity relation • This requires HST or ground-based adaptive optics • With E, , and lens star brightness, we have more constraints than parameters mass-distance relations: Space-based parallaxes using Solar System Science Spacecraft?

  13. Double-Planet Event: OGLE-2006-BLG-109 • 5 distinct planetary light curve features • OGLE alerted 1st feature as potential planetary signal • High magnification • Feature #4 requires an additional planet • Planetary signals visible for 11 days • Features #1 & #5 require the orbital motion of the Saturn-mass planet OGLE alert FUN, OGLE, MOA & PLANET

  14. OGLE-2006-BLG-109 Light Curve Detail • OGLE alert on feature #1 as a potential planetary feature • FUN (Gaudi) obtained a model approximately predicting features #3 & #5 prior to the peak • But feature #4 was not predicted - because it is due to the Jupiter - not the Saturn Gaudi et al (2008) published in Science

  15. OGLE-2006-BLG-109 Light Curve Features • The basic 2-planet nature of the event was identified during the event, • But the final model required inclusion of orbital motion, microlensing parallax and computational improvements (by Bennett).

  16. OGLE-2006-BLG-109Lb,c Caustics Curved source trajectory due to Earth’s orbital motion Planetary orbit changes the caustic curve - plotted at 3-day intervals Feature due to Jupiter

  17. OGLE-2006-BLG-109 Source Star The model indicates that the source is much fainter than the apparent star at the position of the source. Could the brighter star be the lens star? Apparent source In image source from model

  18. OGLE-2006-BLG-109Lb,c Host Star • OGLE images show that the source is offset from the bright star by 350 mas • B. Macintosh: Keck AO images resolve lens+source stars from the brighter star. • But, source+lens blend is 6 brighter than the source (from CTIO H-band light curve), so the lens star is 5 brighter than source. • H-band observations of the light curve are critical because the lens and source and not resolved • Planet host (lens) star magnitude H  17.17 • JHK observations will help to constrain the extinction toward the lens star

  19. Implications of Light Curve Model • Apply lens brightness constraint: HL 17.17. • Correcting for extinction: HL0= 16.93  0.25 • Extinction correction is based on HL-KL color • Error bar includes both extinction and photometric uncertainties • Lens system distance: DL= 1.54  0.13 kpc • Other parameter values: • “Jupiter” mass: mb= 0.73 0.06MJup semi-major axis: • “Saturn” mass: mc= 0.27  0.03MJup= 0.90 MSatsemi-major axis: • “Saturn” orbital velocity vt = 9.5  0.5 km/sec eccentricity inclination i= 63  6

  20. Current Event: MOA-2009-BLG-266 • Planet discovered by MOA on Sept. 11, 2009 • Low-mass planet • Probably • Hope to get mass measurement from Deep Impact (now EPOXI) Spacecraft

  21. Space-Based Microlensing Parallax 2004: study LMC microlensing w/ DI imaging (proposed) 2009: Geometric exoplanet and host star mass measurements with DI

  22. MPF Ground-based confusion, space-based resolution CTIO HST • Space-based imaging needed for high precision photometry of main sequence source stars (at low magnification) and lens star detection • High Resolution + large field + 24hr duty cycle => Microlensing Planet Finder (MPF) • Space observations needed for sensitivity at a range of separations and mass determinations

  23. Lens Star Identification from Space Simulated HST images: ML= 0.08 M • Lens-source proper motion gives E = reltE • rel= 8.40.6 mas/yr for OGLE-2005-BLG-169 • Simulated HST ACS/HRC F814W (I-band) single orbit image “stacks” taken 2.4 years after peak magnification • 2 native resolution • also detectable with HST WFPC2/PC & NICMOS/NIC1 • Stable HST PSF allows clear detection of PSF elongation signal • A main sequence lens of any mass is easily detected (for this event) ML= 0.35 M ML= 0.63 M binned raw image PSF subtracted

  24. The Microlensing Planet Finder(MPF) David Bennett, PI Ed Cheng, Deputy PI NASA/GSFC Management Lockheed Martin, prime contractor

  25. MPF Complements Kepler Figures from B. MacIntosh of the ExoPlanet Task Force

  26. MPF’s Predicted Discoveries Expected MPF planet detections if each lens system has a “solar system analog” planetary system with the same star-planet separations and mass ratios as our own planetary system. The number of expected MPF planet discoveries as a function of planet mass.

  27. From the ExoPlanet Task Force: • “Recommendation B. II. 2 Without impacting the launch schedule of the astrometric mission cited above, launch a Discovery-class space-based microlensing mission to determine the statistics of planetary mass and the separation of planets from their host stars as a function of stellar type and location in the galaxy, and to derive  over a very large sample.

  28. Summary  • Ground-based Next-Generation Survey: ~ $ 30M • Hardware funded by Japan, Poland, and Korea • Frequency of planets  1 M beyond the snow line. • Test planet formation theories. • Either: Space-based Microlensing Mission: +$300M + launch • Complete census of planets with mass greater than Mars and a 0.5 AU. • Sensitivity to all Solar System planet analogs except Mercury. • Demographics of planetary systems - tests planet formation theories. • Detect “outer” habitable zone (Mars-like orbits) where detection by imaging is easiest. • Can find moons and free floating planets. • Or: Joint lensing/Dark Energy Mission +$100M—$200M? • see Beaulieu’s talk • Total cost to “Exoplanet Community”: $105M(?)—$405M

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