The mass of the free-floating planet MOA-2011-BLG-274L

1. The mass of the free-floating planet MOA-2011-BLG-274L Philip Yock 18th International Conference on Gravitational Lensing LCOGT, Santa Barbara January 2014

2. Free-floating planets? Sidney Liebes, “Gravitational Lenses”, Physical Review, 10 Feb 1964:- “There appears little likelihood that unbound planet-sized bodies floating about the galaxy would contribute significantly to the frequency of detectable events. For, the associated pulses would be so weak and infrequent and of such fleeting duration – perhaps a few hours – as to defy detection.” Lens 1000 × lighter than normal, therefore ring 30 × smaller, magnification 30 × less and duration 30 × shorter

3. 51 years later at Farm Cove Observatory, Auckland, NZ Fleeting duration Flat top Free-floater? Choi et al ApJ 751, 41 Mass measurement? Terrestrial parallax? Australia & NZ

4. Six telescopes 2 days 4 hours

5. Source star (V-I)s,0 = 0.76 ± 0.10 and Is,0 = 17.96 ± 0.1 Hence rs = 1.47 ± 0.24 rsolar, MI = 3.47 ± 0.20 and Teff = 5700 ± 200 K

6. Marginalization plots Provide accuracies of umin, ρ, t0 and tE in the usual manner

7. Air-mass effects Farm Cove (Auckland) PEST (Perth) 14º ± 6º 56º - 31º

8. Finite source size ρ = θs/θE = 0.01 is large, but θs is normal, hence θE small and the lens-mass is low tE = 3 days also suggests θE is small and the lens-mass is low BUT the distance to the lens is needed

9. Comparison with Choi et al ApJ 751, 41 (2012) } ρ large tE small µ large Suggest the mass of the lens is low But we need to know the distance the distance to the lens to determine its mass

10. Terrestrial parallax Terrestrial parallax is large, implying the lens is nearby, the Einstein ring is small and the lens-mass is low

11. Negative umin umin > 0 umin < 0 πE ~ 13 πE ~ 8 δκ2 ~ 9 δκ2 ~ 6

12. Cooler and hotter source star 5500K 5700K 5900K πE ~ 12 πE ~ 13 πE ~ 13 δκ2 ~ 9 δκ2 ~ 9 δκ2 ~ 10

13. Lens distance and mass (Preliminary calculations from on-line reduction of the MOA data)

14. Trajectory Impact parameter = umin × rE (at observer plane) = 5.8 Earth radii Direction = 12º west of north (Second solution to the west)

15. Parallax from single telescopes Multi telescope solution Single telescope fits Free of systematic effects (Preliminary analysis with on-line reduction of MOA images)

16. Orbital parallax distorts the light curve (4 second effect)

17. Host star? Caustic formed by a planet and a distant star If the caustic fits inside the source star the source star is undetectable. No host within 37 AU

18. Exomoons? δκ2 = 110 for moon detection Exclusion region slightly larger than found by Choi et al. Above is for mass ratio 3×10-4. Ganymede not detectable.

19. Event rate A couple of transit events are detected per year with normal lenses and main sequence source stars Hence a few transit events should occur per year with free-floating planets and main sequence sources Duration is shorter, magnification is less, and the lens must be nearby for a mass measurement. Detection rate will be low - a challenge for LCOGT But can be done simultaneously while monitoring high mag events:-

20. Thanks