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

Free-floating planets? Sidney Liebes, “Gravitational Lenses”, Physical Review, 10 Feb 1964:- Lens 1000 × lighter than normal, therefore ring 30 × smaller, magnification 30 × less and duration 30 × shorter “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.”

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

Six telescopes 2 days 4 hours

Source star (V-I) s,0 = 0.76 ± 0.10 and I s,0 = ± 0.1 Hence r s = 1.47 ± 0.24 r solar, M I = 3.47 ± 0.20 and T eff = 5700 ± 200 K

Marginalization plots Provide accuracies of u min, ρ, t 0 and t E in the usual manner

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

Finite source size ρ = θ s /θ E = 0.01 is large, but θ s is normal, hence θ E small and the lens-mass is low t E = 3 days also suggests θ E is small and the lens-mass is low BUT the distance to the lens is needed

Comparison with Choi et al ApJ 751, 41 (2012) ρ large t E 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

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

Negative umin u min > 0 u min < 0 π E ~ 13 π E ~ 8 δκ 2 ~ 9 δκ 2 ~ 6

Cooler and hotter source star 5500K 5700K 5900K π E ~ 12 π E ~ 13 π E ~ 13 δκ 2 ~ 9 δκ 2 ~ 9 δκ 2 ~ 10

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

Trajectory Impact parameter = u min × r E (at observer plane) = 5.8 Earth radii Direction = 12 º west of north (Second solution to the west)

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

Orbital parallax distorts the light curve (4 second effect)

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

Exomoons? δκ 2 = 110 for moon detection Exclusion region slightly larger than found by Choi et al. Above is for mass ratio 3× Ganymede not detectable.

Event rate A couple of transit events are detected per year with normal lenses and main sequence source stars 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 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. 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 Detection rate will be low - a challenge for LCOGT But can be done simultaneously while monitoring high mag events:- But can be done simultaneously while monitoring high mag events:-

Thanks