Spitzer Microlensing Parallax for OGLE-2017-BLG-0896 Reveals a Counter-Rotating Low-Mass Brown Dwarf (2018)
AuthorsShvartzvald Y, Yee JC, Skowron J, Lee C-U, Udalski A, Novati SC, Bozza V, Beichman CA, Bryden G, Carey S, Gaudi BS, Henderson CB, Zhu W, Bachelet E, Bolt G, Christie G, Maoz D, Natusch T, Pogge RW, Street RA, Tan T-G, Tsapras Y, Pietrukowicz P, Soszyński I, Szymański MK, Mróz P, Poleski R, Kozłowski S, Ulaczyk K, Pawlak M, Rybicki KA, Iwanek P, Albrow MD, Cha S-M, Chung S-J, Gould A, Han C, Hwang K-H, Jung YK, Kim D-J, Kim H-W, Kim S-L, Lee D-J, Lee Y, Park B-G, Ryu Y-H, Shin I-G, Zang W, Dominik M, Helling C, Hundertmark M, Jørgensen UG, Longa-Peña P, Lowry S, Sajadian S, Burgdorf MJ, Campbell-White J, Ciceri S, Evans DF, Fujii YI, Hinse TC, Rahvar S, Rabus M, Skottfelt J, Snodgrass C, Southworth Jshow all
The kinematics of isolated brown dwarfs in the Galaxy, beyond the solar neighborhood, is virtually unknown. Microlensing has the potential to probe this hidden population, as it can measure both the mass and five of the six phase-space coordinates (all except the radial velocity) even of a dark isolated lens. However, the measurements of both the microlens parallax and finite-source effects are needed in order to recover the full information. Here, we combine Spitzer satellite parallax measurement with the ground-based light curve, which exhibits strong finite-source effects, of event OGLE-2017-BLG-0896. We find that the lens is a ∼19MJ isolated brown dwarf. This is the lowest isolated-object mass measurement to date, only slightly above the common definition of a free-floating planet. The brown dwarf is located at ∼4 kpc toward the Galactic bulge, but with proper motion in the opposite direction of disk stars, possibly moving in the Galactic plane. While it is possibly a halo brown dwarf, it might also represent a different, unknown population.
Keywordsastro-ph.SR; gravitational lensing: micro — Galaxy: bulge
ANZSRC Fields of Research02 - Physical Sciences::0201 - Astronomical and Space Sciences::020110 - Stellar Astronomy and Planetary Systems
02 - Physical Sciences::0201 - Astronomical and Space Sciences::020102 - Astronomical and Space Instrumentation