OGLE-2017-BLG-1434Lb: Eighth q < 1 * 10^-4 Mass-Ratio Microlens Planet Confirms Turnover in Planet Mass-Ratio Function (2018)
AuthorsUdalski A, Ryu Y-H, Sajadian S, Gould A, Mróz P, Poleski R, Szymański MK, Skowron J, Soszyński I, Kozłowski S, Pietrukowicz P, Ulaczyk K, Pawlak M, Rybicki K, Iwanek P, Albrow MD, Chung S-J, Han C, Hwang K-H, Jung YK, Shin I-G, Shvartzvald Y, Yee JC, Zang W, Zhu W, Cha S-M, Kim D-J, Kim H-W, Kim S-L, Lee C-U, Lee D-J, Lee Y, Park B-G, Pogge RW, Bozza V, Dominik M, Helling C, Hundertmark M, Jørgensen UG, Longa-Peña P, Lowry S, Burgdorf M, Campbell-White J, Ciceri S, Evans D, Jaimes RF, Fujii YI, Haikala LK, Henning T, Hinse TC, Mancini L, Peixinho N, Rahvar S, Rabus M, Skottfelt J, Snodgrass C, Southworth J, Essen CVshow all
We report the discovery of a cold Super-Earth planet (m_p=4.4 +/- 0.5 M_Earth) orbiting a low-mass (M=0.23 +/- 0.03 M_Sun) M dwarf at projected separation a_perp = 1.18 +/- 0.10 AU, i.e., about 1.9 times the snow line. The system is quite nearby for a microlensing planet, D_Lens = 0.86 +/- 0.09 kpc. Indeed, it was the large lens-source relative parallax pi_rel=1.0 mas (combined with the low mass M) that gave rise to the large, and thus well-measured, "microlens parallax" that enabled these precise measurements. OGLE-2017-BLG-1434Lb is the eighth microlensing planet with planet-host mass ratio q < 1 * 10^-4. We apply a new planet-detection sensitivity method, which is a variant of "V/V_max", to seven of these eight planets to derive the mass-ratio function in this regime. We find dN/d(ln q) ~ q^p, with p = 1.05 (+0.78,-0.68), which confirms the "turnover" in the mass function found by Suzuki et al. relative to the power law of opposite sign n = -0.93 +/- 0.13 at higher mass ratios q >~ 2 * 10^-4. We combine our result with that of Suzuki et al. to obtain p = 0.73 (+0.42,-0.34).
Keywordsastro-ph.EP; gravitational lensing: micro; planetary systems
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::020108 - Planetary Science (excl. Extraterrestrial Geology)