Udalski ARyu Y-HSajadian SGould AMróz PPoleski RSzymański MKSkowron JSoszyński IKozłowski SPietrukowicz PUlaczyk KPawlak MRybicki KIwanek PAlbrow MDChung S-JHan CHwang K-HJung YKShin I-GShvartzvald YYee JCZang WZhu WCha S-MKim D-JKim H-WKim S-LLee C-ULee D-JLee YPark B-GPogge RWBozza VDominik MHelling CHundertmark MJørgensen UGLonga-Peña PLowry SBurgdorf MCampbell-White JCiceri SEvans DJaimes RFFujii YIHaikala LKHenning THinse TCMancini LPeixinho NRahvar SRabus MSkottfelt JSnodgrass CSouthworth JEssen CV2018-04-232018-04-232018http://hdl.handle.net/10092/15191We 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).enastro-ph.EPgravitational lensing: microplanetary systemsJournal Article2018-03-05Fields of Research::51 - Physical sciences::5101 - Astronomical sciences::510109 - Stellar astronomy and planetary systemsField of Research::02 - Physical Sciences::0201 - Astronomical and Space Sciences::020108 - Planetary Science (excl. Extraterrestrial Geology)