OGLE-2017-BLG-1434Lb: Eighth q<1×10-4 mass-ratio microlens planet confirms turnover in planet mass-ratio function

A. Udalski, Y. H. Ryu, S. Sajadian, A. Gould, P. Mróz, R. Poleski, M. K. Szymanski, J. Skowron, I. Soszynski, S. Kozlowski, P. Pietrukowicz, K. Ulaczyk, M. Pawlak, K. Rybicki, P. Iwanek, M. D. Albrow, S. J. Chung, C. Han, K. H. Hwang, Y. K. JungI. G. Shin, Y. Shvartzvald, J. C. Yee, W. Zang, W. Zhu, S. M. Cha, D. J. Kim, H. W. Kim, S. L. Kim, C. U. Lee, D. J. Lee, Y. Lee, B. G. Park, R. W. Pogge, V. Bozza, M. Dominik, C. Helling, M. Hundertmark, U. G. Jørgensen, P. Longa-Peña, S. Lowry, M. Burgdorf, J. Campbell-White, S. Ciceri, D. Evans, R. Figuera Jaimes, Y. I. Fujii, L. K. Haikala, T. Henning, T. C. Hinse, L. Mancini, N. Peixinho, S. Rahvar, M. Rabus, J. Skottfelt, C. Snodgrass, J. Southworth, C. Von Essen

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We report the discovery of a cold Super-Earth planet (mp=4.4±0.5 M) orbiting a low-mass (M=0.23±0.03) M dwarf at projected separation a=1.18±0.10 a.u., i.e., about 1.9 times the distance the snow line. The system is quite nearby for a microlensing planet, DL=0.86±0.09 kpc. Indeed, it was the large lens-source relative parallax πrel=1.0 mas (combined with the low mass M) that gave rise to the large, and thus well-measured, "microlens parallax" πE∝(πrel/M)1/2 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/Vmax", to seven of these eight planets to derive the mass-ratio function in this regime. We find dN/d lnq ∝ qp, 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.
Original languageEnglish
Pages (from-to)1-42
Number of pages42
JournalActa Astronomica
Issue number1
Publication statusPublished - 2018


  • Gravitational lensing: micro
  • Planetary systems

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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