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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,
and P. Mróz, R. Poleski, M.K. Szymański, J. Skowron, I. Soszyński, S. Kozłowski, P. Pietrukowicz, K. Ulaczyk, M. Pawlak, K. Rybicki, P. Iwanek, (OGLE Collaboration)
M.D. Albrow, S.-J. Chung, C. Han, K.-H. Hwang, Y.K.Jung, I.-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, (KMTNet Collaboration)
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, (MiNDSTEp Collaboration)
2018, Acta Astron., 68, 1 (arXiv:1802.02582)

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.

Light curve and best-fit model of OGLE-2017-BLG-1434

Light curve and best-fit model of OGLE-2017-BLG-1434

PLEASE cite the following paper when using the data or referring to these OGLE results:
    Udalski et al., 2018, Acta Astron., 68, 1 (arXiv:1802.02582)

Any comments about the data and the form of their presentation are welcome as they can improve the future releases of the OGLE analyses. Send your messages to udalski AT astrouw.edu.pl.

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