Spitzer Opens New Path to Break Classic Degeneracy for Jupiter-mass Microlensing Planet OGLE-2017-BLG-1140Lb

June 2018 • 2018AJ....155..261C

Authors • Calchi Novati, S. • Skowron, J. • Jung, Y. K. • Beichman, C. • Bryden, G. • Carey, S. • Gaudi, B. S. • Henderson, C. B. • Shvartzvald, Y. • Yee, J. C. • Zhu, W. • Spitzer Team • Udalski, A. • Szymański, M. K. • Mróz, P. • Poleski, R. • Soszyński, I. • Kozłowski, S. • Pietrukowicz, P. • Ulaczyk, K. • Pawlak, M. • Rybicki, K. • Iwanek, P. • OGLE Collaboration • Albrow, M. D. • Chung, S. -J. • Gould, A. • Han, C. • Hwang, K. -H. • Ryu, Y. -H. • Shin, I. -G. • Zang, 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, R. W. • KMTNet Collaboration

Abstract • We analyze the combined Spitzer and ground-based data for OGLE-2017-BLG-1140 and show that the event was generated by a Jupiter-class ({m}p≃ 1.6 {M}{{J}{{u}}{{p}}}) planet orbiting a mid-late M dwarf (M≃ 0.2 {M}) that lies {D}LS}≃ 1.0 {kpc} in the foreground of the microlensed Galactic-bar source star. The planet-host projected separation is {a}\perp ≃ 1.0 {au}, i.e., well beyond the snow line. By measuring the source proper motion {{\boldsymbol{μ }}}s from ongoing long-term OGLE imaging and combining this with the lens-source relative proper motion {{\boldsymbol{μ }}}rel} derived from the microlensing solution, we show that the lens proper motion {{\boldsymbol{μ }}}l={{\boldsymbol{μ }}}rel}+{{\boldsymbol{μ }}}s is consistent with the lens lying in the Galactic disk, although a bulge lens is not ruled out. We show that while the Spitzer and ground-based data are comparably well fitted by planetary (i.e., binary-lens (2L1S)) and binary-source (1L2S) models, the combination of Spitzer and ground-based data decisively favors the planetary model. This is a new channel to resolve the 2L1S/1L2S degeneracy, which can be difficult to break in some cases.


IPAC Authors


Sebastiano Calchi Novati

Associate Scientist

Sean Carey

Senior Scientist