OGLE-2017-BLG-1130: The First Binary Gravitational Microlens Detected from Spitzer Only

June 2018 • 2018ApJ...860...25W

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

Abstract • We analyze the binary gravitational microlensing event OGLE-2017-BLG-1130 (mass ratio q ∼ 0.45), the first published case in which the binary anomaly was detected only by the Spitzer Space Telescope. This event provides strong evidence that some binary signals can be missed by observations from the ground alone but detected by Spitzer. We therefore invert the normal procedure, first finding the lens parameters by fitting the space-based data and then measuring the microlensing parallax using ground-based observations. We also show that the normal four-fold space-based degeneracy in the single-lens case can become a weak eight-fold degeneracy in binary-lens events. Although this degeneracy is resolved in event OGLE-2017-BLG-1130, it might persist in other events.


IPAC Authors


Sebastiano Calchi Novati

Associate Scientist

Sean Carey

Senior Scientist