Abstract
Abstract We present the result of microlensing event MOA-2016-BLG-290, which received observations from the two-wheel Kepler (K2), Spitzer, as well as ground-based observatories. A joint analysis of data from K2 and the ground leads to two degenerate solutions of the lens mass and distance. This degeneracy is effectively broken once the (partial) Spitzer light curve is included. Altogether, the lens is found to be an extremely low-mass star or brown dwarf ( ) located in the Galactic bulge ( kpc). MOA-2016-BLG-290 is the first microlensing event for which we have signals from three well-separated (∼1 au) locations. It demonstrates the power of two-satellite microlensing experiment in reducing the ambiguity of lens properties, as pointed out independently by S. Refsdal and A. Gould several decades ago.
Highlights
The implementation of the space-based microlensing parallax has revolutionalized the field of Galactic microlensing (e.g., Dong et al 2007; Udalski et al 2015)
The Spitzer microlensing program has been successful in terms of measuring masses of individual planetary systems (Udalski et al 2015; Street et al 2016; Ryu et al 2017; Shvartzvald et al 2017) and constraining the Galactic distribution of planets (Calchi Novati et al 2015a; Yee et al 2015a; Zhu et al 2017b), there is a generic uncertainty in measuring pE with a single satellite, especially in cases of single-lens events
We present the analysis of the first microlensing event that has detected signals from at least three wellseparated (∼1 au) locations, which in the current case are Earth, K2, and Spitzer
Summary
The implementation of the space-based microlensing parallax has revolutionalized the field of Galactic microlensing (e.g., Dong et al 2007; Udalski et al 2015). Ground-based telescopes and a space-based telescope such as Spitzer or Kepler because of the large separation (∼1 au; Refsdal 1966; Gould 1994; Gould & Horne 2013) This effect yields the microlensing parallax vector pE, which conveys crucial information on the lens mass and distance. In 2016, the two-wheel Kepler mission (K2; Howell et al 2014) conducted a microlensing campaign toward the Galactic bulge from April 22 to July 2, which overlapped with the Spitzer microlensing campaign (June 18 to July 26) for nearly two weeks With this unique opportunity, a specific program (Gould et al 2015) was developed in order to demonstrate the idea of Refsdal (1966) and Gould (1994). About 30 microlensing events received observations from both satellites in addition to the dense coverage by groundbased telescopes. This work presents the first analysis of this sample, the bright single-lens event MOA-2016BLG-290 for which the microlensing signal is detected from all three locations.
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