OGLE2017BLG0329L: A Microlensing Binary Characterized with Dramatically Enhanced Precision Using Data from Spacebased Observations
Abstract
Mass measurements of gravitational microlenses require one to determine the microlens parallax π _{E}, but precise π _{E} measurement, in many cases, is hampered due to the subtlety of the microlensparallax signal combined with the difficulty of distinguishing the signal from those induced by other higherorder effects. In this work, we present the analysis of the binarylens event OGLE2017BLG0329, for which π _{E} is measured with a dramatically improved precision using additional data from spacebased Spitzer observations. We find that while the parallax model based on the groundbased data cannot be distinguished from a zeroπ _{E} model at the 2σ level, the addition of the Spitzer data enables us to identify two classes of solutions, each composed of a pair of solutions according to the wellknown ecliptic degeneracy. It is found that the spacebased data reduce the measurement uncertainties of the north and east components of the microlensparallax vector {{\boldsymbol{π }}}_{{{E}}} by factors ∼18 and ∼4, respectively. With the measured microlens parallax combined with the angular Einstein radius measured from the resolved caustic crossings, we find that the lens is composed of a binary with component masses of either (M _{1}, M _{2}) ∼ (1.1, 0.8) M _{⊙} or ∼(0.4, 0.3) M _{⊙} according to the two solution classes. The first solution is significantly favored but the second cannot be securely ruled out based on the microlensing data alone. However, the degeneracy can be resolved from adaptive optics observations taken ∼10 years after the event.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 2018
 DOI:
 10.3847/15384357/aabd87
 arXiv:
 arXiv:1802.10196
 Bibcode:
 2018ApJ...859...82H
 Keywords:

 binaries: general;
 gravitational lensing: micro;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 9 pages, 4 tables, 6 figures