Kavli Affiliate: Jinyi Shangguan
| First 5 Authors: Zexuan Wu, Subo Dong, A. Mérand, Christopher S. Kochanek, Przemek Mróz
| Summary:
We resolve the multiple images of the binary-lens microlensing event
ASASSN-22av using the GRAVITY instrument of the Very Large Telescope
Interferometer (VLTI). The light curves show weak binary perturbations,
complicating the analysis, but the joint modeling with the VLTI data breaks
several degeneracies, arriving at a strongly favored solution. Thanks to
precise measurements of angular Einstein radius theta_E = 0.726 +/- 0.002 mas
and microlens parallax, we determine that the lens system consists of two M
dwarfs with masses of M_1 = 0.261 +/- 0.009 M_sun and M_2 = 0.252 +/- 0.017
M_sun, a projected separation of r_perp = 7.42 +/- 0.33 AU and a distance of
D_L = 2.31 +/- 0.09 kpc. The successful VLTI observations of ASASSN-22av open
up a new path for studying intermediate-separation (i.e., a few AUs)
stellar-mass binaries, including those containing dark compact objects such as
neutron stars and stellar-mass black holes.
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