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First Resolution of Microlensed Images of a Binary-Lens Event

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arxiv 2409.13015 v3 pith:7HRGGG76 submitted 2024-09-19 astro-ph.SR astro-ph.GAastro-ph.IM

First Resolution of Microlensed Images of a Binary-Lens Event

classification astro-ph.SR astro-ph.GAastro-ph.IM
keywords binary-lensvltiasassn-22aveventimagesstellar-massanalysisangular
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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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-lens 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 = 0.724 +/- 0.002 mas and microlens parallax, we determine that the lens system consists of two M dwarfs with masses of M_1 = 0.258 +/- 0.008 M_sun and M_2 = 0.130 +/- 0.007 M_sun, a projected separation of r_\perp = 6.83 +/- 0.31 au and a distance of D_L = 2.29 +/- 0.08 kpc. The successful VLTI observations of ASASSN-22av open up a new path for studying intermediate-separation (i.e., a few astronomical units) stellar-mass binaries, including those containing dark compact objects such as neutron stars and stellar-mass black holes.

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