First Resolution of Microlensed Images of a Binary-lens Event
Tan, Thiam-Guan; Thompson, I. B.; Le Bouquin, Jean-Baptiste; Buder, Sven; Bland-Hawthorn, Joss; Kos, Janez; Sharma, Sanjib; Kreidberg, Laura; Udalski, Andrzej; Mróz, Przemek; Eckart, Andreas; Lai, Olivier; Kochanek, Christopher S.; Dong, Subo; Brandner, Wolfgang; Förster Schreiber, Natascha M.; Buckley, David A. H.; Kervella, Pierre; Mérand, A.; Fabricius, Maximilian; Feuchtgruber, Helmut; Lutz, Dieter; Montargès, Miguel; Shangguan, Jinyi; Rabien, Sebastian; Genzel, Reinhard; Bensby, Thomas; Davies, Richard I.; Petrucci, Pierre-Olivier; Woillez, J.; Lacour, Sylvestre; Nowak, Mathias; Berger, Jean-Philippe; Millour, Florentin; Tacconi, Linda; Sturm, Eckhard; Leftley, James; Defrère, Denis; Garcia, Paulo; Shimizu, Taro T.; Hönig, Sebastian; Laugier, Romain; Perraut, Karine; Eisenhauer, Frank; Bourdarot, Guillaume; Gillessen, Stefan; Ott, Thomas; Paumard, Thibaut; Perrin, Guy; Straubmeier, Christian; Vincent, Frédéric; Widmann, Felix; Christie, Grant; Natusch, Tim; Wu, Zexuan; Drescher, Antonia; Sauter, Jonas; Subroweit, Matthias; Dougados, Catherine; Nowacki, Hugo; Gould, Andrew P.; El Dayem, Karim Abd; Berdeu, Anthony; Heißel, Gernot; Houlle, Mathis; Lopez, Bruno; Mang, Felix; Petrov, Romain; Pourre, Nicolas; Ribeiro, Diogo C.; Robbe-Dubois, Sylvie; Sadun Bordoni, Matteo; Santos, Daryl; Scigliuto, Jules; Sykes, Calvin
China, Germany, United States, Poland, New Zealand, Australia, Sweden, Slovenia, South Africa, France, Belgium, Portugal, United Kingdom
Abstract
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 the angular Einstein radius θ 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 ⊙ and M 2 = 0.130 ± 0.007 M ⊙, a projected separation of r ⊥ = 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.