First Resolution of Microlensed Images of a Binary-lens Event

• Published in: The Astrophysical journal 2024-12, Vol.977 (2), p.229
• Main Authors: Wu, Zexuan, Dong, Subo, Mérand, A, Kochanek, Christopher S, Mróz, Przemek, Shangguan, Jinyi, Grant, Christie, Thiam-Guan Tan, Bensby, Thomas, Bland-Hawthorn, Joss, Buder, Sven, Eisenhauer, Frank, Gould, Andrew P, Kos, Janez, Natusch, Tim, Sharma, Sanjib, Udalski, Andrzej, Woillez, J, Buckley, David A H, Thompson, I B, Karim Abd El Dayem, Berdeu, Anthony, Berger, Jean-Philippe, Bourdarot, Guillaume, Brandner, Wolfgang, Davies, Richard I, Defrère, Denis, Dougados, Catherine, Drescher, Antonia, Eckart, Andreas, Fabricius, Maximilian, Feuchtgruber, Helmut, ster Schreiber, Natascha M, Garcia, Paulo, Genzel, Reinhard, Gillessen, Stefan, Heißel, Gernot, Hönig, Sebastian, Mathis Houlle, Kervella, Pierre, Kreidberg, Laura, Lacour, Sylvestre, Lai, Olivier, Laugier, Romain, Jean-Baptiste Le Bouquin, Leftley, James, Lopez, Bruno, Lutz, Dieter, Mang, Felix, Millour, Florentin, Montargès, Miguel, Nowacki, Hugo, Nowak, Mathias, Ott, Thomas, Paumard, Thibaut, Perraut, Karine, Perrin, Guy, Petrov, Romain, Petrucci, Pierre-Olivier, Pourre, Nicolas, Rabien, Sebastian, Ribeiro, Diogo C, Robbe-Dubois, Sylvie, Matteo Sadun Bordoni, Santos, Daryl, Sauter, Jonas, Scigliuto, Jules, Shimizu, Taro T, Straubmeier, Christian, Sturm, Eckhard, Subroweit, Matthias, Sykes, Calvin, Tacconi, Linda, Vincent, Frédéric, Widmann, Felix
• Format: Article
• Language: English
• Subjects: Binary stars; Black holes; Celestial bodies; Light curve; Microlenses; Neutron stars; Parallax; Separation; Very Large Telescope
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ad90b9

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 θE = 0.724 ± 0.002 mas and microlens parallax, we determine that the lens system consists of two M dwarfs with masses of M1 = 0.258 ± 0.008 M⊙ and M2 = 0.130 ± 0.007 M⊙, a projected separation of r⊥ = 6.83 ± 0.31 au, and a distance of DL = 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.