Full orbital solution for the binary system in the northern Galactic disc microlensing event Gaia16aye^⋆

¹ Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
e-mail: wyrzykow@astrouw.edu.pl
² Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea
³ Sternberg Astronomical Institute, Moscow State University, Universitetskii pr. 13, 119992 Moscow, Russia
⁴ Instituto de Astrofisica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
⁵ Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain
⁶ Institute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA Cambridge, UK
⁷ INAF – Osservatorio Astronomico di Roma, Via di Frascati 33, 00078 Monte Porzio Catone, Roma, Italy
⁸ Indian Institute of Astrophysics, II Block Koramangala, Bengaluru 560034, India
⁹ National Astronomical Research Institute of Thailand, 260, Moo 4, T. Donkaew, A. Mae Rim, Chiang Mai 50180, Thailand
¹⁰ Department of Space Sciences and Technologies, Faculty of Science, Akdeniz University, 07058, Antalya, Turkey
¹¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
¹² School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 6997801, Israel
¹³ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
¹⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
¹⁵ Institute of Astronomy and NAO Rozhen, BAS, 72 Tsarighradsko Shousse Blvd., 1784 Sofia, Bulgaria
¹⁶ National Optical Astronomy Observatory, 950 N Cherry Avenue, Tucson, AZ 85719, USA
¹⁷ Subaru Telescope, National Astronomical Observatory of Japan, 650 N Aohoku Place, Hilo, HI 96720, USA
¹⁸ IAASARS, National Observatory of Athens, Vas. Pavlou & I. Metaxa, 15236 Penteli, Greece
¹⁹ Dipartimento di Fisica E.R. Caianiello, Università di Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy
²⁰ Department of Astronomy and Space Sciences, Ege University, 35100 Izmir, Turkey
²¹ Centre for Advanced Instrumentation, University of Durham, South Road, Durham DH1 3LE, UK
²² Institut del Ciències del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), c/ Martí i Franquès, 1, 08028 Barcelona, Spain
²³ Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 Nijmegen, The Netherlands
²⁴ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
²⁵ Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia
²⁶ Science Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 Noordwijk, The Netherlands
²⁷ Qatar Environment and Energy Research Institute(QEERI), HBKU, Qatar Foundation, Doha, Qatar
²⁸ Institut d’Astrophysique de Paris, Sorbonne Université, CNRS, UMR 7095, 98 bis bd Arago, 75014 Paris, France
²⁹ Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
³⁰ Centre for Exoplanet Science, SUPA School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
³¹ Akdeniz University, Dumlupinar Blv., Campus, 07058 Antalya, Turkey
³² Istanbul University, Department of Astronomy and Space Sciences, 34119, Beyazit Istanbul, Turkey
³³ Dept. of Physics & Astronomy, UCL, Gower St., London WC1E 6BT, UK
³⁴ Center for Astrophysics and Cosmology, University of Nova Gorica, Vipavska cesta 11c, 5270 Ajdovščina, Slovenia
³⁵ European Southern Observatory, Karl Schwarzschild Str 2, 85748 Garching, Germany
³⁶ Astronomical Observatory, Jagiellonian University, Kraków, Poland
³⁷ Mt. Suhora Observatory, Pedagogical University, ul. Podchor ażych 2, 30-084 Kraków, Poland
³⁸ Astronomical Institute of the Academy of Sciences of the Czech Republic, Ondřejov, Czech Republic
³⁹ Czech Technical University, Faculty of Electrical Engineering, Technická 2. 166 27, Praha 6, Czech Republic
⁴⁰ Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
⁴¹ International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
⁴² Department of Physics, School of Science, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro, Tokyo 152-8551, Japan
⁴³ TÜBİTAK National Observatory, Akdeniz University Campus, 07058 Antalya, Turkey
⁴⁴ Instytut Astronomiczny Uniwersytetu Wrocławskiego, ul. Kopernika 11, 51-622 Wrocław, Poland
⁴⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
⁴⁶ School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
⁴⁷ Osservatorio Astronomico Provinciale di Montarrenti, S. S. 73 Ponente, 53018, Sovicille Siena, Italy
⁴⁸ INAF – Osservatorio Astrofisico di Catania, Via Santa Sofia 78, 95123 Catania, Italy
⁴⁹ Faulkes Telescope Project, School of Physics, and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA, UK
⁵⁰ Astronomy Department, University of California, Berkeley, CA 94720, USA
⁵¹ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
⁵² National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing, PR China
⁵³ Graduate Institute of Astronomy, National Central University, Jhongli 32001, Taiwan
⁵⁴ Department of particle physics and astrophysics, Weizmann Institute of Science, Revovot, Israel
⁵⁵ Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio Av. 3, 10257 Vilnius, Lithuania
⁵⁶ Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA
⁵⁷ Soka University of America, 1 University Drive, Aliso Viejo, CA 92656, USA
⁵⁸ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
⁵⁹ Universitat Politècnica de Catalunya, Departament de Física, c/Esteve Terrades 5, 08860 Castelldefels, Spain
⁶⁰ Institute of Astrophysics, Foundation for Research and Technology-Hellas, 71110 Heraklion, Crete, Greece
⁶¹ New York University Abu Dhabi, Saadiyat Island, PO Box 129188, Abu Dhabi, UAE
⁶² Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USA
⁶³ INAF Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶⁴ Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
⁶⁵ Astro Space Center of Lebedev Physical Institute, Profsoyuznaya St. 84/32, 117997 Moscow, Russia
⁶⁶ INAF – Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
⁶⁷ Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
⁶⁸ Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
⁶⁹ Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁷⁰ Institute for Space Studies of Catalonia, c/Gran Capitá 2–4, Edif. Nexus 104, 08034 Barcelona, Spain
⁷¹ Space Science Data Center – ASI, Via del Politecnico SNC, 00133 Roma, Italy
⁷² Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya str. 48, 119017 Moscow, Russia
⁷³ Observatoire de Genève, Université de Genève, 1290 Versoix, Switzerland
⁷⁴ University of Crete, Physics Department & Institute of Theoretical & Computational Physics, 71003 Heraklion, Crete, Greece
⁷⁵ Kazan Federal University, ul. Kremlevskaya 18, 420008 Kazan, Russia
⁷⁶ Center for Theoretical Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
⁷⁷ Department of Astrophysics, Astronomy & Mechanics, Faculty of Physics, University of Athens, 15783 Athens, Greece
⁷⁸ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
⁷⁹ Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Italy
⁸⁰ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436, Macul Santiago, Chile
⁸¹ Istituto Internazionale per gli Alti Studi Scientifici (IIASS), Via G. Pellegrino 19, 84019 Vietri sul Mare, SA, Italy
⁸² IPAC, Mail Code 100-22, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA
⁸³ Space Research Institute of Russian Academy of Sciences (IKI), 84/32 Profsoyuznaya, Moscow, Russia
⁸⁴ National Research University Higher School of Economics, Myasnitskaya ul. 20, 101000 Moscow, Russia
⁸⁵ Institute of Solar-Terrestrial Physics SB RAS, Irkutsk, Russia
⁸⁶ Academy of Sciences of Tatarstan, Kazan, Russia
⁸⁷ Kavli Institute for Cosmology, Madingley Road, Cambridge CB3 0HA, UK
⁸⁸ Université Côte d’Azur, OCA, CNRS, Laboratoire Lagrange, Nice, France
⁸⁹ Crimean Astrophysical Observatory, Nauchnyi, Crimea
⁹⁰ American Association of Variable Star Observers (AAVSO), 49 Bay State Road, Cambridge, MA 02138, USA
⁹¹ Swarthmore College, 500 College Avenue, Swarthmore, PA 19081, USA
⁹² Dark Sky Observatory, Department of Physics and Astronomy, Appalachian State University, Boone, NC 28608, USA
⁹³ University of North Carolina, Chapel Hill, North Carolina, NC 27599, USA
⁹⁴ Yerkes Observatory, Department of Astronomy and Astrophysics, University of Chicago, 373 W. Geneva St., Williams Bay, WI 53191, USA
⁹⁵ Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
⁹⁶ Millenium Institute of Astrophysics, Santiago, Chile
⁹⁷ Horten Upper Secondary School, Bekkegata 2, 3181 Horten, Norway
⁹⁸ Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India
⁹⁹ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking RH5 6NT, UK
¹⁰⁰ GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
¹⁰¹ School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
¹⁰² Department of Physics, Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein 9300, Republic of South Africa

Received: 22 January 2019
Accepted: 10 October 2019

Abstract

Gaia16aye was a binary microlensing event discovered in the direction towards the northern Galactic disc and was one of the first microlensing events detected and alerted to by the Gaia space mission. Its light curve exhibited five distinct brightening episodes, reaching up to I = 12 mag, and it was covered in great detail with almost 25 000 data points gathered by a network of telescopes. We present the photometric and spectroscopic follow-up covering 500 days of the event evolution. We employed a full Keplerian binary orbit microlensing model combined with the motion of Earth and Gaia around the Sun to reproduce the complex light curve. The photometric data allowed us to solve the microlensing event entirely and to derive the complete and unique set of orbital parameters of the binary lensing system. We also report on the detection of the first-ever microlensing space-parallax between the Earth and Gaia located at L2. The properties of the binary system were derived from microlensing parameters, and we found that the system is composed of two main-sequence stars with masses 0.57 ± 0.05 M_⊙ and 0.36 ± 0.03 M_⊙ at 780 pc, with an orbital period of 2.88 years and an eccentricity of 0.30. We also predict the astrometric microlensing signal for this binary lens as it will be seen by Gaia as well as the radial velocity curve for the binary system. Events such as Gaia16aye indicate the potential for the microlensing method of probing the mass function of dark objects, including black holes, in directions other than that of the Galactic bulge. This case also emphasises the importance of long-term time-domain coordinated observations that can be made with a network of heterogeneous telescopes.