OGLE-2014-BLG-1186: gravitational microlensing providing evidence for a planet orbiting the foreground star or for a close binary source?

Year: 2019

Type: article

Abstract: Discussing the particularly long gravitational microlensing event OGLE-2014-BLG-1186 with a time-scale tE ∼ 300 d, we present a methodology for identifying the nature of localised deviations from single-lens point-source light curves, which ensures that (1) the claimed signal is substantially above the noise floor, (2) the inferred properties are robustly determined and their estimation is not subject to confusion with systematic noise in the photometry, (3) alternative viable solutions within the model framework are not missed. Annual parallax and binarity could be separated and robustly measured from the wing and the peak data, respectively. We find matching model light curves that involve either a binary lens or a binary source, and discover hitherto unknown model ambiguities. Our binary-lens models indicate a planet of mass M2 = (45 ± 9) M⊕, orbiting a star of mass M1 = (0.35 ± 0.06) M⊙, located at a distance DL = (1.7 ± 0.3) kpc from Earth, whereas our binary-source models suggest a brown-dwarf lens of M = (0.046 ± 0.007) M⊙, located at a distance DL = (5.7 ± 0.9) kpc, with the source potentially being a (partially) eclipsing binary involving stars predicted to be of similar colour given the ratios between the luminosities and radii. Further observations might resolve the ambiguity in the interpretation in favour of either a lens or a source binary. We experienced that close binary source stars pose a challenge for claiming the detection of planets by microlensing in events where the source passes very close to the lens star hosting the planet.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stz306

Institutions: University of St Andrews, Las Cumbres Observatory Global Telescope Network, Hamad bin Khalifa University, Qatar Foundation, University of Salerno, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Chungbuk National University, University of Copenhagen, Heidelberg University, University of Warsaw, New York University Abu Dhabi, California Institute of Technology, Infrared Processing and Analysis Center, Max Planck Institute for Astronomy, Pontificia Universidad Católica de Chile, Astronomical Observatory of Capodimonte, International Institute for Advanced Scientific Studies "Eduardo R. Caianiello", European Southern Observatory, Tsinghua University, Chungnam National University, Korea Astronomy and Space Science Institute, Space Telescope Science Institute, University of Rome Tor Vergata, Osservatorio Astrofisico di Torino, South African Astronomical Observatory, Sharif University of Technology, The Open University, Royal Observatory, Max Planck Institute for Solar System Research, University of Edinburgh, Keele University, Liverpool John Moores University, University of Liège, Queen Mary University of London, International Space Science Institute, University of Warwick, The Ohio State University

Language: English

Topic: Stellar, planetary, and galactic studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: bronze

Funders: California Institute of Technology, Qatar Foundation, Villum Fonden, University of St Andrews, National Research Foundation, Universität Heidelberg, Fonds National de la Recherche Luxembourg, Ministero dell’Istruzione, dell’Università e della Ricerca, National Research Foundation of Korea, Regione Campania, Narodowym Centrum Nauki, Università degli Studi di Roma Tor Vergata, Qatar National Research Fund, Science and Technology Facilities Council

OpenAlex ID: W2886566978