Microlensing Discovery of a Population of Very Tight, Very Low Mass Binary Brown Dwarfs

Abstract

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Astrometric orbit of a low-mass companion to an ultracool dwarf

“…Gravitational microlensing events were used to discover two binaries seen close to DE0823−49 in Fig. 5 (Choi et al 2013). Those systems are located at large distances from Earth (400 and 2000 parsec) and have low total masses (0.025 and 0.034 M ) compared to DE0823−49 with M 1 + M 2 0.10 M .…”

“…Because its last update was in July 2009, we searched the literature for new systems and revised parameters. We added 24 systems from Choi et al (2013), Burgasser et al (2011), Allers et al (2010, Gelino & Burgasser (2010), Liu et al (2010Liu et al ( , 2011, Kraus & Hillenbrand (2012), Gelino et al (2011), Chauvin et al (2012, Geyer et al (1988), Phan-Bao et al (2006), Allers et al (2009), andBurgasser et al (2009), and we updated system parameters, when applicable, using the compilations of Liu et al (2010), , and Kraus & Hillenbrand (2012).…”

“…Observations of binary systems offer the opportunity for detailed studies and a handful of small-separation ( 1 AU) ultracool binaries (i.e. both components are ultracool dwarfs) have been characterised (Lane et al 2001;Bouy et al 2004;Zapatero Osorio et al 2004;Close et al 2005;Dupuy et al 2010) using spectroscopy (Basri & Martín 1999), eclipse photometry (Stassun et al 2006), astrometry (Dahn et al 2008), and gravitational microlensing (Choi et al 2013). Many systems have been discovered using direct imaging, so they tend to be widely separated ( 1 AU) and to have components of similar brightness and nearly equal masses, which means high secondary/primary mass ratios q = M 2 /M 1 (e.g.…”

Theoretical estimations of future polarization observations for exoplanery searches with gravitational microlensing

“…A list of exoplanets detected with microlensing searches toward the Galactic bulge is given in Table 1 (see, [3,26,27,28,29,30,31,32,33,34,35,36,37]). For some planetary systems two probable regions for the planet-to-star distance are given due to the planet and star-lens parameter degeneracy [28,38], see rows 9, 14, 17 in Table 1.…”

“…For some planetary systems two probable regions for the planet-to-star distance are given due to the planet and star-lens parameter degeneracy [28,38], see rows 9, 14, 17 in Table 1. Reports about these discoveries were published in [11,27,29,30,31,32,33,34,35,36,37,39,40,41,42,44,45,46,47,48,49,50]. In these searches we have a continuous transition from massive exoplanets to brown dwarfs, since an analysis of the anomalous microlensing event, MOA-2010-BLG-073 has been done [51], where the primary of the lens is an M-dwarf with M L1 = 0.16 ± 0.03M ⊙ while the companion has M L2 = [54] 11.0 ± 2.0M J 2 , at a perpendicular distance around 1.21 ± 0.16 AU from the host star, so the low mass component of the system is near a boundary between planets and brown dwarfs.…”