Tuesday, April 26, 2016

Two Different Interpretations of a Microlensing Signature

Figure 1: Artist's impression of a pair of red dwarf stars.

OGLE-2013-BLG-0723 is a gravitational microlensing event that was reported to be caused by a Venus-mass planet orbiting a brown dwarf in a binary system. Han et al. (2016) analysed the event again and found that a 2-body solution is more likely than the current 3-body solution. In this case, the 2-body solution involves a pair of low-mass red dwarf stars with ~0.2 and ~0.1 times the mass of the Sun, located ~3000 light years away. Both stars are spaced ~1.5 AU from each other. The fact that two very different solutions can approximate the same gravitational microlensing light curve shows that careful examination of all possible solutions is necessary.

Figure 2: Light curve of OGLE-2013-BLG-0723. The cyan and black curves plotted over the data are the best-fit models obtained from the previous 3-body model and the newly found 2-body model, respectively. The two lower panels show the residuals from the individual models. Han et al. (2016)

Han et al. (2016), "A New Non-Planetary Interpretation of the Microlensing Event OGLE-2013-BLG-0723", arXiv:1604.06533 [astro-ph.EP]