http://arxiv.org/abs/1909.06375
As a significant fraction of stars are in multiple systems, binaries play a crucial role in stellar evolution. Among short-period ($<$1 day) binary characteristics, age remains one of the most difficult to measure. In this paper, we constrain the lifetime of short-period binaries through their kinematics. With the kinematic information from Gaia Data Release 2 and light curves from {\it Wide-field Infrared Survey Explorer} (WISE), we investigate the eclipsing binary fraction as a function of kinematics for a volume-limited main-sequence sample. We find that the eclipsing binary fraction peaks at a tangential velocity of $10^{1.3-1.6}$ km s$^{-1}$, and decreases towards both low and high velocity end. This implies that thick disk and halo stars have eclipsing binary fraction $\gtrsim 10$ times smaller than the thin-disk stars. Using Galactic models, we show that our results are inconsistent with any known dependence of binary fraction on metallicity. Instead, our best-fit models suggest that the formation of these short-period binaries is delayed by $0.6$-3 Gyr, and the disappearing time is less than the age of the thick disk. The delayed formation time of $\gtrsim0.6$ Gyr is too long for any pre-main sequence interaction alone and is more consistent with the three-body interaction through the Kozai-Lidov mechanism and magnetic winds. Because the main-sequence lifetime of our sample is longer than 14 Gyr, if the disappearance of short-period binaries in the old population is due to their finite lifetime, our results imply that most ($\gtrsim90$ %) short-period binaries in our sample are destroyed during their main-sequence stage.
H. Hwang and N. Zakamska
Tue, 17 Sep 19
42/98
Comments: Submitted to MNRAS. Figure 5 is the key result