The brown dwarf (BD) companion is an appropriate target for testing the various evolution models of BDs in that its dynamical mass can be accurately determined from its orbital motion. While most T dwarf binary has masses consistent with expectations from models, there are a few exceptions. Recently, Gliese 229B (Gl 229B) is reported that it has a higher mass than expected from the evolution models of BDs (Brandt et al. 2020), which might suggest that there is an unseen companion. In this proposal, we aim to search for a companion around a BD with IRD+AO188 by using the radial velocity (RV) method. In the preliminary result from our past observations, the accuracy of RV measurements is sufficient to detect planetary-mass companions around BDs. Whether Gl 229B turns out to be a binary or not, this observation with the highest RV accuracy ever will reveal a new aspect of BD formation and evolution. Our preliminary result also shows the large RV jump between two epochs separated by one year, which might be due to the existence of a companion. We need to both spatially resolve a BD from its nearby host star and obtain high-resolution spectra in the near-infrared, which can only be achieved with the combination of IRD and AO188.
This document was translated from LATEX by HEVEA.