S22A0014

We propose REACH high-dispersion spectroscopy of HIP 53005B, which is a newly detected companion from our CHARIS observations. We characterize this companion from the point of view of SED and dynamical mass. The combination of CHARIS low-resolution spectroscopy and Keck/NIRC2 L′-band flux favors a young brown dwarf (Age: 0.7–1 Gyr, logg∼5.2, T_eff∼1800 K, and R_HIP 53005B∼2 R_Jup) while the dynamical mass derived from Gaia-Hipparcos acceleration suggests ∼150−200 M_Jup. The discrepancy might suggest an unresolved binary brown dwarfs as recent high-contrast imaging studies have started a similar trend of unresolved substellar-mass binaries. Thanks to accumulation of precise astrometry from Gaia-Hippracos catalogues and current updates of high-contrast imaging techniques, we expect to find more number of the discrepancy and potential binary companions (our result is one of the earliest suggestions). This new trend will eventually lead to detections of more exoplanets/exomoons and we are now taking the first step by characterizing HIP 53005B in detail.

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