The Companions to B and A Stars Snapshot (C-BASS) Survey. I. Discovery of a Young Brown Dwarf Companion to HIP 17453

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Abstract We report the detection of a new brown dwarf companion to HIP 17453 A, a chemically peculiar A0V star located at a distance of 81 pc. HIP 17453 A was observed with high-resolution adaptive-optics imaging using the Near-Infrared Camera 2 on the Keck II telescope as part of the Companions to B and A Stars Snapshot (C-BASS) survey over a 10 yr baseline, revealing the presence of a companion at ~3 arcsec with proper motion consistent with the primary. We estimate the age of the HIP 17453 system as 280 ± 125 Myr, and with follow-up intermediate-resolution ( R ∼ 1800) spectroscopic observations with the Gemini Near-Infrared Spectrograph (GNIRS) on the Gemini North telescope, we found the spectrum of HIP 17453 B to be consistent with a spectral type of L2 ±1. Through interpolation of Sonora Diamondback evolutionary models, we calculate an effective temperature of 195 3 − 78 + 84 K and mass of 5 3 − 8 + 10 M Jup for HIP 17453 B, which corresponds to a mass ratio of q = 0.024 ± 0.004 for the HIP 17453 system. With its intermediate mass and young age, HIP 17453 B joins a small set of benchmark brown dwarf companions around early-type stars that are suitable for follow-up atmospheric and evolutionary studies.

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