SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
Currie, Thayne; Kwon, Jungmi; Tamura, Motohide; Wagner, Kevin; Uyama, Taichi; Lawson, Kellen; Wisniewski, John; Martinache, Frantz; Kuzuhara, Masayuki; Brandt, Timothy D.; Li, Yiting; Brandt, G. Mirek; Zeng, Yunlin; Michalik, Daniel; Marois, Christian; Chilcote, Jeffrey; Guyon, Olivier; Janson, Markus; Jovanovic, Nemanja; Knapp, Gillian R.; Lozi, Julien; McElwain, Michael W.; Dupuy, Trent; Groff, Tyler D.; Vievard, Sebastien; Sahoo, Ananya; Deo, Vincent; Grady, Carol; Wahl, Matthew; Letawsky, Michael
United States, Japan, Canada, France, United Kingdom, Netherlands, Sweden
Abstract
We present the direct imaging discovery of a substellar companion to the nearby Sun-like star, HD 33632 Aa, at a projected separation of ∼20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5σ astrometric acceleration on the star as detected with the Gaia and Hipparcos satellites. SCExAO/CHARIS JHK (1.1-2.4 μm) spectra and Keck/NIRC2 Lp (3.78 μm) photometry are best matched by a field L/T transition object: an older, higher-gravity, and less dusty counterpart to HR 8799 cde. Combining our astrometry with Gaia/Hipparcos data and archival Lick Observatory radial velocities, we measure a dynamical mass of 46.4 ± 8 MJ and an eccentricity of e < 0.46 at 95% confidence. HD 33632 Ab's mass and mass ratio (4.0% ± 0.7%) are comparable to the low-mass brown dwarf GJ 758 B and intermediate between the more massive brown dwarf HD 19467 B and the (near-)planet-mass companions to HR 2562 and GJ 504. Using Gaia to select for direct imaging observations with the newest extreme adaptive optics systems can reveal substellar or even planet-mass companions on solar system-like scales at an increased frequency compared to blind surveys. * Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.