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arXiv · 2011.08855

SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star

Thayne Currie·Timothy D. Brandt·Masayuki Kuzuhara·Jeffery Chilcote·Olivier Guyon·Christian Marois·Tyler Groff·Julien Lozi·Sebastien Vievard·Ananya Sahoo·Vincent Deo·Nemanja Jovanovic·Frantz Martinache·Kevin Wagner·Trent J. Dupuy·Matthew Wahl·Michael Letawsky·Yiting Li·Yunlin Zeng·G. Mirek Brandt·Daniel Michalik·Carol Grady·Markus Janson·Gillian R. Knapp·Jungmi Kwon·Kellen D. Lawson·Michael McElwain·Taichi Uyama·John P. Wisniewski·Motohide Tamura
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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 $\sim$ 20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5$\sigma$ astrometric acceleration on the star as detected with the $Gaia$ and $Hipparcos$ satellites. SCExAO/CHARIS $JHK$ (1.1--2.4 $\mu$m) spectra and Keck/NIRC2 $L_{\rm p}$ (3.78 $\mu$m) 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 $\pm$ 8 $M_{\rm J}$ and an eccentricity of $e$ $<$0.46 at 95\% confidence. HD 33632 Ab's mass and mass ratio (4.0\% $\pm$ 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.

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Thayne Currie, Timothy D. Brandt, Masayuki Kuzuhara, Jeffery Chilcote, Olivier Guyon, Christian Marois, Tyler Groff, Julien Lozi, Sebastien Vievard, Ananya Sahoo, Vincent Deo, Nemanja Jovanovic, Frantz Martinache, Kevin Wagner, Trent J. Dupuy, Matthew Wahl, Michael Letawsky, Yiting Li, Yunlin Zeng, G. Mirek Brandt, Daniel Michalik, Carol Grady, Markus Janson, Gillian R. Knapp, Jungmi Kwon, Kellen D. Lawson, Michael McElwain, Taichi Uyama, John P. Wisniewski, Motohide Tamura. 2020-11-17. SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star. https://doi.org/10.3847/2041-8213/abc631

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