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

Creators: Currie, Thayne; Brandt, Timothy D.; Kuzuhara, Masayuki; Chilcote, Jeffrey; Guyon, Olivier; Marois, Christian; Groff, Tyler D.; Lozi, Julien; Vievard, Sebastien; Sahoo, Ananya; Deo, Vincent; Jovanovic, Nemanja; Martinache, Frantz; Wagner, Kevin; Dupuy, Trent; Wahl, Matthew; Letawsky, Michael; Li, Yiting; Zeng, Yunlin; Brandt, G. Mirek; Michalik, Daniel; Grady, Carol; Janson, Markus; Knapp, Gillian R.; Kwon, Jungmi; Lawson, Kellen; McElwain, Michael W.; Uyama, Taichi; Wisniewski, John; Tamura, Motohide

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 L_p (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 M_J 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.

Additional Information

© 2020. The American Astronomical Society. Received 2020 September 19; revised 2020 October 21; accepted 2020 October 30; published 2020 November 30. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We thank Eric Mamajek and William Cochran for helpful comments regarding the HD 33632 system properties. The authors acknowledge the very significant cultural role and reverence that the summit of Maunakea holds within the Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. We acknowledge the critical importance of the current and recent Subaru and Keck Observatory daycrew, technicians, support astronomers, telescope operators, computer support, and office staff employees, especially during the challenging times presented by the COVID-19 pandemic. Their expertise, ingenuity, and dedication is indispensable to the continued successful operation of these observatories. We thank the Subaru and NASA Keck Time Allocation Committees for their generous support of this program. T.C. was supported by a NASA Senior Postdoctoral Fellowship and NASA/Keck grant LK-2663-948181. T.B. gratefully acknowledges support from the Heising-Simons foundation and from NASA under grant #80NSSC18K0439. M.T. is supported by JSPS KAKENHI grant #18H05442. The development of SCExAO was supported by JSPS (Grant-in-Aid for Research #23340051, #26220704, and #23103002), Astrobiology Center of NINS, Japan, the Mt Cuba Foundation, and the director's contingency fund at Subaru Telescope. CHARIS was developed under the support by the Grant-in-Aid for Scientific Research on Innovative Areas #2302. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

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Published - Currie_2020_ApJL_904_L25.pdf

Accepted Version - 2011.08855.pdf

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