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Published December 2018 | Published + Accepted Version
Journal Article Open

SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of κ And b: A Likely Young, Low-gravity Superjovian Companion


We present SCExAO/CHARIS high-contrast imaging/JHK integral field spectroscopy of κ And b, a directly imaged low-mass companion orbiting a nearby B9V star. We detect κ And b at a high signal-to-noise ratio and extract high-precision spectrophotometry using a new forward-modeling algorithm for (A-)LOCI complementary to KLIP-FM developed by Pueyo et al. κ And b's spectrum best resembles that of a low-gravity L0–L1 dwarf (L0–L1γ). Its spectrum and luminosity are very well matched by 2MASS J0141-4633 and several other 12.5–15 M_J free-floating members of the 40 Myr old Tuc–Hor Association, consistent with a system age derived from recent interferometric results for the primary, a companion mass at/near the deuterium-burning limit (13_(-2)^(+12) M_J), and a companion-to-primary mass ratio characteristic of other directly imaged planets (q ~ 0.005_(-0.001)^(+0.005)). We did not unambiguously identify additional, more closely orbiting companions brighter and more massive than κ And b down to ρ ~ 0farcs3 (15 au). SCExAO/CHARIS and complementary Keck/NIRC2 astrometric points reveal clockwise orbital motion. Modeling points toward a likely eccentric orbit: a subset of acceptable orbits include those that are aligned with the star's rotation axis. However, κ And b's semimajor axis is plausibly larger than 55 au and in a region where disk instability could form massive companions. Deeper high-contrast imaging of κ And and low-resolution spectroscopy from extreme adaptive optics systems such as SCExAO/CHARIS and higher-resolution spectroscopy from Keck/OSIRIS or, later, IRIS on the Thirty Meter Telescope could help to clarify κ And b's chemistry and whether its spectrum provides an insight into its formation environment.

Additional Information

© 2018. The American Astronomical Society. Received 2018 September 18; revised 2018 October 15; accepted 2018 October 17; published 2018 November 30. The anonymous referee provided helpful comments, which improved the quality of this paper. Eric Mamajek, Jonathan Gagne, Sasha Hinkley, Nienke van der Marel, Maxwell Service, and Jessica Lu also provided helpful suggestions and comments on earlier manuscript drafts. We thank Adam Burrows for providing atmosphere models and Sasha Hinkley for sharing the P1640 spectrum for κ And b. We thank Randy Campbell, Carlos Alvarez, Jasmin Silva, Mitchell Rudisel, and Kevianna Adams for assistance with our Keck observations. We wish to emphasize the pivotal cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the privilege to conduct scientific observations from this mountain and thus acknowledge the responsibility to use telescope time on Maunakea wisely. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. T.C. is supported by a NASA Senior Postdoctoral Fellowship. S.B. is supported by an NSF Graduate Research Fellowship. J.C. received support from the U.S. Fulbright program and from SC Space Grant.

Attached Files

Published - Currie_2018_AJ_156_291.pdf

Accepted Version - 1810.09457


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