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

Thayne Currie, Timothy D. Brandt, Taichi Uyama, Eric L. Nielsen, Sarah Blunt, Olivier Guyon, Motohide Tamura, Christian Marois, Kyle Mede, Masayuki Kuzuhara, Tyler D. Groff, Nemanja Jovanovic, N. Jeremy Kasdin, Julien Lozi, Klaus Hodapp, Jeffrey Chilcote, Joseph Carson, Frantz Martinache, Sean Goebel, Carol GradyMichael McElwain, Eiji Akiyama, Ruben Asensio-Torres, Masa Hayashi, Markus Janson, Gillian R. Knapp, Jungmi Kwon, Jun Nishikawa, Daehyeon Oh, Joshua Schlieder, Eugene Serabyn, Michael Sitko, Nour Skaf

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Abstract

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 ∼ 0 3 (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.

Original languageEnglish (US)
Article number291
JournalAstronomical Journal
Volume156
Issue number6
DOIs
StatePublished - Dec 2018

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Planetary systems
  • Stars: early-type
  • Stars: individual: (HD 222439)
  • Techniques: high angular resolution

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    Currie, T., Brandt, T. D., Uyama, T., Nielsen, E. L., Blunt, S., Guyon, O., Tamura, M., Marois, C., Mede, K., Kuzuhara, M., Groff, T. D., Jovanovic, N., Jeremy Kasdin, N., Lozi, J., Hodapp, K., Chilcote, J., Carson, J., Martinache, F., Goebel, S., ... Skaf, N. (2018). SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of κ And b: A Likely Young, Low-gravity Superjovian Companion. Astronomical Journal, 156(6), [291]. https://doi.org/10.3847/1538-3881/aae9ea