Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b
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Author
Wilcomb, Kielan K.Konopacky, Quinn M.
Barman, Travis S.

Theissen, Christopher A.
Ruffio, Jean-Baptiste

Brock, Laci
Macintosh, Bruce

Marois, Christian

Affiliation
Univ Arizona, Lunar & Planetary LabIssue Date
2020-10-15
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IOP PUBLISHING LTDCitation
Wilcomb, K. K., Konopacky, Q. M., Barman, T. S., Theissen, C. A., Ruffio, J. B., Brock, L., ... & Marois, C. (2020). Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b. The Astronomical Journal, 160(5), 207.Journal
ASTRONOMICAL JOURNALRights
© 2020. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
We present moderate-resolution (R similar to 4000) K-band spectra of the "super-Jupiter,"kappa Andromedae b. The data were taken with the OSIRIS integral field spectrograph at Keck Observatory. The spectra reveal resolved molecular lines from H2O and CO, and are compared to a custom PHOENIX atmosphere model grid appropriate for young planetary-mass objects. We fit the data using a Markov chain Monte Carlo forward-modeling method. Using a combination of our moderate-resolution spectrum and low-resolution, broadband data from the literature, we derive an effective temperature of T-eff = 1950-2150 K, a surface gravity of log g = 3.5-4.5, and a metallicity of [M/H] = -0.2-0.0. These values are consistent with previous estimates from atmospheric modeling and the currently favored young age of the system (<50 Myr). We derive a C/O ratio of 0.70(-0.24)(+0.09) for the source, broadly consistent with the solar C/O ratio. This, coupled with the slightly subsolar metallicity, implies a composition consistent with that of the host star, and is suggestive of formation by a rapid process. The subsolar metallicity of kappa Andromedae b is also consistent with predictions of formation via gravitational instability. Further constraints on formation of the companion will require measurement of the C/O ratio of kappa Andromedae A. We also measure the radial velocity of kappa Andromedae b for the first time, with a value of -1.4 +/- 0.9 km s(-1) relative to the host star. We find that the derived radial velocity is consistent with the estimated high eccentricity of kappa Andromedae b.ISSN
0004-6256EISSN
1538-3881Version
Final published versionSponsors
National Aeronautics and Space Administrationae974a485f413a2113503eed53cd6c53
10.3847/1538-3881/abb9b1