Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b
AuthorWilcomb, Kielan K.
Konopacky, Quinn M.
Barman, Travis S.
Theissen, Christopher A.
AffiliationUniv Arizona, Lunar & Planetary Lab
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationWilcomb, 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.
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AbstractWe 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.
VersionFinal published version
SponsorsNational Aeronautics and Space Administration