A Caltech Library Service

Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b

Wilcomb, Kielan K. and Konopacky, Quinn M. and Barman, Travis S. and Theissen, Christopher A. and Ruffio, Jean-Baptiste and Brock, Laci and Macintosh, Bruce and Marois, Christian (2020) Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b. Astronomical Journal, 160 (5). Art. No. 207. ISSN 1538-3881.

PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present moderate-resolution (R ~ 4000) K-band spectra of the "super-Jupiter," κ 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 κ 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 κ Andromedae A. We also measure the radial velocity of κ 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 κ Andromedae b.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wilcomb, Kielan K.0000-0002-9803-8255
Konopacky, Quinn M.0000-0002-9936-6285
Barman, Travis S.0000-0002-7129-3002
Theissen, Christopher A.0000-0002-9807-5435
Ruffio, Jean-Baptiste0000-0003-2233-4821
Brock, Laci0000-0003-4297-7306
Macintosh, Bruce0000-0003-1212-7538
Marois, Christian0000-0002-4164-4182
Additional Information:© 2020. The American Astronomical Society. Received 2020 June 25; revised 2020 August 20; accepted 2020 September 16; published 2020 October 15. K.K.W. would like to thank the referee, Joe Carson, for reviewing this work, and Marshall Perrin and Justin Otor for helpful conversations relating to this work. K.K.W. would also like to thank Thea Kozakis and Laura Stevens for discovering κ And b. J.-B.R. acknowledges support from the David & Ellen Lee Prize Postdoctoral Fellowship. Work conducted by L.B. and T.B. was supported by the National Science Foundation under Award No. 1405504. Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51447.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Material presented in this work is supported by the National Aeronautics and Space Administration under Grants/Contracts/Agreements No.NNX17AB63G and NNX15AD95G issued through the Astrophysics Division of the Science Mission Directorate. Any opinions, findings, and conclusions or recommendations expressed in this poster are those of the author(s) and do not necessarily reflect the views of the National Aeronautics and Space Administration. 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. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Funding AgencyGrant Number
David and Ellen Lee Postdoctoral ScholarshipUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51447.001-A
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Direct imaging ; Exoplanet atmospheres ; High resolution spectroscopy ; Exoplanet formation ; Radial velocity
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Direct imaging (387); Exoplanet atmospheres (487); High resolution spectroscopy (2096); Exoplanet formation (492); Radial velocity (1332)
Record Number:CaltechAUTHORS:20201015-152734180
Persistent URL:
Official Citation:Kielan K. Wilcomb et al 2020 AJ 160 207
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106100
Deposited By: George Porter
Deposited On:16 Oct 2020 16:11
Last Modified:16 Oct 2020 16:11

Repository Staff Only: item control page