Radial Velocity Measurements of HR 8799 b and c with Medium Resolution Spectroscopy
Abstract
High-contrast medium resolution spectroscopy has been used to detect molecules such as water and carbon monoxide in the atmospheres of gas giant exoplanets. In this work, we show how it can be used to derive radial velocity (RV) measurements of directly imaged exoplanets. Improving upon the traditional cross-correlation technique, we develop a new likelihood based on joint forward modeling of the planetary signal and the starlight background (i.e., speckles). After marginalizing over the starlight model, we infer the barycentric RV of HR 8799 b and c in 2010 yielding −9.2 ± 0.5 km s⁻¹ and −11.6 ± 0.5 km s⁻¹, respectively. These RV measurements help to constrain the 3D orientation of the orbit of the planet by resolving the degeneracy in the longitude of an ascending node. Assuming coplanar orbits for HR 8799 b and c, but not including d and e, we estimate Ω = 89°⁺²⁷₋₁₇ and i = 20°.8^(4.5)_(-3.7).
Additional Information
© 2019 The American Astronomical Society. Received 2019 August 23; revised 2019 September 14; accepted 2019 September 16; published 2019 October 24. We would like to thank Tuan Do and Adam Mantz for their help with OSIRIS data calibration, and statistics related issues respectively. The research was supported by grants from NSF, including AST-1411868 (J.-B.R., B.M.), 1614492, and 1614492 (T.S.B.). Support was provided by grants from the National Aeronautics and Space Administration (NASA) NNX15AD95G (J.-B.R., R.J.D.R.). This work benefited from NASA's Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA's Science Mission Directorate. Q.M.K., T.S.B., and K.K.W. were supported by NASA under grant no. NNX17AB63G issued through the Astrophysics Division of the Science Mission Directorate. Any opinions, findings, and conclusions or recommendations expressed in this work are those of the author(s) and do not necessarily reflect the views of the National Aeronautics and Space Administration. This work made use of the sky-background models made available by the Gemini observatory.12 The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We also wish to recognize the very important 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. Facility: Keck I (OSIRIS). - Software: astropy13 (Astropy Collaboration et al. 2013), Matplotlib14 (Hunter 2007), orbitize!15 (Blunt et al. 2019), ptemcee16 (Vousden et al. 2016; Foreman-Mackey et al. 2013).Attached Files
Published - Ruffio_2019_AJ_158_200.pdf
Accepted Version - 1909.07571.pdf
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Additional details
- Eprint ID
- 99480
- Resolver ID
- CaltechAUTHORS:20191028-083634607
- AST-1411868
- NSF
- AST-1614492
- NSF
- AST-1614492
- NSF
- NNX15AD95G
- NASA
- NNX17AB63G
- NASA
- W. M. Keck Foundation
- Created
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2019-10-28Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field