CaltechAUTHORS
Published January 2023 | Version public
Journal Article Metadata-only

Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-resolution Data

Creators

  • 1. ROR icon The Ohio State University
  • 2. ROR icon Northwestern University
  • 3. ROR icon California Institute of Technology
  • 4. ROR icon Jet Propulsion Lab
  • 5. ROR icon UK Astronomy Technology Centre
  • 6. ROR icon University of California, Los Angeles
  • 7. ROR icon W.M. Keck Observatory
  • 8. ROR icon University of California, Santa Cruz
  • 9. ROR icon University of California, San Diego
  • 10. ROR icon Pomona College
  • 11. ROR icon University of California, Berkeley
  • 12. ROR icon Space Telescope Science Institute
  • 13. ROR icon Johns Hopkins University

Abstract

The formation and evolution pathway for the directly imaged multiplanetary system HR 8799 remains mysterious. Accurate constraints on the chemical composition of the planetary atmosphere(s) are key to solving the mystery. We perform a detailed atmospheric retrieval on HR 8799 c to infer the chemical abundances and abundance ratios using a combination of photometric data along with low- and high-resolution spectroscopic data (R ∼ 20–35,000). We specifically retrieve [C/H], [O/H], and C/O and find them to be 0.55_(-0.39)^(+0.36), 0.47_(-0.32)^(+0.31), and 0.67_(-0.15)^(+0.12) at 68% confidence. The superstellar C and O abundances, yet a stellar C/O ratio, reveal a potential formation pathway for HR 8799 c. Planet c, and likely the other gas giant planets in the system, formed early on (likely within ∼1 Myr), followed by further atmospheric enrichment in C and O through the accretion of solids beyond the CO ice line. The enrichment either preceded or took place during the early phase of the inward migration to the current planet locations.

Additional Information

This work is supported by the National Science Foundation under grant No. 2143400. We thank Andrew Youdin, Joan Najita, and Kaitlin Kratter for insightful discussions on gravitational instability versus pebble accretion. We thank the anonymous referee for constructive comments and suggestions that significantly improved the Paper. Funding for KPIC has been provided by the California Institute of Technology, the Jet Propulsion Laboratory, the Heising-Simons Foundation (grant Nos. 2015-129, 2017-318, and 2019-1312), the Simons Foundation (through the Caltech Center for Comparative Planetary Evolution), and NSF under grant AST-1611623. 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. We thank the Heising-Simons Foundation for supporting the workshop on combining high-resolution spectroscopy and high-contrast imaging for exoplanet characterization, where the idea originated on combining photometric data and spectral data of different resolutions.

Additional details

Identifiers

Eprint ID
118578
Resolver ID
CaltechAUTHORS:20221221-398072700.2

Funding

NSF
AST-2143400
Caltech
JPL
Heising-Simons Foundation
2015-129
Heising-Simons Foundation
2017-318
Heising-Simons Foundation
2019-1312
Simons Foundation
NSF
AST-1611623
W. M. Keck Foundation

Dates

Created
2023-01-25
Created from EPrint's datestamp field
Updated
2023-01-25
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Astronomy Department , Division of Geological and Planetary Sciences (GPS) , Caltech Center for Comparative Planetary Evolution