CaltechAUTHORS
Published January 2021 | Version Published + Accepted Version
Journal Article Open

Transmission Spectroscopy for the Warm Sub-Neptune HD 3167c: Evidence for Molecular Absorption and a Possible High-metallicity Atmosphere

Creators

  • 1. ROR icon Massachusetts Institute of Technology
  • 2. ROR icon University of Kansas
  • 3. ROR icon University of Montreal
  • 4. ROR icon Max Planck Institute for Astronomy
  • 5. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 6. ROR icon Space Science Institute
  • 7. ROR icon The University of Texas at Austin
  • 8. ROR icon Infrared Processing and Analysis Center
  • 9. ROR icon San Francisco State University
  • 10. ROR icon University of New Mexico
  • 11. ROR icon University of California, Berkeley
  • 12. ROR icon University of California, Santa Cruz
  • 13. ROR icon Jet Propulsion Lab
  • 14. ROR icon Ames Research Center
  • 15. ROR icon Kavli Institute for Particle Astrophysics and Cosmology
  • 16. ROR icon California Institute of Technology
  • 17. ROR icon University of Southern Queensland
  • 18. ROR icon University of Tokyo
  • 19. ROR icon Johns Hopkins University
  • 20. ROR icon University of California, Los Angeles
  • 21. ROR icon Goddard Space Flight Center

Abstract

We present a transmission spectrum for the warm (500−600 K) sub-Neptune HD 3167c obtained using the Hubble Space Telescope Wide Field Camera 3 infrared spectrograph. We combine these data, which span the 1.125–1.643 μm wavelength range, with broadband transit measurements made using Kepler/K2 (0.6–0.9 μm) and Spitzer/IRAC (4–5 μm). We find evidence for absorption by at least one of H₂O, HCN, CO₂, and CH₄ (Bayes factor 7.4; 2.5σ significance), although the data precision does not allow us to unambiguously discriminate between these molecules. The transmission spectrum rules out cloud-free hydrogen-dominated atmospheres with metallicities ≤100× solar at >5.8σ confidence. In contrast, good agreement with the data is obtained for cloud-free models assuming metallicities >700× solar. However, for retrieval analyses that include the effect of clouds, a much broader range of metallicities (including subsolar) is consistent with the data, due to the degeneracy with cloud-top pressure. Self-consistent chemistry models that account for photochemistry and vertical mixing are presented for the atmosphere of HD 3167c. The predictions of these models are broadly consistent with our abundance constraints, although this is primarily due to the large uncertainties on the latter. Interior structure models suggest that the core mass fraction is >40%, independent of a rock or water core composition, and independent of atmospheric envelope metallicity up to 1000× solar. We also report abundance measurements for 15 elements in the host star, showing that it has a very nearly solar composition.

Additional Information

© 2020. The American Astronomical Society. Received 2020 July 31; revised 2020 October 19; accepted 2020 November 5; published 2020 December 7. The authors are grateful to the referee for constructive feedback that improved the quality of the manuscript. Support for HST program GO-15333 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is based in part on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. P.M. acknowledges support from the European Research Council under the European Union's Horizon 2020 research and innovation program under grant agreement No. 832428. D.D. acknowledges support from the TESS Guest Investigator Program grant 80NSSC19K1727 and NASA Exoplanet Research Program grant 18-2XRP18 2-0136. M.R.K. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1339067. Facilities: HST(WFC3) - Hubble Space Telescope satellite, Spitzer(IRAC) - , Kepler(K2) - , Keck(HIRES). - Software: NumPy (van der Walt et al. 2011), SciPy (Virtanen et al. 2020), Matplotlib (Hunter 2007), emcee (Foreman-Mackey et al. 2013), batman (Kreidberg 2015), Astropy (Astropy Collaboration et al. 2013, 2018), pysynphot (STScI Development Team 2013), petitRadtrans (Mollière et al. 2019), PyMultinest (Buchner et al. 2014).

Attached Files

Published - Mikal-Evans_2021_AJ_161_18.pdf

Accepted Version - 2011.03470.pdf

Files

2011.03470.pdf

Files (8.3 MB)

Name Size
md5:18aec7b26bef2718f60bc6f7fccf63da
3.4 MB Preview Download
md5:9af4e670147184cd95c480787f960b86
5.0 MB Preview Download

Additional details

Additional titles

Alternative title
Transmission spectroscopy for the warm sub-Neptune HD3167c: evidence for molecular absorption and a possible high metallicity atmosphere

Identifiers

Eprint ID
106968
Resolver ID
CaltechAUTHORS:20201208-105039183

Related works

Describes
https://arxiv.org/abs/2011.03470 (URL)

Funding

NASA
HST-GO-15333
NASA
NAS 5-26555
NASA/JPL/Caltech
NASA
NNX13AC07G
European Research Council (ERC)
832428
NASA
80NSSC19K1727
NASA
18-2XRP18 2-0136
NSF Graduate Research Fellowship
DGE-1339067

Dates

Created
2020-12-09
Created from EPrint's datestamp field
Updated
2021-11-16
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Astronomy Department , Infrared Processing and Analysis Center (IPAC)