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Multi-orbital-phase and Multiband Characterization of Exoplanetary Atmospheres with Reflected Light Spectra

Damiano, Mario and Hu, Renyu and Hildebrandt, Sergi R. (2020) Multi-orbital-phase and Multiband Characterization of Exoplanetary Atmospheres with Reflected Light Spectra. Astronomical Journal, 160 (5). Art. No. 206. ISSN 1538-3881. https://resolver.caltech.edu/CaltechAUTHORS:20201012-150703263

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Abstract

Direct imaging of widely separated exoplanets from space will obtain their reflected light spectra and measure atmospheric properties. Previous calculations have shown that a change in the orbital phase would cause a spectral signal, but whether this signal may be used to characterize the atmosphere has not been shown. We simulate starshade-enabled observations of the planet 47 UMa b, using the present most realistic simulator Starshade Imaging Simulation Toolkit for Exoplanet Reconnaissance to estimate the uncertainties due to residual starlight, solar glint, and exozodiacal light. We then use the Bayesian retrieval algorithm EXOREL^R to determine the constraints on the atmospheric properties from observations using a Roman- or Habitable Exoplanet Observatory (HabEx)-like telescope, comparing the strategies to observe at multiple orbital phases or in multiple wavelength bands. With a ~20% bandwidth in 600–800 nm on a Roman-like telescope, the retrieval finds a degenerate scenario with a lower gas abundance and a deeper or absent cloud than the truth. Repeating the observation at a different orbital phase or at a second 20% wavelength band in 800–1000 nm, with the same integration time and thus degraded signal-to-noise ratio (S/N), would effectively eliminate this degenerate solution. Single observation with a HabEx-like telescope would yield high-precision constraints on the gas abundances and cloud properties, without the degenerate scenario. These results are also generally applicable to high-contrast spectroscopy with a coronagraph with a similar wavelength coverage and S/N, and can help design the wavelength bandwidth and the observation plan of exoplanet direct-imaging experiments in the future.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-3881/abb76aDOIArticle
https://arxiv.org/abs/2009.08579arXivDiscussion Paper
ORCID:
AuthorORCID
Damiano, Mario0000-0002-1830-8260
Hu, Renyu0000-0003-2215-8485
Hildebrandt, Sergi R.0000-0003-0220-0009
Alternate Title:Multi-orbital-phase and multi-band characterization of exoplanetary atmospheres with reflected light spectra
Additional Information:© 2020 The American Astronomical Society. Received 2020 July 7; revised 2020 September 3; accepted 2020 September 8; published 2020 October 15. The authors thank Dr. Graça M. Rocha for helpful discussions in the preparation of this manuscript, Dr. Stefan Martin for providing the optical throughput and the detector quantum efficiency used by Roman Coronagraph and HabEx, and Dr. Andrew Romero-Wolf for providing Roman's QE value at EOL. Finally, we also thank the anonymous referee for the valuable comments provided which greatly helped to improve the manuscript. This work was supported in part by the NASA WFIRST Science Investigation Teams grant #NNN16D016T. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Funders:
Funding AgencyGrant Number
NASANNN16D016T
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:Astronomical techniques ; Direct imaging ; Spectroscopy ; Exoplanet atmospheres ; Exoplanet atmospheric composition ; Bayesian statistics ; Posterior distribution
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Astronomical techniques (1684); Direct imaging (387); Spectroscopy (1558); Exoplanet atmospheres (487); Exoplanet atmospheric composition (2021); Bayesian statistics (1900); Posterior distribution (1926)
Record Number:CaltechAUTHORS:20201012-150703263
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20201012-150703263
Official Citation:Mario Damiano et al 2020 AJ 160 206
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105991
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Oct 2020 22:27
Last Modified:16 Oct 2020 18:31

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