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Tentative Evidence for Water Vapor in the Atmosphere of the Neptune-Size Exoplanet HD 106315 c

Kreidberg, Laura and Mollière, Paul and Crossfield, Ian J. M. and Thorngren, Daniel P. and Kawashima, Yui and Morley, Caroline V. and Benneke, Björn and Mikal-Evans, Thomas and Berardo, David and Kosiarek, Molly and Gorjian, Varoujan and Ciardi, David R. and Christiansen, Jessie L. and Dragomir, Diana and Dressing, Courtney D. and Fortney, Jonathan J. and Fulton, Benjamin J. and Greene, Thomas P. and Hardegree-Ullman, Kevin K. and Howard, Andrew W. and Howell, Steve B. and Isaacson, Howard and Krick, Jessica E. and Livingston, John H. and Lothringer, Joshua D. and Morales, Farisa Y. and Petigura, Erik A. and Rodriguez, Joseph E. and Schlieder, Joshua E. and Weiss, Lauren M. (2020) Tentative Evidence for Water Vapor in the Atmosphere of the Neptune-Size Exoplanet HD 106315 c. . (Unpublished)

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We present a transmission spectrum for the Neptune-size exoplanet HD 106315 c from optical to infrared wavelengths based on transit observations from the Hubble Space Telescope/Wide Field Camera 3, K2, and Spitzer. The spectrum shows tentative evidence for a water absorption feature in the 1.1−1.7μm wavelength range with a small amplitude of 30 ppm (corresponding to just 0.8±0.04 atmospheric scale heights). Based on an atmospheric retrieval analysis, the presence of water vapor is tentatively favored with a Bayes factor of 1.7 - 2.6 (depending on prior assumptions). The spectrum is most consistent with either enhanced metallicity, high altitude condensates, or both. Cloud-free solar composition atmospheres are ruled out at >5σ confidence. We compare the spectrum to grids of cloudy and hazy forward models and find that the spectrum is fit well by models with moderate cloud lofting or haze formation efficiency, over a wide range of metallicities (1−100× solar). We combine the constraints on the envelope composition with an interior structure model and estimate that the core mass fraction is ≳0.3. With a bulk composition reminiscent of that of Neptune and an orbital distance of 0.15 AU, HD 106315 c hints that planets may form out of broadly similar material and arrive at vastly different orbits later in their evolution.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Kreidberg, Laura0000-0003-0514-1147
Crossfield, Ian J. M.0000-0002-1835-1891
Thorngren, Daniel P.0000-0002-5113-8558
Kawashima, Yui0000-0003-3800-7518
Morley, Caroline V.0000-0002-4404-0456
Benneke, Björn0000-0001-5578-1498
Mikal-Evans, Thomas0000-0001-5442-1300
Kosiarek, Molly0000-0002-6115-4359
Ciardi, David R.0000-0002-5741-3047
Christiansen, Jessie L.0000-0002-8035-4778
Dragomir, Diana0000-0003-2313-467X
Dressing, Courtney D.0000-0001-8189-0233
Fortney, Jonathan J.0000-0002-9843-4354
Fulton, Benjamin J.0000-0003-3504-5316
Greene, Thomas P.0000-0002-8963-8056
Hardegree-Ullman, Kevin K.0000-0003-3702-0382
Howard, Andrew W.0000-0001-8638-0320
Howell, Steve B.0000-0002-2532-2853
Isaacson, Howard0000-0002-0531-1073
Krick, Jessica E.0000-0002-2413-5976
Livingston, John H.0000-0002-4881-3620
Lothringer, Joshua D.0000-0003-3667-8633
Morales, Farisa Y.0000-0001-9414-3851
Petigura, Erik A.0000-0003-0967-2893
Rodriguez, Joseph E.0000-0001-8812-0565
Schlieder, Joshua E.0000-0001-5347-7062
Weiss, Lauren M.0000-0002-3725-3058
Additional Information: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 acontract 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. This research made use of matplotlib, a Python library for publication quality graphics (Hunter 2007) This research made use of SciPy (Virtanen et al. 2020) This research made use of NumPy (Van Der Walt et al. 2011). 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. Y.K. acknowledges support from the European Unions Horizon 2020 Research and Innovation Programme under Grant Agreement 776403. L.K. acknowledge M.R. Line for illuminating discussions.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
European Research Council (ERC)832428
European Research Council (ERC)776403
Subject Keywords:Exoplanet atmospheres; Extrasolar ice giants
Record Number:CaltechAUTHORS:20200624-081951243
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103981
Deposited By: Tony Diaz
Deposited On:24 Jun 2020 15:40
Last Modified:24 Jun 2020 15:40

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