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A Mirage or an Oasis? Water Vapor in the Atmosphere of the Warm Neptune TOI-674 b

Brande, Jonathan and Crossfield, Ian J. M. and Kreidberg, Laura and Oklopčić, Antonija and Polanski, Alex S. and Barman, Travis and Benneke, Björn and Christiansen, Jessie L. and Dragomir, Diana and Foreman-Mackey, Daniel and Fortney, Jonathan J. and Greene, Thomas P. and Howard, Andrew W. and Knutson, Heather A. and Lothringer, Joshua D. and Mikal-Evans, Thomas and Morley, Caroline V. (2022) A Mirage or an Oasis? Water Vapor in the Atmosphere of the Warm Neptune TOI-674 b. Astronomical Journal, 164 (5). Art. No. 197. ISSN 0004-6256. doi:10.3847/1538-3881/ac8b7e.

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We report observations of the recently discovered warm Neptune TOI-674 b (5.25 R_⊕, 23.6 M_⊕) with the Hubble Space Telescope’s Wide Field Camera 3 instrument. TOI-674 b is in the Neptune desert, an observed paucity of Neptune-size exoplanets at short orbital periods. Planets in the desert are thought to have complex evolutionary histories due to photoevaporative mass loss or orbital migration, making identifying the constituents of their atmospheres critical to understanding their origins. We obtained near-infrared transmission spectroscopy of the planet’s atmosphere with the G141 grism. After extracting, detrending, and fitting the spectral light curves to measure the planet’s transmission spectrum, we used the petitRADTRANS atmospheric spectral synthesis code to perform retrievals on the planet’s atmosphere to identify which absorbers are present. These results show moderate evidence for increased absorption at 1.4 μm due to water vapor at 2.9σ (Bayes factor = 15.8), as well as weak evidence for the presence of clouds at 2.2σ (Bayes factor = 4.0). TOI-674 b is a strong candidate for further study to refine the water abundance, which is poorly constrained by our data. We also incorporated new TESS short-cadence optical photometry, as well as Spitzer/IRAC data, and refit the transit parameters for the planet. We find the planet to have the following transit parameters: Rₚ/R_* = 0.1135 ± 0.0006, T₀ = 2458544.523792 ± 0.000452 BJD, and P = 1.977198 ± 0.00007 day. These measurements refine the planet radius estimate and improve the orbital ephemerides for future transit spectroscopy observations of this highly intriguing warm Neptune.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemDiscussion paper
Brande, Jonathan0000-0002-2072-6541
Crossfield, Ian J. M.0000-0002-1835-1891
Kreidberg, Laura0000-0003-0514-1147
Oklopčić, Antonija0000-0002-9584-6476
Polanski, Alex S.0000-0001-7047-8681
Barman, Travis0000-0002-7129-3002
Benneke, Björn0000-0001-5578-1498
Christiansen, Jessie L.0000-0002-8035-4778
Dragomir, Diana0000-0003-2313-467X
Foreman-Mackey, Daniel0000-0002-9328-5652
Fortney, Jonathan J.0000-0002-9843-4354
Greene, Thomas P.0000-0002-8963-8056
Howard, Andrew W.0000-0001-8638-0320
Knutson, Heather A.0000-0002-5375-4725
Lothringer, Joshua D.0000-0003-3667-8633
Mikal-Evans, Thomas0000-0001-5442-1300
Morley, Caroline V.0000-0002-4404-0456
Additional Information:This work was conducted on the ancestral territory of the Kaw, Osage, and Shawnee peoples. We thank Paul Mollière and Evert Nasedkin for their extremely helpful assistance with petitRADTRANS. This work was supported in part by a grant from the NASA Interdisciplinary Consortia for Astrobiology Research (ICAR). This research made use of the open-source Python package ExoCTK, the Exoplanet Characterization Toolkit (Bourque et al. 2021).
Group:Astronomy Department, Division of Geological and Planetary Sciences, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Issue or Number:5
Record Number:CaltechAUTHORS:20221031-575177800.20
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117658
Deposited By: Research Services Depository
Deposited On:05 Nov 2022 21:39
Last Modified:07 Nov 2022 18:24

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