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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. . (Unpublished)

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We report observations of the recently discovered super-Neptune TOI-674 b (5.25 Earth radii, 23.6 Earth mass) with the Hubble Space Telescope's Wide Field Camera 3 instrument. TOI-674 b is deep into 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, which we detrended and fit. After extracting the transmission spectrum from the data, 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 evidence for increased absorption at 1.4 μm due to water vapor at 2.1σ (Bayes factor = 3.2). With these results, TOI-674 b joins the exclusive club of exoplanets with featured transmission spectra. 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 re-fit the transit parameters for the planet. We find the planet to have the following transit parameters: R_p/R_∗ = 0.1135±0.0006, T₀ = 2458544.523792 ± 0.000452 BJD, and P = 1.977198 ± 0.00007 d. 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:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper ItemJournal Article
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.0000-0002-0822-3095
Lothringer, Joshua D.0000-0003-3667-8633
Mikal-Evans, Thomas0000-0001-5442-1300
Morley, Caroline V.0000-0002-4404-0456
Additional Information:Attribution 4.0 International (CC BY 4.0). We thank Paul Mollière and Evert Nasedkin for their extremely helpful assistance with petitRADTRANS. This research made use of the open source Python package ExoCTK, the Exoplanet Characterization Toolkit (Bourque et al. 2021). Facilities: HST, TESS, Spitzer, MAST, ExoFOP, Exoplanet Archive Software: astropy (Astropy Collaboration et al. 2013, 2018), ExoCTK (Bourque et al. 2021), exoplanet (ForemanMackey et al. 2021), petitRADTRANS (Mollière et al. 2019, 2020), Iraclis (Tsiaras et al. 2016a,b, 2018)
Group:Astronomy Department, Division of Geological and Planetary Sciences
Classification Code:Exoplanet atmospheres (487) — Exoplanet atmospheric composition (2021) — Transmission spectroscopy (2133) — M stars (985) — Near infrared astronomy (1093) — Hubble Space Telescope (761)
Record Number:CaltechAUTHORS:20220228-183224134
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113637
Deposited By: George Porter
Deposited On:01 Mar 2022 20:34
Last Modified:04 Nov 2022 18:48

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