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A Transmission Spectrum of the Sub-Earth Planet L98-59 b in 1.1-1.7 μm

Damiano, Mario and Hu, Renyu and Barclay, Thomas and Zieba, Sebastian and Kreidberg, Laura and Brande, Jonathan and Colón, Knicole D. and Covone, Giovanni and Crossfield, Ian and Domagal-Goldman, Shawn D. and Fauchez, Thomas J. and Fiscale, Stefano and Gallo, Francesco and Gilbert, Emily and Hedges, Christina L. and Kite, Edwin S. and Kopparapu, Ravi K. and Kostov, Veselin B. and Morley, Caroline and Mullally, Susan E. and Pidhorodetska, Daria and Schlieder, Joshua E. and Quintana, Elisa V. (2022) A Transmission Spectrum of the Sub-Earth Planet L98-59 b in 1.1-1.7 μm. Astronomical Journal, 164 (5). Art. No. 225. ISSN 0004-6256. doi:10.3847/1538-3881/ac9472.

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With the increasing number of planets discovered by the Transit Exoplanet Survey Satellite, the atmospheric characterization of small exoplanets is accelerating. L98-59 is an M-dwarf hosting a multiplanet system, and so far, four small planets have been confirmed. The innermost planet b is ∼15% smaller and ∼60% lighter than Earth, and should thus have a predominantly rocky composition. The Hubble Space Telescope observed five primary transits of L98-59 b in 1.1–1.7 μm, and here we report the data analysis and the resulting transmission spectrum of the planet. We measure the transit depths for each of the five transits and, by combination, we obtain a transmission spectrum with an overall precision of ∼20 ppm in for each of the 18 spectrophotometric channels. With this level of precision, the transmission spectrum does not show significant modulation, and is thus consistent with a planet without any atmosphere or a planet having an atmosphere and high-altitude clouds or haze. The scenarios involving an aerosol-free, H₂-dominated atmosphere with H₂O or CH₄ are inconsistent with the data. The transmission spectrum also disfavors, but does not rule out, an H₂O-dominated atmosphere without clouds. A spectral retrieval process suggests that an H₂-dominated atmosphere with HCN and clouds or haze may be the preferred solution, but this indication is nonconclusive. Future James Webb Space Telescope observations may find out the nature of the planet among the remaining viable scenarios.

Item Type:Article
Related URLs:
URLURL TypeDescription
Damiano, Mario0000-0002-1830-8260
Hu, Renyu0000-0003-2215-8485
Barclay, Thomas0000-0001-7139-2724
Zieba, Sebastian0000-0003-0562-6750
Kreidberg, Laura0000-0003-0514-1147
Brande, Jonathan0000-0002-2072-6541
Colón, Knicole D.0000-0001-8020-7121
Covone, Giovanni0000-0002-2553-096X
Crossfield, Ian0000-0002-1835-1891
Domagal-Goldman, Shawn D.0000-0003-0354-9325
Fauchez, Thomas J.0000-0002-5967-9631
Fiscale, Stefano0000-0001-8371-8525
Gilbert, Emily0000-0002-0388-8004
Hedges, Christina L.0000-0002-3385-8391
Kite, Edwin S.0000-0002-1426-1186
Kopparapu, Ravi K.0000-0002-5893-2471
Kostov, Veselin B.0000-0001-9786-1031
Morley, Caroline0000-0002-4404-0456
Mullally, Susan E.0000-0001-7106-4683
Pidhorodetska, Daria0000-0001-9771-7953
Schlieder, Joshua E.0000-0001-5347-7062
Quintana, Elisa V.0000-0003-1309-2904
Additional Information:We thank A. Youngblood for assistance with the HST observations. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained 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. These observations are associated with program 15856. Support for program #15856 was provided by NASA through a grant from the Space Telescope Science Institute. This work was supported by the GSFC Sellers Exoplanet Environments Collaboration (SEEC), which is funded by the NASA Planetary Science Divisions Internal Scientist Funding Mode. The material is based on work supported by NASA under award No. 80GSFC21M0002. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Funding AgencyGrant Number
NASANAS 5-26555
Issue or Number:5
Record Number:CaltechAUTHORS:20221110-430367300.7
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117823
Deposited By: Research Services Depository
Deposited On:23 Nov 2022 16:43
Last Modified:28 Nov 2022 17:25

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