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A Featureless Infrared Transmission Spectrum for the Super-puff Planet Kepler-79d

Chachan, Yayaati and Jontof-Hutter, Daniel and Knutson, Heather A. and Adams, Danica and Gao, Peter and Benneke, Björn and Berta-Thompson, Zachory and Dai, Fei and Deming, Drake and Ford, Eric B. and Lee, Eve J. and Libby-Roberts, Jessica E. and Madhusudhan, Nikku and Wakeford, Hannah R. and Wong, Ian (2020) A Featureless Infrared Transmission Spectrum for the Super-puff Planet Kepler-79d. Astronomical Journal, 160 (5). Art. No. 201. ISSN 1538-3881. doi:10.3847/1538-3881/abb23a.

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Extremely low-density planets ("super-puffs") are a small but intriguing subset of the transiting planet population. With masses in the super-Earth range (1 – 10 M_⊕) and radii akin to those of giant planets (> 4 R_⊕), their large envelopes may have been accreted beyond the water snow line and many appear to be susceptible to catastrophic mass loss. Both the presence of water and the importance of mass loss can be explored using transmission spectroscopy. Here, we present new Hubble space telescope WFC3 spectroscopy and updated Kepler transit depth measurements for the super-puff Kepler-79d. We do not detect any molecular absorption features in the 1.1 − 1.7 μm WFC3 bandpass, and the combined Kepler and WFC3 data are consistent with a flat-line model, indicating the presence of aerosols in the atmosphere. We compare the shape of Kepler-79d's transmission spectrum to predictions from a microphysical haze model that incorporates an outward particle flux due to ongoing mass loss. We find that photochemical hazes offer an attractive explanation for the observed properties of super-puffs like Kepler-79d, as they simultaneously render the near-infrared spectrum featureless and reduce the inferred envelope mass-loss rate by moving the measured radius (optical depth unity surface during transit) to lower pressures. We revisit the broader question of mass-loss rates for super-puffs and find that the age estimates and mass-loss rates for the majority of super-puffs can be reconciled if hazes move the photosphere from the typically assumed pressure of ~10 mbar to ~10 µbar.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Chachan, Yayaati0000-0003-1728-8269
Jontof-Hutter, Daniel0000-0002-6227-7510
Knutson, Heather A.0000-0002-0822-3095
Adams, Danica0000-0001-9897-9680
Gao, Peter0000-0002-8518-9601
Benneke, Björn0000-0001-5578-1498
Berta-Thompson, Zachory0000-0002-3321-4924
Dai, Fei0000-0002-8958-0683
Deming, Drake0000-0001-5727-4094
Ford, Eric B.0000-0001-6545-639X
Lee, Eve J.0000-0002-1228-9820
Libby-Roberts, Jessica E.0000-0002-2990-7613
Madhusudhan, Nikku0000-0002-4869-000X
Wakeford, Hannah R.0000-0003-4328-3867
Wong, Ian0000-0001-9665-8429
Additional Information:© 2020 The American Astronomical Society. Received 2020 April 21; revised 2020 August 18; accepted 2020 August 18; published 2020 October 15. We are indebted to the reviewer for apt and useful suggestions that improved this manuscript. This work is based on observations from the Hubble Space Telescope, operated by AURA, Inc. on behalf of NASA/ESA. Support for this work was provided by NASA through Space Telescope Science Institute grants GO-14260 and GO-15138. P. Gao and I. Wong acknowledge the generous support of the Heising-Simons Foundation via the 51 Pegasi b fellowship in Planetary Astronomy. E. B. F. acknowledges support from the Penn State Eberly College of Science and Department of Astronomy & Astrophysics and the Center for Exoplanets and Habitable Worlds. We would also like to thank Jim Fuller, Sarah Millholland, Dave Stevenson, and Shreyas Vissapragada for helpful discussions and feedback. Software: Astropy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018), BATMAN (Kreidberg 2015), emcee (Foreman-Mackey et al. 2012), LDTk (Parviainen & Aigrain 2015), Matplotlib (Hunter 2007), NumPy (Oliphant 2006; Van Der Walt et al. 2011), PLATON (Zhang et al. 2019).
Funding AgencyGrant Number
Heising-Simons Foundation51 Pegasi b Fellowship
Eberly College of ScienceUNSPECIFIED
Center for Exoplanets and Habitable WorldsUNSPECIFIED
Subject Keywords:Exoplanet atmospheres ; Exoplanet evolution ; Exoplanets
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet atmospheres (487); Exoplanet evolution (491); Exoplanets (498)
Record Number:CaltechAUTHORS:20200817-120211517
Persistent URL:
Official Citation:Yayaati Chachan et al 2020 AJ 160 201
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104979
Deposited By: Tony Diaz
Deposited On:17 Aug 2020 19:27
Last Modified:16 Nov 2021 18:38

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