Issue |
A&A
Volume 664, August 2022
|
|
---|---|---|
Article Number | A79 | |
Number of page(s) | 30 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202142912 | |
Published online | 11 August 2022 |
K2 and Spitzer phase curves of the rocky ultra-short-period planet K2-141 b hint at a tenuous rock vapor atmosphere
1
Max-Planck-Institut für Astronomie,
Königstuhl 17,
69117
Heidelberg, Germany
e-mail: zieba@mpia.de
2
Leiden Observatory, Leiden University,
Niels Bohrweg 2,
2333
CA Leiden, The Netherlands
3
Centre for Research in Earth and Space Sciences, York University,
4700 Keele St,
Toronto,
ON M3J 1P3
Canada
4
SRON Netherlands Institute for Space Research,
Niels Bohrweg 4,
2333
CA Leiden, The Netherlands
5
Department of Earth & Planetary Sciences, McGill University,
3450 rue University,
QC H3A 0E8
Montréal, Canada
6
Department of Physics, McGill University,
3600 rue University,
Montréal,
QC H3A 2T8
Canada
7
Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford,
Oxford,
OX1 3PU,
UK
8
Université de Montréal, Institut de Recherche sur les Exoplanètes,
1375 Ave.Thérèse-Lavoie-Roux,
Montréal,
QC H2V 0B3
Canada
9
Department of Physics, Oxford University,
Parks Rd,
Oxford,
OX1 3PJ
UK
10
Department of Physics, University of Warwick,
Coventry,
CV4 7AL
UK
11
Eureka Scientific Inc,
Oakland,
CA 94602
USA
12
Dipartimento di Fisica e Astronomia "Galileo Galilei", Università degli Studi di Padova,
Vicolo dell'Osservatorio 3,
35122
Padova, Italy
13
INAF - Osservatorio Astronomico di Padova,
Vicolo dell'Osservatorio 5,
35122
Padova, Italy
14
Johns Hopkins APL,
11100 Johns Hopkins Rd,
MD 20723
Laurel, USA
Received:
14
December
2021
Accepted:
1
March
2022
K2-141 b is a transiting, small (1.5 R⊕) ultra-short-period (USP) planet discovered by the Kepler space telescope orbiting a K-dwarf host star every 6.7 h. The planet's high surface temperature of more than 2000 K makes it an excellent target for thermal emission observations. Here we present 65 h of continuous photometric observations of K2-141 b collected with Spitzer's Infrared Array Camera (IRAC) Channel 2 at 4.5 μm spanning ten full orbits of the planet. We measured an infrared eclipse depth of ppm and a peak to trough amplitude variation of ppm. The best fit model to the Spitzer data shows no significant thermal hotspot offset, in contrast to the previously observed offset for the well-studied USP planet 55 Cnc e. We also jointly analyzed the new Spitzer observations with the photometry collected by Kepler during two separate K2 campaigns. We modeled the planetary emission with a range of toy models that include a reflective and a thermal contribution. With a two-temperature model, we measured a dayside temperature of K and a night-side temperature that is consistent with zero (Tp,n < 1712 K at 2σ). Models with a steep dayside temperature gradient provide a better fit to the data than a uniform dayside temperature (ΔBIC = 22.2). We also found evidence for a nonzero geometric albedo . We also compared the data to a physically motivated, pseudo-2D rock vapor model and a 1D turbulent boundary layer model. Both models fit the data well. Notably, we found that the optical eclipse depth can be explained by thermal emission from a hot inversion layer, rather than reflected light. A thermal inversion may also be responsible for the deep optical eclipse observed for another USP, Kepler-10 b. Finally, we significantly improved the ephemerides for K2-141 b and c, which will facilitate further follow-up observations of this interesting system with state-of-the-art observatories such as James Webb Space Telescope.
Key words: planets and satellites: atmospheres / planets and satellites: individual: K2-141 b / techniques: photometric
© S. Zieba et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
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