Two small temperate planets transiting nearby M dwarfs in K2 campaigns 0 and 1
- NASA Ames Research Center, Space Science and Astrobiology Division, MS 245-6, Moffett Field, CA 94035 (United States)
- Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ (United States)
- California Institute of Technology, Pasadena, CA 91125 (United States)
- Institute for Astronomy, University of Hawai‘i, 2680 Woodlawn Drive, Honolulu, HI (United States)
- Astronomy Department, University of California, Berkeley, CA (United States)
- NASA Exoplanet Science Institute, California Institute of Technology, 770 S. Wilson Ave., Pasadena, CA 91125 (United States)
- Université Grenoble Alpes, IPAG, 38000, Grenoble, 38000, Grenoble (France)
- University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States)
- Department of Astrophysics, Princeton University, Princeton NJ 08544 (United States)
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA (United States)
- Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)
- Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States)
- Institute for Astronomy, University of Hawai‘i at Mānoa, Hilo, HI 96720-2700 (United States)
The prime Kepler mission revealed that small planets (<4 R{sub ⊕}) are common, especially around low-mass M dwarfs. K2, the repurposed Kepler mission, continues this exploration of small planets around small stars. Here we combine K2 photometry with spectroscopy, adaptive optics imaging, and archival survey images to analyze two small planets orbiting the nearby field-age M dwarfs, K2-26 (EPIC 202083828) and K2-9. K2-26 is an M1.0±0.5 dwarf at 93 ± 7 pc from K2 Campaign 0. We validate its planet with a day period of 14.5665 and estimate a radius of 2.67{sub −0.42}{sup +0.46} R{sub ⊕}. K2-9 is an M2.5±0.5 dwarf at 110 ± 12 pc from K2 Campaign 1. K2-9b was first identified by Montet et al.; here we present spectra and adaptive optics imaging of the host star and independently validate and characterize the planet. Our analyses indicate K2-9b is a 2.25{sub −0.96}{sup +0.53} R{sub ⊕} planet with a 18.4498 day period. K2-26b exhibits a transit duration that is too long to be consistent with a circular orbit given its measured stellar radius. Thus, the long transits are likely due to the photoeccentric effect and our transit fits hint at an eccentric orbit. Both planets receive low incident flux from their host stars and have estimated equilibrium temperatures <500 K. K2-9b may receive approximately Earth-like insolation. However, its host star exhibits strong GALEX UV emission which could affect any atmosphere it harbors. K2-26b and K2-9b are representatives of a poorly studied class of small planets with cool temperatures that have radii intermediate to Earth and Neptune. Future study of these systems can provide key insight into trends in bulk composition and atmospheric properties at the transition from silicate dominated to volatile rich bodies.
- OSTI ID:
- 22887038
- Journal Information:
- Astrophysical Journal, Vol. 818, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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