An Improved Transit Measurement for a 2.4 R{sub ⊕} Planet Orbiting A Bright Mid-M Dwarf K2–28
- Department of Physics, California Institute of Technology, Pasadena, CA 91125 (United States)
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)
- Harvard University, Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
- NASA Exoplanet Science Institute, California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA 91125 (United States)
- Département de Physique, Université de Montréal, Montreal, H3T 1J4 (Canada)
- IPAC MC 314-6 California Institute of Technology 1200 E. California Boulevard, Pasadena, CA 91125 (United States)
- MIT-Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139 (United States)
- Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, CA 94035 (United States)
- Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
We present a new Spitzer transit observation of K2–28b, a sub-Neptune (R {sub p} = 2.45 ± 0.28 R {sub ⊕}) orbiting a relatively bright (V {sub mag} = 16.06, K {sub mag} = 10.75) metal-rich M4 dwarf (EPIC 206318379). This star is one of only seven with masses less than 0.2 M{sub ⊙} known to host transiting planets, and the planet appears to be a slightly smaller analogue of GJ 1214b (2.85±0.20 R{sub ⊕}). Our new Spitzer observations were taken two years after the original K2 discovery data and have a significantly higher cadence, allowing us to derive improved estimates for this planet’s radius, semimajor axis, and orbital period, which greatly reduce the uncertainty in the prediction of near future transit times for the James Webb Space Telescope (JWST) observations. We also evaluate the system’s suitability for atmospheric characterization with JWST and find that it is currently the only small (<3 R{sub ⊕}) and cool (<600 K) planet aside from GJ 1214b with a potentially detectable secondary eclipse. We also note that this system is a favorable target for near-infrared radial velocity instruments on larger telescopes (e.g., the Habitable Planet Finder on the Hobby–Eberly Telescope), making it one of only a handful of small, cool planets accessible with this technique. Finally, we compare our results with the simulated catalog of the Transiting Exoplanet Survey Satellite (TESS) and find K2–28b to be representative of the kind of mid-M systems that should be detectable in the TESS sample.
- OSTI ID:
- 22897465
- Journal Information:
- The Astronomical Journal (Online), Vol. 155, Issue 5; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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