A Low-mass Exoplanet Candidate Detected by K2 Transiting the Praesepe M Dwarf JS 183

We report the discovery of a repeating photometric signal from a low-mass member of the Praesepe open cluster that we interpret as a Neptune-sized transiting planet. The star is JS 183 (HSHJ 163, EPIC 211916756), with Teff = 3325 100 K, M* = 0.44 0.04 M , R* = 0.44 0.03 R , and . The planet has an o...

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Bibliographic Details
Published in:The Astronomical journal 2017-04, Vol.153 (4), p.177-177
Main Authors: Pepper, Joshua, Gillen, Ed, Parviainen, Hannu, Hillenbrand, Lynne A., Cody, Ann Marie, Aigrain, Suzanne, Stauffer, John, Vrba, Frederick J., David, Trevor, Lillo-Box, Jorge, Stassun, Keivan G., Conroy, Kyle E., Pope, Benjamin J. S., Barrado, David
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Boundaries
DATA ANALYSIS
DENSITY
DETECTION
DWARF STARS
Extrasolar planets
GALAXIES
galaxies: star clusters: individual (Praesepe)
MASS
METALLICITY
Open clusters
ORBITS
Photometry
Planets
planets and satellites: detection
RADIAL VELOCITY
SATELLITES
STAR CLUSTERS
Stars
Transit
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Summary:We report the discovery of a repeating photometric signal from a low-mass member of the Praesepe open cluster that we interpret as a Neptune-sized transiting planet. The star is JS 183 (HSHJ 163, EPIC 211916756), with Teff = 3325 100 K, M* = 0.44 0.04 M , R* = 0.44 0.03 R , and . The planet has an orbital period of 10.134588 days and a radius of RP = 0.32 0.02 RJ. Since the star is faint at V = 16.5 and J = 13.3, we are unable to obtain a measured radial velocity orbit, but we can constrain the companion mass to below about 1.7 MJ, and thus well below the planetary boundary. JS 183b (since designated as K2-95b) is the second transiting planet found with K2 that resides in a several-hundred-megayear open cluster; both planets orbit mid-M dwarf stars and are approximately Neptune sized. With a well-determined stellar density from the planetary transit, and with an independently known metallicity from its cluster membership, JS 183 provides a particularly valuable test of stellar models at the fully convective boundary. We find that JS 183 is the lowest-density transit host known at the fully convective boundary, and that its very low density is consistent with current models of stars just above the fully convective boundary but in tension with the models just below the fully convective boundary.
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/1538-3881/aa62ab