The Discovery and Mass Measurement of a New Ultra-short-period Planet: EPIC 228732031b

Dai, F.; Winn, Joshua N.; Gandolfi, Davide; Wang, Sharon X.; Teske, Johanna K.; Burt, Jennifer; Albrecht, Simon; Barragán, Oscar; Cochran, William D.; Endl, Michael; Fridlund, Malcolm; Hatzes, Artie P.; Hirano, Teruyuki; Hirsch, Lea A.; Johnson, Marshall C.; Justesen, Anders Bo; Livingston, John; Persson, Carina M.; Prieto-Arranz, J.; Vanderburg, Andrew; Alonso, R.; Antoniciello, Giuliano; Arriagada, Pamela; Butler, R. P.; Cabrera, Juan; Crane, Jeffrey D.; Cusano, Felice; Csizmadia, Szilárd; Deeg, H. J.; Dieterich, Sergio B.; Eigmüller, Philipp; Erikson, Anders; Everett, Mark E.; Fukui, Akihiko; Grziwa, Sascha; Guenther, Eike W.; Henry, Gregory W.; Howell, Steve B.; Johnson, John Asher; Korth, Judith; Kuzuhara, Masayuki; Narita, Norio; Nespral, D.; Nowak, G.; Palle, E.; Pätzold, Martin; Rauer, Heike; Montañés Rodríguez, P.; Shectman, Stephen A.; Smith, Alexis M. S.; Thompson, Ian B.; Van Eylen, Vincent; Williamson, Michael W.; Wittenmyer, Robert A.
Bibliographical reference

The Astronomical Journal, Volume 154, Issue 6, article id. 226, 17 pp. (2017).

Advertised on:
12
2017
Number of authors
54
IAC number of authors
7
Citations
60
Refereed citations
54
Description
We report the discovery of a new ultra-short-period planet and summarize the properties of all such planets for which the mass and radius have been measured. The new planet, EPIC 228732031b, was discovered in K2 Campaign 10. It has a radius of {1.81}-0.12+0.16 {R}\oplus and orbits a G dwarf with a period of 8.9 hr. Radial velocities obtained with Magellan/PFS and TNG/HARPS-N show evidence for stellar activity along with orbital motion. We determined the planetary mass using two different methods: (1) the “floating chunk offset” method, based only on changes in velocity observed on the same night; and (2) a Gaussian process regression based on both the radial velocity and photometric time series. The results are consistent and lead to a mass measurement of 6.5+/- 1.6 {M}\oplus and a mean density of {6.0}-2.7+3.0 g cm‑3.
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