The Discovery and Mass Measurement of a New Ultra-short-period Planet: K2-131b

• Published in: The Astronomical journal Vol. 154; no. 6; pp. 226 - 242
• Main Authors: Dai, Fei, 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., Bo Justesen, Anders, Livingston, John, Persson, Carina M., Prieto-Arranz, Jorge, Vanderburg, Andrew, Alonso, Roi, Antoniciello, Giuliano, Arriagada, Pamela, Butler, R. P., Cabrera, Juan, Crane, Jeffrey D., Cusano, Felice, Csizmadia, Szilárd, Deeg, Hans, 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, David, Nowak, Grzegorz, Palle, Enric, Pätzold, Martin, Rauer, Heike, Rodríguez, Pilar Montañés, Shectman, Stephen A., Smith, Alexis M. S., Thompson, Ian B., Eylen, Vincent Van, Williamson, Michael W., Wittenmyer, Robert A.
• Format: Journal Article
• Language: English
• Published: Madison The American Astronomical Society 01.12.2017; IOP Publishing
• Subjects: Astronomy; Gaussian process; Planetary mass; planetary systems; Planets; Radial velocity; stars: individual (EPIC 228732031); Stellar activity
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/aa9065

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, K2-131b, was discovered in K2 Campaign 10. It has a radius of 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 and a mean density of g cm−3.