K2-260 b: A hot Jupiter transiting an F star, and K2-261 b: A warm Saturn around a bright G star

Johnson, M. C., Dai, F., Justesen, A. B., Gandolfi, D., Hatzes, A. P., Nowak, G., Endl, M., Cochran, W. D., Hidalgo, D., Watanabe, N., Parviainen, H., Hirano, T., Villanueva, S., Prieto-Arranz, J., Narita, N., Palle, E., Guenther, E. W., Barragán, O., Trifonov, T., Niraula, P., MacQueen, P. J., Cabrera, J., Csizmadia, Sz, Eigmüller, Ph, Grziwa, S., Korth, J., Pätzold, M., Smith, A. M.S., Albrecht, S., Alonso, R., Deeg, H., Erikson, A., Esposito, M., Fridlund, M., Fukui, A., Kusakabe, N., Kuzuhara, M., Livingston, J., Montañes Rodriguez, P., Nespral, D., Persson, C. M., Purismo, T., Raimundo, S., Rauer, H., Ribas, I., Tamura, M., Van Eylen, V. and Winn, J. N. (2018) K2-260 b: A hot Jupiter transiting an F star, and K2-261 b: A warm Saturn around a bright G star. Monthly Notices Of The Royal Astronomical Society, 481 (1), 596-612. (doi:10.1093/mnras/sty2238).

Abstract

We present the discovery and confirmation of two new transiting giant planets from the Kepler extended mission K2. K2-260 b is a hot Jupiter transiting a V = 12.7 F6V star in K2 Field 13, with a mass and radius of M = 1.39_-0.06^+0.05 M_⊙ and R = 1.69 ± 0.03 R. The planet has an orbital period of P = 2.627 d, and a mass and radius of M_P = 1.42_-0.32^+0.31 M_J and R_P = 1.552_-0.057^+0.048 R_J. This is the first K2 hot Jupiter with a detected secondary eclipse in the Kepler bandpass, with a depth of 71 ± 15 ppm, which we use to estimate a geometric albedo of A_g ~ 0.2. We also detected a candidate stellar companion at 0.6 arcsec from K2-260; we find that it is very likely physically associated with the system, in which case it would be an M5-6V star at a projected separation of ~400 au. K2-261 b is a warm Saturn transiting a bright (V = 10.5) G7IV/V star in K2 Field 14. The host star is a metal rich ([Fe/H] = 0.36 ± 0.06), mildly evolved 1.10_-0.02^+0.01 M_⊙ star with R = 1.65 ± 0.04 R. Thanks to its location near the main-sequence turn-off, we can measure a relatively precise age of 8.8_-0.3^+0.4 Gyr. The planet has P = 11.633 d, M_P = 0.223 ± 0.031 M_J, and R_P = 0.850_-0.022^+0.026 R_J, and its orbit is eccentric (e = 0.39 ± 0.15). Its brightness and relatively large transit depth make this one of the best-known warm Saturns for follow-up observations to further characterize the planetary system.

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Contributors

Author: S. Raimundo

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