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

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 $M_{\star }=1.39_{-0.06}^{+0.05}{M}_{\odot }$ and $R_{\star }=1.69\pm 0.03R_{\odot }$. The planet has an orbital period of $P=2.627$ days, 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 $71\pm 15$ ppm, which we use to estimate a geometric albedo of $A_g\sim 0.2$. We also detected a candidate stellar companion at 0.6" 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 $\sim 400$ 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]$=0.36\pm 0.06$), mildly evolved $1.10_{-0.02}^{+0.01}{M}_{\odot }$ star with $R_{\star }=1.65\pm 0.04R_{\odot }$. 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 $P=11.633$ days, $M_P=0.223\pm 0.031M_J$, and $R_P=0.850_{-0.022}^{+0.026}{R}_J$, and its orbit is eccentric ($e=0.39\pm 0.15$). 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.

Published in MNRAS. 18 pages, 10 figures