# EPIC 211391664b: A 32-M$_\oplus$ Neptune-sized planet in a 10-day orbit transiting an F8 star [EPA]

We report the discovery of EPIC 211391664b, a transiting Neptune-sized planet monitored by the K2 mission during its campaign 5. We combine the K2 time-series data with ground-based photometric and spectroscopic follow-up observations to confirm the planetary nature of the object and derive its mass, radius, and orbital parameters. EPIC 211391664 b is a warm Neptune-like planet in a 10-day orbit around a V=12.2~mag F-type star with $M_\star$=$1.074\pm0.042 M_{\odot}$, $R_\star$=$1.311 ^{+ 0.083}_{ – 0.048} R_{\odot}$, and age of $5.2_{-1.0}^{+1.2}$~Gyr. We derive a planetary mass and radius of $M_\mathrm{p}$=$32.2 \pm 8.1 M_{\oplus}$ and $R_\mathrm{p}$=$4.3^{+0.3}_{-0.2} R_{\oplus}$. EPIC 211391664b joins the relatively small group of Neptune-sized planets whose mass and radius have been derived with a precision better than 3-$\sigma$. We estimate that the planet will be engulfed by EPIC 211391664 in $\sim$3~Gyr, due to the evolution of the host star towards the red giant branch.

O. Barragan, S. Grziwa, D. Gandolfi, et. al.
Thu, 4 Aug 16
45/70

Comments: 11 pages, 4 figures, submitted to ApJ