Radial velocity measurements of K2-3 & GJ3470

Supplementing K2 photometry with follow-up Spitzer transit observations refined the transit ephemerides of K2-3 b, c, and d by over a factor of 10. We analyze ground-based photometry from the Evryscope and Fairborn Observatory to determine the characteristic stellar activity timescales for our Gaussian Process fit, including the stellar rotation period and activity region decay timescale.

The stellar rotation signals for both stars are evident in the radial velocity data and is included in our fit using a Gaussian process trained on the photometry. We find the masses of K2-3 b, K2-3 c, and GJ3470 b to be 6.48_-0.93_^+0.99^, 2.14_-1.04_^+1.08^, and 12.58_-1.28_^+1.31^ M_{Earth}_, respectively. K2-3 d was not significantly detected and has a 3{sigma} upper limit of 2.80 M_{Earth}_.