Planet host stars with well-constrained ages provide a rare window to the time domain of planet formation and evolution .
The NASA K2 mission has enabled the discovery of the vast majority of known planets transiting stars in clusters , providing a valuable sample of planets with known ages and radii .
We present the discovery of two planets transiting K2-264 , an M2 dwarf in the intermediate age ( 600-800 Myr ) Praesepe open cluster ( also known as the Beehive Cluster , M44 , or NGC 2632 ) , which was observed by K2 during Campaign 16 .
The planets have orbital periods of 5.8 and 19.7 days , and radii of 2.2 \pm 0.2 and 2.7 \pm 0.2 R _ { \earth } , respectively , and their equilibrium temperatures are 496 \pm 10 and 331 \pm 7 K , making this a system of two warm sub-Neptunes .
When placed in the context of known planets orbiting field stars of similar mass to K2-264 , these planets do not appear to have significantly inflated radii , as has previously been noted for some cluster planets .
As the second known system of multiple planets transiting a star in a cluster , K2-264 should be valuable for testing theories of photoevaporation in systems of multiple planets .
Follow-up observations with current near-infrared ( NIR ) spectrographs could yield planet mass measurements , which would provide information about the mean densities and compositions of small planets soon after photoevaporation is expected to have finished .
Follow-up NIR transit observations using Spitzer or large ground-based telescopes could yield improved radius estimates , further enhancing the characterization of these interesting planets .