2018AJ....156..245R

We report the discovery of a compact multi-planet system orbiting the relatively nearby (78 pc) and bright (K = 8.9) K-star, K2-266 (EPIC 248435473). We identify up to six possible planets orbiting K2-266 with estimated periods of P_b = 0.66, P_.02 = 6.1, P_c = 7.8, P_d = 14.7, P_e = 19.5, and P_.06 = 56.7 days, and radii of R_P = 3.3 R_⊕, 0.646 R_⊕, 0.705 R_⊕, 2.93 R_⊕, 2.73 R_⊕, and 0.90 R_⊕, respectively. We are able to confirm the planetary nature of two of these planets (d and e) by analyzing their transit timing variations (m_d=8.9_–3.8^+5.7M_⊕ and m_e=14.3_–5.0^+6.4M_⊕), confidently validate the planetary nature of two other planets (b and c), and classify the last two as planetary candidates (K2-266.02 and .06). From a simultaneous fit of all six possible planets, we find that K2-266 b's orbit has an inclination of 75.°32 while the other five planets have inclinations of 87°-90°. This observed mutual misalignment may indicate that K2-266 b formed differently from the other planets in the system. The brightness of the host star and the relatively large size of the sub-Neptune sized planets d and e make them well-suited for atmospheric characterization efforts with facilities like the Hubble Space Telescope and upcoming James Webb Space Telescope. We also identify an 8.5 day transiting planet candidate orbiting EPIC 248435395, a co-moving companion to K2-266.