A transiting super-Earth close to the inner edge of the habitable zone of an M0 dwarf star

ABSTRACT We present a super-Earth orbiting close to the inner edge of the habitable zone of the cool dwarf star K2-286 (EPIC 249889081), detected with data from the K2 mission in its 15th campaign. The planet has radius of 2.1 ± 0.2 R⊕, near the 1.5–2.0 R⊕ gap in the radii distribution. The equilibrium temperature is $347^{+21}_{-11}$ K, cooler than most of the small planets with well-measured masses, and the orbital period is 27.359 ± 0.005 d. K2-286, located at a distance of 76.3 ± 0.3 pc, is an M0V star with estimated effective temperature of 3926 ± 100 K, less active than other M dwarf stars hosting exoplanets. The expected radial velocity semi-amplitude induced by the planet on the star is $1.9^{+1.3}_{-1.2}$ m s−1, and the amplitude of signals in transit transmission spectroscopy is estimated at 5.0 ± 3.0 ppm. Follow-up observations for mass measurements and transit spectroscopy should be desirable for this relatively bright target (mV = 12.76, mKs = 9.32) hosting a transiting super-Earth within the inner edge of the habitable zone.