Sunday, July 24, 2016

64 Newly Validated Planets from the K2 Mission

Figure 1: Artist's impression of an exoplanet.

Crossfield et al. (2016) present 197 planet candidates discovered using data from the K2 mission. Of these planet candidates, 104 are validated planets, 30 are false positives and 63 remain as planet candidates. Of the 104 validated planets, 64 are newly validated. They include several multi-planet systems and several small, roughly Earth-sized planets receiving Earth-like levels of irradiation. 37 planets are smaller than twice the size of Earth.

4 of the validated planets orbit a red dwarf star identified as K2-72. The 4 planets, referred to as planets "b", "c", "d" and "e", have radii between 1.2 to 1.5 times the radius of Earth, and their orbital periods are 5.58, 7.76, 15.19 and 24.16 days, respectively. Planets "c" and "d" orbit near the 2:1 mean motion resonance, and planets "b" and "c" orbit near the 7:5 mean motion resonance. The two outer planets receive similar amounts of insolation as Earth gets from the Sun.

Figure 2: Transit light curves indicating the presence of the 4 planets around the red dwarf star K2-72. Crossfield et al. (2016)

Other notable validated planets include K2-89b - a highly irradiated, roughly Earth-sized planet in a one-day orbit around a red dwarf star. Another planet is K2-65b. It has 1.58 times the radius of Earth and its orbital period is 12.65 days. It receives roughly 45 times the amount of insolation Earth gets from the Sun. Because K2-65b orbits a relatively bright star, it is a good target for follow-up radial velocity measurements to determine its mass. The sample of validated planets also includes four new two-planet systems - K2-80, K2-83, K2-84 and K2-90.

Figure 3: Orbital periods and radii of the 104 validated planets, 30 false positives, and 63 remaining planet candidates. Crossfield et al. (2016)

Figure 4: Planetary radii, incident insolation, and stellar effective temperature for the 104 validated planets (coloured points) and all planets at the NASA Exoplanet Archive (gray points). Crossfield et al. (2016)

Crossfield et al. (2016), "197 Candidates and 104 Validated Planets in K2's First Five Fields", arXiv:1607.05263 [astro-ph.EP]