Kepler-454 ( KOI-273 ) is a relatively bright ( V = 11.69 mag ) , Sun-like star that hosts a transiting planet candidate in a 10.6 d orbit .
From spectroscopy , we estimate the stellar temperature to be 5687 \pm 50 K , its metallicity to be [ m/H ] = 0.32 \pm 0.08 , and the projected rotational velocity to be v sin i < 2.4 km s ^ { -1 } .
We combine these values with a study of the asteroseismic frequencies from short cadence Kepler data to estimate the stellar mass to be 1.028 ^ { +0.04 } _ { -0.03 } M _ { \odot } , the radius to be 1.066 \pm 0.012 R _ { \odot } and the age to be 5.25 ^ { +1.41 } _ { -1.39 } Gyr .
We estimate the radius of the 10.6 d planet as 2.37 \pm 0.13 R _ { \oplus } .
Using 63 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 36 observations made with the HIRES spectrograph at Keck Observatory , we measure the mass of this planet to be 6.8 \pm 1.4 M _ { \oplus } .
We also detect two additional non-transiting companions , a planet with a minimum mass of 4.46 \pm 0.12 M _ { J } in a nearly circular 524 d orbit and a massive companion with a period > 10 years and mass > 12.1 M _ { J } .
The twelve exoplanets with radii < 2.7 R _ { \oplus } and precise mass measurements appear to fall into two populations , with those < 1.6 R _ { \oplus } following an Earth-like composition curve and larger planets requiring a significant fraction of volatiles .
With a density of 2.76 \pm 0.73 g cm ^ { -3 } , Kepler-454b lies near the mass transition between these two populations and requires the presence of volatiles and/or H/He gas .