In an effort to measure the masses of planets discovered by the NASA K2 mission , we have conducted precise Doppler observations of five stars with transiting planets .
We present the results of a joint analysis of these new data and previously published Doppler data .
The first star , an M dwarf known as K2-3 or EPICÂ 201367065 , has three transiting planets ( ‘ ‘ b ’ ’ , with radius 2.1 ~ { } R _ { \oplus } ; ‘ ‘ c ’ ’ , 1.7 ~ { } R _ { \oplus } ; and ‘ ‘ d ’ ’ , 1.5 ~ { } R _ { \oplus } ) .
Our analysis leads to the mass constraints : M _ { b } = 8.1 ^ { +2.0 } _ { -1.9 } ~ { } M _ { \oplus } and M _ { c } < 4.2 ~ { } M _ { \oplus } Â ( 95 % Â conf . ) .
The mass of planet d is poorly constrained because its orbital period is close to the stellar rotation period , making it difficult to disentangle the planetary signal from spurious Doppler shifts due to stellar activity .
The second star , a G dwarf known as K2-19 or EPICÂ 201505350 , has two planets ( ‘ ‘ b ’ ’ , 7.7 ~ { } R _ { \oplus } ; and ‘ ‘ c ’ ’ , 4.9 ~ { } R _ { \oplus } ) in a 3:2 mean-motion resonance , as well as a shorter-period planet ( ‘ ‘ d ’ ’ , 1.1 ~ { } R _ { \oplus } ) .
We find M _ { b } = 28.5 ^ { +5.4 } _ { -5.0 } ~ { } M _ { \oplus } , M _ { c } = 25.6 ^ { +7.1 } _ { -7.1 } ~ { } M _ { \oplus } and M _ { d } < 14.0 ~ { } M _ { \oplus } Â ( 95 % Â conf . ) .
The third star , a G dwarf known as K2-24 or EPICÂ 203771098 , hosts two transiting planets ( ‘ ‘ b ’ ’ , 5.7 ~ { } R _ { \oplus } ; and ‘ ‘ c ’ ’ , 7.8 ~ { } R _ { \oplus } ) with orbital periods in a nearly 2:1 ratio .
We find M _ { b } = 19.8 ^ { +4.5 } _ { -4.4 } ~ { } M _ { \oplus } and M _ { c } = 26.0 ^ { +5.8 } _ { -6.1 } ~ { } M _ { \oplus } .
The fourth star , a G dwarf known as EPICÂ 204129699 , hosts a hot Jupiter for which we measured the mass to be 1.857 ^ { +0.081 } _ { -0.081 } ~ { } M _ { \text { Jup } } .
The fifth star , a G dwarf known as EPICÂ 205071984 , contains three transiting planets ( ‘ ‘ b ’ ’ , 5.4 ~ { } R _ { \oplus } ; ‘ ‘ c ’ ’ , 3.5 ~ { } R _ { \oplus } ; and ‘ ‘ d ’ ’ , 3.8 ~ { } R _ { \oplus } ) , the outer two of which have a nearly 2:1 period ratio .
We find M _ { b } = 21.1 ^ { +5.9 } _ { -5.9 } ~ { } M _ { \oplus } , M _ { c } < 8.1 ~ { } M _ { \oplus } Â ( 95 % Â conf . )
and M _ { d } < 35 ~ { } M _ { \oplus } Â ( 95 % Â conf .
) .