We report the discovery of two transiting planets orbiting K2-290 ( EPIC 249624646 ) , a bright ( V=11.11 ) late F-type star residing in a triple-star system .
It was observed during Campaign 15 of the K2 mission , and in order to confirm and characterise the system , follow-up spectroscopy and AO imaging were carried out using the FIES , HARPS , HARPS-N , and IRCS instruments .
From AO imaging and Gaia data we identify two M-dwarf companions at a separation of 113 \pm 2 AU and 2467 _ { -155 } ^ { +177 } AU .
From radial velocities , K2 photometry , and stellar characterisation of the host star , we find the inner planet to be a mini-Neptune with a radius of 3.06 \pm 0.16 R _ { \earth } and an orbital period of P = 9.2 days .
The radius of the mini-Neptune suggests that the planet is located above the radius valley , and with an incident flux of F \sim 400 F _ { \earth } , it lies safely outside the super-Earth desert .
The outer warm Jupiter has a mass of 0.774 \pm 0.047 M _ { J } and a radius of 1.006 \pm 0.050 R _ { J } , and orbits the host star every 48.4 days on an orbit with an eccentricity e < 0.241 .
Its mild eccentricity and mini-Neptune sibling suggest that the warm Jupiter originates from in situ formation or disk migration .