THE K2-ESPRINT PROJECT IV. A HOT JUPITER IN A PROGRADE ORBIT WITH A POSSIBLE STELLAR COMPANION

Abstract

We report on the detection and early characterization of a hot Jupiter in a three day orbit around K2-34 (EPIC 212110888), a metal-rich F-type star located in the K2 Cycle 5 field. Our follow-up campaign involves precise radial velocity (RV) measurements and high-contrast imaging using multiple facilities. The absence of a bright nearby source in our high-contrast data suggests that the transit-like signals are not due to light variations from such a companion star. Our intensive RV measurements show that K2-34b (EPIC 212110888b) has a mass of 1.773 ± 0.086M[subscript J], confirming its status as a planet. We also detect the Rossiter–McLaughlin effect for K2-34b and show that the system has a good spin–orbit alignment (λ = -1[superscript +10][subscript -9] degrees). High-contrast images obtained by the HiCIAO camera on the Subaru 8.2 m telescope reveal a faint companion candidate (CC) (Δm[subscript H] = 6.19 ± 0.11 mag) at a separation of 0.'' 36. Follow-up observations are needed to confirm that the CC is physically associated with K2-34. K2-34b appears to be an example of a typical "hot Jupiter," albeit one which can be precisely characterized using a combination of K2 photometry and ground-based follow-up. Key words: planets and satellites: detection – stars: individual (EPIC 212110888, K2-34) techniques: photometric – techniques: radial velocities – techniques: spectroscopic