Hot Jupiter systems provide unique observational constraints for migration models in multiple systems and binaries .
We report on the discovery of the Kepler-424 ( KOI-214 ) two-planet system , which consists of a transiting hot Jupiter ( Kepler-424b ) in a 3.31-d orbit accompanied by a more massive outer companion in an eccentric ( e = 0.3 ) 223-d orbit .
The outer giant planet , Kepler-424c , is not detected to transit the host star .
The masses of both planets and the orbital parameters for the second planet were determined using precise radial velocity ( RV ) measurements from the Hobby-Eberly Telescope ( HET ) and its High Resolution Spectrograph ( HRS ) .
In stark contrast to smaller planets , hot Jupiters are predominantly found to be lacking any nearby additional planets , the appear to be “ lonely ” ( e.g .
Steffen et al .
2012 ) .
This might be a consequence of a highly dynamical past of these systems .
The Kepler-424 planetary system is a system with a hot Jupiter in a multiple system , similar to \upsilon Andromedae .
We also present our results for Kepler-422 ( KOI-22 ) , Kepler-77 ( KOI-127 ; Gandolfi et al .
2013 ) , Kepler-43 ( KOI-135 ; Bonomo et al .
2012 ) , and Kepler-423 ( KOI-183 ) .
These results are based on spectroscopic data collected with the Nordic Optical Telescope ( NOT ) , the Keck 1 telescope and HET .
For all systems we rule out false positives based on various follow-up observations , confirming the planetary nature of these companions .
We performed a comparison with planetary evolutionary models which indicate that these five hot Jupiters have a heavy elements content between 20 and 120 M _ { \oplus } .