Context : For the past 3 years we have been monitoring 62 K giant stars using precise stellar radial velocity ( RV ) measurements with the 2m Alfred Jensch Telescope of the Thüringer Landessternwarte Tautenburg ( TLS ) .

Aims : To probe the dependence of planet formation on stellar mass by finding planets around intermediate-mass giant stars .

Methods : We present high accuracy RV measurements of the K1.5 III star 42 Dra and the K4 III star HD 139357 .
The wavelength reference for the RV measurements was provided by an iodine absorption cell placed in the optical path of the spectrograph .

Results : Our measurements reveal that the time series of the radial velocity of 42 Dra shows a periodic variation of 479.1 days with a semiamplitude of K = 112.5 m s ^ { -1 } .
An orbital solution yields a mass function of f ( m ) = ( 5.29 \pm 0.62 ) \times 10 ^ { -8 } solar masses ( M _ { \odot } ) and an eccentricity of e = 0.38 \pm 0.06 .
From our template spectra , taken without the iodine cell , we determine a metallicity of - 0.46 \pm 0.04 dex and a stellar mass of 0.98 \pm 0.06 M _ { \odot } for this star . HD 139357 shows periodic RV variations of 1125.7 days with a semiamplitude K = 159.9 m s ^ { -1 } .
An orbital solution yields an eccentricity , e = 0.10 \pm 0.02 and mass function , f ( m ) = ( 4.79 \pm 0.57 ) \times 10 ^ { -7 } M _ { \odot } .
An iron abundance of - 0.13 \pm 0.04 dex is obtained , and a stellar mass of 1.31 \pm 0.24 M _ { \odot } for the parent star is derived .
An analysis of the HIPPARCOS photometry as well as our H \alpha core flux measurements reveal no variability with the radial velocity period .
Keplerian motion is the most likely explanation for the observed radial velocity variations for these stars .

Conclusions : The K giant stars 42 Dra and HD 139357 host extrasolar planets with “ minimum masses ” of 3.88 \pm 0.85 Jupiter masses M _ { \mathrm { Jup } } and 9.76 \pm 2.15 M _ { \mathrm { Jup } } , respectively .