  We report the discovery of a substellar companion to the intermediate-mass
star HD 11977 (G5 III). Radial velocities of this star have been monitored for
five years with FEROS at the 1.52-m ESO and later at the 2.2-m MPG/ESO
telescope in La Silla, Chile. Based on the collected data we calculated an
orbital solution with a period of P=711 days, a semi-amplitude of K1=105 m/s,
and an eccentricity of e=0.4. The period of the radial-velocity variation is
longer than that of the estimated stellar rotation, rendering it unlikely that
rotational modulation is the source of the variation in the radial velocity.
This hypothesis is supported by the absence of a correlation between stellar
activity indicators and radial-velocity variation. By determining a primary
stellar mass of Mstar=1.91 Msun, the best-fit minimum mass of the companion and
semi-major axis of the orbit are m2sini=6.54 Mjup and a2=1.93 AU, respectively.
An upper limit for the mass of the companion of m2 < 65.5 Mjup has been
calculated from Hipparcos astrometric measurements. Although the possibility of
a brown-dwarf companion cannot be excluded, HD 11977 B is one of the few planet
candidates detected around an intermediate-mass star. The progenitor
main-sequence star of HD 11977 is probably an A-type star. This discovery gives
an indirect evidence for planetary companions around early type main-sequence
stars.
