A substellar companion around the intermediate-mass giant star HD 11977

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 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 K-1 = 105 m s(-1), 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 M star = 1. 91 M-circle dot, the best- fit minimum mass of the companion and semi- major axis of the, orbit are m(2) sin i = 6. 54 M-Jup and a(2) = 1. 93 AU, respectively. An upper limit for the mass of the companion of m(2) <= 65.5 M-Jup 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- mainsequence star of HD 11977 is probably an A- type star. This discovery gives an indirect evidence for planetary companions sequence around early type main- sequence stars.