A brown dwarf companion to the intermediate-mass star HR 6037

Context. The frequency of brown dwarf and planetary-mass companions around intermediate-mass stars is still unknown. Imaging and radial velocity surveys have revealed a small number of substellar companions to these stars. Aims. In the course of an imaging survey we detected a visual companion to the intermediate-mass star HR 6037. We here confirm it as a co-moving substellar object. Methods. We present two epoch observations of HR 6037, an A6-type star with a companion candidate at 6 ''.67 and position angle of 294 degrees. We also analyze near-infrared spectroscopy of the companion. Results. Two epoch observations of HR 6037 have allowed us to confirm HR 6037 B as a co-moving companion. Its J and H band spectra suggest that the object has a spectral type of M9, with a surface gravity that is intermediate between a 10 Myr dwarf and a field dwarf of the same spectral type. The comparison of its K-s-band photometry with evolutionary tracks allows us to derive a mass, effective temperature, and surface gravity of 62 +/- 20 M-Jup, T-eff = 2330 +/- 200 K, and log g = 5.1 +/- 0.2, respectively. The low binary mass ratio, q similar to 0.03, and its long orbital period, similar to 5000 yr, make HR 6037 a rare and uncommon binary system.