The low-mass companion of HIP 45314 (HR 3672)

Abstract

We report the discovery of a very low mass companion to HIP 45314 (HR 3672) located about 2.7 arcsec north-west of HR 3672 A. With four years of epoch difference between the two observations obtained with the Very Large Telescope we can reject by more than 4σ that B would be a non-moving background object unrelated to A. HR 3672 A is a B 7-8 main-sequence star with an age of 140 ± 80 Myr and from the magnitude difference between HR 3672 A and B and the Two Micron All Sky Survey magnitudes, we can estimate the magnitude of HR 3672 B (K_s = 12.42 ± 0.28 mag) and then, for age and distance of the primary star, using models, its luminosity and mass (0.2-0.5 M_⊙). We present a reanalysis of the probable membership of HR 3672 A to the Platais 9 cluster, and introduce a new method for astrometric calibration of data without dedicated calibration images. In the deepest available image (co-add of all epochs) no additional companion candidates within 13 arcsec were detected down to 0.03 M_⊙.