Discovery of a low-mass companion around HR3549

We report the discovery of a low-mass companion to HR3549, an A0V star surrounded by a debris disk with a warm excess detected by WISE at 22 $\mu$m ($10\sigma$ significance). We imaged HR3549 B in the L-band with NAOS-CONICA, the adaptive optics infrared camera of the Very Large Telescope, in January 2013 and confirmed its common proper motion in January 2015. The companion is at a projected separation of $\simeq 80$ AU and position angle of $\simeq 157^\circ$,soitisorbitingwellbeyondthewarmdiskinneredgeof$r > 10$ AU. Our age estimate for this system corresponds to a companion mass in the range 15-80 $M_J$, spanning the brown dwarf regime, and so HR3549 B is another recent addition to the growing list of brown dwarf desert objects with extreme mass ratios. The simultaneous presence of a warm disk and a brown dwarf around HR3549 provides interesting empirical constraints on models of the formation of substellar companions.