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We present the results of a survey to detect low-mass companions of UMa groupmembers, carried out in 2003-2006 with NACO at the ESO VLT. While manyextra-solar planets and planetary candidates have been found in close orbitsaround stars by the radial velocity and the transit method, direct detectionsat wider orbits are rare. The Ursa Major (UMa) group, a young stellarassociation at an age of about 200-600 Myr and an average distance of 25 pc,has not yet been addressed as a whole although its members represent a veryinteresting sample to search for and characterize sub-stellar companions bydirect imaging. Our goal was to find or to provide detection limits on widesub-stellar companions around nearby UMa group members using high-resolutionimaging. We searched for faint companions around 20 UMa group members within 30pc. The primaries were placed below a semi-transparent coronagraph, a ratherrarely used mode of NACO, to increase the dynamic range of the images. In mostcases, second epoch images of companion candidates were taken to check whetherthey share common proper motion with the primary. Our coronagraphic images ruleout sub-stellar companions around the stars of the sample. A dynamical range oftypically 13-15 mag in the Ks band was achieved at separations beyond 3" fromthe star. Candidates as faint as Ks ~ 20 were securely identified and measured.The survey is most sensitive between separations of 100 and 200 au but only onaverage because of the very different target distance. Field coverage reachesabout 650 au for the most distant targets. Most of the 200 candidates arevisible in two epochs. All of those were rejected being distant backgroundobjects.

A coronagraphic search for wide sub-stellar companions among members of the Ursa Major moving group