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Description
alpha Centauri is our closest stellar neighbor, at a distance of only 1.3pc, and its two main components have spectral types comparable to the Sun. This is therefore a favorable target for an imaging search for extrasolar planets. Moreover, indications exist that the gravitational mass of alpha Cen B is higher than its modeled mass, the difference being consistent with a substellar companion of a few tens of Jupiter masses. We searched for faint comoving companions to alpha Cen B. As a secondary objective, we built a catalogue of the detected background sources. We used the NACO adaptive optics system of the VLT in the J, H, and Ks bands to search for companions to alpha Cen B. This instrument allowed us to achieve a very high sensitivity to point-like sources, with a limiting magnitude of m_Ks~18 at 7" from the star. We complemented this data set with archival coronagraphic images from the HST-ACS instrument to obtain an accurate astrometric calibration.
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