Deep imaging survey of the environment of Alpha Centauri - II. CCD imaging with the NTT-SUSI2 camera

摘要

Context: The nearby pair of solar-type stars Alpha Centauri is a favorabletarget for an imaging search for extrasolar planets. Indications exist that thegravitational mass of Alpha Cen B could be higher than its modeled mass, thedifference being consistent with a substellar companion of a few tens ofJupiter masses. However, Alpha Centauri usually appears in star cataloguessurrounded by a large void area, due to the strong diffused light. Aims: Wesearched for faint comoving companions to Alpha Cen located at angulardistances of the order of a few tens of arcseconds, up to 2-3 arcmin. As asecondary objective, we built a catalogue of the detected background sources.Methods: In order to complement our adaptive optics search at small angulardistances (Paper I), we used atmosphere limited CCD imaging from the NTT-SUSI2instrument in the Bessel V, R, I, and Z bands. Results: We present the resultsof our search in the form of a catalogue of the detected objects inside a 5.5arcmin box around this star. A total of 4313 sources down to mV~24 and mI~22were detected from this wide-field survey. We extracted the infrared photometryof part of the detected sources from archive images of the 2MASS survey (JHKbands). We investigate briefly the nature of the detected sources, many of thempresenting extremely red color indices (V-K > 14). Conclusions: We did notdetect any companion to Alpha Centauri between 100 and 300 AU, down to amaximum mass of ~15 times Jupiter. We also mostly exclude the presence of acompanion more massive than 30 MJup between 50 and 100 AU.