On the possibility of ground-based direct imaging detection of extra-solarplanets: the case of TWA-7

We show that ground-based direct imaging detection of extra-solar planets i s possible with current technology. As an example, we present evidence for a possible planetary companion to the young T Tauri star 1RXSJ104230.3-3340 14 (=TWA-7), discovered by ROSAT as a member of the nearby TW Hya associati on. In an HST NICMOS F160W image, an object is detected that is more than 9 mag fainter than TWA-7, located 2.445+/-0.035 " south-east at a position a ngle of 142.24+/-1.34 degrees. One year later using the ESO-NTT with the SH ARP speckle camera, we obtained H- and K-band detections of this faint obje ct at a separation of 2.536 +/- 0.077 " and a position angle of 139.3 +/- 2 .1 degrees. Given the known proper motion of TWA-7, the pair may form a pro per motion pair. If the faint object orbits TWA-7, then its apparent magnit udes of H=16.42 +/- 0.11 and K=16.34 +/- 0.15 mag yield absolute magnitudes consistent with a similar to 10(6.5) yr old similar to 3 M-jup mass object according to the non-gray theory by Burrows et al. (1997). At similar to 5 5 pc, the angular separation of similar to 2.5 " corresponds to similar to 138 AU, clearly within typical disk sizes. However, position angles and sep arations are slightly more consistent with a background object than with a companion.