Dust disks around old Pre Main-Sequence stars: HST/NICMOS2 scattered   light images and modeling
  We present recent near-infrared detections of circumstellar disks around the two old PMS Herbig stars HD 141569 and HD 100546 obtained with the HST/NICMOS2 camera. They reveal extended structures larger than 350-400 AU in radius. While the HD 100546 disk appears as a continuous disk down to 40 AU, the HD 141569 environment seems more complex, splitted at least into two dust populations. As a convincing example, the full modeling of the disk surrounding HR 4796, another old PMS star, is detailed and confronted with more recent observations. 
J.C. Augereau (1), A.M. Lagrange (1), D. Mouillet (1) and F. Menard   (1,2) ((1) Laboratoire d'Astrophysique de l'Observatoi...