Space telescope imaging spectrograph coronagraphic observations of β Pictoris

We present new coronagraphic images of beta Pictoris obtained with the Space Telescope Imaging Spectrograph (STIS) in 1997 September. The high-resolution images (0 ".1) clearly detect the circumstellar disk as close to the star as 0 ".75, corresponding to a projected radius of 15 AU. The images define the warp in the disk with greater precision and at closer radii to beta Pic than do previous observations. They show that the warp can be modeled by the projection of two components: the main disk and a fainter component, which is inclined to the main component by 4 degrees-5 degrees and extends only as far as approximate to 4 " from the star. We interpret the main component as arising primarily in the outer disk and the tilted component as defining the inner region of the disk. The observed properties of the warped inner disk are inconsistent with a driving force from stellar radiation. However, warping induced by the gravitational potential of one or more planets is consistent with the data. Using models of planet-warped disks constructed by Larwood & Papaloizou, we derive possible masses of the perturbing object.