Coronagraphic Imaging with the Hubble Space Telescope and the Space Telescope Imaging Spectrograph

Abstract

The unfiltered Space Telescope Imaging Spectrograph (STIS) CCD in tandem with focal plane wedges and a Lyot stop provides a simple white-light coronagraph with a bandpass of 0.2-1.0 mm, which has been used since late 1998 to image nebulosity around stars in the ranges and. The 0.34 ≤ V ≤ 14 0.03 ≤ B V ≤ 1.65 residual starlight seen in STIS coronagraphic images includes diffraction spikes due to the Hubble Space Telescope (HST) secondary support structure, lacks distinct Airy rings, and varies smoothly with radius from the star. The point-spread function (PSF) shape is a strong function of the source spectral energy distribution: we find that the PSF template needs to differ from the occulted source color by mag. Optimal PSF removal D(B V) ≤ 0.08 is achieved for contemporary template observations matched to HST orbital phase of the science observations. Use of noncontemporary PSF templates can degrade the limiting contrast by up to a factor of 10-12 at .