Color Gradients Detected in the HD 15115 Circumstellar Disk
Abstract
We report HST/NICMOS coronagraphic images of the HD 15115 circumstellar disk at 1.1. We find a similar morphology to that seen in the visible and at H band--an edge-on disk that is asymmetric in surface brightness. Several aspects of the 1.1 data are different, highlighting the need for multi-wavelength images of each circumstellar disk. We find a flattening to the western surface brightness profile at 1.1 interior to 2 (90 AU) and a warp in the western half of the disk. We measure the surface brightness profiles of the two disk lobes and create a measure of the dust scattering efficiency between 0.55-1.65 at 1, 2, and 3. At 2 the western lobe has a neutral spectrum up to 1.1 and a strong absorption or blue spectrum >1.1, while a blue trend is seen in the eastern lobe. At 1 the disk has a red F110W-H color in both lobes.