Near-Infrared and Optical Limits for the Central X-ray Point Source in the Cassiopeia A Supernova Remnant

Abstract

Near-infrared images of the center of the Cas A supernova remnant taken with the NICMOS 2 camera on HST using the F110W and F160W filters (~J & ~H bands) have magnitude limits of 26.2 and 24.6 respectively, but reveal no sources within a 1.2" radius of the Chandra detected central X-ray point source (XPS). The NICMOS data, taken together with broadband optical magnitude limits (R ~ 28 mag) obtained from a deep STIS CCD exposure taken with a clear filter (50CCD), indicate that the XPS luminosities are very low in the optical/NIR bands (e.g., L_H < 3 x E29 erg/s) with no optical, J, or H band counterpart to the XPS easily detectable by HST. We discuss the nature of the Cas A central compact object based upon these new near-infrared and optical flux limits.