An Extremely Red Nucleus in an Absorbed QSO atz=0.65

The results of K-band-imaging observations of a candidate of an absorbed QSOat z=0.653, AX J131831+3341, are presented. The B-K color of the object is 4.85mag, which is much redder than optically-selected QSOs. The K-band image showsnuclear and extended components, the same as in the optical V-, R-, and I-bandimages. The nuclear component (I-K = 4.29 mag) is much redder than thepower-law models with energy indices of 0 to -1.0, which well reproduce the V-Rand R-I optical colors of the nuclear component. A heavily absorbed (A_V = 3mag) nucleus may emerge in the K-band, while optical light may originate fromscattered nuclear light. The I-K color of the extended component is 2.2 mag,which is consistent with the post-starburst nature of the host galaxy, which isalso suggested from the V-R and R-I colors of the extended component.Comment: 14 pages with 3 figures, accepted for publication for PAS