CO-13 INTERFEROMETRIC OBSERVATIONS OF THE CENTRAL CORE OF CRL-2688

We report the results of mapping observations of a proto-planetary neb ula CRL 2688 in the 13CO J = 1-0 line with a beam size of 4''.4 x 3''. 9 with Nobeyama Millimeter Array. Emission of 13CO is extended by abou t 15'', which is about one-fourth of the CO envelope size obseved by s ingle-dish telescopes. The channel velocity maps show that 13CO emissi on consists of three components: a spherically symmetric high-brightne ss core at the center, a less bright extended envelope with clumpy str ucture, and a high-velocity component near the center. The high-bright ness central core is found to extend by about 10'' and to appear spher ically symmetric. The disk- or torus-like structure which was previous ly observed by others in several molecular lines is not seen in the 13 CO maps. This indicates that the gas density in the envelope does not vary much with the polar angle. The extended component is observed to spread along the symmetry axis. The peak positions of the red- and blu eshifted features of the high-velocity component are found to be separ ated by about 3''.