APERTURE SYNTHESIS OBSERVATIONS OF HCN J=1-0 EMISSION FROM Y-CANUM-VENATICORUM

We have made high resolution observations of HCN (1-0) emission from t he carbon star Y Canum Venaticorum using the Nobeyama Millimeter Array . We find that the emission region is not well resolved by the synthes ised beam of 3.7'' x 4.6'' over the entire velocity range (V-LSR = 10 to 35 km s(-1)). We find that the true brightness temperature probably exceeds 200 It at many velocity channels as well as at the 26 km s(-1 ) maser spike. The broad emission component may be the result of super imposed maser spikes. The high brightness requires an unreasonably hig h HCN fractional abundance if LTE is assumed. It is likely that the HC N abundance previously reported for the star is considerably affected by the maser action. A new maser spike has been found at V-LSR = 29 km s(-1).