2007AJ....133..364T

We report the detection, for the first time, of HCO⁺(J=1⟶0) emission, as well as marginal CO(J=1⟶0) emission, toward the planetary nebula (PN) K3-35 as a result of a molecular survey carried out toward this source. We also report new observations of the previously detected CO(J=2⟶1) and water maser emission, as well as upper limits for the emission of the SiO, H¹³CO⁺, HNC, HCN, HC₃OH, HC₅N, CS, HC₃N, ¹³CO, CN, and NH₃ molecules. From the ratio of CO(J=2⟶1) to CO(J=1⟶0) emission we have estimated the kinetic temperature of the molecular gas, obtaining a value of ≃20 K. Using this result we have estimated a molecular mass for the envelope of ≃0.017 M_☉ and an HCO⁺ abundance relative to H₂ of 6x10^–7, similar to the abundances found in other PNe. K3-35 is remarkable because it is one of the two PNe reported to exhibit water maser emission, which is present in the central region, as well as at a distance of ≃5000 AU from the center. The presence of molecular emission provides some clues that could help in understanding the persistence of water molecules in the envelope of K3-35. The HCO⁺ emission could be arising in dense molecular clumps, which may provide the shielding mechanism that protects water molecules in this source.