Detection of HCO toward the planetary nebula K3-35

We report the first detection of HCO (1–0) toward the young planetary nebula K3-35. This planetary nebula (PN) is particularly interesting because it is one ot the two PNe that exhibit water maser emission. The persistence of water molecules in this PN could be related with the presence of a massive molecular envelope responsible for shielding the water molecules against the ionizing radiation from the core of the star. We used the emission of HCO to estimate the molecular mass in this PN which resulted in about 0.15 M supporting that K3-35 is a very young PN. Also, from the HCO column density and the ratio of molecular to ionized mass it can be observed that this molecule is present in significant amounts at a very early stage of the evolution of PNe.