CO content of bipolar planetary nebulae

We report high-sensitivity millimeter-wave CO observations of recently disc overed bipolar planetary nebulae (PNe). Three objects (BV 5-1, K 3-94 and K 3-24) have been detected, and one of them (BV 5-1) is resolved by the simi lar to 10 " telescope beam. The envelopes of the three newly detected objec ts display values of the molecular to ionized mass ratio of similar to 0.2, and sizes of similar to 0.1 pc. This indicates that these PNe are rather e volved, with K 3-24 being the youngest of the three (similar to 10(3) years ) according to its CO line profile and kinematic ages. In BV 5-1, the molecular gas appears to be distributed in an irregular disk or ring surrounding the central star and perpendicular to the bipolar nebu la. This is similar to the situation found in other better studied bipolar PNe (e.g. NGC 2346, M 2-9, KjPn8), and thus seems to be the rule in this cl ass of objects. This suggests a common mechanism for the rings and the bipo lar flows that shape the optical nebula.