Evidence for a Binary System at the Core of the Bipolar Proto–planetary Nebula OH 231.8+4.2

Abstract

We present Very Large Array observations of H2O and OH (1612 MHz) maser emission made toward the proto-planetary nebula OH 231.8+4.2. The H2O observations show two features at vLSR of 23.1 and 44.5 km s-1, located at α(1950) = 07h39m5898 ± 001, δ(1950) = -14°35'420 ± 01, coinciding in position within error with the SiO (v = 1; J = 2-1) maser position recently given by Sanchez Contreras et al. The H2O and SiO masers are most likely tracing the position of QX Pup, the Mira variable near the center of OH 231.8+4.2. This position is, however, clearly offset by ~1'' from the axis of the bipolar outflow traced by the OH maser emission. The OH (1612 MHz) maser emission spectrum shows three main components at vLSR of 5.8, 20.0, and 27.4 km s-1, distributed over a region of 2'' whose position and kinematics appear to trace the bipolar outflow of this source. These results suggest the presence of a binary system: one invisible star powering the bipolar outflow and the other, the Mira star QX Pup, associated with the H2O and SiO masers. However, this scenario requires that the two stars have evolved at very similar rates (implying very similar masses).