Water vapor and silicon monoxide maser observations in the protoplanetary nebula OH 231.8+4

Abstract

OH 231.8+4.2 is a well studied preplanetary nebula (pPN) around a binary stellar system that shows a remarkable bipolar outflow. To study the structure and kinematics of the inner 10-80 AU nebular regions we performed high-resolution observations of the H${}_2$O 6${}_{1,6}$--5${}_{2,3}$ and ${}^{28}$SiO $v$=2, $J$=1--0 maser emissions with the Very Long Baseline Array. The absolute position of both emission distributions were recovered using the phase referencing technique, and accurately registered in HST optical images. H${}_2$O maser clumps are found to be distributed in two areas of 20 mas in size spatially displaced by $\sim$60 milli-arcseconds along an axis oriented nearly north-south. SiO masers are tentatively found to be placed between the two H${}_2$O maser emitting regions, probably indicating the position of the Mira component of the system. The SiO maser emission traces an inner equatorial component with a diameter of 12 AU, probably a disk rotating around the M-type star. Outwards, we detect in the H${}_2$O data a pair of polar caps, separated by 80 AU. We believe that the inner regions of the nebula probably have been altered by the presence of the companion, leading to an equator-to-pole density contrast that may explain the lack of H${}_2$O masers and strong SiO maser emission in the denser, equatorial regions.

arXiv comment5 pages, 1 figure, A&A accepted

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Cited by in corpus (9)

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• Through the magnifying glass: ALMA acute viewing of the intricate nebular architecture of OH231.8+4.2
• Rotten Egg Nebula: The magnetic field of a binary evolved star
• Maser Properties of the Enigmatic IRAS Source 19312+1950
• VLBA SiO maser observations of the OH/IR star OH 44.8-2.3: magnetic field and morphology
• The Science Case for Simultaneous mm-Wavelength Receivers in Radio Astronomy
• Registration of H${}_2$O and SiO masers in the Calabash Nebula, to confirm the Planetary Nebula paradigm
• On the Nature of the Protoplanetary Nebula OH\,231.8+4.2