The compact circumstellar material around OH 231.8+4.2

Abstract

We have observed the bipolar post-AGB candidate OH 231.8+4.2, using the mid-infrared interferometer MIDI and the infrared camera with the adaptive optics system NACO on the Very Large Telescope. An unresolved core (<200 mas in FWHM) is found at the center of the OH 231.8+4.2 in the 3.8 micron image. This compact source is resolved with the interferometer. We used two 8-meter telescopes with four different baselines, which cover projected baseline lengths from 62 to 47 meters, and projected position angles from 112 to 131 degrees that are almost perpendicular to the bipolar outflow. Fringes from 8 to 9 micron and from 12 to 13.5 micron were clearly detected, whilst the strong silicate self-absorption allows only marginal detection of visibilities between 9 and 12 micron. The fringes from the four baselines consistently show the presence of a compact circumstellar object with an inner radius of 30-40 mas, which is equivalent to 40-50 AU at 1.3 kpc. This clearly shows that the mid-infrared compact source is not the central star (3 AU) but circumstellar material. The measured size of the circumstellar material is consistent with the size of such disks calculated by hydrodynamic models, implying the circumstellar material may have a disk configuration.

Accepted by ApJL High-resolution jpg image is available from http://optik2.mtk.nao.ac.jp/~mikako/photo/oh231_fig1.jpg

References in corpus (5)

• Self-similarity and scaling behavior of IR emission from radiatively heated dust: I. Theory
• A Mid-Infrared Imaging Survey of Proto-Planetary Nebula Candidates
• Bipolar outflows in OH/IR stars
• The sub-arcsecond dusty environment of Eta Carinae
• The Massive Disk Around OH 231.8+4.2

Cited by in corpus (14)

• A mid-infrared imaging catalogue of post-AGB stars
• The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A
• The enigma of the oldest `nova': the central star and nebula of CK Vul
• A disk inside the bipolar planetary nebula M2-9
• VLTI/MIDI 10 micron interferometry of the forming massive star W33A
• Two short mass-loss events that unveil the binary heart of Minkowski's Butterfly Nebula
• Circumstellar ammonia in oxygen-rich evolved stars
• Water vapor and silicon monoxide maser observations in the protoplanetary nebula OH 231.8+4
• Characterizing AGB stars in Wide-field Infrared Survey Explorer (WISE) bands
• Discovery of shocked H2 around OH 231.8+4.2
• Dust shell model of the water fountain source IRAS 16342--3814
• Time variations of H2O and SiO masers in the proto-Planeatry Nebula OH231.8+4.2
• Maser emission during post-AGB evolution
• Infrared interferometric imaging of the compact dust disk around the AGB star HR3126 with the bipolar Toby Jug Nebula