Broken symmetry: The structure of the dust envelope of IRC +10216

Abstract

view Abstract Citations (56) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Broken Symmetry: The Structure of the Dust Envelope of IRC +10216 Kastner, Joel H. ; Weintraub, David A. Abstract We present polarimetric, coronagraphic near-infrared images of the reflection nebula surrounding the carbon star IRC +10216. These images demonstrate convincingly that the dust envelope is not spherically symmetric. In unocculted images at J (1.25 micrometers) and in occulted images at H (1.65 micrometers) and K (2.2 micrometers), the nebula appears elongated, with major axis lying at position angle approximately 20 deg. The position angle of elongation is the same as that previously determined from near-infrared speckle interferometry for the inner approximately 1 sec of the envelope. The elliptical symmetry of the J polarimetric map offers additional evidence of the axial symmetry of the envelope and indicates that the equatorial plane of IRC +10216 lies perpendicular to the major axis of the nebula. The polarization map also indicates that the source of illumination -- presumably the stellar photosphere or hot dust located very near the photosphere -- is directly detected at wavelengths as short as approximately 1 micrometers. We find that the density distribution of grains in the polar regions is roughly n varies as r-2 and estimate that the scattering dust mass within 12 sec in radius of the central star is approximately 5 x 10-6 solar masses. These results support a model in which the envelope of IRC +10216 is weakly bipolar and is viewed at an intermediate inclination angle such that we have a direct line of sight to the central star. The axisymmetric near-infrared intensity and polarization morphologies are best understood in terms of enhanced mass loss in the equatorial plane. An examination of previous near-infrared and millimeter-wave mapping observations supports this hypothesis. These observations make clear that axisymmetric structure can be well established before an intermediate-mass star leaves the asymptotic giant branch. It is possible that the dust envelope of IRC +10216 presents an early manifestation of the more profound bipolar structure that characterizes highly evolved preplanetary nebulae. Publication: The Astrophysical Journal Pub Date: October 1994 DOI: 10.1086/174774 Bibcode: 1994ApJ...434..719K Keywords: Broken Symmetry; Carbon Stars; Cosmic Dust; Density Distribution; Infrared Astronomy; Optical Polarization; Reflection Nebulae; Stellar Envelopes; Astronomical Interferometry; Astronomical Polarimetry; Coronagraphs; Infrared Imagery; Stellar Evolution; Astronomy; ISM: DUST; EXTINCTION; ISM: STRUCTURE; POLARIZATION; ISM: REFLECTION NEBULAE; STARS: CARBON; STARS: INDIVIDUAL ALPHANUMERIC: IRC; 10216 full text sources ADS | data products SIMBAD (6)