Surprising detection of an equatorial dust lane on the AGB star IRC+10216

Abstract

Understanding the formation of planetary nebulae remains elusive because in the preceding asymtotic giant branch (AGB) phase these stars are heavily enshrouded in an optically thick dusty envelope. To further understand the morphology of the circumstellar environments of AGB stars we observe the closest carbon-rich AGB star IRC+10216 in scattered light. When imaged in scattered light at optical wavelengths, IRC+10216 surprisingly shows a narrow equatorial density enhancement, in contrast to the large-scale spherical rings that have been imaged much further out. We use radiative transfer models to interpret this structure in terms of two models: firstly, an equatorial density enhancement, commonly observed in the more evolved post-AGB stars, and secondly, in terms of a dust rings model, where a local enhancement of mass-loss creates a spiral ring as the star rotates. We conclude that both models can be used to reproduce the dark lane in the scattered light images, which is caused by an equatorially density enhancement formed by dense dust rather than a bipolar outflow as previously thought. We are unable to place constraints on the formation of the equatorial density enhancement by a binary system.

arXiv comment9 pages, 4 figures

References in corpus (26)

• Modeling optical properties of cosmic dust grains using a distribution of hollow spheres
• Radiative transfer in very optically thick circumstellar disks
• A far-infrared survey of bow shocks and detached shells around AGB stars and red supergiants
• Unexpectedly large mass loss during the thermal pulse cycle of the red giant R Sculptoris!
• Imaging Polarimetric Observations of a New Circumstellar Disk System
• The carrier of the "30" micron emission feature in evolved stars. A simple model using magnesium sulfide
• Warm water vapour in the sooty outflow from a luminous carbon star
• Speckle Suppression Through Dual Imaging Polarimetry, and a Ground-Based Image of the HR 4796A Circumstellar Disk
• 2-Dust : a Dust Radiative Transfer Code for an Axisymmetric System
• Smoke Signals From IRC +10216: 1. Milliarcsecond Proper Motions of the Dust
• The circumstellar envelope of IRC+10216 from milli-arcsecond to arcmin scales
• Optical properties of silicon carbide for astrophysical applications I. New laboratory infrared reflectance spectra and optical constants
• The effects of disk and dust structure on observed polarimetric images of protoplanetary disks
• Data Reduction Techniques for High Contrast Imaging Polarimetry. Applications to ExPo
• An independent distance estimate to CW Leo
• Discovery of multiple dust shells beyond 1 arcmin in the circumstellar envelope of IRC+10216 using Herschel/PACS
• Wide Binary Effects on Asymmetries in Asymptotic Giant Branch Circumstellar Envelopes
• Large-scale environments of binary AGB stars probed by Herschel - I. Morphology statistics and case studies of R Aquarii and W Aquilae
• Bispectrum speckle interferometry of IRC+10216: the dynamic evolution of the innermost circumstellar environment from 1995 to 2001
• The mass-loss return from evolved stars to the Large Magellanic Cloud III. Dust properties for carbon-rich asymptotic giant branch stars
• The color dependent morphology of the post-AGB star HD161796
• Multi-wavelength diffraction-limited imaging of the evolved carbon star IRC +10216, II
• Constraining the Circumbinary Envelope of Z CMa via imaging polarimetry
• Direct imaging of a massive dust cloud around R Coronae Borealis
• Imaging the circumstellar environment of the young T Tauri star SU Aurigae
• Four Decades of IRC +10216: Evolution of a Carbon Rich Dust Shell Resolved at 10 microns with MMT Adaptive Optics and MIRAC4

Cited by in corpus (11)

• (Sub)stellar companions shape the winds of evolved stars
• ALMA data suggest the presence of a spiral structure in the inner wind of CW Leo
• Non-azimuthal linear polarization in protoplanetary disks
• Evolution and Mass Loss of Cool Ageing Stars: a Daedalean Story
• Slowly, slowly in the wind: 3D hydrodynamical simulations of wind mass transfer and angular-momentum loss in AGB binary systems
• HST Images Reveal Dramatic Changes in the Core of IRC+10216
• Monitor variability of millimeter lines in IRC +10216
• BP Piscium: its flaring disk imaged with SPHERE/ZIMPOL
• Multi-frequency high spectral resolution observations of HCN toward the circumstellar envelope of Y CVn
• How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions -- The case of EP Aqr
• Near-infrared Integral-field Spectroscopy of the Wind Forming Region of CW Leo