The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr

Abstract

ALMA observations of CO(1-0) and CO(2-1) emissions of the circumstellar envelope of EP Aqr, an oxygen-rich AGB star, are reported. A thorough analysis of their properties is presented using an original method based on the separation of the data-cube into a low velocity component associated with an equatorial outflow and a faster component associated with a bipolar outflow. A number of important and new results are obtained concerning the distribution in space of the effective emissivity, the temperature, the density and the flux of matter. A mass loss rate of (1.6$\pm$0.4)10${}^{-7}$ solar masses per year is measured. The main parameters defining the morphology and kinematics of the envelope are evaluated and uncertainties inherent to de-projection are critically discussed. Detailed properties of the equatorial region of the envelope are presented including a measurement of the line width and a precise description of the observed inhomogeneity of both morphology and kinematics. In particular, in addition to the presence of a previously observed spiral enhancement of the morphology at very small Doppler velocities, a similarly significant but uncorrelated circular enhancement of the expansion velocity is revealed, both close to the limit of sensitivity. The results of the analysis place significant constraints on the parameters of models proposing descriptions of the mass loss mechanism, but cannot choose among them with confidence.

arXiv comment26 pages, 31 figures, accepted for publication in MNRAS

References in corpus (39)

• Gaia Data Release 2. Summary of the contents and survey properties
• Too little radiation pressure on dust in the winds of oxygen-rich AGB stars
• A far-infrared survey of bow shocks and detached shells around AGB stars and red supergiants
• A close halo of large transparent grains around extreme red giant stars
• Unexpectedly large mass loss during the thermal pulse cycle of the red giant R Sculptoris!
• Multiple Molecular Winds in Evolved Stars I. A Survey of CO(2-1) and CO(3-2) Emission from 45 Nearby AGB Stars
• The Formation of Very Narrow Waist Bipolar Planetary Nebulae
• Global 3D radiation-hydrodynamics models of AGB stars. Effects of convection and radial pulsations on atmospheric structures
• 2D Models for Dust-driven AGB Star Winds
• The pulsation modes, masses and evolution of luminous red giants
• The wonderful complexity of the Mira AB system
• The dynamical evolution of the circumstellar gas around low-and intermediate-mass stars I: the AGB
• The Red Rectangle: Its Shaping Mechanism and its Source of Ultraviolet Photons
• Properties of detached shells around carbon stars: Evidence of interacting winds
• Further ALMA observations and detailed modeling of the Red Rectangle
• Collimated Outflow Formation via Binary Stars. 3-D Simulations of AGB Wind and Disk Wind Interactions
• Pulsation-triggered mass loss from AGB stars: the 60-day critical period
• Pulsation-triggered dust production by asymptotic giant branch stars
• The "Twin Jet" Planetary Nebula M2-9
• The shock-heated atmosphere of an asymptotic giant branch star resolved by ALMA
• Aperture synthesis imaging of the carbon AGB star R Sculptoris: Detection of a complex structure and a dominating spot on the stellar disk
• Geometry and velocity structure of HD 44179's bipolar jet
• A New Method of Determining the Characteristics of Evolved Binary Systems Revealed in the Observed Circumstellar Patterns: Application to AFGL 3068
• The detached dust and gas shells around the carbon star U Ant
• A detailed view of the gas shell around R Sculptoris with ALMA
• An unusual face-on spiral in the wind of the M-type AGB star EP Aquarii
• HI and CO in the circumstellar environment of the S-type star RS Cnc
• Evidence of a Binary-Induced Spiral from an Incomplete Ring Pattern of CIT 6
• The photodissociation of CO in circumstellar envelopes
• Simplified models of stellar wind anatomy for interpreting high-resolution data: Analytical approach to embedded spiral geometries
• Large-scale environments of binary AGB stars probed by Herschel. II: Two companions interacting with the wind of pi1 Gruis
• The multi-scale environment of RS Cnc from CO and HI observations
• 12CO emission from EP Aqr: Another example of an axi-symmetric AGB wind?
• Constraining the shaping mechanism of the Red Rectangle through spectro-polarimetry of its central star
• Morphology and kinematics of the gas envelope of Mira Ceti
• BIMA CO Observation of EP Aqr the Semiregular Pulsating Star with a Double Component Line Profile
• Space reconstruction of the morphology and kinematics of axisymmetric radio sources
• ALMA observations of the circumstellar envelope around EP Aqr
• De-projection of radio observations of axi-symmetric expanding circumstellar envelopes

Cited by in corpus (11)

• (Sub)stellar companions shape the winds of evolved stars
• Observation of narrow polar jets in the nascent wind of oxygen-rich AGB star EP Aqr
• Circumstellar envelopes of semi-regular long-period variables: mass-loss rate estimates and general model-fitting of the molecular gas
• A detailed view on the circumstellar environment of the M-type AGB star EP Aquarii I. High-resolution ALMA and SPHERE observations
• Revealing new features of the millimetre emission of the circumbinary envelope of Mira Ceti
• How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions -- The case of EP Aqr
• Mira Ceti, atypical archetype
• Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri
• Circumstellar CO J = 3-2 detected around the evolving metal-poor ([Fe/H] ~ -1.15 dex) AGB star RU Vulpeculae
• Infrared interferometric imaging of the compact dust disk around the AGB star HR3126 with the bipolar Toby Jug Nebula
• Probing sulfur chemistry in oxygen-rich AGB stars with ALMA