Synthetic photometry for carbon-rich giants. V. Effects of grain-size-dependent dust opacities

Abstract

The properties and the evolution of asymptotic giant branch (AGB) stars are strongly influenced by their mass loss through a stellar wind. This is believed to be caused by radiation pressure due to the absorption and scattering of the stellar radiation by the dust grains formed in the atmosphere. The optical properties of dust are often estimated using the small particle limit (SPL) approximation, and it has been used frequently in modelling AGB stellar winds when performing radiation-hydrodynamics (RHD) simulations. We aim to investigate the effects of replacing the SPL approximation by detailed Mie calculations of the size-dependent opacities for grains of amorphous carbon forming in C-rich AGB star atmospheres. We performed RHD simulations for a large grid of carbon star atmosphere+wind models with different effective temperatures, luminosities, stellar masses, carbon excesses, and pulsation properties. Also, a posteriori radiative transfer calculations for many radial structures (snapshots) of these models were done, resulting in spectra and filter magnitudes. We find, when giving up the SPL approximation, the wind models become more strongly variable and more dominated by gusts, although the average mass-loss rates and outflow speeds do not change significantly; the increased radiative pressure on the dust throughout its formation zone does, however, result in smaller grains and lower condensation fractions (and thus higher gas-to-dust ratios). The photometric K magnitudes are generally brighter, but at V the effects of using size-dependent dust opacities are more complex: brighter for low mass-loss rates and dimmer for massive stellar winds. Given the large effects on spectra and photometric properties, it is necessary to use the detailed dust optical data instead of the simple SPL approximation in stellar atmosphere+wind modelling where dust is formed.

arXiv comment14 pages, 24 figures. Accepted for publication in Astronomy \& Astrophysics

References in corpus (39)

• Constraining the thermally-pulsing asymptotic giant branch phase with resolved stellar populations in the Small Magellanic Cloud
• Models of circumstellar molecular radio line emission: Mass loss rates for a sample of bright carbon stars
• Near-Infrared Photometry of Carbon Stars
• Synthetic photometry for carbon rich giants, I. Hydrostatic dust-free models
• Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud
• ExoMol molecular line lists -- XXXVII: spectra of acetylene
• Structure of the Large Magellanic Cloud from 2MASS
• Dust driven mass loss from carbon stars as a function of stellar parameters - I. A grid of Solar-metallicity wind models
• Line formation in AGB atmospheres including velocity effects. Molecular line profile variations of long period variables
• Dynamic atmospheres and winds of cool luminous giants, I. Al${}_2$O${}_3$ and silicate dust in the close vicinity of M-type AGB stars
• Study of the inner dust envelope and stellar photosphere of the AGB star R Doradus using SPHERE/ZIMPOL
• Variable stars in the Magellanic Clouds: II. The data and infrared properties
• Synthetic photometry for M and K giants and stellar evolution: hydrostatic dust-free model atmospheres and chemical abundances
• The evolved-star dust budget of the Small Magellanic Cloud: the critical role of a few key players
• Synthetic photometry for carbon-rich giants. IV. An extensive grid of dynamic atmosphere and wind models
• The APM Survey for Cool Carbon Stars in the Galactic Halo - II The Search for Dwarf Carbon Stars
• A new method to identify subclasses among AGB stars using Gaia and 2MASS photometry
• ExoMol line lists XXXI: Spectroscopy of lowest eights electronic states of C${}_2$
• Carbon stars identified from LAMOST DR4 using Machine Learning
• The mass-loss, expansion velocities and dust production rates of carbon stars in the Magellanic Clouds
• Synthetic photometry for carbon-rich giants II. The effects of pulsation and circumstellar dust
• Estimating the dust production rate of carbon stars in the Small Magellanic Cloud
• An update to the MARVEL dataset and ExoMol line list for 12C2
• Carbon stars in the X-shooter Spectral Library
• The VMC survey III. Mass-loss rates and luminosities of LMC AGB stars
• Characterisation of Galactic carbon stars and related stars from Gaia-EDR3
• Carbon stars as standard candles: I. The luminosity function of carbon stars in the Magellanic Clouds
• Aperture synthesis imaging of the carbon AGB star R Sculptoris: Detection of a complex structure and a dominating spot on the stellar disk
• Carbon star wind models at solar and sub-solar metallicities: a comparative study. I. Mass loss and the properties of dust-driven winds
• Observing and modeling the dynamic atmosphere of the low mass-loss C-star R Sculptoris at high angular resolution
• Carbon-Rich Mira Variables: Radial Velocities and Distances
• Astrophysical Distance Scale II. Application of the JAGB Method: A Nearby Galaxy Sample
• Dust driven mass loss from carbon stars as function of stellar parameters - II. Effects of grain size on wind properties
• Synthetic photometry for carbon-rich giants. III. Tracing the sequence of mass-losing galactic C-type Miras
• Carbon stars as standard candles: II. The median J magnitude as a distance indicator
• The VMC Survey -- XXXVII. Pulsation periods of dust enshrouded AGB stars in the Magellanic Clouds
• Milky Way Zero-Point Calibration of the JAGB Method: Using Thermally Pulsing AGB Stars in Galactic Open Clusters
• Carbon stars with increased oxygen and nitrogen abundances: hydrostatic dust-free model atmospheres
• A Preliminary Calibration of the JAGB Method Using Gaia EDR3

Cited by in corpus (1)

• Dynamic atmosphere and wind models of C-type asymptotic giant branch stars. Influences of dust optical data on mass loss and observables