On the optical properties of Resonant Drag Instabilities: Variability of Asymptotic Giant Branch and R Coronae Borealis stars

Abstract

In dusty cool-star outflow or ejection events around AGB or RCB-like stars, dust is accelerated by radiation from the star and coupled to the gas via collisional drag forces. But it has recently been shown that such dust-gas mixtures are unstable to a super-class of instabilities called the resonant drag instabilities (RDIs), which promote dust clustering. We therefore consider idealized simulations of the RDIs operating on a spectrum of dust grain sizes subject to radiative acceleration (allowing for different grain optical properties), coupled to the gas with a realistic drag law, including or excluding the effects of magnetic fields and charged grains, and calculate for the first time how the RDIs could contribute to observed variability. We show that the RDIs naturally produce significant variations ($\sim 10-20\%$ $1\sigma$-level) in the extinction, corresponding to $\sim 0.1-1$mag level in the stellar types above, on timescales of order months to a year. The fluctuations are surprisingly robust to finite source-size effects as they are dominated by large-scale modes, which also means their spatial structure could be resolved in some nearby systems. We also quantify how this produces variations in the line-of-sight grain size-distribution. All of these variations are similar to those observed, suggesting that the RDIs may play a key role driving observed variability in dust extinction within dusty outflow/ejection events around cool stars. We further propose that the measured variations in grain sizes could directly be used to identify the presence of the RDIs in close by systems with observations.

arXiv commentsubmitted to MNRAS, 13 pages, 12 Figures, comments welcome!

References in corpus (47)

• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• Interstellar Dust Grains
• GIZMO: A New Class of Accurate, Mesh-Free Hydrodynamic Simulation Methods
• Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars
• Mass loss from hot massive stars
• Particle Clumping and Planetesimal Formation Depend Strongly on Metallicity
• Dynamics of Solids in the Midplane of Protoplanetary Disks: Implications for Planetesimal Formation
• 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
• Accurate, Meshless Methods for Magneto-Hydrodynamics
• The Effect of the Radial Pressure Gradient in Protoplanetary Disks on Planetesimal Formation
• Obscured Asymptotic Giant Branch Variables in the Large Magellanic Cloud and the Period-Luminosity Relation
• Particle-Gas Dynamics with Athena: Method and Convergence
• Resonant Drag Instabilities in protoplanetary disks: the streaming instability and new, faster-growing instabilities
• 2D Models for Dust-driven AGB Star Winds
• A Constrained-Gradient Method to Control Divergence Errors in Numerical MHD
• Astrophysical Weighted Particle Magnetohydrodynamics
• Turbulent Clustering of Protoplanetary Dust and Planetesimal Formation
• The Fundamentally Different Dynamics of Dust and Gas in Molecular Clouds
• The Mira variable S Ori: Relationships between the photosphere, molecular layer, dust shell, and SiO maser shell at 4 epochs
• Study of the inner dust envelope and stellar photosphere of the AGB star R Doradus using SPHERE/ZIMPOL
• Origin of quasi-periodic shells in dust forming AGB winds
• Photochemistry in the inner layers of clumpy circumstellar envelopes: formation of water in C-rich objects and of C-bearing molecules in O-rich objects
• Knots in the Helix Nebula found in H2
• New insights into the dust formation of oxygen-rich AGB stars
• Resonant drag instability of grains streaming in fluids
• Solar-Like Cycle in Asymptotic Giant Branch Stars
• Vigorous atmospheric motion in the red supergiant star Antares
• Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER II. Time variations between pre-maximum and minimum light
• Ubiquitous Instabilities of Dust Moving in Magnetized Gas
• First detection of surface magnetic fields in Post-AGB stars : the cases of U Monocerotis and R Scuti
• Pulsation-triggered mass loss from AGB stars: the 60-day critical period
• Optical and Near-IR Spectra of O-rich Mira Variables : a Comparison between Models and Observations
• The Dynamics of Charged Dust in Magnetized Molecular Clouds
• Dust and molecular shells in asymptotic giant branch stars - Mid-infrared interferometric observations of R Aql, R Aqr, R Hya, W Hya and V Hya
• The Resonant Drag Instability (RDI): Acoustic Modes
• Kinematics of solid particles in a turbulent protoplanetary disc
• Three-component modeling of C-rich AGB star winds. II. The effects of drift in long-period variables
• Local simulations of MRI turbulence with meshless methods
• Nonlinear Evolution of the Resonant Drag Instability in Magnetized Gas
• Simulating the Diverse Instabilities of Dust in Magnetized Gas
• Nonlinear Evolution of Instabilities Between Dust and Sound Waves
• Mid-IR period-magnitude relations for AGB stars
• On the Formation of Multiple-Shells Around Asymptotic Giant Branch Stars
• The Acoustic Resonant Drag Instability with a Spectrum of Grain Sizes
• A Model For the Formation of High Density Clumps in Proto-Planetary Nebulae
• ROAD and K2 photometry of V348 Sgr: probing the pulsation dust connection

Cited by in corpus (2)

• Dust in the Wind with Resonant Drag Instabilities: I. The Dynamics of Dust-Driven Outflows in GMCs and HII Regions
• Resonant Drag Instabilities for Polydisperse Dust, I. The Acoustic Resonant Drag Instability