Thermal Emission in the Southwest Clump of VY CMa

Abstract

We present high spatial resolution LBTI/NOMIC $9-12$ $\mu m$ images of VY CMa and its massive outflow feature, the Southwest (SW) Clump. Combined with high-resolution imaging from HST ($0.4-1$ $\mu m$) and LBT/LMIRCam ($1-5$ $\mu m$), we isolate the spectral energy distribution (SED) of the clump from the star itself. Using radiative-transfer code DUSTY, we model both the scattered light from VY CMa and the thermal emission from the dust in the clump to estimate the optical depth, mass, and temperature of the SW Clump. The SW Clump is optically thick at 8.9 $\mu m$ with a brightness temperature of $\sim$200 K. With a dust chemistry of equal parts silicates and metallic iron, as well as assumptions on grain size distribution, we estimate a dust mass of $5.4\times 10^{-5}{M}_{\odot }$. For a gas--to--dust ratio of 100, this implies a total mass of $5.4\times 10^{-3}{M}_{\odot }$. Compared to the typical mass-loss rate of VY CMa, the SW Clump represents an extreme, localized mass-loss event from $\lesssim 300$ years ago.

arXiv commentPublished in AJ, February 2019. 14 pages, 5 figures, 2 tables

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• Episodic Gaseous Outflows and Mass Loss from Red Supergiants
• The Mass-Loss History of the Red Hypergiant VY CMa
• The Unexpected Spectrum of the Innermost Ejecta of the Red Hypergiant VY CMa
• On massive dust clumps in the envelope of the red supergiant VY Canis Majoris
• Red Supergiants, Yellow Hypergiants, and Post-RSG Evolution
• The Red and Yellow Hypergiants