Observations and Radiative Transfer Simulations of the Carbon-rich AGB star V Oph with VLTI/MATISSE

TL;DR

This study combines interferometric observations and radiative transfer modeling to analyze the dust and gas distribution around the carbon-rich AGB star V Oph, revealing changes over its pulsational cycle.

Contribution

It presents the first detailed radiative transfer models of V Oph's circumstellar environment using VLTI/MATISSE data at different pulsation phases.

Findings

Stellar radii of 395 and 495 R_sun at different phases

Dust shell radii of 790 and 742.5 R_sun

Good fit to visibility spectra with gas and dust models

Abstract

Carbon-rich Asymptotic Giant Branch (AGB) stars are among the most important contributors of enriched materials to the interstellar medium due to their strong stellar winds. To fully characterize mass loss on the AGB, it is necessary to determine the distributions of dust and gas around the stars, where the dust begins to condense from the gas, and how this extended atmospheric structure evolves over the pulsational period of the star. We present an analysis of L-band (2.8-4.2 $\mu$m) interferometric observations of the carbon-rich AGB star V Oph made with the MATISSE instrument at the VLTI at the maximum and minimum of the star's visual light curve. Using the radiative transfer software RADMC-3D, we model the circumstellar dust shell, and find stellar radii of 395 and 495 $R_{\odot}$ at the two phases, and dust radii of 790 and 742.5 $R_{\odot}$ at the two epochs, respectively. By adding C$_2$H$_2$ and HCN gas to the RADMC-3D models, we are able to fit the visibility spectra well, with some deviations at the 3.11 $\mu$m feature. Reasons for this deviation and interpretation of the best fitting models are discussed in the text, and we discuss motivations for follow-up imaging observations of V Oph.