The effect of winds on atmospheric layers of red supergiants II. Modelling VLTI/GRAVITY and MATISSE observations of AH Sco, KW Sgr, V602 Car, CK Car and V460 Car

Abstract

Mass loss plays a crucial role in the lives of massive stars, especially as the star leaves the main sequence and evolves to the red supergiant (RSG) phase. However, the physical processes that trigger mass-loss events in RSGs are not well understood. Recently, we showed that adding a static wind to a MARCS atmospheric model can accurately reproduce observed extensions in the atmospheres of RSGs. In this work, we compute synthetic observables that match new interferometric data of the RSGs AH Sco, KW Sgr, V602 Car, CK Car, and V460 Car obtained with VLTI/MATISSE and GRAVITY. We computed model spectra and visibilities and found the best-fit model, mass-loss rate, and best-fit angular Rosseland diameter for the observations. We matched our model to the data, covering a wavelength range of $1.8-5.0\mu$m, which corresponds to the $K$, $L,$ and $M$ bands. Our models reproduce the spectro-interferometric data over this wide wavelength range, including extended atmospheric layers of CO, H${}_2$O, and SiO. We obtain Rosseland angular diameters between $3.0<{\theta }_{\mathrm{Ross}}<5.5$ mas and mass-loss rates of $-6.5<\log \dot{M}/M_{\odot }{\mathrm{yr}}^{-1}<-4$. The partial pressure of SiO relative to the gas pressure and the SiO 4.0$\mu$m line intensity increase between 2 and 3 stellar radii. The relative intensity depends on the luminosity used for our models, since the more luminous models have a higher mass-loss rate. This work further demonstrates that our MARCS+wind model can reproduce the observed physical extension of RSG atmospheres for several spectral diagnostics spanning a broad wavelength range. We reproduce both spectra and visibilities of newly obtained data as well as provide temperature and density stratifications that are consistent with the observations. With the MATISSE data, we newly include the extension of SiO layers as a precursor of silicate dust.

Accepted for publication in A&A

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