The dusty circumstellar environment of Betelgeuse during the Great Dimming as seen by VLTI/MATISSE

Abstract

The 'Great Dimming' of the prototypical red supergiant Betelgeuse, which occurred between December 2019 and April 2020, gives us unprecedented insight into the processes occurring on the stellar surface and in the inner wind of this type of star. In particular it may bring further understanding of their dust nucleation and mass loss processes. Here, we present and analyse VLTI/MATISSE observations in the N-band (8 - 13 $\mu$m) taken near the brightness minimum in order to assess the status of the dusty circumstellar environment. We explore the compatibility of a dust clump obscuring the star with our mid-infrared interferometric observations using continuum 3D radiative transfer modelling, and probe the effect of adding multiple clumps close to the star on the observables. We also test the viability of a large cool spot on the stellar surface without dust present in the ambient medium. Using the visibility data, we derive a uniform disk diameter of 59.02 $\pm$ 0.64 mas in the spectral range 8 to 8.75 $\mu$m. We find that both the dust clump and the cool spot models are compatible with the data. Further to this, we note that the extinction and emission of our localised dust clump in the line of sight of the star, directly compensate each other making the clump undetectable in the spectral energy distribution and visibilities. The lack of infrared brightening during the 'Great Dimming' therefore does not exclude extinction due to a dust clump as one of the possible mechanisms. The visibilities can be reproduced by a spherical wind with dust condensing at 13 stellar radii and a dust mass-loss rate of (2.1 - 4.9) $\times$ 10${}^{-10}$ $M_{\odot }{\mathrm{yr}}^{-1}$, however, in order to reproduce the complexity of the observed closure phases, additional surface features or dust clumps would be needed.

13 Pages, accepted for publication in A&A

References in corpus (26)

• A new mass-loss rate prescription for red supergiants
• The dust condensation sequence in red super-giant stars
• Atmospheric dynamics and the mass loss process in red supergiant stars
• Final Moments I: Precursor Emission, Envelope Inflation, and Enhanced Mass loss Preceding the Luminous Type II Supernova 2020tlf
• A dusty veil shading Betelgeuse during its Great Dimming
• Standing on the shoulders of giants: New mass and distance estimates for Betelgeuse through combined evolutionary, asteroseismic, and hydrodynamical simulations with MESA
• The close circumstellar environment of Betelgeuse - V. Rotation velocity and molecular envelope properties from ALMA
• Betelgeuse Just Isn't That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse
• The close circumstellar environment of Betelgeuse - II. Diffraction-limited spectro-imaging from 7.76 to 19.50 microns with VLT/VISIR
• Stellar atmospheric parameters for 754 spectra from the X-shooter Spectral Library
• The Photospheric Temperatures of Betelgeuse during the Great Dimming of 2019/2020: No New Dust Required
• Analytic, dust-independent mass-loss rates for red supergiant winds initiated by turbulent pressure
• An Updated 2017 Astrometric Solution for Betelgeuse
• Properties of the CO and H${}_2$O MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observations
• The molecular and dusty composition of Betelgeuse's inner circumstellar environment
• Spatially Resolved Ultraviolet Spectroscopy of the Great Dimming of Betelgeuse
• Atmosphere of Betelgeuse before and during the Great Dimming event revealed by tomography
• The inhomogeneous sub-millimeter atmosphere of Betelgeuse
• The Mass-Loss History of the Red Hypergiant VY CMa
• Betelgeuse fainter in the sub-millimetre too: an analysis of JCMT and APEX monitoring during the recent optical minimum
• Detection of `parent' molecules from the inner wind of AGB stars as tracers of non-equilibrium chemistry
• NOEMA maps the CO $J=2-1$ environment of the red supergiant $\mu$ Cep
• The Great Dimming of Betelgeuse seen by the Himawari-8 meteorological satellite
• The impact of winds on the spectral appearance of Red Supergiants
• Imaging the outward motions of clumpy dust clouds around the red supergiant Antares with VLT/VISIR
• The inner circumstellar dust of the red supergiant Antares as seen with VLT/SPHERE/ZIMPOL

Cited by in corpus (5)

• Images of Betelgeuse with VLTI/MATISSE across the Great Dimming
• The Great Dimming of Betelgeuse: the photosphere as revealed by tomography over the past 15 years
• Reconstructing the mid-infrared environment in the stellar merger remnant V838 Monocerotis
• Betelgeuse's Buddy: X-Ray Constraints on the Nature of $\alpha$ Ori B
• Red Supergiants in the Milky Way and Nearby Galaxies