Spatially resolving the inhomogeneous structure of the dynamical atmosphere of Betelgeuse with VLTI/AMBER

Abstract

We present spatially resolved high-spectral resolution K-band observations of the red supergiant Betelgeuse (alpha Ori) using AMBER at the Very Large Telescope Interferometer (VLTI). Betelgeuse was observed between 2.28 and 2.31 micron using baselines of 16, 32, and 48m with spectral resolutions of 4800 -- 12000. Spectrally dispersed interferograms have been obtained in the 2nd, 3rd, and 5th lobes, which represents the highest spatial resolution (9 mas) achieved for Betelgeuse, corresponding to 5 resolution elements over its stellar disk. The AMBER data in the continuum can be reasonably fitted by a uniform disk with a diameter of 43.19+/-0.03 mas or a limb-darkening disk with 43.56+/-0.06 mas. The K-band interferometric data taken at various epochs suggest that Betelgeuse seen in the continuum shows much smaller deviations from the above uniform/limb-darkened disk than predicted by 3-D convection simulations. On the other hand, our AMBER data in the CO lines reveal that the blue and red wings of the CO lines originate in spatially distinct regions over the stellar disk, indicating an inhomogeneous velocity field. Our AMBER data in the CO lines can be roughly explained by a simple model, in which a patch of CO gas is moving outward or inward at velocities of 10--15 km s^-1, while the CO gas in the remaining region in the atmosphere is moving in the opposite direction at the same velocities. The AMBER data are also consistent with the presence of warm molecular layers at ~1.4--1.5 Rstar with a CO column density of ~1 x 10^20 cm^-2. Our AMBER observations of Betelgeuse are the first spatially resolved study of the so-called macroturbulence in a stellar atmosphere other than the Sun. The spatially resolved CO gas motion is likely to be related to convective motion or intermittent mass ejections in clumps or arcs.

17 pages, 6 figures, accepted for publication in Astronomy and Astrophysics

References in corpus (12)

• Interferometric data reduction with AMBER/VLTI.Principle,estimators and illustration
• Red supergiants as potential Type IIn supernova progenitors: Spatially resolved 4.6 micron CO emission around VY CMa and Betelgeuse
• Variability in red supergiant stars: pulsations, long secondary periods and convection noise
• The dust condensation sequence in red super-giant stars
• Atmospheric dynamics and the mass loss process in red supergiant stars
• Tracing the young massive high-eccentricity binary system Theta 1 Orionis C through periastron passage
• The 3D Morphology of VY Canis Majoris. I The Kinematics of the Ejecta
• Tests of stellar model atmospheres by optical interferometry: VLTI/VINCI limb-darkening measurements of the M4 giant psi phe
• A critical test of empirical mass loss formulae applied to individual giants and supergiants
• The molecular and dusty composition of Betelgeuse's inner circumstellar environment
• Infrared Spectra and Visibilities as Probes of the Outer Atmospheres of Red Supergiant Stars
• Water vapor on supergiants. The 12 micron TEXES spectra of mu Cephei

Cited by in corpus (49)

• Granulation in Red Giants: observations by the Kepler mission and 3D convection simulations
• The temperatures of Red Supergiants
• Imaging the spotty surface of Betelgeuse in the H band
• Imaging the dynamical atmosphere of the red supergiant Betelgeuse in the CO first overtone lines with VLTI/AMBER
• Radiative hydrodynamics simulations of red supergiant stars: II. simulations of convection on Betelgeuse match interferometric observations
• Radiative hydrodynamics simulations of red supergiant stars. IV gray versus non-gray opacities
• The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed by Herschel. I. Evidence of clumps, multiple arcs, and a linear bar-like structure
• The close circumstellar environment of Betelgeuse - Adaptive optics spectro-imaging in the near-IR with VLT/NACO
• The close circumstellar environment of Betelgeuse - V. Rotation velocity and molecular envelope properties from ALMA
• High spectral resolution imaging of the dynamical atmosphere of the red supergiant Antares in the CO first overtone lines with VLTI/AMBER
• Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER
• Evolutionary tracks for Betelgeuse
• The close circumstellar environment of Betelgeuse - II. Diffraction-limited spectro-imaging from 7.76 to 19.50 microns with VLT/VISIR
• An observational study of dust nucleation in Mira ($o$ Ceti): I. Variable features of AlO and other Al-bearing species
• KamLAND Sensitivity to Neutrinos from Pre-Supernova Stars
• The close circumstellar environment of Betelgeuse. IV. VLTI/PIONIER interferometric monitoring of the photosphere
• The atmospheric structure and fundamental parameters of the red supergiants AH Sco, UY Sct and KW Sgr
• An Updated 2017 Astrometric Solution for Betelgeuse
• 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
• Properties of the CO and H${}_2$O MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observations
• CHARA/MIRC observations of two M supergiants in Perseus OB1: temperature, Bayesian modeling, and compressed sensing imaging
• Is Betelgeuse Really Rotating? Synthetic ALMA Observations of Large-scale Convection in 3D Simulations of Red Supergiants
• Imaging the heart of astrophysical objects with optical long-baseline interferometry
• Exploring the innermost dust formation region of the oxygen-rich AGB star IK~Tau with VLT/SPHERE-ZIMPOL and VLTI/AMBER
• Spatially resolved, high-spectral resolution observation of the K giant Aldebaran in the CO first overtone lines with VLTI/AMBER
• Spatially resolving the outer atmosphere of the M giant BK Vir in the CO first overtone lines with VLTI/AMBER
• High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR
• Imaging the outward motions of clumpy dust clouds around the red supergiant Antares with VLT/VISIR
• Infrared interferometric three-dimensional diagnosis of the atmospheric dynamics of the AGB star R Dor with VLTI/AMBER
• The non-uniform, dynamic atmosphere of Betelgeuse observed at mid-infrared wavelengths
• On Granulation and Irregular Variation of Red Supergiants
• Interferometry of chemically peculiar stars: theoretical predictions vs. modern observing facilities
• Spatially resolving the thermally inhomogeneous outer atmosphere of the red giant Arcturus in the 2.3 micron CO lines
• AMBER-NACO aperture-synthesis imaging of the half-obscured central star and the edge-on disk of the red giant L2 Pup
• Circumstellar Light Echo as a Possible Origin of the Polarization of Type IIP Supernovae
• A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER
• Tomography of cool giant and supergiant star atmospheres III. Validation of the method on VLTI/AMBER observations of the Mira star S Ori
• Analysis of stellar spectra with 3D and NLTE models
• Spatially resolving the atmosphere of the non-Mira-type AGB star SW Vir in near-infrared molecular and atomic lines with VLTI/AMBER
• 3D-M3: High-spatial resolution spectroscopy with extreme AO and 3D printed micro-lenslets
• 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
• Betelgeuse and the red supergiants
• Betelgeuse's Buddy: X-Ray Constraints on the Nature of $\alpha$ Ori B
• Betelgeuse, the Prototypical Red Supergiant
• MOLsphere and pulsations of the Galactic Center's red supergiant GCIRS 7 from VLTI/GRAVITY
• From the atmosphere to the circumstellar environment in cool evolved stars
• Exploring the water and carbon monoxide shell around Betelgeuse with VLTI/AMBER
• Indicators of Mass in Spherical Stellar Atmospheres