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Magnetically aligne...
Magnetically aligned dust and SiO maser polarisation in the envelope of the red supergiant VY Canis Majoris
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- Vlemmings, Wouter, 1974 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Khouri, Theo, 1985 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Marti-Vidal, Ivan, 1980 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Tafoya Martinez, Daniel, 1981 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Baudry, A. (författare)
- Laboratoire d'Astrophysique de Bordeaux
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- Etoka, S. (författare)
- Universität Hamburg,University of Hamburg
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- Humphreys, E. M. (författare)
- European Southern Observatory (ESO)
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- Jones, T. J. (författare)
- University of Minnesota
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- Kemball, A. (författare)
- University of Illinois
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O Gorman, Eamon, 1984 (författare)
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- Perez-Sanchez, A. F. (författare)
- European Southern Observatory Santiago
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- Richards, A. M. S. (författare)
- University of Manchester
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(creator_code:org_t)
- 2017-07-11
- 2017
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 603, s. A92-
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Abstract
Ämnesord
Stäng
- Aims. Polarisation observations of circumstellar dust and molecular (thermal and maser) lines provide unique information about dust properties and magnetic fields in circumstellar envelopes of evolved stars. Methods. We use Atacama Large Millimeter/submillimeter Array (ALMA) Band 5 science verification observations of the red supergiant VY CMa to study the polarisation of SiO thermal /maser lines and dust continuum at similar to 1.7 mm wavelength. We analyse both linear and circular polarisation and derive the magnetic field strength and structure, assuming the polarisation of the lines originates from the Zeeman effect, and that of the dust originates from aligned dust grains. We also discuss other effects that could give rise to the observed polarisation. Results. We detect, for the first time, significant polarisation (similar to 3%) of the circumstellar dust emission at millimeter wavelengths. The polarisation is uniform with an electric vector position angle of similar to 8 degrees. Varying levels of linear polarisation are detected for the J = 4-3 (SiO)-Si-28 nu = 0; 1; 2; and (SiO)-Si-29 nu = 0; 1 lines, with the strongest polarisation fraction of similar to 30% found for the (SiO)-Si-29 nu = 1 maser. The linear polarisation vectors rotate with velocity, consistent with earlier observations. We also find significant (up to similar to 1%) circular polarisation in several lines, consistent with previous measurements. We conclude that the detection is robust against calibration and regular instrumental errors, although we cannot yet fully rule out non-standard instrumental effects. Conclusions. Emission from magnetically aligned grains is the most likely origin of the observed continuum polarisation. This implies that the dust is embedded in a magnetic field >13 mG. The maser line polarisation traces the magnetic field structure. The magnetic field in the gas and dust is consistent with an approximately toroidal field configuration, but only higher angular resolution observations will be able to reveal more detailed field structure. If the circular polarisation is due to Zeeman splitting, it indicates a magnetic field strength of similar to 1-3 Gauss, consistent with previous maser observations.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- Late-Type Stars
- Field Direction
- stars: individual: VY CMa
- polarization
- Evolved Stars
- Radiofrequency Lines
- supergiants
- Circumstellar Envelopes
- 3-Dimensional Morphology
- Molecular Clouds
- Circular-Polarization
- stars: mass-loss
- stars: magnetic field
- Grain Alignment
- masers
- Radiative Torques
Publikations- och innehållstyp
- art (ämneskategori)
- ref (ämneskategori)
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Vlemmings, Woute ...
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Khouri, Theo, 19 ...
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Marti-Vidal, Iva ...
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Tafoya Martinez, ...
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Baudry, A.
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Etoka, S.
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visa fler...
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Humphreys, E. M.
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Jones, T. J.
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Kemball, A.
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O Gorman, Eamon, ...
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Perez-Sanchez, A ...
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Richards, A. M. ...
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visa färre...
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