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Resolving the stell...
Resolving the stellar activity of the Mira AB binary with ALMA
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- Vlemmings, Wouter, 1974 (författare)
- Chalmers, Onsala Space Observ, Dept Earth & Space Sci, S-43992 Onsala, Sweden.,Chalmers tekniska högskola,Chalmers University of Technology
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- Ramstedt, Sofia (författare)
- Uppsala universitet,Teoretisk astrofysik,Uppsala University
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- O Gorman, Eamon, 1984 (författare)
- Chalmers, Onsala Space Observ, Dept Earth & Space Sci, S-43992 Onsala, Sweden.,Chalmers tekniska högskola,Chalmers University of Technology
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- Humphreys, E. M. L. (författare)
- ESO, D-85748 Garching, Germany.,European Southern Observatory (ESO)
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- Wittkowski, M. (författare)
- ESO, D-85748 Garching, Germany.,European Southern Observatory (ESO)
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- Baudry, A. (författare)
- Univ Bordeaux 1, LAB, UMR 5804, F-33270 Floirac, France.;CNRS, LAB, UMR 5804, F-33270 Floirac, France.,Laboratoire d'Astrophysique de Bordeaux,Centre national de la recherche scientifique (CNRS)
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- Karovska, M. (författare)
- Smithsonian Astrophys Observ, Cambridge, MA 02138 USA.,Smithsonian Astrophysical Observatory
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Chalmers, Onsala Space Observ, Dept Earth & Space Sci, S-43992 Onsala, Sweden Chalmers tekniska högskola (creator_code:org_t)
- 2015-05-13
- 2015
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 577
- Relaterad länk:
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https://doi.org/10.1...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Aims. We present the size, shape, and flux densities at millimeter continuum wavelengths, based on ALMA science verification observations in Band 3 (similar to 94.6 GHz) and Band 6 (similar to 228.7 GHz), from the binary Mira A (o Ceti) and Mira B. Methods. The Mira AB system was observed with ALMA at a spatial resolution down to similar to 25 mas. The extended atmosphere of Mira A and the wind around Mira B sources were resolved, and we derived the sizes of Mira A and of the ionized region around Mira B. The spectral indices within Band 3 (between 89-100 GHz) and between Bands 3 and 6 were also derived. Results. The spectral index of Mira A is found to change from 1.71 +/- 0.05 within Band 3 to 1.54 +/- 0.04 between Bands 3 and 6. The spectral index of Mira B is 1.3 +/- 0.2 in Band 3, in good agreement with measurements at longer wavelengths; however, it rises to 1.72 +/- 0.11 between the bands. For the first time, the extended atmosphere of a star is resolved at these frequencies, and for Mira A the diameter is similar to 3.8 x 3.2 AU in Band 3 (with brightness temperature T-b similar to 5300 K) and similar to 4.0 x 3.6 AU in Band 6 (T-b similar to 2500 K). Additionally, a bright hotspot similar to 0.4 AU, with T-b similar to 10 000 K, is found on the stellar disk of Mira A. The size of the ionized region around the accretion disk of Mira B is found to be similar to 2.4 AU. Conclusions. The emission around Mira B is consistent with emission from a partially ionized wind of gravitationally bound material from Mira A close to the accretion disk of Mira B. The Mira A atmosphere does not fully match predictions with brightness temperatures in Band 3 significantly higher than expected, potentially owing to shock heating. The hotspot is very likely due to magnetic activity and could be related to the previously observed X-ray flare of Mira A.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- stars: AGB and post-AGB
- stars: atmospheres
- binaries: close
- stars: individual: Mira AB
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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