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                              <identifier>oai:research.chalmers.se:220363</identifier>
                              <datestamp>2018-09-07T12:43:42Z</datestamp>
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                          <metadata>
                              <oai_dc:dc xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
                                  <dc:title>Resolving the stellar activity of the Mira AB binary with ALMA</dc:title>
                                  <dc:identifier>https://research.chalmers.se/en/publication/220363</dc:identifier>
                                  <dc:date>2015</dc:date>
                                              <dc:creator>Vlemmings, Wouter</dc:creator>
                                              <dc:creator>Ramstedt, S.</dc:creator>
                                              <dc:creator>O Gorman, Eamon</dc:creator>
                                              <dc:creator>Humphreys, E. M.</dc:creator>
                                              <dc:creator>Wittkowski, M.</dc:creator>
                                              <dc:creator>Baudry, A.</dc:creator>
                                              <dc:creator>Karovska, M.</dc:creator>
                                                  <dc:subject>Astronomy, Astrophysics and Cosmology</dc:subject>
                                              <dc:subject>stars: AGB and post-AGB</dc:subject>
                                              <dc:subject>stars: atmospheres</dc:subject>
                                              <dc:subject>binaries: close</dc:subject>
                                              <dc:subject>stars: individual: Mira AB</dc:subject>
                                          <dc:description>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.</dc:description>
                                                                  <dc:relation>info:eu-repo/grantAgreement/EC/FP7/614264//Magnetic fields and the outflows during the formation and evolution of stars (OUTFLOWMAGN)/</dc:relation>
                                                  <dc:relation>info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201526186</dc:relation>
                                          <dc:type>info:eu-repo/semantics/article</dc:type>
                                          <dc:source>Astronomy and Astrophysics (0004-6361) vol.577(2015)</dc:source>
                                                      <dc:rights>info:eu-repo/semantics/openAccess</dc:rights>
  <dc:language>eng</dc:language>
                                  <dc:audience>Researchers</dc:audience>
                                  <dc:format>application/pdf</dc:format>
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