Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Resolving the stellar activity of the Mira AB binary with ALMA   We present the size, shape and flux densities at millimeter continuum
wavelengths, based on ALMA science verification observations in Band 3 (~94.6
GHz) and Band 6 (~228.7 GHz), from the binary Mira A (o Ceti) and Mira B. The
Mira AB system has been observed with ALMA at a spatial resolution of down to
~25 mas. The extended atmosphere of Mira A and the wind around Mira B sources
are resolved and we derive the size of Mira A and of the ionized region around
Mira B. The spectral indices within Band 3 (between 89-100 GHz) and between
Band 3 and Band 6 are also derived. The spectral index of Mira A is found to
change from 1.71+-0.05 within Band 3 to 1.54+-0.04 between Band 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 ~3.8x3.2 AU in Band 3 (with
brightness temperature Tb~5300 K) and ~4.0x3.6 AU in Band 6 (Tb~2500 K).
Additionally, a bright hotspot of ~0.4 AU and with Tb~10000 K is found on the
stellar disc of Mira A. The size of the ionized region around the accretion
disk of Mira B is found to be ~2.4 AU. The emission around Mira B is consistent
with that 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 due to shock heating. The hotspot is likely
due to magnetic activity and could be related to the previously observed X-ray
flare of Mira A.

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The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: cmp-lg