Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: VLBI Observation of Microquasar Cyg X-3 during an X-ray State Transition
  from Soft to Hard in the 2007 May-June Flare   We present a radio observation of microquasar Cyg X-3 during an X-ray state
transition from ultrasoft to hard state in the 2007 May$-$June flare using the
VLBI Exploration of Radio Astrometry (VERA) at 22 GHz. During the transition, a
short-lived mini-flare of ${\lesssim}3$ hr was detected prior to the major
flare. In such a transition, a jet ejection is believed to occur, but there
have been no direct observations to support it. An analysis of Gaussian fits to
the observed visibility amplitudes shows a time variation of the source axis,
or a structural change, during the mini-flare. Our model fits, together with
other multiwavelength observations in the radio, soft, and hard X-rays, and the
shock-in-jet models for other flaring activities at GHz wavebands, suggest a
high possibility of synchrotron flares during the mini-flare, indicative of a
predominant contribution from jet activity. Therefore, the mini-flare with an
associated structural change is indicative of a jet ejection event in the state
transition from ultrasoft to hard state.

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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
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The categories of this paper are: math
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: physics
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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: alg-geom