VLBI Observation of Microquasar Cyg X-3 during an X-Ray State Transition from Soft to Hard in the 2007 May-June Flare
Abstract
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 at 22 GHz. During the transition, a short-lived mini-flare of <~ 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2013
- DOI:
- 10.1088/0004-637X/772/1/41
- arXiv:
- arXiv:1307.1226
- Bibcode:
- 2013ApJ...772...41K
- Keywords:
-
- binaries: close;
- ISM: jets and outflows;
- radiation mechanisms: non-thermal;
- radio continuum: stars;
- stars: individual: Cygnus X-3;
- techniques: interferometric;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 12 pages, 3 figures, accepted for publication in ApJ