Title: Determining the Distance of Cyg X-3 with its X-ray Dust Scattering Halo Authors: Zhixing Ling, Shuang Nan Zhang, Shichao Tang (Version v2)

Using a cross-correlation method, we study the X-ray halo of Cyg X-3. Two components of dust distributions are needed to explain the time lags derived by the cross-correlation method. Assuming the distance as 1.7 kpc for Cygnus OB2 association (a richest OB association in the local Galaxy) and another uniform dust distribution, we get a distance of 7.2^{+0.3}_{-0.5} kpc (68% confidence level) for Cyg X-3. When using the distance estimation of Cygnus OB2 as 1.38 kpc or 1.82 kpc, the inferred distance for Cyg X-3 is 3.4^{+0.2}_{-0.2} kpc or 9.3^{+0.6}_{-0.4} kpc respectively. The distance estimation uncertainty of Cyg X-3 is mainly related to the distance of the Cygnus OB2, which may be improved in the future with high precision astrometric measurements. The advantage of this method is that the result depends weakly on the photon energy, dust grain radius, scattering cross-section and so on.

Title: Determining the Distance of Cyg X-3 with its X-ray Dust Scattering Halo Authors: Zhixing Ling, Shuang Nan Zhang, Shichao Tang

Using a cross-correlation method, we study the X-ray halo of Cyg X-3. Two components of dust distributions are needed to explain the time lags derived by the cross-correlation method. Assuming the distance as 1.7 kpc for Cygnus OB2 association (a richest OB association in the local Galaxy) and another uniform dust distribution, we get a distance of 7.2^{+0.3}_{-0.5} kpc (68% confidence level) for Cyg X-3. When using the distance estimation of Cygnus OB2 as 1.38 kpc or 1.82 kpc, the inferred distance for Cyg X-3 is 3.4^{+0.2}_{-0.2} kpc or 9.3^{+0.6}_{-0.4} kpc respectively. The distance estimation uncertainty of Cyg X-3 is mainly related to the distance of the Cygnus OB2, which may be improved in the future with high precision astrometric measurements. The advantage of this method is that the result depends weakly on the photon energy, dust grain radius, scattering cross-section and so on.

Title: The 2006 Radio Outburst of a Microquasar Cyg X-3: Observation and Data Authors: M. Tsuboi, T. Tosaki, N. Kuno, K. Nakanishi, T. Sawada, T. Umemoto, S. A. Trushkin, T. Kotani, N. Kawai, Y. Kurono, T. Handa, K. Kohno, T. Tsukagoshi, O. Kameya, H. Kobayashi, K. Fujisawa, A. Doi, T. Omodaka, H. Takaba, H. Sudou, K. Wakamatsu, Y. Koyama, E. Kawai, N. Mochizuki, Y. Murata

We present the results of the multi-frequency observations of radio outburst of the microquasar Cyg X-3 in February and March 2006 with the Nobeyama 45-m telescope, the Nobeyama Millimetre Array, and the Yamaguchi 32-m telescope. Since the prediction of a flare by RATAN-600, the source has been monitored from Jan 27 (UT) with these radio telescopes. At the eighteenth day after the quench of the activity, successive flares exceeding 1 Jy were observed successfully. The time scale of the variability in the active phase is presumably shorter in higher frequency bands. We also present the result of a follow-up VLBI observation at 8.4 GHz with the Japanese VLBI Network (JVN) 2.6 days after the first rise. The VLBI image exhibits a single core with a size of <8 mas (80 AU). The observed image was almost stable, although the core showed rapid variation in flux density. No jet structure was seen at a sensitivity of T_b = 7.5 x 10^5 K.