Multiwavelength corss-correlation and radio Doppler factor estimation of CGRaBS J2345-1555

Abstract

In this paper, CGRaBS J2345-1555’s long-term radio band, gamma ray flux and optical V-band magnitude data are collected from Fermi/LAT, Catalina, and OVRO dataset. The correlation between multi-bands is evaluated by the discrete correlation function method. The results show that the correlation coefficient between gamma band and radio band is 0.53, and the time delay is about 90 days, a variation of the gamma band is about 90 days ahead of radio band; the correlation coefficient between radio band and optical V-band is 0.84, and the time delay is about –300 days, a variation of the optical V-band is about 300 days ahead of radio band; there is no significant correlation between gamma and optical V-band. These results show that the optical band is dominated by synchrotron radiation, and the time delay between the radio band and the optical band can be explained as the fact that the radiation region of the optical band is upstream, and the radio band is downstream. The gamma band and the radio band are both homologous. The distribution of brightness temperature is used to calculate the Doppler factor of the celestial body’s radio band. The averaged Doppler factor is 12.64, and it oscillates with the light curve. So the jet has obvious bunching effect, and the variation of radiation flux in radio band comes from the jet.