Vol 7, No 5

Seven-frequency VLBI Observations of the GHz-Peaked-Spectrum Source OQ 208

Wen-Feng Luo, Jun Yang, Lang Cui, Xiang Liu, Zhi-Qiang Shen


Abstract We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4, 1.7, 2.3, 5.0, 8.4, 15.4 GHz and the European VLBI Network at 6.7 GHz. The low frequency (1.4, 1.7 and 2.3 GHz) observations reveal a weak and extended steep-spectrum component at about 30 mas away at position angle −110°, which may be a remnant emission. The radio structure of OQ 208 consists of two mini-lobes at 5.0, 6.7, 8.4 and 15.4 GHz. Our spectral analysis further confirms that the southwest lobe undergoes free-free absorption and finds that the free-free absorption is stronger in the inner region. By fitting the 8.4 GHz images from 1994 to 2005, we obtain a separation speed of 0.031±0.006 mas yr−1 between the two mini-lobes. This indicates a jet proper motion of 0.105±0.020 c and a kinematic age of 219±42 yr for the radio source.



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