We report on VLA observations of HST-1 in M87 at 8 GHz from 2003–2007, during which a long major outburst occurs from radio to X-ray wave bands. At the VLA resolution, the flux density of HST-1 rises rapidly from 2003, peaks at the end of 2004, and then falls slowly in subsequent stages, which is similar to that in optical and X-ray wave bands. It appears that HST-1 moves with an apparent speed of 1.23𝑐 ± 0.91𝑐, and the fractional polarization keeps rising through the whole major outburst. The persistent increase in polarization level may mainly be attributed to the formation of a couple of new `subcomponents’ of relatively high degree of polarization within HST-1, and the weakening depolarization due to Faraday rotation and/or opacity through the whole major outburst.
Volume 40 | Issue 3
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