Physical parameters of a relativistic jet at very high redshift: the case of the blazar J1430+4204

¹ Dept. of Physics of Complex Systems, Eötvös University, Pázmány P. s. 1/A, 1117 Budapest, Hungary e-mail: veresp@elte.hu
² Dept. of Physics, Bolyai Military University, PO Box 15, Budapest, 1581, Hungary
³ FÖMI Satellite Geodetic Observatory, PO Box 585, 1592 Budapest, Hungary
⁴ MTA Research Group for Physical Geodesy and Geodynamics, PO Box 91, 1521 Budapest, Hungary
⁵ Joint Institute for VLBI in Europe, PO Box 2, 7990 AA Dwingeloo, The Netherlands

Received: 8 May 2010
Accepted: 23 June 2010

Abstract

Context. The high-redshift (z = 4.72) blazar J1430+4204 produced a major radio outburst in 2005. Such outbursts are usually associated with the emergence of a new component in the inner radio jet.

Aims. We searched for possible changes in the radio structure on milli-arcsecond angular scales, to determine physical parameters that characterise the relativistic jet ejected from the centre of this source.

Methods. We analysed 15-GHz radio interferometric images obtained with the Very Long Baseline Array (VLBA) before and after the peak of the outburst.

Results. We did not identify any significant new jet component over a period of 569 days. We estimated the Doppler factor, the Lorentz factor, and the apparent transverse speed of a putative jet component using three different methods. The likely small jet angle to the line of sight and our values of the apparent transverse speed are consistent with not detecting a new jet feature.