Research Note

A compact radio source in the high-redshift soft gamma-ray blazar IGR J12319–0749

¹ FÖMI Satellite Geodetic Observatory, PO Box 585, 1592 Budapest, Hungary
e-mail: frey@sgo.fomi.hu
² Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands
e-mail: zparagi@jive.nl
³ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary
e-mail: gabanyi@konkoly.hu
⁴ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, 200030 Shanghai, PR China
e-mail: antao@shao.ac.cn
⁵ Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 210008 Nanjing, PR China

Received: 22 November 2012
Accepted: 7 March 2013

Abstract

Context. Blazars are powerful active galactic nuclei (AGNs) radiating prominently in the whole electromagnetic spectrum, from the radio to the X-ray and gamma-ray bands. Their emission is dominated by synchrotron and inverse-Compton radiation from a relativistic jet originating from an accreting central supermassive black hole. The object IGR J12319−0749 has recently been identified as a soft gamma-ray source with the IBIS instrument of the INTEGRAL satellite, coincident with a quasar at high redshift (z = 3.12).

Aims. We studied the radio structure of IGR J12319−0749 to strengthen its blazar identification by detecting a compact radio jet on the milli-arcsecond (mas) angular scale, and to measure its astrometric position accurate to mas level.

Methods. We used the technique of electronic very long baseline interferometry (e-VLBI) to image IGR J12319−0749 with the European VLBI Network (EVN) at 5 GHz on 2012 June 19.

Results. IGR J12319−0749 (J1231−0747) is a compact radio source, practically unresolved on interferometric baselines up to ~136 million wavelengths. The estimated brightness temperature (at least 2 × 10¹¹ K) indicates that the radio emission of its jet is Doppler-boosted. The accurate position of the compact radio source is consistent with the positions measured at higher energies.