J06587−5558: a very unusual polarized radio source |
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| Authors: | H Liang RD Ekers RW Hunstead EE Falco P Shaver |
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| Institution: | Astronomical Institute 'Anton Pannekoek', University of Amsterdam, and Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, the Netherlands;National Radio Astronomy Observatory, Socorro, NM 87801, USA;Joint Astronomy Centre, 660 N. A'ohoku Pl., Hilo, Hawaii, USA;Mullard Radio Astronomy Observatory, Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE;Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA;Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette Cedex, France;University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, Cheshire SK11 9DL |
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| Abstract: | We present observations of the X-ray transient XTE J1118+480 during its low/hard X-ray state outburst in 2000, at radio and submillimetre wavelengths with the VLA, Ryle Telescope, MERLIN and JCMT. The high-resolution MERLIN observations reveal all the radio emission (at 5 GHz) to come from a compact core with physical dimensions smaller than 65 d (kpc) au. The combined radio data reveal a persistent and inverted radio spectrum, with spectral index ∼ +0.5. The source is also detected at 350 GHz, on an extrapolation of the radio spectrum. Flat or inverted radio spectra are now known to be typical of the low/hard X-ray state, and are believed to arise in synchrotron emission from a partially self-absorbed jet. Comparison of the radio and submillimetre data with reported near-infrared observations suggest that the synchrotron emission from the jet extends to the near-infrared, or possibly even optical regimes. In this case the ratio of jet power to total X-ray luminosity is likely to be P J L X≫0.01, depending on the radiative efficiency and relativistic Doppler factor of the jet. Based on these arguments we conclude that during the period of our observations XTE J1118+480 was producing a powerful outflow which extracted a large fraction of the total accretion power. |
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| Keywords: | binaries: close stars: individual: XTE J1118+480 ISM: jets and outflows radio continuum: stars |
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