Year: 2001
Type: article
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 65d (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 PJLX≫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.
Authors: R. P. Fender, R. M. Hjellming, R. P. J. Tilanus, G. G. Pooley, J. R. Deane, R. N. Ogley, R. E. Spencer
Institutions: University of Amsterdam, National Radio Astronomy Observatory, University of Cambridge, University of Hawaiʻi at Mānoa, University of Hawaii System, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, CEA Paris-Saclay - Etablissement de Saclay, CEA Paris-Saclay, University of Manchester
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2123430010