Nature 374, 141 - 143 (09 March 2002); doi:10.1038/374141a0

Relativistic motion in a nearby bright X-ray source

S. J. Tingay^*†, D. L. Jauncey^‡, R. A. Preston^†, J. E. Reynolds^‡, D. L.  Meier^†, D. W. Murphy^†, A. K. Tzioumis^‡, D. J. McKay^‡, M. J. Kesteven^‡, J. E. J. Lovell^§, D. Campbell-Wilson^£, S. P. Elllngsen^§, R. Gough^‡, R. W. Hunstead^£, D. L. Jonos^†, P. M. McCulloch^§, V. Migenes^‡, J. Quick, M. W. Sinclair^‡ & D. Smits

^* Mount Stromlo and Siding Spring Observatories, Canberra, ACT 2611, Australia
^†Jet Propulsion Laboratory, Pasadena, California 91109, USA
^‡ Australia Telescope National Facility, Epping, NSW 2121, Australia
^§University of Tasmania, Hobart, Tasmania 7001, Australia
Hartebeesthoek Radio Astronomy Observatory, Hartebeestheok 1740, South Africa
^£University of Sydney, NSW 2006, Australia

THE recent discovery¹ of radio components apparently moving away from a Galactic source of transient X-ray emission faster than the speed of light (superluminal motion) has identified a low-energy Galactic counterpart to quasars. Here we report high-resolution radio observations of a second Galactic superluminal radio source GRO J1655-40, which was detected as an X-ray transient² on 27 July 1994. Our radio images reveal two components moving away from each other at an angular speed of 65 5 mas d^-1, corresponding to superluminal motion at the estimated distance of 3–5 kpc. The 12-day delay between the X-ray and radio outbursts suggests that the ejection of material at relativistic speeds occurs during a stable phase of accretion onto a black hole, which follows an unstable phase with a high accretion rate.

References

1.	Mirabel, I. F. & Rodriguez, L. F. Nature 371, 46−48 (1994). | Article | ISI |
2.	Zhang, S. N. et al. IAU Circ. No. 6046 (1994).
3.	Campbell-Wilson, D. & Hunstead, R. IAU Circ. No. 6052 (1994).
4.	Jauncey, D. L. et al. in Very High Angular Resolution Imaging (eds Robertson, J. & Tango, W.) 131−133 (Kluwer, Dordrecht, 1994).
5.	Preston, R. A. et al. in Sub-Arcsecond Radio Astronomy (eds Davis, R. J. & Booth, R. J.) 428−430 (Cambridge Univ. Press, 1993).
6.	Vermeulen, R. C., Schilizzi, R. T., Icke, V., Fejes, I. & Spencer, R. E. Nature 328, 309−313 (1987). | Article |
7.	Della Valle, M. IAU Circ. No. 6052 (1994).
8.	Crawford, I. A., Barlow, M. J. & Blades, J. C. Astrophys. J. 336, 212−230 (1989). | Article | ChemPort |
9.	Caswell, J. L., Murray, J. D., Roger, R. S., Cole, D. J. & Cooke, D. J. Astr. Astrophys. 45, 239−258 (1975). | ISI |
10.	Pearson, T. J. & Zensus, J. A. in Superluminal Radio Sources (eds Pearson, T. J. & Zensus, J. A.) 1−11 (Cambridge Univ. Press, 1987).
11.	Wilson, C. A. et al. IAU Circ. 6056 (1994).
12.	Blandford, R. D. & Payne, D. G. Mon. Not. R. astr. Soc. 199, 883−903 (1982). | ISI |
13.	Spencer, R. E., Swinney, R. W., Johnston, K. J. & Hjellming, R. M. Astrophys. J. 309, 694−699 (1986). | Article | ChemPort |