2001/07/05 by M. Massi, M. Ribó, M. Ribo +3 · 6 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1051/0004-6361:20010953
published as Astron.Astrophys. 376 (2001) 217-223 · 7 pages, 4 figures, LaTeX, uses aa.cls. Accepted for publication in A&A
arxiv created 2001/07/05 · openalex publication_date 2001/09/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We present Very Long Baseline Interferometry (VLBI) observations of the high mass X-ray binary LS I +61°303, carried out with the European VLBI Network (EVN). Over the 11 hour observing run, performed ~10 days after a radio outburst, the radio source showed a constant flux density, which allowed sensitive imaging of the emission distribution. The structure in the map shows a clear extension to the southeast. Comparing our data with previous VLBI observations we interpret the extension as a collimated radio jet as found in several other X-ray binaries. Assuming that the structure is the result of an expansion that started at the onset of the outburst, we derive an apparent expansion velocity of 0.003 c, which, in the context of Doppler boosting, corresponds to an intrinsic velocity of at least 0.4 c for an ejection close to the line of sight. From the apparent velocity in all available epochs we are able to establish variations in the ejection angle which imply a precessing accretion disk. Finally we point out that LS I +61°303, like SS 433 and Cygnus X-1, shows evidence for an emission region almost orthogonal to the relativistic jet.