2004/05/16 by G. B. Taylor, D. A. Frail, E. Berger +1 · 3 citations
Physics and Astronomy · #Astro and Planetary Science #Gamma-ray bursts and supernovae #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/422554
published as Astrophys.J. 609 (2004) L1-L4 · 12 pages including 2 figures, LaTeX. Accepted to ApJ Letters on May 14, 2004
arxiv created 2004/05/16 · openalex publication_date 2004/05/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The bright, nearby ( z = 0.1685) gamma-ray burst (GRB) of 2003 March 29 has presented us with the first opportunity to directly image the expansion of a GRB. This burst reached flux density levels at centimeter wavelengths more than 50 times brighter than any previously studied event. Here we present the results of a VLBI campaign using the Very Long Baseline Array, Very Large Array, Green Bank, Effelsberg, Arecibo, and Westerbork telescopes that resolves the radio afterglow of GRB 030329 and constrains its rate of expansion. The size of the afterglow is found to be ~0.07 mas (0.2 pc) 25 days after the burst and 0.17 mas (0.5 pc) 83 days after the burst, indicating an average velocity of 3 c -5 c . This expansion is consistent with expectations of the standard fireball model. We measure the projected proper motion of GRB 030329 in the sky to less than 0.3 mas in the 80 days following the burst. In observations taken 52 days after the burst, we detect an additional compact component at a distance from the main component of 0.28 ± 0.05 mas (0.80 pc). The presence of this component is not expected from the standard model.