Astron. Astrophys. Suppl. Ser. 138, 445-446

VLBI observations of GRB afterglows

G.B. Taylor¹ - A.J. Beasley¹ - D.A. Frail¹ - S.R. Kulkarni² - J.E. Reynolds³

Send offprint request: G.B. Taylor

1 - National Radio Astronomy Observatory (NRAO), Socorro, NM 87801, U.S.A.
e-mail: gtaylor@nrao.edu

2 - Division of Physics, Mathematics, and Astronomy 105-24, California Institute of Technology, Pasadena, CA 91125, U.S.A.
3 - Australia Telescope National Facility, CSIRO, Epping 2121, Australia

Received December 29, 1998; accepted March 30, 1999

Abstract:

Once the afterglow from a GRB has been detected in the radio, Very Long Baseline Interferometry (VLBI) observations can provide a resolution of 1 milliarcsecond or better and absolute astrometry at a similar level. We will review the VLBI programs carried out to date which include observations of G970508, G980329, G980425, and G980703. All of these objects are found to be very compact (size < 1 mas) even months after the burst. This is consistent with the predictions of fireball models. Our ultimate goal is a direct measurement of the morphology and expansion of a GRB afterglow.

Key words: gamma-ray bursts -- technique: interferometry astrometry