2009/04/25 by E. Fomalont, S. Kopeikin, G. Lanyi +1 · 3 citations
Physics and Astronomy · #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/699/2/1395
published as Astrophys.J.699:1395-1402,2009 · 22 pages, 3 figures
arxiv created 2009/04/25 · arxiv updated 2009/12/01
We have used the Very Long Baseline Array (VLBA) at 43, 23 and 15 GHz to measure the solar gravitational deflection of radio waves among four radio sources during an 18-day period in October 2005. Using phase-referenced radio interferometry to fit the measured phase delay to the propagation equation of the parameterized post-Newtonian (PPN) formalism, we have determined the deflection parameter gamma = 0.9998 +/- 0.0003 (68% confidence level), in agreement with General Relativity. The results come mainly from 43 GHz observations where the refraction effects of the solar corona were negligible beyond 3 degrees from the sun. The purpose of this experiment is three-fold: to improve on the previous results in the gravitational bending experiments near the solar limb; to examine and evaluate the accuracy limits of terrestrial VLBI techniques; and to determine the prospects and outcomes of future experiments. Our conclusion is that a series of improved designed experiments with the VLBA could increase the presented accuracy by at least a factor of 4.