Closure Amplitude Analysis of 7mm VLBA Observations of Sagittarius A*

Geoffrey C. Bower1

1 UC Berkeley

E-mail contact: gbower@astro.berkeley.edu

High frequency very long baseline interferometry is necessary to avoid the effects of strong interstellar scattering when imaging Sagittarius A*. Unfortunately, the reliability of imaging declines with increasing frequency due to amplitude calibration errors for this low declination source. Closure amplitude analysis provides an unbiased method for estimating source parameters. We summarize the results of this analysis for old and new 7mm VLBA experiments.