Multifrequency Very Long Baseline Array Observations of the Compact Double B2 2050+36: Constraints on Interstellar Scattering Revisited
NAVAL RESEARCH LAB WASHINGTON DC REMOTE SENSING DIV
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We present multifrequency observations with the Very Long Baseline Array of the compact double radio source B2 205036. Our observations are at 0.33, 0.61, 1.67, 2.3, and 8.4 GHz, with the 0.61 GHz observations forming the third epoch of observation of this source at that frequency. At 0.61 GHz, the structure of B2 205036 is dominated by two components 56 mas apart. Within the uncertainties of the various measurements, this separation has remained unchanged for the past 16 yr. Any differential image wander caused by refractive interstellar scattering is less than 4 mas. Both the lack of differential image wander and the frequency dependence of the angular diameter of B2 205036 below 1 GHz indicate that the electron density power spectrum along this line of sight has a spectral index near the Kolmogorov value, with a value of 4 being highly unlikely. We conclude that diffractive scattering dominates along this line of sight results in the literature indicate that this conclusion also holds true for the line of sight to the pulsar PSR B202028. Comparison of our 1.67 GHz observations with those obtained 21 yr previously place a limit on the projected linear separation velocity of the two components of c.