C. R. Gwinn, M. D. Johnson, J. E. Reynolds, D. L. Jauncey, A. K. Tzioumis, S. Dougherty, B. Carlson, D. Del Rizzo, H. Hirabayashi, H. Kobayashi, Y. Murata, P. G. Edwards, J. F. H. Quick, C. S. Flanagan, P. M. McCulloch
We compare the noise in interferometric measurements of the Vela pulsar from ground- and space-based antennas with theoretical predictions. In particular, the noise scales with both the flux density and the interferometric phase of the source. Because the Vela pulsar is bright and scintillating, these comparisons extend into both the low and high signal-to-noise regimes. Furthermore, our diversity of baselines explores the full range of variation in interferometric phase. We find excellent agreement between our estimates of noise between spectral samples within the characteristic scintillation scales and theoretical expectations. Namely, the noise is drawn from an elliptical Gaussian distribution in the complex plane, centered on the signal. The major axis, aligned with the signal phase, varies quadratically with the signal, while the minor axis, at quadrature, varies linearly with the same coefficients. Thus, for weak signal, the noise is a circular Gaussian distribution. Both the variance and covariance of the noise are also affected by artifacts from the digitization and correlation. In particular, we show that gating introduces correlations between nearby spectral channels.
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http://arxiv.org/abs/1208.0039
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