Fig. 2: The spatial PSD for three epochs of observations of R Doradus.
From: One month convection timescale on the surface of a giant evolved star
The spatial PSD, in units of mJy2, was determined directly from the interferometric visibilities after subtracting the best fit model for the stellar disk. The three panels represent the final three, highest angular resolution, epochs. Note the nonlinear scale of the x-axis. The filled circles denote the measurements and the curve represents a cubic spline fit to the observations. The largest blue stars, with corresponding 1σ s.d. error bars, are the PSD determined on-source; the smaller orange dots represent the off-source measurements. In the last two epochs, the second bin at about 12 mas contains only limited visibilities and hence does not present a significant detection. As the peak at the smallest angular size dominates, this indicates that the smallest granule structure dominates. From an error-weighted average of the three epochs, we find a value of x = 13.1 ± 0.6 mas. For a distance of 55 ± 3 pc (ref. 16), this corresponds to x = 0.72 ± 0.05 au, compared to a stellar diameter at 338 GHz of 3.28 au.
