Online material

Appendix A: Flux density calibrators

Several quasars were used for flux density calibration at the different epochs and bands. In Table A.1 we present the calibrators and their adopted flux densities and spectral indices from the ALMA calibrator catalog.

Appendix B: Relative astrometry

The binary pair Mira AB is fully resolved in the observations, with a representative image at the two frequencies presented

in Fig. 1 (left) and Fig. 2 (left). Using uv-fitting we determine the separation and position angle with milliarcsecond accuracy as indicated in Table B.1. The average separation of 0.472′′ corresponds to 43.4 AU at a distance of 92 pc. These values fit well with the predictions made by Prieur et al. (2002), although the authors note that their derived binary orbit is still poorly constrained. It is interesting to note that the data already show a (not yet significant) sign of a decrease in separation R over two weeks of observing at a rate of ~121 ± 71 μas day^-1. Futher epochs of observations with ALMA will thus be able to constrain the binary orbit to high precision.

© ESO, 2015