Multifrequency VLA observations of radio continuum from IRAS 16293-2422

Abstract

Using the VLA at 20, 6, 2, and 1.3 cm, we observed the cold infrared source IRAS 16293-2422. Our data allow a determination of the spectral indices of the components A and B. IRAS 16293-2422A, which is known from higher angular resolution data to consist of at least two subcomponents, has a spectral index alpha = 0.6 +/- 0.1, consistent with the subcomponent sources being partially optically thick H II regions or ionized outflows. On the other hand, IRAS 16293-2422B has a very steep spectral index, alpha = 2.1 +/- 0.2 between 6 and 2 cm and alpha = 3.2 +/- 0.5 between 2 and 1.3 cm. The spectral index from the 6 and 2 cm data is consistent with an optically thick H II region, and the unusually large spectral index between 2 and 1.3 cm suggests that the 1.3 cm flux may have a contribution from dust emission. We have also monitored the region at 2 cm in five different occasions over a period of 14 months. We did not detect evidence of variability within the observational uncertainty.