Circularly polarized 3.5 cm continuum emission was detected toward three radio sources in the R CrA region using the Very Large Array .
The Class I protostar IRS 5b persistently showed polarized radio emission with a constant helicity over 8 yr , which suggests that its magnetosphere has a stable configuration .
There is a good correlation between the Stokes I and Stokes V fluxes , and the fractional polarization is about 0.17 .
During active phases the fractional polarization is a weakly decreasing function of Stokes I flux , which suggests that IRS 5b is phenomenologically similar to other types of flare stars such as RS CVn binaries .
The variability timescale of the polarized flux is about a month , and the magnetosphere of IRS 5b must be very large in size .
The Class I protostar IRS 7A was detected once in circularly polarized radio emission , even though IRS 7A drives a thermal radio jet .
This detection implies that the radio emission from the magnetosphere of a young protostar can escape the absorption by the partially ionized wind at least once in a while .
The properties of IRS 7A and IRS 5b suggests that Class I protostars have organized peristellar magnetic fields of a few kilogauss and that the detectability of magnetospheric emission may depend on the evolutionary status of protostar .
Also reported is the detection of circularly polarized radio emission toward the variable radio source B5 .