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We analyze the radio emission from the β Cep star V2187 Cyg using archive data from the Jansky Very Large Array. The observations were made in ten epochs at 1.39 and 4.96 GHz in the highest angular resolution A configuration. We determine a spectral index of of α = 0.6 ± 0.2 ( S _ν ∝ ν ^α ), consistent with an ionized wind or a partially optically thick synchrotron or gyrosynchrotron source. The emission is spatially unresolved at both frequencies. The 4.96 GHz data show a radio pulse with a duration of about one month that can be modeled in terms of an internal shock in the stellar wind produced by a sudden increase in the mass-loss rate and the terminal velocity. The quiescent radio emission of V2187 Cyg at 4.96 GHz (with a flux density of ≃150 μ Jy) cannot be explained in terms of an internally (by V2187 Cyg) or externally (by a nearby O star) photoionized wind. We conclude that, despite the spectral index suggestive of free–free emission from an ionized wind, the radio emission of V2187 Cyg most likely has a magnetic origin, a possibility that can be tested with a sensitive search for circular polarization in the radio, as expected from gyrosynchrotron radiation and also by trying to measure the stellar magnetic field, which is expected to be in the range of several kilogauss.

We observed with the Jansky Very Large Array at 3.6 and 1.3 cm a sample of 11 proto-brown dwarf (BD) candidates in Taurus in a search for thermal radio jets driven by the most embedded BDs. We detected for the first time four thermal radio jets in proto-BD candidates. We compiled data from UKIDSS, 2MASS, Spitzer, WISE, and Herschel to build the spectral energy distribution (SED) of the objects in our sample, which are similar to typical Class I SEDs of young stellar objects (YSOs). The four proto-BD candidates driving thermal radio jets also roughly follow the well-known trend of centimeter luminosity against bolometric luminosity determined for YSOs, assuming they belong to Taurus, although they present some excess of radio emission compared to the known relation for YSOs. Nonetheless, we are able to reproduce the flux densities of the radio jets modeling the centimeter emission of the thermal radio jets using the same type of models applied to YSOs, but with corresponding smaller stellar wind velocities and mass-loss rates, and exploring different possible geometries of the wind or outflow from the star. Moreover, we also find that the modeled mass outflow rates for the bolometric luminosities of our objects agree reasonably well with the trends found between the mass outflow rates and bolometric luminosities of YSOs, which indicates that, despite the “excess” centimeter emission, the intrinsic properties of proto-BDs are consistent with a continuation of those of very low-mass stars to a lower mass range. Overall, our study favors the formation of BDs as a scaled-down version of low-mass stars. [ABSTRACT FROM AUTHOR]