Mon. Not. R. Astron. Soc., 465, 1995-2009 (2017/February-3)
Modelling the environment around five ultracool dwarfs via the radio domain.
METODIEVA Y.T., KUZNETSOV A.A., ANTONOVA A.E., DOYLE J.G., RAMSAY G. and WU K.
Abstract (from CDS):
We present the results of a series of short radio observations of six ultracool dwarfs made using the upgraded Very Large Array in S (2-4GHz) and C (4-7GHz) bands. LSR J1835+3259 exhibits a 100 per cent right-hand circularly polarized burst that shows intense narrow-band features with a fast negative frequency drift of about -30 MHz s–1. They are superimposed on a fainter broad-band emission feature with a total duration of about 20 min, bandwidth of about 1 GHz, centred at about 3.5 GHz, and a slow positive frequency drift of about 1 MHz s–1. This makes it the first such event detected below 4 GHz and the first one exhibiting both positive and negative frequency drifts. Polarized radio emission is also seen in 2MASS J00361617+1821104 and NLTT 33370, while LP 349-25 and TVLM 513-46546 have unpolarized emission and BRI B0021-0214 was not detected. We can reproduce the main characteristics of the burst from LSR J1835+3259 using a model describing the magnetic field of the dwarf as a tilted dipole. We also analyse the origins of the quiescent radio emission and estimate the required parameters of the magnetic field and energetic electrons. Although our results are non-unique, we find a set of models that agree well with the observations.