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arXiv · 1610.02989

Modelling the environment around five ultracool dwarfs via the radio domain

Y. T. Metodieva·A. A. Kuznetsov·A. E. Antonova·J. G. Doyle·G. Ramsay·K. Wu
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Abstract

We present the results of a series of short radio observations of six ultracool dwarfs made using the upgraded VLA in S (2--4GHz) and C (4--7GHz) bands. LSR J1835+3259 exhibits a 100 percent right-hand circularly polarised burst which shows intense narrowband features with a fast negative frequency drift of about $-30$ MHz $\textrm{s}^{-1}$. They are superimposed on a fainter broadband emission feature with a total duration of about 20 minutes, bandwidth of about 1 GHz, centred at about 3.5 GHz, and a slow positive frequency drift of about 1 MHz $\textrm{s}^{-1}$. This makes it the first such event detected below 4 GHz and the first one exhibiting both positive and negative frequency drifts. Polarised radio emission is also seen in 2MASS J00361617+1821104 and NLTT 33370, while LP 349-25 and TVLM 513-46546 have unpolarised 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 which agree well with the observations.

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Y. T. Metodieva, A. A. Kuznetsov, A. E. Antonova, J. G. Doyle, G. Ramsay, K. Wu. 2016-10-10. Modelling the environment around five ultracool dwarfs via the radio domain. https://doi.org/10.1093/mnras%2Fstw2597

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