| 7th of April 2020 |
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| Evidence for Auroral Radio Emission from the magnetic star ρ Oph A |
| by Leto et al. |
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Stars like our Sun possess a magnetic field, and produce a solar wind
of high energy particles, but are not intrinsically bright sources at
radio wavelengths. However, certain classes of stars with strong
magnetic fields and plasma winds can produce significant radio
emission. The capability of the stellar magnetic fields to trap
out-flowing mass can produce periodic variability in radio and optical
spectral line emisson. Leto et al. describe ATCA measurements over
the frequency range 2.1–21.2 GHz of the magnetic star ρ Oph A. These
new ATCA observations, carried out over 3 epochs in March 2019,
enabled the rotational modulation of the stellar radio emission to be
determined, P = 0.75 days. Additionally, the detection of two highly
polarized pulses at 2.1 GHz indicates that the coherent stellar
Auroral Radio Emission is being produced.
The figure above shows the rotational variability of the ρ Oph A radio emission. The left panels show the total intensity (Stokes I) and the right panels show the circularly polarized intensity (Stokes V). The vertical orange bars (centred at a phase of 0.3) highlight the range of phases where Stokes V is clearly negative at frequencies above 5.5 GHz and the light-blue bars (centred at a phase of 0.75) refer to the phase range with Stokes V > 0. More details are given in the paper, published in Monthly Notices of the Royal Astronomical Society. |