Low-frequency monitoring of flare star binary CR Draconis: long-term electron-cyclotron maser emission

Recently detected coherent low-frequency radio emission from M dwarf systems shares phenomenological similarities with produced by magnetospheric processes the gas giant planets of our Solar System. Such beamed electron-cyclotron maser can be driven a star-planet interaction or breakdown in co-rotation between rotating plasma disk and stellar magnetosphere. Both models suggest that could periodic. Here we present longest interferometric monitoring campaign an system, composed twenty-one ≈8 h epochs taken two series observing blocks separated year. We achieved total on-source time 6.5 days. show binary CR Draconis has 3 σ detection rate 90 −8 +5 % when noise floor ≈0.1 mJy is reached, median flux density 0.92 mJy, consistent circularly polarised handedness, fraction 66%. resolve three bright bursts dynamic spectra, revealing brightest elliptically polarised, confined to 4 MHz bandwidth centred on 170 MHz, reaches 205 mJy. The burst structure mottled, indicating it consists unresolved sub-bursts. striking resemblance Jupiter. near-constant high brightness temperature, highly-circularly-polarised radiation circular polarisation handedness implies via instability. Optical photometric data reveal system rotation period 1.984 ± 0.003 observe no periodicity data, but sampling observations produces window function would hide near two-day signal.