%0 Journal Article %T Low-frequency monitoring of flare star binary CR Draconis: long-term electron-cyclotron maser emission %+ Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA) %A Callingham, J. %A Pope, B. %A Feinstein, A. %A Vedantham, H. %A Shimwell, T. %A Zarka, P. %A Tasse, C. %A Lamy, L. %A Veken, K. %A Toet, S. %A Sabater, J. %A Best, P. %A van Weeren, R. %A Röttgering, H. %A Ray, T. %< avec comité de lecture %@ 0004-6361 %J Astronomy and Astrophysics - A&A %I EDP Sciences %V 648 %P A13 %8 2021-04 %D 2021 %R 10.1051/0004-6361/202039144 %Z Physics [physics]/Astrophysics [astro-ph]Journal articles %X Recently detected coherent low-frequency radio emission from M dwarf systems shares phenomenological similarities with emission produced by magnetospheric processes from the gas giant planets of our Solar System. Such beamed electron-cyclotron maser emission can be driven by a star-planet interaction or a breakdown in co-rotation between a rotating plasma disk and a stellar magnetosphere. Both models suggest that the radio emission could be periodic. Here we present the longest low-frequency interferometric monitoring campaign of an M dwarf system, composed of twenty-one ≈8 h epochs taken in two series of observing blocks separated by a year. We achieved a total on-source time of 6.5 days. We show that the M dwarf binary CR Draconis has a low-frequency 3 σ detection rate of 90 −8 +5 % when a noise floor of ≈0.1 mJy is reached, with a median flux density of 0.92 mJy, consistent circularly polarised handedness, and a median circularly polarised fraction of 66%. We resolve three bright radio bursts in dynamic spectra, revealing the brightest is elliptically polarised, confined to 4 MHz of bandwidth centred on 170 MHz, and reaches a flux density of 205 mJy. The burst structure is mottled, indicating it consists of unresolved sub-bursts. Such a structure shares a striking resemblance with the low-frequency emission from Jupiter. We suggest the near-constant detection of high brightness temperature, highly-circularly-polarised radiation that has a consistent circular polarisation handedness implies the emission is produced via the electron-cyclotron maser instability. Optical photometric data reveal the system has a rotation period of 1.984 ± 0.003 days. We observe no periodicity in the radio data, but the sampling of our radio observations produces a window function that would hide the near two-day signal. %G English %2 https://u-paris.hal.science/hal-03256523/document %2 https://u-paris.hal.science/hal-03256523/file/aa39144-20.pdf %L hal-03256523 %U https://u-paris.hal.science/hal-03256523 %~ OBSPM %~ INSU %~ CNRS %~ LESIA %~ PSL %~ SORBONNE-UNIVERSITE %~ SORBONNE-UNIV %~ SU-SCIENCES %~ UNIV-PARIS %~ UNIVERSITE-PARIS %~ UP-SCIENCES %~ OBSPM-PSL %~ SU-TI %~ ALLIANCE-SU %~ SANTE-PLANTES-ENVIRONNEMENT