Table 2
Summary of our classification system for the different types of radio emission detected on stars.
| Classification | Type | (N, M) | Timescale | Bandwidth | |V|/I | Internal structure | Interpretation |
|---|---|---|---|---|---|---|---|
| (Fractional width) | |||||||
| Type A | Broadband emission | (40,42) | >3h | >2GHz | <30% | Smooth emission in time and frequency. | Incoherent |
| (>1) | The spectrum has a positive spectral index. | (Gyromagnetic) | |||||
| Type B | Confined burst | (6,42) | 3–6 h | 200–500 MHz | >90% | Bursts that are strongly confined in frequency. | Coherent |
| (0.1–0.5) | Do not show prototypical internal frequency structure. | (ECMI) | |||||
| TypeC | Slow sweeps | (9,42) | 1–3 h | 200–500MHz | >90% | These bursts move to lower or higher frequencies over time. | Coherent |
| (0.07–0.5) | Do not change direction in frequency and can have multiple lanes of emission. | (ECMI) | |||||
| The drift rate is 5MHzmin−1 or lower. | |||||||
| Type D | Fast sweeps | (1,42) | 0.5–1 h | 400–700MHz | >90% | Bursts with larger drift rates around 50 MHz min-1. | Coherent |
| (0.13-0.6) | They can have several sweeps in a short time, which might not move in the same direction. | (ECMI) | |||||
| Type E | Shot bursts | (2,42) | <15min | <100MHz | >50% | These bursts look like bullet holes in the dynamic spectrum. | Coherent |
| (<0.025) | They are strongly confined in both frequency and time. | (ECMI?) | |||||
| No detected internal time-frequency structure. | |||||||
| Type F | Irregular bursts | (4,42) | 1–6 h | 0.3–1.5GHz | >90% | Similar to the confined and sweep bursts, but less constrained. | Coherent |
| (0.1–1) | Moves around in frequency and can change directions. | (ECMI) | |||||
| Type G | Pulse bursts | – | 5 min–1 h | 60 MHz–6 GHz | >90% | These bursts are broadband and often last a few minutes. | Coherent |
| (>0.5) | They can have strong variations on short timescales. | (–) | |||||
| Not detected on AU Mic. |
Notes. Examples of each category detected on AU Mic are shown in Fig. 1. Several bursts fit into more than one category, in which case they are counted in both. There can also be multiple separate types of emission in one epoch. (N, M) indicates the number of epochs in which emission of that type has been detected, compared to the total number of epochs. |V|/I shows the absolute value of the circular polarisation fraction. The last column shows whether this type of emission is coherent or incoherent, along with our interpretation of this type of emission when detected on AUMic.
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