# The population of M dwarfs observed at low radio frequencies

**Authors:** J. R. Callingham, H. K. Vedantham, T. W. Shimwell, B. J. S. Pope, I. E. Davis, P. N. Best, M. J. Hardcastle, H. J. A. Rottgering, J. Sabater, C. Tasse, R. J. van Weeren, W. L. Williams, P. Zarka, F. de Gasperin, A. Drabent  
**arXiv:** [2110.03713](https://arxiv.org/abs/2110.03713)  
**Date:** 2021-10-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2110.03713v1/

## Key points

- Low-frequency radio emission from stars provides valuable information about the conditions of their outer corona, mass-ejection events, and space weather.
- Previous low-frequency searches for radio-emitting stellar systems have lacked sensitivity to detect the general population.
- A recent study published in Nature Astronomy by J.R. Callingham et al. presented 19 detections of coherent radio emission associated with known M dwarfs from a blind flux-limited low-frequency survey.
- Coherent radio emission is ubiquitous across the M dwarf main sequence and independent of known coronal and chromospheric activity indicators.
- Large-scale analogues of magnetospheric processes seen in gas-giant planets are likely driving the radio emission associated with quiescent stars.
- The slowest-rotating stars in this sample are candidate systems to search for star-planet interaction signatures.
- Low-frequency emissions from stars with low X-ray luminosities and long rotation periods are more likely to be generated by Electron Cyclotron Maser Instability (ECMI).
- Plasma emission could generate observed radio emissions from coronally active and rapidly rotating stars such as AD Leo and DO Cep.
- The study's low frequency radio stellar system detection statistics for Gaia DR2 are shown on a Gaia colour magnitude diagram, highlighting the importance of conducting blind flux limited low frequency surveys to detect general populations of radio emitting stellar systems.
- These results have implications for our understanding of space weather and planetary habitability around M dwarf stars.

## Summary

Low-frequency radio emission from stars provides valuable information about the conditions of their outer corona, mass-ejection events, and space weather. However, previous low-frequency searches for radio-emitting stellar systems have lacked the sensitivity to detect the general population, instead largely focusing on targeted studies of anomalously active stars. In a recent study published in Nature Astronomy by J.R. Callingham et al., 19 detections of coherent radio emission associated with known M dwarfs were presented from a blind flux-limited low-frequency survey. The study shows that coherent radio emission is ubiquitous across the M dwarf main sequence and that the radio luminosity is independent of known coronal and chromospheric activity indicators. While plasma emission can generate low-frequency emission from the most chromospherically active stars in their sample, the origin of radio emission from the most quiescent sources is yet to be ascertained. Large-scale analogues of magnetospheric processes seen in gas-giant planets are likely driving the radio emission associated with these quiescent stars. The slowest-rotating stars in this sample are candidate systems to search for star-planet interaction signatures. The study also highlights that low-frequency emissions from stars with low X-ray luminosities and long rotation periods are more likely to be generated by Electron Cyclotron Maser Instability (ECMI), resembling the emission processes seen in sub-stellar objects such as ultracool dwarfs and gas giant planets. For coronally active and rapidly rotating stars such as AD Leo and DO Cep, plasma emission could plausibly generate observed radio emissions. The authors present their low frequency radio detections on a Gaia colour magnitude diagram showing that their detected stellar systems are indicated by red circles, with red squares highlighting known close (< 3 AU separation) binaries. The colour of the density map represents the number of sources in each coloured pixel, as set by the colour bar in the top right corner of the plot. The study's low frequency radio stellar system detection statistics for Gaia DR2 are shown in bottom panel, with LoTSS - Gaia DR2 detection statistics for different Gaia colour bins. In conclusion, this study provides a new understanding of coherent radio emission from M dwarf stars and highlights the importance of conducting blind flux limited low frequency surveys to detect general populations of radio emitting stellar systems. The findings suggest that large scale analogues of magnetospheric processes seen in gas giant planets likely drive the radio emission associated with quiescent stars, while plasma emission could generate observed radio emissions from coronally active and rapidly rotating stars. These results have implications for our understanding of space weather and planetary habitability around M dwarf stars.