ASKAP detects first solar-like radio burst from Proxima Cen, indicative of coronal mass ejection activity

New research published in The Astrophysical Journal on 9 December detailed multiwavelength observations of a powerful flare and associated radio bursts from Proxima Centauri, the nearest star and exoplanet host to the Sun.

The radio bursts, detected by ASKAP, are the most compelling examples of solar-like radio burst activity detected from another star to date. The properties of the radio bursts following the optical flare identify them as a solar-like type IV burst event. 


Caption: Multiwavelength overview of the flare and associated radio bursts. The top panel shows the ASKAP dynamic spectrum over the 14-hour observation, revealing a sequence of intense radio bursts. The middle panel shows the frequency-averaged ASKAP lightcurves, showing the highly-polarised nature of the radio bursts. The bottom panel shows data from optical facilities (NASA’s TESS, the Zadko 1m Telescope, and the ANU 2.3m Telescope), revealing a powerful, long-duration flare event. Taken together, these observations reveal the association between the low-frequency radio bursts and the intense optical flaring activity. 

Although M-dwarf flares at optical to X-ray wavelengths are well-studied, their space weather environment – describing the conditions of the plasma beyond the stellar atmosphere, and around their companion planets – has been difficult to observationally constrain. 

Frequent exposure of planets to strong space weather events from their host stars may lead to magnetospheric compression and atmospheric erosion – presenting a serious threat to their habitability.

A promising avenue toward understanding the space weather around active stars is the detection of solar-like radio bursts. These low-frequency radio bursts from the Sun (such as type II or type IV bursts) are frequently associated with optical or X-ray flaring activity, and provide important information about space weather events like coronal mass ejections – massive expulsions of energetic plasma and magnetic fields from the stellar corona. 

Although low-frequency radio bursts are frequently detected from other active stars, they have historically shown very little correlation with flaring activity at optical or X-ray wavelengths, frustrating attempts to interpret the radio bursts in the solar paradigm.

Our detection of this type IV burst from Proxima Cen with ASKAP is the most compelling example of a solar-like burst from another star to date.  On the Sun, type IV bursts only occur following powerful coronal mass ejections This type IV burst from Proxima Cen is therefore indicative of a coronal mass ejection event from the star. 

Caption: Artist’s conception of a flare-coronal mass ejection event from Proxima Centauri. Credit: Mark Myers/ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)

This marks an important step in our attempts to understand the space weather around active stars, but there is still more work to be done. 

While our detections are indicative of the violent space weather environment around the star, we cannot directly measure the properties of these events with this observation alone. Future observations of similar events, combining low-frequency radio with X-ray and ultraviolet observations, may provide the information needed to study these phenomena in more detail.

With ASKAP surveys beginning to take off, and with the rapid development of other low-frequency radio facilities, including the SKA, we are poised to make rapid progress in this area in the coming years.

Author: Andrew Zic, University of Sydney
 
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