Constraining Stellar Coronal Mass Ejections Through Multi-Wavelength Analysis of the Active M Dwarf EQ Peg

TL;DR

This study used multi-wavelength observations of the active M dwarf EQ Peg to constrain stellar coronal mass ejections, finding no evidence of type II radio bursts and setting limits on their properties, thus informing stellar mass loss models.

Contribution

First simultaneous multi-wavelength analysis of EQ Peg to constrain stellar CMEs using radio and optical data, applying solar scaling relations to predict CME parameters.

Findings

No drifting radio bursts detected in 20 hours of observations.

Constraints placed on brightness temperature and source size of potential bursts.

Predicted CME parameters suggest flares were insufficient to produce detectable type II bursts.

Abstract

Stellar coronal mass ejections remain experimentally unconstrained, unlike their stellar flare counterparts which are observed ubiquitously across the electromagnetic spectrum. Low frequency radio bursts in the form of a type II burst offer the best means of identifying and constraining the rate and properties of stellar CMEs. CME properties can be further improved through the use of proposed solar-stellar scaling relations and multi-wavelength observations of CMEs through the use of type II bursts and the associated flare expected to occur occur alongside. We report on 20 hours of observation of the nearby, magnetically active, and well characterized M dwarf star EQ Peg. The observations are simultaneously observed with the Jansky Very Large Array at their P-band (230-470 MHz) and at the Apache Point observatory in the SDSS u' filter ($\lambda$ = 3557 \AA). Dynamic spectra of the P band data, constructed to search for signals in the frequency-time domains, did not reveal evidence for drifting radio bursts that could be ascribed to type II bursts. Given the sensitivity of our observations, we are able to place limits on the brightness temperature and source size of any bursts which may have occurred. Using solar scaling rations on four observed stellar flares, we predict CME parameters. Given the constraints on coronal density and photospheric field strength, our models suggest that the observed flares would have been insufficient to produce detectable type II bursts at our observed frequencies. We consider the implications of these results, and other recent findings, on stellar mass loss.