Constraining Stellar Coronal Mass Ejections through Multi-wavelength Analysis of the Active M Dwarf EQ Peg

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 (λ = 3557Å).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.

Suppression of Coronal Mass Ejections in Active Stars by an Overlying Large-scale Magnetic Field: A Numerical Study

“…Guenther & Emerson (1997) found a distinct Hα blue-wing enhancement in a spectrum of the weak T Tauri star DZ Cha (RX J1149.8-7850) they attributed to a CME and deduced an ejected mass in the range of 10 18 − 10 19 g, which is a factor 10 − 100 larger than for the most massive solar CMEs. Moschou et al (2017) followed the suggestion of Favata & Schmitt (1999), that an absorption event during a giant flare on Algol could be a CME, to deduce an even larger ejected mass in the range 10 21 − 10 22 g. However, several studies attempting to detect of stellar CMEs using radio and optical data found no significant signatures (e.g., Leitzinger et al 2014, Crosley et al 2016, Villadsen 2017, Crosley & Osten 2018).…”

Flare-productive active regions

“…In this regard, Crosley and Osten ( 2018a , b ) attempted to detect type II bursts on nearby, magnetically-active, well-characterized M dwarf star EQ Peg. During 20 h of simultaneous radio and optical observation, they detected four optical flare signatures but no radio features identifiable as type II bursts.…”

The evolution of the solar wind

“…3, cf. Crosley and Osten 2018). With an observationally derived flare frequency distribution, this could then be used to estimate the total mass loss in CME-dominated winds.…”