The Search for Signatures Of Transient Mass Loss in Active Stars

TL;DR

This study used LOFAR radio observations to search for signatures of transient mass loss events, like CMEs, in an active M dwarf star, setting upper limits on their occurrence rate and proposing a new interpretative methodology.

Contribution

It presents the first LOFAR-based search for stellar CMEs in YZ CMi and introduces a methodology to interpret flare and CME observations jointly.

Findings

No confirmed type II radio bursts detected in 15 hours.

Established an upper limit of 0.067 shocks per hour for YZ CMi.

Proposed a new approach to constrain stellar CME rates and test solar scaling relations.

Abstract

The habitability of an exoplanet depends on many factors. One such factor is the impact of stellar eruptive events on nearby exoplanets. Currently this is poorly constrained due to heavy reliance on solar scaling relationships and a lack of experimental evidence. Potential impacts of Coronal Mass Ejections (CMEs), which are a large eruption of magnetic field and plasma from a star, are space weather and atmospheric stripping. A method for observing CMEs as they travel though the stellar atmosphere is the type II radio burst, and the new LOw Frequency ARray (LOFAR) provides a means for detection. We report on 15 hours of observation of YZ Canis Minoris (YZ CMi), a nearby M dwarf flare star, taken in LOFAR's beam-formed observation mode for the purposes of measuring transient frequency-dependent low frequency radio emission. The observations utilized Low-Band Antenna (10-90 MHz) or High-Band Antenna (110-190 MHz) for five three-hour observation periods. In this data set, there were no confirmed type II events in this frequency range. We explore the range of parameter space for type II bursts constrained by our observations Assuming the rate of shocks is a lower limit to the rate at which CMEs occur, no detections in a total of 15 hours of observation places a limit of $\nu_{type II} < 0.0667$ shocks/hr $ \leq \nu_{CME}$ for YZ CMi due to the stochastic nature of the events and limits of observational sensitivity. We propose a methodology to interpret jointly observed flares and CMEs which will provide greater constraints to CMEs and test the applicability of solar scaling relations.