Connecting Flares and Transient Mass-Loss Events in Magnetically Active Stars

Abstract

We explore the ramification of associating the energetics of extreme magnetic reconnection events with transient mass loss in a stellar analogy with solar eruptive events. We establish energy partitions relative to the total bolometric radiated flare energy for different observed components of stellar flares, and show that there is rough agreement for these values with solar flares. We apply an equipartition between the bolometric radiated flare energy and kinetic energy in an accompanying mass ejection, seen in solar eruptive events and expected from reconnection. This allows an integrated flare rate in a particular waveband to be used to estimate the amount of associated transient mass loss. This approach is supported by a good correspondence between observational flare signatures on high flaring rate stars and the Sun, which suggests a common physical origin.If the frequent and extreme flares that young solar-like stars and low-mass stars experience are accompanied by transient mass loss in the form of coronal mass ejections, then the cumulative effect of this mass loss could be large. We find that for young solar-like stars and active M dwarfs, the total mass lost due to transient magnetic eruptions could have significant impacts on disk evolution, and thus planet formation, and also exoplanet habitability. Subject headings: stars: activity -stars: flare -stars: late-type -stars: mass-loss redshifted than blue-shifted emission components, and the hetergeneous nature of the events prevents a systematic exploration. Thus, in the absence of conclusive evidence of stellar CMEs, stellar astronomers must look to the Sun to gain insight into transient stellar mass loss on magnetically active stars. The commonality of stellar flare phenomenology with solar observations suggests that an extrapolation of solar flare/CME behavior to the more distant stars should be appropriate. The Sun has a low overall rate of mass loss (Ṁ ⊙ = 2 ×10 −14 M ⊙ yr −1 ), of which transient mass loss events comprise a minor component (typically <10%; Howard et al. 1985). However, if mass loss due to CMEs scales with flare occurrence, stars with a high flaring rate ought to also show an enhanced rate of mass lost due to transient events like CMEs. Recently, Aarnio et al. (2012) used an empirical scaling between solar flareX-ray energy and associated CME mass and extrapolated to pre-main sequence stars with measured X-ray flare energies to deduce mass loss rates of putative CMEs associated with the stellar flares. They inferred high levels of CME-related mass loss in these solar-type pre-main sequence stars of 10 −12 -10 −9 M ⊙ yr −1 . Drake et al. (2013) also used an empirical relationship between solar flare X-ray energy and associated CME mass to extrapolate to observed stellar coronal X-ray luminosities and investigate the radiative and kinetic energy requirements, assuming that the stellar coronal emissions are produced by flares whose occurrence has a power-law dependence on flare energy. They likewise find a large CME mass loss rate. Th...

Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

“…This work built on earlier theoretical models of time-steady solar wind scaling relations (Cranmer & Saar 2011) and on empirical correlations between CME properties and highenergy flare emissions (e.g., Aarnio et al 2012;Drake et al 2013;Osten & Wolk 2015). Although it is likely that the magnetic properties of a star are more fundamental (i.e., they are what drive the flare and CME properties), it is also undeniable that they are much more difficult to observe than, say, flare light curves.…”

A VERY BRIGHT, VERY HOT, AND VERY LONG FLARING EVENT FROM THE M DWARF BINARY SYSTEM DG CVn

“…From their Table 2, we estimate the bolometric radiated energy two ways: using the extrapolated U-band energy described above, as well as the X-ray energies calculated in Section 3.3.1. The estimation of bolometric energy using the coronal radiated energy is imprecise because the formulation of Osten & Wolk (2015) only considered the 0.01-10 keV energy range, whereas the BFF event clearly has significant contribution at higher photon energies. The two estimates of bolometric energy differ from each other by a factor of threeor more.…”

“…The amount of energy radiated in the V filter bandpass is about an order of magnitude less than this. Section 3.3.4 discusses the energy partition within BFF and F2; both appear to be X-ray luminous compared to expectations from scaling of optical flare energy to bolometric radiated energy from Osten & Wolk (2015). The integrated V-band energy from the EVLac superflare described in Osten et al (2010) could not be calculated due to insufficient data, but we note that the large enhancement flare on the very-low-mass star described in Stelzer et al (2006) had nearly equal amounts of radiated energy in the X-ray and V filter bandpasses (but overall lower integrated values, at ∼3×10 32 erg).…”

The Characteristics of Solar X-Class Flares and CMEs: A Paradigm for Stellar Superflares and Eruptions?

“…(Drake et al, 2013) made comparisons of solar power-law relationships to stellar energies to extrapolate what mass loss may be possible from solar-like stars. It is clear that there is potential for significant mass loss (see also Osten and Wolk, 2015).…”