@article {28409,
	title = {A Very Bright, Very Hot, and Very Long Flaring Event from the M Dwarf Binary System DG CVn},
	volume = {832},
	year = {2016},
	month = {2016/12/1},
	pages = {174},
	abstract = {On 2014 April 23, the Swift satellite responded to a hard X-ray transient detected by its Burst Alert Telescope, which turned out to be a stellar flare from a nearby, young M dwarf binary DG CVn. We utilize observations at X-ray, UV, optical, and radio wavelengths to infer the properties of two large flares. The X-ray spectrum of the primary outburst can be described over the 0.3-100 keV bandpass by either a single very high-temperature plasma or a nonthermal thick-target bremsstrahlung model, and we rule out the nonthermal model based on energetic grounds. The temperatures were the highest seen spectroscopically in a stellar flare, at T <SUB> X </SUB> of 290 MK. The first event was followed by a comparably energetic event almost a day later. We constrain the photospheric area involved in each of the two flares to be >10<SUP>20</SUP> cm<SUP>2</SUP>, and find evidence from flux ratios in the second event of contributions to the white light flare emission in addition to the usual hot, T \~{} 10<SUP>4</SUP> K blackbody emission seen in the impulsive phase of flares. The radiated energy in X-rays and white light reveal these events to be the two most energetic X-ray flares observed from an M dwarf, with X-ray radiated energies in the 0.3-10 keV bandpass of 4 {\texttimes} 10<SUP>35</SUP> and 9 {\texttimes} 10<SUP>35</SUP> erg, and optical flare energies at E <SUB> V </SUB> of 2.8 {\texttimes} 10<SUP>34</SUP> and 5.2 {\texttimes} 10<SUP>34</SUP> erg, respectively. The results presented here should be integrated into updated modeling of the astrophysical impact of large stellar flares on close-in exoplanetary atmospheres.},
	keywords = {Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics, stars: coronae, stars: flare, stars: individual: DG CVn},
	isbn = {0004-637X},
	url = {https://ui.adsabs.harvard.edu/abs/2016ApJ...832..174O},
	author = {Osten, Rachel A. and Kowalski, Adam and Drake, Stephen A. and Krimm, Hans and Page, Kim and Gazeas, Kosmas and Kennea, Jamie and Oates, Samantha and Page, Mathew and de Miguel, Enrique and Nov{\'a}k, Rudolf and Apeltauer, Tomas and Gehrels, Neil}
}
