A VERY BRIGHT, VERY HOT, and VERY LONG FLARING EVENT from the M DWARF BINARY SYSTEM DG CVn

Rachel A. Osten, Adam Kowalski, Stephen A. Drake, Hans Krimm, Kim Page, Kosmas Gazeas, Jamie Kennea, Samantha Oates, Mathew Page, Enrique De Miguel, Rudolf Novák, Tomas Apeltauer, Neil Gehrels

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30 Scopus citations

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 X 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 >1020 cm2, 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 ∼ 104 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 1035 and 9 1035 erg, and optical flare energies at E V of 2.8 1034 and 5.2 1034 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.

Original languageEnglish (US)
Article number174
JournalAstrophysical Journal
Volume832
Issue number2
DOIs
StatePublished - Dec 1 2016

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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