Relationship between X-ray and ultraviolet emission of flares from dMe stars observed by XMM-Newton
Raassen, A. J. J.;
Mewe, R.;
Audard, M.;
Güdel, M.;
van Driel-Gesztelyi, L.;
Branduardi-Raymont, G.;
Mitra-Kraev, U.;
Harra, L. K.;
Kay, H. R. M.
United Kingdom, Switzerland, United States, Netherlands, France, Hungary
Abstract
We present simultaneous ultraviolet and X-ray observations of the dMe-type flaring stars AT Mic, AU Mic, EV Lac, UV Cet and YZ CMi obtained with the XMM-Newton observatory. During 40 h of simultaneous observation we identify 13 flares which occurred in both wave bands. For the first time, a correlation between X-ray and ultraviolet flux for stellar flares has been observed. We find power-law relationships between these two wavelength bands for the flare luminosity increase, as well as for flare energies, with power-law exponents between 1 and 2. We also observe a correlation between the ultraviolet flare energy and the X-ray luminosity increase, which is in agreement with the Neupert effect and demonstrates that chromospheric evaporation is taking place.
2005
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Astronomy and Astrophysics
XMM-Newton
77
