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Relationship between X-ray and ultraviolet emission of flares from dMe stars observed by XMM-Newton

U. Mitra-Kraev·L. K. Harra·M. Guedel·M. Audard·G. Branduardi-Raymont·H. R. M. Kay·R. Mewe·A. J. J. Raassen·L. van Driel-Gesztelyi
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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 hours 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.

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U. Mitra-Kraev, L. K. Harra, M. Guedel, M. Audard, G. Branduardi-Raymont, H. R. M. Kay, R. Mewe, A. J. J. Raassen, L. van Driel-Gesztelyi. 2004-10-25. Relationship between X-ray and ultraviolet emission of flares from dMe stars observed by XMM-Newton. https://doi.org/10.1051/0004-6361%3A20041201

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