ROSAT-Detection of a giant X-ray flare on LkHalpha92

Thomas Preibisch, Hans Zinnecker & Juergen Schmitt

Astronomy & Astrophysics, 279, L33, (1993)


We report the detection of a giant X-ray flare on the classical T Tauri star LkHalpha 92 with the ROSAT PSPC. In this flare the PSPC count rate rose by a factor of more than 100 in a time interval of about 2000 sec. Our X-ray observations cover most of the rise phase as well as part of the decay phase of the flare.

We model the X-ray spectra obtained at different flare phases to determine temperature and emission measure of the flaring plasma. Combining the thus derived X-ray luminosity with the observed decay time scale of about 7800 sec, we estimate the total energy release of the flare in the ROSAT PSPC band (0.1 - 2.4 keV) to be about 4 x 10^36 erg, which is more than a factor of 10^4 greater than the energy release in the strongest solar flares and still more than a factor of 100 greater than that in typical flares on T Tauri stars.

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ROSAT images of the flare on LkHalpha92

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