Volume 374, Number 3, August II 2001
|Page(s)||1072 - 1084|
|Section||Stellar structure and evolution|
|Published online||15 August 2001|
Microwave plasma emission of a flare on AD Leo
Pulkovo Observatory, 196140 St. Petersburg, Russia e-mail: firstname.lastname@example.org
2 Astrophysikalisches Institut Potsdam, 14482 Potsdam, Germany
3 Institute of Applied Physics, 603600 Nizhny Novgorod, Russia e-mail: email@example.com
4 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: firstname.lastname@example.org
5 Universitätssternwarte Hamburg, 21029 Hamburg, Germany e-mail: email@example.com
Corresponding author: B. Kliem, firstname.lastname@example.org
Accepted: 6 April 2001
An intense radio flare on the dMe star AD Leo, observed with the Effelsberg radio telescope and spectrally resolved in a band of 480 MHz centred at 4.85 GHz is analysed. A lower limit of the brightness temperature of the totally right handed polarized emission is estimated as K (with values K considered to be more probable), which requires a coherent radio emission process. In the interpretation we favour fundamental plasma radiation by mildly relativistic electrons trapped in a hot and dense coronal loop above electron cyclotron maser emission. This leads to densities and magnetic field strengths in the radio source of cm-3 and G. Quasi-periodic pulsations during the decay phase of the event suggest a loop radius of cm. A filamentary corona is implied in which the dense radio source is embedded in hot thin plasma with temperature K and density . Runaway acceleration by sub-Dreicer electric fields in a magnetic loop is found to supply a sufficient number of energetic electrons.
Key words: stars: activity / stars: flare / stars: coronae / radio continuum: stars / radiation mechanisms: non-thermal / acceleration of particles
© ESO, 2001
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