Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995a%26a...299..739s&link_type=abstract
Astronomy and Astrophysics, v.299, p.739
Astronomy and Astrophysics
Astrophysics
18
Stars: Flare, Stars: Uv Cet, X-Rays: Bursts, Radio Continuum: Stars
Scientific paper
Multifrequency observations of the flare of December 31, 1991 on UV Ceti are presented. The radio observations were carried out with the Effelsberg 100-m radio telescope at 4750MHz, whereas optical photometry was performed using the 0.8-m telescope of the Wendelstein Observatory in the five UBVRI colors. The radio burst started ~5min after the maximum of an optical flare. X-ray emission observed with the ROSAT PSPC before and after the optical flare conclusively demonstrates that an X-ray flare has occured. Several narrow-bandwidth radio spikes with duration of about 0.1s, peak flux density of 250mJy, and >=75% LH polarization were recorded. An interpretation of the spikes in terms of electron-cyclotron maser emission (ECME) and, alternatively, coherent plasma emission is proposed. The flare plasma parameters obtained from radio and soft X-ray data are as follows: n_e_=~10^11^/cm-3, T_e_=~10^7^K, B=~(200-800)G. Using these values, the escape windows for ECME have been calculated at ν=4.75GHz. It has been shown that there is actually no "perpendicular" window for the ordinary mode at the second and third harmonics of the electron gyrofrequency. The optical flare's cross-section area and the temperature of the "cool" plasma were found to be 4x10^16^cm^2^ and 16000K, respectively. Possible reasons for the time delay between the optical and radio flares as well as stellar flare models are discussed.
Barwig Heinz
Fuerst Ernst
Hildebrandt Joachim
Krueger Andre
Schmitt Jerome
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