naa a22 4500 510732437 CHVBK 20180411082958.0 cr unu---uuuuu 180411e20130801xx s 000 0 eng 10.1134/S1063772913080040 doi (NATIONALLICENCE)springer-10.1134/S1063772913080040 Lovkaya M. Crimean Astrophysical Observatory, Nauchnyi, Crimea, Ukraine aut Analysis of the fine temporal structure of optical flares on AD Leo on February 4, 2003 [Elektronische Daten] [M. Lovkaya] The fine temporal structure of two flares observed on the red-dwarf flare star AD Leo on February 4, 2003 with the 1.25-m telescope of the Crimean Astrophysical Observatory in a rapidphotometry mode is studied. One flare lasted approximately 5 min and another was longer than 8 min. The amplitudes in the U band were 1.65 m and 1.76 m . A detailed color analysis shows that the flare parameters at the maximum brightnesses corresponded to blackbody radiation with temperatures of approximately 14 000 and 13 000 K, enabling the monitoring of temperature — the rapid cooling of flare plasma near the flare maxima—for the first time. During 1.5 and 3.5 min at the maxima, the flares radiated as blackbodies, but these behaved as optically thick plasmas in the Balmer continuum on the second half of the descending branches. At the end of the first flare, the plasma became optically thin in the Balmer continuum; the final stage of the second flare was not observed. The flare areas at the luminosity maxima were 2.1 × 1018 and 3.0×1018 cm2 in a blackbody approximation, or 0.07%and 0.11%of the visible stellar disk. The occurrence of quasi-periodic brightness pulsations during red-dwarf flares on time scales of approximately ten seconds is confirmed. Pleiades Publishing, Ltd., 2013 Astronomy Reports Springer US; http://www.springer-ny.com 57/8(2013-08-01), 603-610 1063-7729 57:8<603 2013 57 11444 https://doi.org/10.1134/S1063772913080040 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1134/S1063772913080040 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Lovkaya M. Crimean Astrophysical Observatory, Nauchnyi, Crimea, Ukraine aut NATIONALLICENCE 773 0- Astronomy Reports Springer US; http://www.springer-ny.com 57/8(2013-08-01), 603-610 1063-7729 57:8<603 2013 57 11444 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer