NGC5044-N50: Una etapa evolutiva intermedia entre galaxias compactas azules (BCD) y enanas elípticas (dE)

CELLONE, S. A.; BUZZONI, A.

Tafí del Valle

Congreso; 44a. Reunión Anual AAA; 2000

AAA

We present results of two-colour photometry with high time resolution of the violently variable BL Lac object AO 0235+164. We have found extreme intranight variability with amplitudes of ~100 % over time scales of 24 hours. Changes of 0.5 magnitudes in both R and V bands were measured within a single night, and variations up to 1.2 magnitudes occurred from night to night. A complete outburst with an amplitude ~30 % was observed during one of the nights, while the spectrum remained unchanged. This seems to support an origin based on a thin relativistic shock propagating in such a way that it changes the viewing angle, as recently suggested by Kraus et al. (1999, A&A 344, 807) and Qian et al. (2000, A&A 357, 84).