Context. The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. The maximum brightness detected was R = 12.0, which represents the most luminous quasar state thus far observed (M B ∼ −31.4). Aims. In order to follow the emission behaviour of the source in detail, a large multiwavelength campaign was organized by the Whole Earth Blazar Telescope (WEBT). Methods. Continuous optical, near-IR and radio monitoring was performed in several bands. ToO pointings by the Chandra and INTEGRAL satellites provided additional information at high energies in May 2005. Results. The historical radio and optical light curves show different behaviours. Until about 2001.0 only moderate variability was present in the optical regime, while prominent and long-lasting radio outbursts were visible at the various radio frequencies, with higher-frequency variations preceding the lower-frequency ones. After that date, the optical activity increased and the radio flux is less variable. This suggests that the optical and radio emissions come from two separate and misaligned jet regions, with the inner optical one acquiring a smaller viewing angle during the 2004−2005 outburst. Moreover, the colour-index behaviour (generally redder-when-brighter) during the outburst suggests the presence of a luminous accretion disc. A huge mm outburst followed the optical one, peaking in June−July 2005. The high-frequency (37−43 GHz) radio flux started to increase in early 2005 and reached a maximum at the end of our observing period (end of September 2005). VLBA observations at 43 GHz during the summer confirm the brightening of the radio core and show an increasing polarization. An exceptionally bright X-ray state was detected in May 2005, corresponding to the rising mm flux and suggesting an inverse-Compton nature of the hard X-ray spectrum. Conclusions. A further multifrequency monitoring effort is needed to follow the next phases of this unprecedented event.

Abstract. We present the results of surface photometry on a new sample of Blue Compact Dwarf galaxies (BCDGs), in continuation to a previous paper (Doublier et al. 1997, hereafter Paper I). The 22 galaxies (plus two companions) discussed in the present paper have been selected in the Southern Hemisphere, from several lists. An atlas containing isophotal maps, surface brightnesses and B − R color profiles of the sample is given, together with the tables containing the photometric parameters.The results are consistent with those obtained in Paper I for objects selected from the Byurakan Surveys in the Northern hemisphere. Similarly, we find about one fourth of the BCDGs showing a dominant r 1/4 brightness distribution component, one fourth of the BCDG showing a dominant exponential surface brightness profile, and about half of them show composite brightness distributions. Integrated properties, colors, mean surface brightnesses and luminosity-radius relations are investigated and discussed for the objects presented in this paper and Paper I. We found that r 1/4 BCDGs tend to show a different behaviour compared to the exponential BCDGs, with respect to colors, compactness and luminosity-radius relations. We also include a brief study of the surroundings of the galaxies, where we find several candidate companions.Key words: galaxies: compact -galaxies: photometrygalaxies: starburst -galaxies: structure Send offprint requests to: V. Doublier Based on observations collected at the 1.54 m Danish Telscope at the European Southern observatory (La Silla, Chile).

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