Abstract
BL Lacertae was observed with the MAGIC telescope from August to December 2005 (22.2 hours) and from July to September 2006 (26.0 hours). A very high energy (VHE) gamma-ray signal was discovered with a 5.1sigma excess in the 2005 data. BL Lacertae is the first low-frequency peaked BL Lac object for which a clear detection of VHE gamma-ray signal below the previous upperlimits has been obtained. The 2006 data contains no signal, which is interpreted as lower VHE gamma-ray emission state. In this paper we show that the drop in flux level was also seen in the optical and millimetre regimes, suggesting a connection between these energy bands.
