WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008. Unveiling different emission components

Understand

In 2007-2008 we carried out a new multiwavelength campaign of the Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the XMM-Newton satellite, to study its emission properties.

• The source was monitored in the optical-to-radio bands by 37 telescopes.
• The brightness level was relatively low.
• Some episodes of very fast variability were detected in the optical bands.