Example of SED fits to two cores in the active region. Top panel: all flux densities can be fitted with a single greybody; there is no excess at 70 μm, and this core is recognised as a pre-stellar core. The core in the lower panel has an excess flux density at 70 μm (the point has not been excluded from the fit, hence the large χ²). This could be due either to the core being heated from the outside by the FUV radiation field, or to a protostar inside the core (see Sect. 4.2).