New eruptive variable in the massive star-forming region associated with IRAS 18507+0121

Aims: We report the discovery of a strong outburst of the embedded young stellar object (YSO) UKIDSS-J185318.36+012454.5, located in the star-forming region associated with IRAS 18507+0121 and the ultra-compact H II region GAL 034.4+00.23.
Methods: Using archival photometric data and images, we determined the amplitude and the epoch of the outburst as well as the evolution stage and the basic parameters of the object.
Results: According to the near- and mid-infrared colors and spectral energy distribution, we classify the object as an intermediate-mass YSO with Class 0/I evolution stage. The outburst apparently started between May 2003 and April 2004. The amplitude of the outburst is at least ΔK_s = 5.0 mag. The summation of the photometric and spectral data does not allow classifying UKIDSS-J185318.36+012454.5 as an FU Orionis (FUor) or EX Orionis (EXor) object. We can consider it as an eruptive variable with mixed characteristics or as an MNor type object.