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Context. In August 2010, the sudden optical brightening of two young stellarobjects, located in the North America/Pelican Nebula Complex, was announced.Early observations indicated that these objects may belong to the FUor or EXorclass of young eruptive stars. The eruptions of FUors and EXors are oftenexplained by enhanced accretion of material from the circumstellar disk to theprotostar. Aims. In order to determine the true nature of these two objects, westarted an optical and near-infrared monitoring program, and complemented ourdata with archival observations and data from the literature. Methods. We plotand analyze pre-outburst and outburst spectral energy distributions (SEDs),multi-filter light curves, and color-color diagrams. Results. HBC 722brightened monotonically in about two months, and the SED obtained duringmaximum brightness indicates the appearance of a hot, single-temperatureblackbody. The current fading rate implies that the star will return toquiescence in about a year, questioning its classification as a bone fide FUor.The outburst of VSX J205126.1+440523 happened more gradually, but reached anunprecedentedly high amplitude. At 2.5 months after the peak, its light curvesshow a deep minimum, when the object was close to its pre-outburst opticalbrightness. Further monitoring indicates that it is still far from beingquiescent. Conclusions. The shape of the light curves, the bolometricluminosities and accretion rates suggest that these objects do not fit into theclassic FUor group. Although HBC 722 exhibit all spectral characteristics of abona fide FUor, its luminosity and accretion rate is too low, and its timescaleis too fast compared to classical FUors. VSX J205126.1+440523 seems to be anexample where quick extinction changes modulate the light curve.

The outburst and nature of two young eruptive stars in the North America/Pelican Nebula Complex