Vol. 597
In section 7. Stellar structure and evolution

The 2008 outburst in the young stellar system Z CMa. III. Multi-epoch high-angular resolution images and spectra of the components in near-infrared

by M. Bonnefoy, G. Chauvin, C. Dougados, et al. A&A 597, A91


Z CMa is a complex pre-main sequence binary with a current separation of 110 mas, known to consist of a FU Orionis star (SE component) and an embedded Herbig Be star (NW component). This paper presents a wealth of new observations, both imaging and spectroscopic, of each component of the Z CMa system during its most recent 2008-2009 outburst (as well as an extra observation once the system was back in its quiescent state). The authors confirm that the NW star dominates the system flux over the 1.1-3.8 mum range and is responsible for the photometric outburst. From extracted medium-resolution (R~2000-4000) near-infrared (1.1-2.4 mum) spectra of the individual components, the authors show that the SE component has a spectrum typical of FU Orionis objects, and that the NW component spectrum is characteristic of embedded out-bursting protostars and EX Or objects. The blueing of the continuum of the NW component along with the absolute flux and color-variation of the system during the outburst suggests that the outburst was caused by a complex interplay between (a) a variation of the extinction in the line of sight of the NW component, and (b) the emission of shocked regions close to the NW component.