The 2008-2009 outburst of the young binary system Z CMa unraveled by interferometry with high spectral resolution

TL;DR

This study used high-resolution interferometry to analyze the 2008-2009 outburst of the young binary system Z CMa, revealing that the outburst was linked to the Herbig Be star's accretion disk and outflow activity.

Contribution

First high spectral resolution interferometric observations of Z CMa during an outburst, providing detailed insights into the accretion and outflow processes involved.

Findings

Herbig Be star produced strong Brγ emission during outburst

Asymmetric spectro-astrometric measurements suggest outflow contribution

Keplerian disk model alone cannot explain the observations

Abstract

Z CMa is a young binary system consisting of an Herbig primary and a FU Ori companion. Both components seem to be surrounded by active accretion disks and a jet was associated to the Herbig B0. In Nov. 2008, K. Grankin discovered that Z CMa was exhibiting an outburst with an amplitude larger than any photometric variations recorded in the last 25 years. To study the innermost regions in which the outburst occurs and understand its origin, we have observed both binary components with AMBER/VLTI across the Br{\gamma} emission line in Dec. 2009 in medium and high spectral resolution modes. Our observations show that the Herbig Be, responsible for the increase of luminosity, also produces a strong Br{\gamma} emission, and they allow us to disentangle from various origins by locating the emission at each velocities through the line. Considering a model of a Keplerian disk alone fails at reproducing the asymmetric spectro-astrometric measurements, suggesting a major contribution from an outflow.