High Resolution Infrared Imaging & Spectroscopy of the Z Canis Majoris System During Quiescence & Outburst

TL;DR

This study uses high-resolution infrared imaging and spectroscopy to analyze the Z Canis Majoris binary system during quiescence and outburst, revealing which component caused the outburst and clarifying the origin of CO features.

Contribution

It provides the first high-resolution photometry and spectroscopy of the system during different phases, conclusively identifying the source of the outburst and the CO spectral features.

Findings

Outburst was caused solely by the Herbig Ae/Be component.

The FU Ori component's luminosity decreased by about 30%.

CO absorption is from the FU Ori star, while CO emission is from the Herbig Ae/Be star.

Abstract

We present adaptive optics photometry and spectra in the JHKL-bands along with high spectral resolution K-band spectroscopy for each component of the Z Canis Majoris system. Our high angular resolution photometry of this very young (<1 Myr) binary, comprised of an FU Ori object and a Herbig Ae/Be star, were gathered shortly after the 2008 outburst while our high resolution spectroscopy was gathered during a quiescent phase. Our photometry conclusively determine that the outburst was due solely to the embedded Herbig Ae/Be member, supporting results from earlier works, and that the optically visible FU Ori component decreased slightly (~30%) in luminosity during the same period, consistent with previous works on the variability of FU Ori type systems. Further, our high-resolution K-band spectra definitively demonstrate that the 2.294 micron CO absorption feature seen in composite spectra of the system is due solely to the FU Ori component, while a prominent CO emission feature at the same wavelength, long suspected to be associated with the innermost regions of a circumstellar accretion disk, can be assigned to the Herbig Ae/Be member. These findings are in contrast to previous analyses (e.g. Malbet et al 2010, Benisty et al. 2010) of this complex system which assigned the CO emission to the FU Ori component.