The 2008 Outburst in the Young Stellar System Z CMa: The First Detection of Twin Jets

TL;DR

This study uses adaptive optics spectroscopy to discover twin jets in the Z CMa binary system, linking jet wiggling to a potential companion and outburst activity, providing new insights into the system's outflow mechanisms.

Contribution

First detection of twin jets in Z CMa, revealing the Herbig Be star drives a large outflow and the FUOR drives a smaller jet, with jet wiggling indicating a possible companion.

Findings

Herbig Be star drives a parsec-scale outflow.

FUOR component drives a ~0.4 jet.

Jet wiggling suggests a companion causing outbursts.

Abstract

The Z CMa binary is understood to undergo both FU Orionis (FUOR) and EX Orionis (EXOR) type outbursts. While the SE component has been spectro- scopically identified as an FUOR, the NW component, a Herbig Be star, is the source of the EXOR outbursts. The system has been identified as the source of a large outflow, however, previous studies have failed to identify the driver. Here we present adaptive optics (AO) assisted [FeII] spectro-images which reveal for the first time the presence of two jets. Observations made using OSIRIS at the Keck Observatory show the Herbig Be star to be the source of the parsec-scale outflow, which within 2'' of the source shows signs of wiggling and the FUOR to '' be driving a ~ 0.4 jet. The wiggling of the Herbig Be star's jet is evidence for an additional companion which could in fact be generating the EXOR outbursts, the last of which began in 2008 (Grankin & Artemenko 2009). Indeed the dy- namical scale of the wiggling corresponds to a time-scale of 4-8 years which is in agreement with the time-scale of these outbursts. The spectro-images also show a bow-shock shaped feature and possible associated knots. The origin of this structure is as of yet unclear. Finally interesting low velocity structure is also observed. One possibility is that it originates in a wide-angle outflow launched from a circumbinary disk.