Molecules in \eta\ Carinae

TL;DR

This study reports the detection of six new molecules and their isotopes in e2 Carinae, revealing in situ formation from CNO-processed stellar material and challenging previous assumptions about molecular abundances.

Contribution

First detection of multiple molecules and isotopes in e2 Carinae, showing in situ formation from stellar material and revising previous abundance estimates.

Findings

CO and HCO+ are not under-abundant in e2 Carinae.

Nitrogen- and 13C-containing molecules are overabundant by about ten times.

Molecular emission originates in the dense, possibly clumpy, central region of the nebula.

Abstract

We report the detection toward \eta\ Carinae of six new molecules, CO, CN, HCO+, HCN, HNC, and N2H+, and of two of their less abundant isotopic counterparts, 13CO and H13CN. The line profiles are moderately broad (about 100 km /s) indicating that the emission originates in the dense, possibly clumpy, central arcsecond of the Homunculus Nebula. Contrary to previous claims, CO and HCO+ do not appear to be under-abundant in \eta\ Carinae. On the other hand, molecules containing nitrogen or the 13C isotope of carbon are overabundant by about one order of magnitude. This demonstrates that, together with the dust responsible for the dimming of eta Carinae following the Great Eruption, the molecules detected here must have formed in situ out of CNO-processed stellar material.