The nature of strings in the nebula around Eta Carinae

TL;DR

This paper investigates the highly collimated, linear-velocity structures called strings in the nebula around Eta Carinae, revealing their unique properties and potential similarity to features in planetary nebulae.

Contribution

It provides the first detailed kinematic and morphological analysis of the strings, demonstrating their Hubble-law velocity profile and suggesting a new phenomenon in LBV nebulae.

Findings

Strings are extremely long, narrow, and follow a Hubble law with increasing velocity.

Five strings identified with lengths of 0.058 to 0.177 pc and widths of 0.002 pc.

Similar string-like structures found in planetary nebula NGC 6543.

Abstract

Eta Carinae is one of the most extreme cases of a Luminous Blue Variable star. A bipolar nebula of 17" size surrounds the central object. Even further out, a large amount of filamentary material extends to a distance of 30" or about 0.3 pc. In this paper we present a detailed kinematic and morphological analysis of some outer filaments in this nebula which we call strings. All strings are extremly long and narrow structures. We identified 5 strings which have sizes of 0.058 to 0.177 pc in length and a width of only 0.002 pc. Using high-resolution long-slit echelle spectroscopy it was found that the strings follow a Hubble law with velocities increasing towards larger distances from the star. With these unique properties, high collimation and linear increase of the radial velocity the strings represent a newly found phenomena in the structure and evolution of nebulae around LBVs. Finally, we show that morphologically similar strings can be found in the planetary nebula NGC 6543, a possible PN-counterpart to this phenomenon.