What Produced the Ultraluminous Supernova Remnant in NGC 6946?
Abstract
The ultraluminous supernova remnant (SNR) in NGC 6946 is the brightest known SNR in X-rays, ~1000 times brighter than Cas A. To probe the nature of this remnant and its progenitor, we have obtained high-dispersion optical echelle spectra. The echelle spectra detect H-alpha, [N II], and [O III] lines, and resolve these lines into a narrow (FWHM ~20--40 km/s) component from un-shocked material and a broad (FWHM ~250 km/s) component from shocked material. Both narrow and broad components have unusually high [N II]/H-alpha ratios, ~1. Using the echelle observation, archival HST images, and archival ROSAT X-ray observations, we conclude that the SNR was produced by a normal supernova, whose progenitor was a massive star, either a WN star or a luminous blue variable. The high luminosity of the remnant is caused by the supernova ejecta expanding into a dense, nitrogen-rich circumstellar nebula created by the progenitor.
Keywords
Cite
@article{arxiv.astro-ph/9912003,
title = {What Produced the Ultraluminous Supernova Remnant in NGC 6946?},
author = {Bryan C. Dunne and Robert A. Gruendl and You-Hua Chu},
journal= {arXiv preprint arXiv:astro-ph/9912003},
year = {2009}
}
Comments
20 pages, 5 figures. To be published in The Astronomical Journal, March 2000