* Astronomy

Title: Two extremely luminous WN stars in the Galactic center with circumstellar emission from dust and gas
Authors: A. Barniske, L. M. Oskinova, W.-R. Hamann

We study relatively isolated massive WN-type stars in the Galactic centre. The K-band spectra of WR102ka and WR102c are exploited to infer the stellar parameters and to compute synthetic stellar spectra using the Potsdam Wolf-Rayet (PoWR) model atmosphere code. These models are combined with dust-shell models for analysing the Spitzer IRS spectra of these objects. Archival IR images complement the interpretation. We report that WR102ka and WR102c are among the most luminous stars in the Milky Way. The mid-IR continua for both objects are dominated by dust emission. For the first time we report the presence of dust in the close vicinity of WN stars. Also for the first time, we have detected lines of pure-rotational transitions of molecular hydrogen in a massive-star nebula. A peony-shaped nebula around 102ka is resolved by the Spitzer MIPS camera. We attribute the formation of this nebula to the recent evolutionary history of WR102ka.

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Both Eta Carinae and the Peony nebula star are evolved blue giants known as "Wolf-Rayet" stars, which have masses of 100 to 200 Suns. Either could self-destruct as a supernova at any moment.
The Peony nebula star lies about 26,000 light years away and Eta Carinae about 7500 light years away.

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