NGC 3199, the Banana nebula

Constellation: Carina

NGC 3199, the Banana nebula (a.k.a. Carina’a smile) is a an emission nebula in the constellation Carina. The star HD 89358 is the Wolf-Rayet star 18 (WR 18, on sky chart). Link to interactive sky chart.

Hot Gas in the Wolf–Rayet Nebula NGC 3199

J. A. Toalá, A. P. Marston, M. A. Guerrero, Y.-H. Chu and R. A. Gruendl
Published 2017 September 1 • © 2017. The American Astronomical Society. All rights reserved.
Citation: J. A. Toalá et al 2017 ApJ 846 76. DOI: 10.3847/1538-4357/aa8554

The Wolf–Rayet (WR) nebula NGC 3199 has been suggested to be a bow shock around its central star, WR 18, which is presumably a runaway star, because optical images of the nebula show a dominating arc of emission southwest of the star. We present the XMM-Newton detection of extended X-ray emission from NGC 3199, unveiling the powerful effect of the fast wind from WR 18. The X-ray emission is brighter in the region southeast of the star and an analysis of the spectral properties of the X-ray emission reveals abundance variations: (i) regions close to the optical arc present nitrogen-rich gas enhanced by the stellar wind from WR 18 and (ii) gas at the eastern region exhibits abundances close to those reported for the nebular abundances derived from optical studies, which is a signature of an efficient mixing of the nebular material with the stellar wind. The dominant plasma temperature and electron density are estimated to be T ≈ 1.2 × 10⁶ K and n_e = 0.3 cm⁻³ with an X-ray luminosity in the 0.3–3.0 keV energy range of L_X = 2.6 × 10³⁴ erg s⁻¹. Combined with information derived from Herschel and the recent Gaia first data release, we conclude that WR 18 is not a runaway star and that the formation, chemical variations, and the shape of NGC 3199 depend on the initial configuration of the interstellar medium.

Telescope & Mount:

PlaneWave CDK17 (F6.8) on a Software Bisque Paramount ME mount.

Imaging:

Camera: Player One Zeus-Mono (bin 2×2)

Data:
Ha: 60x600s
O3: 59x600s
S2: 60x600s

Stars:
Red: 120x60s
Green: 119x60s
Blue: 122x60s

Total integration time: 35h 51′