The metallicity of the nebula surrounding the ultra-luminous X-ray source NGC 1313 X-2

✍ Scribed by E. Ripamonti; M. Mapelli; L. Zampieri; M. Colpi

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 118 KB
• Volume: 332
• Category: Article
• ISSN: 0004-6337
• DOI: 10.1002/asna.201011512

✦ Synopsis

Abstract

Recent models of the formation of ultra‐luminous X‐ray sources (ULXs) predict that they preferentially form in low‐metallicity environments. We look at the metallicity of the nebula surrounding NGC 1313 X‐2, one of the best‐studied ULXs. Simple estimates, based on the extrapolation of the metallicity gradient within NGC 1313, or on empirical calibrations (relating metallicity to strong oxygen lines) suggest a quite low metal content (Z ∼ 0.1__Z__~⊙~). But such estimates do not account for the remarkably strong X‐ray flux irradiating the nebula. Then, we build photoionization models of the nebula using CLOUDY; using such models, the constraints on the metallicity weaken substantially, as we find 0.15__Z__~⊙~ ≤ Z ≤ 0.5__Z__~⊙~ (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)