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Part of the book series: Astronomy and Astrophysics Library ((AAL))

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Abstract

A spherically symmetric, uniform HII region is ionized by an O7 star (mass about 50 M ), with an excitation parameter, which is defined as \(\mathrm {U} = \mathrm {N}_{\mathrm {e}}^{2/3} \, \mathrm {L(pc)} \) U = 68 pc cm2∕3. Background information needed: The excitation parameter U is used in the following problem. U is the radius of the HII region (in pc), multiplied by the 2∕3 power of the electron density.

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Wilson, T.L., Hüttemeister, S. (2018). Recombination Lines. In: Tools of Radio Astronomy - Problems and Solutions. Astronomy and Astrophysics Library. Springer, Cham. https://doi.org/10.1007/978-3-319-90820-5_14

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