恒星包层中平均辐射强度的计算

ON CALCULATION OF AVERAGE RADIATION INTENSITY IN A STELLAR ENVELOPE

本文讨论了中央激发源在其周围包层中产生的平均辐射强度的计算问题。计算表明,通常星云理论中计算平均辐射强度的公式仅适用于光学薄的情况,且光学深度必须用从源表面开始计量的距离计算。在有物质抛射的恒星包层中,中央星产生的平均辐射强度必须严格计算,特别是在减速星风情况下。本文提出了严格计算的公式。

Average radiation intensity in envelope of a central star is usually divided into two parts, a stellar part produced by the continuum radiation from the star and a diffuse part resulting from the emission of ionized gas in a nebula.The former,which, is discussed in this article, is generally computed with formula (1) or more exactly with formula (2) in the theory of gaseous nebula. The results in our article indicate that the formula (2) can be used only in case that the envelope is optically thin, and the extinction distance should be measured from the surface of the star (see Figure 2f. As the optical depth τv^1, the stellar radiation field will be overestimated with formulas (2) and (9) and underestimated with formulae (2) and τv = τo Rp in a uniform envelope. In case of mass loss of stars the hydrogen density in an envelope will be so high that the optical depth is very large for the ionization radiation from the central star. Thus, the formula (7) must be used to compute exactly the stellar radiation field, especially in case of a decelerated stellar wind(see Figure 3). The exact formulae(13)-(18) to compute the optical depth are given here assuming a power distribution of electron density. As the non-LTE departure factor b,is a function of distance from a star, the envelope can be divided into many thin layers, and then the above formulae can be used.