arXiv 0911.36892009-11astro-ph.SR

行星状星云中心恒星激发类参数的估算

An Evaluation of the Excitation Class Parameter for the Central Stars of Planetary Nebulae

Warren A. Reid, Quentin A. Parker

备注：: 14 pages, 18 figure. This peer reviewed paper has been accepted for publication in PASA
DOI：: 10.1071/AS09055

摘要：

利用大麦云星云（LMC）中586颗新发现和已知的行星状星云（PNe），对目前用于估算行星状星云（PNe）中心星激发级的三种主要方法进行了比较和评价。为了实现这一点，我们运行了一系列的评估测试，使用来自去红，通量校准光谱的线比。方法之间的显著差异被暴露。通过比较激发类别与H-β线通量来创建图表。最好的方法，然后比较公布的温度使用Zanstra方法和评估其能力，以反映中央恒星的有效温度和演变。因此，我们呼吁根据所使用的不同输入参数澄清术语“激励类别”。第一种方法，我们称之为Exneb，完全依赖于某些关键发射线的比率。第二种方法，我们称之为Ex*，包括建模，以创建一个连续的变量，光学厚PNE在麦哲伦云，旨在更密切地关系到内在的恒星参数。第三种方法，我们称之为Ex [OIII]/H-β，因为[OIII]/H-β比率与其他温度诊断隔离使用。这些方法中的每一种都被证明在用作中心恒星温度的指标时有严重的缺点。最后，我们提出了一种新的方法（Exrho），用于估计结合[OIII]/H-β和HeII 4686/H-β比值的激发类。虽然任何试图提供准确的中央恒星温度使用来自星云线的激发类将始终是有限的，我们表明，这种新方法提供了一个实质性的改进，比以前的方法，更好的协议，通过Zanstra方法获得的温度。

英文摘要：

The three main methods currently in use for estimating the excitation class of planetary nebulae (PNe) central stars are compared and evaluated using 586 newly discovered and previously known PNe in the Large Magellanic Cloud (LMC). In order to achieve this we ran a series of evaluation tests using line ratios derived from de-reddened, flux calibrated spectra. Pronounced differences between the methods are exposed. Diagrams were created by comparing excitation classes with H-beta line fluxes. The best methods are then compared to published temperatures using the Zanstra method and assessed for their ability to reflect central star effective temperatures and evolution. As a result we call for a clarification of the term `excitation class' according to the different input parameters used. The first method, which we refer to as Exneb relies purely on the ratios of certain key emission lines. The second method, which we refer to as Ex* includes modeling to create a continuous variable and, for optically thick PNe in the Magellanic Clouds, is designed to relate more closely to intrinsic stellar parameters. The third method, we refer to as Ex [OIII]/H-beta since the [OIII]/H-beta ratio is used in isolation to other temperature diagnostics. Each of these methods is shown to have serious drawbacks when used as an indicator for central star temperature. Finally, we suggest a new method (Exrho) for estimating excitation class incorporating both the [OIII]/H-beta and the HeII4686 /H-beta ratios. Although any attempt to provide accurate central star temperatures using the excitation class derived from nebula lines will always be limited, we show that this new method provides a substantial improvement over previous methods with better agreement to temperatures derived through the Zanstra method.

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