Comparison of the effective temperatures, gravities and helium abundances of DAO white dwarfs from Balmer and Lyman line studies
Comparison of the effective temperatures, gravities and helium abundances of DAO white dwarfs from Balmer and Lyman line studies
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巴尔默线和莱曼线研究中 DAO 白矮星的有效温度、重力和氦丰度的比较
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
P. Dobbie
中科院分区：
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作者：
S. Good;M. Barstow;J. Holberg;D. Sing;M. Burleigh;P. Dobbie
利用巴尔默吸收系列氢的观测是一种确定白矮星表面重力和有效温度（teff）的行之有效的方法。在巴尔默线不能使用的情况下，可以使用氢莱曼系列代替。然而，Barstow等人先前的研究表明，对于温度高于~ 5万K的DAs（富氢，无氦），Lyman谱线系统地产生比Balmer谱线更高的T - eff值。对16颗DAO白矮星（混合氢/氦）的光学光谱和FUSE光谱的分析表明，使用不同数据集测量的温度在更高的温度下继续发散，在三个极端情况下，Lyman谱线得出的Teff超过120,000 K。在较低的重力和光度下，这些差异被观察到减少。氦的丰度也由两种波长下的He ii谱线的强度来确定。除了两个DAO+M矮双星外，尽管它们的温度差别很大，但它们的结果很吻合。对于这些，测量到的氦丰度的变化可能是由于在两个波长范围内观察到物体的不同时间造成的。
The use of observations of the hydrogen Balmer absorption series is a well-established method of determining the surface gravity and effective temperature ( T eff ) of white dwarfs. In situations where the Balmer lines cannot be used it is possible to use the hydrogen Lyman series instead. However, previous studies by Barstow et al. have shown that for DAs (hydrogen-rich, no helium) hotter than ∼50 000 K the Lyman lines systematically yield higher values of T eff than the Balmer lines. Analysis of optical and FUSE spectra of 16 DAO white dwarfs (hybrid hydrogen/helium) demonstrates that temperatures measured using the different data sets continue to diverge at even higher temperatures, and in three extreme cases Teff derived from the Lyman lines is in excess of 120 000 K. These discrepancies are observed to decrease at lower gravities and luminosities. Helium abundances were also determined from the strength of He ii lines in the two wavelength regimes. These agree well, even though the temperatures differ considerably, with the exception of two DAO+M dwarf binaries. For these, the change in the measured helium abundance may result from the different times at which the objects were observed in the two wavelength regimes.