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arXiv 1108.3567astro-ph.GAastro-ph.SR
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WR 38/38 a与隆凸鱼全绝灭与选择绝灭的比值

WR 38/38a and the ratio of total-to-selective extinction in Carina

David G. Turner

摘要:

根据UBV和JHK对星团成员的现有观测,对疏散星团Shorlin 1(与WR 38和WR 38 a相关的恒星群)进行了重新分析。特别是2 MASS的观测,意味着平均星团红化E(B-V)=1.45+-0.07和2.94+-0.12 kpc的距离。红化与UBV的结果一致,但只有当相关尘埃的全消光与选择消光之比为R=Av/E(B-V)=4.0+-0.1时,2 MASS和UBV系统的距离估计才一致。这两个结果是相似的,已经获得了在海山二区域相邻的集群通过类似的分析,这表明,“异常”的尘埃灭绝是广泛的通过该地区,特别是对群体变红相对较近的灰尘。与海山二复合体有关的尘埃本身似乎表现出更“正常”的性质。这些结果对解释银河系l=287-291度的旋臂距离有直接的意义,特别是这里的船底座臂可能略大于2 kpc,而不是以前研究中暗示的2.5-3 kpc。新导出的两个星团沃尔夫-拉叶星WR 38(WC 4)和WR 38 a(WN 5)的内禀参数与银河系疏散星团中其他WR星的内禀参数吻合得很好,而以前的情况并非如此。

英文摘要:

A reanalysis of the (seemingly very distant) open cluster Shorlin 1, the group of stars associated with WR 38 and WR 38a, is made on the basis of existing UBV and JHKs observations for cluster members. The 2MASS observations, in particular, imply a mean cluster reddening of E(B-V)=1.45+-0.07 and a distance of 2.94+-0.12 kpc. The reddening agrees with the UBV results provided that the local reddening slope is described by E(U-B)/E(B-V)=0.64+-0.01, but the distance estimates in the 2MASS and UBV systems agree only if the ratio of total-to-selective extinction for the associated dust is R=Av/E(B-V)=4.0+-0.1. Both results are similar to what has been obtained for adjacent clusters in the Eta Carinae region by similar analyses, which suggests that `anomalous' dust extinction is widespread through the region, particularly for groups reddened by relatively nearby dust. Dust associated with the Eta Carinae complex itself appears to exhibit more `normal' qualities. The results have direct implications for the interpretation of distances to optical spiral arm indicators for the Galaxy at l=287-291 degrees, in particular the Carina arm here is probably little more than ~2 kpc distant, rather than 2.5-3 kpc distant as implied in previous studies. Newly-derived intrinsic parameters for the two cluster Wolf-Rayet stars WR 38 (WC4) and WR 38a (WN5) are in good agreement with what is found for other WR stars in Galactic open clusters, which was not the case previously.

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