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arXiv 1306.5962astro-ph.GA
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本地泡沫55 pc内灭绝?

Local Bubble. Extinction within 55 pc?

Jens Knude

摘要:

在局部ISM的映射中,知道在哪里可以测量局部气泡的边界的第一指示是有意义的。依巴谷距离结合B-V测光和某种光谱分类允许绘制空间消光分布。光度测量法几乎可以用于依巴谷星的完整样本,密歇根分类法可以用于delta = +5 deg(1900)以南的较亮恒星。对于北方和较暗的恒星,给出了光谱类型,例如HD类型,但通常缺少光度类别。然而,B-V测光和视差确实允许矮星/巨星分离,这是因为在颜色星等图中,红化矢量的斜率值与主序的梯度相比,其形式为:B-V vs. M_V+A_V = V+5(1+log(pi)),以及依巴谷样本中存在的相当浅的消光。本文给出依巴谷2距离小于55 pc的恒星的中值A_V(l,b)分布。第一、第二象限的北部消光最大,可达0.2等,第三和第四象限的南部消光最小,可达0.05等。消光极小值的边界在几度的角分辨率上显得相当连贯

英文摘要:

In the mapping of the local ISM it is of some interest to know where the first indications of the boundary of the Local Bubble can be measured. The Hipparcos distances combined to B-V photometry and some sort of spectral classification permit mapping of the spatial extinction distribution. Photometry is available for almost the complete Hipparcos sample and Michigan Classification is available for brighter stars south of delta = +5 deg (1900). For the northern and fainter stars spectral types, e.g. the HD types, are given but a luminosity class is often missing. The B-V photometry and the parallax do, however, permit a dwarf/giant separation due to the value of the slope of the reddening vector compared to the gradient of the main sequence in a color magnitude diagram, in the form: B-V vs. M_V+A_V = V+5(1+log(pi)), together with the rather shallow extinction present in the Hipparcos sample. We present the distribution of median A_V(l, b) for stars with Hipparcos 2 distances less than 55 pc. The northern part of the first and second quadrant has most extinction, up to 0.2 mag and the southern part of the third and fourth quadrant the slightest extinction, 0.05 mag. The boundary of the extinction minimum appears rather coherent on an angular resolution of a few degrees

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