A NEW X-RAY ANALYSIS OF THE OPEN CLUSTER BLANCO 1 USING WIDE-FIELD BVIc PHOTOMETRIC AND PROPER MOTION SURVEYS
A NEW X-RAY ANALYSIS OF THE OPEN CLUSTER BLANCO 1 USING WIDE-FIELD BVIc PHOTOMETRIC AND PROPER MOTION SURVEYS
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DOI：
10.1088/0004-6256/137/2/3230
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发表时间：
2009-01
期刊：
影响因子：
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通讯作者：
P. Cargile;D. James;I. Platais
中科院分区：
文献类型：
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作者：
P. Cargile;D. James;I. Platais
我们利用新的BVIc光度和固有运动数据集，对现有的ROSAT和XMM-Newton对南部疏散星团Blanco 1的x射线调查进行了新的分析。在我们的研究中，我们匹配了47个与Blanco 1星团成员相关的x射线源，其中6个在之前的x射线研究中被列为星团非成员。我们新的x射线源光学对应星表在彩色星等图中清晰地描绘了Blanco 1主序列，从早期的G光谱类型延伸到中m光谱类型。此外，我们还得到了新的x射线光度，以及已确认的星团成员的x射线与辐射光度的比值。我们将这些x射线特性与其他年轻疏散星团（包括同时期的昴星团）进行比较，以研究年龄与x射线活动之间的关系。我们发现Blanco 1中的恒星通常表现出与其他疏散星团相似的x射线特性，即早期型恒星的Lx/Lbol随质量的减少而增加，而V−Ic≥1.25的恒星的Lx/Lbol在10−3等时达到饱和极限。更一般地说，在Blanco 1中探测到的x射线恒星的x射线发射幅度与在其他年轻星团中看到的总体趋势一致。我们观察到x射线发射随年龄衰减，并且衰减速率与质量有关。具体来说，对于质量较大的恒星，趋势是斯库曼尼奇式的（即Lx/Lbol∝age - 1/2）；然而，当一个人到达较低的质量时，x射线发射的大小就不再是年龄的函数了。事实上，对于质量最低的恒星（m型），在它们生命的前1 ~ 1 Gyr内，x射线的产生没有可观察到的减少。然而，由于缺乏对低x射线通量的敏感性，可能存在x射线通量低于饱和水平的m型恒星，这些恒星未包括在我们的研究中。直接比较Blanco 1和昴宿星团，两个星团的成员具有相似的x射线特征；然而，Lx/Lbol的分布确实有一些差异，作为颜色的函数，可能与在昴宿星团CMD中看到的散射有关。此外，由于依赖照相光度法，以前对Blanco 1进行这种性质的比较是不可能的。在这里，精确、均匀和标准化的CCD测光技术可以对Blanco 1中恒星的x射线特性进行高保真、详细的研究，并将Blanco 1与其他得到充分研究的疏散星团进行彻底的比较。
We perform a new analysis of the extant ROSAT and XMM-Newton X-ray surveys of the southern open cluster Blanco 1, utilizing new BVIc photometric and proper motion data sets. In our study, we match optical counterparts to 47 X-ray sources associated with Blanco 1 cluster members, six of which were listed in previous X-ray studies as cluster nonmembers. Our new catalog of optical counterparts to X-ray sources clearly traces out the Blanco 1 main sequence in a color–magnitude diagram, extending from early G to mid-M spectral types. Additionally, we derive new X-ray luminosities as well as ratios of X-ray to bolometric luminosities for confirmed cluster members. We compare these X-ray properties to other young open clusters, including the coeval Pleiades cluster, to investigate the relationship between age and X-ray activity. We find that stars in Blanco 1 generally exhibit X-ray properties similar to those of other open clusters, namely increasing Lx/Lbol with reducing mass for earlier-type stars, and a saturation limit of Lx/Lbol at a magnitude of 10−3 for stars with V − Ic ≳ 1.25. More generally, the X-ray detected stars in Blanco 1 have X-ray emission magnitudes that agree with the overall trends seen in the other young clusters. We observe that X-ray emission decays as a function of age and the rate of this decay is mass dependent. Specifically, for higher mass stars, the trend is Skumanich like (i.e., Lx/Lbol ∝ age−1/2); however, as one goes to lower masses the magnitude of X-ray emission becomes less of a function of age. In fact, for the lowest mass stars (M-type), there is no observable reduction in X-ray production during the first ∼1 Gyr of their lives. However, due to a lack of sensitivity to low X-ray fluxes, there may exist M-type stars that have less than saturated levels of X-ray flux which are not included in our study. In a direct comparison of Blanco 1 to the Pleiades open cluster, members of both clusters have similar X-ray characteristics; however, there does appear to be some discrepancies in the distribution of Lx/Lbol as a function of color that may be related to scatter seen in the Pleiades CMD. Moreover, previous comparisons of this nature for Blanco 1 were not possible due to the reliance on photographic photometry. This is where the power of precise, homogeneous, and standardized CCD photometry allows for a high fidelity, detailed study of the X-ray properties of stars in Blanco 1, as well as a thorough comparison of Blanco 1 to other well-studied open clusters.