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arXiv 0807.4456astro-ph
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用Chandra对Trumpler 16中低质量恒星的X射线巡天

An X-ray survey of low-mass stars in Trumpler 16 with Chandra

J. F. Albacete-Colombo, F. Damiani, G. Micela, S. Sciortino, F. R. Harnden

摘要:

利用深Chandra X射线观测方法,对Trumpler 16(Tr 16)星域中的低质量恒星进行了识别和表征,并研究了它们的光学和近红外性质。我们比较了Tr 16星的X射线活动与猎户座和天鹅座OB 2星的已知特征。我们分析了一个88.4千秒的钱德拉ACIS-I观测指向中心的Tr 16。由于扩散X射线发射,使用PWDetect代码对两个不同的能量范围进行源检测:0.5-8.0 keV和0.9-8.0 keV。结果被合并成一个单一的最终名单。我们将X射线源与光学目录和2 MASS目录进行位置关联。使用基于IDL的例程ACIS-Extract提取源事件。使用Kolmogorov-Smirnov检验表征X射线可变性,并使用XSPEC拟合光谱。早期型大质量恒星的X射线光谱被单独分析。我们的X射线源列表包括1035个条目,其中660个具有近红外对应物,并且可能与Tr 16成员有关。从近红外色-色和色-星等图中,我们计算出恒星的单个质量和它们的Av值。大约15%的近红外对应物显示出磁盘引起的过度。X射线变异性在77个源中被发现。OB星发射的X射线比低质量星要柔和。Tr 16区域有非常丰富的低质量X射线发射恒星。它的星周盘的一个重要部分在其大质量恒星的强烈辐射场中幸存下来。质量为1.5-2.5 Mo的恒星显示出类似于天鹅座OB 2恒星的X射线活动,但比猎户座星云团成员的强度要低得多。

英文摘要:

We identify and characterize low-mass stars in the ~3 Myr old Trumpler 16 (Tr16) region by means of a deep Chandra X-ray observation, and study their optical and near-IR properties. We compare X-ray activity of Tr16 stars with known characteristics of Orion and Cygnus OB2 stars. We analyzed a 88.4 ksec Chandra ACIS-I observation pointed at the center of Tr16. Because of diffuse X-ray emission, source detection was performed using the PWDetect code for two different energy ranges: 0.5-8.0 keV and 0.9-8.0 keV. Results were merged into a single final list. We positionally correlate X-ray sources with optical and 2MASS catalogues. Source events were extracted with the IDL-based routine ACIS-Extract. X-ray variability was characterized using the Kolmogorov-Smirnov test and spectra were fitted by using XSPEC. X-ray spectra of early-type, massive stars were analyzed individually. Our list of X-ray sources consists of 1035 entries, 660 of which have near-IR counterparts and are probably associated with Tr16 members. From near-IR color-color and color-magnitudes diagrams we compute individual masses of stars and their Av values. About 15% of the near-IR counterparts show disk-induced excesses. X-ray variability is found in 77 sources. X-ray emission from OB stars appear softer than the low-mass stars. The Tr16 region has a very rich population of low-mass X-ray emitting stars. An important fraction of its circumstellar disks survive the intense radiation field of its massive stars. Stars with masses 1.5-2.5 Mo display X-ray activity similar to that of stars in Cyg OB2 but much less intense than observed for Orion Nebula Cluster members.

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