Evolution of the dust mass loss with luminosity along the giant branch of the globular cluster 47 Tucanae
Evolution of the dust mass loss with luminosity along the giant branch of the globular cluster 47 Tucanae
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沿球状星团 47 Tucanae 巨分支的尘埃质量损失随光度的演变
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
A. Jorissen
中科院分区：
文献类型：
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作者：
Aafifa Ramdani;A. Jorissen
本文利用ISOCAM和DENIS资料研究了球状星团47 Tuc巨分支中恒星尘埃质量损失的性质。5个油田的光栅地图，涵盖的地区从4美元 imes 4美元至15美元 用11.5 μ m的ISOCAM（LW 10滤光片）获得了离团簇中心不同距离处的x 15 arcmin ~ 2。覆盖的字段包括该集群中已知的大多数红色变量。探测阈值约为0.2 mJy，使我们能够探测到11.5 μ m的巨星，一直到水平分支。与LMC/SMC球状星团中具有较大的关闭质量的情况相反，在观测场中没有发现尘埃遮蔽的渐近巨星分支星。颜色指数$[12]{-}[2]$（基于ISO 11.5 μ m通量和DENIS K s星等）被用作尘埃排放（以及尘埃质量损失）的诊断。它的演化与光度沿着的巨大分支显示，尘埃质量损失只存在于V3 $（唯一的集群米拉变量在本研究中观察到）和V18 $，一个星星呈现间歇性的变化。这一结论证实了恒星脉动在尘埃形成和随后的质量损失中的重要性。
The present paper investigates the properties of the dust mass loss in stars populating the giant branch of the globular cluster 47 Tuc, by combining ISOCAM and DENIS data. Raster maps of 5 fields covering areas ranging from $4 imes4$ to $15 imes15$ arcmin 2 at different distances from the center of the cluster have been obtained with ISOCAM at 11.5 μ m (LW10 filter). The covered fields include most of the red variables known in this cluster. A detection threshold of about 0.2 mJy is achieved, allowing us to detect giant stars at 11.5 μ m all the way down to the horizontal branch. No dust-enshrouded asymptotic giant branch stars have been found in the observed fields, contrary to the situation encountered in LMC/SMC globular clusters with larger turnoff masses. The color index $[12]{-}[2]$ (based on the ISO 11.5 μ m flux and on the DENIS K s magnitude) is used as a diagnostic of dust emission (and hence dust mass loss). Its evolution with luminosity along the giant branch reveals that dust mass loss is only present in $V3$ (the only cluster Mira variable observed in the present study) and in $V18$, a star presenting intermittent variability. This conclusion confirms the importance of stellar pulsations in the dust formation and ensuing mass loss.