We have used high-resolution Hubble Space Telescope Wide Field Planetary Camera 2 and ground-based wide-field images to determine the center of gravity and construct an extended radial density and brightness pro. le of the cluster NGC 6752 including, for the first time, detailed star counts in the very inner region. The barycenter of the nine innermost X-ray sources detected by Chandra is located only 1."9 off the new center of gravity. Both the density and the brightness profile of the central region are best fitted by a double King model, suggesting that NGC 6752 is experiencing a post-core-collapse bounce. Taking advantage of our new optical data, we discuss the puzzling nature of the accelerations displayed by the innermost millisecond pulsars detected in this cluster. We discuss two possible origins to the accelerations: ( 1) the overall cluster gravitational potential, which would require a central projected mass-to-light ratio of the order of 6 - 7 and the existence of a few thousand solar masses of low-luminosity matter within the inner 0.08 pc of NGC 6752, and (2) the existence of a local perturber(s) of the pulsar dynamics, such as a recently proposed binary black hole of intermediate (100 - 200 M(.)) mass.
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机译:我们已使用高分辨率哈勃太空望远镜广角行星相机2和地面广角图像确定重心,并构造了扩展的径向密度和亮度pro。 NGC 6752星团的1e,首次包括非常内部区域的详细恒星数。钱德拉(Chandra)检测到的最里面的9个X射线源的重心位于距新重心仅1.“ 9的位置。中心区域的密度和亮度分布都最好使用双King模型拟合,这表明NGC 6752正在经历核后崩溃反弹,利用我们的新光学数据,我们讨论了在该星团中检测到的最里面的毫秒脉冲星所显示的加速度的令人困惑的性质,我们讨论了加速度的两个可能的来源:(1)整体星团的引力,这将要求中心投影的质量与光之比约为6-7,并且在NGC 6752的内部0.08 pc内存在几千个低发光度的太阳质量,并且( 2)存在脉冲星动力学的局部扰动,例如最近提出的中等质量(100-200 M(。))的二进制黑洞。
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