Detection of High-Energy Gamma-Ray Emission from the Globular Cluster 47 Tucanae with Fermi
Detection of High-Energy Gamma-Ray Emission from the Globular Cluster 47 Tucanae with Fermi
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DOI：
10.1126/science.1177023
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发表时间：
2009-08
期刊：
影响因子：
56.9
通讯作者：
A. Abdo;M. Ackermann;M. Ajello;W. Atwood;M. Axelsson;L. Baldini;J. Ballet;G. Barbiellini;
中科院分区：
文献类型：
--
作者：
A. Abdo;M. Ackermann;M. Ajello;W. Atwood;M. Axelsson;L. Baldini;J. Ballet;G. Barbiellini;
伽玛射线脉冲星富矿我们所知道的大多数脉冲星都是通过它们的无线电发射被探测到的;少数脉冲伽玛射线已知，但首先是在其他波长被探测到的（见Halpern的透视图）。Abdo等人（第840页，7月2日在线发表;见封面）利用费米伽马射线太空望远镜，仅根据伽马射线发射就发现了16颗以前未知的双星。其中13个与以前未被识别的伽马射线源相吻合，解决了30年来的身份之谜。脉冲星是快速旋转的中子星。随着时间的推移，它们会减速并停止辐射;然而，如果它们是在一个双星系统中，它们的自旋速率可以通过来自伴星的质量转移而增加，开始作为毫秒双星的新生命。在另一项研究中，Abdo等人（第845页）报告了球状星团47 Tuccenda的伽马射线辐射的探测，这是来自星团核心的毫秒级恒星系。这些数据表明，在47个图克卡蒙中有多达60个毫秒级的彗星，是无线电观测预测的两倍。在进一步的同伴研究中，阿卜杜等人（第848页，7月2日在线发表）搜索了费米大面积望远镜的数据，寻找星团外所有已知毫秒级恒星的脉动，发现其中8个恒星的伽马射线脉动。它们的性质类似于其他伽马射线双星，这表明它们具有相同的基本发射机制。事实上，这两组中子星都倾向于伽马射线产生于中子星星外磁层的发射模型。费米大天区望远镜在这个球状星团中发现了多达60个毫秒的双星，是射电观测预测的两倍。利用费米伽马射线太空望远镜上的大面积望远镜获得的数据，我们报告了在17σ的显著性水平上从球状星团47 Tuccenda探测到200兆电子伏以上的伽马射线发射。球状星团被认为会发射伽马射线，因为它们包含大量的毫秒级双星。图47的光谱形状与毫秒双星的伽马射线发射一致。观测到的伽马射线亮度意味着在47图克卡蒙中存在60毫秒的射电星的上限。
Gamma-Ray Pulsar Bonanza Most of the pulsars we know about were detected through their radio emission; a few are known to pulse gamma rays but were first detected at other wavelengths (see the Perspective by Halpern). Using the Fermi Gamma-Ray Space Telescope, Abdo et al. (p. 840, published online 2 July; see the cover) report the detection of 16 previously unknown pulsars based on their gamma-ray emission alone. Thirteen of these coincide with previously unidentified gamma-ray sources, solving the 30-year-old mystery of their identities. Pulsars are fast-rotating neutron stars. With time they slow down and cease to radiate; however, if they are in a binary system, they can have their spin rates increased by mass transfer from their companion stars, starting a new life as millisecond pulsars. In another study, Abdo et al. (p. 845) report the detection of gamma-ray emission from the globular cluster 47 Tucanae, which is coming from an ensemble of millisecond pulsars in the cluster's core. The data imply that there are up to 60 millisecond pulsars in 47 Tucanae, twice as many as predicted by radio observations. In a further companion study, Abdo et al. (p. 848, published online 2 July) searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars outside of stellar clusters, finding gamma-ray pulsations for eight of them. Their properties resemble those of other gamma-ray pulsars, suggesting that they share the same basic emission mechanism. Indeed, both sets of pulsars favor emission models in which the gamma rays are produced in the outer magnetosphere of the neutron star. The Fermi Large Area Telescope reveals up to 60 millisecond pulsars in this globular cluster, twice as many as predicted by radio observations. We report the detection of gamma-ray emissions above 200 megaelectron volts at a significance level of 17σ from the globular cluster 47 Tucanae, using data obtained with the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. Globular clusters are expected to emit gamma rays because of the large populations of millisecond pulsars that they contain. The spectral shape of 47 Tucanae is consistent with gamma-ray emission from a population of millisecond pulsars. The observed gamma-ray luminosity implies an upper limit of 60 millisecond pulsars present in 47 Tucanae.