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arXiv 1710.10596astro-ph.HEgr-qc
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标量-张量引力中脉冲星的脉冲轮廓

Pulse profiles from a pulsar in scalar-tensor gravity

Hajime Sotani

摘要:

在极帽模型的基础上,假设中子星上存在对跖热点,研究了几种恒星模型下标量张量引力理论中中子星的脉冲轮廓。然后,我们发现标量张量引力中的标量化中子星的脉冲轮廓与广义相对论中的脉冲轮廓几乎相同,即,没有标量场,如果两颗恒星的恒星紧密度非常相似。也就是说,标量场的存在并不直接改变来自中子星的脉冲轮廓,而即使在标量张量引力下,恒星的致密性对确定脉冲形状也至关重要。此外,我们还发现标量化中子星的脉冲波形与广义相对论中相同质量的中子星的脉冲波形相似,而脉冲波形中最小振幅与最大振幅的比值强烈地依赖于标量-张量引力中的耦合常数,这取决于旋转轴和磁轴之间的角度以及旋转轴和朝向观察者的方向之间的角度。因此,直接观测脉冲轮廓加上对恒星质量的额外观测,可以提取强场区引力理论的印记。

英文摘要:

The pulse profile from a neutron star in scalar-tensor theory of gravity is examined for several stellar models, where we assume the existence of the antipodal hot spots on the neutron star based on the polar cap model. Then, we find that the pulse profile from the scalarized neutron star in scalar-tensor gravity is almost the same as that in general relativity, i.e., without a scalar field, if the stellar compactness of the both stars is very similar. That is, the existence of the scalar field does not directly change the pulse profile from the neutron star, while the stellar compactness is crucial for determining the pulse shape even in the scalar-tensor gravity. Additionally, we find that the pulse shape from the scalarized neutron star is more or less similar to that from the neutron star with the same mass in general relativity, while the ratio of the minimum amplitude to the maximum amplitude in the pulse profile depend strongly on the coupling constant in scalar-tensor gravity, depending on the angle between the rotational and magnetic axes and the angle between the rotational axis and the direction to the observer. So, the direct observation of the pulse profile together with the additional observation of the stellar mass, one may extract the imprint of the gravitational theory in strong field regime.

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