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arXiv 0802.1304astro-ph
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XMM-Newton发现NGC 1313中的瞬态X射线脉冲星

XMM-Newton discovery of transient X-ray pulsar in NGC 1313

Sergey Trudolyubov

摘要:

我们报告的发现和分析的瞬态X射线脉冲星XMMU J031747.5-663010发现在2004年11月23日XMM-牛顿观测的螺旋星系NGC 1313。X射线源在0.3-7 keV能量范围内具有周期P~765.6 s的脉动和接近正弦的脉冲形状,脉冲分数~38%。XMMU J031747.5-663010的X射线谱很硬,在0.3-7 keV能带内符合光子指数约1.5的吸收简单幂律。该源的X射线特性和没有比20等更亮的光学/紫外对应物使我们能够将XMMU J031747.5-663010识别为位于NGC 1313中的吸积X射线脉冲星。它的吸收光度为0.3-7 keV,L~1.6 \times 10^{39} ergs/s,是已知最亮的X射线源之一。基于相对较长的脉冲周期和源的瞬态行为,我们将其归类为Be双星X射线脉冲星候选者。XMMU J 031747.5 -663010是在本星系群之外发现的第二颗X射线脉冲星,在附近的螺旋星系NGC 2403中发现了短暂的18秒脉冲源CXMMU J 073709.1 +653544。

英文摘要:

We report on the discovery and analysis of the transient X-ray pulsar XMMU J031747.5-663010 detected in the 2004 November 23 XMM-Newton observation of the spiral galaxy NGC 1313. The X-ray source exhibits pulsations with a period P~765.6 s and a nearly sinusoidal pulse shape and pulsed fraction ~38% in the 0.3-7 keV energy range. The X-ray spectrum of XMMU J031747.5-663010 is hard and is well fitted with an absorbed simple power law of photon index ~1.5 in the 0.3-7 keV energy band. The X-ray properties of the source and the absence of an optical/UV counterpart brighter than 20 mag allow us to identify XMMU J031747.5-663010 as an accreting X-ray pulsar located in NGC 1313. The estimated absorbed 0.3-7 keV luminosity of the source L~1.6\times 10^{39} ergs/s, makes it one of the brightest X-ray pulsars known. Based on the relatively long pulse period and transient behaviour of the source, we classify it as a Be binary X-ray pulsar candidate. XMMU J031747.5-663010 is the second X-ray pulsar detected outside the Local Group, after transient 18 s pulsating source CXOU J073709.1+653544 discovered in the nearby spiral galaxy NGC 2403.

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