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arXiv 0806.1865astro-ph
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用MAGIC望远镜观测LS I +61 303的周期性甚高能gamma-ray发射

Periodic very high energy gamma-ray emission from LS I +61 303 observed with the MAGIC telescope

MAGIC Collaboration, J. Albert

摘要:

MAGIC合作最近报告了在TeV能量区域发现来自双星系统LS I +61 303的伽马射线发射。在这里,我们提出了新的观测结果,这个源的能量范围在300 GeV和3 TeV之间。2006年9月至12月期间,共采集了112小时的数据,涵盖该物体的4个轨道周期。这一大量的数据使我们能够产生一个积分通量光变曲线,第一次覆盖了LS I +61 303的所有轨道相位。此外,我们还获得了两个轨道相位仓的微分能谱,覆盖相位范围为0.5<phi<0.6和0.6<phi<0.7。两个相位仓中的光子指数在误差范围内是一致的,平均指数Gamma=2.6+-0.2_{stat}+-0.2_{sys}。LS I +61 303在TeV能量下以天为时间尺度变化。这些新的MAGIC测量使我们能够搜索VHE排放的夜间变化;然而,没有证据表明流量变化的时间尺度下降到30 minutes. To测试光变曲线中可能的周期结构,我们应用Lomb和Scargle开发的形式主义在2005年和2006年拍摄的LS I +61 303数据。我们发现LS I +61 303数据集是周期性的,周期为(26.8+-0.2)天(试验后机会概率为10^{-7}),接近轨道周期。

英文摘要:

The MAGIC collaboration has recently reported the discovery of gamma-ray emission from the binary system LS I +61 303 in the TeV energy region. Here we present new observational results on this source in the energy range between 300 GeV and 3 TeV. In total 112 hours of data were taken between September and December 2006 covering 4 orbital cycles of this object. This large amount of data allowed us to produce an integral flux light curve covering for the first time all orbital phases of LS I +61 303. In addition, we also obtained a differential energy spectrum for two orbital phase bins covering the phase range 0.5<phi<0.6 and 0.6<phi<0.7. The photon index in the two phase bins is consistent within the errors with an average index Gamma=2.6+-0.2_{stat}+-0.2_{sys}. LS I +61 303 was found to be variable at TeV energies on timescales of days. These new MAGIC measurements allowed us to search for intra-night variability of the VHE emission; however, no evidence for flux variability on timescales down to 30 minutes was found. To test for possible periodic structures in the light curve, we apply the formalism developed by Lomb and Scargle to the LS I +61 303 data taken in 2005 and 2006. We found the LS I +61 303 data set to be periodic with a period of (26.8+-0.2) days (with a post-trial chance probability of 10^{-7}), close to the orbital period.

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