标题： 软γ射线脉冲星PSR B1509-58的敏捷观测 显示英文标题

标题： Agile Observations of the "Soft" Gamma-Ray Pulsar PSR B1509-58

摘要： 我们展示了PSR B1509-58的新“敏捷”（Agile）观测结果，这些结果是在使用当前数据集的一部分检测到信号后，在2.5年的时间内完成的。 30 MeV以上光变曲线的调制显著性达到了5$\sigma$置信水平，并且光变曲线与早期Comptel在30 MeV以下发现的结果相似：一个宽且不对称的第一个峰值，在射电峰值之后0.39 ± 0.02个周期达到最大值，加上第二个峰值位于0.94 ± 0.03。 Comptel和“敏捷”探测到的脉冲伽马射线流量的光谱能量分布可以用一个幂律（光子指数α=1.87±0.09）很好地描述，并且在E_c=81 ± 20 MeV处有一个显著的截止点，这是迄今为止在γ射线脉冲星中观察到的最软的光谱。 假设距离为5.2千秒差距，脉冲星在E > 1 MeV的能量上的发光度为$L_{\gamma}=4.2^{+0.5}_{-0.2} \times10^{35}$erg/s，这意味着向伽马射线转换的自旋下降效率为$\sim 0.03$。 PSR B1509-58谱中的异常柔软断点被解释为极地帽模型框架下的奇异光子分裂过程的标志，这种过程发生在该脉冲星的强大磁场中。 在这种解释下，我们的光谱限制了辐射点的高度在中子星表面以上3公里，这表明由于在磁层某些区域，当磁场变得太弱而无法维持光子分裂时，成对产生可以替代光子分裂，因此衰减可能不像以前认为的那样强烈。 在外间隙情景或者双极透镜模型的情况下，为了确定模型所需的条件是否与“敏捷”光变曲线和光谱匹配，从而符合偏振测量结果，还需要从射电波段获得更好的辐射几何约束。 显示英文摘要

摘要： We present the results of new Agile observations of PSR B1509-58 performed over a period of 2.5 years following the detection obtained with a subset of the present data. The modulation significance of the lightcurve above 30 MeV is at a 5$\sigma$ confidence level and the lightcurve is similar to those found earlier by Comptel up to 30 MeV: a broad asymmetric first peak reaching its maximum 0.39 +/- 0.02 cycles after the radio peak plus a second peak at 0.94 +/- 0.03. The gamma-ray spectral energy distribution of the pulsed flux detected by Comptel and Agile is well described by a power-law (photon index alpha=1.87+/-0.09) with a remarkable cutoff at E_c=81 +/- 20 MeV, representing the softest spectrum observed among gamma-ray pulsars so far. The pulsar luminosity at E > 1 MeV is $L_{\gamma}=4.2^{+0.5}_{-0.2} \times10^{35}$ erg/s, assuming a distance of 5.2 kpc, which implies a spin-down conversion efficiency to gamma-rays of $\sim 0.03$. The unusual soft break in the spectrum of PSR B1509-58 has been interpreted in the framework of polar cap models as a signature of the exotic photon splitting process in the strong magnetic field of this pulsar. In this interpretation our spectrum constrains the magnetic altitude of the emission point(s) at 3 km above the neutron star surface, implying that the attenuation may not be as strong as formerly suggested because pair production can substitute photon splitting in regions of the magnetosphere where the magnetic field becomes too low to sustain photon splitting. In the case of an outer-gap scenario, or the two pole caustic model, better constraints on the geometry of the emission would be needed from the radio band in order to establish whether the conditions required by the models to reproduce Agile lightcurves and spectra match the polarization measurements.