LSI +61303的长期OVRO监测：两个关闭周期的确认
Long-term OVRO monitoring of LSI+61303: confirmation of the two close periodicities
摘要：
背景：伽马射线双星LSI+61303显示出多个周期性。对6.7年的GBI射电数据和6年的Fermi-LAT GeV γ射线数据的时间分析都发现了两个相近的周期P1（GBI）= 26.49 \pm 0.07 d，P2（GBI）=26.92 \pm 0.07 d和P1（gamma）=26.48 \pm 0.08 d，P2（gamma）= 26.99 \pm 0.08 d。目的：系统LSI+61303是低能量和高能量下几个连续监测程序的对象。f1和f2之间的频率差仅为0.0006 d（-1），需要长期监测，因为时序分析中的频率分辨率与整个时间间隔的倒数有关。欧文斯谷射电天文台（OVRO）的40米望远镜已经在15千兆赫监测源五年，并与费米-LAT监测重叠。这项工作的目的是确定这两个频率是否也解决了OVRO监测。方法：我们用Lomb-Scargle方法分析OVRO数据。我们还更新了Fermi-LAT观测的时间分析。结果：OVRO数据的周期图证实了两个周期P1（OVRO）= 26.5 \pm 0.1 d和P2（OVRO）= 26.9 \pm 0.1 d。结论：用GBI、OVRO和Fermi-LAT观测对P1和P2进行的三次独立测量证实了周期性是LSI+61303系统的永久特征。当LSI+61303中的致密物体朝向apastron时，在高（GeV）和低（无线电）能量下的发射行为相似，这表明发射是由旋进（P2）喷流中相同的周期性（P1）喷射电子群引起的。
英文摘要：
Context: The gamma-ray binary LSI+61303 shows multiple periodicities. The timing analysis of 6.7 yr of GBI radio data and of 6 yr of Fermi-LAT GeV gamma-ray data both have found two close periodicities P1(GBI) = 26.49 \pm 0.07 d, P2(GBI)=26.92 \pm 0.07 d and P1(gamma)=26.48 \pm 0.08 d, P2(gamma) = 26.99 \pm 0.08 d. Aims: The system LSI+61303 is the object of several continuous monitoring programs at low and high energies. The frequency difference between f1 and f2 of only 0.0006 d(-1) requires long-term monitoring because the frequency resolution in timing analysis is related to the inverse of the overall time interval. The Owens Valley Radio Observatory (OVRO) 40 m telescope has been monitoring the source at 15 GHz for five years and overlaps with Fermi-LAT monitoring. The aim of this work is to establish whether the two frequencies are also resolved in the OVRO monitoring. Methods: We analysed OVRO data with the Lomb-Scargle method. We also updated the timing analysis of Fermi-LAT observations. Results: The periodograms of OVRO data confirm the two periodicities P1(OVRO) = 26.5 \pm 0.1 d and P2(OVRO) = 26.9 \pm 0.1 d. Conclusions: The three indipendent measurements of P1 and P2 with GBI, OVRO, and Fermi-LAT observations confirm that the periodicities are permanent features of the system LSI+61303. The similar behaviours of the emission at high (GeV) and low (radio) energy when the compact object in LSI+61303 is toward apastron suggest that the emission is caused by the same periodically (P1) ejected population of electrons in a precessing (P2) jet.
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