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arXiv 2301.12697astro-ph.HE
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NGC ~6341中PSR ~ J1717 +4308 A的gamma-ray脉动的可能探测及球状星团中gamma-ray毫秒脉动的意义

Likely detection of gamma-ray pulsations of PSR~J1717+4308A in NGC~6341 and implication of the gamma-ray millisecond pulsars in globular clusters

P. Zhang, Y. Xing, Z. Wang, W. Wu, Z. Chen

摘要:

本文报道了对球状星团NGC~6341(M92)的分析结果,该球状星团中最近发现了一颗毫秒脉冲星J1717 $+$ 4308 A。使用的数据来自{ \it费米伽马射线太空望远镜(费米)}上的大面积望远镜。我们在$4.4σ$置信水平下检测MSP的$γ$射线脉动(相应的加权H检验值为$\sim$ 28.4)。这颗MSP是在GC中发现的第四颗$γ$射线脉冲星,没有明显的脉冲外发射,其$γ$射线光度和效率分别为$1.3\times10^{34}$,erg,s $^{-1}$和1.7%.为了更清楚地了解已知GCPDMATHABMO射线MSP的性质,我们重新分析了其他三个的\fermi \ LAT数据。这四种MSP共享具有高$\dot{E}$($\sim 10^{36}$ \,erg\,s $^{-1}$)或在仅包含有限数量的已知MSP的GC中的特性。另外,我们还发现NGC~6624和NGC~6626中的PSR ~J1823 $-$ 3021 A和PSR ~ B1821 $-$ 24具有可探测的脉冲外$γ$射线发射,而NGC~6652中的PSR ~ J1835 $-$ 3259 B则没有。使用所获得的关断脉冲光谱或光谱上限,我们约束在四个GC中的其他MSP的数量。结果与文献报道的射电望远镜数目一致。虽然至少在NGC~6624和NGC~6626中,其他MSP对其观测到的PDMATHAMO射线发射的贡献不可忽略,但我们的研究表明,明亮MSP的存在可能是决定GC是否在PDMATHAMO射线下可检测的主要因素。

英文摘要:

We report our analysis results for the globular cluster (GC) NGC~6341 (M92), as a millisecond pulsar (MSP) J1717$+$4308A has recently been reported found in this GC. The data used are from the Large Area Telescope onboard the {\it Fermi Gamma-ray Space Telescope (Fermi)}. We detect $γ$-ray pulsations of the MSP at a $4.4σ$ confidence level (the corresponding weighted H-test value is $\sim$28.4). This MSP, the fourth $γ$-ray pulsar found in a GC, does not have significant off-pulse emission and has $γ$-ray luminosity and efficiency $1.3\times10^{34}$\,erg\,s$^{-1}$ and 1.7\% respectively. In order to have a clear view on the properties of the known GC $γ$-ray MSPs, we re-analyze the \fermi\ LAT data for the other three ones. These four MSPs share the properties of either having high $\dot{E}$ ($\sim 10^{36}$\,erg\,s$^{-1}$) or being in the GCs that contain only limited numbers of known MSPs. In addition, we find that PSRs~J1823$-$3021A and B1821$-$24, in NGC~6624 and NGC~6626 respectively, have detectable off-pulse $γ$-ray emission and PSR J1835$-$3259B in NGC~6652 does not. Using the obtained off-pulse spectra or spectral upper limits, we constrain the numbers of other MSPs in the four GCs. The results are consistent with the numbers of the radio pulsars reported in them. While at least in NGC~6624 and NGC~6626, the contribution of other MSPs to their observed $γ$-ray emission can not be ignored, our study indicates that the presence of a bright MSP could be the dominant factor for whether a GC is detectable at $γ$-rays or not.

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