论文标题
瞬态Pulsar GRO J2058+42的宽带X射线特性
Broadband X-ray characteristics of the transient pulsar GRO J2058+42
论文作者
论文摘要
BE X射线二进制GRO J2058+42最近在2019年3月至4月的II爆发中爆发了大约50天。该爆发被检测到所有Sky X射线显示器，例如Fermi-GBM，Swift-Bat和Maxi-GSC。还进行了两个Nustar观察，一个在崛起期间，另一个在爆发期间进行。它为我们提供了独特的机会，可以首次分析脉冲星的宽带特性，并在一系列X射线光度内进行脉冲星的吸积扭矩特性。脉冲曲线非常依赖能量，在低能（<20 keV）处至少有四个不同的脉冲成分，可在高能（> 30 keV）下演变为单峰曲线。在每个狭窄的能带中，在两个Nustar观测值中，脉冲曲线几乎相同。来自两个观测值的光谱非常适合具有费米 - 迪拉克型高能量截止的幂律。我们排除了脉冲相中的X射线光谱在Nustar带中的X射线光谱中的存在，其光学深度大于0.15。在两个nustar光谱中都检测到铁发射线，同等宽度约为125 eV。我们研究了旋转速率对亮度的依赖性，并估计了磁场强度，与其他已知的BEXRB脉冲星相比，磁场强度要高得多。最后，我们讨论了确定中子恒星磁场强度的扭矩亮度关系不足。
The Be X-ray binary GRO J2058+42 recently went through a Type-II outburst during March-April 2019 lasting for about 50 days. This outburst was detected with the operating all sky X-ray monitors like the Fermi-GBM, Swift-BAT and MAXI-GSC. Two NuSTAR observations were also made, one during the rise and other during the decay of the outburst. It gave us the unique opportunity to analyze the broadband characteristics of the pulsar for the first time and accretion torque characteristics of the pulsar over a range of X-ray luminosity. The pulse profiles are strongly energy dependent, with at least four different pulse components at low energy (< 20 keV) which evolves to a single-peaked profile at high energy (> 30 keV). In each of the narrow energy bands, the pulse profiles are nearly identical in the two NuSTAR observations. The spectra from both the observations are fitted well to a power-law with a Fermi-Dirac type high energy cutoff. We ruled out presence of a cyclotron line in the pulse phase averaged X-ray spectrum in the NuSTAR band with an optical depth greater than 0.15. An iron emission line is detected in both the NuSTAR spectra with an equivalent width of about 125 eV. We looked at the dependence of the spin-up rate on the luminosity and estimated the magnetic field strength from that, which came out to be much higher compared to other known BeXRB pulsars. Lastly, we discussed the inadequacy of the torque-luminosity relation for determination of magnetic field strength of neutron stars.
