标题： XTE J1946+274 = GRO J1944+26：一个神秘的Be/X射线双星系统 显示英文标题

标题： XTE J1946+274 = GRO J1944+26: An Enigmatic Be/X-ray Binary

摘要： XTE J1946+274 = GRO J1944+26 是一个15.8秒的Be/X射线脉冲星，于1998年9月同时由康普顿伽马射线天文台（CGRO）上的暴发和瞬态源实验（BATSE）以及罗西X射线时变探测器（RXTE）上的全天监视器（ASM）发现。 在这里我们展示了来自BATSE和{\em RXTE}的新结果，包括脉冲定时分析、光谱分析以及吸积盘存在的证据。 我们的脉冲定时分析得到了169.2天的轨道周期、中等偏心率0.33，并推导出质量函数为9.7 M_sun。 我们观察到了吸积盘存在的证据，测量到的自旋加速率与通量之间存在相关性，通过拟合该相关性获得了距离估计值为9.5 ± 2.9千秒差距。 XTE J1946+274从1998年9月至2001年7月一直处于活跃状态，经历了13次未锁定在轨道相位的爆发。 比较1998年首次明亮爆发和2001年最后两次爆发期间的RXTE PCA观测数据，我们发现在两次爆发中都存在能量和强度依赖的脉冲轮廓变化，并且在较微弱的2001年爆发中随着强度增加，光谱变硬。 在2001年7月，光学Hα观测表明当X射线爆发停止时，Be盘中出现了密度扰动。 我们认为在这个系统中，Be星的赤道平面相对于轨道平面倾斜，并且这种倾斜可能是该系统异常爆发行为的因素之一。 显示英文摘要

摘要： XTE J1946+274 = GRO J1944+26 is a 15.8 s Be/X-ray pulsar discovered simultaneously in 1998 September with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) and the All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE). Here we present new results from BATSE and {\em RXTE} including a pulse timing analysis, spectral analysis, and evidence for an accretion disk. Our pulse timing analysis yielded an orbital period of 169.2 days, a moderate eccentricity of 0.33, and implied a mass function of 9.7 M_sun. We observed evidence for an accretion disk, a correlation between measured spin-up rate and flux, which was fitted to obtain a distance estimate of 9.5 +/- 2.9 kpc. XTE J1946+274 remained active from 1998 September - 2001 July, undergoing 13 outbursts that were not locked in orbital phase. Comparing RXTE PCA observations from the initial bright outburst in 1998 and the last pair of outbursts in 2001, we found energy and intensity dependent pulse profile variations in both outbursts and hardening spectra with increasing intensity during the fainter 2001 outbursts. In 2001 July, optical Halpha observations indicate a density perturbation appeared in the Be disk as the X-ray outbursts ceased. We propose that the equatorial plane of the Be star is inclined with respect to the orbital plane in this system and that this inclination may be a factor in the unusual outburst behavior of the system.