Optical spectroscopy of the quiescent counterpart to EXO???0748???676
Optical spectroscopy of the quiescent counterpart to EXO???0748???676
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EXO 静态对应物的光谱？？？0748???676
DOI：
10.1111/j.1365-2966.2009.15395.x
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发表时间：
2009
影响因子：
4.8
通讯作者：
Bassa C
中科院分区：
文献类型：
--
作者：
Bassa C
我们展示了中子星 X 射线双星 EXO 0748−676 在 2008 年秋季源返回静止状态后的相分辨光谱和 X 射线计时。X 射线光曲线显示日食在轨道周期、轨道相位和持续时间上与返回静止之前的预测和测量一致。 Hα 和 Heiemission 线出现在光谱中，并显示了双星伴星轨道的特征，对径向速度半振幅 K2> 405 km s−1 的径向速度半振幅设置了下限。连续谱中的通量和发射线都显示出轨道调制，表明我们观察到被中子星辐射的双星伴星的半球。这种辐射的影响妨碍了对双星伴星的径向速度半振幅的直接测量；事实上，光谱中没有看到恒星的吸收线。尽管如此，我们的观测对中子星质量设定了严格的下限：M1>1.27 M⊙。对于标准中子星质量 M1= 1.4 M⊙，质量比限制为 0.075 <q< 0.105。
We present phase resolved optical spectroscopy and X-ray timing of the neutron star X-ray binary EXO 0748−676 after the source returned to quiescence in the autumn of 2008. The X-ray light curve displays eclipses consistent in orbital period, orbital phase and duration with the predictions and measurements before the return to quiescence. Hα and Heiemission lines are present in the optical spectra and show the signature of the orbit of the binary companion, placing a lower limit on the radial velocity semi-amplitude ofK2> 405 km s−1. Both the flux in the continuum and the emission lines show orbital modulations, indicating that we observe the hemisphere of the binary companion that is being irradiated by the neutron star. Effects due to this irradiation preclude a direct measurement of the radial velocity semi-amplitude of the binary companion; in fact, no stellar absorption lines are seen in the spectrum. Nevertheless, our observations place a stringent lower limit on the neutron star mass ofM1> 1.27 M⊙. For the canonical neutron star mass ofM1= 1.4 M⊙, the mass ratio is constrained to 0.075 <q< 0.105.