EXO 0748–676 is a well-studied, high-inclination, dipping and eclipsing neutron star low-mass X-ray binary that has recently emerged from 16 yr of quiescence into a new outburst. We present results from 55.5 ks of XMM-Newton observation, focusing on high-resolution spectroscopy with the same instrument (the Reflection Grating Spectrometer) that produced significant insights during the previous outburst. The XMM-Newton European Photon Imaging Camera light curve reveals a type I X-ray burst that leads to a corresponding optical burst by 3 s. To understand the effects of the burst on the ionization structure, the data are divided into burstless and pre- and postburst spectra, with additional analysis for dip and nondip phases. The primary spectral feature in all phases is a broad O vii recombination line, accompanied by velocity-broadened O viii, N vii, and Ne ix lines. Notably, the Ne ix line shows different ionization states for the preburst (11.65 Å) and postburst (13.56 Å) phases, while the dips also substantially affect the spectral lines. The current outburst mirrors many traits from the earlier one, such as a similar spectral state, plasma components with similar ionization structure, and spectral features from the same elements, implying a stable long-term accretion behavior across outbursts.

中文翻译：

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EXO 0748–676 从长时间静止中重新出现后的 XMM-Newton 高分辨率光谱


EXO 0748-676 是一个经过充分研究的、高倾角、倾角和黯然失色的中子星低质量 X 射线双星，它最近从 16 年的静止状态中脱颖而出，进入了新的爆发期。我们展示了 55.5 ks 的 XMM-Newton 观测结果，重点是使用在上次爆发期间产生重要见解的同一仪器（反射光栅光谱仪）进行高分辨率光谱学。XMM-Newton 欧洲光子成像相机的光线曲线显示了 I 型 X 射线暴，该 X 射线暴导致相应的光暴 3 秒。为了了解突发对电离结构的影响，将数据分为无突发以及突发前和后突发光谱，并对浸入和非浸入相进行额外分析。所有相中的主要谱特征是一条宽的 O vii 复合线，并伴有速度展宽的 O viii、N vii 和 Ne ix 线。值得注意的是，Ne ix 线显示了预爆发 （11.65 Å） 和后突 （13.56 Å） 阶段的不同电离态，而下降也对谱线产生重大影响。当前的爆发反映了前一次爆发的许多特征，例如相似的光谱状态、具有相似电离结构的等离子体成分以及来自相同元素的光谱特征，这意味着在爆发中具有稳定的长期吸积行为。