标题： LMC X-4 中子星双星的超轨道周期光谱特征 显示英文标题

标题： Spectroscopic Signatures of the Superorbital Period in the Neutron Star Binary LMC X-4

摘要： 我们展示了中子星双星系统LMC X-4中发射线随超轨道相位变化的首个高分辨率X射线研究。 我们的分析通过X射线光谱提供了新证据，确认了吸积盘进动是超轨道周期的起源。 通过钱德拉高能传输光栅光谱仪（HETGS）和XMM-Newton反射光栅光谱仪（RGS）获得的光谱包含多个发射特征，包括来自N、O、Ne和Fe的类氢和类氦物质的线、窄带O VII共振吸收线（RRC），以及来自冷Fe的荧光发射。 我们利用窄带RRC和He-alpha三重态来限制（光电离）气体的温度和密度。 通过比较不同超轨道相位的光谱，我们试图分离来自吸积盘和恒星风的线发射贡献。 还存在高度电离铁的红移和蓝移证据，约为25,000公里/秒。 我们认为这种发射起源于内吸积盘，并表明LMC X-4中的发射线特性是吸积盘进动的自然结果。 显示英文摘要

摘要： We present the first high-resolution X-ray study of emission line variability with superorbital phase in the neutron star binary LMC X-4. Our analysis provides new evidence from X-ray spectroscopy confirming accretion disk precession as the origin of the superorbital period. The spectra, obtained with the Chandra High-Energy Transmission Grating Spectrometer (HETGS) and the XMM-Newton Reflection Grating Spectrometer (RGS), contain a number of emission features, including lines from hydrogen-like and helium-like species of N, O, Ne, and Fe, a narrow O VII RRC, and fluorescent emission from cold Fe. We use the narrow RRC and the He-alpha triplets to constrain the temperature and density of the (photoionized) gas. By comparing spectra from different superorbital phases, we attempt to isolate the contributions to line emission from the accretion disk and the stellar wind. There is also evidence for highly ionized iron redshifted and blueshifted by ~25,000 km/s. We argue that this emission originates in the inner accretion disk, and show that the emission line properties in LMC X-4 are natural consequences of accretion disk precession.