发表机构
Università degli Studi di Palermo; Osservatorio Astronomico di Cagliari, Istituto nazionale di astrofisica; INAF – IASF Palermo; INAF – Osservatorio Astronomica di Brera（巴勒莫大学; 卡利亚里天文台，意大利国家天体物理研究所; 意大利国家天体物理研究所帕勒莫天文空间物理研究所; 意大利国家天体物理研究所布雷拉天文台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过XRISM和NuSTAR光谱分析4U 1624-490的轨道相位分辨吸收特征，推断其可能为中等质量X射线双星，伴星质量为2.66倍太阳质量。
AI 中文摘要
高倾角食双中子星X射线双星提供了吸积流结构的直接视图，因为视线截取了盘上方的电离等离子体。我们分析了两次XRISM/Resolve对4U 1624$-$490的观测，同时有NuSTAR覆盖，将数据分为七个轨道相位区间。相位分辨拟合包括中性部分覆盖、光电离吸收体、热康普顿化和电离盘反射。在大部分轨道上探测到Fe XXV和Fe XXVI吸收线。吸收体柱密度、电离状态、覆盖比例和投影速度随轨道相位变化，谱线系统性蓝移，视线速度约为$85$-$440\\ {\rm km\\,s^{-1}}$。仅吸收模型留下宽Fe-K残差，而电离反射改善了拟合。速度调制半振幅$K=210\pm14\\ {\rm km\\,s^{-1}}$，若解释为轨道运动，则质量函数$f(M)=0.83\pm0.17\\,M_\odot$。Fe XXVI蓝翼的残差结构暗示食附近额外的运动学复杂性，但排除两个食邻近测量后调制仍一致。若吸收体追踪中子星轨道运动，推断的伴星质量为$M_2=2.66\pm0.32\\,M_\odot$，与充满洛希瓣的B9 V-B9.5 V星兼容。在此解释下，4U 1624$-$490可能是中等质量而非经典低质量X射线双星。（摘要删节）
英文摘要
High-inclination dipping neutron-star X-ray binaries provide a direct view of accretion-flow structure because the line of sight intercepts ionised plasma above the disc. We analyse two XRISM/Resolve observations of 4U 1624$-$490 with simultaneous NuSTAR coverage, dividing the data into seven orbital-phase intervals. Phase-resolved fits include neutral partial covering, a photoionised absorber, thermal Comptonisation, and ionised disc reflection. Fe XXV and Fe XXVI absorption are detected over most of the orbit. The absorber column density, ionisation state, covering fraction, and projected velocity vary with orbital phase and the lines are systematically blueshifted, with line-of-sight velocities of about $85$-$440\ {\rm km\,s^{-1}}$. Absorption-only models leave broad Fe-K residuals, while ionised reflection improves the fits. The velocity modulation has a semi-amplitude $K=210\pm14\ {\rm km\,s^{-1}}$ and, if interpreted as orbital motion, implies a mass function $f(M)=0.83\pm0.17\,M_\odot$. Residual structure in the blue wing of Fe XXVI suggests additional kinematic complexity near the dip, but the modulation remains consistent when the two dip-adjacent measurements are excluded. If the absorber traces the neutron-star orbital motion, the inferred donor mass is $M_2=2.66\pm0.32\,M_\odot$, compatible with a Roche-lobe-filling B9 V-B9.5 V star. Under this interpretation, 4U 1624$-$490 may be an intermediate-mass rather than a classical low-mass X-ray binary. (Abridged abstract)
Comments17 pages, 9 figures, accepted for publication in A&A, Sect. 7: Stellar structure and evolution
