AX J1745.6-2901 is an eclipsing low mass X-ray binary (LMXB) in the Galactic Centre (GC). It shows significant X-ray excess emission during the eclipse phase, and its eclipse light curve shows an asymmetric shape. We use archival XMM-Newton and Chandra observations to study the origin of these peculiar X-ray eclipsing phenomena. We find that the shape of the observed X-ray eclipse light curves depends on both photon energy and the shape of the source extraction region, and also shows differences between the two instruments. By performing detailed simulations for the time-dependent X-ray dust scattering halo, as well as directly modelling the observed eclipse and non-eclipse halo profiles of AX J1745.6-2901, we obtained solid evidence that its peculiar eclipse phenomena are indeed caused by the X-ray dust scattering in multiple foreground dust layers along the line-of-sight (LOS). The apparent dependence on the instruments is caused by different instrumental point-spread-functions. Our results can be used to assess the influence of dust scattering in other eclipsing X-ray sources, and raise the importance of considering the timing effects of dust scattering halo when studying the variability of other X-ray sources in the GC, such as Sgr A*. Moreover, our study of halo eclipse reinforces the existence of a dust layer local to AX J1745.6-2901 as reported by Jin et al. (2017), as well as identifying another dust layer within a few hundred parsecs to Earth, containing up to several tens of percent LOS dust, which is likely to be associated with the molecular clouds in the Solar neighbourhood. The remaining LOS dust is likely to be associated with the molecular clouds located in the Galactic disk in-between.
Swift J174540.7-290015: a new accreting binary in the Galactic Center
我们报告的新的银河系中心（GC）的瞬态斯威夫特J174540.7-290015作为一个可能的低质量X射线双星（LMXB）位于只有16角秒从Sgr A* 的识别。在2016年2月6日的Swift GC监测期间检测到这种瞬变，它显示出与硬到软状态转变兼容的长期光谱变化。我们在2月26日用XMM-牛顿观测了35 ks的场，检测到软态的源，其特征是低水平的可变性和具有高能量尾部的软X射线热谱（通过INTEGRAL检测到高达~50 keV），典型的吸积中子星或黑洞。我们观察到：i）中性吸收物质的高柱密度，表明斯威夫特J174540.7-290015位于GC附近或之外; ii）亚太阳铁丰度，因此我们认为铁耗尽成尘埃颗粒。没有探测到FeK吸收线、蚀或倾斜，表明吸积盘是在低倾角下观测到的。无线电（VLA）观测没有发现任何与斯威夫特J174540.7-290015对应的无线电。用MPG/ESO La Silla 2.2米望远镜的GROND和VLT/NaCo在爆发前后的近红外波段也观测到了瞬变的位置。在钱德拉误差区域内，我们发现多个对象没有显示出显著的变化。
Ne and Fe abundances in the ISM: Archival Study of Fe-L and Ne-K edges in Chandra and XMM-Newton
University of Michigan（密歇根大学）；European Space Agency, European Space Research and Technology Center（欧洲空间局，欧洲空间研究与技术中心）；Rochester Institute of Technology（罗切斯特理工学院）
The January 2016 eruption of recurrent nova LMC 1968
我们对大麦云星云中的食周期性新星LMC 1968的所有观测结果进行了全面的回顾，这些观测结果以前曾在1968年，1990年，2002年，2010年以及最近的2016年在喷发中观测到。我们得到了一个可能的复发时间为$6.2 \pm 1.2$年，并提供了星历的日食。在紫外-光学-红外测光中，光变曲线从喷发后两天左右的第一次观察起就显示出高度的可变性。因此，无法证实颜色变化。2016年和1990年的爆发光谱非常相似，主要是由H和He线向2000埃方向延伸。发现星际红化为E（B-V）= $0.07\pm0.01$。超软X射线光度低于爱丁顿光度，X射线光谱表明WD的质量大于1.3 M $_\odot$。光变曲线的弯曲表明该系统处于高轨道倾角。在喷发后的第四天，在Fe II紫外吸收线中观察到了复合波。在第6天之后看到了窄线成分，并解释为是由于前一次喷发的喷出物再电离。紫外光谱随轨道相位而变化，特别是He II 1640埃发射线的一个组成部分，这使我们提出，早期的内部WD罗氏瓣可能充满了约束不透明介质之前，重新形成的吸积盘。这种介质和喷出物都可以导致软X射线源出现的延迟。
XRISM spectroscopy of a crowded Galactic center region -- I. Disentangling the sources in the field of view
Ehime University（爱媛大学）；Kyoto University（京都大学）；Columbia University（哥伦比亚大学）；Shizuoka University（静冈大学）；Nara University of Education（奈良教育大学）；NASA/Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；Center for Research and Exploration in Space Science and Technology, NASA/GSFC (CRESST II)（NASA/GSFC空间科学与技术探索研究中心（CRESST II））；University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校）
