Stars getting close enough to black holes(BHs)can be torn apart by strong tidal forces,producing electromagnetic flares.To date,more than 100 tidal disruption events(TDEs)have been observed,each involving invariably n...Stars getting close enough to black holes(BHs)can be torn apart by strong tidal forces,producing electromagnetic flares.To date,more than 100 tidal disruption events(TDEs)have been observed,each involving invariably normal gaseous stars whose debris falls onto the BH,sustaining the flares over years.White dwarfs(WDs),which are the most prevalent compact stars and a million times denser-and therefore tougher-than gaseous stars,can only be disrupted by intermediate-mass black holes(IMBHs)of 10^(2)–10^(5) solar masses.WD-TDEs are considered to generate more powerful and short-lived flares,but their evidence has been lacking.Here we report observations of a fast and luminous X-ray transient EP250702a detected by Einstein Probe.Its one-day-long X-ray peak as luminous as 10^(47−49) erg s^(−1) showed strong recurrent flares with hard spectra extending to several tens of MeV gamma-rays,as detected by Fermi/GBM and Konus-Wind,indicating relativistic jet emission.The jet's X-rays dropped sharply from 3×10^(49) erg s^(−1) to around 1044 erg s^(−1) within 20 days(10 days in the source rest frame).These characteristics are inconsistent with any previously known transient phenomena.We suggest that this fast-evolving event over the unprecedentedly short timescale arises likely from disruption of a WD by an IMBH.At late times,a soft component progressively dominates the X-ray spectrum,reaching a luminosity as high as 1044 erg s^(−1),which is consistent with being extreme super-Eddington emission from an accretion disk expected to form in an IMBH-WD TDE.WD-TDEs open a new window for investigating the elusive IMBHs and their surrounding stellar environments,and they are prime sources of gravitational waves in the band of space-based interferometers.展开更多
A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-d...A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-dimensional cusp boundary from a two-dimensional X-ray image because the detected X-ray signals will be integrated along the line of sight.In this work,a global magnetohydrodynamic code was used to simulate the X-ray images and photon count images,assuming an interplanetary magnetic field with a pure Bz component.The assumption of an elliptic cusp boundary at a given altitude was used to trace the equatorward and poleward boundaries of the cusp from a simulated X-ray image.The average discrepancy was less than 0.1 RE.To reduce the influence of instrument effects and cosmic X-ray backgrounds,image denoising was considered before applying the method above to SXI photon count images.The cusp boundaries were reasonably reconstructed from the noisy X-ray image.展开更多
“慧眼”硬X射线调制望远镜(简称慧眼卫星,英文名为Insight Hard X-ray Modulation Telescope,简称Insight-HXMT或HXMT),于2017年6月15日发射升空,标志着我国自主研发的首个天文台级X射线望远镜的诞生.慧眼卫星凭借其大面积、宽波段、...“慧眼”硬X射线调制望远镜(简称慧眼卫星,英文名为Insight Hard X-ray Modulation Telescope,简称Insight-HXMT或HXMT),于2017年6月15日发射升空,标志着我国自主研发的首个天文台级X射线望远镜的诞生.慧眼卫星凭借其大面积、宽波段、高时间分辨率和高能量分辨率的综合优势,为黑洞与中子星系统的硬X射线快速变化和宽波段能谱研究领域开辟了新的研究窗口.超出设计寿命的慧眼卫星已稳定运行超过8yr,目前状态良好,且有望进一步延长其在轨服务时间.截至2024年10月,慧眼卫星已7次向全球科学界公开征集观测提案,共收到334份有效的观测提案,并据此制定了2368个观测计划.此外,慧眼卫星已向公众发布数据13批次,累计数据量达到40 TB,数据公开比率高达94%.慧眼卫星还向用户提供了不同版本的数据分析软件和标定数据库,在轨标定精度在2%左右,满足科学分析的要求.来自全球17家及国内36家研究机构的学者使用慧眼数据开展了科学研究,发表了约300多篇高质量学术论文,累计引用次数约7300次.展开更多
中国空间站巡天望远镜(Chinese Space Survey Telescope,CSST)无缝光谱组件将安装在巡天模块主焦面探测器前面,用于开展大视场、宽波段的无缝光谱观测.无缝光谱组件作为巡天模块的重要色散元件,由24块光栅和12块滤光片拼接而成.光谱效...中国空间站巡天望远镜(Chinese Space Survey Telescope,CSST)无缝光谱组件将安装在巡天模块主焦面探测器前面,用于开展大视场、宽波段的无缝光谱观测.无缝光谱组件作为巡天模块的重要色散元件,由24块光栅和12块滤光片拼接而成.光谱效率是无缝光谱组件的重要技术指标之一,在研制过程中,需要对无缝光谱组件的光谱效率进行检测.由于无缝光谱组件外形包络较大,无法使用商业光谱效率测量设备进行检测.针对无缝光谱组件光谱效率测试的问题,首先介绍了实验室搭建的无缝光谱组件光谱效率检测装置的基本结构和测量原理,接着给出了无缝光谱组件鉴定件光谱效率测量的步骤和结果,最后利用误差合成理论分析并计算了测量结果的精度.测量和计算结果表明,无缝光谱组件鉴定件平均光谱效率分别为GU波段51.9%、GV波段67.9%、GI波段71.6%(其中900-1000 nm波段为67.7%),满足技术指标要求.展开更多
空间碎片高精度定轨、碰撞预警和清除等技术问题对高精度空间碎片测量数据提出了迫切需求。激光测距技术是目前精度最高的空间碎片观测手段,然而大部分空间碎片轨道预报精度差,降低了空间碎片测距的成功率。文中提出了一种基于时间偏差...空间碎片高精度定轨、碰撞预警和清除等技术问题对高精度空间碎片测量数据提出了迫切需求。激光测距技术是目前精度最高的空间碎片观测手段,然而大部分空间碎片轨道预报精度差,降低了空间碎片测距的成功率。文中提出了一种基于时间偏差修正的空间碎片轨道预报优化方法,旨在提高测距过程中对碎片的稳定跟踪能力,进而获得更多的观测数据。通过选取Starlette、Larets和Lares三颗精密定轨卫星,基于两行根数(Two Line Element,TLE)轨道时间偏差修正与SP3精密星历的对比验证了方法的有效性,三颗卫星的视位置偏差较初始值分别减少51.7%、76.0%和95.0%。进而提出把预报方位角俯仰角时间序列看作整体的时间偏差计算方法,实现了三颗卫星时间偏差的仿真计算。实验依托中国科学院云南天文台1.2 m望远镜实际跟踪TLE预报的大量空间碎片,从实验上分析文中提出方法的有效性。空间碎片观测实验结果为,方位角偏差的平均修正量为83.5%,俯仰角偏差的平均修正量为79.8%,时间偏差修正方法可大幅修正碎片预报位置偏差,该方法可为不可见空间碎片的跟踪提供技术支撑,提升激光测距系统全天时观测能力。展开更多
文摘Stars getting close enough to black holes(BHs)can be torn apart by strong tidal forces,producing electromagnetic flares.To date,more than 100 tidal disruption events(TDEs)have been observed,each involving invariably normal gaseous stars whose debris falls onto the BH,sustaining the flares over years.White dwarfs(WDs),which are the most prevalent compact stars and a million times denser-and therefore tougher-than gaseous stars,can only be disrupted by intermediate-mass black holes(IMBHs)of 10^(2)–10^(5) solar masses.WD-TDEs are considered to generate more powerful and short-lived flares,but their evidence has been lacking.Here we report observations of a fast and luminous X-ray transient EP250702a detected by Einstein Probe.Its one-day-long X-ray peak as luminous as 10^(47−49) erg s^(−1) showed strong recurrent flares with hard spectra extending to several tens of MeV gamma-rays,as detected by Fermi/GBM and Konus-Wind,indicating relativistic jet emission.The jet's X-rays dropped sharply from 3×10^(49) erg s^(−1) to around 1044 erg s^(−1) within 20 days(10 days in the source rest frame).These characteristics are inconsistent with any previously known transient phenomena.We suggest that this fast-evolving event over the unprecedentedly short timescale arises likely from disruption of a WD by an IMBH.At late times,a soft component progressively dominates the X-ray spectrum,reaching a luminosity as high as 1044 erg s^(−1),which is consistent with being extreme super-Eddington emission from an accretion disk expected to form in an IMBH-WD TDE.WD-TDEs open a new window for investigating the elusive IMBHs and their surrounding stellar environments,and they are prime sources of gravitational waves in the band of space-based interferometers.
基金funded by the National Natural Science Foundation of China(NNSFC)under Grant Numbers 42322408,42188101,and 42441809Additional support was provided by the Climbing Program of the National Space Science Center(NSSC,Grant No.E4PD3005)as well as the Specialized Research Fund for State Key Laboratories of China.
文摘A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-dimensional cusp boundary from a two-dimensional X-ray image because the detected X-ray signals will be integrated along the line of sight.In this work,a global magnetohydrodynamic code was used to simulate the X-ray images and photon count images,assuming an interplanetary magnetic field with a pure Bz component.The assumption of an elliptic cusp boundary at a given altitude was used to trace the equatorward and poleward boundaries of the cusp from a simulated X-ray image.The average discrepancy was less than 0.1 RE.To reduce the influence of instrument effects and cosmic X-ray backgrounds,image denoising was considered before applying the method above to SXI photon count images.The cusp boundaries were reasonably reconstructed from the noisy X-ray image.
文摘中国空间站巡天望远镜(Chinese Space Survey Telescope,CSST)无缝光谱组件将安装在巡天模块主焦面探测器前面,用于开展大视场、宽波段的无缝光谱观测.无缝光谱组件作为巡天模块的重要色散元件,由24块光栅和12块滤光片拼接而成.光谱效率是无缝光谱组件的重要技术指标之一,在研制过程中,需要对无缝光谱组件的光谱效率进行检测.由于无缝光谱组件外形包络较大,无法使用商业光谱效率测量设备进行检测.针对无缝光谱组件光谱效率测试的问题,首先介绍了实验室搭建的无缝光谱组件光谱效率检测装置的基本结构和测量原理,接着给出了无缝光谱组件鉴定件光谱效率测量的步骤和结果,最后利用误差合成理论分析并计算了测量结果的精度.测量和计算结果表明,无缝光谱组件鉴定件平均光谱效率分别为GU波段51.9%、GV波段67.9%、GI波段71.6%(其中900-1000 nm波段为67.7%),满足技术指标要求.
文摘空间碎片高精度定轨、碰撞预警和清除等技术问题对高精度空间碎片测量数据提出了迫切需求。激光测距技术是目前精度最高的空间碎片观测手段,然而大部分空间碎片轨道预报精度差,降低了空间碎片测距的成功率。文中提出了一种基于时间偏差修正的空间碎片轨道预报优化方法,旨在提高测距过程中对碎片的稳定跟踪能力,进而获得更多的观测数据。通过选取Starlette、Larets和Lares三颗精密定轨卫星,基于两行根数(Two Line Element,TLE)轨道时间偏差修正与SP3精密星历的对比验证了方法的有效性,三颗卫星的视位置偏差较初始值分别减少51.7%、76.0%和95.0%。进而提出把预报方位角俯仰角时间序列看作整体的时间偏差计算方法,实现了三颗卫星时间偏差的仿真计算。实验依托中国科学院云南天文台1.2 m望远镜实际跟踪TLE预报的大量空间碎片,从实验上分析文中提出方法的有效性。空间碎片观测实验结果为,方位角偏差的平均修正量为83.5%,俯仰角偏差的平均修正量为79.8%,时间偏差修正方法可大幅修正碎片预报位置偏差,该方法可为不可见空间碎片的跟踪提供技术支撑,提升激光测距系统全天时观测能力。
