During the September-October 2008 outburst of the accreting millisecond pulsar SAX J1808.4-3658, the source was observed by both Suzaku and XMM-Newton approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe K-alpha emission line which is present in both data-sets, as has recently been reported for other neutron star low-mass X-ray binaries. The properties of the Fe K line observed during each observation are very similar. From modeling the Fe line, we determine the inner accretion disk radius to be 13.2 +/- 2.5 GM/c^2. The inner disk radius measured from the Fe K line suggests that the accretion disk is not very receded in the island state. If the inner disk (as measured by the Fe line) is truncated at the magnetospheric radius this implies a magnetic field strength of ~3E8 G at the magnetic poles, consistent with other independent estimates.
The first discovered accreting millisecond pulsar, SAX J1808.4-3658, went into X-ray outburst in April 2015. We triggered a 100 ks XMM-Newton ToO, taken at the peak of the outburst, and a 55 ks NuSTAR ToO, performed four days apart. We report here the results of a detailed spectral analysis of both the XMM-Newton and NuSTAR spectra. While the XMM-Newton spectrum appears much softer than in previous observations, the NuSTAR spectrum confirms the results obtained with XMM-Newton during the 2008 outburst. We find clear evidence of a broad iron line that we interpret as produced by reflection from…
We report on the analysis of the AstroSat dataset of the accreting millisecond X-ray pulsar SAX J1808.4-3658, obtained during its 2019 outburst. We found coherent pulsations at $\sim 401$ Hz and an orbital solution consistent with previous studies. The 3-20 keV pulse profile can be well fitted with three harmonically related sinusoidal components with background-corrected fractional amplitude of $\sim 3.5 \%$, $\sim 1.2 \%$ and $\sim 0.37 \%$ for fundamental, second and third harmonic, respectively. Our energy-resolved pulse profile evolution study indicate a strong energy dependence. We also …
Broadband Timing and Spectral Study of Accreting Millisecond X-ray Pulsar SAX J1808.4$-$3658 during Its 2022 Outburst
Inter-University Centre for Astronomy and Astrophysics (IUCAA)（大学间天文学与天体物理学中心）；Universitá degli Studi di Cagliari（卡利亚里大学）；Department of Applied Sciences, UPES（印度石油大学应用科学系）
SAX J1748.9-2021 is a transiently accreting X-ray millisecond pulsar. It is also known as an X-ray burster source discovered by Beppo-SAX. We analysed the persistent emission and type-I X-ray burst properties during its 2015 outburst. The source varied from hard to soft state within half day. We modeled the broad-band spectra of the persistent emission in the 1 - 250 keV energy band for both spectral states using the quasi-simultaneous INTEGRAL and Swift data. The broad-band spectra are well fitted by an absorbed thermal Componization model, compps, in a slab geometry. The best-fits for the tw…
A clean broad iron line in GS 1354--64 as seen by XRISM
Institut für Astronomie und Astrophysik, Universität Tübingen（蒂宾根大学天文与天体物理研究所）；Nankai University（南开大学）；Cahill Center for Astronomy & Astrophysics, California Institute of Technology（加州理工学院卡希尔天文与天体物理学中心）；University of Warwick（华威大学）；Fudan University（复旦大学）；New Uzbekistan University（新乌兹别克斯坦大学）；Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）；Newcastle University（纽卡斯尔大学）；MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology（麻省理工学院卡弗里天体物理学与空间研究研究所）；Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理重点实验室）；University of Hertfordshire（赫特福德大学）；Institute of Space Sciences (ICE, CSIC)（空间科学研究所（加泰罗尼亚高等研究院））
Spectral Analysis of the 2019 and 2022 Outbursts of SAX J1808.4-3658
Montana State University（蒙大拿州立大学）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo（东京大学宇宙学前沿研究机构（WPI））；RTX（RTX公司）
Flux Dependence of the 1\,keV Soft X-ray Feature in SAX J1808.4-3658 with \textit{NICER}
Montana State University（蒙大拿州立大学）；University of Leicester（莱斯特大学）；Inter-University Centre for Astronomy and Astrophysics（大学间天体物理中心）；The University of Tokyo（东京大学）
Broad iron emission lines in Seyfert Galaxies - re-condensation of gas onto an inner disk below the ADAF
最近用Chandra、XMM-Newton和Suzaku对Seyfert 1活动星系核进行的观测显示出宽的铁K_α发射线，有些相对论性地模糊了。对于银河系黑洞的X射线双星XMM-牛顿光谱在硬态也揭示了相对论铁发射线和热分量的存在下，解释为一个弱的内部冷吸积盘热日冕下的指示。这些热成分被发现后，从软到硬的光谱状态的过渡，可以理解为持续的气体从对流为主的流（ADAF）到磁盘上的再冷凝。鉴于恒星质量和超大质量黑洞周围吸积流的相似性，我们讨论了Seyfert 1活动星系核中的宽铁发射线是否可以理解为来自类似的吸积流几何。在Miller（2007）和Nandra et al.（2007）的样本中，我们推导了具有强线的Seyfert星系的Eddington标度吸积率。在评估中，我们使用了观测到的X射线光度，热辐射校正和文献中的黑洞质量，大多数值来自Fabian和Vasudevan（2009）。超过一半的来源得出的速率小于爱丁顿速率的0.1。对于塞弗特1活动星系核中10^7到10^8个太阳质量的黑洞来说，这个极限相当于每年0.01到0.2个太阳质量。我们的研究表明，对于相当多的Seyfert活动星系核在硬谱态铁的发射线可以产生于一个内部弱盘周围的ADAF的再凝聚模型预测。一些具有较高吸积率的剩余源可能处于与LMXB的“非常高”状态相当的光谱状态。（节略）
Broad Iron Line as a Relativistic Reflection from Warm Corona in AGN
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文中心）；ESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité（巴黎天文台，PSL研究大学，法国国家科学研究中心，索邦大学，巴黎第六大学，巴黎第七大学，索邦巴黎城）；Research Center for Computational Physics and Data Processing, Institute of Physics, Silesian University in Opava（奥帕瓦西里西亚大学物理研究所计算物理与数据处理研究中心）
A sample of 22 narrow-line Seyfert 1 (NLS1) and 47 broad-line Seyfert 1 (BLS1) galaxies observed with Suzaku is used to examine the Fe K band properties of each group. Three different models are used to examine the presence of: narrow neutral Fe Ka line at 6.4 keV and ionised Fe xxv and Fe xxvi emission lines (model A); a broad emission feature at around 6 - 7 keV (model B); and an absorption edge at 7.1 keV (model C). In all three models, the neutral Fe Ka line is weaker (lower luminosity and equivalent width) in NLS1s than in BLS1s. Model (B) also finds a more significant broad component (la…
The Effects of Complex Accretion Disk Geometry on Broadened Iron K$α$ Lines
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；Stanford University（斯坦福大学）；Kavli Institute for Particle Astrophysics & Cosmology (KIPAC), Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）；The Ohio State University（俄亥俄州立大学）
We present results from the Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the new black hole X-ray binary candidate MAXI J1631-479 at two epochs during its 2018-2019 outburst, which caught the source in a disk dominant state and a power-law dominant state. Strong relativistic disk reflection features are clearly detected, displaying significant variations in the shape and strength of the broad iron emission line between the two states. Spectral modeling of the reflection spectra reveals that the inner radius of the optically-thick accretion disk evolves from $<1.9$ $r_{\rm g}$…
Polarised X-ray emission from the accreting millisecond pulsar SAX J1808.4-3658 during an X-ray outburst and a type-I X-ray burst
INAF Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；INAF Istituto di Astrofisica e Planetologia Spaziali（意大利国家天体物理研究所天体物理与空间行星学研究所）；INAF Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究所）
We present a spectral study of the ultraluminous Be/X-ray transient pulsar Swift J0243.6+6124 using Neutron Star Interior Composition Explorer (NICER) observations during the system's 2017--2018 giant outburst. The 1.2--10~keV energy spectrum of the source can be approximated with an absorbed cut-off power law model. We detect strong, luminosity-dependent emission lines in the 6--7 keV energy range. A narrow 6.42 keV line, observed in the sub-Eddington regime, is seen to evolve into a broad Fe-line profile in the super-Eddington regime. Other features are found at 6.67 and 6.97 keV in the Fe-l…
