Context: Cygnus X-1 is a black hole X-ray binary system in which the black hole captures and accretes gas from the strong stellar wind emitted by its supergiant O9.7 companion star. The irradiation of the supergiant star essentially determines the flow properties of the stellar wind and the X-ray luminosity from the system. The results of three-dimensional hydrodynamical simulations of wind-fed X-ray binary systems reported in recent work reveal that the ionizing feedback of the X-ray irradiation leads to the existence of two stable states with either a soft or a hard spectrum. Aims: We discuss the observed radiation of Cygnus X-1 in the soft and hard state in the context of mass flow in the corona and disk, as predicted by the recent application of a condensation model. Methods: The rates of gas condensation from the corona to the disk for Cygnus X-1 are determined, and the spectra of the hard and soft radiation are computed. The theoretical results are compared with the MAXI observations of Cygnus X-1 from 2009 to 2018. In particular, we evaluate the hardness-intensity diagrams (HIDs) for its ten episodes of soft and hard states which show that Cygnus X-1 is distinct in its spectral changes as compared to those found in the HIDs of low-mass X-ray binaries. Results: The theoretically derived values of photon counts and hardness are in approximate agreement with the observed data in the HID. However, the scatter in the diagram is not reproduced. Improved agreement could result from variations in the viscosity associated with clumping in the stellar wind and corresponding changes of the magnetic fields in the disk. The observed dipping events in the hard state may also contribute to the scatter and to a harder spectrum than predicted by the model.
Cygnus X-1 is one of the brightest X-ray sources observed and shows the X-ray intensity variations on time scales from milliseconds to months in both the soft and hard X-rays. The accretion onto the black hole is believed to be wind fed due to focused stellar wind from the binary companion HDE-226868. We aim to understand the physical mechanism responsible for the short timescale X-ray variability ($<$100 s) of the source in its Hard/Low state. We compute the 2D relativistic hydrodynamic simulation of the low angular momentum accretion flow with a time dependent outer boundary condition that r…
Black-hole binary (BHB) systems comprise a stellar-mass black hole and a closely orbiting companion star. Matter is transferred from the companion to the black hole, forming an accretion disk, corona and jet structures. The resulting release of gravitational energy leads to emission of X-rays. The radiation is affected by special/general relativistic effects, and can serve as a probe of the properties of the black hole and surrounding environment, if the accretion geometry is properly identified. Two competing models describe the disk-corona geometry for the hard spectral state of BHBs, based …
The Cygnus\,OB2 region, $\sim 3.5-5~\text{Myr}$ old, contains one of the most significant populations of massive stars of the Milky Way. Such stars substantially contribute to producing large scale soft ($<2~\text{keV}$) diffuse X-ray emission. We also detected hard ($>3~\text{keV}$) diffuse X-ray emission in the direction of the pulsar PSR\,J2032+4127. The torus-shaped emission spans a $\approx 3'\times 2'$ jet-like structure. It is spatially coincident with the Fermi $γ$-ray source 4FGL\,J2032.3+4127. We suggest that the hard diffuse X-ray emission is the pulsar wind nebula bearing the pulsa…
We execute a detailed spectral-timing study of Cygnus X-1 in the low/hard, intermediate and high/soft states with the Hard X-ray Modulation Telescope observations. The broad band energy spectra fit well with the "truncated disk model" with the inner boundary of the accretion disk stays within $\sim$10 \textit R$_{\rm g}$ and moves inward as the source softens. Through studying of PDS, rms and Fourier-frequency component resolved spectroscopy, we find that the X-ray variations are generated in two different regions for each state. We discover that the major role that contributes to the X-ray va…
Unchanged X-Ray Polarization During Accretion Dips in the Low Hard State of Cygnus X-1
Guangxi University（广西大学）；INAF Istituto di Astrofisica e Planetologia Spaziali（意大利国家天体物理研究所空间天体物理学和行星科学研究所）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）
The evolution of massive stars is influenced by the mass lost to stellar winds over their lifetimes. These winds limit the masses of the stellar remnants (such as black holes) that the stars ultimately produce. We use radio astrometry to refine the distance to the black hole X-ray binary Cygnus X-1, which we find to be $2.22^{+0.18}_{-0.17}$ kiloparsecs. When combined with previous optical data, this implies a black hole mass of $21.2\pm2.2$ solar masses, higher than previous measurements. The formation of such a high-mass black hole in a high-metallicity system constrains wind mass loss from …
Recent observations of the high-mass X-ray binary Cygnus X-1 have shown that both the companion star (41 solar masses) and the black hole (21 solar masses) are more massive than previously estimated. Furthermore, the black hole appears to be nearly maximally spinning. Here we present a possible formation channel for the Cygnus X-1 system that matches the observed system properties. In this formation channel, we find that the orbital parameters of Cygnus X-1, combined with the observed metallicity of the companion, imply a significant reduction in mass loss through winds relative to commonly us…
Recent observations of AdLIGO and Virgo have shown that the spin measurements in binary black hole (BH) systems are typically small, which is consistent with the predictions by the classical isolated binary evolution channel. In this standard formation channel, the progenitor of the first-born BH is assumed to have efficient angular momentum transport. The BH spins in high-mass X-ray binaries (HMXBs), however, have been found consistently to be extremely high. In order to explain the high BH spins, the inefficient angular momentum transport inside the BH progenitor is required. This requiremen…
We report the detection of a short-lived narrow quasi-periodic oscillation (QPO) at ~88 mHz in an Insight-HXMT observation during the soft state of the persistent black hole high mass X-ray binary Cygnus X-1. This QPO is significantly detected in all the three instruments of Insight-HXMT, so in the broad energy range 1-250 keV. The fractional rms of the QPO does not show significant variations above 3 keV (~5%) while decreases at lower energy (~2%). We show that this QPO is different from the type-A, -B, and -C QPOs usually observed in black hole X-ray binaries. We compare QPOs at similar freq…
The Cygnus X-1 Puzzle: Implications of X-ray Polarization Measurements in the Soft and Hard States on the Properties of the Accretion Flow and the Emission Mechanisms
本文总结了 Cyg X-1 吸积流的关键观测约束，提出以约半光速远离吸积盘运动的正电子对层模型，解释了软硬态下的 X 射线高线性偏振及幂律辐射机制，并强调硬态几何结构仍受等离子体过程强烈影响。
Thanks to recurrent observations of the black hole binary Cyg X-1 carried out over 15 years the INTEGRAL satellite has collected the largest data set in the hard X-ray band for this source. We have analyzed these data, complemented by data collected by other X-ray satellites and radio flux at 15 GHz. To characterize the spectral and variability properties of the system we have examined parameters such as the hard X-ray flux, photon index and fractional variability. Our main result is that the 2D distribution of the photon index and flux determined for the 22-100 keV band forms six clusters. Th…
We analyse the aperiodic flaring features, also known as shots, observed in Cyg X-1 in the 0.1-80 keV energy band using a 6.39 ks simultaneous observation with AstroSat and NICER. We detect 49 simultaneous shots in the soft and hard X-ray bands with NICER and AstroSat-LAXPC, respectively. We observe the shot profile for the first time in soft X-rays (0.1-3 keV), which shows a spectral peak at $\sim$2 keV. Using time-averaged spectroscopy, we measured the truncation of the inner accretion disk at $6.7\pm0.2$ gravitational radii. The shot-phase resolved spectroscopy allowed us to identify the or…
In Supergiant X-ray binaries (SgXB), a compact object captures a fraction of the wind of an O/B supergiant on a close orbit. Proxies exist to evaluate the efficiency of mass and angular momentum accretion but they depend so dramatically on the wind speed that given the current uncertainties, they only set loose constrains. Furthermore, they often bypass the impact of orbital and shock effects on the flow structure. We study the wind dynamics and the angular momentum gained as the flow is accreted. We identify the conditions for the formation of a disc-like structure around the accretor and the…
State-Dependent X-ray Variability in Cygnus X-1: A 12-Year NuSTAR Timing Study of Accretion Flow Geometry
Boston University（波士顿大学）；Raman Research Institute（拉曼研究所）；Indian Institute of Science Education and Research Bhopal（印度科学教育与研究学院博帕尔分校）；Florida International University（佛罗里达国际大学）；Miami Dade College（迈阿密戴德学院）；Osmania University（奥斯曼尼亚大学）；Physical Research Laboratory（物理研究实验室）；UN Center for Space Science and Technology Education in Asia and Pacific (CSSTEAP)（联合国亚洲及太平洋空间技术和外空活动教育训练中心）；Sardar Vallabhbhai National Institute of Technology, Surat（萨达尔·瓦拉巴伊国立技术学院苏拉特分校）；Pondicherry University（本地治里大学）；School of Sciences, JAIN (Deemed-to-be University), Bengaluru（JAIN（视为大学）班加罗尔理学院）；Janusz Gil Institute of Astronomy, University of Zielona Góra（绿山大学扬努什·吉尔天文学研究所）
Chandra X-Ray Spectroscopy of the Focused Wind in the Cygnus X-1 System. II. The Nondip Spectrum in the Low/Hard State - Modulations with Orbital Phase
From GeV to PeV: Orbital Modulation and Wind-Regulated Ultrahigh-energy Emission in Cygnus~X-3
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（教育部现代天文学和天体物理学重点实验室（南京大学））；Tianfu Cosmic Ray Research Center（天府宇宙线研究中心）；State 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国家重点实验室）
OB-associations and superbubbles being energetically essential galactic powerhouses are likely to be the important acceleration sites of galactic cosmic rays (CRs). The emission profile of gamma-ray sources related to superbubbles and stellar clusters indicates on continuous particle acceleration by winds of massive stars. One of the most luminous galactic gamma-ray sources is Cygnus Cocoon superbubble, observed by multiple instruments, such as Fermi-LAT, ARGO, and, recently, HAWC. We discuss a model of particle acceleration and transport in a superbubble to explain GeV-TeV gamma-ray spectrum …
A cooler look at the environment of Cygnus X-1: Searching for dynamical interactions within cold molecular gas
University of Lethbridge（莱斯布里奇大学）；Universitat de Barcelona (ICCUB)（巴塞罗那大学宇宙科学研究所）；Curtin University（科廷大学）；New York University Abu Dhabi（纽约大学阿布扎比分校）；Istituto Nazionale di Astrofisica（意大利国家天体物理研究所）；Università degli Studi di Milano Bicocca（米兰比可卡大学）；ASTRON, Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；Radboud University（拉德堡德大学）
We present the first X-ray reverberation mass measurement of a stellar-mass black hole. Accreting stellar-mass and supermassive black holes display characteristic spectral features resulting from reprocessing of hard X-rays by the accretion disc, such as an Fe K$α$ line and a Compton hump. This emission probes of the innermost region of the accretion disc through general relativistic distortions to the line profile. However, these spectral distortions are insensitive to black hole mass, since they depend on disc geometry in units of gravitational radii. Measuring the reverberation lag resultin…
Institutt for fysikk, NTNU, Trondheim, Norway（挪威特隆赫姆挪威科技大学物理系）；Department of Physics, School of Natural Sciences, Technical University Munich, Germany（德国慕尼黑工业大学自然科学学院物理系）
We present a new analysis of NuSTAR and Suzaku observations of the black hole Cygnus X-1 in the intermediate state. The analysis uses kerrC, a new model for analyzing spectral and spectropolarimetric X-ray observations of black holes. kerrC builds on a large library of simulated black holes in X-ray binaries. The model accounts for the X-ray emission from a geometrically thin, optically thick accretion disk, the propagation of the X-rays through the curved black hole spacetime, the reflection off the accretion disk, and the Comptonization of photons in coronae of different 3-D shapes and physi…
We present an analysis of three Chandra High Energy Transmission Gratings observations of the black hole binary Cyg X-1/HDE 226868 at different orbital phases. The stellar wind that is powering the accretion in this system is characterized by temperature and density inhomogeneities including structures, or "clumps", of colder, more dense material embedded in the photoionized gas. As these clumps pass our line of sight, absorption dips appear in the light curve. We characterize the properties of the clumps through spectral changes during various dip stages. Comparing the silicon and sulfur abso…
Highly Ionized Fe-K Absorption Line from Cygnus X-1 in the High/Soft State Observed with Suzaku
2011年10月5日，在高/软状态期间，我们在朱雀观测的天鹅座黑洞X-1的高级会合附近观测到了一条瞬态类He Fe K α吸收线，这使我们能够首次绘制出从幕式吸积现象或下降开始和结束的完整演化。我们在事件中的X射线光谱模型，并跟踪其演变。吸收线在观测的前半部分相当弱，但在~10 ks时立即加深，之后减弱。等效宽度的总体变化是~3的因子，在~0.08的轨道相位处达到峰值。这是为黑洞提供能量的伴星风是星云的证据。通过分析与Voigt配置文件的线，它被发现是符合轻微红移的Fe XXV过渡，或可能是几个物种的混合物比Fe XXV少电离。这些数据可以用一个距离约为10^（10-12）cm、密度约为10^（（-13）-（-11））g cm^-3的团块来解释，该团块吸积到黑洞上，并/或通过视线到达黑洞，导致观测到的电离度瞬间下降和/或吸积物质密度增加。通过未来的X射线量热计任务（如ASTRO-H和AXSIO）继续监测个别事件，将使我们能够详细绘制出吸积环境及其在各种吸积状态之间的变化。
The radiatively driven wind of the primary star in wind-fed X-ray binaries can be suppressed by the X-ray irradiation of the compact secondary star. This causes feedback between the wind and the X-ray luminosity of the compact star. We estimated how the wind velocity on the face-on side of the donor star depends on the spectral state of the high-mass X-ray binary Cygnus X-3. We modeled the supersonic part of the wind by computing the line force (force multiplier) with the Castor, Abbott and Klein formalism and XSTAR physics and by solving the mass conservation and momentum balance equations. W…
We present a large-scale study of diffuse X-ray emission in the nearby massive stellar association Cygnus OB2 as part of the Chandra Cygnus OB2 Legacy Program. We used 40 Chandra X-ray ACIS-I observations covering $\sim$1.0 deg$^2$. After removing 7924 point-like sources detected in our survey, background-corrected X-ray emission, the adaptive smoothing reveals large-scale diffuse X-ray emission. Diffuse emission was detected in the sub-bands Soft [0.5 : 1.2] and Medium [1.2 : 2.5], and marginally in the Hard [2.5 : 7.0] keV band. From X-ray spectral analysis of stacked spectra we compute a to…
Cygnus X-3 is a unique microquasar in the Galaxy hosting a Wolf-Rayet companion orbiting a compact object that most likely is a low-mass black hole. The unique source properties are likely due to the interaction of the compact object with the heavy stellar wind of the companion. In this paper, we concentrate on a very specific period of time prior to the massive outbursts observed from the source. During this period, Cygnus X-3 is in a so-called hypersoft state, where the radio and hard X-ray fluxes are found to be at their lowest values (or non-detected), the soft X-ray flux is at its highest…
Neutron stars in low mass X-ray binaries are hypothesised to emit continuous gravitational waves that may be detectable by ground-based observatories. The torque balance model predicts that a higher accretion rate produces larger-amplitude gravitational waves, hence low mass X-ray binaries with high X-ray flux are promising targets for gravitational wave searches. The detection of X-ray pulsations would identify the spin frequency of these neutron stars, and thereby improve the sensitivity of continuous gravitational-wave searches by reducing the volume of the search parameter space. We perfor…
XRISM High-Resolution X-ray Spectroscopy of Cygnus X-1 -- Orbital and Short-Term Variability of Iron Absorption
Tokyo University of Science（东京科学大学）；Rikkyo University（立教大学）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；SRON Netherlands Institute for Space Research（荷兰空间研究所）；California Institute of Technology（加州理工学院）；University of Michigan（密歇根大学）；Massachusetts Institute of Technology（麻省理工学院）；Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA)（日本宇宙航空研究开发机构宇宙科学研究所）
