Ultraluminous X-ray sources as super-Eddington accretion disks
Sergei Fabrika, Alexander Vinokurov, Kirill Atapin
备注:
5 pages, 3 figures, to appear in the Proceedings of the "14th Marcel Grossmann Meeting" (Rome, July 12 - 18, 2015). Comments on optical spectra have been added
The origin of Ultraluminous X-ray sources (ULXs) in external galaxies whose X-ray luminosities exceed those of the brightest black holes in our Galaxy by hundreds and thousands of times is mysterious. The most popular models for the ULXs involve either intermediate mass black holes (IMBHs) or stellar-mass black holes accreting at super-Eddington rates. Here we review the ULX properties, their X-ray spectra indicate a presence of hot winds in their accretion disks supposing the supercritical accretion. However, the strongest evidences come from optical spectroscopy. The spectra of the ULX counterparts are very similar to that of SS 433, the only known supercritical accretor in our Galaxy.
X-ray Outflows and Super-Eddington Accretion in the Ultraluminous X-ray Source Holmberg IX X-1
对X射线连续谱发射和通量变化的研究还没有最终揭示在分布的高亮度端(Lx > 1 e40 erg/s)的超亮X射线源(ULX)的性质。这些都是特别感兴趣的,因为光度需要超级爱丁顿吸积到一个质量约10 Msun的黑洞,或更多的标准吸积到一个中等质量的黑洞。超级爱丁顿吸积模型预测了强烈的外流风,使原子吸收线成为极端ULX性质的关键诊断。为了寻找这样的功能,我们已经进行了长期的,500公里的观测活动Holmberg IX X-1与朱雀。这是迄今为止,对于明亮的孤立ULX,铁K带通中最敏感的数据集,但我们在发射或吸收中没有发现统计上显著的原子特征;任何未检测到的窄特征必须具有小于15-20 eV的等效宽度,置信度为99%。如果观察到的质量流入和流出速率之间的趋势延伸到超爱丁顿区域,这些极限远低于预期的>150 eV的线,并且事实上排除了在各种次爱丁顿黑洞中从盘风观察到的线强度。因此,我们不能通过任何实质性的物质柱来观察Holmberg IX X-1的中心区域,排除了球形超爱丁顿吸积模型。如果Holmberg IX X-1是一个超爱丁顿源,任何相关的外流必须具有各向异性的几何形状。最后,铁元素的缺乏表明这颗伴星不可能产生强风,而霍姆伯格IX X-1必须主要通过罗氏瓣溢出吸积。
We present the results of high-quality XMM-NEWTON observations of a ULX in the galaxy NGC 4190. The detection of spectral cutoff in NGC 4190 ULX1 spectra rules out the interpretation of the ULX to be in a standard low/hard canonical accretion state. We report that the high quality EPIC spectra can be better described by broad thermal component, such as a slim disk. In addition we found long term spectral and flux variability in the source using several XMM-NEWTON and Swift data. A clear anti-correlation between flux and power-law photon index is found which further confirms the unusual spectra…
Puzzling accretion onto a black hole in the ultraluminous X-ray source M101 ULX-1
对于亮度超过$10^{39}$ erg s $^{-1}$的超亮X射线源(ULX),有两种解释。它们可能是中等质量的黑洞(大于100- 1000,太阳质量,$M_\odot$),以次最大(次爱丁顿)速率辐射,就像银河系黑洞X射线双星一样,但具有更大,更冷的吸积盘。或者,它们可能是以艾丁顿或超艾丁顿速率辐射的恒星质量黑洞。在被发现时,M101 ULX-1的光度为$3\times10^{39}$ erg s $^{-1}$,超软的热盘光谱具有异常低的温度-不受热电子日冕激发的光子的影响-更符合吸积中等质量黑洞的预期外观。在这里,我们报告的光学光谱监测M101 ULX-1。我们证实了先前的建议,该系统包含一个沃尔夫-拉叶星,并揭示了轨道周期为8.2天。这个黑洞的最小质量为$5M_\odot$,更可能是$20-30M_\odot$,但我们认为它不太可能是一个中等质量的黑洞。因此,它在高Eddinton比率下异常柔软的光谱违反了对恒星质量黑洞吸积的预期。吸积必须发生在被捕获的恒星风中,迄今为止,人们一直认为恒星风的效率很低,无法为超亮源提供动力。
A model of population of ultraluminous X-ray sources with magnetised neutron stars (NULX) in a spiral galaxy with the star formation history similar to that in the thin disc of Milky Way is computed using a hybrid approach. First, applying analytical approximations (code BSE) we construct the ensemble of close binaries (CBS) which can be potential precursors of NULX. Next, evolution with accretion onto magnetised neutron stars (NS) is computed by the evolutionary code MESA. Accretion rate onto NS and X-ray luminosity are calculated for the models of sub- and supercritical discs and for the dis…
Swift observations of the ultraluminous X-ray source Holmberg IX X-1
Holmberg IX X-1是一个著名的超亮X射线源,其X射线亮度约为1 e40 erg/s。斯威夫特的X射线望远镜定期监测该源。自2009年4月以来,该源一直处于扩展的低光度状态。我们利用在不同光度状态下的共加光谱来研究源的光谱行为。简单的幂律和多色盘黑体模型可以排除。然而,最好的整体拟合是由具有冷黑体和暖盘黑体的双热模型提供的。这表明Holmberg IX X-1可能是一个10个太阳质量的黑洞,在比爱丁顿极限高7倍的地方吸积,或者是一个100个太阳质量的最大旋转黑洞,在爱丁顿极限处吸积,我们正在观察吸积盘的内部区域和致密物体的流出物。
Neutrinos from hidden ultraluminous X-ray sources in the Galaxy
Instituto Argentino de Radioastronomía (CCT La Plata, CONICET(阿根廷射电天文研究所);CICPBA(拉普拉塔国立大学天文与地球物理学院);UNLP)(马德普拉塔物理研究所);Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata(马德普拉塔国立大学理学院物理系);Instituto de Investigaciones Físicas de Mar del Plata (IFIMAR – CONICET);Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata
A variable ultraluminous X-ray source in a globular cluster in NGC 4649
本文报道了在椭圆星系NGC 4649中发现的一个与球状星团有关的新的超亮X射线源(ULX)。最初探测到的X射线源的光度低于5 x 10^38 erg/s,但在7年和11年后的后续观测中,它已大幅增亮至2 ~ 3 x 10^39 erg/s。在六个独立的观测过程中,它显示出显着的光谱变化,在连续斜率和吸收柱。在至少一次观察中,还存在X射线通量的短期变异性。这个天体的性质似乎与以超爱丁顿速率(即在超铝吸积状态)吸积的恒星质量黑洞一致,尽管不能排除高度超爱丁顿中子星。在至少一次观测中,吸收柱的增加与短期变率的可能增强相一致,这表明有一股由clusifully辐射驱动的风穿过我们的视线到达该物体
Supercritical accretion onto compact objects may drive massive winds that are nearly spherical, optically thick, and Eddington limited. Blackbody emission from the photosphere is the direct observational signature of the wind. Here we investigate whether or not it can explain the soft emission component seen in the energy spectra of ultraluminous X-ray sources (ULXs). Based on high-quality XMM-Newton spectra of 15 ULXs, we find that the soft component can be modeled as blackbody emission with a nearly constant luminosity, and the 5 known pulsating ULXs (PULXs) in the sample display a blackbody…
NGC 4472 is home to five ultraluminous X-ray sources hosted by globular clusters. These sources have been suggested as good black hole candidates in extragalactic globular clusters$-$ a highly sought after population that may provide observational information regarding the progenitors of merging black hole binaries. In this body of work, we present X-ray and optical follow up to one of these sources, CXOUJ1229410+075744 (GCU1). We find no evidence of [OIII] optical emission in GCU1 which indicates a lack of significant evidence for super-Eddington outflows, unlike what is seen in a handful of …
The missing link: a low mass X-ray binary in M31 seen as an ultraluminous X-ray source
钱德拉最近在M31中发现了一个新的瞬变超亮X射线源(ULX),其亮度约为5 x 10^39 erg/s。在这里,我们分析了一系列的五个随后的XMM-牛顿观测。X射线亮度在1.5个月内的稳定下降给出了一个观测到的约40天的e倍时间尺度;类似于我们银河系中软X射线瞬变的衰变时间尺度。这支持解释这个ULX作为一个恒星质量的黑洞在低质量的X射线二进制(LMXB),吸积在超爱丁顿率。这是进一步支持缺乏检测的O/B星在宁静和XMM-牛顿光谱数据被占主导地位的盘状组件,而不是幂律预期从一个亚爱丁顿中等质量黑洞。这些数据给出了有史以来最好的序列的高爱丁顿馏分光谱组装由于低吸收柱M31和良好校准的带通下降到0.3千电子伏的XMM-牛顿的组合。光谱可以粗略地描述我们目前最好的盘模型,BHSPEC,假设一个10 M的太阳黑洞的最佳拟合自旋~0.4。然而,数据更好地描述了一个两个组件的模型,其中光盘排放显着影响平流,并在高能量的附加低温Comptonisation组件。这可能只是表明目前的光盘模型的局限性,虽然能量依赖的变化也弱支持的数据的两个组件的解释。不管光谱特性的详细解释,这些数据支持存在的吸积到恒星质量的黑洞在LMXB吸积在爱丁顿制度。这使得这个物体,并通过扩展,类似的低光度ULX,“标准”的X射线二进制明确的连接。
A Newly Identified Transient Ultraluminous X-ray Source in M31
California Institute of Technology(加州理工学院);University of Illinois at Urbana-Champaign(伊利诺伊大学厄巴纳-香槟分校);Université de Strasbourg(斯特拉斯堡大学);CNRS(法国国家科学研究中心);Observatoire astronomique de Strasbourg(斯特拉斯堡天文台);University of Hertfordshire(赫特福德大学);University of Southampton(南安普顿大学)
Most ULXs are believed to be powered by super-Eddington accreting neutron stars and, perhaps, black holes. Above the Eddington rate the disc is expected to thicken and to launch powerful winds through radiation pressure. Winds have been recently discovered in several ULXs. However, it is yet unclear whether the thickening of the disc or the wind variability causes the switch between the classical soft and supersoft states observed in some ULXs. In order to understand such phenomenology and the overall super-Eddington mechanism, we undertook a large (800 ks) observing campaign with XMM-Newton t…
We study the spectral properties and accretion flow behavior of an ultraluminous X-ray source M82\,X-1 using {\it NuSTAR} observations. We use the physical two component advective flow (TCAF) model to fit the data and to derive the accretion flow properties of the source. From the model fitted parameters, we found that M82\,X-1 is harboring an intermediate mass black hole at its centre, where the mass varies from $156.04^{+13.51}_{-15.30}$ to $380.96^{28.38}_{-29.76}$ M$_\odot$. The error weighted average mass of the black hole is $273\pm43$ M$_\odot$, which accreted in nearly super-Eddington …
Most ultraluminous X-ray sources (ULXs) are believed to be stellar mass black holes or neutron stars accreting beyond the Eddington limit. Determining the nature of the compact object and the accretion mode from broadband spectroscopy is currently a challenge, but the observed timing properties provide insight into the compact object and details of the geometry and accretion processes. Here we report a timing analysis for an 800 ks XMM-Newton campaign on the supersoft ultraluminous X-ray source, NGC 247 ULX-1. Deep and frequent dips occur in the X-ray light curve, with the amplitude increasing…
Variability is a powerful tool to investigate properties of X-ray binaries (XRB), in particular for Ultraluminous X-ray sources (ULXs) that are mainly detected in the X-ray band. For most ULXs the nature of the accretor is unknown, although a few ULXs have been confirmed to be accreting at super-Eddington rates onto a neutron star (NS). Monitoring these sources is particularly useful both to detect transients and to derive periodicities, linked to orbital and super-orbital modulations. Here we present the results of our monitoring campaign of the galaxy NGC 925, performed with the Neil Gehrels…
The magnetic field of ultraluminous X-ray (ULX) pulsars is the key parameter to understand the nature and accretion physics. However, the typical magnetic field values in these ULX pulsars are still under debate. We used six different torque models to study the magnetic fields of ULX pulsars, to see how derived magnetic fields change with different models, and to determine which models are more suitable for ULX pulsars. We took the currently available period, period derivative, and flux data of 7 confirmed ULX pulsars, M82 X-2, ULX NGC 7793 P13, ULX NGC 5907, NGC 300 ULX1, NGC 1313 X-2, M51 UL…