We report the discovery of a new candidate ultraluminous X-ray source (ULX) in the nearby edge-on spiral galaxy NGC 891. The source, which has an absorbed flux of F_X ~ 10^-12 erg/s/cm^2 (corresponding to L_X > 10^40 erg/s at 9 Mpc), must have begun its outburst in the past 5 years as it is not detected in prior X-ray observations between 1986 and 2006. We try empirical fits to the XMM-Newton spectrum, finding that the spectrum is fit very well as emission from a hot disk, a cool irradiated disk, or blurred reflection from the innermost region of the disk. The simplest physically motivated model with an excellent fit is a hot disk around a stellar-mass black hole (a super-Eddington outburst), but equally good fits are found for each model. We suggest several follow-up experiments that could falsify these models.
A long-term X-ray monitoring of the ultraluminous X-ray source NGC 5408 X-1 with Swift reveals the presence of dips but no orbital period
NGC 5408 X-1是一个经过充分研究的超亮X射线源(ULX),多年来一直被认为发射出超过恒星质量黑洞爱丁顿极限的X射线。在本文中,我们报告了最广泛的X射线监测的ULX,使用超过四年的观测斯威夫特卫星。我们发现Strohmayer(2009)报告的115天周期在几个周期后就消失了,证实了Foster等人(2010)的怀疑,即周期很可能是超轨道的,而不是系统的轨道周期。我们还报告了一个明确的浸渍行为的来源,可能与(超)轨道现象。所有这些特征都让人想起银河系的X射线双星,并加强了它们与ULX的联系。对倾角进行更深入的观测可以帮助解决对ULX光谱成分解释的模糊性。
We studied the apparent galaxy pair NGC 1232 / NGC 1232A with Chandra, looking for evidence of interactions and collisions. We report that there is no cloud of diffuse emission in NGC 1232, contrary to previous claims in the literature. Instead, we find that the small "companion" galaxy NGC 1232A contains three ultraluminous X-ray sources (ULXs) with peak 0.3-10 keV luminosities above 10^{40} erg/s (assuming a cosmological distance of 93 Mpc for this galaxy). For its mass, morphology, metal abundance and bright ULX population, NGC 1232A is analogous to the more nearby late-type spiral NGC 1313…
We investigate a sample of seven edge-on spiral galaxies using Chandra observations. Edge-on spiral galaxies allow us to clearly separate source associated with their star-forming regions versus the outer edges of the system; offering a clear advantage over other systems. We uncover a number of X-ray point sources across these galaxies, and after eliminating contaminating foreground and background sources, we identify 12 candidate ultraluminous X-ray sources. All of these sources are projected onto the central regions, implying that the majority of ULXs in this sample of spiral galaxies are di…
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
Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13
NGC 7793 P13是一个可变(亮度范围~100)的超亮X射线源(ULX),被认为是一个双星系统中的恒星质量黑洞,其质量小于15 M $_{\odot}$,轨道周期为64 d,伴星为18-23 M $_{\odot}$ B 9 Ia。在EXTraS项目中,我们在NGC 7793 P13的两次XMM-牛顿观测中发现了周期约为0.42 s的脉动,在此期间,在$L_{\mathrm{X}}\sim2.1\times10^{39}$和$5\times10^{39}$ erg s $^{-1}$(0.3-10 keV波段)检测到了源。这些发现明确地表明,NGC 7793 P13中的致密物体是一颗以超爱丁顿速率吸积的中子星。虽然标准的吸积模型面临的困难占脉冲星X射线光度,多极磁场的存在与$B$ ~几个$\times$ 10 $^{13}$ G靠近吸积柱的底部似乎是在协议的系统的属性。
We have identified three ultraluminous X-ray sources (ULXs) hosted by globular clusters (GCs) within NGC 1316's stellar system. These discoveries bring the total number of known ULXs in GCs up to 20. We find that the X-ray spectra of the three new sources do not deviate from the established pattern of spectral behaviour of the other known GC ULXs. The consistency of the X-ray spectral behaviour for these sources points to multiple paths of formation and evolution mechanisms for these rare and unique sources. Using the now larger sample of GC ULXs, we compare the optical properties of the entir…
Evidence for candidate X-ray pulsations from the ultraluminous X-ray source NGC 7456 ULX-1
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(南京大学现代天文与天体物理教育部重点实验室)
The accreting compact objects in most of ultraluminous X-ray sources (ULXs) are likely to be neutron stars rather than black holes as suggested by the recent detection of periodic pulsations from some of these sources located in neighboring galaxies and one ULX that has hitherto been discovered in our own galaxy. As a member of the ULX family, NGC 300 ULX1 is a new pulsating ULX (PULX) spinning up at substantially high rates compared with other PULXs. In this paper, the strength of the magnetic field on the surface of the neutron star is inferred from the energy of the cyclotron absorption lin…
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…
The two Ultraluminous X-ray sources in the galaxy NGC 925
NGC 925 ULX-1和ULX-2是位于NGC 925中的两个超亮X射线源,距离为8.5 Mpc。这是我们第一次分析两个来源的高质量,同时XMM-Newton和NuSTAR数据。虽然乍一看ULX-1类似于一个中等质量的黑洞候选者(IMBH),因为它的高X射线光度($(2$ $-$ $4)\times10^{40}$ erg s $^{-1}$)和它的光谱/时间的特点,仔细检查表明,它的属性更类似于一个典型的超爱丁顿吸积恒星黑洞,我们将其归类为一个“加宽的光盘”超明亮的X射线源。基于这种光谱状态的物理解释,我们建议,ULX-1被认为是在小倾角,可能通过一个强大的风起源于吸积盘疏散锥。ULX-2的光谱分类是不太确定的,但我们不赞成IMBH吸积亚爱丁顿率,因为它的光谱/时间属性可以关联到银河系吸积黑洞二进制的软或硬状态。
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 …
Spectral variability in Swift and Chandra observations of the Ultraluminous source NGC 55 ULX1
NGC 55 ULX 1是一个明亮的超铝X射线源,距离地球1.78 Mpc。我们分析了2013年4月至8月期间拍摄的20个Swift观测样本,以及2001年9月和2004年6月拍摄的两个Chandra观测样本。我们只发现了有限数量的光变曲线的下降,以前报道发生在这个源的边缘提示,虽然由于数据的低计数统计的不确定性很大。Chandra和Swift光谱显示出清晰的光谱变异性,这与在其他ULX中观察到的相似。我们可以解释这种光谱的变化方面的变化,在两个标准化和固有的柱密度的两个组件的模型组成的黑体(软组件)和多色吸积盘(硬组件)。我们讨论的可能性,强大的外流喷出的光盘是部分负责这种光谱的变化。
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…
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…
Archival {\it XMM-Newton}, {\it Chandra} and {\it Hubble Space Telescope (HST)} data have been used to study the X-ray and optical properties of two candidate ultraluminous X-ray sources (ULXs) in NGC\,4536. In order to search for potential optical counterparts, relative astrometry between {\it Chandra} and {\it HST} was improved, and as a result, optical counterparts were detected for both X-ray sources. To complement our findings (based on the archival data), ground-based optical spectra of the counterparts were obtained with the 6m BTA Telescope located at the Special Astrophysical Observat…
We report X-ray spectral variability in an ultraluminous X-ray source NGC 1042 ULX1, using archival XMM-Newton and recent NuSTAR observations. In long-term evolution, the source has shown a trend of variation in spectral hardness. The variability in different XMM-Newton observations is prominent above $\sim 1$ keV. Cool thermal disk component with a characteristic temperature of $\sim 0.2$ keV manifests that the spectral state of NGC 1042 ULX1 in all epochs is similar to that of the ultraluminous state sources. An apparent anti-correlation between luminosity and powerlaw index demonstrates tha…
We perform empirical fits to the \emph{Chandra} and \emph{XMM-Newton} spectra of three ultraluminous X-ray sources (ULXs) in the edge-on spiral galaxy NGC 891, monitoring the region over a seventeen year time window. One of these sources has been visible since the early 1990s with \emph{ROSAT} and has been observed multiple times with \emph{Chandra} and \emph{XMM-Newton}. Another has been visible since 2011. We build upon prior analyses of these sources by analyzing all available data at all epochs. Where possible \emph{Chandra} data is used, since its superior spatial resolution allows for mo…
A candidate proton cyclotron feature in the ultraluminous X-ray source NGC 4656 ULX-1
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata(拉普拉塔国立大学天文与地球物理科学学院);Instituto de Astrofísica de Canarias (IAC)(加那利天体物理学研究所);Departamento de Astrofísica, Universidad de La Laguna(拉古纳大学天体物理学系);Space Telescope Science Institute(太空望远镜科学研究所);Instituto Argentino de Radioastronomía (CCT La Plata, CONICET(阿根廷射电天文学研究所);CICPBA(意大利国家天体物理研究所卡利亚里天文台);UNLP)(空间科学研究所);INAF, Osservatorio Astronomico di Cagliari(加泰罗尼亚空间研究学院);Institute of Space Sciences (ICE, CSIC);Institut d’Estudis Espacials de Catalunya (IEEC)
A comparative study of occurrence rates and nature of Ultraluminous X-ray sources in spiral and elliptical galaxies
Manipal Centre for Natural Sciences, Manipal Academy of Higher Education(马尼帕尔高等教育部马尼帕尔自然科学中心);Space Astronomy Group, U R Rao Satellite Center, ISITE Campus(印度空间研究组织乌尔·拉奥卫星中心空间天文学组)
We report on results from a one-year soft X-ray observing campaign of the ultraluminous X-ray pulsar NGC 300 ULX-1 by the Neutron star Interior Composition Explorer (NICER) during 2018--2019. Our analysis also made use of data from Swift/XRT and XMM-Newton in order to model and remove contamination from the nearby eclipsing X-ray binary NGC 300 X-1. We constructed and fitted a series of 5-day averaged NICER spectra of NGC 300 ULX-1 in the 0.4--4.0 keV range to evaluate the long-term spectral evolution of the source, and found that an absorbed power-law model provided the best fit overall. Over…
NGC 1313 X-2 is one of the few known pulsating ultraluminous X-ray sources (PULXs), and so is thought to contain a neutron star that accretes at highly super-Eddington rates. However, the physics of this accretion remains to be determined. Here we report the results of two simultaneous XMM-Newton and HST observations of this PULX taken to observe two distinct X-ray behaviours as defined from its Swift light curve. We find that the X-ray spectrum of the PULX is best described by the hard ultraluminous (HUL) regime during the observation taken in the lower flux, lower variability amplitude behav…
Aims. We analyzed multi-epoch X-ray data of the Ultraluminous X-ray source (ULX) NGC 5055 X-1, with luminosity up to $2.32\times10^{40}\ \rm erg\ s^{-1}$, in order to constrain the physical parameters of the source. Methods. We performed timing and spectral analysis of Chandra and XMM-Newton observations. We used spectral models which assume the emission is from an accreting black hole system. We fit the data with a multicolor disk (MCD) combined with a powerlaw (PL) or a thermal Comptonization (NTHCOMP) component, and compared those fits with a slim disk model. Results. The lightcurves of the…
Identification of three new ultraluminous X-ray sources in NGC 4631 and NGC 1097: Evidence for stellar-mass black holes
Department of Physics, University of Çukurova(丘鲁罗瓦大学物理系);Space Science and Solar Energy Research and Application Center (UZAYMER), University of Çukurova(丘鲁罗瓦大学空间科学与太阳能研究与应用中心)