Related papers: Slim Disk Model for Ultra-Luminous X-Ray Sources
The X-ray spectra of the most extreme ultra-luminous X-ray sources -- those with L > 1 E+40 erg/s -- remain something of a mystery. Spectral roll-over in the 5-10 keV band was originally detected in in the deepest XMM-Newton observations of…
Ultraluminous X-ray sources (ULXs) are accreting black holes that may contain the missing population of intermediate mass black holes or reflect super-Eddington accretion physics. Ten years of Chandra and XMM-Newton observations of ULXs,…
We argue that both the extreme soft X-ray excess and the large-amplitude variability of Narrow-Line Seyfert 1 galaxies (NLS1s) can be explained in the framework of the slim disk model. When the disk luminosity approaches the Eddington…
The origin of the variable X-ray emission in the $(0.3-30)\,$keV energy range of ultraluminous X-ray sources (ULXs) remains unclear, making it difficult to constrain the mass of the central compact object. X-ray luminosities of bright ULXs…
Studies of X-ray continuum emission and flux variability have not conclusively revealed the nature of ultra-luminous X-ray sources (ULXs) at the high-luminosity end of the distribution (those with Lx > 1e40 erg/s). These are of particular…
We observed the Ultraluminous X-ray Source IC 342 X-1 simultaneously in X-ray and radio with Chandra and the JVLA to investigate previously reported unresolved radio emission coincident with the ULX. The Chandra data reveal a spectrum that…
Following a serendipitous detection with the NuSTAR observatory, we present a multi-epoch spectral and temporal analysis of an extreme ultraluminous X-ray source (ULX) located in the outskirts of the Circinus galaxy, hereafter Circinus…
(Abridged) Narrow Line Seyfert 1 (NLS1) galaxies have low mass black holes and mass accretion rates close to (or exceeding) Eddington, so a standard blackbody accretion disc should peak in the EUV. However, the lack of true absorption…
A number of ultraluminous X-ray sources (ULXs) are physically associated with extragalactic globular clusters (GCs). We undertake a systematic X-ray analysis of eight of the brightest of these sources. We fit the spectra of the GC ULXs to…
Ultra-luminous X-ray sources (ULXs) are those X-ray sources located away from the centre of their host galaxy with luminosities exceeding the Eddington limit of a stellar-mass black hole ($L_X>10^{39}\;{\rm erg\,s}^{-1}$). The discovery of…
Two {\it ASCA} observations were made of two ultra-luminous compact X-ray sources (ULXs), Source 1 and Source 2, in the spiral galaxy IC 342. In the 1993 observation, Source 2 showed a 0.5--10 keV luminosity of $6 \times 10^{39}$ ergs…
Ultraluminous X-ray sources (ULXs) are some of the most enigmatic X-ray bright sources known to date. It is generally accepted that they cannot host black holes as large as those associated with active galaxies, but they appear to be…
The luminosity range at and just below the 10^39 erg/s cut-off for defining ultraluminous X-ray sources (ULXs) is a little-explored regime. It none-the-less hosts a large number of X-ray sources, and has great potential for improving our…
We present the results from an X-ray and optical study of a new sample of eight extreme luminosity ultraluminous X-ray source (ULX) candidates, which were selected as the brightest ULXs (with L_X > 5x10^40 erg/s) located within 100 Mpc…
The thermal dominant state in black hole binaries (BHBs) is well understood but rarely seen in ultraluminous X-ray sources (ULXs). Using simultaneous observations of M82 with Chandra and XMM-Newton, we report the first likely identification…
We apply a reflection-based model to the best available XMM-Newton spectra of X-ray bright UltraLuminous X-ray (ULX) sources (NGC 1313 X-1, NGC 1313 X-2, M 81 X-6, Holmberg IX X-1, NGC 5408 X-1 and Holmberg II X-1). A spectral drop is…
The atomic features in the X-ray spectra of the ultraluminous X-ray source (ULX) may be associated with the outflow (Middleton et al. 2015), which may provide a way to explore the physics of the ULXs. We construct a conical outflow model,…
We compare standard models of accretion disks around black holes that include the appropriate zero-torque inner boundary condition and relativistic effects on the emission and propagation of radiation. The comparison is performed adopting…
M82 X-1 is one of the brightest ultraluminous X-ray sources (ULXs) known, which, assuming Eddington-limited accretion and other considerations, makes it one of the best intermediate-mass black hole (IMBH) candidates. However, the ULX may…
We present an analysis of X-ray observations of the Ultraluminous X-ray source (ULX) in IZw18 based on archival data taken with Chandra, XMM-Newton, and Suzaku. This ULX is considered to be an intermediate-mass black hole candidate simply…