Related papers: Ultraluminous X-Ray Sources
Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any X-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present…
We investigate models for the class of ultraluminous non-nuclear X-ray sources (ULXs) seen in a number of galaxies and probably associated with star-forming regions. Models where the X-ray emission is assumed to be isotropic run into…
Using archival data from Suzaku, XMM-Newton, and NuSTAR, nine representative Ultra-Luminous X-ray sources (ULXs) in nearby galaxies were studied. Their X-ray spectra were all reproduced with a multi-color disk emission model plus its…
We model the multiwavelength properties of binaries accreting at super-critical rates with the aim to better understand the observational properties of Ultra-luminous X-ray Sources (ULXs). We calculate an extended grid of binary systems…
We present spectroscopic observations of six optical counterparts of intermediate luminosity X-ray sources (ULXs) around nearby galaxies. The spectra of the six objects show the presence of broad emission features. The identification of…
Optical studies of ultraluminous X-ray sources (ULX) in nearby galaxies have turned out to be instrumental in discriminating between various models including the much advertised intermediate mass black hole hypothesis and various beaming…
Ultraluminous X-ray sources (ULX) are extragalactic objects with X-ray luminosities above the Eddington limit for a 10 Msun black hole (BH). ULXs may host super-Eddington accreting neutron stars or stellar mass BH, although the exact…
With the discovery of pulsations in some of the ultra-luminous X-ray sources (ULXs), it is quite clear that most of the ULXs harbor either a neutron star or a stellar mass black hole as a compact object accreting at super-Eddington rates.…
A significant fraction of ultraluminous X-ray sources appear to be embedded in observable ionized nebulae that take the form of large, several 100 pc diameter interstellar bubbles. Here we review optical observations of these bubbles, their…
We show that ultraluminous X-ray sources (ULXs) with coherent X-ray pulsing (PULXs) probably have neutron-star spin axes significantly misaligned from their central accretion discs. Scattering in the funnels collimating their emission and…
It is now widely accepted that most ultraluminous X-ray sources (ULXs) are binary systems whose large (above $10^{39}$ erg s$^{-1}$) apparent luminosities are explained by super-Eddington accretion onto a stellar-mass compact object. Many…
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…
Most ultraluminous X-ray sources (ULXs) are thought to be powered by neutron stars and black holes accreting beyond the Eddington limit. If the compact object is a black hole or a neutron star with a magnetic field $\lesssim10^{12}$ G, the…
We explore the nature of ultraluminous X-ray sources through detailed investigations of their spectral shape using some of the highest quality data available in the XMM-Newton public archives. Phenomenological models allow us to…
Despite the 30-year history of ultra-luminous X-ray sources (ULXs) studies, issues like the majority of their physical natures (i.e., neutron stars, stellar-mass black holes, or intermediate black holes) as well as the accretion mechanisms…
The advanced capabilities of the Chandra and XMM-Newton observatories mean that, for the first time, the detailed study of the brightest point-like X-ray sources in nearby galaxies outside of the local group is a realistic aim. Here, we…
If ultraluminous X-ray sources (ULXs) are powered by accretion onto stellar remnant black holes, then many must be accreting at super-Eddington rates. It is predicted that such high accretion rates should give rise to massive,…
Various arguments strongly suggest that the population of ultraluminous X-ray sources (ULXs: apparent X-ray luminosity > Eddington limit for 10 Msun ~10^39 erg/s) in nearby galaxies are mostly stellar-mass X-ray binaries in unusual…
There are two proposed explanations for ultraluminous X-ray sources (ULXs) with luminosities in excess of $10^{39}$ erg s$^{-1}$. They could be intermediate-mass black holes (more than 100-1,000, solar masses, $M_\odot$) radiating at…
The Ultra Luminous X-ray Sources (ULXs) are unique in exhibiting moderately bright X-ray luminosities, $L_{\rm x} \sim 10^{38-40} {\rm erg~s^{-1}}$, and relatively high blackbody temperatures, $\Tin \sim 1.0-2.0 {\rm keV}$. From the…