Related papers: Herschel views on ultra-luminous X-ray sources
Ultraluminous X-ray sources (ULXs) are a population of extragalactic objects whose luminosity exceeds the Eddington limit for a 10 Msun black hole (BH). Their properties have been widely interpreted in terms of accreting stellar-mass or…
The ultraluminous X-ray sources (ULXs) were isolated in external galaxies for the last 5 years. Their X-ray luminosities exceed 100-10000 times those of brightest Milky Way black hole binaries and they are extremely variable. There are two…
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…
We review the available estimates of the masses of the compact object in Ultraluminous X-ray Sources (ULXs) and critically reconsider the stellar-mass versus intermediate-mass black hole interpretations. Black holes of several hundreds to…
The nature of ultraluminous X-ray sources (ULXs) -- off-nuclear extra-galactic sources with luminosity, assumed isotropic, $\gtrsim 10^{39}$ erg s$^{-1}$ -- is still debated. One possibility is that ULXs are stellar black holes accreting…
Multiwavelength observations may help us understand the physical nature of the ultraluminous X-ray sources (ULXs) found in external galaxies. Enabled by the arcsecond X-ray source positions now available from Chandra, there has been…
Ultraluminous X-ray sources (ULXs) are bright extragalactic sources with X-ray luminosities above 10^39 erg/s powered by accretion onto compact objects. According to the first studies performed with XMM-Newton ULXs seemed to be excellent…
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,…
Ultraluminous X-ray sources (ULXs), first observed ~30 years ago, have been argued as extreme stellar mass black hole binaries or a new class intermediate mass black hole. In order to settle this debate, scientists have utilised a wide…
The origin and nature of Ultra-Luminous X-ray sources (ULXs) is a contentious and controversial topic. There are ongoing debates about the masses of the objects responsible, their sources of mass for accretion, and their relation to stellar…
The nature of the ultra-luminous X-ray sources (ULXs) in the nearby galaxies is a matter of debates. One of the popular hypothesis associates them with accretion at a sub-Eddington rate on to intermediate mass black holes. Another…
Ultraluminous X-ray sources (ULXs) were identified as a separate class of objects in 2000 based on data from the Chandra X-Ray Observatory. These are unique objects: their X-ray luminosities exceed the Eddington limit for a typical…
One hundred fifty-four discrete non-nuclear Ultra-Luminous X-ray (ULX) sources, with intrinsic X-ray luminosities >1e39 ergs/s, are identified in 82 galaxies observed with Chandra's Advanced CCD Imaging Spectrometer. Source positions, X-ray…
Despite much observational and theoretical effort little is presently known about the nature of the luminous non-nuclear X-ray sources which appear to largely surpass the Eddington limit of a few solar masses. Here we present first results…
In the last few years multiwavelength observations have boosted our understanding of Ultraluminous X-ray Sources (ULXs). Yet, the most fundamental questions on ULXs still remain to be definitively answered: do they contain stellar or…
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…
Many upcoming surveys, particularly in the radio and optical domains, are designed to probe either the temporal and/or the spatial variability of a range of astronomical objects. In the light of these high resolution surveys, we review the…
Nearby galaxies host ultra-luminous X-ray sources (ULXs), whose nature remains largely unknown. Until the discovery of the first ULX pulsar, M82 X-2, the mechanism powering the large luminosities of most ULXs was thought to be…
Ultraluminous X-ray sources (ULXs) with Lx > 10^{39} ergs/s have been discovered in great numbers in external galaxies with ROSAT, Chandra, and XMM. The central question regarding this important class of sources is whether they represent an…
While many observed ultra-luminous X-ray sources (ULXs, Lx > 10^39 erg s^-1) could be extragalactic X-ray binaries (XRBs) emitting close to the Eddington limit, the highest-luminosity ULXs (Lx > 3x10^39 erg s^-1) exceed the isotropic…