Related papers: An Extremely Luminous and Variable Ultraluminous X…
Ultraluminous X-ray sources (ULXs) are likely to include different physical types of objects. We discuss some possible subclasses, reviewing the properties of a sample of ULXs recently observed by Chandra and XMM-Newton. Sources with an…
In this study, we report identification of a new ultraluminous X-ray source (ULX) named as X-7 in NGC 1316, with an unabsorbed luminosity of 2.1$\times$10$^{39}$ erg s$^{-1}$ using the two recent Chandra archival observations. The X-7 was…
Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with X-ray luminosities above 1e39 erg/s. The ULX population counts several hundreds objects but only a minor fraction is well studied. Here we present a detailed…
Ultraluminous X-ray sources (ULXs) are point-like sources that exhibit apparent X-ray luminosities exceeding the Eddington limit for stellar-mass compact objects. A widely accepted interpretation is that these systems are X-ray binaries…
Ultraluminous X-ray sources (ULXs) are non-nuclear X-ray binary systems that exceed the Eddington luminosity for a 10 Msun black hole. The majority of these sources are thought to be stellar-mass compact objects accreting at super-Eddington…
We report on the identification of the optical and infrared counterparts of the ultraluminous X-ray source (ULX) XMMU J121214.5+131248 (NGC4168-ULX1). The optical spectrum yields a redshift of z=0.217, which implies that the ULX is not…
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 report here the discovery of NGC 7793 ULX-4, a new transient ultraluminous X-ray source (ULX) in NGC 7793, a spiral galaxy already well known for harbouring several ULXs. This new source underwent an outburst in 2012, when it was…
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…
We present a spectral variability study of the ultraluminous X-ray source NGC 4490 ULX-8 based on 14 Chandra, 6 XMM-Newton and 19 Swift-XRT observations obtained between 2000 and 2024. The X-ray spectra are modelled using absorbed power-law…
We present the results of an archival XMM-Newton study of the bright X-ray point sources (L_X > 10^38 erg/s) in 32 nearby galaxies. From our list of approximately 100 point sources, we attempt to determine if there is a low-state…
We present optical observations of a ULX in the nearby spiral galaxy IC 342. This variable source has an average X-ray luminosity of some 10^{40} erg/s. At the position of the source there is an ionized nebula (the "Tooth") having huge…
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…
Late type non-starburst galaxies have been shown to contain X-ray emitting objects, some being ultraluminous X-ray sources. We report on XMM-Newton observations of 11 nearby, late-type galaxies previously observed with the Hubble Space…
Using two archival XMM-Newton observations, we identify strong X-ray flux variations in NGC 6946 X-1 indicating it is the most variable ultraluminous X-ray source (ULX) on mHz time scales known so far. The 1-10 keV lightcurve exhibits…
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…
We present the first results of an XMM-Newton EPIC observation of the luminous X-ray source population in the supergiant spiral galaxy M101. We have studied the properties of the fourteen most luminous sources, all of which have intrinsic…
An XMM-Newton study of ultraluminous X-ray sources (ULX) has been performed in a sample of 10 nearby Seyfert galaxies. Eighteen ULX have been found with positional uncertainty of about 4". The large collecting area of XMM-Newton makes the…
We present results from the major coordinated X-ray observing program on the ULX NGC 1313 X-1 performed in 2017, combining $XMM$-$Newton$, $Chandra$ and $NuSTAR$, focusing on the evolution of the broadband ($\sim$0.3-30.0 keV) continuum…
XMM-Newton EPIC observations have revealed a bright point-like X-ray source in the nearby Magellanic-type galaxy NGC 55. At the distance of NGC 55, the maximum observed X-ray luminosity of the source, designated as XMMU J001528.9-391319, is…