Related papers: A New Transient Ultraluminous X-ray Source in NGC …
We examined the variability of three ultra-luminous X-ray sources (ULXs) in the 2003, 110 ks XMM-Newton observation of NGC253. Remarkably, we discovered ULX1 to be three times more variable than ULX2 in the 0.3--10 keV band, even though…
We report the discovery of a new ultraluminous X-ray source (ULX) in the nearby galaxy NGC 4244 from Chandra archival data. The source, 1WGAJ1216.9+3743, is one of the least luminous and softest ULXs discovered so far. Its X-ray spectrum is…
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…
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…
A new, transient ultraluminous X-ray source (ULX) was recently discovered by Chandra in M31 with a luminosity at ~ 5 x 10^39 erg/s. Here we analyse a series of five subsequent XMM-Newton observations. The steady decline in X-ray luminosity…
We present broadband X-ray analyses of a sample of bright ultraluminous X-ray sources with the goal of investigating the spectral similarity of this population to the known ULX pulsars, M82 X-2, NGC7793 P13 and NGC5907 ULX. We perform a…
We present some results from an archival VLA study of ultraluminous X-ray source s (ULXs). These unresolved non-nuclear X-ray sources have luminosities (L_X >= 1 0^39 ergs/sec) which may require somewhat exotic explanations, such as…
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…
A prime motivation for compiling catalogues of any celestial X-ray source is to increase our numbers of rare sub-classes. In this work we take a recent multi-mission catalogue of ultraluminous X-ray sources (ULXs) and look for hitherto…
Ultraluminous and hyperluminous X-ray sources (ULXs and HLXs) are among the brightest astrophysical objects in the X-ray sky. While ULXs most likely host stellar-mass compact objects accreting at super-Eddington rates, HLXs are compelling…
(Abridged) We present results based on XMM-Newton observation of the nearby spiral galaxy M51 (NGC5194 and NGC5195). Two ULXs in NGC5194 show evidence for short-term variability, and all but two ULXs vary on long time scales (over a…
The number of Ultraluminous X-ray Sources (ULXs) is observed to be correlated with the current star formation rate in late-type galaxies and with the stellar mass in early-type galaxies (ETGs). Since there is very little gas, dust or star…
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.…
We consider ultraluminous X-ray sources (ULXs) where the accretor is a neutron star rather than a black hole. We show that the recently-discovered example (M82 X-2) fits naturally into the simple picture of ULXs as beamed X-ray sources fed…
We present spectroscopic observations of three Ultra Luminous X-ray sources (ULX's). Two of them are very close to the active galaxy NGC 720 and the other is near NGC 1073. The two around NGC 720 turn out to be quasars at z=0.964 and z=…
Ultraluminous X-ray sources are non-nuclear point sources exceeding the Eddington luminosity of a 10 Solar mass black hole. Modern consensus for a majority of the ULX population is that they are powered by stellar-mass black holes or…
We report the XMM-Newton detection of a moderately bright X-ray source superimposed on the outer arms of the inactive spiral galaxy MCG-03-34-63 (z=0.0213). It is clearly offset from the nucleus (by about 19'') but well within the D25…
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…
We report the discovery of a new ultraluminous X-ray source (ULX) 2XMM J125048.6+410743 within the spiral galaxy M94. The source has been observed by ROSAT, Chandra, and XMM-Newton on several occasions, exhibiting as a highly variable…
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…