Related papers: A new candidate pulsating ULX in NGC 7793
Based on our long (~ 300 ks) 2007 XMM-Newton observation of the Seyfert galaxy NGC 1365, we report here on the spectral and timing behaviour of two ultraluminous X-ray sources, which had previously reached isotropic X-ray luminosities L_X ~…
We present the results of two Chandra observations (separated by 1 year) of the population of X-ray sources in the spiral galaxy M51 (NGC 5194 and NGC 5195). 113 X-ray sources have been detected in an 8'.4x8'.4 region. Nine and 28 sources…
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…
The discovery of pulsating ultra-luminous X-ray sources (PULX) suggests that neutron stars are presumably common within the ultra-luminous X-ray source (ULX) population though the majority of the population members are currently lacking…
We analyse all the available Chandra observations of the Cartwheel Galaxy and its compact group, taken between 2001 and 2008, with the main aim of addressing the variability in the X-ray band for this spectacular collisional ring galaxy. We…
NGC 5408 X-1 is a well-studied ultraluminous X-ray source (ULX) that has been seen to emit in X-rays persistently above the Eddington limit of a stellar-mass black hole for years. In this paper we report on the most extensive X-ray…
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…
Some ultraluminous X-ray sources (ULXs) are surrounded by collisionally ionized bubbles, larger and more energetic than supernova remnants: they are evidence of the powerful outflows associated with super-Eddington X-ray sources. We…
An ultraluminous X-ray source (ULX) in NGC 5252 has been known as a strong candidate for an off-nuclear intermediate-mass black hole. We present near-infrared imaging data of the ULX obtained with the William Herschel Telescope. Using this…
We report the discovery of a ultraluminous X-ray source (ULX; CXO J133815.6+043255) in NGC 5252. This ULX is an off-nuclear point-source, which is 22$^{\prime\prime}$ away from the center of NGC 5252, and has an X-ray luminosity of 1.5…
The end points of massive star evolution are poorly known, especially those in interacting binary systems containing compact objects, such as neutron stars or black holes. Such systems are bright in X-rays, and the most luminous among them…
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…
Ultraluminous X-ray sources (ULXs) are X-ray binary systems containing an accreting neutron star (NS) or black hole emitting at luminosities above the Eddington limit of a $10M_{\odot}$ black hole. Approximately 1900 (either confirmed or…
We present new multi-wavelength observations of two ultraluminous X-ray sources (ULXs) hosted by globular clusters (GCs) in the giant elliptical NGC 1399, focusing on CXO J0338318-352604 (GCU7), only the second GC ULX known to have luminous…
First results from a deep XMM-Newton observation of a field in the Large Magellanic Cloud (LMC) near the northern rim of the supergiant shell LMC 4 are presented. Spectral and temporal analyses of a sample of selected X-ray sources yielded…
We studied the multiband properties of two ultraluminous X-ray sources (2CXO J225728.9-410211 = X-1 and 2CXO J225724.7-410343 = X-2) and their surroundings, in the spiral galaxy NGC 7424. Both sources have approached X-ray luminosities…
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.…
Chandra observations of 17 nearby galaxies were analysed and 166 bright sources with X-ray counts > 100, were chosen for temporal analysis. Fractional root mean square variability amplitudes were estimated for lightcurves binned at ~ 4 ksec…
We study the evolution of newborn neutron stars in high-mass X-ray binaries interacting with a wind-fed super-Eddington disk. The inner disk is regularized to a radiation-dominated quasi-spherical configuration for which we calculate the…
Ultraluminous X-ray sources (ULXs) are enigmatic sources first discovered in the 1980s in external galaxies. They are characterized by their extraordinarily high X-ray luminosity, which often exceeds $10^{40}\, \rm{erg \; s^{-1}}$. Our…