Related papers: New observations of ULX supershells, and their imp…
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=…
We have performed a set of simulations of expanding, spherically symmetric nebulae inflated by winds from accreting black holes in ultraluminous X-ray sources (ULXs). We implemented a realistic cooling function to account for free-free and…
The extended nebulae formed as pulsar winds expand into their surroundings provide information about the composition of the winds, the injection history from the host pulsar, and the material into which the nebulae are expanding.…
The understanding of the nature of ultra-high-energy cosmic rays is one of the most intriguing open questions for current and future observatories. These particles are expected to be accelerated in extragalactic sources. Because of their…
One hundred seven ultraluminous X-ray (ULX) sources with 0.3-10.0 keV luminosities in excess of 1e39 erg/s are identified in a complete sample of 127 nearby galaxies. The sample includes all galaxies within 14.5 Mpc above the completeness…
We present a model for the prediction of the optical/infra-red emission from ULXs. In the model, ULXs are binary systems with accretion taking place through Roche lobe overflow. We show that irradiation effects and presence of an accretion…
Ultra-luminous X-ray sources (ULXs) are a class of extra-galactic, point-like, off-nuclear X-ray sources with X-ray luminosity from $\sim 10^{39}$~erg s$^{-1}$ to $10^{41}$~erg s$^{-1}$. We investigated the temporal and broadband X-ray…
Ultraluminous X-ray sources (ULXs) are bright X-ray sources in nearby galaxies not associated with the central supermassive black hole. Their luminosities imply they are powered by either an extreme accretion rate onto a compact stellar…
We present an analysis of the optical properties of three Ultra Luminous X-ray (ULX) sources identified in NGC 925. We use Integral field unit data from the George Mitchel spectrograph in the context of the Metal-THINGS survey. The optical…
Based on the expected population of core collapse supernova remnants and the huge number of detected pulsars in the Galaxy, still representing only a fraction of the real population, pulsar wind nebulae are likely to constitute one of the…
We present results of a Chandra survey of the ultra-luminous X-ray sources (ULX) in 13 normal galaxies, in which we combine source detection with X-ray flux measurement. 22 ULX were detected, i.e. with L_x > 1 x 10^{39} erg s^{-1} (L_10),…
We report the identification of a recurrent ultraluminous X-ray source (ULX), a highly absorbed X-ray source (possibly a background AGN), and a young supernova remnant near the center of the starburst galaxy M82. From a series of Chandra…
A thorough search for Ultraluminous X-ray source candidates within the Local Volume is made. The search spatially matches potential ULXs detected in X-ray images or cataloged in the literature with galaxies tabulated in the Catalog of…
The most extreme ultraluminous X-ray sources (ULXs), with $L_\mathrm{X} > 5 \times 10^{40}$ erg s$^{-1}$, are amongst the best candidates for hosting intermediate-mass black holes (IMBHs) in the haloes of galaxies. Jet radio emission is…
We present a spectrophotometric imaging study of the emission bubble N70 (DEM 301) in the Large Magellanic Cloud. N70 is approximately 100 pc in size with a nearly circular shell-like morphology. The nebular emission is powered by an…
I briefly review much of the X-ray and optical data on the nature of the ULXs in nearby galaxies. I present new results on radio emission, finding that the radio is usually rather luminous and extended. I review the X-ray data on timing and…
The accreting compact objects in most of ultraluminous X-ray sources (ULXs) are likely to be neutron stars rather than black holes as suggested by the recent detection of periodic pulsations from some of these sources located in neighboring…
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…
Recent models of the formation of ultra-luminous X-ray sources (ULXs) predict that they preferentially form in low-metallicity environments. We look at the metallicity of the nebula surrounding NGC 1313 X-2, one of the best-studied ULXs.…
The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray (ULX) sources have finally enabled us to recognize a subclass within the ULX class: the great pretenders, neutron stars (NSs) that appear to emit X-ray radiation…