Related papers: Understanding ULX Nebulae in the Framework of Supe…
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…
We show that the hyperluminous source HLX--1 may be a stellar--mass binary system like SS433, but seen along its X--ray beams. The precession of these beams gives the $\sim 1$~yr characteristic timescale of the light curve, while the…
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…
Most ultraluminous X-ray sources (ULXs) display a typical set of properties not seen in Galactic stellar-mass black holes (BHs): higher luminosity Lx > 3 10^39 erg/s, unusually soft X-ray components (kT < 0.3 keV) and a characteristic…
A previously undetected X-ray source (L_X<10**36 erg/s) in the strongly star-forming galaxy M83 entered an ultraluminous state between August 2009 and December 2010. It was first seen with Chandra on 23 December 2010 at L_X ~ 4 10**39…
Aims. We report our finding of a high excitation emission line nebula associated with an Ultra Luminous X-ray source (ULX) at $z=$ 0.027, which we found in our Chandra observation of the AKARI North Ecliptic Pole (NEP) Deep Field. Methods.…
A sub-set of the brightest ultraluminous X-ray sources (ULXs), with X-ray luminosities well above $10^{40}$ erg s$^{-1}$, typically have energy spectra which can be well described as hard power-laws, and short-term variability in excess of…
It was recently proposed that a significant fraction of ultraluminous X-ray sources (ULXs) actually host a neutron star (NS) accretor. We have performed a systematic study on the NS ULX population in Milky Way-like galaxies, by combining…
Optical studies of ultra-luminous X-ray sources is an essential step in understanding the nature of these enigmatic sources, and in this paper we report our studies of five ULXs in NGC4559, NGC5194, NGC1313 and NGC628 observed with the…
The presence or lack of eclipses in the X-ray lightcurves of ultraluminous X-ray sources (ULXs) can be directly linked to the accreting system geometry. In the case where the compact object is stellar mass and radiates isotropically, we…
Optical photometric and spectroscopic data are presented that show an association of an ultraluminous X-ray source in NGC 7331 with a young star cluster of mass 1.1e5 solar masses and age 4.25 Myr. If the ULX is part of the bright stellar…
The nature of ultraluminous X-ray sources (ULXs) is not yet fully understood but it can be done in the most efficient way by analyzing its optical emission and environment. We present preliminary results of photometric and spectral studies…
A major prediction of most super-Eddington accretion theories is the presence of anisotropic emission from supercritical disks, but the degree of anisotropy and its dependency with energy remain poorly constrained observationally. A key…
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…
We have searched for ultraluminous X-ray sources (ULXs) in a sample of 28 elliptical and S0 galaxies observed with Chandra. We find that the number of X-ray sources detected at a flux level that would correspond to a 0.3-10 keV X-ray…
Ultraluminous X-ray sources (ULXs) were once largely believed to be powered by super-Eddington accretion onto stellar-mass black holes, although in some rare cases, ULXs also serve as potential candidates for (sub-Eddington) intermediate…
Recent observations of galaxies continue to reveal new ultraluminous X-ray sources (ULXs), increasing their known population and improving the statistics needed to understand their nature. We study the ULX populations of NGC 4631 and NGC…
We present a new, multi-mission catalogue of ultraluminous X-ray source (ULX) candidates, based on recent data releases from each of the XMM-Newton, Swift and Chandra observatories (the 4XMM-DR10, 2SXPS and CSC2 catalogues, respectively).…
We have constructed a model to describe the optical emission from ultra-luminous X-ray sources (ULXs). We assume a binary model with a black hole accreting matter from a Roche lobe filling companion star. We consider the effects of…
The nature of ultra-luminous X-ray sources (ULXs) has long been plagued by an ambiguity about whether the central compact objects are intermediate-mass (IMBH, >~ 10^3 M_sun) or stellar-mass (a few tens M_sun) black holes (BHs). The high…