Related papers: Spectral variability in NGC 1042 ULX1

RX J1140.1+0307 (hereafter RX1140) is a Narrow Line Seyfert 1 (NLS1) with one of the lowest black hole masses known in an AGN (M ${\le} 10^6$ M$_{\odot}$). We show results from two new {\it XMM-Newton} observations, showing soft 2-10~keV…

Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework…

Nearby galaxies host ultra-luminous X-ray sources (ULXs), whose nature remains largely unknown. Until the discovery of the first ULX pulsar, M82 X-2, the mechanism powering the large luminosities of most ULXs was thought to be…

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…

We report on Chandra observations of the bright ultra-luminous X-ray (ULX) source in NGC3921. Previous XMM observations reported in the literature show the presence of a bright ULX at a 0.5-10 keV luminosity of 2x10^40 erg/s. Our Chandra…

ULX-7, in the northern spiral arm of M51, demonstrates unusual behaviour for an ultraluminous X-ray source, with a hard X-ray spectrum but very high short-term variability. This suggests that it is not in a typical ultraluminous state. We…

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…

We present results from four new broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 ($L_{\rm{X}} > 10^{40}$ erg/s), performed by $Suzaku$ and $NuSTAR$ in coordination. Combined with the archival data, we…

We present the results of optical panoramic and long-slit spectroscopy of the nebula MF16 associated with the Ultraluminous X-ray Source NGC6946 ULX-1. More than 20 new emission lines are identified in the spectra. Using characteristic line…

We present the long-term spectral evolution of eight black hole ultra-luminous X-ray sources (BH-ULXs), namely NGC1313 X-1, NGC5408 X-1, NGC6946 X-1, IC342 X-1, NGC55 ULX1, NGC4395 ULX1, NGC5204 X-1 and NGC4190 ULX1 using {\it XMM-Newton}…

We present an analysis of recent XMM-Newton and HST archive data of the ultraluminous X-ray source NGC 1313 X-2. Quasi-simultaneous observations taken with XMM-Newton, HST and VLT allow us to study both the X-ray light curve and its…

Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a…

Ultraluminous X-ray sources (ULXs) are extragalactic X-ray emitters located off-center of their host galaxy and with a luminosity in excess of a few ${10^{39}\text{ erg s}^{-1}}$, if emitted isotropically. The discovery of periodic…

Soft, potentially thermal spectral components observed in some ULXs can be fit with models for emission from cool, optically-thick accretion disks. If that description is correct, the low temperatures that are observed imply accretion onto…

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.…

Suzaku observation of an ultraluminous X-ray source, NGC 2403 Source 3, performed on 2006 March 16--17, is reported. The Suzaku XIS spectrum of Source 3 was described with a multi-color black-body-like emission from an optically thick…

We present a systematic analysis of the X-ray spectra of NGC 1313 X-1 and NGC 1313 X-2, using three years of XMM-Newton observations. We fitted the continuum with a Comptonization model plus a multicolor blackbody disc, that describes the…

Observations of the Ultra Luminous X-ray source (ULX) Holmberg IX X-1 were carried out with Suzaku twice, once on 2012 April 13 and then on 2012 October 24, with exposures of 180 ks and 217 ks, respectively. The source showed a hard…

We present results from the spectral analysis of a long XMM-Newton observation of the radio-loud NLS1 galaxy PKS0558-504. The source is highly variable, on all sampled time scales. We did not observe any absorption features in either the…

We seek clarification of the nature of X-ray sources detected in M 31. Here we focus on CXOM31 J004253.1+411422, the brightness of which suggests that it belongs to the class of ultraluminous X-ray sources. We determine the X-ray properties…