Related papers: Spectral States and Evolution of Ultraluminous X-r…
We report X-ray spectral variability in an ultraluminous X-ray source NGC 1042 ULX1, using archival XMM-Newton and recent NuSTAR observations. In long-term evolution, the source has shown a trend of variation in spectral hardness. The…
X-ray spectral state transitions are a key signature of black hole X-ray binaries and follow a well-defined pattern. We examined 12 XMM-Newton observations of the nearby spiral galaxy NGC 1313, which harbors two compact ultraluminous X-ray…
We present the results of high-quality XMM-NEWTON observations of a ULX in the galaxy NGC 4190. The detection of spectral cutoff in NGC 4190 ULX1 spectra rules out the interpretation of the ULX to be in a standard low/hard canonical…
We present a comprehensive spectro-temporal analysis of five ultraluminous X-ray sources (ULXs) with central object likely being a black hole, using archival {\it XMM-Newton} observations. These sources, namely NGC 1313 X-1, NGC 5408 X-1,…
We report the results of spectral and temporal variability studies of the ultraluminous X-ray sources (ULXs) contained within the interacting pair of galaxies NGC 4485/4490, combining Chandra and XMM-Newton observations. Each of the four…
We select a sample of nearby Ultraluminous X-ray sources with long XMM-Newton observations and analyse all the available XMM-Newton data using both X-ray spectral fitting techniques and hardness-intensity diagrams. The sample includes IC…
We study spectral variability of 11 ultraluminous X-ray sources (ULX) using archived XMM-Newton and Chandra observations. We use three models to describe the observed spectra; a power-law, a multi-colour disk (MCD) and a combination of…
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}…
Aims. We analyzed multi-epoch X-ray data of the Ultraluminous X-ray source (ULX) NGC 5055 X-1, with luminosity up to $2.32\times10^{40}\ \rm erg\ s^{-1}$, in order to constrain the physical parameters of the source. Methods. We performed…
We study spectral variability of 11 ultraluminous X-ray sources (ULX) using archived XMM-Newton and Chandra observations. We use three models to describe the observed spectra: a power-law, a multi-colour disc (MCD) and a combination of…
We present the results of two XMM-Newton observations of the ultraluminous X-ray source (ULX) NGC 5204 X-1. The EPIC spectra are well-fit by the standard spectral model of a black-hole X-ray binary, comprising a soft multi-colour disc…
The ultra-luminous X-ray (ULX) source ESO 243-49 HLX-1 currently provides the strongest evidence for the existence of intermediate mass black holes. We conduct an ongoing monitoring campaign with the Swift X-ray Telescope and found that…
It is thought that ultraluminous X-ray sources (ULXs) are mainly powered by super-Eddington accreting neutron stars or black holes as shown by recent discovery of X-ray pulsations and relativistic winds. This work presents a follow up study…
M82 hosts two well-known ultraluminous X-ray sources (ULXs). X-1, an intermediate-mass black hole (IMBH) candidate, and X-2, an ultraluminous X-ray pulsar (ULXP). Here we present a broadband X-ray spectral analysis of both sources based on…
We examined X-ray spectral and timing properties of ultraluminous X-ray sources (ULXs) in nearby galaxies in XMM-Newton archival data. There appear to be three distinct classes of spectra. One class shows emission from hot, diffuse plasma.…
We report the X-ray data analysis of two transient ultraluminous X-ray sources (ULXs, hereafter X1 and X2) located in the nearby galaxy NGC 7090. While they were not detected in the 2004 XMM-Newton and 2005 Chandra observations, their…
Using the X-ray data taken with ASCA, a detailed analysis was made of intensity and spectral variations of three ultra-luminous extra-galactic compact X-ray sources (ULXs); IC 342 source 1, M81 X-6, and NGC 1313 source B, all exhibiting…
Most ultra-luminous X-ray sources (ULXs) are now thought to be powered by stellar-mass compact objects accreting at super-Eddington rates. While the discovery of evolutionary cycles have marked a breakthrough in our understanding of the…
Two {\it ASCA} observations were made of two ultra-luminous compact X-ray sources (ULXs), Source 1 and Source 2, in the spiral galaxy IC 342. In the 1993 observation, Source 2 showed a 0.5--10 keV luminosity of $6 \times 10^{39}$ ergs…
A number of ultraluminous X-ray sources (ULXs) are physically associated with extragalactic globular clusters (GCs). We undertake a systematic X-ray analysis of eight of the brightest of these sources. We fit the spectra of the GC ULXs to…