Related papers: Ultra Luminous X-ray sources - new distance indica…

The classical limit on the accretion luminosity of a neutron star is given by the Eddington luminosity. The advanced models of accretion onto magnetized neutron stars account for the appearance of magnetically confined accretion columns and…

Unidentified extreme UV sources, detected in the {\it EUVE} and {\it ROSAT} WFC all-sky surveys, could be isolated old neutron stars, accreting material from the ISM. The closest neutron stars, that are located in the local ISM bubble of…

We analyse four XMM-Newton observations of the neutron-star low-mass X-ray binary EXO 0748$-$676 in quiescence. We fit the spectra with an absorbed neutron-star atmosphere model, without the need for a high-energy (power-law) component;…

We observed the main core F of the rho Ophiuchi cloud, an active star-forming region located at ~140 pc, using XMM-Newton with an exposure of 33 ks. We detect 87 X-ray sources within the 30' diameter field-of-view of the it EPIC imaging…

In this paper we report accurate Chandra positions for two ultraluminous X-ray sources: NGC 7319-X4 at Right Ascension (RA) = 339.02917(2) deg, Declination (Dec) = 33.97476(2) deg and NGC 5474-X1 at RA = 211.24859(3) deg, Dec = 53.63584(3)…

We present the first survey results of hard X-ray point sources in the Galactic Center (GC) region by NuSTAR. We have discovered 70 hard (3-79 keV) X-ray point sources in a 0.6 deg^2 region around Sgr A* with a total exposure of 1.7 Ms, and…

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…

(Abridged) We report the results of a 20 ks Chandra ACIS-S observation of the interacting galaxy pair NGC 4485/4490. A total of 29 discrete X-ray sources are found coincident with NGC 4490, but only one is found within NGC 4485. The sources…

We present the discovery, from archival Chandra and XMM-Newton data, of X-ray eclipses in two ultraluminous X-ray sources (ULXs), located in the same region of the galaxy M 51: CXOM51 J132940.0$+$471237 (ULX-1, for simplicity) and CXOM51…

We present a summary of our ongoing efforts to study one of the brightest ultraluminous X-ray source, NGC 1313 X-2. Despite a large coverage in the X-rays, much of the information we have about the source and its environment comes from…

Eddington-limited X-ray bursts from neutron stars can be used in conjunction with other spectroscopic observations to measure neutron star masses, radii, and distances. In order to quantify some of the uncertainties in the determination of…

We present results from three nearly simultaneous NuSTAR and Chandra monitoring observations between 2012 Sep 2 and 2012 Nov 16 of local star-forming galaxy NGC 253. The 3-40 keV NuSTAR intensity of the inner 20 arcsec (~400 pc) nuclear…

We present optical and X-ray data for a sample of serendipitous XMM-Newton sources that are selected to have 0.5-2 keV vs 2-4.5 keV X-ray hardness ratios which are harder than the X-ray background. The sources have 2-4.5 keV X-ray flux >=…

We have used a set of dedicated astrometric data from the Hubble Space Telescope to measure the parallax and proper motion of the nearby neutron star RX J0720.4-3125. At each of eight epochs over two years, we used the High Resolution…

We present XMM-Newton X-ray observations of the interacting galaxy pairs NGC7771/7770 and NGC2342/2341. In NGC7771, for the first time we are able to resolve the X-ray emission into a bright central source (L(X)~10^41 erg/s), plus two…

We identify sources with extremely hard X-ray spectra (i.e., with photon indices of Gamma<0.6 in the 13 sq. deg. NuSTAR serendipitous survey, to search for the most highly obscured AGNs detected at >10 keV. Eight extreme NuSTAR sources are…

We analyze the X-ray scattering halos around three Galactic Anomalous X-ray Pulsars (AXPs) in order to constrain the distance and the optical extinction of each source. We obtain surface brightness distributions from EPIC-pn data obtained…

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…

We presented the result of a high resolution (FWHM~0.5'') 12 ks Chandra HRC-I observation of the starburst galaxy IC342 taken on 2 April 2006. We identified 23 X-ray sources within the central 30' x 30' region of IC342. Our HRC-I…

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…