Related papers: Intermediate Mass Black Holes in Accreting Binarie…

MAXI J1305-704 has been proposed as a high-inclination candidate black hole X-ray binary in view of its X-ray properties and dipping behaviour during outburst. We present photometric and spectroscopic observations of the source in…

Distinguishing the photon output of an accreting supermassive black hole binary system from that of a single supermassive black hole accreting at the same rate is intrinsically difficult because the majority of the light emerges from near…

We consider observational tests for the nature of Ultraluminous X-ray sources (ULXs). These must distinguish between thermal-timescale mass transfer on to stellar-mass black holes leading to anisotropic X-ray emission, and accretion on to…

Periodic pulsations have been found in emission from the ultra-luminous X-ray source (ULX) M82 X-2, strongly suggesting that the emitter is a rotating neutron star rather than a black hole. However, the radiation mechanisms and accretion…

We report the discovery of the transient ultraluminous X-ray source (ULX) CXOU J122602.3+125951 (hereafter M86 tULX-1), located 3'52" (19 kpc) northwest of the centre of the giant elliptical galaxy M86 (NGC 4406) in the Virgo Cluster. The…

We present X-ray properties of optically-selected intermediate-mass (~10^5--10^6 M_Sun) black holes (BHs) in active galaxies (AGNs), using data from the Chandra X-Ray Observatory. Our observations are a continuation of a pilot study by…

We report results from a spectral and timing analysis of M82 X-1, one of the brightest known ultraluminous X-ray sources. Data from a new 105 ks {\it XMM-Newton} observation of M82 X-1, performed in April 2004, and of archival {\it…

The compact X-ray source in the eclipsing X-ray binary IC 10 X-1 has reigned for years as ostensibly the most massive stellar-mass black hole, with a mass estimated to be about twice that of its closest rival. However, striking results…

We model the intermediate-mass black hole HLX-1, using the Hubble Space Telescope, XMM-Newton and Swift. We quantify the relative contributions of a bluer component, function of X-ray irradiation, and a redder component, constant and likely…

There is a lot of current astrophysical evidence and interest in intermediate mass black holes, ranging from a few hundred to several thousand solar masses. The active galaxy M82 and the globular cluster in M31, for example, are known to…

Hyper-luminous X-ray sources (HLXs; L_X>10^41 erg s^-1) are off-nuclear X-ray sources in galaxies and strong candidates for intermediate-mass black holes (IMBHs). We have constructed a sample of 169 HLX candidates by combining X-ray…

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…

We present a Chandra and HST study of IC 10 X-1, the most luminous X-ray binary in the closest starburst galaxy to the Milky Way. Our new hard X-ray observation of X-1 confirms that it has an average 0.5-10 keV luminosity of 1.5e38 erg/s,…

With an inferred bolometric luminosity exceeding 10^42 erg/s, HLX-1 in ESO 243-49 is the most luminous of ultraluminous X-ray sources and provides one of the strongest cases for the existence of intermediate mass black holes. We obtain good…

Ultraluminous X-ray sources (ULXs) are likely to include different physical types of objects. We discuss some possible subclasses, reviewing the properties of a sample of ULXs recently observed by Chandra and XMM-Newton. Sources with an…

Two X-ray sources were recently discovered by Irwin et al. in compact companions to elliptical galaxies to show ultra-luminous flares with fast rise (~ minute) and decay (~ hour), and with a peak luminosity ~10^{40-41} erg/s. Together with…

Chandra observations of the Cartwheel galaxy reveal a population of ultraluminous X-ray sources (ULXs) with lifetimes < 10^7 yr associated with a spreading wave of star formation which began some 3 x 10^8 yr ago. A population of high-mass…

The observations and theory of the exciting new class of galactic black hole X-ray transients is reviewed. Seven of these systems have measured mass functions or mass estimates in excess of stable neutron stars, making them excellent black…

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…

We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected…