相关论文: An Intermediate-Mass Black Hole Candidate in M51?

The ultraluminous compact X-ray sources (ULXs) generally show a curving spectrum in the 0.7--10 keV ASCA bandpass, which looks like a high temperature analogue of the disk dominated high/soft state spectra seen in Galactic black hole…

We present the first broadband 0.3-25.0 kev X-ray observations of the bright ultraluminous X-ray source (ULX) Holmberg II X-1, performed by NuSTAR, XMM-Newton and Suzaku in September 2013. The NuSTAR data provide the first observations of…

The origin of supermassive black holes (SMBH) in galaxy centers still remains uncertain. There are two possible ways of their formation - from massive ($10^5 - 10^6 M_{\odot}$) and low-mass ($100 M_{\odot}$) BH nuclei. The latter scenario…

The hyper luminous X-ray source HLX-1 in the galaxy ESO 243-49, currently the best intermediate mass black hole candidate, displays spectral transitions similar to those observed in Galactic black hole binaries, but with a luminosity…

The nature of ultraluminous X-ray sources (ULXs) -- off-nuclear extra-galactic sources with luminosity, assumed isotropic, $\gtrsim 10^{39}$ erg s$^{-1}$ -- is still debated. One possibility is that ULXs are stellar black holes accreting…

With a goal of searching for accreting intermediate-mass black holes (IMBHs), we report the results of ultra-deep Jansky VLA radio continuum observations of the cores of three Galactic globular clusters: M15, M19, and M22. We reach rms…

We have re-examined the most luminous X-ray sources in the starburst galaxy NGC 4631, using XMM-Newton, Chandra and ROSAT data. The most interesting source is a highly variable supersoft ULX. We suggest that its bolometric luminosity ~ a…

Most black hole candidates exhibit characteristic power-law like hard X-ray emission above $\sim$ 10 keV. In the {\em high state}, in which 2 -- 10 keV luminosity is relatively high, the energy index of the hard X-ray emission is usually…

The ultraluminous X-ray source (ULX), NGC 5408 X-1, is one of only 3 such objects to show a quasi-periodic oscillation (QPO) in its power spectrum. Previous analysis of this signal identified it with the well-studied type C low-frequency…

In this paper we present a comprehensive study of the mass of the intermediate mass black hole candidate HLX-1 in the galaxy ESO 243-49. We analyse the continuum X-ray spectra collected by Swift, XMM-Newton, and Chandra with the slim disc…

We report the results of a series of RXTE and ATCA observations of the recently-discovered X-ray transient IGR J17497-2821. Our 3-200 keV PCA+HEXTE spectral analysis shows very little variations over a period of ~10 days around the maximum…

We present broadband X-ray spectral study of two ultraluminous X-ray sources (ULXs), M81 X-6 and Holmberg IX X-1 based on Suzaku & XMM-Newton observations. We perform joint broadband spectral analysis of the brightest sources in the field,…

Ultra-luminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities >10^39 erg s^-1. These extreme luminosities - if the emission is isotropic and below the theoretical (i.e.…

The discovery of pulsations in (at least) six ultraluminous X-ray sources (ULXs) has shown that neutron stars can accrete at (highly) super-Eddington rates, challenging the standard accretion theories. M51 ULX-7, with a spin signal of…

We report variability of the X-ray source, X-7, in NGC 6946, during a 60 ksec Chandra observation when the count rate decreased by a factor of ~1.5 in ~5000 secs. Spectral fitting of the high and low count rate segments of the light curve…

The ultraluminous X-ray sources (ULXs) were isolated in external galaxies for the last 5 years. Their X-ray luminosities exceed 100-10000 times those of brightest Milky Way black hole binaries and they are extremely variable. There are two…

Ultraluminous X-ray sources (ULXs) are a population of extragalactic objects whose luminosity exceeds the Eddington limit for a 10 Msun black hole (BH). Their properties have been widely interpreted in terms of accreting stellar-mass or…

We present a multi-wavelenght study of the recently discovered Ultraluminous X-ray transient XMMUJ004243.6+412519 (ULX2 hereafter) in M31, based on Swift data and the 1.8-m Copernico Telescope in Asiago (Italy). Undetected until January…

The origin and nature of Ultra-Luminous X-ray sources (ULXs) is a contentious and controversial topic. There are ongoing debates about the masses of the objects responsible, their sources of mass for accretion, and their relation to stellar…

Intermediate-mass black holes (IMBHs) with masses below ($2 \times 10^5 M_{\odot}$) are pivotal in understanding the origin and growth mechanisms of supermassive black holes (SMBHs) in galactic nuclei. This study focuses on the search and…