Related papers: Orbital decay in M82 X-2
The nature of the 5-12 s "anomalous" X-ray pulsars remains a mystery. Among the models that have been proposed to explain the properties of AXPs, the most likely ones are: (1) isolated accreting neutron stars evolved from the…
Ultraluminous X-ray sources (ULXs) represent an extreme class of accreting compact objects: from the identification of some of the accretors as neutron stars to the detection of powerful winds travelling at 0.1-0.2 c, the increasing…
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 the identification of a recurrent ultraluminous X-ray source (ULX), a highly absorbed X-ray source (possibly a background AGN), and a young supernova remnant near the center of the starburst galaxy M82. From a series of Chandra…
Ultraluminous X-ray sources (ULXs) are X-ray binary systems containing an accreting neutron star (NS) or black hole emitting at luminosities above the Eddington limit of a $10M_{\odot}$ black hole. Approximately 1900 (either confirmed or…
We report on the discovery of a new, transient ultraluminous X-ray source (ULX) in the galaxy NGC 7090. This new ULX, which we refer to as NGC 7090 ULX3, was discovered via monitoring with $Swift$ during 2019-20, and to date has exhibited a…
Recently the first finding of a spin period of an accreting neutron star in M31 is reported. The observed spin period is 1.2 s and it shows 1.27 d modulations due to orbital motion. From the orbital information, the mass donor could not be…
SwiftJ0243.6+6124, the first Galactic ultra-luminous X-ray pulsar, was observed during its 2017-2018 outburst with \emph{AstroSat} at both sub- and super-Eddington levels of accretionwith X-ray luminosities of $L_{X}{\sim}7{\times}10^{37}$…
Possible manifestations of accreting magnetars are discussed. It is shown that the four ultra-luminous X-ray pulsars can be understood in the accreting low magnetic field magnetar scenario. The NGC300 ULX1 pulsar may have a higher dipole…
We discuss properties of the ultra-luminous $X$-ray source in the galaxy M82, NuSTAR J095551+6940.8, containing an accreting neutron star. The neutron star has surface magnetic field $ B_{NS} \approx 1.4 \times 10^{13 } \, {\rm G}$ and…
We report on NuSTAR observations of transient pulsations in the neutron star X-ray binary SMC X-1. The transition from non-pulsing to pulsing states was not accompanied by a large change in flux. Instead, both pulsing and non-pulsing states…
Two \textit{NuSTAR} observations of the luminous X-ray pulsar LMC X-4 in October and November 2015 captured several bright accretion flares from this source, which has a long history of stable pulse and superorbital behavior. We present a…
It is expected that extreme mass accretion rate onto strongly magnetised neutron star results in appearance of accretion columns above stellar surface. For a distant observer, rotation of a star results in periodic variations of X-ray flux.…
Ultra-luminous X-ray sources (ULXs) with apparent luminosities up to 100's of times the Eddington luminosity for a neutron star have been discovered in external galaxies. The existence of intermediate mass black holes has been proposed to…
The outbursts of low mass X-ray binaries are prolonged relative to those of dwarf nova cataclysmic variables as a consequence of X-ray irradiation of the disc. We show that the time-scale of the decay light curve and its luminosity at a…
NGC 300 ULX1 is a pulsating ultraluminous X-ray source (PULX) with the longest spin period of $P\simeq31.6\,\rm s$ and a high spin-up rate of $\dot P\simeq5.56\times10^{-7}\,\rm s\,s^{-1}$ that is ever seen in the confirmed PULXs. In this…
Ultra-luminous X-ray sources are usually believed to be black holes with mass about $10^{2-3}M_{\odot}$. However, the recent discovery of NuSTAR J095551+6940.8 in M82 by Bachetti et al. shows that it holds the spin period $P=1.37\rm\,s$ and…
There are two proposed explanations for ultraluminous X-ray sources (ULXs) with luminosities in excess of $10^{39}$ erg s$^{-1}$. They could be intermediate-mass black holes (more than 100-1,000, solar masses, $M_\odot$) radiating at…
We report on our search for the optical counterparts of two ultraluminous X-ray pulsars with known orbital periods, M82 X-2 and NGC 5907 X-1, in new and archival HST observations, in an effort to characterize the donor stars in these…
Ultra-luminous X-ray sources (ULXs) are the most extreme members of the X-ray binary population, exhibiting X-ray luminosities that can surpass the 10^39 erg/s threshold (by orders of magnitude). They are mainly seen in external galaxies…