Related papers: No magnetars in ULXs
Although ultra-luminous X-ray sources (ULX) are important for astrophysics due to their extreme apparent super-Eddington luminosities, their nature is still poorly known. Theoretical and observational studies suggest that ULXs could be a…
Ultramagnetized neutron stars or magnetars are magnetically powered neutron stars. Their strong magnetic fields dominate the physical processes in their crusts and their surroundings. The past few years have seen several advances in our…
In previous papers, we presented the discovery of a 12-s X-ray pulsar in the supernova remnant Kes 73, providing the first direct evidence for an ultramagnetized neutron star, a magnetar, with an equivalent dipole field of nearly twenty…
The presence or lack of eclipses in the X-ray lightcurves of ultraluminous X-ray sources (ULXs) can be directly linked to the accreting system geometry. In the case where the compact object is stellar mass and radiates isotropically, we…
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…
In this paper we discuss the spin-equilibrium of accreting neutron stars in LMXBs. We demonstrate that, when combined with a naive spin-up torque, the observed data leads to inferred magnetic fields which are at variance with those of…
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…
Recent evidence - in particular the hard X-ray spectra obtained by NuSTAR, and the large amplitude hard X-ray variability observed when ultraluminous X-ray sources (ULXs) show soft spectra - reveals that common ULX behaviour is inconsistent…
The launch of IXPE telescope in late 2021 finally made polarization measurements in the 2-8 keV band a reality, more than 40 years after the pioneering observations of the OSO-8 satellite. In the first two years of operations IXPE targeted…
We present the results from the high resolution Chandra observation of the Cartwheel galaxy. Many individual sources are resolved in the image, mostly associated with the outer ring. All detected sources have a very high X-ray luminosity…
It has recently been proposed that radio emission from magnetars can be evaluated using a "fundamental plane" in parameter space between pulsar voltage gap and ratio of X-ray luminosity Lx to rotational energy loss rate Edot. In particular,…
Pulsars are rapidly spinning neutron stars, that radiate at the expense of their strong magnetic field and their high surface temperature. Five decades of multi-wavelength observations showed a large variety of physical parameters, such as…
We present broadband X-ray analyses of a sample of bright ultraluminous X-ray sources with the goal of investigating the spectral similarity of this population to the known ULX pulsars, M82 X-2, NGC7793 P13 and NGC5907 ULX. We perform a…
Ultra-luminous X-ray sources (ULXs) have been puzzling us with a debate whether they consist of an intermediate mass black hole or super-Eddington accretion by a stellar mass black hole. Here we suggest that in the presence of large scale…
If the ultraluminous source (ULX) M82 X-2 sustains its measured spin-up value of $\dot \nu= 10^{-10}\,{\rm s^{-2}}$, it will become a millisecond pulsar in less than $10^5\,$ years. The observed (isotropic) luminosity of $10^{40}\,$ erg/s…
Observations of high-redshift quasars frequently promote suggestions of large black hole masses, whose presence so early in cosmic time is not easily explicable. I consider the parallel with ultraluminous X-ray sources (ULXs) -- now known…
I summarize the recent advances in our understanding of the Soft Gamma Repeaters: in particular their spin behavior, persistent emission and hyper-Eddington outbursts. The giant flares on 5 March 1979 and 27 August 1998 provide compelling…
The detection of optical/infrared counterparts to Anomalous X-ray Pulsars (AXPs) has greatly increased our understanding of these systems. Models for the AXP phenomenon were based upon their X-ray emission, and all but the magnetar model…
Ultraluminous X-ray sources (ULXs) are accreting black holes that may contain the missing population of intermediate mass black holes or reflect super-Eddington accretion physics. Ten years of Chandra and XMM-Newton observations of ULXs,…
In the current work we explore the applicability of standard theoretical models of accretion to the observed properties of M51 ULX-7. The spin-up rate and observed X-ray luminosity are evidence of a neutron star with a surface magnetic…