Related papers: NGC 300 ULX1: A test case for accretion torque the…
During a search for coherent signals in the X-ray archival data of XMM-Newton, we discovered a modulation at 1.2 s in 3XMM J004301.4+413017 (3X J0043), a source lying in the direction of an external arm of M 31. This short period indicates…
In this work we give detail consideration of the possible scenario of evolution of isolated neutron stars and determine some characteristics of X-ray pulsars from their spin period evolution (the paper containes more detailed abstract).
The hot subdwarf HD 49798 has an X-ray emitting compact companion with a spin-period of 13.2 s and a dynamically measured mass of 1.28+/-0.05 M_sun, consistent with either a neutron star or a white dwarf. Using all the available XMM-Newton…
We present the results of a 63 ks {\it Chandra} observation of the "supernova impostor" SN 2010da four months after it was first observed on 25 May 2010. We detect an X-ray source at $\sim7\sigma$ confidence coincident with the optical…
UW CrB (MS1603+2600) is a peculiar short period X-ray binary that exhibits extraordinary optical behaviour. The optical light curve shape of the system changes drastically from night to night, without any changes in overall brightness. Here…
Millisecond spinning, low magnetic field neutron stars are believed to attain their fast rotation in a 0.1-1 Gyr-long phase during which they accrete matter endowed with angular momentum from a low-mass companion star. Despite extensive…
We show that ultraluminous X-ray sources (ULXs) with coherent X-ray pulsing (PULXs) probably have neutron-star spin axes significantly misaligned from their central accretion discs. Scattering in the funnels collimating their emission and…
Observations of the X-ray pulsar 4U 2206+54, performed over a 15-year span, show its period, which is now 5555 \pm 9 s, to increase drastically. Such behavior of the pulsar can be hardly explained in the frame of traditional scenarios of…
The symbiotic X-ray binary 4U 1954+319 is a rare system hosting a peculiar neutron star (NS) and an M-type optical companion. Its ~5.4h NS spin period is the longest among all known accretion-powered pulsars and exhibited large (~7%)…
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…
A report is made on the luminosity and pulse-period evolution of the Be binary X-ray pulsar, GX 304$-$1, during a series of outbursts from 2009 to 2013 observed by MAXI/GSC, RXTE/PCA, and Fermi/GBM. In total, twelve outbursts repeated by…
We have investigated the rotational and the X-ray luminosity ($L_{\mathrm{x}}$) observations of 4U 1626--67 accumulated during the last four decades. It has been recorded that the source underwent a torque reversal twice. We have tried to…
We report on the discovery and analysis of the transient X-ray pulsar CXO/XMMU J073709.13+653544 detected in the 2004 August-October Chandra and XMM observations of the nearby spiral galaxy NGC2403. The source exhibits X-ray pulsations with…
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 report on \textit{NuSTAR} observations of the well-known wind-accreting X-ray pulsar \source\ during a strong spin-up episode that took place in January-March 2019. A high luminosity of the source in a most recent observation allowed us…
In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4s and 85.4s pulsations were…
Recently, ultraluminous X-ray source (ULX) M82 X-2 has been identified to be an accreting neutron star, which has a $P=1.37$ s spin period, and is spinning up at a rate $\dot{P}=-2.0\times 10^{-10}~\rm s\,s^{-1}$. Interestingly, its…
An expected signature of the presence of neutron stars in the population of ultraluminous X-ray sources (ULXs) are large scale changes in X-ray luminosity, as systems reach spin equilibrium and a propeller state ensues. We explore the…
We report strong evidence for a ~304-day periodicity in the spin history of the accretion-powered pulsar GX1+4 that is most probably associated with the orbital period of the system. We have used data from the Burst and Transient Source…
We report on the serendipitous discovery of a new transient in NGC 5907, at a peak luminosity of 6.4x10^{39} erg/s. The source was undetected in previous 2012 Chandra observations with a 3 sigma upper limit on the luminosity of 1.5x10^{38}…