Related papers: The Be/X-ray binary LS 992/RX J0812.4-3114: physic…
IGR J06074+2205 is a poorly studied X-ray source with a Be star companion. It has been proposed to belong to the group of Be/X-ray binaries. In Be/X-ray binaries, accretion onto the neutron star occurs via the transfer of material from the…
SXP4.78 was originally discovered in 2000 as a pulsar in the Small Magellanic Cloud (SMC) by the Rossi X-ray Timing Explorer (RXTE) but it was not spatially located at that time. A new detection in 2018 with the Neil Gehrels Swift…
We carry out a dedicated study of 3XMM J181923.7$-$170616\ with an approximate pulsation period of 400~s using the XMM-Newton and Swift observations spanning across nine years. We have refined the period of the source to 407.904(7) s (at…
The long-period ($P = 1091$ s) of the recently discovered pulsar GLEAM-X J162759.5-523504.3 can be attained by neutron stars evolving with fallback discs and magnetic dipole moments of a few $10^{30}$ G cm$^3$ at ages greater than $\sim 2…
One of the goals of the XMM-Newton survey of the Small Magellanic Cloud is the study of the Be/X-ray binary population. During one of our first survey observations a bright new transient - XMMUJ004814.0-732204 - was discovered. We present…
The high-mass X-ray binary RX J0146.9+6121, with optical counterpart LS I+61 235 (V831 Cas), is an intriguing system on the outskirts of the open cluster NGC 663. It contains the slowest X-ray pulsar known with a pulse period of around…
We present an analysis of new spectroscopic observations of the bright Be star kappa Dra obtained at the Ondrejov observatory during 1992 - 2003 and UBV photometric observations secured at several observatories. The fundamental stellar…
The nature of the X-ray source RX J1914+24 has been the subject of much debate. It shows a prominent period of 569 sec in X-rays and the optical/infra-red: in most models this has been interpreted as the binary orbital period. We present…
We report on optical and RXTE observations of a new high-latitude bursting X-ray transient, XTE J2123-058. We identified the optical counterpart, measured the 5.9573 hr orbital period and constrained the binary inclination and the source…
We report on the first spectral and timing characterization of the transient X-ray source 1RXS J194211.9+255552 using all available data from the Swift X-ray satellite. We used 10 years of hard X-ray data from the Burst Alert Telescope…
Be stars possess gaseous circumstellar disks that modify in many ways the spectrum of the central B star. Furthermore, they exhibit variability at several timescales and for a large number of observables. Putting the pieces together of this…
We report on a long-term optical monitoring of the neutron star X-ray binary Centaurus X-4 performed during the last 13.5 years. This source has been in quiescence since its outburst in 1979. Our monitoring reveals the overall evolution of…
We obtained new optical observations of the X-ray source XMMU J083850.38-282756.8, the previously proposed counterpart of the gamma-ray source 3FGL J0838.8-2829. Time-series photometry in the $r'$ band reveals periodic modulation of…
The majority of massive classical Be stars are thought to be binary interactions products. Their rapid rotation and often strong, variable, and emission-line dominated spectrum, make spectroscopic analysis challenging. Hence, robust binary…
KS 1947+300 is a Be/X-ray binary. Despite its nearly circular orbit, it displays both giant and regular less intense X-ray outbursts. According to the viscous decretion disk model, such low eccentric binaries should not show periodic…
A significant number of X-ray binaries are now known to exhibit long-term ``superorbital'' periodicities on timescales of $\sim$ 10 - 100 days. Several physical mechanisms have been proposed that give rise to such periodicities, in…
We report on X-ray and TeV gamma-ray observations of the pulsar/Be star binary PSR J2032+4127/MT91 213. PSR J2032+4127 is a 143-ms gamma-ray pulsar which shares a long period (45-50 year) and highly eccentric orbit with the massive Be star…
We study the recently discovered Be/X-ray pulsar MAXI J0655--013 using the 2022 \emph{NuSTAR} observations. The paper is the first detailed study of the timing and spectral properties of the source. The pulse profiles of the pulsar vary…
After nearly a decade of quiescence, the transient Be/X-ray binary pulsar RX J0520.5-6932 underwent an outburst in 2024. We performed X-ray monitoring of the source with NICER and AstroSat near the peak of the event. Our primary objective…
We report on analysis of the poorly studied source 2RXP J130159.6-635806 at different epochs with ASCA, Beppo-SAX, XMM-Newton, and INTEGRAL. The source shows coherent X-ray pulsations at a period ~700s with an average spin up rate of about…