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We present the results of XMM-Newton X-ray observations of the Mira AB binary system, which consists of a pulsating, asymptotic giant branch primary and nearby (~0.6'' separation) secondary of uncertain nature. The EPIC CCD (MOS and pn)…

We investigated the long-term behaviour in X-rays of the colliding wind binary WR 25, using archival data obtained with Suzaku, Swift, XMM-Newton, and NuSTAR spanning over ~16 years. Our analysis reveals phase-locked variations repeating…

To constrain the origin of the soft X-ray excess phenomenon seen in many active galactic nuclei, the intensity-correlated spectral analysis, developed by Noda et al. (2011b) for Markarian 509, was applied to wide-band (0.5-45 keV) Suzaku…

We have reanalysed the ASCA X-ray spectrum of the bright symbiotic star CH Cyg, which exhibits apparently distinct hard and soft X-ray components. Our analysis demonstrates that the soft X-ray emission can be interpreted as scattering of…

OAO 1657-415 is an accreting pulsar in an eclipsing binary system. We analyzed the INTEGRAL core program observations of this object and obtained the eclipse light curve in the soft gamma-ray band between 15 and 40 keV. We note that the…

We used 13 years of Swift/BAT observations to probe the nature and origin of hard X-ray (14-195 KeV) emission in Centaurus A. Since the beginning of the Swift operation in 2004, significant X-ray variability in the 14-195 KeV band is…

We report the variable X-ray emission from BL Lacertae detected in the ASCA ToO observation conducted during the EGRET and RXTE pointings, coincident with the 1997 July outburst. The source showed a historically high state of X-ray,…

We have analyzed {\it Rossi} X-ray timing explorer (RXTE) pointed observations of the outbursts of black hole and neutron star soft X-ray transients in which an initial low/hard state or `island' state, followed by a transition to a softer…

We present the first {\it XMM-Newton} observation of the classical supergiant high-mass X-ray binary XTE J1855$-$026 taken entirely during the eclipse of the neutron star (NS), covering the orbital phases $\phi= 0.00-0.11$. The analysis of…

Irradiation effects in close binaries are crucial for a reliable determination of system parameters and understanding the close binary evolution. We study irradiated light originating from the low mass component of an eclipsing system…

Five on-plane regions within +/- 0.8deg of the Galactic center were observed with the Hard X-ray Detector (HXD) and the X-ray Imaging Spectrometer (XIS) onboard Suzaku. From all regions, significant hard X-ray emission was detected with…

CH Cygni is a symbiotic star consisting of an M giant and an accreting white dwarf, which is known to be a highly variable X-ray source with a complex, two-component, spectra. Here we report on two Suzaku observations of CH Cyg, taken in…

We report on the X-ray observations of the eclipsing polar HY Eri (RX J0501-0359), along with its photometric, spectrophotometric, and spectropolarimetric optical variations, collected over 30 years. With an orbital period of 2.855 h, HY…

We analyse two ASCA observations of the highly eccentric O9III + B1III binary Iota Orionis obtained at periastron and apastron. Based on the assumption of a strong colliding winds shock between the stellar components, we expected to see…

Stellar evolutionary models predict that most of the early type subdwarf stars in close binary systems have white dwarf companions. More massive companions, such as neutron stars or black holes, are also expected in some cases. The presence…

We explore XMM-{\it Newton} observations of the eclipsing super-soft X-ray source CAL~87 in order to map the accretion structures of the system. { Indirect imaging techniques were applied in X-ray light curves to provide eclipse maps}. The…

We present the results of detailed analysis of pointed X-ray observations by RXTE PCA/HEXTE of the black hole X-ray binary (BHXRB) system V4641 Sgr (= SAX J1819.3-2525) during its outburst of August 2003. Soft X-ray (3-20 keV) flux…

We present the results from analyses of Suzaku observations of the supergiant X-ray binaries IGR J16207-5129 and IGR J17391-3021. For IGR J16207-5129, we provide the first broadband (0.5--60 keV) spectrum from which we confirm a large…

(Abridged) We present results of several X-ray observations of the X-ray binary 4U 1954+31 performed with the satellites BeppoSAX, EXOSAT, ROSAT, RXTE, and Swift. We also studied the RXTE ASM data over a period of more than 10 years. Light…

Advances in the capabilities of X-ray, gamma-ray and TeV telescopes have brought new information on the physics of relativistic jets, which are responsible for the blazar "phenomenon". In particular the broad band sensitivity of the…