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We present a spectral-timing analysis of two NICER observations of the weakly magnetized neutron star low-mass X-ray binary Cygnus X-2. During these observations, we detect a rapid transition from a narrow 50-Hz horizontal-branch…
This paper presents a comprehensive study of the fundamental quasinormal modes of all Standard Model fields propagating on a brane embedded in a higher-dimensional rotating black hole spacetime. The equations of motion for fields with spin…
We present the first broadband spectral and timing study of the Be/X-ray pulsar XTE J0111.2$-$7317 (SXP31.0) during the first major outburst since its discovery in 1998. This giant type II outburst, observed between April and September…
We present an analysis of the long RXTE observation of the Seyfert~1 galaxy MCG-6-30-15, taken in July 1997. Our results show that the behaviour is complicated. We find clear evidence from colour ratios and direct spectral fitting that…
We present the results of a 30ks XMM-Newton observation of the supergiant fast X-ray transient (SFXT) SAX J1818.6-1703 - the first in-depth soft X-ray study of this source around periastron. INTEGRAL observations shortly before and after…
We present a timing analysis of threeRossi X-ray Timing Explorer observations of the black hole binary Cygnus X-1 with the propagating mass accretion rate fluctuations model PROPFLUC. The model simultaneously predicts power spectra, time…
We report on the X-ray spectral (using XMM-Newton data) and timing behavior (using XMM-Newton and Rossi X-ray Timing Explorer [RXTE] data) of the very faint X-ray transient and black hole system Swift J1357.2-0933 during its 2011 outburst.…
Black hole binaries exhibit dramatic changes in their X-ray spectral and timing properties over time, providing important clues about the physical processes that occur in these systems. Black holes and black hole candidates are prime…
We report results of Swift observations for the high mass Be/X-ray binary system 1A 1118-615, during an outburst stage in January, 2009 and at a flaring stage in March, 2009. Using the epoch-folding method, we successfully detected a pulsed…
Aims: Flip-flops are top-hat-like X-ray flux variations which occur in some transient accreting black hole binary systems and feature simultaneous changes in the spectral hardness and the Power Density Spectrum (PDS). They occur at a…
We report on the detection of optical/near-infrared (O-IR) quasi-periodic oscillations (QPOs) from the black hole X-ray transient Swift J1727.8-1613. We obtained three X-ray and O-IR high-time-resolution observations of the source during…
During an XMM-Newton observation, the eclipsing polar UZ For was found in a peculiar state with an extremely low X-ray luminosity and occasional X-ray and UV flaring. For most of the observation, UZ For was only barely detected in X-rays…
The RXTE observations of Scorpius X-1 in 1996-1999 are presented. The properties of its quasi-periodic X-ray oscillations are studied in detail. The results obtained are used for analysis in terms of the transition-layer model (TLM) and the…
We report on INTEGRAL observations performed during the 2004 outburst of the bright black hole transient GX 339-4. We analysed IBIS and JEM-X public data starting on 9th August and lasting about one month. During this period GX 339-4 showed…
Black hole X-ray binaries display significant stochastic variability on short time-scales (0.01-100 seconds), with a complex pattern of lags in correlated variability seen in different energy bands. This behaviour is generally interpreted…
The superorbital period of LMC X-4 is among the most stable known in Roche-lobe overflow, high-mass X-ray binaries. We analyzed 33 years of monitoring data from the Compton Gamma Ray Observatory Burst and Transient Source Experiment (CGRO…
Sco X-1 is the archetypal low mass X-ray binary (LMXB) and the brightest persistent extra-solar X-ray source in the sky. It was included in the K2 Campaign 2 field and was observed continuously for 71 days with 1 minute time resolution. In…
The Rossi X-Ray Timing Explorer (RXTE) has found that the neutron stars in low-mass X-ray binaries exhibit oscillations in the range 300-1200 Hz. Persistent emission may exhibit one or both of two features. In bursts a nearly coherent…
The rms (root mean square) variability is the parameter for understanding the emission temporal properties of X-ray binaries (XRBs) and active galactic nuclei (AGN). The rms-flux relation with Rossi X-ray Timing Explorer (RXTE) data for the…
We present results of our analysis of a set of RXTE/PCA observations of X-ray flares/bursts with burst cycle ranging from 30 to 1300 s from the Galactic X-ray transient source GRS 1915+105 during last four years. These flares/bursts can be…