Related papers: Fourier time lags in the dwarf nova SS Cygni
The UV/optical variations in many AGN are very well correlated, showing delays which increase with increasing wavelength. It is thought that this is due to thermal reprocessing of the X-ray emission by the accretion disk. In this scenario,…
We present the results of hard-X-ray observations of four broad-line radio galaxies (BLRGs) with the Rossi X-Ray Timing Explorer (RXTE). The original motivation behind the observations was to search for systematic differences between the…
XMM-Newton X-ray spectra of the hard state Black Hole X-Ray Binaries (BHXRBs) SWIFT J1753.5-0127 and GX 339-4 show evidence for accretion disc blackbody emission, in addition to hard power-laws. The soft and hard band Power-Spectral…
Recent results are presented and discussed regarding the EUV and X-ray emission of nonmagnetic cataclysmic variables. Emphasis is given to high accretion rate systems (novalike variables and dwarf novae in outburst), and to a number of…
We present a detailed multi-frequency analysis of an intense monitoring programme of Seyfert 1 galaxy NGC 4593 over a duration of nearly for a month with Swift observatory. We used 185 pointings to study the variability in six…
The black-hole binary, V404 Cygni, went into outburst in June 2015, after 26 years of X-ray quiescence. We observed the outburst with the Neil Gehrels Swift observatory. We present optical/UV observations taken with the Swift Ultra-violet…
Active galactic nuclei (AGN) have been observed to vary stochastically with 10-20 rms amplitudes over a range of optical wavelengths where the emission arises in an accretion disk. Since the accretion disk is unlikely to vary coherently,…
Black hole X-ray binaries in their hard and hard-intermediate states display hard and soft time lags between broadband noise variations (high-energy emission lagging low-energy and vice versa), which could be used to constrain the geometry…
The X-ray emission from active galactic nuclei (AGN) is highly variable. Measurements of time lags (characterised by lag spectra) between variability in the light curves in energy bands corresponding to directly observed continuum emission…
AM CVn systems are a rare type of cataclysmic variable star consisting of a w hite dwarf accreting material from a low-mass, hydrogen-poor donor star. These helium-rich systems usually have orbital periods that are less than 65 minutes an d…
Emission from Active Galactic Nuclei is known to vary strongly over time over a wide energy band, but the origin of the variability and especially of the inter-band correlations is still not well established. Here we present the results of…
We present soft X-ray variability time-scales for 65 active galactic nuclei (AGNs) derived from ROSAT/PSPC pointing data. For these 65 objects with obvious exponential increasing or decreasing patterns in their light curves, we use the…
We present a 140ks observation of NGC 4593 with XMM-Newton providing simultaneous and continuous PN X-ray and OM UV (UVW1 2910\AA) lightcurves which sample short-timescale variations better than previous observations. These observations…
X-ray reverberation in Active Galactic Nuclei, believed to be the result of the reprocessing of coronal photons by the underlying accretion disc, has allowed us to probe the properties of the inner-most regions of the accretion flow and the…
We analyse the X-ray time-lags in the Narrow Line Seyfert 1 (NLS1) galaxy PG 1244+026 ($M_{\rm BH}\sim 10^7 M_{\rm sun}$, $L/L_{\rm Edd}\sim 1$). The time delay between the soft (0.3--0.7~keV) and harder (1.2--4.0~keV) variations shows…
We study multi-wavelength variability of a bare Seyfert 1 galaxy Fairall~9 using \swift{} monitoring observations consisting of $165$ usable pointings spanning nearly two years and covering six UV/optical bands and X-rays. Fairall~9 is…
We present a unified model for optical, ultraviolet (UV), and X-ray light curves of V1974 Cygni (Nova Cygni 1992). Based on an optically thick wind model of nova outbursts, we have calculated light curves and searched for the best fit model…
We have carried out a timing analysis of Cyg X-1 and GRS 1915+105 using more than 5 years worth of data from the All Sky Monitor (ASM) on board RXTE. We have obtained for the first time power density spectra, colour-colour and…
MCG-6-30-15 is one of the most observed Narrow Line Seyfert 1 galaxies in the X-ray band. In this paper we examine the X-ray time lags in this source using a total of 600 ks in observations (440 ks exposure) taken with the XMM-Newton…
We present a new release of the RELTRANS model to fit the complex cross-spectrum of accreting black holes as a function of energy. The model accounts for continuum lags and reverberation lags self-consistently in order to consider the…