Related papers: A truncated accretion disk in the galactic black h…
We report the few hundred second anti-correlated soft lags between soft and hard energy bands in the source GX 339-4 using RXTE observations. In one observation, anti-correlated soft lags were observed using the ISGRI/INTEGRAL hard energy…
We present an analysis of NuSTAR observations of a hard intermediate state of the transient black hole GX 339-4 taken in January 2015. As the source softened significantly over the course of the 1.3 d-long observation we split the data into…
We analyze X-ray light curves of the blazar Mrk 421 obtained from the Soft X-ray Imaging Telescope and the Large Area X-Ray Proportional Counter instrument onboard the Indian space telescope $AstroSat$ and archival observations from…
We perform a comprehensive timing and broadband spectral analysis using an AstroSat observation of the low-mass black hole X-ray binary H~1743--322 during 2017 outburst. Additionally, we use two Swift/XRT observations, one of which is…
We study a truncated accretion disk using a well-resolved, semi-global magnetohydrodynamic simulation that is evolved for many dynamical times (6096 inner disk orbits). The spectral properties of hard state black hole binary systems and…
Observations from the Rossi X-Ray Timing Explorer have shown the existence of high frequency quasi-periodic oscillations (HFQPOs) in the X-ray flux from accreting black hole binary systems. In at least two systems, these HFQPOs come in…
We analyse the properties of the Comptonizing medium in the black-hole X-ray binary Swift J1727.8$-$1613 using the time-dependent Comptonization model vkompth, using NICER observations of type-C QPOs in the hard and hard-intermediate…
The Galactic black-hole candidate GX 339-4 exhibited several outbursts at regular intervals of \sim 2-3 years in the Rossi X-ray Timing Explorer (RXTE) era. After remaining in an almost quiescent state for 3 years, it again became X-ray…
The black hole transient H1743-322 exhibited several outbursts with temporal and spectral variability since its discovery in 1977. These outbursts occur at a quasi-regular recurrence period of around $0.5-2$ years, since its rediscovery in…
Context: Some apparently quiescent supermassive black holes (BHs) at centers of galaxies show quasi-periodic eruptions (QPEs) in the X-ray band, the nature of which is still unknown. A possible origin for the eruptions is an accretion disk,…
It has long been proposed that low frequency QPOs in stellar mass black holes or their equivalents in super massive black holes are results of resonances between infall and cooling time scales. We explicitly compute these two time scales in…
We study accretion flow dynamics of Galactic transient black hole candidate (BHC) H 1743-322 during its 2010 outburst by analyzing spectral data using Two Component (Keplerian and sub-Keplerian) Advective Flow (TCAF) solution, after its…
Observations of Galactic black hole sources are traditionally done in the classical X-ray range (2 -- 10 keV) due to sensitivity constraints. Most of the accretion power, however, is radiated above 10 keV and the study of these sources in…
The evolution of the C-type low frequency quasi-periodic oscillations (LFQPOs) and associated time lag in transient black hole sources as a function of time can be explained by variation of the Compton cloud size in a Two Component…
Accreting stellar-mass black holes often show a `Type-C' quasi-periodic oscillation (QPO) in their X-ray flux, and an iron emission line in their X-ray spectrum. The iron line is generated through continuum photons reflecting off the…
The nature of accretion onto stellar mass black holes in the low/hard state remains unresolved, with some evidence suggesting that the inner accretion disc is truncated and replaced by a hot flow. However, the detection of relativistic…
Simultaneous multiwavelength observations were recently performed for three black hole candidates --- SWIFT J1753.5-0127, GRO J1655-40 and XTE J1720-318. In this paper we test the accretion-jet model originally proposed to XTE J1118+480 by…
We present a variability study of the black hole candidate and X-ray transient H1743-322 during its 2003/2004 outburst. We analyzed five Rossi X-ray Timing Explorer observations that were performed as part of a multi-wavelength campaign, as…
We have performed a spectral-timing analysis on the black hole X-ray binary MAXI J1535--571 during its 2017 outburst, with the aim of exploring the evolution of the inner accretion flow geometry. X-ray reverberation lags are observed in the…
We present two observational campaigns performed with the RXTE satellite on the black hole transient H 1743-322. The source was observed in outburst on two separate occasions between October-November 2008 and May-July 2009. We have carried…