Related papers: Comparison of Relativistic Iron Line Models
X-ray reflection spectroscopy is a powerful technique for probing the nature of gravity around black holes in the so-called strong field regime. One of the most popular of such probes is to look at theory-agnostic deviations away from the…
We present three simultaneous/quasi-simultaneous NuSTAR and Swift datasets of the black hole GRS 1716-249 in its hard intermediate state. The accretion disk in this state may have reached the innermost stable circular orbit, and the NuSTAR…
Einstein-dilaton-Gauss-Bonnet gravity is a well-motivated alternative theory of gravity that emerges naturally from string theory. While black hole solutions have been known in this theory in numerical form for a while, an approximate…
We estimate the black hole spin parameter in GRS 1915+105 using the continuum-fitting method with revised mass and inclination constraints based on the very long baseline interferometric parallax measurement of the distance to this source.…
4U 1543-47 is a low mass X-ray binary which harbours a stellar-mass black hole located in our Milky Way galaxy. In this paper, we revisit 7 data sets which were in the Steep Power Law state of the 2002 outburst. The spectra were observed by…
We analyzed simultaneous archival XMM-Newton and RXTE observations of the X-ray binary and black hole candidate Swift J1753.5-0127. In a previous analysis of the same data a soft thermal component was found in the X-ray spectrum, and the…
X-ray observations of several active galactic nuclei show prominent iron K-shell fluorescence lines that are sculpted due to special and general relativistic effects. These observations are important because they probe the space-time…
Recently, the accretion geometry of the black-hole X-ray binary Cyg X-1 was probed with the X-ray polarization. The position angle of the X-ray emitting flow was found to be aligned with the position angle of the radio jet in the plane of…
X-ray reflection spectroscopy (or iron line method) is a powerful tool to probe the strong gravity region of black holes, and currently is the only technique for measuring the spin of the supermassive ones. While all the available…
Context: Theoretical modelling of time-lags between variations in the Fe K$\alpha$ emission and the X-ray continuum might shed light on the physics and geometry of the X-ray emitting region in active galaxies (AGN) and X-ray binaries. We…
The observations and interpretation of broad iron lines in the X-ray spectra of Seyfert 1 galaxies are reviewed. The line profiles observed from MCG--6-30-15 and NGC 3516 show extended red wings to the line explained by large gravitational…
There is growing evidence from both spectral and timing properties that there is a truncated inner accretion disc in low mass accretion rate Galactic black hole systems. The detection of extremely smeared relativistic iron lines in some of…
Relativistic iron K$\alpha$ spectral emission line from the inner disc of a neutron star low-mass X-ray binary (LMXB) was first detected in 2007. This discovery opened up new ways to probe strong gravity and dense matter. The past decade…
The compact X-ray source in the eclipsing X-ray binary IC 10 X-1 has reigned for years as ostensibly the most massive stellar-mass black hole, with a mass estimated to be about twice that of its closest rival. However, striking results…
QPOs are a common feature in the X-ray power density spectrum of black hole binaries and a potentially powerful tool to probe the spacetime geometry around these objects. Here we discuss their constraining power to test the Kerr black hole…
The continuum-fitting and the iron line methods are currently the two leading techniques for probing the strong gravity region around accreting black holes. In the present work, we test the Kerr black hole hypothesis with the stellar-mass…
Astrophysical black hole systems are the ideal laboratories for testing Einstein's theory of gravity in the strong field regime. We have recently developed a framework which uses the reflection spectrum of black hole systems to perform…
We describe a program that we have embarked on to estimate the spins of stellar-mass black holes in X-ray binaries. We fit the continuum X-ray spectrum of the radiation from the accretion disk using the standard thin disk model, and extract…
Fitting the thermal continuum emission of accreting black holes observed across X-ray bands represents one of the principle means of constraining the properties (mass and spin) of astrophysical black holes. Recent ''continuum fitting''…
Most black hole binaries show large changes in X-ray luminosity caused primarily by variations in mass accretion rate. An important question for understanding black hole accretion and jet production is whether the inner edge of the…