Dewangan, G. C., Griffiths, R. E., Dasgupta, Surajit, Rao, A. R.
We investigate the origin of the soft X-ray excess emission from narrow-line Seyfert 1 galaxies Akn564 and Mrk1044 using XMM-Newton observations. We find clear evidence for time delays between the...
Time lags in Narrow-line Seyfert 1 galaxies and the origin of their soft excess emission (2007)
Dewangan, G. C., Griffiths, R. E., Rao, A. R., Dasgupta, Surajit
The origin of soft X-ray excess emission from type 1 active galactic nuclei has remained a major problem for the last two decades. It has not been possible to distinguish alternative models for the...
Black-Hole Accretion Disc as an Analogue Gravity Model (2006)
Das, Tapas Kumar, Bilic, Neven, Dasgupta, Surajit
We formulate and solve the equations governing the transonic behaviour of a general relativistic black-hole accretion disc with non-zero advection velocity. We demonstrate that a relativistic...
Anti-correlated hard X-ray time lag in GRS 1915+105: evidence for a truncated accretion disc (2005)
Choudhury, Manojendu, Rao, A. R., Dasgupta, Surajit, Pendharkar, J., Sriram, K., Agrawal, V. K.
Multi-wavelength observations of Galactic black hole candidate sources indicate a close connection between the accretion disk emission and the jet emission. The recent discovery of an anti-correlated...
Pseudo-Schwarzschild Spherical Accretion as a Classical Black Hole Analogue (2005)
Dasgupta, Surajit, Bilić, Neven, Das, Tapas K.
We demonstrate that a spherical accretion onto astrophysical black holes, under the influence of Newtonian or various post-Newtonian pseudo-Schwarzschild gravitational potentials, may constitute a...
Dasgupta, Surajit, Rao, A. R., Dewangan, G. C., Agrawal, V. K.
We present the results of an analysis of data from XMM-Newton and CHANDRA observations of the high luminosity narrow-line quasar PG 1404+226. We confirm a strong soft X-ray excess in the X-ray...
Dasgupta, Surajit, Rao, A. R., Dewangan, G. C.
We present results based on an XMM-Newton observation of the high luminosity narrow-line QSO PHL 1092 performed in 2003 January. The 0.3 - 10 keV spectrum is well described by a model which includes...