We investigate the association between the accretion disk during radio plateau state and the following superluminal relativistic radio jets with peak intensity varies from 200 mJy to 1000 mJy observed over a period of five years and present the evidences of direct accretion disc-jet connection in microquasar GRS 1915+105 . We have analysed RXTE PCA/HEXTE X-ray data and have found that the accre...

We consider the structure of self-gravitating marginally stable accretion disks in galactic centers in which a small fraction of the disk mass has been converted into protostars. We find that proto-stars accrete gaseous disk matter at prodigious rates. Mainly due to the stellar accretion luminosity, the disk heats up and geometrically thickens, shutting off further disk fragmentation. The exist...

One possible mechanism for giant planet formation is disk instability in which the planet is formed as a result of gravitational instability in the protoplanetary disk surrounding the young star. The final composition and core mass of the planet will depend on the planet’s mass, environment and the planetesimal accretion efficiency. We calculate heavy element enrichment in a Jupiter-mass protop...

The black hole candidate X-ray transient XTE J1817−330 was observed by the Swift satellite over 160 days of its 2006 outburst with the XRT and UVOT instruments. At the start of the observations, the XRT spectra show that the 0.6-10 keV emission is dominated by an optically thick, geometrically thin accretion disk with an inner disk temperature of ∼ 0.8 keV, indicating that the source was in a h...

Periodic outbursts are observed in many AGNs and usually explained with a supermassive black hole binary (SMBHB) scenario. However, multiple periods are observed in some AGNs and cannot be explained with it. Here we analyze the periodicity of the radio light curves of AO 0235+164 at multi-frequencies and report the discovery of six QPOs in integer ratio 1:2:3:4:5:6 of QPO frequencies, of which ...

I discuss recent observations of asymmetries in Doppler shifts across T Tauri jets, and argue that the observed asymmetric velocity shifts and gradients do not indicate jet rotation. These observations, therefor, cannot be used as a support of a magnetized disk wind. The interaction of the jets with a twisted-tilted (wrapped) accretion disk (or the variable velocity precessing model) accounts b...

We present pulse-phase X-ray spectroscopy of the high-mass X-ray pulsar SMC X-1 from five different epochs, using Chandra X-ray Observatory ACIS-S and XMM-Newton EPIC-pn data. The X-ray spectrum consistently shows two distinct components, a hard power law and a soft blackbody with kT BB ∼ 0.18 keV. For all five epochs the hard component shows a simple double-peaked pulse shape, and also a varia...

The first VLBI images of H2O maser emission in the Circinus Galaxy AGN show both an accretion disk and outflow 0.1 to 1 pc from the central engine. The maser traces a warped, edge-on accretion disk between radii of about 0.1 and 0.4 pc that is bound by a 1.3 × 10 6 M⊙ central mass. The rotation curve is somewhat flatter than a Keplerian rotation law and is consistent with a disk mass on the ord...

Misaligned accretion disks surrounding rotating compact objects experience a torque due to the LenseThirring effect, which leads to precession of the inner disk. It has been suggested that this effect could be responsible for some low frequency Quasi-Periodic Oscillations observed in the X-ray lightcurves of neutron star and galactic black hole systems. We investigate this possibility via time-...