• H. SREEHARI

      Articles written in Journal of Astrophysics and Astronomy

    • Observational aspects of outbursting black hole sources: Evolution of spectro-temporal features and X-ray variability

      H. SREEHARI ANUJ NANDI D. RADHIKA NIRMAL IYER SAMIR MANDAL

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      We report on our attempt to understand the outbursting profile of Galactic Black Hole sources, keeping in mind the evolution of temporal and spectral features during the outburst. We present results of evolution of quasi-periodic oscillations, spectral states and possible connection with jet ejections during the out burst phase. Further,we attempt to connect the observed X-ray variabilities (i.e., ‘class’/‘structured’ variabilities, similar to GRS 1915$+$105) with spectral states of black hole sources. Towards these studies, we consider three black hole sources that have undergone single (XTE J1859$+$226), a few (IGR J17091$-$3624) and many (GX 339-4) outbursts since the start of $RXTE$ era. Finally, we model the broadband energy spectra (3–150 keV) of different spectral states using $RXTE$ and $NuSTAR$ observations. Results are discussed in the context oftwo-component advective flow model, while constraining the mass of the three black hole sources.

    • Advective accretion flow properties around rotating black holes – application to GRO J1655-40

      RAMIZ AKTAR SANTABRATA DAS ANUJ NANDI H. SREEHARI

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      We examine the properties of the viscous dissipative accretion flow around rotating black holes in the presence of mass loss. Considering the thin disc approximation, we self-consistently calculate the inflow-outflow solutions and observe that the mass outflow rates decrease with the increase in viscosity parameter ($\alpha$). Further, we carry out the model calculation of quasi-periodic oscillation frequency ($\nu_{\rm QPO}$) that is frequentlyobserved in black hole sources and observe that $\nu^{\max}_{\rm QPO}$ increases with the increase of black hole spin ($a_{\rm k}$). Then, we employ our model in order to explain the High Frequency Quasi-Periodic Oscillations (HFQPOs) observedin black hole source GROJ1655-40. While doing this, we attempt to constrain the range of $a_k$ based on observed HFQPOs ($\sim$300 Hz and $\sim$450 Hz) for the black hole source GRO J1655-40.

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    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

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      Posted on July 25, 2019

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