Future Plan

We are now in the process of employing a full general relativistic description of axisymmetric accretion in Kerr geometry, to study the environment of the close vicinity of the central black hole of Sgr A$^*$. We have, thus, already formulated and solved the governing equations describing the low angular momentum relativistic accretion flow around a spinning black hole. We have been able to calculate the density, pressure, and ion temperature distribution for such flow at any radial distance (measured from the event horizon of the central black hole of Sgr A$^*$.). We also have estimated the shock location and have been able to study the temperature and density stratification of the accretion disc due to such shock formation, and could quantify how such temperature enhancement at the post shock zone may contribute to the emergent spectrum.

We are now working at the theory of spectral formation for such a model. We are in the process of converting the ion temperature into the electron temperature by incorporating suitable physical mechanisms, and taking care of appropriate relativistic corrections. This will enable us to construct a canonical spectra, emerging as a result of shock formation in low angular momentum black hole accretion. Such a characteristic spectra will be useful to explain the origin and duration of the X-ray flares (and other variabilities observed at the close proximity of our galactic centre) observed to be emanating out from our Galactic centre.

We also study how the black hole spin parameter influences such spectral features. One of the most tantalizing issues in relativistic astrophysics is to investigate whether the spin of the black hole could be determined using any observational means, the spectral signature of the black hole, for example. Investigation of general relativistic accretion flows in Kerr metric may provide an important step towards a better understanding of this problem. This will be of immense importance in the sense that it will provide us a definitive measure of the spectral characteristics of black hole spin, and using our formalism, the spin parameter of our Galactic centre black hole can be estimated.