KULINDER PAL SINGH
Articles written in Journal of Astrophysics and Astronomy
Volume 40 Issue 3 June 2019 Article ID 0024
We present a process for thermal forming of thin glass panels of borosilicate glass to produce mirror segments for X-ray telescope optics. The mirror segments are required to be shaped in a parabolic and hyperbolic shape in accordance with Wolter-I type design of X-ray telescope optics. Thermal forming of glass is a low-cost method to produce light-weight mirror segments. The process makes use of a semi-cylindrical quartz mold having surface roughness of the order of 1 nm. Flat glass sheets of 0.2 mm and 0.3 mm thickness are placedon the diametric edges of the mold. With a suitable thermal cycle, the glass sheets are thermally formed as per the shape of the mold. The shape of these formed glass sheets was measured using a non-contact optical setup.The surface quality measurements of the formed glass sheets were performed using atomic force microscope and they were found to be in the range of 0.04–0.33 nm. Once tested for acceptance, these glass sheets are coatedusing sputter deposition of multi-layers of high and low atomic number materials for hard X-ray reflection. Such mirror segments do not require polishing of the surface before being coated with multi-layers.
Volume 42 All articles Published: 25 May 2021 Article ID 0017 PAYLOAD REVIEW
The Soft X-ray Telescope (SXT) aboard the AstroSat satellite is the first Indian X-ray telescope in space. It is a modest size X-ray telescope with a charge coupled device (CCD) camera in the focal plane, which provides X-ray images in the $\sim$0.3–8.0 keV band. A forte of SXT is in providing undistorted spectraof relatively bright X-ray sources, in which it excels over some current large CCD-based X-ray telescopes. Here, we highlight some of the published spectral and timing results obtained using the SXT data to demonstrate the capabilities and overall performance of this telescope.
Volume 42 All articles Published: 17 September 2021 Article ID 0103
Soft X-ray telescope (SXT) built on the principle of grazing incidence optics was launched onboard
Volume 43 All articles Published: 11 November 2022 Article ID 0085 ACTIVE GALACTIC NUCLEI
In this article, first the author present a short historical introduction to the discovery of extragalactic jets in active galactic nuclei (AGN), followed by a brief overview of their observational properties which lead to their various classifications and a unification scheme based on the viewing geometry of jets in the AGN. The author largely focus on the studies of multi-wavelength emissions and modeling of spectral energy distribution of AGN, which are dominated by emission from jets, namely, blazars. The author present a few new results from the studies of a few blazars based mostly on observations with the AstroSat. The author ends with an overview of the role played by the radio jets in clusters of galaxies in creating various interesting features in the hot gas, and feedback and regulation of heating and cooling in the cores of the hot gas.
Volume 44, 2023
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