Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Faculty Publications Article Faculty Publications -Articles Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Creator An entity primarily responsible for making the resource Giridharan, L.; Thomas, Neal Titus; Gudennavar, S.B.; Bubbly, S.G. Title A name given to the resource AstroSat's view of kHz quasi-periodic oscillations from 4U 1820?30 Date A point or period of time associated with an event in the lifecycle of the resource 01-01-2026 Source A related resource from which the described resource is derived Journal of High Energy Astrophysics;Volume;50;Issue;;Article No.;100494; Identifier An unambiguous reference to the resource within a given context <a href="https://doi.org/10.1016/j.jheap.2025.100494" target="_blank" rel="noreferrer noopener">https://doi.org/10.1016/j.jheap.2025.100494</a> <br /><br /><a href="https://www.scopus.com/pages/publications/105022186237?origin=resultslist" target="_blank" rel="noreferrer noopener">https://www.scopus.com/pages/publications/105022186237?origin=resultslist</a> Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Giridharan L., Department of Physics and Electronics, CHRIST University, Karnataka, Bangalore, 560029, India; Thomas N.T., Department of Physics and Electronics, CHRIST University, Karnataka, Bangalore, 560029, India; Gudennavar S.B., Department of Physics and Electronics, CHRIST University, Karnataka, Bangalore, 560029, India; Bubbly S.G., Department of Physics and Electronics, CHRIST University, Karnataka, Bangalore, 560029, India Description An account of the resource This study presents the spectro-temporal analysis of the neutron star low mass X-ray binary 4U 1820?30, using data from three observations conducted by AstroSat 's Soft X-ray Telescope and Large Array X-ray Proportional Counter. Spectral analysis revealed that the source spectra could be modelled using an absorbed blackbody and a multi-temperature disk model along with a Comptonization model with ?=1.24 ? 1.89 and the inner accretion disk located at an distance of ?17 km from the neutron star. This showed the source to be in the hard spectral state. Temporal analysis revealed the presence of kHz quasi-periodic oscillations (QPOs) with frequencies in the 640 ? 1090 Hz range with root mean squared (RMS) amplitudes between 6 ? 10 per cent and quality factors between 8 ? 42. The RMS amplitude?energy and time lag?energy spectra of the upper and lower kHz QPOs hint them to be caused by modulations of photons having a common radiative mechanism. Moreover, the maximum RMS amplitude and time lag exhibited an anti-correlation with mass accretion rate. Using an analytical relation based on the relativistic precession model, the mass of the neutron star in the system was estimated to be 1.8 M?. The emission radius of one of the detected kHz QPOs was estimated to be ? 17 km. 2025 Elsevier B.V. Subject The topic of the resource Accretion, accretion discs; Stars: neutron; X-rays: binaries; X-rays: individual: 4U 1820?30 Publisher An entity responsible for making the resource available Elsevier B.V. Relation A related resource ISSN: 22144048; Language A language of the resource English Type The nature or genre of the resource Article Rights Information about rights held in and over the resource Restricted Access; Hardcopy may be available in the library Format The file format, physical medium, or dimensions of the resource online