Abstract Details

Name: Nazma Husain
Affiliation: jamia millia islamia university
Conference ID: ASI2021_75
Title : Detection of mHz frequency break in weak low/hard state of GX 339-4 using AstroSat data
Authors and Co-Authors : Nazma Husain(Department of Physics, Jamia Millia Islamia), Ranjeev Misra (Inter-University Center for Astronomy and Astrophysics) and Somasri Sen (Department of Physics, Jamia Millia Islamia)
Abstract Type : Oral
Abstract Category : Stars, ISM and Galaxy
Abstract : Using AstroSat data, we report the detection of a characteristic mHz low-frequency break in the power density spectrum (PDS) of GX 339-4 in weak low/hard state, when the source luminosity was 0.002 that of the Eddington value. The source was at the beginning of a failed outburst in 2017. The X-ray spectral continuum could be well described by an absorbed power-law with photon index ~1.57. Addition of a reflection component in the spectral modelling improves the chi-squared fit, showing the possibility of weak broadened reflection features in the energy spectrum. We perform timing analysis by studying the PDS with data from detectors LAXPC 10, LAXPC 20 and SXT of AstroSat. The PDS exhibits band-limited noise with a mHz low-frequency break in all three detectors, which are the two typical features of low/hard state in Blackhole systems. When compared to earlier low luminosity observations of this source, our result fits in a positive correlation found between break frequency and unabsorbed flux. Also, the mHz break frequency may be associated with the viscous time scale of the truncation radius at ~142 gravitational radii.