Abstract Details

Name: Malu S
Affiliation: Department of Astronomy, Osmania University, Hyderabad
Conference ID: ASI2021_334
Title : Spectro-temporal studies of the Atoll source 4U 1705-44: Investigating the inner region of the accretion disk
Authors and Co-Authors : Malu S (Department of Astronomy, Osmania University, Hyderabad), Dr. K Sriram (Department of Astronomy, Osmania University, Hyderabad), Dr. Vivek Kumar Agrawal (Space Astronomy Group, ISITE Campus, U R Rao Satellite Center, Bangalore)
Abstract Type : Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : We performed spectro-temporal analysis of the atoll source 4U 1705-44 using AstroSat SXT and LAXPC in order to understand its inner accretion disk region. The source was found to be in the banana state during the observations. Power density spectral studies revealed the presence of a peaked broad low frequency noise (LFN) component from 5.0--13.5 Hz in the 3-10 keV energy band, with the most prominent feature detected with a Q factor of ~ 1.6. This feature was absent in the 10-20 keV energy band. We constrained the height/radius of a viscous shell within the inner accretion disk region by assuming this LFN component to be oscillations originating within such a shell. Cross-Correlation Function study (CCF) between the 3-5 keV (LAXPC),0.8-2 keV (SXT) and 15-30 keV LAXPC data showed CCF lags of the order of few tens to hundred seconds. Previous studies have shown that these lags can be used to constrain the coronal height as they can be interpreted as the readjustment timescales of this coronal structure. Coronal height was constrained to be of the order of few tens of kms. Spectral studies indicated a variation in the power-law index as the source traversed along the Banana branch and it was found that the source was close to the last stable orbit. Results of these spectro-temporal studies show similarities to those performed on Z sources.