| Name: | Soma Mandal |
| Affiliation: | Government Girls' General Degree College, Kolkata |
| Conference ID : | ASI2024_191 |
| Title : | Spectral-timing analysis of kHz QPOs observed by AstroSat |
| Authors : | Soma Mandal |
| Authors Affiliation: | Government Girls' General Degree College, Kolkata 700 023, India |
| Mode of Presentation: | Poster |
| Abstract Category : | High Energy Phenomena, Fundamental Physics and Astronomy |
| Abstract : | We present a systematic spectral-timing analysis of the kHz QPO in the neutron star low mass X-ray binaries observed by AstroSat. Here we have detected four (4) sources with the upper kHz QPOs in the power density spectrum in the 3-20 keV energy range and we have been able to obtain correlated time lags and fractional r.m.s as a function of energy. Out of the 4 sources we have focused on the sources 4U 1636-536 and 4U 1728-34. The data of the different observations of the sources using SXT and LAXPC has been analysed and strictly simultaneous spectral analysis reveals a clear presence of the Fe line in the spectra. More detailed studies reveal for the first time a strict correlation between the QPO frequency and photon index of the spectra as well as between the iron line width and photon index which further indicates a correlation between iron line width and the QPO frequency. Detailed timing analysis shows an appearance of a hump around 30 Hz which gets prominent as the source reaches the softer end of the HID along with the presence of the upper kHz QPOs with frequency varying from 600-900 Hz. Further study of the increasing r.m.s and soft time lag behaviour gives an indication of single coronal region while hard lag indicates an existence of multiple coronal region. |
