| Name: | Malu S |
| Affiliation: | Department of Astronomy, Osmania University, Hyderabad |
| Conference ID : | ASI2022_629 |
| Title : | Spectro-temporal studies of GX 339-4: Understanding the Comptonization region |
| Authors : | Malu S, Department of Astronomy, Osmania University, Hyderabad K. Sriram, Department of Astronomy, Osmania University, Hyderabad |
| Abstract Type: | Poster |
| Abstract Category : | Stars, ISM and Galaxy |
| Abstract : | GX 339-4 underwent an outburst in January 2021 as indicated by the X-ray detection using NICER, NuSTAR, SWIFT (BAT and UVOT), INTEGRAL, MAXI, and AstroSat, and optical monitoring from MeerKAT. Near-daily cadence observations using NICER from MJD 59234 to MJD 59293 suggested that the source was in the bright hard state (ATel #14490). Later observations from MJD 59299 to MJD 59301.42, indicate a drastic increase in the count rate with a rise in disk parameters and photon index (ATel #14490). This suggested a state transition from the hard to soft state. Rapidly changing Comptonization parameters indicate a varying coronal structure. To understand the nature of corona during the outburst and state transition, we perform a cross correlation function study using the SWIFT UVOT, NICER, and NuSTAR observations to constrain the coronal structure. Any lags obtained may be interpreted as the readjustment timescale of the disk-coronal structure (Sriram et al. 2019). A broadband spectral study will also be reported in order to interpret the observed CCF nature and PDS. Results based on the energy dependent cross spectral study will also be discussed. |