| Abstract : | GX 339-4, a low mass X-ray binary, has frequent outburst cycle of typically 2-3 years. Three outbursts of GX 339-4 were observed by NICER, and it is evident from MAXI lightcurve and hardness intensity diagram that recent outburst in 2021 follows a typical Q-profile and confirmed state transition. The recent outburst of source has been observed by NICER regularly in soft x-ray. We analysed the NICER data of GX 339-4 for recent outburst. We carried out timing analysis of NICER data. We studied the x-ray variability of the source using power spectral density, time lag and coherence. A slowly varying low frequency QPO has been detected in hard state. During hard to soft state transition, a fast varying low frequency QPO was observed and its evolution was studied using Dynamic power spectra. A QPO in 5-6 Hz range was observed in rising as well as in decay phase of the outburst. |
