Exploring the energy-dependent temporal nature of MAXI J1803-298 using AstroSat and NICER.

In this work we have performed the spectral and temporal analysis of MAXI J1803-298 using AstroSat (LAXPC and SXT) and NICER observations taken during it’s outburst in May 2021. We found that the source traverses through hard, intermediate, and soft states of the outburst. The spectrum in all the states can be described using the soft emissions from the thermal disk and the hard emissions from the hot and warm coronal regions. We affirmed the presence of broad features, Type C, and Type B QPOs in power spectra of different spectral states. We investigated the fractional rms and lags of all the variability features and discovered that lag swung between positive and negative over the outburst evolution. While modeling the features with a simple model that considers variations in accretion parameters such as accretion rate, heating rate, and inner disc radius along with delays between them, we found a dynamic reversal in the origin of variability between the corona and disc.