부산대학교 도서관

We present here the results of the first broadband simultaneous spectral and temporal studies of the newly detected black hole binary MAXI J1820+070 as seen by SXT and LAXPC on-board AstroSat.The observed combined spectra in the energy range 0.7-80 keV were well modeled using disk black-body emission, thermal Comptonization and a reflection component. The spectral analysis revealed that the source was in its hard spectral state (Gamma=1.61) with a cool disk (kTin=0.22 keV). We report the energy dependent time-lag and root mean squared (rms) variability at different frequencies in the energy range 3-80 keV using LAXPC data. We also modeled the flux variability using a single zone stochastic propagation model to quantify the observed energy dependence of time-lag and fractional rms variability and then compared the results with that of Cygnus X-1. Additionally, we confirm the detection of a quasi-periodic oscillation with the centroid frequency at 47.7 mHz.
Comment: Accepted for publication in Astrophysical Journal Letters (ApJL). The article contains 8 pages, 4 figures and 1 Table. Missing reference added. Some typos corrected