Speaker
Description
We present the comprehensive analyses of the wide band spectral and timing variabilities of the two BH sources, namely GX 339$-$4 and H 1743$-$322, using AstroSat and NuSTAR observations during $2016-2022$. We observe that both GX 339$-$4 and H 1743$-$322 experienced successful as well as failed outbursts during $2016-2022$. Using long-term MAXI and BAT light curves, we examine the outburst profiles of both sources when they underwent failed and successful outbursts. GX 339$-$4 transits from quiescence to outburst and the broad-band spectral modelling indicates that the source traces through the several spectral states, namely hard ($kT_{\rm {bb}}=0.29-0.53$ keV, $\Gamma=1.46-1.65$ and $L_{\rm bol} =0.25-8.37$\% $L_{\rm Edd}$), intermediate ($kT_{\rm {bb}}=0.17-0.71$ keV, $\Gamma=1.71-2.49$, $L_{\rm {bol}}=6.46-9.11 \% \,L_{\rm Edd}$) and soft states ($kT_{\rm {in}}=0.51-0.93$ keV, $\Gamma=1.67-3.74$, $L_{\rm {bol}}=1.48-12.66 \% \,L_{\rm Edd}$), respectively. On the contrary, H 1743$-$322 transits from quiescent state to hard state ($\Gamma=1.57-1.71$, $L_{\rm {bol}}=3.07-5.81 \% \,L_{\rm Edd}$) only. We detect both type-B and type-C Quasi-periodic Oscillations (QPOs) in GX 339$-$4 of frequencies varying between $0.1 - 5.37$ Hz along with harmonics. For H 1743$-$322, prominent type-C QPO is found with frequencies in the range $0.22 - 1.03$ Hz along with distinct harmonics. The energy-dependent power density spectrum reveals that the fundamental QPO and harmonics disappear beyond $20$ keV in GX 339$-$4, whereas the fundamental QPO is present in the $3-40$ keV energy band, and the harmonic disappears beyond $\sim 20$ keV. Finally, we discuss the implications of our observational findings in the context of accretion dynamics around the black hole binaries.
| aneeshaunnikrishnan@gmail.com | |
| Affiliation | IIT Guwahati |
