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تسجيل مستخدم جديدAstroSat and MAXI view of the Black Hole binary 4U 1630-472 during 2016 and 2018 Outbursts
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We present an in-depth spectral and timing analysis of the Black Hole binary 4U 1630-472 during 2016 and 2018 outbursts as observed by textit{AstroSat} and textit{MAXI}. The extensive coverage of the outbursts with textit{MAXI} is used to obtain the Hardness Intensity Diagram (HID). The source follows a `c-shaped profile in agreement with earlier findings. Based on the HIDs of previous outbursts, we attempt to track the evolution of the source during a `super-outburst and `mini-outbursts. We model the broadband energy spectra ($0.7-20.0$ keV) of textit{AstroSat} observations of both outbursts using phenomenological and physical models. No Keplerian disc signature is observed at the beginning of 2016 outburst. However, the disc appears within a few hours after which it remains prominent with temperature ($T_{in}$) $sim$ 1.3 keV and increase in photon index ($Gamma$) from 1.8 to 2.0, whereas the source was at a disc dominant state throughout the textit{AstroSat} campaign of 2018 outburst. Based on the HIDs and spectral properties, we classify the outbursts into three different states - the `canonical hard and soft states along with an intermediate state. Evolution of rms along different states is seen although no Quasi-periodic Oscillations (QPOs) are detected. We fit the observed spectra using a dynamical accretion model and estimate the accretion parameters. Mass of the black hole is estimated using inner disc radius, bolometric luminosity and two component flow model to be $3-9$ $M_{odot}$. Finally, we discuss the possible implications of our findings.
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