Broad-band spectral study of X-ray transient MAXI J1820+070 using Swift/XRT and NuSTAR

Abstract

We report on a \textit{NuSTAR} and \textit{Swift}/XRT observation of the newly discovered X-ray transient MAXI J1820+070. \textit{Swift}/XRT and \textit{NuSTAR} have concurrently observed the newly detected source on 14 March 2018. We have simultaneously fitted the broad-band spectra obtained from \textit{Swift}/XRT and \textit{NuSTAR}. The observed joint spectra in the energy range 0.6--78.0 keV are well modeled with a weak disk black-body emission, dominant thermal Comptonization and relativistic reflection fraction. We have detected a fluorescent Iron-K$\alpha$ line relativistically broadened, and a Compton hump at $\sim$ 30 keV. We constrain the inner disk radius as well as the disk inclination angle and their values are found to be 4.1${}_{-0.6}^{+0.8}$ R${}_{ISCO}$ (where R${}_{ISCO}\equiv$ radius of the innermost stable circular orbit) or 5.1${}_{-0.7}^{+1.0}$ r${}_g$ (where r${}_g\equiv$ gravitational radius) and 29.8${}_{-2.7}^{+3.0}$ ${}^{\circ }$ respectively. The best fit broad-band spectra suggest that the source was in the hard state and evolving. The source emission is best described by weak thermal emission along with strong thermal Comptonization from a relatively cold, optically thick, geometrically thin and ionized accretion disk. X-ray spectral modeling helps us to understand the accretion and ejection properties in the vicinity of the compact object.

07 pages, 05 figures and 02 tables, Accepted for publication by Monthly Notices of the Royal Astronomical Society

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Cited by in corpus (6)

• The binary mass ratio in the black hole transient MAXI J1820+070
• A timing study of MAXI J1820+070 based on Swift/XRT and NICER monitoring in 2018/19
• Physical origin of the nonphysical spin evolution of MAXI J1820+070
• A timing-based estimate of the spin of the black hole in MAXI J1820+070
• Unveiling the temporal properties of MAXI J1820+070 through AstroSat observations
• Accretion Scenario of MAXI J1820+070 during 2018 Outbursts with Multi-mission Observations