Abstract Extragalactic black hole X-ray binaries LMC X-1 and LMC X-3 are the persistent sources which are usually found in a soft spectral state. In this study, we consider multi-mission (MAXI, NICER, NuSTAR and AstroSat) X-ray observations of both these sources carried out during 2014–2020 to perform a detailed spectral and temporal analysis. Study of long term MAXI lightcurve shows that the flux variability of LMC X-1 is moderate (fractional variability, ) whereas that of LMC X-3 is high () in 2–10 keV which is associated with the change in spectral state. The energy spectra of LMC X-1 and LMC X-3 are characterized by a multi-color disc blackbody and a Comptonization component, with LMC X-1 having an additional Fe-line emission feature. NICER ( keV), NuSTAR ( keV) and AstroSat ( keV) spectral analysis collectively shows that LMC X-1 has remained in the soft state (disc flux contribution in 0.3–40 keV, , photon index ) throughout the period of 2014–2020. Mass accretion rate () of LMC X-1 during this period, calculated from bolometric luminosity ( keV) is found to be within (Eddington mass accretion rate). Although LMC X-3 remained in the soft state during most of the observations (), it exhibits a transition into hard state () and intermediate state (). of LMC X-3 through different spectral states varies in the range . Temporal studies carried out for these observations show that the Power Density Spectra (PDS) in keV follow a red-noise with fractional rms of for LMC X-1 and in case of LMC X-3, rms is less during the soft state (), but relatively high in the intermediate () and hard states (). From spectral modeling of the soft X-ray continuum of NICER and NuSTAR energy spectra with relativistic accretion disc and reflection models, we constrain the spin and accretion rate () of the BHs. In case of LMC X-1, spin is estimated to be within by continuum-fitting method and by Fe-line fitting method and in case of LMC X-3 continuum-fitting yields its value is in the range . Finally, we discuss the implications of our findings in the context of accretion disc dynamics around the vicinity of the BHs.
Multi-mission view of extragalactic black hole X-ray binaries LMC X-1 and LMC X-3: Evolution of broadband spectral features
Advances in Space Research ; 69 , 1 ; 483-498
2021-09-29
16 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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