Wideband study of the brightest black hole X-ray binary 4U 1543−47 in the 2021 outburst: signature of disc-wind regulated accretion

Abstract

A comprehensive wideband spectral analysis of the brightest black hole X-ray binary 4U 1543 − 47 during its 2021 outburst is carried out for the first time using NICER, NuSTAR, and AstroSat observations by phenomenological and reflection modelling. The source attains a super-Eddington peak luminosity and remains in the soft state, with a small fraction ($< 3\%$) of the inverse-Comptonized photons. The spectral modelling reveals a steep photon index (Γ ∼ 2 − 2.6) and relatively high inner disk temperature (Tin ∼ 0.9 − 1.27 keV). The line-of-sight column density varies between (0.45 − 0.54) × 1022 cm−2. Reflection modelling using the RELXILL model suggests that 4U 1543 − 47 is a low-inclination system (θ ∼ 32○ − 40○). The accretion disk is highly ionized (log ξ > 3) and has super solar abundance (3.6−10 AFe, ⊙) over the entire period of study. We detected a prominent dynamic absorption feature between ∼8 − 11 keV in the spectra throughout the outburst. This detection is the first of its kind for X-ray binaries. We infer that the absorption of the primary X-ray photons by the highly ionized, fast-moving disk-winds can produce the observed absorption feature. The phenomenological spectral modelling also shows the presence of a neutral absorption feature ∼7.1 − 7.4 keV, and both ionized and neutral absorption components follow each other with a delay of a typical viscous timescale of 10 − 15 days.

The bright black hole X-ray binary 4U 1543–47 during the 2021 outburst: A thick accretion disk inflated by high luminosity

“…This absorption feature is believed to be associated with the presence of disk winds. However, based on our fitting results and the findings in Prabhakar et al (2023), we observe that the corona only contributes to a small fraction (less than 8%) of the total flux, suggesting that the illumination from such a weak corona should be correspondingly faint.…”

Discovery of X-Ray Polarization from the Black Hole Transient Swift J1727.8−1613

“…In these cases, we see the innermost parts of the disk/corona during the hard state. On the other hand, the luminosities of GRS 1915+105, V404 Cyg, V4641 Sgr, and 4U 1543−47 are believed to reach near-and super-Eddington values, and signatures of an optically thick outflow, that can cover the innermost regions, have been detected (Revnivtsev et al 2002;Motta et al 2017;Miller et al 2020;Prabhakar et al 2023). Analogs to these classes of sources can be found in active galactic nuclei, whose geometry studies are now also enabled by IXPE data.…”