# Wideband Study of the Brightest Black Hole X-ray Binary 4U 1543-47 in the 2021 Outburst: Signature of Disk-Wind Regulated Accretion

**Authors:** Geethu Prabhakar, Samir Mandal, Bhuvana G. R., Anuj Nandi  
**arXiv:** [2301.13711](https://arxiv.org/abs/2301.13711)  
**Date:** 2023-01-31  
**Summary page:** https://www.summarizepaper.com/en/paper/2301.13711v1/

## Key points

- Comprehensive wideband spectral analysis of black hole X-ray binary 4U $1543-47$ during its 2021 outburst
- Observations from NICER, NuSTAR, and AstroSat used in the study
- Super-Eddington peak luminosity and soft state throughout the outburst
- Less than 3% of photons are inverse-Comptonized
- Steep photon index (2 to 2.6) and high inner disk temperature (0.9 to 1.27 keV)
- Line-of-sight column density varies between ($0.45-0.54$)$\times10^{22}$ cm$^{-2}$
- Low-inclination system with inclination angle estimated between approximately $32^\circ$ and $40^\circ$
- Highly ionized accretion disk with super solar abundance of iron throughout observation period
- Detection of a dynamic absorption feature between approximately 8 and 11 keV, attributed to absorption by fast-moving disk winds
- Detection of a neutral absorption feature around 7.1 to 7.4 keV with a delay of approximately 10 to 15 days

## Summary

A comprehensive wideband spectral analysis of the black hole X-ray binary 4U $1543-47$ during its 2021 outburst has been conducted using observations from NICER, NuSTAR, and AstroSat. This study, which combines phenomenological and reflection modeling, provides valuable insights into the properties of this source. The observations reveal that 4U $1543-47$ reaches a super-Eddington peak luminosity and remains in the soft state throughout the outburst. Interestingly, only a small fraction (less than 3%) of the photons are inverse-Comptonized. The spectral modeling indicates a steep photon index (ranging from approximately 2 to 2.6) and a relatively high inner disk temperature (around 0.9 to 1.27 keV). The line-of-sight column density varies between ($0.45-0.54$)$\times10^{22}$ cm$^{-2}$. Furthermore, the reflection modeling using the RELXILL model suggests that 4U $1543-47$ is a low-inclination system with an inclination angle estimated to be between approximately $32^\circ$ and $40^\circ$. The accretion disk in this system is found to be highly ionized (with log $\xi$ greater than 3) and exhibits super solar abundance (ranging from 3.6 to 10 times the solar iron abundance) throughout the entire observation period. One significant finding of this study is the detection of a prominent dynamic absorption feature between approximately 8 and 11 keV in the spectra throughout the outburst. This detection represents the first time such an absorption feature has been observed in X-ray binaries. The researchers propose that this absorption feature can be attributed to the absorption of primary X-ray photons by highly ionized and fast-moving disk winds. Additionally, a neutral absorption feature around 7.1 to 7.4 keV is also detected in the phenomenological spectral modeling; both components show a delay of approximately 10 to 15 days corresponding to a typical viscous timescale.