The spin of the black hole 4U 1543-47

TL;DR

This study estimates the black hole spin in 4U 1543-47 by combining spectral fitting methods, resulting in a moderate spin value that aligns with previous estimates within uncertainties.

Contribution

It demonstrates that combining thermal and reflection spectral models yields a consistent black hole spin measurement, addressing discrepancies from previous individual methods.

Findings

Moderate black hole spin a* ≈ 0.43 with uncertainties.

Combined spectral methods produce consistent spin estimates.

Discussion of systematic uncertainties and implications.

Abstract

We present a new analysis of Rossi X-ray Timing Explorer observations of the 2002 outburst of the transient X-ray nova 4U 1543-47. We focus on observations in the High/Soft state, and attempt to measure the spin of the black hole by simultaneously fitting the thermal disk continuum and by modeling the broadened iron k-shell emission lines and additional blurred reflection features. Previous works have found that use of these methods individually returns contradictory values for the dimensionless spin parameter a* =cJ/GM^2. We find that when used in conjunction with each other, a moderate spin is obtained (a*=0.43 +0.22 -0.31) that is actually consistent with both other values within errors. We discuss limitations of our analysis, systematic uncertainties, and implications of this measurement, and compare our result to those previously claimed for 4U 1543-47.