The Spin and Orientation of the Black Hole in XTE J1908$+$094

TL;DR

This study measures the spin and inclination of the black hole in XTE J1908+094 using relativistic reflection modeling of NuSTAR X-ray data, exploring various assumptions to ensure robust results.

Contribution

It provides a comprehensive analysis of black hole spin in XTE J1908+094 by testing 19 different reflection models, advancing the methodology for spin measurement in X-ray binaries.

Findings

Black hole spin estimated at a=0.55^{+0.29}_{-0.45}

Inclination angle measured at 27^{+2}_{-3} degrees

Consistent spin estimates across all models

Abstract

NuSTAR observed the black hole candidate XTE J1908$+$094 during its 2013 and 2019 outbursts. We use relativistic reflection to measure the spin of the black hole through 19 different assumptions of relxill flavors and parameter combinations. The most favored model in terms of Deviance Information Criterion (DIC) measures the spin of the black hole to be $a = 0.55^{+0.29}_{-0.45}$, and an inclination of $\theta=27^{+2}_{-3}$ degrees ($1\sigma$ statistical errors). We look at the effects of coronal geometry assumptions and density of the accretion disk on the spin prediction. All 19 tested models provide consistent spin estimates. We discuss the evolution of spin measurement techniques using relativistic reflection in X-ray binaries and discuss the implications of this spin measurement in reconciling the distributions of stellar mass black hole spin measurements made through X-ray and gravitational wave observations.