Properties of 2017-18 'failed' Outburst of GX 339-4

TL;DR

This study analyzes the 2017-18 failed outburst of GX 339-4, revealing it remained in the hard state with dominant non-thermal flux, and provides detailed spectral and temporal insights including QPOs and black hole mass estimation.

Contribution

It offers a comprehensive spectral and temporal analysis of a failed outburst using NICER and AstroSat data, applying both phenomenological and physical models, and estimates the black hole mass.

Findings

Outburst remained in the hard spectral state throughout.

Spectra were mostly fitted with powerlaw models, few required disk blackbody plus powerlaw.

Detected a 0.31 Hz QPO with four harmonics and estimated black hole mass as ~10.76 solar masses.

Abstract

The Galactic transient black hole candidate GX 339-4 is a very interesting object to study as it showed both complete and failed types of outbursts. We studied both spectral and temporal properties of the 2017-18 outburst of the source using archival data of NICER and AstroSat instruments. This 2017-18 outburst is found to be failed in nature, as during the entire period of the outburst, the source was only in the hard spectral state. Source spectra were highly dominated with the non-thermal fluxes. When we tried to fit spectra with phenomenological models, most of the spectra were fitted with only the powerlaw model, and only six spectra required disk black body plus powerlaw models. While fitting spectra with the physical two-component advective flow (TCAF) model, we observed that the flow was highly dominated by the sub-Keplerian halo rate. The presence of stronger shock at a larger radius from the black hole was also observed during the rising and declining phases of the outburst. A prominent signature of $0.31$~Hz QPO is observed with its four harmonics. Mass of the black hole was also estimated from our spectral analysis with the TCAF model as $10.76^{+0.77}_{-1.07}~M_\odot$.