The XMM Newton spectra of the 2012 outburst of the black-hole candidate 4U 1630-47 revisited

TL;DR

This study reanalyzes XMM-Newton data of black-hole candidate 4U 1630-47's 2012 outburst, proposing an alternative model that explains spectral features without Doppler-shifted lines, emphasizing the role of non-solar element abundances and ionized absorbers.

Contribution

The paper introduces a simplified spectral model that accounts for observed features without Doppler-shifted lines by considering non-solar abundances and ionized absorption, improving fit quality.

Findings

A broad emission line around 7 keV is required in the model.

Highly ionized Fe and Ni absorption features indicate a nearby ionized absorber.

The alternative model fits all observations, including those with Doppler-shifted lines.

Abstract

Recent XMM-Newton observations of the black-hole candidate 4U 1630-47 during the 2012 outburst revealed three relativistically Doppler-shifted emission lines that were interpreted as arising from baryonic matter in the jet of this source. Here we reanalyse those data and find an alternative model that, with less free parameters than the model with Doppler-shifted emission lines, fits the data well. In our model we allow the abundance of S and Fe in the interstellar material along the line of sight to the source to be non solar. Among other things, this significantly impacts the emission predicted by the model at around 7.1 keV, where the edge of neutral Fe appears, and renders the lines unnecessary. The fits to all the 2012 XMM-Newton observations of this source require a moderately broad emission line at around 7 keV plus several absorption lines and edges due to highly ionised Fe and Ni, which reveal the presence of a highly-ionised absorber close to the source. Finally, our model also fits well the observations in which the lines were detected when we apply the most recent calibration files, whereas the model with the three Doppler-shifted emission lines does not.