Comparison of spectral models for disc truncation in the hard state of GX 339-4. (arXiv:1811.09145v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Dzielak_M/0/1/0/all/0/1">Marta A. Dziełak</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zdziarski_A/0/1/0/all/0/1">Andrzej A. Zdziarski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Szanecki_M/0/1/0/all/0/1">Michał Szanecki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marco_B/0/1/0/all/0/1">Barbara De Marco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Niedzwiecki_A/0/1/0/all/0/1">Andrzej Niedźwiecki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Markowitz_A/0/1/0/all/0/1">Alex Markowitz</a>
We probe models of disc truncation in the hard spectral state of an outburst
of the well-known X-ray transient GX 339-4. We test a large number of different
models of disc reflection and its relativistic broadening, using two
independent sets of codes, and apply it to a Rossi X-ray Timing Explorer
spectrum in the rising part of the hard state of the 2010/11 outburst. We find
our results to be significantly model-dependent. While all of the models tested
show best-fits consistent with truncation, some models allow the disc to extend
close to the innermost stable circular orbit (ISCO) and some require
substantial disc truncation. The different models yield a wide range in
best-fit values for the disc inclination. Our statistically best model has a
physical thermal Comptonization primary continuum, requires the disc to be
truncated at a radius larger than that of $approx$2 ISCO, and predicts a disc
inclination in agreement with that of the binary. Our preferred models have
moderate Fe abundance, $gtrsim$2 times the solar one. We have also tested the
effect of increasing the density of the reflecting medium. We find it leads to
an increase of the truncation radius, but also to an increase of the Fe
abundance, opposite to a previous finding.
We probe models of disc truncation in the hard spectral state of an outburst
of the well-known X-ray transient GX 339-4. We test a large number of different
models of disc reflection and its relativistic broadening, using two
independent sets of codes, and apply it to a Rossi X-ray Timing Explorer
spectrum in the rising part of the hard state of the 2010/11 outburst. We find
our results to be significantly model-dependent. While all of the models tested
show best-fits consistent with truncation, some models allow the disc to extend
close to the innermost stable circular orbit (ISCO) and some require
substantial disc truncation. The different models yield a wide range in
best-fit values for the disc inclination. Our statistically best model has a
physical thermal Comptonization primary continuum, requires the disc to be
truncated at a radius larger than that of $approx$2 ISCO, and predicts a disc
inclination in agreement with that of the binary. Our preferred models have
moderate Fe abundance, $gtrsim$2 times the solar one. We have also tested the
effect of increasing the density of the reflecting medium. We find it leads to
an increase of the truncation radius, but also to an increase of the Fe
abundance, opposite to a previous finding.
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