High-density reflection spectroscopy: I. A case study of GX 339-4
We present a broad-band spectral analysis of the black hole binary GX 339-4 with NuSTAR and Swift using high-density reflection model. The observations were taken when the source was in low-flux (LF) hard states during the outbursts in 2013 and 2015, and in a very high-flux (HF) soft state in 2015. The high-density reflection model can explain its LF spectra with no requirement for an additional low temperature thermal component. This model enables us to constrain the density in the disc surface of GX 339-4 in different flux states. The disc density in the LF state is log (ne/ cm^(−3)) ≈ 21, 100 times higher than the density in the HF state (log (n_e/ cm^(−3)) = 18.93^(+0.12)_(−0.16). A close-to-solar iron abundance is obtained by modelling the LF and HF broad-band spectra with variable density reflection model (Z_(Fe) = 1.50^(+0.12)_(−0.04)Z⊙ and Z_(Fe) = 1.05^(+0.17)_(−0.15)Z⊙, respectively).
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2019 January 6. Received 2019 January 6; in original form 2018 November 26. Published: 10 January 2019. JJ acknowledges support by the Cambridge Trust and the Chinese Scholarship Council Joint Scholarship Programme (201604100032). DJW acknowledges support from an STFC Ernest Rutherford Fellowship. ACF acknowledges support by the ERC Advanced Grant 340442. MLP is supported by European Space Agency (ESA) Research Fellowships. JFS has been supported by NASA Einstein Fellowship grant No. PF5-160144. JAG acknowledges support from the Alexander von Humboldt Foundation. This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center and the California Institute of Technology. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. We acknowledge support from European Space Astronomy Center (ESAC).
Accepted Version - 1901.01739.pdf
Published - stz095.pdf