Relativistic Reflection and Reverberation in GX 339-4 with NICER and NuSTAR

Wang J, Kara E, Steiner JF, Garcia J, Homan J, Neilsen J, Marcel G, Ludlam RM, Tombesi F, Cackett EM, Remillard RA (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Astrophysical Journal American Astronomical Society

Book Volume: 899

Article Number: 44

Journal Issue: 1

DOI: 10.3847/1538-4357/ab9ec3

Abstract

We analyze seven Neutron Star Interior Composition Interior Explorer (NICER) and Nuclear Spectroscopic Telescope Array epochs of the black hole X-ray binary GX 339-4 in the hard state during its two most recent hard-only outbursts in 2017 and 2019. These observations cover the 1-100 keV unabsorbed luminosities between 0.3% and 2.1% of the Eddington limit. With NICER's negligible pileup, high count rate, and unprecedented time resolution, we perform a spectral-timing analysis and spectral modeling using relativistic and distant reflection models. Our spectral fitting shows that as the inner disk radius moves inward, the thermal disk emission increases in flux and temperature, the disk becomes more highly ionized, and the reflection fraction increases. This coincides with the inner disk increasing its radiative efficiency around ∼1% Eddington. We see a hint of the hysteresis effect at ∼0.3% of Eddington; the inner radius is significantly truncated during the rise (>49R g ), while only a mild truncation (∼5R g ) is found during the decay. At higher frequencies (2-7 Hz) in the highest-luminosity epoch, a soft lag is present whose energy dependence reveals a thermal reverberation lag with an amplitude similar to previous findings for this source. We also discuss the plausibility of the hysteresis effect and the debate of the disk truncation problem in the hard state.

Authors with CRIS profile

Javier Garcia Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut

Involved external institutions

Massachusetts Institute of Technology (MIT) US United States (USA) (US) University of Maryland US United States (USA) (US) Wayne State University (WSU) US United States (USA) (US) Villanova University US United States (USA) (US) California Institute of Technology (Caltech) US United States (USA) (US) Eureka Scientific US United States (USA) (US)

How to cite

APA:

Wang, J., Kara, E., Steiner, J.F., Garcia, J., Homan, J., Neilsen, J.,... Remillard, R.A. (2020). Relativistic Reflection and Reverberation in GX 339-4 with NICER and NuSTAR. Astrophysical Journal, 899(1). https://doi.org/10.3847/1538-4357/ab9ec3

MLA:

Wang, Jingyi, et al. "Relativistic Reflection and Reverberation in GX 339-4 with NICER and NuSTAR." Astrophysical Journal 899.1 (2020).

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