X-ray spectral and timing evolution of MAXI J1727–203 with NICER
We present a detailed X-ray spectral and variability study of the full 2018 outburst of MAXI J1727–203 using NICER observations. The outburst lasted approximately four months. Spectral modelling in the 0.3–10 keV band shows the presence of both a soft thermal and a hard Comptonised component. The analysis of these components shows that MAXI J1727–203 evolved through the soft, intermediate, and hard spectral states during the outburst. We find that the soft (disc) component was detected throughout almost the entire outburst, with temperatures ranging from ∼0.4 keV, at the moment of maximum luminosity, to ∼0.1 keV near the end of the outburst. The power spectrum in the hard and intermediate states shows broad-band noise up to 20 Hz, with no evidence of quasi-periodic oscillations. We also study the rms spectra of the broad-band noise at 0.3−10 keV of this source. We find that the fractional rms increases with energy in most of the outburst except during the hard state, where the fractional rms remains approximately constant with energy. We also find that, below 3 keV, the fractional rms follows the same trend generally observed at energies >3 keV, a behaviour known from previous studies of black holes and neutron stars. The spectral and timing evolution of MAXI J1727–203, as parametrised by the hardness–intensity, hardness–rms, and rms–intensity diagrams, suggest that the system hosts a black hole, although we could not rule out a neutron star.
© 2020 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 2020 July 20. Received 2020 July 20; in original form 2020 April 8. Published: 06 August 2020. This work is based on observations made by the NICER X-ray mission supported by NASA. This research has made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory. This research has made use of the MAXI light curve provided by RIKEN, JAXA, and the MAXI team. This research has also made use of Swift/BAT transient monitor results provided by the Swift/BAT team. KA acknowledges support from a UGC–UKIERI Phase 3 Thematic Partnership (UGC–UKIERI-2017-18-006; PI: P. Gandhi). KA especially acknowledges Dr. Keith Arnaud for his help with the X-ray tool XSPEC. DA and DJKB acknowledge support from the Royal Society. VAC acknowledges support from the Royal Society International Exchanges 'The first step for High-Energy Astrophysics relations between Argentina and UK' and from the Spanish Ministerio de Ciencia e Innovación under grant AYA2017-83216-P. LZ and AC acknowledge support from the Royal Society Newton International Fellowship. RML acknowledges the support of NASA through Hubble Fellowship Program grant HST-HF2-51440.001. Data Availability: The data underlying this article are publicly available in the High Energy Astrophysics Science Archive Research Center (HEASARC) at https://heasarc.gsfc.nasa.gov/db-perl/W3Browse/w3browse.pl.
Accepted Version - 2007.11373.pdf
Published - staa2168.pdf