Timing analysis of Swift J1658.2–4242's outburst in 2018 with Insight-HXMT, NICER and AstroSat

Abstract

We present the observational results from a detailed timing analysis of the black hole candidate Swift J1658.2–4242 during its 2018 outburst with the observations of Hard X-ray Modulation Telescope (Insight-HXMT), Neutron Star Interior Composition Explorer (NICER) and AstroSat in 0.1–250keV. The evolution of intensity, hardness and integrated fractional root mean square (rms) observed by Insight-HXMT and NICER are presented in this paper. Type-C quasi-periodic oscillations (QPOs) observed by NICER (0.8–3.5Hz) and Insight-HXMT (1–1.6Hz) are also reported in this work. The features of the QPOs are analyzed with an energy range of 0.5–50keV. The relations between QPO frequency and other characteristics such as intensity, hardness and QPO rms are carefully studied. The timing and spectral properties indicate that Swift J1658.2–4242 is a black hole binary system. Besides, the rms spectra of the source calculated from the simultaneous observation of Insight-HXMT, NICER and AstroSat support the Lense-Thirring origin of the QPOs. The relation between QPO phase lag and the centroid frequency of Swift J1658.2–4242 reveals a near zero constant when <4Hz and a soft phase lag at 6.68Hz. This independence follows the same trend as the high inclination galactic black hole binaries such as MAXI J1659–152.