A spectral and timing study of MAXI J1535-571, based on Swift/XRT, XMM-Newton and NICER observations obtained in fall 2017

TL;DR

This study analyzes spectral and timing data from multiple X-ray observatories to track the state evolution of the black hole transient MAXI J1535-571 during fall 2017, revealing state transitions and QPOs.

Contribution

First comprehensive spectral-timing analysis of MAXI J1535-571 using Swift/XRT, XMM-Newton, and NICER data, detailing its state evolution and QPO detection.

Findings

Black hole binary in bright state with flux peak of 3.71e-7 erg/cm^2/s.

Transitions from low-hard to high-soft states and back observed.

Type-C QPOs detected during hard states.

Abstract

We present a spectral-timing analysis of observations taken in fall 2017 of the newly detected X-ray transient MAXI J1535-571. We included 38 Swift/XRT window timing mode observations, three XMM-Newton observations and 31 NICER observations in our study. We computed the fundamental diagrams commonly used to study black hole transients, and fitted power density and energy spectra to study the evolution of spectral and timing parameters. The observed properties are consistent with a bright black hole X-ray binary ($F_{\mathrm{0.6-10 keV}}^{\mathrm{max}}=3.71\pm0.02\times10^{-7}$ erg cm$^{-2}$ s$^{-1}$) that evolves from the low-hard-state to the high-soft state and back to the low-hard-state. In some observations the power density spectra showed type-C quasi-periodic oscillations, giving additional evidence that MAXI J1535-571 is in a hard state during these observations. The duration of the soft state with less than ten days is unusually short and observations taken in spring 2018 show that MAXI J1535-571 entered a second (and longer) soft state.