Fast infrared variability from the black-hole candidate MAXI J1535$-$571 and tight constraints on the modelling

TL;DR

This study analyzes simultaneous X-ray and infrared variability in the black-hole candidate MAXI J1535$-$571, revealing correlated quasi-periodic oscillations and constraints on the disk-jet alignment, informing models of IR variability.

Contribution

It provides the first simultaneous multi-wavelength analysis of IR and X-ray variability in this source, offering new insights into the origin of IR variability and disk-jet misalignment.

Findings

Detection of near-IR QPO at 2.07 Hz

Strong asymmetric anti-correlation at positive lags

Evidence for disk-jet misalignment

Abstract

We present the results regarding the analysis of the fast X-ray/infrared (IR) variability of the black-hole transient MAXI J1535$-$571. The data studied in this work consist of two strictly simultaneous observations performed with XMM-Newton (X-rays: 0.7$-$10 keV), VLT/HAWK-I ($K_{\rm s}$ band, 2.2 $\mu$m) and VLT/VISIR ($M$ and $PAH2$_$2$ bands, 4.85 and 11.88 $\mu$m respectively). The cross-correlation function between the X-ray and near-IR light curves shows a strong asymmetric anti-correlation dip at positive lags. We detect a near-IR QPO (2.5 $\sigma$) at $2.07\pm0.09$ Hz simultaneously with an X-ray QPO at approximately the same frequency ($f_0=2.25\pm0.05$). From the cross-spectral analysis a lag consistent with zero was measured between the two oscillations. We also measure a significant correlation between the average near-IR and mid-IR fluxes during the second night, but find no correlation on short timescales. We discuss these results in terms of the two main scenarios for fast IR variability (hot inflow and jet powered by internal shocks). In both cases, our preliminary modelling suggests the presence of a misalignment between disk and jet.