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

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 thiswork consist of two strictly simultaneous observations performed with XMM-Newton (X-rays: 0.7-10 keV), VLT/HAWK-I (K-s band, 2.2 mu m) andVLT/VISIR (Mand 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 anticorrelation dip at positive lags. We detect a near-IR QPO (2.5 sigma) at 2.07 +/- 0.09 Hz simultaneously with an X-ray QPO at approximately the same frequency (f(0) = 2.25 +/- 0.05). 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 time-scales. 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 the disc and jet.

Automated summary

This study presents the results of the fast X-ray/infrared variability analysis of the black hole transient MAXI J1535-571, showing a strong asymmetric anticorrelation between X-ray and near-IR light curves. The detection of a near-IR QPO and simultaneous X-ray QPO at approximately the same frequency suggests a possible misalignment between the disc and jet in scenarios for fast IR variability.