NICER uncovers the transient nature of the type-B quasi-periodic oscillation in the black hole candidate MAXI J1348-630

TL;DR

This study analyzes the transient type-B QPO in MAXI J1348-630, revealing it is linked to a redistribution of accretion power favoring the Comptonised emission, possibly related to jet activity.

Contribution

It provides the first detailed spectral-timing analysis of the transient nature of type-B QPOs in this black hole candidate, highlighting the energy-dependent spectral changes during QPO transitions.

Findings

Type-B QPOs are associated with increased Comptonised emission.

The transition involves a decrease in disk flux and an increase in Comptonised flux.

The total flux remains relatively constant during QPO appearance/disappearance.

Abstract

We present a systematic spectral-timing analysis of a fast appearance/disappearance of a type-B quasi-periodic oscillation (QPO), observed in four NICER observations of MAXI J1348-630. By comparing the spectra of the period with and without the type-B QPO, we found that the main difference appears at energy bands above ~2 keV, suggesting that the QPO emission is dominated by the hard Comptonised component. During the transition, a change in the relative contribution of the disk and Comptonised emission was observed. The disk flux decreased while the Comptonised flux increased from non-QPO to type-B QPO. However, the total flux did not change too much in the NICER band. Our results reveal that the type-B QPO is associated with a redistribution of accretion power between the disk and Comptonised emission. When the type-B QPO appears, more accretion power is dissipated into the Comptonised region than in the disk. Our spectral fits give a hint that the increased Comptonised emission may come from an additional component that is related to the base of the jet.