Fast transition of type-B QPO in the black hole transient XTE J1817-330

TL;DR

This paper investigates the rapid transition of type-B to type-A QPOs in XTE J1817-330, revealing associated spectral changes and providing insights into the physical mechanisms behind QPO evolution in black hole binaries.

Contribution

It presents the first detailed analysis of a fast QPO transition and spectral variation in XTE J1817-330, highlighting the connection between QPO type change and spectral state.

Findings

Type-B QPOs transition to type-A within tens of seconds.

Spectral variations accompany the QPO transition.

The flux decreases during the QPO transition.

Abstract

The evolution of different types of quasi-periodic oscillations (QPOs) and the coupled radiative/physical changes in the accretion disk are still poorly understood. In a few black hole binaries it was found that fast evolution of QPOs is associated with spectral variations. Such studies in other black hole binaries are important to understand the QPO phenomenon. For the black hole transient XTE J1817-330, we study fast QPO transitions and accompanying spectral variations to investigate what causes the spectral variation during the QPO transition. Roy et al. (2011) found QPOs in ten RXTE observations of XTE J1817-330. We found that, among the ten observations, only one observation shows erratic dips in its X-ray light curve. The power density spectra and the corresponding energy spectra were extracted and analyzed for the dip and non-dip sections of the light curve. We found that type-B $\sim$6 Hz QPO changes into type-A QPO in a few tens of seconds along with a flux decrease. This transient evolution is accompanied with a significant spectral variation. We report a transient QPO feature and accompanying spectral variation in XTE J1817-330. Based on our findings, we discuss the origin of fast evolution of QPOs and spectral variations.