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The evolution of different types of quasi-periodic oscillations (QPOs) andthe coupled radiative/physical changes in the accretion disk are still poorlyunderstood. In a few black hole binaries it was found that fast evolution ofQPOs is associated with spectral variations. Such studies in other black holebinaries are important to understand the QPO phenomenon. For the black holetransient XTE J1817-330, we study fast QPO transitions and accompanyingspectral variations to investigate what causes the spectral variation duringthe QPO transition. Roy et al. (2011) found QPOs in ten RXTE observations ofXTE J1817-330. We found that, among the ten observations, only one observationshows erratic dips in its X-ray light curve. The power density spectra and thecorresponding energy spectra were extracted and analyzed for the dip andnon-dip sections of the light curve. We found that type-B $\sim$6 Hz QPOchanges 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 XTEJ1817-330. Based on our findings, we discuss the origin of fast evolution ofQPOs and spectral variations.

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