A catalog of low frequency quasi-periodic oscillations from cygnus X-2

Abstract

We present the results of timing analysis of archival Rossi X-ray Timing Explorer observations of the neutron star (NS) X-ray binary Cygnus X-2. This work focuses on the search for low-frequency ($\le$100 Hz) quasi-periodic oscillations (QPOs) from Cygnus X-2 performed using a semi-automatic analysis pipeline. The aim of the presented catalog is to expand the availability of timing information pertaining to neutron star low mass X-ray binaries (LMXBs) to facilitate detailed comparison with black hole LMXBs. The search identified QPOs in 88 out of 582 observations. We classify the detected QPOs into horizontal, normal, and flaring branch oscillations (HBOs, NBOs, and FBOs) respectively, analogous to the classification of black hole (BH) QPOs into type-C, type-B, and type-A. We identify 79 observations with HBOs, 8 with NBOs and no FBOs in the dataset. We further identify an observation that shows the presence of a NBO and HBO simultaneously.