QPO Detection for HMXB Transient Pulsar 1A~0535+262 Observed with RXTE-PCA

We report the detection of quasi-periodic oscillations (QPO) at ~19 mHz and ~4 mHz in the transient high-mass Be/X-ray binary pulsar 1A~0535+262 using data from the RXTE observatory. The observations used in the present work were carried out during the X-ray out- bursts in 2010 January-April-August and 2011 Feb-May-July-August. The ~19 mHz QPO in 1A~0535+262 was detected in two Rossi Explorer Timing Experiment (RXTE) Proportional Counter Array (PCA) observations during the declining phase of its 2010 January-April-August outburst and ~4 mHz QPO in 2011 Feb-May-July-August. However, this QPO was rarely detected during other two outbursts of the pulsar. Though QPOs between 27-72 mHz were reported earlier in the pulsar, the ~19 mHz and ~4 mHz QPOs were detected for the first time in this pulsar. The results of our analysis of RXTE data during two outbursts of the pulsar are presented in the paper.