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We report the discovery of kHz quasi periodic oscillations (QPOs) in threeRossi X-ray Timing Explorer observations of the low mass X-ray binary (LMXB)XTE J1701-407. In one of the observations we detect a kHz QPO with acharacteristic frequency of 1153 +/- 5 Hz, while in the other two observationswe detect twin QPOs at characteristic frequencies of 740 +/- 5 Hz, 1112 +/- 17Hz and 740 +/- 11 Hz, 1098 +/- 5 Hz. All detections happen when XTE J1701-407was in its high intensity soft state, and their single trial significance arein the 3.1-7.5 sigma range. The frequency difference in the centroidfrequencies of the twin kHz QPOs (385 +/- 13 Hz) is one of the largest seentill date. The 3-30 keV fractional rms amplitude of the upper kHz QPO variesbetween ~18 % and ~30 %. XTE J1701-407, with a persistent luminosity close to 1% of the Eddington limit, is among the small group of low luminosity kHz QPOsources and has the highest rms for the upper kHz QPO detected in any source.The X-ray spectral and variability characteristics of this source indicate itsatoll source nature.

Discovery of twin kHz quasi periodic oscillations in the low mass X-ray binary XTE J1701-407