IGR J00291+5934 is a 598 Hz X-ray Pulsar

IGR J00291+5934 (Eckert et al. 2004, ATel #352) was observed by the RXTE PCA instrument on Dec. 3, 2004 at 06:17 (UTC) for approximately 2000 seconds exposure. The source was detected with a flux of 35 mCrab (2-10 keV). Pulsations were detected at a barycentric frequency of 598.88 Hz, with a pulsed amplitude of approximately 6%. There is no evidence of any harmonics at half or double this frequency, suggesting that it is the fundamental rotation period of a neutron star.