2011ATel.3542....1G

RXTE/PCA observed the new source, Swift J1834.9-0846 (D'Elia et al. GCN Circ. 12253, Guiriec et al. 12255) on 2011 August 9-10, for a net exposure time of 9.7 ks. We performed a timing analysis using the barycentered photon arrival times in the 2-10 keV band and detected a coherent pulsation at 0.402853(2) Hz which corresponds to a spin period of 2.482295 s. Note that an earlier PCA observation on 2011 August 9 of the same field with a 3.4 ks exposure did not reveal the pulsed signal clearly but it does confirm the signal at a consistent frequency. The pulse profile shows a broad structure covering about 50% of the spin phase with an evidence of a less significant and shorter second structure. This is the only pulsed signal detected within the 1 degree RXTE field of view. To confirm the association of this pulsar with Swift J1834.9-0846, we also analyzed the Swift/XRT data. We see the signal at the same frequency in the XRT observation of 2011 August 9, but at lower significance. The association of the RXTE pulsar with Swift J1834.9-0846 thus needs to be unambiguously confirmed with further longer XRT exposures or with other low-background X-ray instruments, such as Chandra.