A Study of the Pulsed Radio Emission from XTE J1810-197

We present observations of pulsed radio emission from the transient anomalous X-ray pulsar XTE J1810-197. Data were obtained over a period of 100 days beginning in 2006 May using a baseband recording system at the 26 m Mount Pleasant radio telescope operated by the University of Tasmania. Pulsed emission was detected in three frequency bands centered on 1.4, 4.8, and 8.4 GHz. The mean flux density varied significantly within all bands, but we obtained fewer detections toward the end of the observing period, and the monitoring program was eventually abandoned. Most interestingly, we observed changes in the pulse-to-pulse emission characteristics. The variance of the flux in 10 s integrations changed significantly during the span of our observations, but we did not have sufficient data to identify a clear secular trend. In addition, timing measurements confirmed that the neutron star's spin period derivative changed significantly on or around MJD 53935. © 2007. The American Astronomical Society. All rights reserved.