Pulsar timing at Urumqi Astronomical Observatory: observing system and results

Abstract

A B S T R A C TA pulsar timing system has been operating in the 18-cm band at the Urumqi Astronomical Observatory 25-m telescope since mid-1999. Frequency resolution allowing de-dispersion of the pulsar signals is provided by a 2 Â 128 Â 2:5 MHz filterbank/digitizer system. Observations of 74 pulsars over more than 12 months have resulted in updated pulsar periods and period derivatives, as well as improved positions. Comparison with previous measurements showed that the changes in period and period derivative tend to have the same sign and to be correlated in amplitude. A model based on unseen glitches gives a good explanation of the observed changes, suggesting that long-term fluctuations in period and period derivatives are dominated by glitches. In 2000 July, we detected a glitch of relative amplitude Dn/ n , 24 Â 10 29 in the Crab pulsar. The post-glitch decay appears similar to other large Crab glitches.

TMRT Observations of 26 Pulsars at 8.6 GHz

“…PSR J0837−4135 (B0835−41). This pulsar was discovered at 408 MHz by Large et al (1968) and Wang et al (2001) used the Nanshan radio telescope at Xinjiang Astronomical Observatory to update the period and period derivative. The 8.6 GHz profile for this pulsar ( Fig.…”

Pulsar timing for theFermigamma-ray space telescope

“…Four pulsars with no detectable radio emission are being observed with the Rossi X-ray Timing Explorer satellite (RXTE). The Urumqi Observatory (Wang et al 2001) is using a 25 m antenna to monitor 38 of the brighter radio pulsars. The goal is to build a database of rotation parameters that will allow folding of the gamma-rays as they are accumulated over the 5 to 10 year lifetime of the LAT.…”

Predicting the Starquakes in PSR J0537−6910

“…J0537 has a young characteristic timing age of 5 ; 10 3 yr, consistent with the 4000 yr estimated age of N157B, although we have shown this quantity to be actually decreasing with time ( Marshall et al 2004, hereafter M04). Many pulsars have also been shown to undergo sudden discontinuities (usually increases) in their rotation rates known as ''glitches'' (see, e.g., Alpar et al 1993Alpar et al ,1996Hobbs et al 2002;Johnston et al 1995;Jones 2002;Lyne et al 1993Lyne et al , 2000Pines & Alpar 1985;Ruderman et al 1998;Shemar & Lyne 1996;Wang et al 2000Wang et al , 2001aWong et al 2001). Although glitches have been detected in both young and old pulsars, they are predominately found in the younger ones ( c < 10 5 yr; Urama & Okeke 1999;Lyne et al 2000).…”