The Nançay radiotelescope in France is a large collecting area (7000m2) with receivers around 1.4, 1.7 and 3.5GHz. At this observatory, we are conducting frequent high-precision timing observations of 5 millisecond pulsars (PSR B1937+21, B1821-24 since 1988; J1643-1224, J1713+0747 and B1620-26 since 1996) with a swept frequency oscilllator based on a DDS as a dedisperser.

The most interesting result from these dense series of observations is the detection of several Extreme Scattering Events in direction of B1937+21 and possibly in direction of B1821-24 (Cognard, 1993, Nature, 366, 320; Cognard & Lestrade, 1996, in ASP Conf. Ser. Vol 105, Pulsars: Problems and Progress (San Francisco: ASP), 469; Lestrade, Rickett & Cognard 1998, A&A, 334, 1068). The flux density variations and TOA fluctuations observed have been used to estimate the size (several AU) and electron density (a few hundreds electrons cm−3) of the discrete ionised clouds localized in the interstellar medium that are thought to be responsible for this phenomena. The number of events recorded at Nançay in direction of B1937+21 yields the space density 105 – 106 pc−3 for these clouds. This density is very large and is about 100 times higher than the density estimated from Extreme Scattering Events observed in direction of extragalactic radio sources (Fiedler et al., 1994, ApJ, 430, 581). This might mean that the line of sight to B1937+21 is peculiar. This is being investigated with additional observations of a larger array of pulsars at Nançay with the Navy-Berkeley-Pulsar Processor (Figure 1) This processor NBPP (Foster et al., in ASP Conf. Ser. Vol 105, Pulsars: Problems and Progress (San Francisco: ASP), 25) has been used to acquire pulsar search data for 2 years at Nancay and we are now using its real-time folding capability.

Regular timing observations of millisecond and binary pulsars are made with the 64-m radio telescope at Kalyazin (Russia). Filterbank 160-channel receiver is used for observations at 0.6 GHz in two circular orthogonal polarization. Precise local time service (based upon a rubidium standards and hydrogen maser) is used for measurements of Times-of-Arrival (TOA) from radio pulsars. A local time scale is compared by GPS and TV-systems with the basic AT-scales (UTC(USNO) and UTC(SU)) within an accuracy about 50 ns per day. Recently the second 1.4 GHz receiver (250 kHz × 64 channels) was constructed and installed at Kalyazin radio telescope. There is a possibility to combine a part of the 1.4 GHz back-end with the 2.2 GHz front-end to produce timing observations at three frequencies simultaneously. We present a results of precise timing observations conducted by the Kalyazin pulsar system. Most of data were obtained at 0.6 GHz in 1997–1999. The data will be used for valuable applications in fundamental metrology, interstellar medium, general relativity and pulsar physics itself.

We present results of timing observations, obtained at the 100 m-Radiotelescope Effelsberg since 1994. The quality of the pulse arrival times, recorded with the coherent de-disperser EBPP since October 1996, is excellent. Our TOAs are well suited for the measurement of binary parameters of binary pulsars with short orbital periods. Some results are presented.

Accurate, long-term timing measurements of pulsars provide a powerful method to study a variety of astrophysical phenomena. For “normal”, slow pulsars, the dominant factors that limit the timing precision are the intrinsic timing noise and single pulse “jitter” (e.g. Cordes 1993). In fact, because the pulse jitter surpasses radiometer noise for sufficiently strong pulsars and no further improvement of the timing precision can be achieved by increasing the antenna gain, the timing of such sources can be very efficiently conducted with suitably equipped medium-size radiotelescopes.

We have been timing slow pulsars with the 32-m TCfA radiotelescope in Toruń, Poland, since July 1996, using a dual-channel, circular polarization L-band receiving system at frequencies around 1.7 GHz, and a 2 × 64 × 3 MHz channel pulsar backend, the Penn State Pulsar Machine - 2 (PSPM-2; for more details, see Konacki et al. 1999). Our gradually expanding source list currently includes 88 pulsars timed once a week with a millisecond precision using the observatory’s UTC-calibrated H-maser clock. Data analysis is routinely performed with the TEMPO software package. With a particularly dense, weekly sampling and a ≤1 ms timing precision, the TCfA program has a sensitivity to detect previously overlooked short period, low orbital inclination binaries, as well as very low-mass, planetary companions. In addition, it will be very useful in identifying and monitoring pulsar timing glitches and other forms of the timing noise.

A pulsar timing system has been set up using the 25-m Nanshan telescope of the Urumqi Astronomical Observatory. It uses a dual polarization receiver operating at 18 cm and a filterbank receiver. The data acquisition system is based on a PC using the Windows NT operating system. Timing properties of about 100 pulsars will be monitored with this system.

We present results of long-term timing of eclipsing binaries PSR B1744–24A and PSR B1957+20 at Arecibo, the VLA, and Green Bank. Both pulsars exhibit irregularities in pulsar rotation and orbital motion. Increases and decreases of the orbital period of PSR B1957+20 are of order ΔPb/Pb ∼ 10−7, varying on a time scale of a few years. Over a decade of observations, the orbital period of PSR B1744–24A has only decreased, with time scale |Pb/Ṗb| ∼ 200Myr. When the effects of orbital motion are removed from the timing data, long-term trends remain in the pulse phase residuals, with amplitudes of order 30 and 500 μs, respectively, for B1957+20 and B1744–24A. Such large “timing noise” is not seen in other spun-up pulsars (isolated or binary), leading us to conclude that it is a consequence of mass flow in the system. Possible causes include variations in the rotation of the pulsars and movement of the binary systems along the line of sight (perhaps due to gravitational interactions with outflowing matter).

Systematic effects currently dominate the timing residuals of the pulsar PSR J0437–4715. These systematics arise from transformations that occur during the propagation and detection of radio waves. The transformation properties of polarized radiation are related to the Lorentz group, and such effects may be represented using Lorentz transformations. These effects may be removed using the techniques of polarimetric self-calibration. Alternatively, an invariant profile may be formed from the polarimetric analogue of the Lorentz invariant I2 – Q2 – U2 – V2 and used for pulsar timing. Observations of PSR J0437–4715 are presented that show the consistency between these two techniques.

A planetary system around the pulsar B1257+12 has three planets A, B and C with the orbital periods of 25, 66 and 98 days, respectively (Wolszczan 1994). Dynamical properties of the system have been thoroughly studied by Rasio et al. (1993) and Malhotra (1993). They demonstrated that the gravitational interactions between planets B and C are significant enough to be detected. In such case, the motion of the system is no longer Keplerian and it is necessary to use a more precise description of motion in order to model the data properly. In this paper we derive a semi-analytical theory of motion assuming that the relative inclination of the orbits is small. We perform numerical simulations to show that our theory sucessfully predicts times of arrival of pulsar pulses and allows a determination of orbital inclinations and hence the masses of planets B and C.

We have extensively searched for periodic signals in the area of the soft gamma-ray repeater SGR 1900+14, at 430 and 1410 MHz with the Arecibo telescope. Our observations did not reveal the 5.16-s periodicity reported for the magnetar down to a 430-MHz flux density limit of 150 μJy. During the search we discovered a 226-ms radio pulsar, PSR J1907+0918. The period derivative implies the characteristic age for this pulsar is only 38 kyr. Independent evidence in support of this apparent youth are the unusually high degree of circular polarization and its relatively flat radio spectrum. The close proximity of PSR J1907+0918 to SGR 1900+14 suggests that they may have evolved from a massive binary system. Regardless of this possibility, it is presently not clear to us that SGR 1900+14 is associated with the supernova remnant G42.8+0.6.

The MIC photon counting detector developed at UCL has been upgraded to allow time resolved spectroscopic optical data to be acquired on periodical sources such as pulsars. First observing trials have been carried out on the Crab pulsar. The detector was phase locked to the pulsar period and a temporal resolution of 41.4μs employed. The phase locking allowed the co-addition of time slices over a large number of pulsar periods building up quantifiable spectroscopic data when observing in a flux limited regime.

High time resolution (41.4μs) observations of the Crab Pulsar have been undertaken on the 2.1m telescopes at San Pedro Martir and the Observatorio Astrofisico Guillermo Haro (MX) in January/February 1999. In our prelimenary analysis of the Crab Pulsar’s light curve we obtained a slightly narrow widths on the seondary pulse than that reported by Percival et al. Our data indicate the presence of substructures in the pulsar’s main pulse, though not statistically convincing.

Recent observations of the globular cluster 47 Tuc, made with the Parkes telescope at a wavelength of 20 cm, have resulted in the discovery of nine new millisecond pulsars (MSPs), all in binary systems. The number of timing solutions available has risen from two to 14. These results will make possible a more detailed study of the cluster dynamics.

We have used the effect of Shapiro delay of the pulsar radiation in the gravitational lensing approximation. The microlensing probabilities for pulsars located in globular clusters 47 Tuc (NGC 104) and M15 (7078) in the case of rather large impact parameters was calculated.

We report on the observation of highly-periodic, correlated variations in the rotation and pulse shape of PSR B1828–11. Three harmonically-related periodicities of 100, 500 and 250 days are seen in both the rotation rate and profile shape. The 0.7% modulation in period derivative is apparently related to oscillatory changes in the magnetospheric configuration. The origin of the periodic effects most likely lies in the free precession of the neutron star.

The phase residuals of PSR B1642-03 obtained during a 30-yr interval since 1969 to 1999 are discussed. Interpretation of observed cyclical residual changes in terms of free precession gives a wooble angle of 0.3 - 0.7 degrees.

The long time series of observations of four pulsars made by the Pushchino Large Phased Array are analyzed to describe a pulsar timing noise. The analysis was made after making a standard fitting procedure.

Pulse arrival times of pulsars have a high – though limited – degree of predictability: they show both discrete ‘glitches’, and continuous deviations from an analytic extrapolation of earlier data spans; they are ‘noisy’. This noise shows a strong dependence on a pulsar’s spindown age. Both types of noise can be understood as due to a loose coupling of the charged component of a pulsar’s moment of inertia to a neutral superfluid component, of relative moment of inertia usually below 1%, but reaching 10% in extreme cases. Differential spin rates δΩ/Ω of the two components are ≲ 10−3, usually only ≲ 10−5.

In assumption that pulsar gravitationally interacts with its surroundings the relationships between the pulsar rotational and orbital parameters are derived and the solutions for PSR B1620–26 and PSR B1822–09 are presented.

Results of timing observations of the glitching pulsar B1822–09 made practically simultaneously at widely separated frequencies of 0.1 and 1.6/2.3 GHz during seven years since 1991 to 1998 are discussed.

Parkes timing observations of 31 mostly young pulsars over nearly nine years are described. A total of 29 glitches were detected, of which 19 are previously unreported. Twelve glitches were seen in PSR J1341–6220, making this the most frequently glitching pulsar known, and the largest known glitch was detected in PSR J1614–5047. Distributions of glitch parameters were investigated.