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Evidence for Free Precession in the Pulsar B1642-03
T.V. Shabanova, A.G. Lyne, J.O. Urama
Astrophysical Journal, 552, 321-325 (2001)
   Abstract. We present an analysis of the timing data of the pulsar B1642-03, collected over a span of 30 years between 1969 and 1999. During this interval, the timing residuals exhibit cyclical changes with amplitude varying from 15 to 80 ms and spacing of maxima varying from 3 to 7 yr. Interpretation of these observed cyclical changes in terms of free precession suggests a wobble angle of about 0.8 degrees.

A.D. Kuzmin and B.Ya. Losovsky
   Abstract. We present the results of the first low frequency measurements of the flux densities of a large sample of millisecond pulsars (MSPs) at 102 and 111 MHz. Combining our observations with data at higher frequencies borrowed from the literature, we constructed the spectra of 30 MSPs in the 0.1 to 4.8 GHz frequency range. Our flux density measurements extend the known spectra of MSPs to the lowest frequency to date. The coverage of a low frequency range allows us to search for low frequency turn-over, which is often observed for normal pulsars. We find that spectra of MSPs differ from those of normal pulsars, showing no low-frequency turn-over typical of normal pulsars. We suggest that the geometry of the radio emission region of MSPs differs from that of normal pulsars: the magnetic field configuration in MSPs' magnetospheres may deviate from that of a pure dipole and/or the radio emission region may be radially compressed. Monochromatic luminosities at this low frequency and the integral luminosity over the 0.1-4.8 GHz frequency range were determined and their dependence on other pulsar parameters analyzed.

T. V. Shabanova
   Abstract. Two glitches have been detected in the pulsar PSR B1822-09. The first glitch occured around MJD 49615 and was characterized by a fractional increase in rotational frequency of 2*10^{-10}. The second glitch occured 325 days after the first one and caused a fractional change in frequency of 5*10^{-9}. Of interest was the post-glitch behaviour. The rotational frequency immediately after the second glitch began slowly, gradually increasing which lasted ~620 days. As a result of the slow increase a fractional change in rotation frequency for this period of time made up 7*10^{-9}. This event was accompanied by a decrease in the frequency derivative, which having reached minimum magnitude ~0.4 percentage less than the original value, returned to its initial value.

T. V. Shabanova, J.O.Urama
Astron. Astrophys. 354, 960-964 (2000)
   Abstract. An analysis of four glitches observed in the pulsar B1822-09 during the period 1994 - 1999 is presented. The main distinguishing feature of these glitches is that the sudden increase in rotational frequency is accompanied by a decrease in the frequency derivative. The largest change of the frequency derivative was measured in the fourth glitch. This glitch occured around MJD 51054 and was characterized by rather a small increase in rotational frequency of Delta_nu/nu=7*10^{-9}, but a large decrease in the frequency derivative by ~2.4 percent. The first two glitches were observed practically simultaneously at two frequencies of 0.1 GHz in Pushchino, Russia and 1.6/2.3 GHz at HartRAO, South Africa. An analysis of the high- and low frequency timing data showed that glitches did not affect the pulse arrival times at different frequencies within 2 ms. Glitch signature was identical in the wide frequency range from 0.1 to 2.3 GHz. In addition, a more exact value of the dispersion measure was measured to be 19.383(3) pc*cm^{-3}.

T. V. Shabanova
Astrophysical Journal, 453, 779-782 (1995)
   Abstract. The data set of available pulse arrival times of the pulsar PSR B0329+54, including the JPL timing data between 1968 and 1983 and the Pushchino timing data between 1978 and 1994, is analyzed. It is shown that a quasi-sinusoidal modulation with a period of 16.9 years exists in the timing residuals. This periodicity can be interpreted as evidence for the existence of a planet-like body orbiting the pulsar PSR B0329+54 with the 16.9-yr orbital period. The planet has the minimum mass of about twice the mass of the Earth, and moves in eccentric orbit (e=0.23) with the semimajor axis 7.3 AU. The existence of 3-yr periodicity in arrival times, claimed by Demianski and Proszynski in 1979, is verified. It manifested itself distinctly in the JPL data only after removing the main 16.9-yr periodicity.


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