Yu. P. Shitov

Radio spectra of pulsars

AbstractThe results of flux pulsar radioemission measurements at meter wavelengths, made at Pushchino Radio Astronomical Observatory of the Lebedev Physical Institute, are presented. Flux densities at 102, 85, 61 and 39 MHz have been measured for 85, 29, 37 and 23 pulsars correspondingly. Some of them were performed at all frequencies simultaneously.On the basis of these data and high frequencies data obtained by other authors, spectra of 52 pulsars were plotted. In practically all investigated pulsars we have detected a turn-over frequency at which the flux density of pulsar radioemission attained its maximum. Its mean value isvm=130±80 MHz. Averaged on many pulsars, the spectral index is negative in the 39–61 MHz frequency range

Pulsar PP 0943

(\bar \alpha _{39 - 61} = - 1.4 \pm 0.4)

Pulsar Time Scale - PT

and passes through zero at frequencies of about 100 MHz, becoming positive in the 100–400 MHz frequency range. It was noticed that the spectral index in the 100–400 MHz interval depends upon such pulsar periods as α100−=0.7logp+0.9. Using the spectra, more precise radio luminosities of pulsars have been computed.

Irregularity in the period of the pulsar B1822-09

Abstract We report the results of our search for pulsed radio emission from Geminga carried out in 1992, 1993 and 1996–1997 at 102.5 MHz using the BSA radiotelescope of the Pushchino Radioastronomy Observatory. The Geminga radio pulsar (PSR J0633+1746) was detected in all three observation periods. With the best signal to noise ratio Geminga was detected in records taken in 1993, when the maximum passband of the radiotelescope was used for the searches. The main criterion for radio pulsar detection was the presence of records containing the dominant spectral line at the rotation frequency of the pulsar Ω = 4.22 Hz in the amplitude spectra. The method of averaging the amplitude spectra, obtained for many days in February–June 1993, was used for the determination of the mean flux density of the Geminga radio emission at 102.5 MHz. We report the main parameters of the pulsar PSR J0633 + 1746, obtained from our observations. The mean flux S102 = 8(−2+3)mJy. The average pulse profile is very wide and has a shape like in X-rays (Halpern and Holt, 1992 [Natur, 357, 222]). The profile width on the 0.5 level W 0.5 ⋍ 120 ms , i.e. about 180°. The dispersion measure DM = 3.2±0.3 pc · cm−3. A timing analysis, which was performed for the best profiles, obtained from 1992 to 1997, yields values for the period P and derivative P, which are, within error limits, in agreement with the data published by Mayer-Hasselwander et al. (1994)[ApJ, 421, 276]. We discuss possible reasons for the extremely low radio luminosity of the Geminga pulsar.

Pulsars as independent clocks with high long-term stability

THE radio astronomy station of the P. N. Lebedev Physical Institute of the USSR Academy of Sciences in Pushchino (near Serpukhov) is investigating pulsars in the metre wavelength range. The east–west arm of the cross radio telescope DCR-1000 is used, and we can observe a pulsar for about 1 min each day.

The magnetic field structure of PSR 0809 + 74

Measurements of average pulse profiles made with a single linear polarization over the range 41-112 MHz are presented for PSR B0950+08. We show that the observed variable structure of the pulse profiles is a result of Faraday sinusoidal modulation of the pulse intensity with frequency. The rotation measure corresponding to this effect, RM ≈ 4r ad m −2 , is about 3 times greater than the published value of RM = 1.35 rad m −2 (Taylor et al. 1993).

Catalogue of time aligned profiles of 56 pulsars at frequencies between 102 and 10500 MHz

It is proposed to establish a new astronomical time scale - the pulsar time scale (PT). This scale is based on the very stable periodicity of the pulse sequence of a pulsar radio emission. The most stable pulsars such as PSR 0834+06, 0950+08, 1919+21 and the millisecond pulsar PSR 1937+214 are proposed as reference clocks for the new time scale. The pulsar time scale will keep both an interval and an epoch of the time and is more precise than existing UT and ET astronomical time scales.

Frequency dependence of characteristics of pulsars PSR 0031 – 07, 0320 + 39, 1133 + 16 and 2016 + 28

The results of long-term monitoring of irregularies in the rotation rate of the pulsar B1822-09 (J1825-0935) are presented. Observations of the pulsar carried out since 1991 on the Large Phased Array of the Pushchino Radio Astronomy Observatory have revealed a new type of irregularity in the rotation, which has the form of “slow glitches” and is manifest as a gradual exponential growth in the rotation frequency of the star over several hundred days. In 1995–2004, five slow glitches in the rotation frequency were observed, with relative amplitudes of Δν/ν ∼ (2.5-32) × 10−9. Together with these unusual “slow glitches” in the rotation frequency, two modest ordinary glitches, associated with sudden, jump-like increases in the rotation frequency, were also observed. The observed irregularities in the rotation frequency of the pulsar are analyzed in detail, and possible interpretations of the results are discussed.