Yu. P. Ilyasov

Giant Pulses—the Main Component of the Radio Emission of the Crab Pulsar

The paper presents an analysis of dual-polarization observations of the Crab pulsar obtained on the 64-m Kalyazin radio telescope at 600 MHz with a time resolution of 250 ns. A lower limit for the intensities of giant pulses is estimated by assuming that the pulsar radio emission in the main pulse and interpulse consists entirely of giant radio pulses; this yields estimates of 100 and 35 Jy for the peak flux densities of giant pulses arising in the main pulse and interpulse, respectively. This assumes that the normal radio emission of the pulse occurs in the precursor pulse. In this case, the longitudes of the giant radio pulses relative to the profile of the normal radio emission turn out to be the same for the Crab pulsar and the millisecond pulsar B1937+21, namely, the giant pulses arise at the trailing edge of the profile of the normal radio emission. Analysis of the distribution of the degree of circular polarization for the giant pulses suggests that they can consist of a random mixture of nanopulses with 100% circular polarization of either sign, with, on average, hundreds of such nanopulses within a single giant pulse.

Pulsar Time Scale - PT

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.

Pulsar VLBI experiment with the Kashima (Japan)–Kalyazin (Russia) baseline

Abstract The position of PSR0329+54 on the International Celestial Reference Frame was measured at epochs March 1995, May 1996, and May 1998. Our observations detected the proper motion of PSR0329+54. The position and proper motion agreed well with the position determined by Bartel et al. (1985) . From combined analysis with our data and that of Bartel, the proper motion of PSR0329+54 was determined: μ α =+17.4±0.3 mas yr −1 , μ δ =−11.0±0.3 mas yr −1 . These results are consistent with the value by Harrison et al. (1993) measured with the MERLIN interferometer. We also determined the coordinates of PSR0329+54 very accurately within the ICRF: α =03 h 32 m 59 s .3761±0 s .0002, δ =54°34′43′′.5119±0′′.0015 at 1995.

Millisecond Pulsar Timing at Kalyazin Observatory

Pulsar timing of millisecond pulsars are carried on at Kalyazin radio astronomical observatory (Russia) since 1995. Seven pulsars are observed at 0.6 GHz by full steerable 64-m dish radio telescope RT-64 and filter-bank receiver. The millisecond pulsar B1937+21 is being monitored at Kalyazin observatory (0.6 GHz) and Kashima space research centre of NICT (Japan) (2.3 GHz), simultaneously since 1996.

Deep surveys and the nonthermal noise of radio telescopes

The paper presents an analysis of catalogs of discrete radio sources and the results of deep surveys carried out with angular resolutions to 1.5″ and limiting flux densities to 9 μJy at frequencies from 80 MHz to 8.5 GHz using large radio telescopes around the world. We consider the influence on the sensitivity of a radio telescope of the nonthermal noise associated with variations in the total flux due to fluctuations in the number of unresolved sources with fluxes lower than the observed value that fall in the main lobe of the antenna beam when the direction in which the receiver is pointed is changed (the first component), and also due to sources with fluxes higher than the observed value that arrive in the scattering region of the telescope (the second component). With growth in the sensitivity and resolution of a telescope, the second component of this nonthermal noise determines to an appreciable extent the limiting capability of the telescope for carrying out deep surveys. We estimate the number of antenna beams per source that are required to reach a specified sensitivity in deep surveys. The results of our calculations are compared with data derived from catalogs and numerous surveys.

Pulsar Astrometry—Availabilities and Relativistic Aspects of a Pulsar Reference Frame

We propose a quasi-inertial four-dimensional reference frame in the solar system asymptotically-flat spacetime on the basis of pulsar astrometry techniques. The Pulsar Reference Frame (PRF) consists of the Pulsar Time Scale (PT) and the the Pulsar Reference System (PRS) on the sky.

Development of K4 Correlator for Pulsar VLBI: Japan-Russia Baseline

We are doing astrometric pulsar VLBI observation with Kashima-Kalyazin 7000 km baseline. K4 correlator is under the development for this observation program. When XF type correlator is used for pulsar processing with gating, attention should be paid to avoid fluctuation on delay result due to fractional bit effect. This influence is serious around the point that bit shift for delay tracking and pulsar period is synchronized. In this paper, the K4 correlation system is introduced and fractional bit effect on pulsar processing is explained.

Synchronizing the time and frequency standards at the Radio Astronomy Station, Physics Institute, USSR Academy of Sciences, with the state standard for time and frequency

The pulsar time scale [i, 2] is based on the pulsed radio emission from pulsars such as PSR 1937 + 214 (millisecond range), which imposes new requirements on the time service at the Radio Astronomy Station [3]. The standard deviation in the residual deviations in the time of arrival from the precalculated course is less than i Dsec [4]. In this connection, the error in the local time scale at the station should be less than I Dsec relative to that of the state standard of frequency and time in the USSR. For that purpose, the time and frequency service at the station has been equipped with high-stability quantum time and frequency standards and precision apparatus for matching them to the state scale.

Pulsars as independent clocks with high long-term stability

In 1967, pulsars were discovered, which were later identified with rotating neutron stars, whose exisence had been predicted by Landau, Baade, and Twicky in the1930s. They are currently considered to form by gravitational collapse at a stage where material for thermonuclear processes is exhausted and the internal pressure cannot support the gravitational forces. Gravitational collapse causes a star having 1-3 solar masses to contract to a density of I017 kg/m ~, while the radius is reduced by comparison with the solar value by almost a factor l0 s and is about i0 km. The conservation of momentum means that the rotational speed increases in the proportion to the reduction in radius. The rotation periods for over 400 pulsars are from a few milliseconds to a few seconds. On current views, a rotation speed of over 1200 sec -I in a neutron star would disrupt it on account of centrifugal forces.

Pulsar time scale

In this article a new time scale is proposed, that of pulsar time PT which is based on the regular sequence of time intervals between pulses of a pulsars radio emissions. In discussing variations in the arrival times of pulsar radio emissions, three kinds of variations in the radiation periods are described. PSR 0834 + 06 is used as the basic reference pulsar. Time scales are also determined for reference pulsars PSR 0905 + 08 and 1919 + 21. The initial parameters for the three reference pulsars needed for managing a PT scale are presented. The basic PT scale is defined as the continuous sequence of time intervals between radio-emission pulses of the basic reference pulsar.