A. D. Kuzmin

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 rangen

Secular evolution of the period and inclination of the magnetic to rotation axis and recycled pulsars

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

A Brief History of Radio Astronomy in the USSR

n 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.

Pulsars as independent clocks with high long-term stability

AbstractnWe present a brief review of observational manifestations of pulsars with giant pulses radio emission, based on the survey of the main properties of known pulsars with giant pulses, including our detection of 4 new pulsars with giant pulses.n

Pulsar time scale

Statistical analysis has been carried out of the relations between period and the ageP−tc, and the inclination of magnetic to rotation axis to the age α−tcof pulsars have been done.Up to characteristic agestc=3×107 years the period increases as expected for magneto-dipole radiation energy lossesP=Pm(1−exp(−t/τB))1/n−1. Best-fitting parameters of this approximation are the time-scale of the magnetic moment decay τB=4×106 years and breaking indexn=3.6. Fortc>3×107 years theP−tcdependence is significantly different.The inclination α of magnetic to rotation axis decreases versus age, showing a secular alignment of the axis. But this decrease continues also only up totc=3×107 years. Thus bothP−tcand α−tcdependencies indicate that most of the pulsars of agestc>3×107 years are not evolutionary continuations of more younger ones, but apparently represent another population of pulsars, which differ by their genetic history or physical processes. This population includes all known millisecond pulsars. We suggest, that this population is a so-called ‘recycled’ pulsar. The list of candidates of ‘recycled’ pulsars is presented.A new evaluation of the inclination of the magnetic to the rotation axis for 105 pulsars is presented.

The magnetic field structure of PSR 0809 + 74

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.

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

1 Radio Astronomy Studies at the Lebedev Physical Institute.- 2 Radio Astronomy Studies in Gorkii.- 3 Radio Astronomy at GAISH and IKI.- 4 GAO Department of Radio Astronomy.- 5 Radio Astronomy at the SAO.- 6 Byurakan Astrophysical Observatory and other Armenian Organisations.- 7 Crimean Astrophysical Observatory.- 8 Academy of Sciences of the Ukrainian SSR.- 9 IRE of the USSR Academy of Sciences.- 10 IZMIRAN.- 11 SibIZMIRAN.- 12 The RO of the Latvian Academy of Sciences.- 13 Leningrad State University.

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

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.