Radio Luminosities Of Pulsars Research Articles

Energetic requirements of the gamma-ray emission from pulsars: A nonparametric analysis of the data in the Fermi-LAT 12-Year Catalog

The prevalent view that the radio-loud gamma-ray pulsars have gamma-ray luminosities that exceed their radio luminosities by several orders of magnitude is based on the assumption that the decay with distance of their gamma-ray fluxes obeys the inverse-square law as does that of their radio fluxes. The results presented here, of testing the hypothesis of independence of luminosities and distances of gamma-ray pulsars by means of the Efron–Petrosian statistic, do not uphold this assumption however: they imply that the observational data in the Fermi-LAT 12-Year Catalog are consistent with the dependence S∝D−3/2 of the flux densities S of the gamma-ray pulsars on their distances D at substantially higher levels of significance than they are with the dependence S∝D−2. These results, which were theoretically predicted in Ardavan (2021), are not incompatible with the requirements of the conservation of energy because the radiation process by which the superluminally moving current sheet in the magnetosphere of a neutron star has been shown to generate the slowly decaying gamma-ray pulses is intrinsically transient: the difference in the fluxes of power across any two spheres centred on the star is balanced by the change with time of the energy contained inside the shell bounded by those spheres. Once the over-estimation of their values is rectified, the luminosities of gamma-ray pulsars turn out to have the same range of values as do the luminosities of radio pulsars. This conclusion agrees with that reached earlier on the basis of the smaller data set in the Second Fermi-LAT Catalog of Gamma-ray Pulsars.

Parameters of radio pulsars in binary systems and globular clusters

The parameters of radio pulsars in binary systems and globular clusters are investigated. It is shown that such pulsars tend to have short periods (of the order of several milliseconds). Themagnetic fields of most of the pulsars considered are weak (surface fields of the order of 108−109 G). This corresponds to the generally accepted view that short-period neutron stars are spun up by angular momentum associated with the stellar wind from a companion. However, the fields at the light cylinders in these objects are two to three orders of magnitude higher than for the main population of single neutron stars. The dependence of the pulse width on the period does not differ from the corresponding dependences for single pulsars, assuming the emission is generated inside the polar cap, at moderate distances from the surface or near the light cylinder. The radio luminosities of pulsars in binary systems do not show the correlation with the rate of loss of rotational energy that is characteristic for single pulsars, probably due to the influence of accreting matter from a companion. Moreover, accretion apparently decreases the power of the emergent radiation, and can explain the observed systematic excess of the radio luminosity of single pulsars compared to pulsars in binary systems. The distributions and dependences presented in the article support generally accepted concepts concerning the processes occurring in binary systems containing neutron stars.

RADIO EFFICIENCY OF PULSARS

We investigate radio emission efficiency $\xi$ of pulsars and report a near linear inverse correlation between $\xi$ and the spindown power $\dot E$, as well as a near linear correlation between $\xi$ and pulsar age $\tau$. This is a consequence of very weak, if any, dependences of radio luminosity $L$ on pulsar period $P$ and period derivative $\dot{P}$, in contrast to X-ray or $\gamma$-ray emission luminosities. The analysis of radio fluxes suggests that these correlations are not due to a selection effect, but are intrinsic to the pulsar radio emission physics. We have found that, although with a large variance, the radio luminosity of pulsars is $\left<L\right>\approx 10^{29} \,{\rm erg/s}$, regardless of the position in the $P-\dot P$ diagram. Within such a picture, a model-independent statement can be made that the death line of radio pulsars corresponds to an upper limit in the efficiency of radio emission. If we introduce the maximum value for a radio efficiency into Monte Carlo-based population syntheses we can reproduce the observed sample using the random luminosity model. The Kolmogorov-Smirnov test on a synthetic flux distribution shows high probability of reproducing the observed distribution. Our results suggests that the plasma responsible for generating radio emission is produced under similar conditions regardless of pulsar age, dipolar magnetic field strength, and spin-down rate. The magnetic fields near the pulsar surface are likely dominated by crust-anchored magnetic anomalies, which do not significantly differ among pulsars, leading to similar conditions for generating electron-positron pairs necessary to power radio emission.

On the Mechanism of X-ray Emission from Radio Pulsars

The correlations between the luminosities of radio pulsars in various wavebands and the magnetic fields at the light cylinder suggest that the observed emission is generated in outer layers of the pulsar magnetospheres by the synchrotron mechanism. The formula for calculating the X-ray luminosity LX of radio pulsars is derived in the framework of the synchrotron model. It is shown that LX depends strongly on the parameter This raises the possibility of predicting the detection of X-ray emission from more than a hundred known radio pulsars.

On the mechanism of X-ray emission from radio pulsars

We discuss the correlations between the luminosities of radio pulsars in various frequency ranges and the magnetic fields on the light cylinder. These correlations suggest that the observed emission is generated in outer layers of the pulsar magnetospheres by the synchrotron mechanism. To calculate the distribution functions of the relativistic particles in the generation region, we use a model of quasi- linear interactions between the waves excited by cyclotron instability and particles of the primary beam and the secondary electron-positron plasma. We derive a formula for calculating the X-ray luminosity Lx of radio pulsars. A strong correlation was found between Lx and the parameter ˙ P−15/P 3.5 ,w hereP is the neutron-star rotation period, in close agreement with this formula. The latter makes it possible to predict the detection of X-ray emission from more than a hundred (114) known radio pulsars. We show that the Lorentz factors of the secondary particles are small (γp =1 .5-8.5), implying that the magnetic field near the neutron-star surface in these objects is multipolar. It follows from our model that almost all of the millisecond pulsars must emit X-ray synchrotron radiation. This conclusion differs from predictions of other models and can be used to test the theory under consideration. The list of potential X-ray radiators presented here can be used to search for X-ray sources with existing instruments. c � 2003 MAIK "Nauka/Interperiodica".

Linear Wave Beams in the Crust of a Neutron Star

The propagation of axially symmetric wave beams near the equatorial plane of a neutron star is studied. These waves are excited by a spatially bounded perturbation in the form of a transverse magnetic field applied to the inner boundary of the crust of the star. For a small ratio of the perturbed to the unperturbed magnetic field, a linear theory can be employed to solve the evolution equation. This condition is satisfied in the crust plasma of a neutron star for typical radio luminosities of pulsars. The resulting simple, exact solution in the form of linear gaussian beams exists without additional conditions on the dissipation, dispersion, and narrowness of the beams, if the velocity c n of these waves is constant. The latter requirement is well satisfied for the plasma in neutron star crusts. The width of the gaussian beam also depends weakly on position.

Pulsed optical emission by radio pulsars

The luminosity L of radio pulsars due to synchrotron radiation by the primary beam at the magnetosphere periphery is derived. There is a strong correlation between the observed optical luminosities of radio pulsars and the parameter $$\dot P/P^4$$ (where P is the pulsar period). This correlation predicts appreciable optical emission from several dozen pulsars, in particular, from all those with P<0.1 s. Agreement with optical observations can be achieved for Lorentz factors of the secondary plasma γp=2–13. Plasma with such energies can be produced only when the magnetic-field structure near the neutron-star surface deviates substantially from a dipolar field. The peak frequency of the synchrotron spectrum should shift toward higher values as the pulsar period P decreases; this is, in agreement with observational data for 27 radio pulsars for which emission has been detected outside the radio band.

The Statistics of Radio Pulsars: A Spark Model

We use Monte Carlo techniques to relate a theoretical pulsar emission model to the observed distributions of pulse period, magnetic field strength, distance, and luminosity of radio pulsars. We assume that the radio luminosity of pulsars is proportional to the gap potential and current flow from the polar cap. The current is assumed to be nonuniform and clustered in sparks, but only those sparks swept by the line of sight contribute to the observed radio luminosity. We test our model by using the Ruderman-Sutherland vacuum gap potential and find that the simulated distributions are consistent with those observed, with the exception of the period distribution. The model predicts more long-period pulsars than are observed. This discrepancy may result from the model itself, a reduced sensitivity of surveys to long-period pulsars, or the nondipole spin-down of pulsars.

The Radio Luminosity of Pulsars and the Distribution of Interstellar Electron Density

AbstractThe radio luminosities of pulsars are given as functions of their period and the time variation of the period. The parameters of that dependence are calculated and independent distances are determined for pulsars. The average electron densities toward the pulsars are determined from the known dispersion measures. The results obtained are used to study the large-scale electron density distribution in the Galaxy. The distribution maximum lies in the vicinity of the Sagittarius spiral arm. The electron density falls off exponentially in the regions between spiral arms.

Pulsar radio luminosities and the magnetic moments of neutron stars

Using equations from the theory of pulsar radio emission, the radio luminosities of pulsars and the magnetic moments of neutron stars are calculated from existing observational data.

The radio luminosity of pulsars and the distribution of electron density in the galaxy

Radio luminosities of pulsars depend on their periods and derivatives of periods. The parameters of these dependences and the independent distances for 288 pulsars are determined. Known dispersion measures are used for determination of the mean electron densities in the direction of pulsars. The results obtained are used for investigation of the large-scale distribution of electron concentration in the galaxy. The maximum value of that distribution is found at a distance of 9 kpc from the galactic center in the Sagittarius arm. In the interarm regions electron density decreases roughly exponentially.

Radio luminosities of pulsars and the electron density distribution in the galaxy

The radio luminosities o f pulsars are given as functions of their period and the time variation of the period. The parameters of that dependence are calculated and independent distances are determined for 288 pulsars. The average electron densities toward the pulsars are determined from the known dispersion measures. The results obtained are used to study the large-scale electron density distribution in the Galaxy at a distance of 4-5 kpc from the sun. The distribution maximum lies at a distance of 9 kpc from the center o f the Galaxy in the vicinity of the Sagittarius spiral arm. The electron density falls o f f exponentially in the regions between arms (toward the Perseus and Centaurus spiral arms).

Does the Radio Luminosity of Pulsar Grow up in its Later Stage?

In usual statistical analyses, because of diversities of proper parameters of pulsars, some interesting features might be smeared. In order to remove these diversities, we use the mean values for all quantities of pulsars, instead of values of individual pulsar, to do statistical analyses. logP/P3 - log τ and logL - logτ have been plotted, here τ P/2P and L denote the characteristic time scale and the radio luminosity of pulsars respectively. The most striking feature is that after its initial dropping to a dip at about τ∼106 yrs, the radio luminosity of pulsar appears to grow up evidently and then redrop again. This feature is difficult to be understood in usual models. However, two tentative interpretations have been given in this paper.