ترغب بنشر مسار تعليمي؟ اضغط هنا

Luminosity of radio pulsar and its new emission death line

106   0   0.0 ( 0 )
 نشر من قبل QingDong Wu
 تاريخ النشر 2020
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We investigated the pulsar radio luminosity ($L$), emission efficiency (ratio of radio luminosity to its spin-down power $dot{E}$), and death line in the diagram of magnetic field (B) versus spin period (P), and found that the dependence of pulsar radio luminosity on its spin-down power ($L-dot{E}$) is very weak, shown as $Lsimdot{E}^{0.06}$, which deduces an equivalent inverse correlation between emission efficiency and spin-down power as $xisim dot{E}^{-0.94}$. Furthermore, we examined the distributions of radio luminosity of millisecond and normal pulsars, and found that, for the similar spin-down powers, the radio luminosity of millisecond pulsars is about one order of magnitude lower than that of the normal pulsars. The analysis of pulsar radio flux suggests that this correlations are not due to a selective effect, but are intrinsic to the pulsar radio emission physics. Their radio radiations may be dominated by the different radiation mechanisms. The cut-off phenomenon of currently observed radio pulsars in B-P diagram is usually referred as the pulsar death line, which corresponds to $dot{E}approx 10^{30}$ erg/s and is obtained by the cut-off voltage of electron acceleration gap in the polar cap model of pulsar proposed by Ruderman and Sutherland. Observationally, this death line can be inferred by the actual observed pulsar flux $Sapprox $1mJy and 1kpc distance, together with the maximum radio emission efficiency of 1%. At present, the actual observed pulsar flux can reach 0.01mJy by FAST telescope, which will arise the observational limit of spin-down power of pulsar as low as $dot{E}approx 10^28$ erg/s. This means that the new death line is downward shifted two orders of magnitude, which might be favorably referred as the observational limit-line, and accordingly the pulsar theoretical model for the cut-off voltage of gap should be heavily modified.



قيم البحث

اقرأ أيضاً

Since pulsars were discovered as emitters of bright coherent radio emission more than half a century ago, the cause of the emission has remained a mystery. In this Letter we demonstrate that coherent radiation can be directly generated in non-station ary pair plasma discharges which are responsible for filling the pulsar magnetosphere with plasma. By means of large-scale two-dimensional kinetic plasma simulations, we show that if pair creation is non-uniform across magnetic field lines, the screening of electric field by freshly produced pair plasma is accompanied by the emission of waves which are electromagnetic in nature. Using localized simulations of the screening process, we identify these waves as superluminal ordinary (O) modes, which should freely escape from the magnetosphere as the plasma density drops along the wave path. The spectrum of the waves is broadband and the frequency range is comparable to that of observed pulsar radio emission.
76 - Bing Zhang 2000
We reinvestigate the radio pulsar ``death lines within the framework of two different types of polar cap acceleration models, i.e., the vacuum gap model and the space-charge-limited flow model, with either curvature radiation or inverse Compton scatt ering photons as the source of pairs. General relativistic frame-dragging is taken into account in both models. We find that the inverse Compton scattering induced space-charge-limited flow model can sustain strong pair production in some long-period pulsars, which allows the newly detected 8.5s pulsar PSR J2144-3933 to be radio loud, without assuming a special neutron star equation-of-state or ad hoc magnetic field configurations.
It is shown that pulsar radio emission can be generated effectively through a streaming motion in the polar-cap regions of a pulsar magnetosphere causing nonresonant growth of waves that can escape directly. As in other beam models, a relatively low- energy high-density beam is required. The instability generates quasi-transverse waves in a beam mode at frequencies that can be well below the resonant frequency. As the waves propagate outward growth continues until the height at which the wave frequency is equal to the resonant frequency. Beyond this point the waves escape in a natural plasma mode (L-O mode). This one-step mechanism is much more efficient than previously widely considered multi-step mechanisms.
The computational cost of searching for new pulsars is a limiting factor for upcoming radio telescopes such as SKA. We introduce four new algorithms: an optimal constant-period search, a coherent tree search which permits optimal searching with O(1) cost per model, a semicoherent search which combines information from coherent subsearches while preserving as much phase information as possible, and a hierarchical search which interpolates between the coherent and semicoherent limits. Taken together, these algorithms improve the computational cost of pulsar search by several orders of magnitude. In this paper, we consider the simple case of a constant-acceleration phase model, but our methods should generalize to more complex search spaces.
121 - J. A. Eilek , T. H. Hankins 2016
We review our high-time-resolution radio observations of the Crab pulsar and compare our data to a variety of models for the emission physics. The Main Pulse and the Low-Frequency Interpulse come from regions somewhere in the high-altitude emission z ones (caustics) that also produce pulsed X-ray and gamma-ray emission. Although no emission model can fully explain these two components, the most likely models suggest they arise from a combination of beam-driven instabilities, coherent charge bunching and strong electromagnetic turbulence. Because the radio power fluctuates on a wide range of timescales, we know the emission zones are patchy and dynamic. It is tempting to invoke unsteady pair creation in high-altitude gaps as source of the variability, but current pair cascade models cannot explain the densities required by any of the likely models. It is harder to account for the mysterious High-Frequency Interpulse. We understand neither its origin within the magnetosphere nor the striking emission bands in its dynamic spectrum. The most promising models are based on analogies with solar zebra bands, but they require unusual plasma structures which are not part of our standard picture of the magnetosphere. We argue that radio observations can reveal much about the upper magnetosphere, but work is required before the models can address all of the data.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا