Frequency dependence of pulsar radiation patterns

We report on new results from simultaneous, dual frequency, single pulse observation of PSR B0329+54 using the Giant Metrewave Radio Telescope. We find that the longitude separation of subpulses at two different frequencies (238 and 612 MHz) is less than that for the corresponding components in the average profile. A similar behaviour has been noticed before in a number of pulsars. We argue that subpulses are emitted within narrow flux tubes of the dipolar field lines and that the mean pulsar beam has a conal structure. In such a model the longitudes of profile components are determined by the intersection of the line of sight trajectory with subpulse-associated emission beams. Thus, we show that the difference in the frequency dependence of subpulse and profile component longitudes is a natural property of the conal model of pulsar emission beam. We support our conclusions by numerical modelling of pulsar emission, using the known parameters for this pulsar, which produce results that agree very well with our dual frequency observations.Comment: 24 pages, 8 figures. Accepted for publication in Ap

Pulsar spectra of radio emission

We have collected pulsar flux density observations and compiled spectra of 281 objects. The database of Lorimer et al. (\cite{lorimer}) has been extended to frequencies higher than 1.4 GHz and lower than 300 MHz. Our results show that above 100 MHz the spectra of the majority of pulsars can be described by a simple power law with average value of spectral index $= -1.8\pm0.2$. A rigorous analysis of spectral fitting revealed only about 5% of spectra which can be modelled by the two power law. Thus, it seems that single power law is a rule and the two power law spectrum is a rather rare exception, of an unknown origin, to this rule. We have recognized a small number of pulsars with almost flat spectrum ($\alpha \geq -1.0$) in the wide frequency range (from 300 MHz to 20 GHz) as well as few pulsars with a turn-over at unusually high frequency ($\sim$~1 GHz).Comment: 9 pages, 3 figure

Upper Limits on the Pulsed Radio Emission from the Geminga Pulsar at 35 & 327 MHz

We report here our observations at 35 MHz and 327 MHz made in the direction of the Gamma Ray pulsar Geminga. Based on the observed absence of any significant pulsed emission from this source above our detection thresholds at the two frequencies, we obtain useful upper-limits for the average flux to be 75-100 mJy at 35 MHz, and 0.2-0.3 mJy at 327 MHz. We discuss a few possible reasons for the ``radio-quiet'' nature of this pulsar at frequencies other than around 100 MHz.Comment: Accepted for publication in Astronomy & Astrophysic

On the pulse-width statistics in radio pulsars

The Monte Carlo simulations of pulsar periods, pulse-widths and magnetic inclination angles are performed. Using the available observational data sets we study a possible trial parent distribution functions by means of the Kolmogorov-Smirnov significance tests. We also use an additional condition that the numbers of generated interpulses, whether from both magnetic poles or from single pole, are at the observed levels. We conclude that the parent distribution function of magnetic inclination angles is neither flat nor cosine but it is a more complicated function with a local maximum near alpha=25deg and another weaker one near alpha=90deg. The plausible distribution function of pulsar periods is represented by the gamma function. The beaming fraction describing the fraction of observable radio pulsars is about 0.12.Comment: Astronomy & Astrophysics in pres

Una reflexión crítica sobre el Mecanismo de Antikythera desde una perspectiva idealista y sus implicaciones en el desarrollo tecnológico como medio para entender nuestro Cosmos

Technology can be an insight into how humanities’ needs have changed along the centuries and how science has been applied in order to solve these conundrums, to make the world our own and understand it to learn about what surrounds, what is true, and what is unchangeable. The Antikythera Mechanism’s complexity and recent discoveries allow the academy to know its functions and how exact it was, as a new model has been proposed that shows that it was a device to unravel one of the biggest mysteries of antiquity: The Cosmos and the Stars. Along with the help of the perspective of Collingwood’s sense II and sense III, this paper aims to define and analyse the epistemological and methodological significance of the Antikythera Mechanism, by looking into what is says about the old world and how it contrasts with the new.La tecnología muestra una mirada perspicaz hacia cómo las necesidades de la humanidad han cambiado a lo largo de los siglos, y cómo la ciencia ha sido aplicada para resolver estos acertijos, para hacer el mundo nuestro y entenderlo para aprender lo que rodea, lo que es cierto y lo que es inmutable. La complejidad del mecanismo de Antikythera y recientes descubrimientos permiten a la academia saber sus funciones y qué tan exacto era, ya que un nuevo modelo ha sido propuesto que muestra que era un dispositivo para descifrar uno de los más grandes misterios de la antigüedad: El cosmos y las estrellas.Con la ayuda de la perspectiva del sentido II y el sentido III de Collingwood, este artículo busca definir y analizar el significado epistemológico y metodológico del mecanismo de Antikythera, al estudiar lo que dice del viejo mundo y cómo contrasta con el nuevo