Polarization observations of giant radio pulses from the millisecond pulsar B1937+21 at a frequency of 600 MHz

We performed polarization observations of giant radio pulses from the millisecond pulsar B1937+21. The observations were carried out in July 2002 with the 64-m Kalyazin radio telescope at a frequency of 600 MHz in two polarization channels with left-and right-hand circular polarizations (RCP and LCP). We used the S2 data acquisition system with a time resolution of 125 ns. The duration of an observing session was 20 min. We detected twelve giant radio pulses with peak flux densities higher than 1000 Jy; five and seven of these pulses appeared in the RCP and LCP channels, respectively. We found no event that exceeded the established detection threshold simultaneously in the two polarization channels. Thus, we may conclude that the detected giant pulses have a high degree of circular polarization, with the frequency of occurrence of RCP and LCP pulses being the same.     

Massless scalar field in Robertson-Walker space-time

Recently, exact spatially-homogeneous solutions have been found for a conformally invariant massless scalar fieldS(t) coupled to a Robertson-Walker geometry. We investigate extending these solutions to inhomogeneous scalar fieldsS(t, x ^l ). For an isotropic scalar fieldS(t, r) we find a solution satisfying three of the five field equations. If we use REDUCE, we show that the remaining equations forceS=S(t).     

Line forming regions in active galaxies and their nuclei

The spectra of active galaxies and their nuclei are rich in emission and absorption line features. A major aim of present research is the development of self-consistent hydrodynamic models for the production of the line-forming regions. We here review such modelling and stress the central role played by shock phenomena induced by winds and explosions on scales ranging from the circumstellar to the intergalactic.     

Results from the Whole Earth Telescope — Indian contributions

The Indian team at ISRO has been part of the Whole Earth Telescope (WET) team since 1988 when we first participated in the campaign on V471 Tau. We have been part of many other observing campaigns over the last decade. This presentation traces the circumstances leading to our joining the WET team and how useful the coverage from the Indian longitude has been. The results of several pulsators from the WET runs during which we participated are also described. These include PG1159-035 the prototype of the GW Vir type of stars, RE J 0751+14 a cataclysmic variable, PG 1336-018 a binary with an sdB pulsator and finally HR 1217 a roAp star. The paper concludes with what the limitations are in our observations and how we can overcome them in the future.     

Modeling X-Ray Photoionized Plasmas Produced at the Sandia Z-Facility

In experiments at the high-power Z-facility at Sandia National Laboratory in Albuquerque, New Mexico, we have been able to produce a low density photoionized laboratory plasma of Fe mixed with NaF. The conditions in the experiment allow a meaningful comparison with X-ray emission from astrophysical sources. The charge state distributions of Fe, Na and F are determined in this plasma using high resolution X-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter ξ = 20–25 erg cm s⁻¹ under nearly steady-state conditions. First comparisons of the measured charge state distributions with X-ray photoionization models show reasonable agreement, although many questions remain.