Topology and Polarisation of Subbeams Associated With Pulsar B0943+10's `Drifting'-Subpulse Emission: II. Analysis of Gauribidanur 35-MHz Observations

In the previous paper of this series Deshpande & Rankin (2001) reported results regarding subpulse-drift phenomenon in pulsar B0943+10 at 430 MHz and 111 MHz. This study has led to the identification of a stable system of subbeams circulating around the magnetic axis of this star. Here, we present a single-pulse analysis of our observations of this pulsar at 35 MHz. The fluctuation properties seen at this low frequency, as well as our independent estimates of the number of subbeams required and their circulation time, agree remarkably well with the reported behavior at higher frequencies. We use the `cartographic'-transform mapping technique developed in Paper-I to study the emission pattern in the polar region of this pulsar. The significance of our results in the context of radio emission mechanisms is also discussed.Comment: 6 pages, 7 figures (2 color figs), MNRAS, 326 (4), 1249-1254 (2001

Fluctuation Properties and Polar Emission Mapping of Pulsar B0834+06 at Decameter Wavelengths

Recent results regarding subpulse-drift in pulsar B0943+10 have led to the identification of a stable system of sub-beams circulating around the magnetic axis of the star. Here, we present single-pulse analysis of pulsar B0834+06 at 35 MHz, using observations from the Gauribidanur Radio Telescope. Certain signatures in the fluctuation spectra and correlations allow estimation of the circulation time and drift direction of the underlying emission pattern responsible for the observed modulation. We use the `cartographic transform' mapping technique to study the properties of the polar emission pattern. These properties are compared with those for the other known case of B0943+10, and the implications are discussed.Comment: (v3: minor changes); 9 pages, 6 figures (11 ps files); To appear in MNRA

Using R-based VOStat as a low resolution spectrum analysis tool

We describe here an online software suite VOStat written mainly for the Virtual Observatory, a novel structure in which astronomers share terabyte scale data. Written mostly in the public-domain statistical computing language and environment R, it can do a variety of statistical analysis on multidimensional, multi-epoch data with errors. Included are techniques which allow astronomers to start with multi-color data in the form of low-resolution spectra and select special kinds of sources in a variety of ways including color outliers. Here we describe the tool and demonstrate it with an example from Palomar-QUEST, a synoptic sky survey