Title: Scintillation based search for off-pulse radio emission from pulsars,
Abstract: We propose a new method to detect off-pulse (unpulsed and/or continuous)
emission from pulsars, using the intensity modulations associated with
interstellar scintillation. Our technique involves obtaining the dynamic
spectra, separately for on-pulse window and off-pulse region, with time and
frequency resolutions to properly sample the intensity variations due to
diffractive scintillation, and then estimating their mutual correlation as a
measure of off-pulse emission, if any. We describe and illustrate the essential
details of this technique with the help of simulations, as well as real data.
We also discuss advantages of this method over earlier approaches to detect
off-pulse emission. In particular, we point out how certain non-idealities
inherent to measurement set-ups could potentially affect estimations in earlier
approaches, and argue that the present technique is immune to such
non-idealities. We verify both of the above situations with relevant
simulations. We apply this method to observation of PSR B0329+54 at frequencies
730 and 810 MHz, made with the Green Bank Telescope and present upper limits
for the off-pulse intensity at the two frequencies. We expect this technique to
pave way for extensive investigations of off-pulse emission with the help of
even existing dynamic spectral data on pulsars and of course with more
sensitive long-duration data from new observations.