The frequency evolution of interstellar pulse broadeningfrom radio pulsars

• Published in: Astronomy and astrophysics (Berlin) 2004-10, Vol.425 (2), p.569-575
• Main Authors: Löhmer, O., Mitra, D., Gupta, Y., Kramer, M., Ahuja, A.
• Format: Article
• Language: English
• Subjects: ISM: structure; scattering; stars: pulsars: general; stars: pulsars: individual: PSR B1933+16
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20035881

In this paper we report multi-frequency measurements of pulse broadening times ($\tau_{\rm d}$) for nine medium dispersion measure (DM $\approx 150{-}400$ pc cm-3) pulsars observed over a wide frequency range. The low frequency data at 243, 325 and 610 MHz are new observations done with the Giant Metrewave Radio Telescope (GMRT). The frequency dependence of $\tau_{\rm d}$ for all but one (PSR B1933+16) of our sources is consistent with the Kolmogorov spectrum of electron density fluctuations in a turbulent medium. PSR B1933+16, however, shows a very flat spectrum as previously observed for high DM pulsars. Our observations combined with earlier published results enable us to study the spectral index of $\tau_{\rm d}$ over the whole observed DM range. While the spectral properties are generally consistent with a Kolmogorov spectrum, pulsars seen along line-of-sights towards the inner Galaxy or complex regions often show deviations from this expected behaviour.