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A Study of Scattering in Pulsars below 100 MHz

Thursday October 4, 2018
2:00 pm

 Presenter:  Karishma Bansal (UNM)
 Series:  Center for Astrophysics Research and Technologies Seminar Series
 Abstract:  The interstellar medium (ISM) consists of an ionized plasma which affects radiation as it traverses the medium. Observable ISM effects include dispersion, scattering, angular broadening, and interstellar scintillation. Pulsars are compact and emit short pulses thus making them good candidates to study and understand all the above effects. Furthermore, all of these effects are stronger at lower frequencies, though in the case of scattering the pulsar profiles also grow asymmetrically broader at lower frequencies which can complicate the analysis. Different ISM models predict different frequency dependencies for the scattering time-scale τsc. For gaussian inhomogeneity, the scaling relation for τsc goes as the fourth power of frequency, while for a Kolmogorov distribution of irregularities, the expected relation for τsc is with frequency to the 4.4. Previous scattering studies show a wide range of scattering index across all ranges of DM. A scattering index less than 4 is believed to be due to either limitations of the underlying assumptions of the thin screen model or an anisotropic scattering mechanism. The effect of this anisotropy can be seen in the power spectra as scintillation arcs. However, identifying such features has been difficult at low frequencies.
 Host:  Gregory Taylor
 Location:  Room 190, Physics & Astronomy

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