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21-08-2018
Scintillation based search for off-pulse emission from pulsars
| Submitter: | Iuliana Nitu |
| Description: | An ongoing question in pulsar emission is whether pulsars have some intrinsic 'off-pulse' emission, outside their main pulse region. While any such off-pulse emission would be too faint to detect directly, the ISM can help by acting as a lens. In the right conditions, the signal from a pulsar could show scintillation, or intensity fluctuations, due to the irregularities in the ISM as it propagates through. If the pulsar's magnetosphere is not resolved, and thus the pulsar looks like a point source, the off-pulse emission should show correlated intensity variations to the ones of the main-pulse. On the basis of this, we used a new technique ( Ravi and Deshpande 2018 ) to estimate off-pulse emission from pulsars. A major part of this project was the implementation of this technique in Python. Then, we analysed various observations. The image here shows the main plots of the analysis of PSR J1713+0747 data taken with the Green Bank Telescope, as part of the 24-hour campaign (with thanks to Joeri van Leeuwen and Timothy Dolch for providing these data). On the right, the dynamic spectrum of the main pulse region shows bright regions (or scintles) due to interstellar scintillation. On the top-left, the 2D auto-correlation of the main pulse dynamic spectrum is shown, with the corresponding 1D cuts at zero frequency and time lag respectively. The widths of the Gaussian distributions are representative of the dimensions of the scintles. On the bottom-left, the cross-correlation between the main pulse and the off-pulse dynamic spectra is shown, with the corresponding cuts. Our analysis places a limit on the off-pulse emission as (0.0 +/- 0.4)% of the main pulse emission. We hope that in the near future, the software developed this summer will lead to a systematic search of off-pulse emission in many pulsars, and eventually help improve our understanding of pulsar emission. |
| Copyright: | Iuliana Nitu |
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