Singha, J and Joshi, BC and Krishnakumar, MA and Kareem, F and Bathula, A and Dwivedi, C and Jacob, SJ and Desai, S and Tarafdar, P and Arumugam, P and Arumugam, S and Bagchi, M and Batra, ND and Dandapat, S and Deb, D and Debnath, J and Gopakumar, A and Gupta, Y and Hisano, S and Kato, R and Kikunaga, T and Marmat, P and Nobleson, K and Paladi, AK and Arul Pandian, B and Prabu, T and Rana, P and Srivastava, A and Surnis, M and Susobhanan, A and Takahashi, K (2024) Improving DM estimates using low-frequency scatter-broadening estimates. In: Monthly Notices of the Royal Astronomical Society, 535 (1). pp. 1184-1192.
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Abstract
A pulsar�s pulse profile gets broadened at low frequencies due to dispersion along the line of sight or due to multipath propagation. The dynamic nature of the interstellar medium makes both of these effects time-dependent and introduces slowly varying time delays in the measured times-of-arrival similar to those introduced by passing gravitational waves. In this article, we present an improved method to correct for such delays by obtaining unbiased dispersion measure (DM) measurements by using low-frequency estimates of the scattering parameters. We evaluate this method by comparing the obtained DM estimates with those, where scatter-broadening is ignored using simulated data. A bias is seen in the estimated DMs for simulated data with pulse-broadening with a larger variability for a data set with a variable frequency scaling index, α, as compared to that assuming a Kolmogorov turbulence. Application of the proposed method removes this bias robustly for data with band averaged signal-to-noise ratio larger than 100. We report the measurements of the scatter-broadening time and α from analysis of PSR J1643�1224, observed with upgraded Giant Metrewave Radio Telescope as part of the Indian Pulsar Timing Array experiment. These scattering parameters were found to vary with epoch and α was different from that expected for Kolmogorov turbulence. Finally, we present the DM time-series after application of this technique to PSR J1643�1224. © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.
| Item Type: | Journal Article |
|---|---|
| Publication: | Monthly Notices of the Royal Astronomical Society |
| Publisher: | Oxford University Press |
| Additional Information: | The copyright for this article belongs to the author. |
| Keywords: | Frequency estimation; Multipath propagation; Time of arrival; Time series; Velocity measurement, Dispersion measure; Frequency scatter; ISM:general; Kolmogorov turbulence; Line of Sight; Lower frequencies; Pulsar: individual (PSR j1643�1224); Pulsars: general; Pulsars:individual; Pulse profile, Pulsars |
| Department/Centre: | Division of Physical & Mathematical Sciences > Joint Astronomy Programme |
| Date Deposited: | 29 Nov 2024 09:13 |
| Last Modified: | 29 Nov 2024 09:13 |
| URI: | http://eprints.iisc.ac.in/id/eprint/86945 |
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