학술논문
Using low-frequency scatter-broadening measurements for precision estimates of dispersion measures
Document Type
Working Paper
Author
Singha, Jaikhomba; Joshi, Bhal Chandra; Krishnakumar, M. A.; Kareem, Fazal; Bathula, Adarsh; Dwivedi, Churchil; Jacob, Shebin Jose; Desai, Shantanu; Tarafdar, Pratik; Arumugam, P.; Arumugam, Swetha; Bagchi, Manjari; Batra, Neelam Dhanda; Dandapat, Subhajit; Deb, Debabrata; Debnath, Jyotijwal; Gopakumar, A; Gupta, Yashwant; Hisano, Shinnosuke; Kato, Ryo; Kikunaga, Tomonosuke; Marmat, Piyush; Nobleson, K.; Paladi, Avinash K.; B., Arul Pandian; Prabu, Thiagaraj; Rana, Prerna; Srivastava, Aman; Surnis, Mayuresh; Susobhanan, Abhimanyu; Takahashi, Keitaro
Source
Subject
Language
Abstract
A pulsar's pulse profile gets broadened at low frequencies due to dispersion along the line of sight or due to multi-path 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 a new 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, $\alpha$, 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, for the first time, the measurements of the scatter-broadening time and $\alpha$ 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 $\alpha$ was different from that expected for Kolmogorov turbulence. Finally, we present the DM time-series after application of the new technique to PSR J1643$-$1224.
Comment: 9 pages, 8 figures, Submitted to MNRAS
Comment: 9 pages, 8 figures, Submitted to MNRAS