Low-frequency pulse profile variation in PSR B2217+47: evidence for echoes from the interstellar medium

Abstract

We have observed a complex and continuous change in the integrated pulse profile of PSR B2217+47, manifested as additional components trailing the main peak. These transient components are detected over 6 yr at 150 MHz using the LOw Frequency ARray (LOFAR), but they are not seen in contemporaneous Lovell observations at 1.5 GHz. We argue that propagation effects in the ionized interstellar medium (IISM) are the most likely cause. The putative structures in the IISM causing the profile variation are roughly half-way between the pulsar and the Earth and have transverse radii R ∼ 30 au. We consider different models for the structures. Under the assumption of spherical symmetry, their implied average electron density is n¯¯¯e∼100 cm−3. Since PSR B2217+47 is more than an order of magnitude brighter than the average pulsar population visible to LOFAR, similar profile variations would not have been identified in most pulsars, suggesting that subtle profile variations in low-frequency profiles might be more common than we have observed to date. Systematic studies of these variations at low frequencies can provide a new tool to investigate the proprieties of the IISM and the limits to the precision of pulsar timing.

Publisher

Oxford University Press

Publication Date

2-13-2018

Publication Title

Monthly Notices of the Royal Astronomical Society

Department

Physics and Astronomy

Document Type

Article

DOI

https://dx.doi.org/10.1093/mnras/sty368

Keywords

Pulsars: individual: PSR B2217+47, ISM: general, radio continuum: ISM

Language

English

Format

text

Link to Full Text

Share

COinS