Observations of Low-frequency Radio Emission from Millisecond Pulsars and Multipath Propagation in the Interstellar Medium
Journal article, 2018
Studying the gravitational-wave sky with pulsar timing arrays (PTAs) is a key science goal for the Square Kilometre Array (SKA) and its pathfinder telescopes. With current PTAs reaching sub-microsecond timing precision, making accurate measurements of interstellar propagation effects and mitigating them effectively has become increasingly important to realize PTA goals. As these effects are much stronger at longer wavelengths, low-frequency observations are most appealing for characterizing the interstellar medium (ISM) along the sight lines toward PTA pulsars. The Murchison Widefield Array (MWA) and the Engineering Development Array (EDA), which utilizes MWA technologies, present promising opportunities for undertaking such studies, particularly for PTA pulsars located in the southern sky. Such pulsars are also the prime targets for PTA efforts planned with the South African MeerKAT, and eventually with the SKA. In this paper we report on observations of two bright southern millisecond pulsars, PSR J0437-4715 and PSR J2145-0750, made with these facilities; MWA observations sampled multiple frequencies across the 80-250 MHz frequency range, while the EDA provided direct-sampled baseband data to yield a large instantaneous usable bandwidth of similar to 200 MHz. Using these exploratory observations, we investigate various aspects relating to pulsar emission and ISM properties, such as spectral evolution of the mean pulse shape, scintillation as a function of frequency, chromaticity in interstellar dispersion, and flux density spectra at low frequencies. Systematic and regular monitoring observations will help ascertain the role of low-frequency measurements in PTA experiments, while simultaneously providing a detailed characterization of the ISM toward the pulsars, which will be useful in devising optimal observing strategies for future PTA experiments.
instrumentation: interferometers
ISM: general
pulsars: general
methods: observational
pulsars: individual (PSR J0437-4715, PSR J2145-0750)
Author
N. D. R. Bhat
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Curtin University
S. E. Tremblay
Curtin University
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Franz Kirsten
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
B. W. Meyers
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Curtin University
M. Sokolowski
Curtin University
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
W. van Straten
Auckland University of Technology
S. J. McSweeney
Curtin University
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
S. M. Ord
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
R. M. Shannon
ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)
Curtin University
Swinburne University of Technology
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
A. Beardsley
Arizona State University
B. Crosse
Curtin University
D. Emrich
Curtin University
T. M. O. Franzen
Curtin University
L. Horsley
Curtin University
M. Johnston-Hollitt
Curtin University
D. L. Kaplan
University of Wisconsin Madison
D. Kenney
Curtin University
M. F. Morales
University of Washington
D. Pallot
University of Western Australia
K. Steele
Curtin University
S. J. Tingay
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Curtin University
C. M. Trott
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Curtin University
M. Walker
Curtin University
R. B. Wayth
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Curtin University
A. Williams
Curtin University
C. Wu
University of Western Australia
Astrophysical Journal, Supplement Series
0067-0049 (ISSN) 1538-4365 (eISSN)
Vol. 238 1 1Subject Categories
Medical Laboratory and Measurements Technologies
Astronomy, Astrophysics and Cosmology
Fusion, Plasma and Space Physics
DOI
10.3847/1538-4365/aad37c