27 research outputs found
Evidence for profile changes in PSR J1713+0747 using the uGMRT
PSR J1713+0747 is one of the most precisely timed pulsars in the international pulsar timing array experiment. This pulsar showed an abrupt profile shape change between 2021 April 16, (MJD 59320) and 2021 April 17 (MJD 59321). In this paper, we report the results from multi-frequency observations of this pulsar carried out with the upgraded Giant Metrewave Radio Telescope (uGMRT) before and after the event. We demonstrate the profile change seen in Band 5 (1260 MHz-1460 MHz) and Band 3 (300 MHz-500 MHz). The timing analysis of this pulsar shows a disturbance accompanying this profile change followed by a recovery with a time-scale of ∼159 days. Our data suggest that a model with chromatic index as a free parameter is preferred over models with combinations of achromaticity with DM bump or scattering bump. We determine the frequency dependence to be ∼ν+1.34. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Noise analysis of the Indian Pulsar Timing Array data release I
The Indian Pulsar Timing Array (InPTA) collaboration has recently made its first official data release (DR1) for a sample of 14 pulsars using 3.5 years of uGMRT observations. We present the results of single-pulsar noise analysis for each of these 14 pulsars using the InPTA DR1. For this purpose, we consider white noise, achromatic red noise, dispersion measure (DM) variations, and scattering variations in our analysis. We apply Bayesian model selection to obtain the preferred noise models among these for each pulsar. For PSR J1600−3053, we find no evidence of DM and scattering variations, while for PSR J1909−3744, we find no significant scattering variations. Properties vary dramatically among pulsars. For example, we find a strong chromatic noise with chromatic index ∼ 2.9 for PSR J1939+2134, indicating the possibility of a scattering index that doesn’t agree with that expected for a Kolmogorov scattering medium consistent with similar results for millisecond pulsars in past studies. Despite the relatively short time baseline, the noise models broadly agree with the other PTAs and provide, at the same time, well-constrained DM and scattering variations
MeerTRAP: Twelve Galactic fast transients detected in a real-time, commensal MeerKAT survey
MeerTRAP is a real-time untargeted search project using the MeerKAT telescope
to find single pulses from fast radio transients and pulsars. It is performed
commensally with the MeerKAT large survey projects (LSPs), using data from up
to 64 of MeerKAT's 13.96~m dishes to form hundreds of coherent beams on sky,
each of which is processed in real time to search for millisecond-duration
pulses. We present the first twelve Galactic sources discovered by MeerTRAP,
with DMs in the range of 33--381~pc~cm. One source may be Galactic or
extragalactic depending on the Galactic electron density model assumed.
Follow-up observations performed with the MeerKAT, Lovell, and Parkes radio
telescopes have detected repeat pulses from seven of the twelve sources. Pulse
periods have been determined for four sources. Another four sources could be
localised to the arcsecond-level using a novel implementation of the tied-array
beam localisation method.Comment: 16 pages, 14 figure
FRB 20210405I: a nearby Fast Radio Burst localised to sub-arcsecond precision with MeerKAT
We present the first sub-arcsecond localised Fast Radio Burst (FRB) detected
using MeerKAT. FRB 20210405I was detected in the incoherent beam using the
MeerTRAP pipeline on 2021 April 05 with a signal to noise ratio of 140.8 and a
dispersion measure of 565.17 pc cm. It was detected while MeerTRAP was
observing commensally with the ThunderKAT large survey project, and was
sufficiently bright that we could use the ThunderKAT 8s images to localise the
FRB. Two different models of the dispersion measure in the Milky Way and halo
suggest that the source is either right at the edge of the Galaxy, or outside.
This highlights the uncertainty in the Milky Way dispersion measure models,
particularly in the Galactic Plane, and the uncertainty of Milky Way halo
models. Further investigation and modelling of these uncertainties will be
facilitated by future detections and localisations of nearby FRBs. We use the
combined localisation, dispersion measure, scattering, specific luminosity and
chance coincidence probability information to find that the origin is most
likely extra-galactic and identify the likely host galaxy of the FRB: 2MASS
J17012494932475. Using SALT spectroscopy and archival observations of the
field, we find that the host is a disk/spiral galaxy at a redshift of
.Comment: 15 pages, 4 tables, 10 figures. Accepted to MNRA