Aris Karastergiou

Abstract:

<jats:title>Abstract</jats:title> <jats:p>We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for the newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. MeerKAT is a high-gain (<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S1323358020000193_inline1.png" /> <jats:tex-math> ${\sim}2.8\,\mbox{K Jy}^{-1}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>) low-system temperature (<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S1323358020000193_inline2.png" /> <jats:tex-math> ${\sim}18\,\mbox{K at }20\,\mbox{cm}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>) radio array that currently operates at 580–1 670 MHz and can produce tied-array beams suitable for pulsar observations. This paper presents results from the MeerTime Large Survey Project and commissioning tests with PTUSE. Highlights include observations of the double pulsar <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S1323358020000193_inline3.png" /> <jats:tex-math> $\mbox{J}0737{-}3039\mbox{A}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, pulse profiles from 34 millisecond pulsars (MSPs) from a single 2.5-h observation of the Globular cluster Terzan 5, the rotation measure of Ter5O, a 420-sigma giant pulse from the Large Magellanic Cloud pulsar PSR <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S1323358020000193_inline4.png" /> <jats:tex-math> $\mbox{J}0540{-}6919$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, and nulling identified in the slow pulsar PSR J0633–2015. One of the key design specifications for MeerKAT was absolute timing errors of less than 5 ns using their novel precise time system. Our timing of two bright MSPs confirm that MeerKAT delivers exceptional timing. PSR <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S1323358020000193_inline5.png" /> <jats:tex-math> $\mbox{J}2241{-}5236$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> exhibits a jitter limit of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S1323358020000193_inline6.png" /> <jats:tex-math> $&lt;4\,\mbox{ns h}^{-1}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> whilst timing of PSR <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S1323358020000193_inline7.png" /> <jats:tex-math> $\mbox{J}1909{-}3744$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> over almost 11 months yields an rms residual of 66 ns with only 4 min integrations. Our results confirm that the MeerKAT is an exceptional pulsar telescope. The array can be split into four separate sub-arrays to time over 1 000 pulsars per day and the future deployment of S-band (1 750–3 500 MHz) receivers will further enhance its capabilities.</jats:p>

Abstract:

We present the data analysis pipeline, commissioning observations, and initial results from the GREENBURST fast radio burst (FRB) detection system on the Robert C. Byrd Green Bank Telescope (GBT) previously described by Surnis et al., which uses the 21-cm receiver observing commensally with other projects. The pipeline makes use of a state-of-the-art deep learning classifier to winnow down the very large number of false-positive single-pulse candidates that mostly result from radio frequency interference. In our observations, totalling 156.5 d so far, we have detected individual pulses from 20 known radio pulsars that provide an excellent verification of the system performance. We also demonstrate, through blind injection analyses, that our pipeline is complete down to a signal-to-noise threshold of 12. Depending on the observing mode, this translates into peak flux sensitivities in the range 0.14–0.89 Jy. Although no FRBs have been detected to date, we have used our results to update the analysis of Lawrence et al. to constrain the FRB all-sky rate to be 1150+200−180 per day above a peak flux density of 1 Jy. We also constrain the source count index α = 0.84 ± 0.06, which indicates that the source count distribution is substantially flatter than expected from a Euclidean distribution of standard candles (where α = 1.5). We discuss this result in the context of the FRB redshift and luminosity distributions. Finally, we make predictions for detection rates with GREENBURST, as well as other ongoing and planned FRB experiments.

Abstract:

Pulsar radio emission and its polarization are observed to evolvewith frequency. This frequency dependence is key to the emission mechanism and the structure of the radio beam.With the new ultra-wideband receiver (UWL) on the Parkes radio telescope we are able, for the first time, to observe how pulsar profiles evolve over a broad continuous bandwidth of 700-4000 MHz.We describe here a technique for processing broad-band polarimetric observations to establish a meaningful alignment and visualize the data across the band.We apply this to observations of PSRs J1056-6258 and J1359-6038, chosen due to previously unresolved questions about the frequency evolution of their emission. Application of our technique reveals that it is possible to align the polarization position angle (PA) across a broad frequency range when constrained to applying only corrections for dispersion and Faraday rotation to do so. However, this does not correspond to aligned intensity profiles for these two sources. We find that it is possible to convert these misalignments into emission height range estimates that are consistent with published and simulated values, suggesting that they can be attributed to relativistic effects in the magnetosphere. We discuss this work in the context of the radio beam structure and prepare the ground for a wider study of pulsar emission using broad-band polarimetric data.