Characterising Pulsars with Low-Frequency Software Telescopes
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2024-09-30Citation:
McKenna, David Joseph, Characterising Pulsars with Low-Frequency Software Telescopes, Trinity College Dublin, School of Physics, Physics, 2024Download Item:
Abstract:
Pulsars are a class of rapidly rotating neutron stars that periodically provide detectable emission in the direction of the Earth, where it can be detected by telescopes across the electromagnetic spectrum. These husks of former massive stars are extremely stable rotators, and some of the most extreme laboratories of the Universe. To date, pulsars have been used for a variety of research, ranging from characterising the interstellar medium, to detection of the first extra-solar planet, testing theories of general relativity and converting the Milky Way into a gravitational wave detector.
In this work, we discuss several projects that aimed to increase our understanding of recently discovered pulsars through the use of low-frequency software telescopes. This began with efforts to build up observing capabilities at the Irish station of the Low Frequency Array (LOFAR), simplifying telescope operations and producing software to perform data (pre)processing to convert the raw data produced by the telescope to science-ready or intermediate data products in both an on-line and off-line manner. Within this, we lay the
foundation for future work on the topic of pulsars, fast transients and general time-domain astronomy with the station.
We next discuss efforts using the Irish LOFAR station to perform a census of a class of pulsar known as rotating radio transients (RRATs), which are only detectable through isolated emission. During a 1900 h observing campaign with the telescope at 150 MHz, over 120 of these sources were observed, of which 29 were detected, 21 of which had not been discussed in prior work with LOFAR instruments. After initial detection, these sources were monitored to characterise their emission properties and perform pulsar timing to model the underlying rotation of the sources. Three sources had a sufficient event rates to allow for their rotation periods to be determined, while a total of 8 pulsar timing ephemerides were published based on the observations of this corpus of sources.
Exploratory work was performed on a smaller group of RRATs at three other sites. Five sources were observed at 1.25 GHz using the Five-hundred Aperture Spherical Telescope in China, detecting emission in 2 of 4 processed observations of these sources, which was also the first detection of both sources at this frequency. 27 sources were observed at 150 MHz using the LOFAR core, a dense set of LOFAR stations in the Netherlands, detecting emission from 14, 6 of which were novel to LOFAR, and determining a novel rotation period for 1 source, while refining 3 others. Finally, a census and monitoring campaign at 55 MHz using NenuFAR is discussed. Previously, only two RRATs had been detected below 100 MHz, but this work resulted in the detection of 8 sources with single-pulse emission (6 novel), and a further three with novel periodic emission for these frequencies, from the 22 observed sources. Three of the RRATs were followed-up with a dense observing campaign to characterise their emission.
At the Irish LOFAR station, a further two monitoring campaigns were performed on a set of 17 non-recycled pulsars to perform characterisation and timing, and beginning a long-term campaign to monitor the properties of single-pulses from the Crab pulsar. The pulsar monitoring campaign characterised the low-frequency emission from all 17 sources, and resulted in novel pulsar timing ephemerides for 12 sources. While the Crab monitoring campaign is expected to continue for several years, initial analysis and discussion of the properties from the observed emission between March 2020 and July 2023 are provided. This work closes with discussion arising from collaborations and other minor projects undertaken with the station, highlighting the diversity of observations that the 14 (and soon to be 16) international LOFAR stations currently spread across Europe can undertake.
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Irish Research Council (IRC)
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https://tcdlocalportal.tcd.ie/pls/EnterApex/f?p=800:71:0::::P71_USERNAME:MCKENND2Description:
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Author: McKenna, David Joseph
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Irish Research Council (IRC)Advisor:
Gallagher, PeterPublisher:
Trinity College Dublin. School of Physics. Discipline of PhysicsType of material:
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