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J. McCauley

Publications and source records attributed to J. McCauley.

5 recordsLinked to original sources

Pulsar timing solutions for 17 pulsars at 150 MHz from the Irish LOFAR station

Pulsar timing is a foundational part of pulsar research to triage the most interesting systems and to characterise properties (rotational or otherwise) of the population of these extreme objects. Due to the efficiency of a number of sensitive and/or wide-field surveys in recent years, the number of new pulsars discoveries is growing year-on-year, and most of these lack even basic timing parameter measurements. This work aims to demonstrate the capabilities of international Low Frequency Array (LOFAR) stations operating as single telescopes to follow-up, time and characterise these sources, offering new insight into the emission properties of these neutron stars, and support efforts to build timing models for these sources. Between 2020 and 2023 we used the local-mode allocation of the Irish LOFAR station to follow-up 33 pulsar candidates announced from various surveys at different observing frequencies to determine if an international LOFAR station has sufficient sensitivity to detect and time these sources. From the 33 pulsars selected, 22 pulsars were detected and 17 were selected for long-term monitoring across 590 hours of observing time. This has resulted in coherent timing solutions for all of these sources at 150 MHz -- 7 of these have never had any reported timing solutions, the remaining 10 solutions agree well with announcements from others since the beginning of our project. For a fraction of sources announced by surveys each year, the 14 international LOFAR stations are well placed to follow-up survey candidates for long-term pulsar monitoring beyond the standard timing campaigns performed at these telescopes to date, reducing the pressure on observing time availability at these observatories, and enabling the full scientific potential of these pulsars to be realised.

astro-ph.HE

GReX: An Instrument Overview and New Upper Limits on the Galactic FRB Population

We present the instrument design and initial results for the Galactic Radio Explorer (GReX), an all-sky monitor for exceptionally bright transients in the radio sky. This instrument builds on the success of STARE2 to search for fast radio bursts (FRBs) from the Milky Way and its satellites. This instrument has deployments across the globe, with wide sky coverage and searching down to $32\,\mu\text{s}$ time resolution, enabling the discovery of new super giant pulses. Presented here are the details of the hardware and software design of the instrument, performance in sensitivity and other key metrics, and experience in building a global-scale, low-cost experiment. We follow this discussion with experimental results on validation of the sensitivity via hydrogen-line measurements. We then update the rate of Galactic FRBs based on non-detection in the time since FRB 200428. Our results suggest FRB-like events are even rarer than initially implied by the detection of a MJy burst from SGR J1935+2154 in April 2020.

astro-ph.HE

A Census of Rotating Radio Transients at 150 MHz with the Irish LOFAR Station

Rotating radio transients (RRATs) are neutron stars that emit detectable radio bursts sporadically. They are statistically distinct in the neutron star population, in many observable properties, but by their nature are practically difficult to study in depth. In this paper, we present the results from 1408 h of observations of RRAT candidates using the Irish station of the Low Frequency Array (LOFAR) at 150 MHz. As of October 2022, this census involved observing 113 sources, leading to 29 detections which were then followed up systematically. Single-pulse emission was detected from 25 sources, and periodic emission from 14 sources. 18 sources were found to have emission behaviour that is not discussed in prior works using LOFAR instruments. Four novel or modified source periods have been determined, ranging from 1.5-3.9 s, and 8 new or updated phase-coherent pulsar timing ephemerides have been produced using detected bursts. One unexpected single-pulse with a clearly-Galactic dispersion measure was detected as a part of this work, but has not been re-detected in follow-up observations. Observations are ongoing to expand the number of observed sources and further characterise and improve ephemerides for the detected sources. This census has demonstrated the capability for international LOFAR stations to detect, monitor and characterise a significant fraction of these unique sources.

astro-ph.HE

First Results from the REAL-time Transient Acquisition backend (REALTA) at the Irish LOFAR station

Modern radio interferometers such as the LOw Frequency ARray (LOFAR) are capable of producing data at hundreds of gigabits to terabits per second. This high data rate makes the analysis of radio data cumbersome and computationally expensive. While high performance computing facilities exist for large national and international facilities, that may not be the case for instruments operated by a single institution or a small consortium. Data rates for next generation radio telescopes are set to eclipse those currently in operation, hence local processing of data will become all the more important. Here, we introduce the REAL-time Transient Acquisition backend (REALTA), a computing backend at the Irish LOFAR station (I-LOFAR) which facilitates the recording of data in near real-time and post-processing. We also present first searches and scientific results of a number of radio phenomena observed by I-LOFAR and REALTA, including pulsars, fast radio bursts (FRBs), rotating radio transients (RRATs), the search for extraterrestrial intelligence (SETI), Jupiter, and the Sun.

astro-ph.IM

Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory

The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53 05'38.9", 7 55'12.7") in 2010 to study solar radio bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range 10-870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range 10-400 MHz are obtained with 4 sweeps per second over 600 channels. Here, we describe the RSTO solar radio spectrometer set-up, and present dynamic spectra of a sample of Type II, III and IV radio bursts. In particular, we describe fine-scale structure observed in Type II bursts, including band splitting and rapidly varying herringbone features.

astro-ph.SR