“They missed it because they hadn’t expected to find anything like it.” 2023 July 19, NatureRead More
The GLEAM-X survey covers the entire sky south of Dec +30, using the extended configuration of the MWA, as described in Wayth et al. 2018. A description of the science motivations and survey methodology for GLEAM will be found in Hurley-Walker et al. (in prep). As in the original GLEAM survey, the sky has been divided into seven drift scans in declination and five frequency ranges as summarised below. The declinations are chosen such that the peak in the primary beam response for a given setting corresponds approximately to the half power point of the neighbouring beam along the meridian at 150 MHz. The instantaneous frequency coverage of the MWA is 30.72 MHz, so the frequency range between 72 and 231 MHz is divided into five bands that provide near contiguous coverage, but avoid the band around 137 MHz that is contaminated by satellite interference.
The observing is executed as a series of four-week-long campaigns where a single declination setting is observed in a night, covering a strip approximately 10 to 12 hours in length, depending on the time of year. The Sun can be bright and time-variable at MWA frequencies, so drift scan observations are only performed at night. Within a night, the observing is broken into a series of 120 s scans for each frequency, cycling through all five frequency settings over 10 minutes. Within a scan, typically 108 s of usable data are collected. Every 2 hours throughout the night, a calibration field is observed over all five frequency settings, again as a set of 120 s scans totalling 10 minutes. Each declination strip will receive two meridian drift scans (HA=0), one at HA=+1, and one at HA=-1, to improve (u,v)-coverage and sensitivity.
GLEAM-X observing began in January 2018 and final observations are planned for Q3 2022. We plan to release both continuum and polarisation studies using the GLEAM-X data.
If you’d like to read about the unusual long-period radio transient we discovered in GLEAM-X, you can find the paper here.
GLEAM-X is still being observed and processed. Check back here for updates on survey progress as they come in! In the meantime, check out the original GLEAM survey.
To join the team or work on pre-release GLEAM-X data, please contact Natasha Hurley-Walker via firstname.lastname@example.org.
As per the MWA large project policy, any member of the MWA collaboration can access raw GLEAM-X data for their science. This can be downloaded from the MWA node of the All-Sky Virtual Observatory.
Comparison to other surveys
|Survey Name||Frequency Range||Sensitivity||Angular resolution||Sky area|
|GLEAM-X||72 – 231||1 – 2||~45||30,000|
|GLEAM||72 – 231||6 – 10||~100||30,000|
|MSSS-LBA||30 – 74||~15||~100||20,000|
|MSSS-HBA||120 – 160||~5||~45||20,000|
|TGSS||150||2 – 5||25||37,000|
|MWACS||120 – 180||50||~180||6,100|
|Pointing Declinations (deg)||-72, -55, -40.5, -26.7, -13, +1.6, +18.3|
|Pointing HAs (hours)||0, -1, 1|
|RA ranges (hours)||4 to 21 (2018-A); 17 to 8 (2019-B)|
|Central Frequencies (MHz)||87.68, 118.4, 154.24, 184.96, 215.68|
|Frequency resolution (kHz)||10|
|Time resolution (s)||0.5|