2022-10-13

Owned by Gemma Elizabeth Anderson
Last updated: Oct 13, 2022
3 min read

Minutes for MWA Transient meeting on the theme: MWA gravitational wave follow-up during O4

Attendees: Gemma Anderson, Jun Tian, Tara Murphy, David Kaplan, Zhijun Xu, Clancy James, John Morgan Laura Driessen

Declined due to timezone or other commitments: Xiang Zhang


Agenda (see email sent on 11 Oct 2022)

General updates:

  • Update from Xiang Zhang  on flare star work (5 mins; update to be given by Gemma due to time zone restrictions)

GW themed presentations:

  • Tara (5 min): ATCA + ASKAP plans for GW follow-up
  • Gemma (10 mins): MWA follow-up strategy to probe low latency coherent/prompt radio emission from GW events.
  • Jun (10 mins): Update on coherent radio emission mechanisms and how they attenuate with binary inclination angle. Jun will then show some preliminary detection probabilities using MWA to target these models.

GW MWA discussion

Meeting minutes

General updates

Xiang Zhang:

  • MWA follow-up observations taken of FK Aqr (GLEAM-X Stokes V transient). Receiver problems that may affect data quality.
  • Simultaneous MWA and ATCA observations obtained of AU Mic. May have similar data quality issues. 
  • Potential for collaboration with a NenuFAR planetary scientist to perform exoplanet studies in Stokes V. 

Gemma Anderson

  • There is a new, bright, nearby GRB that is a good opportunity for MWA follow-up: GRB 221009A 

Xu Zhijun:

  • A few MWA triggers left so plan to observe GRB 221009A

GW themed presentations

Tara's talk:

  • OzGrav2: 2024 - umbrella to do most GW Australian follow-up. FInd out in November
  • Regardless of center results - involved in O3 follow-up for radio building on and improve
    • ATCA
    • ASKAP
    • MWA
  • Keen to coordinate with Australian groups and International groups
    • jagua group - VLA 
    • Multiple teams trying to trigger on same event then probably shared access to the data. Fairly competitive when getting results out.
  • 3 strategies/approaches
    • ATCA: monitoring GW events in criteria expect to see them. Follow up individual objects, well localised, host identified at another wavelength.
      • Follow-up IDed GW counterpart
      • Follow-up kilonova even if not associated with GW event
      • Several semester follow-up
      • Galaxy targeted survey in localisation region before EM counterpart discovered? To be discussed. 
    • ASKAP: Some set of GWs that will not be well localised so galaxy targeting strategy is hard. 
      • 30 deg^2 so not worth follow-up of individual events. Can cover significant portion of GW position uncertainty.
      • Dougal Dobie GW190814 NSBH, 10 epochs (2019,2022). (100 hrs)
      • Target fields to find the radio counterpart. 
      • Not part of VAST - guest science program. 15% of ASKAP time is allocated to guest science. Finalising details.
        • Priority
        • Discussing with John Reynolds as a strategic initiative. 
        • Very modest amount of time request. Unlikely to be many candidates. 
        • Other interesting transients found.
    • MWA: Complemented by a different strategy.
    • VLBI: Adam Deller


Clancy: May be very well localised GWs (few square degrees). If only 1 or 2 plausible host galaxy. Could trigger in galaxy <= n galaxies. 

Tara: Very strict triggering criteria. 3 competing ATCA proposals. Will also be doing VLBI program led by Adam Deller

Gemma's talk:

MWA GW follow-up strategies

Jun's talk:

Targeting coherent emission from GWs with MWA talk


John comments:

  • Written software that automatically keeps the Sun in the null. Pretty much instantaneous. 
  • Single dipole: size of field. Can't really see below 40 degrees. Our chosen metric may be overestimating the size of the field of view but it is close.
  • Always more sensitive to the Zenith regardless of the number of dipoles so stick with Zenith pointings. Full array pointed at the horizon is not much better than a Zenith-pointed observation.
  • Subarraying (fly's eye) - Not like ASKAP with single dishes. Groups of 64 or 32 tiles with different directions but throwing away baselines so strongly losing in sensitivity. 
  • Point XX beams in one point in the sky and YY to another part of the sky - double collecting area, we loose a smaller amount of sensitivity.
  • Go to an even lower frequency but still a much wider field of view but get extra time delay. Daytime observations at lower freq, the quiet Sun gets weaker and weaker - around 80 MHz. 
  • Switch pointing every 8 seconds - get some of the dispersed frequency/signals. May always get some of the signal, whether the top or bottom of band.