Attendees: Gemma Anderson, Sam McSweeney, Andrew Williams, Natasha Hurley-Walker, Flora

Agenda:

Updates

o    Andrew Williams: Update on the status of MWA (5 mins)

o    Sam McSweeney: The latest epoch of the Galactic Plane Monitory (GPM) campaign (10 mins)

o    Natasha Hurley-Walker: Student project research update (10 mins)

o    Gemma Anderson: Searching for short timescale transients from long GRBs in VCS data (5 mins)

Planned publications 

o    This is an opportunity to discuss any MWA Transient publications you are working on (5-10 mins)

Upcoming MWA project meeting

o    Contributions to the Transient update talk (5-10 mins)

Minutes

Andrew Williams

• Extended mode

• Only 100 tiles

  • Solar tiles, few hundred metres from vehicle access.

  • Off line for 2 years.

  • Batteries in a bad state so - need to be carried by hand from tile to vehicle so hard to change and expensive. Cycling through all batteries for repair.

    • Don’t work through the night

    • Fibres are bad

  • 16 were completely disconnected, with fibres removed for SKA work.

    • Currently being reconnected.

• Running on reduced tiles for probably 6 months

• SHAO Receivers being installed - need two installed. For filling in the compact mode tiles - 16 tiles added to extended tiles.

  • When all SHAO receivers are fielded we will have a 256 tiles

• Questions

  • Sam: Something will have to fundamentally change about the process for the long baselines. Is this process going to continue?

    • Andrew: No budget or time to change this system Just going to try to repair the batteries. Just have to work on slow fixes. Current charging systems working since 2017 but batteries getting old.

  • Gemma: The plan is 256 tiles so something will need to be changed?

    • Andrew: Yes, and new batteries have been installed (about 100) its just that most tiles are unconnected.

  • Sam: Are batteries the most expensive part of the tiles

    • Andrew: Yes, for the solar tiles. The distance from the vehicles creates a labor too.

  • Sam: What are the code IDs?

    • 2001-2056 and their names start with LB.

    • On receivers 1, 8, 9, 13, 14, 17, 18

  • Gemma: What is the maximum baseline that we currently have?

    • LBA tiles are mostly fine - North and North East are not

    • Offline tiles in Hex will come online with SHAO recievers.

  • Same: If everything that was supposed to be working that is working, would the PSF be strange?

    • Natasha: Based on the fact the images look okay that the tiles are well distributed.

  • Andrew: If you look at the live status page, you can see which tiles are offline: http://hermes.mwa128t.org/liveplots/index.html

    • Obs info page also show the state at the time of the observation

Sam McSweeney

• Galactic Plane Monitoring (GPM) 2

  • Trying to find more ULP transients

  • Also doing additional processing to search for circularly polarised sources

  • We have GPM J1839 (the first one)

  • GLEAM-X J1627

  • ASKAP J1935

  • GCRT J1745 (the Burper)

• Try to design survey to find more

• Care about the timescale that the emission changes

  • Better to look at pulse widths (upper limits on how their pulses change)

  • GPM sensitive to between pulse widths 4s and 5 mins

  • Can widen range

• Not changing the transient search algorithm from GPM 1

  • The last step of the processing

    • Cshaned applying matched filter techniques (also to GLEAM-X)

  • Also looking for Stokes V sources

  • Now using one of the latest version of WSClean v3.4

• First light on Stokes V

  • Young Low (student) will be looking at these this semester

• Ideal for quick processing - about 2-3 days.

  • There was an automated process for GPM 1 but Sam is doing it more manually this time to go through calibration solutions

  • 70 observations per night (looks a few at the end of the night due to contamination of CygA in sidelobe)

• Web app was created with support of ADACS for GPM 1 - candidates were uploaded

  • Being upgraded this year for GPM 2

• Andrew: Can you present the coding of the difference processing pipelines at StdErr

• Seeing lots of pulsars and a new candidate!

  • New candidate is a good verification for filters

  • Its a known object but its not expected to do what has been observed

• This yet to do:

  • Pulse widths of ~1 hour timescales currently not set up for

    • Updates planned to try to be sensitive to longer timescales

  • Mix and match Stokes V search (apply filters to Stokes V)

  • Focus is to go through the processing

• Question

  • Gemma: Great to be looking in Stokes V

  • Andrew: Just fitting in all the fields right now but the GP is now starting to set

    • Natasha: Could consider longer paintings and returning to the same sky less option with the thought that some of the longer ULPs could become detected.

      • 45 mins dwell times currently. Potentially 6 hours on a given pointing would be better.

      • Touch to know the best strategies. Transients searches you want large fields.

    • Sam: Any change to the strategy could change the sensitivity to the current targets between 4s to 5 min

      • Also shorter timescales too

      • Natasha: Too difficult at low frequencies in the Galactic Plane given dispersion. GLEAM-X may be better for probing that parameter space.

        • Just let the daytime observations go.

      • Natasha: they all have different activity windows where they are on for very different timescales

        • Drives widefield and relatively shallow

        • Diminishing returns the more nights that there are no detections

        • Once you know the activity windows you would change your observing dates - so go back once a month but make sure the sky is observed for 3 hours.

          • Andrew: Good way to only see the things you expect

          • Natasha: yes but if we don’t see anything new is these few nights then we probably wont.

      • Sam: Survey designed earlier this year but things have really moved forward and changed in the field so next year we will know better how to optimise the observing strategy.

        • Natasha: Only so much MWA can find given sensitivity and frequency unless its turned into an all sky monitor.

Natasha

• Follow-up towards GPM J1839 (33 active one)

  • Possibly magnetar (but no X-ray), WD, AR Sco-type (binary WD-red dwarf system).

  • MeerKAT - unpublished but pulses get fainter over time

    • 1912-44 AR Sco-type spectrum (L band MeerKAT)

  • What if GPM J1839 is similar but on longer timescales with orbital period on 10-40 hours

    • Hoping for full time tracking for

      • MWA and MeerKAT approved so 16 hours

    • VLA DDT - if approved a further 24. If two epochs then another 24.

• Eclipsing binary MSPs (red backs) - Flora Petrou

  • Lots of follow-up found with 4 GPM 1 as well as one from VAST and one from VLA.

    • All are associated with gamma-ray counterparts

  • Two goals

    • Do they have pulsar pulsations? Only seen from VAST sources and this is because it is outside the Galactic bulge but the rest are instead the bulge.

    • Look at the difference between high and low frequencies to see how the spectrum changes as it goes through an eclipse

    • Lots of proposals submitted/accepted for uGMRT, ATCA, Parkes, MeerKAT

  • No more data so being written up soon

  • There are only 2 known eclipsing binary MSPs - if the new 6 are confirmed and all gamma-ray sources. There is therefore a strong argument for MSPs being the source of the Fermi bubbles. Just need SKA to find them as they are strongly dispersed.

• GLEAM-X (G0008) blind search

  • See Natash’a slides

Planned publications

• Please see Natasha’s slides

• Xu et al. in prep on searches for prompt radio signals from long GRBs in VCS data.

MWA project meeting

• Please send me slides