Minutes for MWA Transient meeting on theme "Polarised/Stokes V Transients"
Attendees: Gemma Anderson, Chenoa Tremblay, Christene Lynch, Bryan Gaensler, Xiang Zhang, Laura Driessen, Sam McSweeney, John Morgan, George Heald, Jai Chauhan, Steve Prabu, Susmita Sett, Zhijun Xu
Registered attendees: Gemma Anderson, Chenoa Tremblay, Christene Lynch, Bryan Gaensler, Xiang Zhang, Laura Driessen, Sam McSweeney
Tentative: Clancy James, James Miller-Jones
Declined due to timezone or other commitments: Joe Callingham (2am in Europe), Natasha Hurley-Walker (meeting clash), Tara Murphy, Joshua Pritchard + VAST members (OzGrav retreat clash)
Declined: Randall Wayth, Paul Hancock, Lister Staveley-Smith, Miguel Morales, Martin Bell
Proposed Agenda (see email sent on 23 Nov 2022):
- Xiang Zhang (Shanghai Astronomical Observatory) will present her work on a flaring M dwarf detected in GLEAM-X data.
- General updates from individual members on the Polarised/Stokes V transients theme - This does not need to be limited to MWA work but can include ASKAP, MeerKAT, LOFAR, optical, etc. Updates could include:
- Recent results
- Current/planned research
- New ideas for proposals/collaborations
- Stokes V/polarisation transient work planned during MWAX science commissioning
- Discussion regarding future meeting scheduling and flexibility
- Future discussion on this or a similar theme (particularly in a different time zone)
- General scheduling discussion
- Any other business
Christene: Exoplanets with MWA - 2018 paper - crossmatch with known exoplanets
- LOFAR best bet - predicted this should be possible.
- Joe's paper 1mJy - very challenging for MWA - LOTSS, cross-match with GAIA to find them, Stokes V selection
- Phase II MWA - GLEAM-X and LOBES 1 sigma sensitivity of mJy - much longer integrations
- longer last emissions found so could try long integrations
- Some emissions only last 1 hour so wont gain anything with longer integrations.
- Few dozen sources may be possible with MWA (looked at Emil's polarisation survey - GLEAM data)
- Could pick your favourite targets and try stacking? Might need 10s of hours
- Highly circularly polarised (>70%)
Further project on bright M dwarfs
- Continue working on objects that may produce bright bursts - e.g. UV Ceti
- The following year did 100 hours but did not detect anything - so emission is not very stable
- Duty cycle about 1 %
- Processing all archival MWA data on UV Ceti to look at long term variability
- A list of 10 bright objects
- Stokes V RTS on these images - RTS very fast and don't need to clean in Stokes V
- Incorporate GMRT
- Archival data that has not been processed (not GLEAM data that Emil used for his paper).
- Targeted sources of specific objects need lots of extra data unless the objects are really flaring.
- John - emphasize Stokes V polarisation calibration improvements done with GLEAM-X
- Recommends transferring this knowledge between GLEAM-X, GeG, and this project.
- Christene - Use RTS to see if there is a flare and then do proper imaging if there is a detection - see if there is a big improvement
- Chenoa - Quick RTS search may be only hitting the highest threshold
- Christene says sensitivity dependence is definitely in Stokes I but probably not a problem in Stokes V
- Would definitely want to do GLEAM-X processing of any Stokes I images when a Stokes V detection is found
- Sammy - there is some Linear and Circular polarisation swapping if calibration is not done properly so there may be some sensitivity loss in Stokes V with RTS.
- Christene: Worth looking at level this occurs (original work also done with analytic beam). Position in the primary beam will also have different effects on the leakage.
Xiang Zhang: Stokes V transient discovery in GLEAM-X data (FK Aqu)
- POGS-X circular: M dwarf detection - double M dwarf binary
- 73% circular pol, 1/10th of observations covering sky region, no linear pol
- Known radio star - VLA detection
- Sits at edge of GAMA-23 field
- ATCA follow-up - source detected
- Stokes V light curve 0.02-0.08 Jy
- Christene
- no common light curve for flare stars as dependent on the different properties of the stars. Not sure what causes the flare - could be an episodic burst or a hot spot with stellar rotation.
- Only have dirty Stokes I image so haven't detected it yet. Should be detectable in a clean Stokes I image (snapshots)
- Tim's catalogue does have a detection in the Stokes I catalogue.
- Laura
- The periods of the binaries are on the order of a day. Could be radio emission from interaction
- Next step to make clean Stokes I snapshot images
- See if the fractional polarisation changes
- Christene - send lots of info and references on this star
Laura Driessen: Looking at ASKAP POSSUM
- Stokes I and V matches (similar to what Joe did with GAIA) many stellar matches/chance coincidences
- Something more similar with STOKES I - RS CVn low polarisation (chromospheric activity and gyrosynchrotron emission)
- Stellar matches using machine learning
- Need another filtering criterion as chance coincidences are still very high. (Not Stokes V)
- Ultimate would be X-ray matches
- One of the target sources is detected in ROSAT but not detected in the radio
- Gemma - eROSITA-AAL MoU - contact Time Domain team or a Galactic team - all-sky - a catalogue of X-ray sources (not just flares - want quiescent detections)
- Laura to be joint project scientist in VAST
- Christene - VAST doing a lot of work (Josh and Mark have a paper). Look at the overlap with Mark - unbiased search for radio stars in RACS data - GAIA and colour-colour cross-match selections in Stokes I.
- Laura is hesitant to do colour cuts with binary systems
- Straight forward MWA synergy - if in ASKAP see if it is there in MWA - coherent vs incoherent
- Find them first in ASKAP
Sam McSweeney
- PSR group interested to close the loop on the polarisation GLEAM-X work
- Want to reproduce same polarisation corrections
- PSRs give more stringent tests on polarisation corrections
- Working with John to make sure GLEAM-X and pulsar polarisation are consistent
Agree with ultinating timezone - VAST does this.