Bursts without memory Ryan Shannon (and Emily Petroff) 2011: EP, GH, RMS worked on bursts. 2012: JW and XZ (WC, GH, RMS): harnessing power of A+ Ax 2013: RMS resumed work in earnest in late March Today’s presentation: project outline (not any real results yet).

Do we expect bursts? Sources: Very nearby very massive, eccentric BH binary Exotic string-things Black holes are getting bigger by the day Exploration of the unknown

Project goals Develop algorithm to search A+,Ax time series for quadrupolar signatures of duration << observing span Place limits on amplitude and rates of short-duration GW events. Astrophysics? Better understand PPTA response to polarised GWs Gain better understanding of datasets (wide-sense stationary noise that could mimic burst)

Project Manifesto For what are we searching? “Data side” algorithm Not memory bursts Not continuous wave sources Complements other search algorithms “Data side” algorithm Measurements in units of Antenna power (vs. source side). Not a template-based approach Appeal to searches for radio transients for algorithms(Thornton Bursts)

Analogy to RF Detecting Radio Pulses A+, Ax are like voltage time series Null case: zero mean signal -> deviations from mean Want to make power measurement (phase likely a nuisance) Discriminating versus non-modelled noise Angular correlation of signal Sky localisation Time localisation

Differences with detecting radio bursts Issues: Time series are highly correlated Noise in time series is different Conclusion need to weight by inverse parameter covariance matrix C-1 This should mitigate effects of cross coupling, as long as C is a good estimate of covariance. Example: single measurement of +, x [+ x] C-1 [+ x]T

Progress so far Started developed tempo2 plugin Monte-carlo capabilities re-fitting global variables Identified tiny memory leak in doFit.C Definition of A+ and Ax Current definition based on KJ Lee Ryan redefined + and x on Celestial sphere and got consistent results Covariance of A+ and Ax Under what condtions are they covariant

A+,Ax corellation

Questions to answer Developing detection criterion Search in single polarisation? PTA polarisations Use of null stream? Ryan 2008-2013: Scramble pulsar positions and recalculate DS