1. 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).

2. 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

3. 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)

4. 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)

5. 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

6. 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

7. 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

9. A+,Ax corellation

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