Pauli Kehayias August 7, 2008 1

Analysis and Simulations of 6T MWA Solar Data

Pauli Kehayias Tufts University

REU Final Presentation

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MWA Background 1

- Murchison Widefield Array- 512 tile array

- 16 dipoles per 5 × 5 m tile

- Tiles spread over 1.5 km radius- 80 – 300 MHz range- 15° – 50° field of view (zenith)

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MWA Background 2

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MWA Background 3

[2]

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MWA 6T Prototype Array

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6T Solar Data

- Two hours of solar data collected (April 28, 2008)- 85 MHz, 180 MHz- 0.1 s time resolution- 10 kHz / channel, 128 channels- Alternating 2 minute runs

- Analysis motivations- Solar transients- Radio frequency interference (RFI)- Instrument performance

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Bandshapes 1

Visibilities(data)

Time

Average over time

Bandshape

128

chan

nels

Time series

Freq

uenc

y

Freq

uenc

y

Time

Average over frequency

Tiles

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Bandshapes 2

Good Bad

- 10 s average bandshape- 4/12 input signals were found to be faulty

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Transients 1

- Transient search algorithm:- Calculate 2 hr average bandshapes- Compare to 10 s average bandshapes- Look for large deviations

- Findings- Four event types- All thought to be RFI or instrumental – no solar transients

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Transients 2

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Bandshape Stability

- Examine bandshape noise over time to study performance

- Compare 10 s bandshapes to an average:- “Global” bandshape: over all data- “Local” bandshape: over the current run (2 min)

- Get root mean square (RMS) difference

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Local RMS (85 MHz)

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Average Bandshape Scaling (85 MHz)

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Average Bandshape Scaling (180 MHz)

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Bandshape Scaling Simulations

- Bandshape scaling can be due to varying signal from the sky

- Simulate potential sources:- Background radio sky- Sun (changing orientation and antenna gain)

- Results- Background radio sky is not the sole cause- Sun simulation underway

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Background Radio Sky SimulationBaseline 3, 8

85 MHz

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Sun Simulation 1

- Solar disk: 32’ [4]- 6T resolution:

- 85 MHz: ~40’ – 190’- 180 MHz: ~20’ – 90’- Vary over time

- Sun radio emission brighter near disk edge

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Sun Simulation 2Si

mul

atio

nD

ata

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Acknowledgements

Divya Oberoi

Roger CappalloRich CrowleyPhil Erickson

Madeleine NeedlesK.T. Paul

Preethi PratapAlan Rogers

Randall Wayth (CfA)

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References

1. http://maps.google.com “-26.7033194, 116.6708139”.2. MWA TWiki, Expedition 1 photos,

http://mwa-lfd.haystack.mit.edu/twiki/pub/Main/TilePhotos/tile016w.jpg.3. MWA TWiki, X3.1 Results and Analysis, Divya’s map of selected tiles for X3.1,

http://mwa-lfd.haystack.mit.edu/twiki/pub/Main/ResultsAndAnalysis/do_8T_selection.pdf.4. NASA National Space Science Data Center Sun Fact Sheet.

http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html.5. S. F. Smerd (1950), Australian J. Sci. Res. A 3, 34.

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MWA Science Goals

- Epoch of Reionization – 21 cm H emission, z = 6.5- Radio sky survey / transient search- Space weather (solar bursts, Faraday rotation, IPS)

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Average Bandshapes (85 MHz)

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Average Bandshapes (180 MHz)

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Transients 3

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Global RMS (85 MHz)

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Sun Simulation 3

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