Limits on millisecond transients with ARTEMIS on LOFAR

Aris Karastergiou

Transcript

1. Limits on millisecond transients with ARTEMIS on LOFAR Wednesday, 8 January 14
2. ARTEMIS has no confirmed detections yet... Lorimer 2007 Keane 2012 Wednesday, 8 January 14
3. LOFAR international stations • Large collecting area, high sensitivity • 96 coherently added dipoles x 2 pol • Very fast sampling rate, 5.12μs voltage data • Large fields of view, e.g. 30 sq.deg in 8x6MHz beams at ~150 MHZ • Large amounts of available time Wednesday, 8 January 14
4. Griffin Foster Wednesday, 8 January 14
5. Dell Poweredge C6100 Dell Poweredge C410x Stef Salvini Wes Armour Dalal Ait Allal Mike Giles Chris Williams Steve Roberts Fred Dulwich Ben Mort Alessio Magro Aris Karastergiou hardware Wednesday, 8 January 14
6. Frequency (MHz) Time (ms) 8000 8200 8400 8600 8800 9000 143 144 145 146 147 148 149 20 30 40 50 60 200 400 600 800 0 2000 4000 6000 8000 Time bin 40 60 100 200 300 400 500 600 700 800 900 dB Frequency channels Pulse Wednesday, 8 January 14
7. Frequency (MHz) Time (ms) 8000 8200 8400 8600 8800 9000 143 144 145 146 147 148 149 16 18 20 22 24 26 28 30 200 400 600 800 0 200 400 Time bin 22 24 26 100 200 300 400 500 600 700 800 900 dB Frequency channels Wednesday, 8 January 14
8. dynamic noise modelling for effective RFI removal and transient detection filterbank noise pre-filtering filterbank noise post-filtering Wednesday, 8 January 14
9. DM time (s) GPU dedispersion test: 1500 measures searched in real-time, only pulses from B0329+54 detected, no spurious signals Wednesday, 8 January 14
10. Real time detection system which would easily detect RRATs and Lorimer burst as they happened. Affordable and scalable hardware 26 December 2011 drift scan with beam at Dec=+21º B1919+21 Crab time (s) Crab B1919+21 Wednesday, 8 January 14
11. Wednesday, 8 January 14
12. ARTEMIS survey I • 1000 h of observations • 8 beams on Greenwich meridian • 143 - 149 MHz • ~2000 x 3.05 kHz channels • ~40 Jy (at 8σ) over 2ms integrations • DMmax = 150 pc / cm3, δDM = 0.1 • Sampling local Galactic population (really?) Wednesday, 8 January 14
13. ARTEMIS survey I For 40 Jy (8σ) sources in 2ms integrations: R < 1/1000h/30deg2 ≈ 30 sources / sky / day ≈ 3x10-5 sources / deg2 / hour Wednesday, 8 January 14
14. Scattering Bhat et al. 2004 Wednesday, 8 January 14
15. DM (pc/cm3) log10(o sc ) (ms) 100 101 102 103 −10 −8 −6 −4 −2 0 2 4 6 Pulsars Extragalactic FRBs o sc = 10ms at 1GHz o sc = 10ms at 350MHz o sc = 10ms at 150MHz A peculiar population FastRadioBursts Wednesday, 8 January 14
16. Galactic & Extragalactic scattering Maximum scattering occurs when midway between the pulsar and Earth Lorimer et al. 2013 Wednesday, 8 January 14
17. DM (pc/cm3) log10(o sc ) (ms) 100 101 102 103 −10 −8 −6 −4 −2 0 2 4 6 Pulsars Extragalactic FRBs o sc = 10ms at 1GHz o sc = 10ms at 350MHz o sc = 10ms at 150MHz DM ~ 1200 z pc/cm3 z ~ 0.1 z ~ 0.5 Lorimer et al. 2013 Wednesday, 8 January 14
18. ARTEMIS survey I R < 1/1000h/30deg2 ≈ 30 sources / sky / day Assuming: • z = 0.1 and limit at 40 Jy • some cosmological expansion • rates of fast transients from high frequency surveys • high frequency surveys probe much greater volumes we can extract some limits on the spectra of these objects Wednesday, 8 January 14
19. Standard candle model Uniformly distributed, 1Jy peak flux at z = 0.75 Artemis 1 Artem is I1 (prediction) 0.75 events per day Wednesday, 8 January 14
20. ARTEMIS survey II Wednesday, 8 January 14
21. ARTEMIS survey II • Out to DM of 320 pc / cm3 • 288 hours completed on 30 deg2 • Upper limit of 111 sources/sky/day • 10 times less than Extragalactic standard candle prediction Wednesday, 8 January 14
22. The hundred tied-array-beams realtime processor LOFAR APERTIF MeerKAT SKA-I SKA-II RFI-excision dedispersion folding detection CPU - GPU cluster Slide from Oxford TKSP meeting Wednesday, 8 January 14