7/26/12W. Majid1 Crab Giant Pulses W. Majid *, S. Ellingson (PI), C. Garcia-Miro, T. Kuiper, J. Lazio, S. Lowe, C. Naudet, D. Thompson, K. Wagstaff * Jet Propulsion Laboratory, California Institute of Technology

7/26/12W. Majid2 Some Facts about Giant Pulses Intense narrow pulses with a pulse energy many times that of mean pulse energy: S peak >~ 100 x Characterized by a power-law distribution of pulse energies Extremely rare phenomenon –To date only ~10 pulsars have been known to exhibit this behavior out of ~2000 known pulsars Bursts fall into narrow phase window in pulse profile The Crab exhibits ns bursts - limited by hardware (Hankins et al. 2007) –Suggests region of emission is size of a basketball –Smallest entity ever detected outside Solar system –Extreme brightness temperature - brightest in galaxy Coincident with high frequency emission

7/26/12W. Majid3 Why GPs? Only way to detect extragalactic pulsars Important for understanding the magnetospheres of pulsars Emission mechanism is not well understood How high energy emission might be linked with radio emission Conflicting claims on few detections Are GPs restricted to small group of pulsars or many waiting to be discovered Galactic pulsar population may be larger than we thought Wide range of single pulse properties apparent Algorithms relevant to transient detection phenomenon

7/26/12W. Majid4 Low Frequency Studies Why at Low Frequencies –Examine how the properties of pulse emission evolves Pulse energy frequency dependence –Scattering and dispersive effects more prominent Previous Studies –Early studies at 200 MHz suggested a turnover of the spectrum (Manchester & Taylor 1977) –23, 111, and 600 MHz studies by Popov et al suggests very steep falloff at low frequencies –MWA detected a handful of GPs at 200 MHz, none at 100 MHz (Bhat et al. 2007) –LOFAR LBA studies MHz (Stappers et al. 2011)

7/26/12W. Majid5 Low Frequency Studies Why at Low Frequencies –Examine how the properties of pulse emission evolves Pulse energy frequency dependence –Scattering and dispersive effects more prominent Previous Studies –Early studies at 200 MHz suggested a turnover of the spectrum (Manchester & Taylor 1977) –23, 111, and 600 MHz studies by Popov et al suggests very steep falloff at low frequencies –MWA detected a handful of GPs at 200 MHz, none at 100 MHz (Bhat et al. 2007) –LOFAR LBA studies MHz (Stappers et al. 2011)

7/26/12W. Majid6 Low Frequency Studies LWA Advantages –30% greater sensitivity (256 stands, coherently combined) –Up to ~80 MHz BW (with 3 beams) –Location better for Crab –Multi-beaming capability –Low RFI environment –Excellent prospects for pulsar and transient science

7/26/12W. Majid7 Single Dispersed Pulses with the LWA (P. Ray) Crab Giant Pulse Campaign –160 hours over 10 months –Can coordinate with higher frequencies at GAVRT, GBT –Can coordinate with Fermi for radio/gamma correlation studies Single Dispersed Pulse Survey –160 hours over 11 months –Survey will establish limits on LIGO sources, discover or study RRATs GCN-triggered observations of GRBs –80 hours over 10 months –Dispersive delay gives time for interrupting observing and repointing –New MCS event-triggered observing capability applicable to other projects

7/26/12W. Majid8 Crab Pulsar Observations DateHH:MM (UTC)Duration (hr) : : : : : : : : : :004 S. Ellingson

7/26/12W. Majid Observation of the Crab Crab pulsar was observed at L-band from 19:57:00 – 21:40:00

7/26/12W. Majid Observation of the Crab Crab pulsar was observed at L-band from 19:57:00 – 21:40:00

7/26/12W. Majid Observation of the Crab 13 kJy, 8  s wide

7/26/12W. Majid Observation of the Crab LWA Observation: 4 Beams: 2 pointed at the Crab; 2 pointed off the Crab 0.7 hr in RA Beams 1&3: 60, 76 MHz (dual pol) Beams 2&4: 28, 44 MHz BW = 19.6 MHz 4x1TB drives (mattingly,koubek,kalbfus, and roosa - MLB?) Frequency (MHz)Dispersive Delay (s)

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7/26/12W. Majid Observation of the Crab Using LSL tools: looking at spectra, waterfall plots, time series Extracting voltage data to apply coherent dedispersion on 50s of data starting at the time of the L-band GP Stay tuned …

7/26/12W. Majid17 Implications for Single Dispersed Pulse Detections Pulsars Sources (Known) –Giant Pulses –Rotating Radio Transients (RRATs) –Anomalously Intensive Pulses (AIPs) Suspected Sources –Prompt Emission from GRBs –Compact Object Mergers (LIGO/VIRGO events) –Evaporating Primordial Black Holes –Cosmic Strings Unknowns –Magnetars? –Much unexplored search space Period derivative (s s -1 ) (Keane et al. 2011) Period (s)

7/26/12W. Majid18 FIN

7/26/12W. Majid19 Crab GPs Microstructure

7/26/12W. Majid20 Fermi Studies Source of GP emission currently unknown –Changes in coherence of radio emission –Changes in pair creation rate in the pulsar magnetosphere –Changes in beaming direction Correlation studies with high energy emission is one way to pin-point the origin of GP emission –Look for increase in high-energy flux during GP emission –Look for frequency dependence of GP emission and coincidence with high energy emission

7/26/12W. Majid21 Fermi Studies (in progress) Expect ~100 coincidences over the course of this study