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Rotating Radio Transients

Rotating Radio Transients. Maura McLaughlin West Virginia University 12 September 2007. In contrast to the situation at high energies…. The transient radio sky is relatively UNEXPLORED!. Radio telescopes have short time scale sensitivity but very narrow fields of view.

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Rotating Radio Transients

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  1. Rotating Radio Transients Maura McLaughlin West Virginia University 12 September 2007

  2. In contrast to the situation at high energies… The transient radio sky is relatively UNEXPLORED! • Radio telescopes have short time scale sensitivity • but very narrow fields of view. • Most transient radio sources are follow-ups of • high energy detections. • But studying radio transients can teach us about • -> compact sources and explosive/dynamic events • -> fundamental physics/astrophysics • -> intervening media

  3. Outline • Parkes observations and phenomenology • GBT, Arecibo and XMM follow-up observations • What are they? • Population estimates • New Arecibo RRATs • Arecibo’s role in RRAT studies

  4. RRATs Discovery • As part of PMPS reprocessing • Largest scale search for ms-s radio transients ever Parkes Telescope • Over 750 pulsars discovered in PMPS • About 20 sources discovered just in SP - a few `bursty’ pulsars, a few objects missed in original search and 11 mysterious sources not detectable in periodicity searches More recent reprocessing shows that there are at least twice as many as this…. Parkes Multibeam 1400-MHz receiver McLaughlin et al. 2007, Nature, 439, 817

  5. RRATs Discovery J1819–1458 DM = 194 pc cm-3 J1443–60 DM = 374.2 pc cm-3 No periodicities detected in FFT/FFA!

  6. RRATs Discovery Can measure periodicities from single pulse arrival times J1819–1458 DM = 194 pc cm-3 Periodicity of 4.26 s. J1443–60 DM = 374.2 pc cm-3 Periodicity of 4.76 s. No periodicities detected in FFT/FFA!

  7. RRATs Discovery - periods Periods show they must be neutron stars -> Rotating Radio Transients

  8. RRATs Discovery - timing • For RRATs with highest bursting rates, can time just like normal pulsars (but from single pulses!) Timing residuals for J1317-5759

  9. RRATs Discovery - timing J1819-1458 Timing properties generally consistent with those of normal pulsars. RRATs SGRs AXPs XDINSs

  10. RRATs Discovery - locations • Slight concentration towards Galactic plane (but small number stats!) • Consistent with pulsar distribution

  11. RRATs Discovery - bursts McLaughlin et al. 2007, Nature, 439, 817

  12. GBT Follow-up Observations J0848-43 J1754-30 normal pulsars GBT observation of J0848-43 at 350 MHz

  13. GBT Follow-up Observations J1819-1458 J1826-14 J1839-01 J1848-12 NOTnormal pulsars Never detected again in Parkes or GBT observations! Original detection of J1839-01

  14. AO Follow-up Observations J1911+00 J1913+1333 NOTnormal pulsars Observation with AO at 327 MHz of J1911+00 No period measurable with Parkes, with only 11 pulses in total over 2 years of observations. But 6.9 s period from Arecibo observations at 327 MHz.

  15. AO Follow-up Observations J1911+00 J1913+1333 Arecibo observations of J1913+1333 at 327 MHz NOTnormal pulsars Several minutes in “on” state

  16. XMM Follow-up Observations • Recent XMM Epic PN data - 43 ks on RRAT J1819-1458. • Radio and X-ray pulses are aligned (within uncertainties). • Spectrum fit well by absorbed blackbody plus + Gaussian. • kT ~ 140 eV, nH ~ 8x1021 cm-2. McLaughlin et al. 2007, ApJ, in press

  17. RRAT properties - Summary • New sources class or one end of spectrum of normal pulsar emission? Properties vary widely from object to object! • The more we observe them the more muddled things become - two RRATs look like normal pulsars with higher sensitivity obs (but some not detected at all!) - some RRATs occasionally detected in FFT/FFA searches (but rare) • No obvious relationship between strange emission and P/Pdot (for RRATs with measured quantities) • P/Pdots (and positions) exceedingly slow going for other RRATs….. • X-ray observations for one RRAT show it is similar to both XDINSs and normal pulsars…and need positions to get obs for other sources!

  18. What are they? Radio populations: • Pulsars with giant pulses • Intermittent pulsars • Nulling pulsars • Pulsars like B0656+14 B1931+24 (Kramer et al. 2006) Weltevrede et al. 2006

  19. What are they? Explanations: • Almost-dead pulsars, brought back to life temporarily (Zhang and Gil 2005) • Pulsars with temporary reversal of radio emission direction (Dyks et al. 2005) • Pulsars with asteroid belts (Cordes & Shannon 2006 and Li 2006)

  20. What a mess!!! How do we define a RRAT/normal/intermittent/ nulling/giant pulsar???? Where do we go from here???

  21. Population Estimates Expect over twice as many RRATs as normal pulsars. With intermittent pulsars -> three times as many?? Highly dependent on assumed minimum luminosity… Expect 20,000 RRATs detectable by SKA! Lorimer et al. in preparation

  22. There are RRATs in the tropics too! New PALFA objects • J0628+09 - PALFA discovery with P = 1.24 s and DM = 88 pc cm-3

  23. There are RRATs in the tropics too! New PALFA objects • J1928+15 - PALFA RRAT candidate • Three bursts separated by 405 ms at DM = 240 pc cm-3 • An extreme nuller?

  24. There are RRATs in the tropics too! New PALFA objects PALFA survey is crucial for understanding the nature of the RRATs and the total population of neutron stars. And for discovering new classes of objects! ala Cordes & McLaughlin (2003)

  25. An extragalactic transient! - Not man-made - Cold plasma dispersion law and W~f-4.4 - Not Galactic - DM = 375 cm-3 pc - • Extragalactic! - DM ~ 1200 x z implies z < 0.3 !!! - Conservative estimate D = 500 Mpc. Lorimer et al. 2007, Science, in press

  26. An extragalactic transient! - Energy budget (@ 500 Mpc) - Radio energy output ~ 1040 erg • Brightness temperature ~1039 K - Possible sources • GRB? NS-NS coalescence? Sne? - PALFA surveys -> cosmology! • Parkes could detect out to z ~ 0.25 (1 Gpc) • AO could detect out to z ~ 0.5 (2 Gpc) extra motivation for high-b surveys! 8 times the number of sources!!!! Lorimer et al. 2007, Science, in press

  27. AO’s role in transient studies • Essential for measuring periods and timing parameters of RRATs discovered with other telescopes -> only way to understand relationship to other NSs and facilitate high-frequency and high-E obs • PALFA (and future) surveys will discover many more such objects -> crucial for understanding the population and making accurate estimates of total NS population • Such objects discovered with Arecibo will only be able to be followed up with Arecibo! • PALFA surveys should revolutionize our view of the transient radio sky in general. Future? Low-frequency multibeam system!! .

  28. Stay tuned! Even 40 years after their discovery, there is still much to be learned about radio pulsars!

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