Lyne, Nanda! Rea, Jim Cordes, Duncan Lorimer, Michael! Kramer, Aris Karastergiou, Aidan Hotan, Dick Manchester, Andrea Possenti,! Marta Burgay, Ingrid Stairs, Nichi D’Amico, ! Fernando Camilo, Bryan Gaensler, Shami Chatterjee and Gianluca Israel ! " ! and PhD students! Evan Keane, Josh Miller and Julia Deneva ! Russell Kightley Media!
Transient (GCRT) ! Hyman et al. (2005,2006,2007)! - Radio pulses from ! magnetars! Camilo et al. (2006,2007)! - Radio pulses from brown ! dwarf TVLM 513-46546! Hallinan et al. (2007) ! - Rotating Radio ! Transients (RRATs) ! McLaughlin et al. (2006)! - Millisecond extragalactic! radio burst (MERB)! Lorimer et al. (2007)! Radio Transient Phase Space (today)!
bandwidth (50-500 MHz) as possible. 2) Signals go to filterbank or correlator to give you good time (< 1 ms) and frequency (< 1 MHz) resolution. 3) Dedisperse the data over a number of trial DMs. 4) Search each dedispersed times series for events above some threshold. 5) Repeat for different smoothings and iterate, removing bright sources. Transient radio searches!
! reanalysis of data from the Parkes ! Multibeam Pulsar Survey.! Characterized by repeated, dispersed ! radio bursts of millisecond widths.! Not detectable in standard (FFT) pulsar searches.! Periods (0.7-7 s) measured for some sources (through individual bursts) indicate they are rotating neutron stars.! J1444–6026! DM = 374.2 pc cm-3! P = 4.75 s!
and can only be studied through individual pulses….Why are they different?! Let’s look at their! 1) Numbers! 2) Burst rates and amplitude statistics! 3) Spin-down properties! 4) Spectra! 5) Polarization! 6) Multi-wavelength properties!
through their single pulses. Nearly 30 of these objects are true RRATs (i.e. only detectable through single pulses):! - 18 in Parkes multibeam survey (Keane et al. & " " McLaughlin et al.)! - 1 in Parkes high-latitude survey (McLaughlin et al.)! - 3 in GBT surveys (Hessels et al. & drifters)! - 4 in PALFA survey (Deneva et al.)! - ? with WSRT (Stappers et al.)! These numbers are all changing rapidly! The more carefully we look, the more RRATs we seem to ﬁnd!! Parkes RRATs have been followed up for roughly 4 years with monthly monitoring observations. 800 hours of time.!
J1317-5759! P = 4.75" " " " P = 2.64! But the bursts of other sources are consistent with a random distribution, and there is no evidence for quasi-periodicities (on the timescales to which we are sensitive!)!
All of the RRATs (new and old) in general have long periods.! Three timing solutions ! published in discovery! paper. Three more! since that time. Large timing! errors due to pulse-! to-pulse proﬁle ! changes.! All properties are! consistent with those! or normal pulsars,! though two have! high Bﬁelds.!
questions than they answer! Similarities to many classes of neutron stars. ! Currently analyzing joint 100-ks radio/XMM observation of J1819-1458.! X-ray spectra of J1819-1458. Strange absorption features!!!
temporarily (Zhang and Gil 2006). (Maybe some…)! “Rocking the Lighthouse” - Pulsars with asteroid belts (Cordes & Shannon 2008 and Li 2006). (How test?)! Radio counterparts to X-ray Dim Isolated Neutron Stars (XDINSs) or transient radio magnetars….continued X-ray monitoring is crucial. (Maybe some…)! Nulling pulsars? Giant-pulsing pulsars? Intermittent pulsars? Part of the normal spectrum of pulsar emission?! (For sure some relationships…)! What are they?!! Weltevrede et al. (2006) suggest B0656+14 would appear as a RRAT were it farther away.!
even make sense to describe a population of RRATs? ! We expect roughly ~10 RRATs! in PALFA and ~20 in Parkes! high-latitude surveys. ! • LOFAR surveys should! Detect many(+/-many), and over ! 30,000 could be detected! by the SKA! (Lorimer et al.! in preparation)! Population:! N RRATS ≈2×105(L min /100mJy⋅kpc2)−1 ×(0.5/ f on )×(0.5/ f rfi )×(0.1/ f beam )
difﬁculty) of known RRATs implies that there must be a large Galactic population of these objects, perhaps four times as many as the population of normal pulsars!! Spin-down, timing, spectral and multi-wavelength properties consistent with normal radio pulsars (but also show some similarities with other classes of neutron stars….two classes of RRAT – nullers and bursters?).! Timing solutions difﬁcult but possible with continued monitoring.! The cause of the unusual radio emission is an open question.! Searches on new and archival data are continuing to yield more of these objects.!
(Eatough et al. submitted) and automated search algorithms (dynamic spectra, on-the-ﬂy processing, automated periodicity searches, machine learning). See Kondratiev et al. 2008, WVU student Smithbauer.! • We need to search more parameter space (broader pulses! narrower band signals!) You will only ﬁnd what you look for! ! • BETTER POSITION LOCALIZATION CRUCIAL!! • Improved methods for pulse detection/timing in known RRATs. ! • Need better understanding of selection effects.! • Lower frequency surveys may reveal a new population of nearby transient sources.! • Follow-up is very time intensive. How will all the new sources be followed up? Are frequent short or infrequent long obs better? Will all the new sources be followed up? How will multi-wavelength follow-ups be done?!