Rotating Radio TransientsRotating Radio Transients

Maura McLaughlinMaura McLaughlin

West Virginia UniversityWest Virginia University

12 September 200712 September 2007

The transient radio sky is relatively UNEXPLORED!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

In contrast to the situation at high energies…

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

OutlineOutline

As part of PMPS reprocessing Largest scale search for ms-s radio transients ever

Parkes Multibeam 1400-MHz receiver

Parkes Telescope

RRATs DiscoveryRRATs Discovery

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….

McLaughlin et al. 2007, Nature, 439, 817

J1819–1458

DM = 194 pc cm-3

No periodicities detected in FFT/FFA!

RRATs DiscoveryRRATs Discovery

J1443–60

DM = 374.2 pc cm-3

J1819–1458

DM = 194 pc cm-3

Periodicity of 4.26 s.

No periodicities detected in FFT/FFA!

RRATs DiscoveryRRATs Discovery

J1443–60

DM = 374.2 pc cm-3

Periodicity of 4.76 s.

Can measure periodicitiesfrom single pulse arrival times

Name P

(s)

J0848-43 5.98

J1317-5759

2.64

J1443-60 4.76

J1754-30 1.32

J1819-1458

4.26

J1826-1429

0.77

J1839-01 0.93

J1846-02 4.47

J1848-12 6.79

J1911+00 ?

J1913+1333

0.92

RRATs Discovery - periodsRRATs Discovery - periods

Periods show they must be neutron stars -> Rotating Radio Transients

RRATs Discovery - timingRRATs Discovery - timing

Timing residuals for J1317-5759

For RRATs with highest bursting rates, can time just like normal pulsars (but from single pulses!)

RRATs

AXPs XDINSs

SGRs

RRATs Discovery - timingRRATs Discovery - timing

Timing properties generally consistent with those of normal pulsars.

J1819-1458

Slight concentration towards Galactic plane (but small number stats!) Consistent with pulsar distribution

RRATs Discovery - locationsRRATs Discovery - locations

RRATs Discovery - burstsRRATs Discovery - bursts

Name w50 S1400 Np/Tobs Ndet/Nobs Np

(ms) (mJy) (hr-1) (%)

J0848-43 30 100 4.2 32 58

J1317-5759 10 1100 4.5 93 144

J1443-60 20 280 0.8 68 42

J1754-30 16 160 0.6 55 25

J1819-1458 3 3800 18.0 100 363

J1826-14 2 600 1.0 62 18

J1839-01 15 100 0.4 7 8

J1846-02 16 250 0.8 50 13

J1848-12 2 450 0.7 57 11

J1911+00 5 250 0.3 45 5

J1913+1333 2 650 4.7 60 93

McLaughlin et al. 2007, Nature, 439, 817

GBT Follow-up ObservationsGBT Follow-up Observations

GBT observation of J0848-43 at 350 MHz

J0848-43J1754-30

normal pulsars

GBT Follow-up ObservationsGBT Follow-up Observations

Never detected again inParkes or GBT observations!

J1819-1458J1826-14J1839-01J1848-12

NOT normal pulsars

Original detection of J1839-01

AO Follow-up ObservationsAO Follow-up Observations

J1911+00J1913+1333

NOT normal pulsarsObservation 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.

AO Follow-up ObservationsAO Follow-up Observations

J1911+00J1913+1333

Arecibo observations of J1913+1333 at 327 MHz

Several minutes in “on” state

NOT normal pulsars

XMM Follow-up ObservationsXMM Follow-up Observations

Spectrum fit well by absorbed blackbody plus + Gaussian. kT ~ 140 eV, nH ~ 8x1021 cm-2.

Recent XMM Epic PN data - 43 ks on RRAT J1819-1458. Radio and X-ray pulses are aligned (within uncertainties).

McLaughlin et al. 2007, ApJ, in press

RRAT properties - SummaryRRAT 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!

What are they?What are they?

Pulsars with giant pulses Intermittent pulsars

Radio populations:

Nulling pulsars Pulsars like B0656+14

Weltevrede et al. 2006B1931+24 (Kramer et al. 2006)

What are they?What are they?

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)

Explanations:

What a mess!!!What a mess!!!

How do we define a RRAT/normal/intermittent/nulling/giant pulsar????

Where do we go from here???

Population EstimatesPopulation Estimates

Lorimer et al. in preparation

Expect over twice as many RRATs as normal pulsars. With intermittent pulsars -> three times as many??

Highly dependent on assumedminimum luminosity…

€

NRRATS ≈ 2 ×105(Lmin /100mJy ⋅kpc

2)−1 × (0.5 / fon ) × (0.5 / f rfi) × (0.1/ fbeam )

Expect 20,000 RRATs detectable by SKA!

New PALFA objects

New PALFA objects

J0628+09 - PALFA discovery with P = 1.24 s and DM = 88 pc cm-3

There are RRATs in

the tropics too!

J1928+15 - PALFA RRAT candidate

Three bursts separated by 405 ms at DM = 240 pc cm-3

An extreme nuller?

There are RRATs in

the tropics too!

New PALFA objects

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!

There are RRATs in

the tropics too!

New PALFA objects

New PALFA objects

ala Cordes & McLaughlin (2003)

An extragalactic An extragalactic transient!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

- 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!!!!

An extragalactic An extragalactic transient!transient!

Lorimer et al. 2007, Science, in press

AO’s role in transient studies

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!!

.

Stay tuned!Stay tuned!

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