Fast Radio Bursts Simon Johnston, CSIRO Astronomy & Space Science The Labyrinth of the Unexpected May 2017
CSIRO ASTRONOMY & SPACE SCIENCE In the very very beginning …
Labyrinth - Kerastari | Simon Johnston In the very very beginning …
It was Jocelyn Bell of course who set it all going in 1967 …
Labyrinth - Kerastari | Simon Johnston In the beginning …
Labyrinth - Kerastari | Simon Johnston In the beginning …
In the 1970s we “knew” that pulsars were highly periodic. Computers became more powerful and the “Discrete Fourier Transform” was invented.
Labyrinth - Kerastari | Simon Johnston In the beginning … The Hulse/Taylor Arecibo survey was the first to use digital computers and FFTs (rather than pen charts and analogue systems) to find pulsars. In the 1970s we “knew” that pulsars were highly periodic. Computers became more powerful and the “Discrete Fourier Transform” was invented.
… and later won the Nobel Prize for their discovery of a rela vis c binary pulsar.
Labyrinth - Kerastari | Simon Johnston Back to the Future …
By the early 2000s the number of pulsars discovered was around 2000 and searching for single pulses had long fallen out of fashion.
Then Maura McLaughlin discovered the RRATs in a Parkes pulsar survey!
And was able to use the mul beam (coincidence detec on) to discriminate between pulses and interference.
Labyrinth - Kerastari | Simon Johnston McLaughlin et al. (2006) : Rotating Radio Transients (RRATs)
3 examples of RRATs. Very sporadic emi ers, but they do repeat at the same DM if you wait for long enough. Their DMs are consistent with galactic. They are The FFT search does almost certainly not find RRATs! Neutron Stars
Labyrinth - Kerastari | Simon Johnston And then …
Single pulses became interes ng again! And people started looking through old datasets using Maura’s technique to look for RRATs and other things …
Labyrinth - Kerastari | Simon Johnston And then …
Single pulses became interes ng again! And people started looking through old datasets using Maura’s technique to look for RRATs and other things …
And so the Lorimer Burst!
Labyrinth - Kerastari | Simon Johnston The Lorimer Burst …
(apologies to Michelangelo and the Bishop)
Labyrinth - Kerastari | Simon Johnston LORIMER BURST (2001 data, published in Lorimer et al. 2007)
Labyrinth - Kerastari | Simon Johnston The Lorimer Burst …
There was the Lorimer Burst.
Hugely bright, “perfect” cold plasma law dispersion. DM was much higher than expected from the Galaxy. This plus sca ering led to the interpreta on that the Lorimer burst had an extragalac c origin.
Sociology was generally posi ve, and favoured the astrophysical signal interpreta on
Labyrinth - Kerastari | Simon Johnston The Perytons emerge …
There was the Lorimer Burst.
Hugely bright, “perfect” cold plasma law dispersion. DM was much higher than expected from the Galaxy. This plus sca ering led to the interpreta on that the Lorimer burst had an extragalac c origin.
And then there came …
Sarah’s discovery of The Perytons!
Labyrinth - Kerastari | Simon Johnston Burke-Spolaor et al. (2010) : Perytons
Perytons are seen in all 13 beams of the MB simultaneously. They have DMs of 300-500 (similar to the Lorimer burst). They do not repeat in sky posi on.
The (then) explanation was that they are most likely Terrestrial in origin. Perhaps from lightning or other atmospheric ducting effects.
Labyrinth - Kerastari | Simon Johnston Peryton Examples (Burke-Spolaor et al)
Perytons are seen in mul ple beams but appear to be dispersed with a DM of ~300. The DM sweep looks patchy. They have pulse widths of a few ms.
Labyrinth - Kerastari | Simon Johnston Confusion in 2010
What Lorimer Perytons RRATs # Beams 1 All 1 Dispersed Yes Yes Yes DMs ~400 300-500 < 300 Repeat No No? Yes Origin Extragalac c? Atmosphere ? Galac c Source Unknown Lightning? Pulsars
The prevailing sociology was that the Lorimer Burst was a Peryton and thus likely terrestrial (and so uninteres ng to the astrophysics community).
Labyrinth - Kerastari | Simon Johnston Parkes Pulsar Survey
The High Time Resolution Universe (HTRU) Survey for Pulsars and Transients
Students maketh the survey!!
Labyrinth - Kerastari | Simon Johnston Survey Descrip on Keith et al. 2011 MNRAS
Galac c Plane (Kramer – Einstein) Rela vis c Binary pulsars (Cameron et al. In Prep).
Intermediate (Bailes – MSPs) Maximise the MSP yield 27 MSPs found!
All Sky (Johnston – unknown) Sky largely unsurveyed FRBs found!
64 us sampling, all digital 5 Tbytes/day Northern hemisphere Swinburne supercomputer with Effelsberg
Labyrinth - Kerastari | Simon Johnston Published in Science 2013 (data 2 years old)
4 FRBs detected DMs extremely high Interpreta ons: Few ms pulse width, Jy peak flux density Blitzar Implied rate = 10000/sky/day Flare stars (galac c) = 1 per 1000 yr per M* galaxy Magnetar flares Atmospheric Cosmic strings Giant pulses
Labyrinth - Kerastari | Simon Johnston Four Thornton bursts
DM=950
Dispersed + Scattered behaves very milliseconds much like ISM (unlike Perytons) Positions only good to 2 beamwidths • DMs Lat (30 arcmin) • 944 pc/cc -55 723 pc/cc -42 Associating DM with distance and • knowledge of the IGM then DM=1200 • 1103 pc/cc -59 corresponds to z=1. • 553 pc/cc -66
Labyrinth - Kerastari | Simon Johnston Five more bursts from HTRU – high latitude processing
Champion et al. 2016. MNRAS.
• Date Lat DM S/N • 09-06-25 +28 899 28 • 12-10-02 -26 1680 12 • 13-06-26 +27 956 15 • 13-06-28 +31 471 20 • 13-07-29
From 2013, FRBs detected using the real- me Heimdall implementa on at Parkes.
Some FRBs are double peaked!
Labyrinth - Kerastari | Simon Johnston HTRU at low latitudes – Petroff et al. (2015)
DETECTED NOTHING!
Galac c effects reduce the signal-to-noise over a small frac on of the survey
However we (a) Rule out an isotropic distribu on with 99% confidence (b) Rule out high DM galac c origin (eg flare stars)
Yes! Scin lla on boosts the Is there some other high la tude detec on rate (galac c) effect we (Macquart & Johnston 2015) are not considering?
Labyrinth - Kerastari | Simon Johnston HTRU Summary of Fast Radio Bursts
10 FRBs were found by the HTRU survey in total. The distribu on is highly non-isotropic at >90% confidence level. Rate at high la tude 7100 FRBs/sky/day at Parkes sensi vity Rate at low la tude 1700 FRBs/sky/day. This is one FRB per 250 hours observing at high la tudes. Rate is ~1 per 1000 years per M* galaxy to z~1 (completeness very hard to quan fy)
Some FRBs are double peaked, some show sca er broadening, some appear to be unresolved at the 100us level. None of the Parkes FRBs repeat (yet).
Sociology: The Thornton et al. paper clinched the deal that FRBs were astrophysical and different to the Perytons. Nitpicking (largely from the US) that “FRBs only occur at Parkes”
Labyrinth - Kerastari | Simon Johnston SUPERB Survey
SUPERB = SUrvey for Pulsars and Extragalac c Radio Bursts
Real- me data processing and search to find pulsars and FRBs in real me. Uses Parkes telescope, GPU backend and Swinburne supercomputer. So ware includes pulsar search, FRB search and neural network learning.
Quasi real me triggering of other telescopes (op cal, radio, X-ray)
Labyrinth - Kerastari | Simon Johnston The Peryton Mystery Solved!
MNRAS 2015.
Labyrinth - Kerastari | Simon Johnston FRB 150418 Discovery
Real me detec on!
RA 07:16 Dec -19:00 gl,gb = 232.7, -3.7 DM=776 Speak = 2.2 Jy Wobs = 0.8 ms Hint of L No RM measured No real V
Labyrinth - Kerastari | Simon Johnston FRB 150418
Variable radio source detected!
Op cal galaxy; redshi obtained
Labyrinth - Kerastari | Simon Johnston FRB150418 – radio light curve Keane et al. Nature
Labyrinth - Kerastari | Simon Johnston FRB150418
NATURE 2016
Labyrinth - Kerastari | Simon Johnston FRB150418 – missing baryons
The DM gives all the baryons along the line of sight, and so knowledge of redshi allows Ωb to be determined!
Ωb = 4.9 +/- 1.3 % consistent with the WMAP result
Labyrinth - Kerastari | Simon Johnston FRB150418 – radio light curve Keane et al. Nature
Labyrinth - Kerastari | Simon Johnston FRB150418 – radio light curve Johnston et al. MNRAS 2017
Labyrinth - Kerastari | Simon Johnston FRB150418 – associated or not?
• This is a strange and seemingly rare type of variable • The DM and the redshi “agree” with the models • Consistent with scin lla on from the central AGN? • The sky may be more variable at low flux levels • Similar behaviour also seen in the source poten ally associated with the Ravi et al. FRB which has a be er source loca on. The repeater also has a variable host galaxy.
The Sociology was extremely hos le against this associa on with “trial by facebook” and poor behaviour from certain sec ons of the community.
Labyrinth - Kerastari | Simon Johnston My take on the strangeness of FRBs • They are extragalac c • Repeaters versus non-repeaters? • Hard to understand lack of repe on in bright bursts • But two classes also not really jus fied (but the RRATs) • Bright versus weak? • Too many bright ones • Galac c la tude dependence? • HTRU says yes, but SUPERB less convincing • Spectral features? • Completeness / detectability • High rates? • >1000x GRB rate • Not NS if z>0.5
Blitzar model (Falcke & Rezzolla) Giant pulse model (Cordes et al.)
Labyrinth - Kerastari | Simon Johnston Pulsar and FRB history compared
• New instrumenta on à detec on • New instrumenta on à detec on • Student vigilance! • Student vigilance! • Distance : local galaxy • Distance : extragalac c • Polariza on detected • Polariza on detected • Complex pulse structure • Double structure • Scin lla on • Scin lla on • No counterparts at other λ • No counterparts at other λ • Mechanism: oscilla ng WDs • Mechanism: many and varied (rota on not considered, aliens including pulsars, black holes, rejected) aliens • Gold 1968 paper : rota ng NS, • Theory paper exists already? (But lighthouse, slow-down, Crab which one!!??) • Single dishes reign supreme • Wide FoV telescopes key (?) • 50 years of glorious history with • Future ahead in cosmology if many physics applica ons detectable beyond z~1 • Less glorious – MSPs, 87A, planets • Less glorious – perytons, facebook
Labyrinth - Kerastari | Simon Johnston Thank you ASTRONOMY & SPACE SCIENCE Simon Johnston Head of Astrophysics t +61 2 9372 4573 e [email protected] w www.atnf.csiro.au
CSIRO ASTRONOMY & SPACE SCIENCE