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Fast Radio Bursts Simon Johnston, CSIRO Astronomy & Space Science the Labyrinth of the Unexpected May 2017

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Fast Radio Bursts Simon Johnston, CSIRO Astronomy & Space Science the Labyrinth of the Unexpected May 2017 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 relavisZc 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 mulZbeam (coincidence detecZon) 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 interesZng 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 interesZng 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 scaering led to the interpretaon that the Lorimer burst had an extragalacZc origin. Sociology was generally posiZve, and favoured the astrophysical signal interpretaon 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 scaering led to the interpretaon that the Lorimer burst had an extragalacZc 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 posiZon. 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 mulZple 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 ExtragalacZc? Atmosphere ? GalacZc Source Unknown Lightning? Pulsars The prevailing sociology was that the Lorimer Burst was a Peryton and thus likely terrestrial (and so uninteresZng 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 Descripon Keith et al. 2011 MNRAS Galacc Plane (Kramer – Einstein) RelavisZc 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 Interpretaons: Few ms pulse width, Jy peak flux density Blitzar Implied rate = 10000/sky/day Flare stars (galacZc) = 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-Zme Heimdall implementaon at Parkes. Some FRBs are double peaked! Labyrinth - Kerastari | Simon Johnston HTRU at low latitudes – Petroff et al. (2015) DETECTED NOTHING! GalacZc effects reduce the signal-to-noise over a small fracZon of the survey However we (a) Rule out an isotropic distribuZon with 99% confidence (b) Rule out high DM galacZc origin (eg flare stars) Yes! ScinZllaon boosts the Is there some other high latude detecZon rate (galacZc) 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 distribuZon is highly non-isotropic at >90% confidence level. Rate at high latude 7100 FRBs/sky/day at Parkes sensiZvity Rate at low latude 1700 FRBs/sky/day. This is one FRB per 250 hours observing at high laJtudes. Rate is ~1 per 1000 years per M* galaxy to z~1 (completeness very hard to quanZfy) Some FRBs are double peaked, some show scaer 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 ExtragalacZc Radio Bursts Real-Zme data processing and search to find pulsars and FRBs in real Jme. Uses Parkes telescope, GPU backend and Swinburne supercomputer. Sovware includes pulsar search, FRB search and neural network learning. Quasi real Zme triggering of other telescopes (opZcal, radio, X-ray) Labyrinth - Kerastari | Simon Johnston The Peryton Mystery Solved! MNRAS 2015. Labyrinth - Kerastari | Simon Johnston FRB 150418 Discovery Real Jme detecJon! 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! OpZcal galaxy; redshiv 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 redshiv 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 redshiv “agree” with the models • Consistent with scinZllaon from the central AGN? • The sky may be more variable at low flux levels • Similar behaviour also seen in the source potenZally associated with the Ravi et al. FRB which has a be_er source locaon. The repeater also has a variable host galaxy. The Sociology was extremely hosZle against this associaon with “trial by facebook” and poor behaviour from certain secZons of the community. Labyrinth - Kerastari | Simon Johnston My take on the strangeness of FRBs • They are extragalacZc • Repeaters versus non-repeaters? • Hard to understand lack of repeZZon in bright bursts • But two classes also not really jusZfied (but the RRATs) • Bright versus weak? • Too many bright ones • GalacZc latude 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 instrumentaon à detecZon • New instrumentaon à detecZon • Student vigilance! • Student vigilance! • Distance : local galaxy • Distance : extragalacZc • Polarizaon detected • Polarizaon detected • Complex pulse structure • Double structure • ScinZllaon • ScinZllaon • No counterparts at other λ • No counterparts at other λ • Mechanism: oscillang WDs • Mechanism: many and varied (rotaon not considered, aliens including pulsars, black holes, rejected) aliens • Gold 1968 paper : rotang 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 applicaons 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 .
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