Fast Radio Bursts The chase is on. Sarah Burke Spolaor National Radio Astronomy Observatory with C. Law, G. Bower, B. Butler, P. Demorest, J. Lazio, M. Rupen, many others
S P A C E
S P A C E f At source f At Earth t t
S P A C E f At source f At Earth t t
S P A C E f At source Dispersion measure f At Earth t t
S P A C E f At source Dispersion measure f At Earth t t
S P A C E Scattering and Scintillation Lorimer+Kramer05
S P A C E Scattering and Scintillation τ Lorimer+Kramer05 600MHz 400MHz 325MHz 240MHz Our galaxy: τ ~ f 3.8 to -4.4 Lorimer+Kramer05
Voilà (FRB) τ f 4.0 ± 0.4 DM = 944 pc/cc dt f 2.000 ± 0.006 Thornton+13
Voilà (FRB) Unknown dispersion contribution Known (Milky Way) dispersion contribution
NE2001 electron density model: Cordes & Lazio (2002) FRBs excess dispersion Dispersion excess Repeater (Spitler+16, Scholz+16) Keane+11 Pulsars FRBs
NE2001 electron density model: Cordes & Lazio (2002) FRBs excess dispersion Dispersion excess DANGER ZONE! Repeater (Spitler+16, Scholz+16) Keane+11 Pulsars FRBs
FRB Distances Intergalactic Medium (IGM) Dispersion Measure contribution (pc/cm 3 ) Inoue (2004) model IGM: 24% He, 76% H Ionization fraction 1.0 All excess attributed to IGM
FRB Distances Intergalactic Medium (IGM) Dispersion Measure contribution (pc/cm 3 ) Inoue (2004) model IGM: 24% He, 76% H Ionization fraction 1.0 50% excess attributed to IGM
Scattering, dispersing, absorbing, and polarizing media
What are they? What can we use them for?
Where What are they? What can we use them for?
Baryonic census/ Detecting a WHIM Photon mass constraints (Wu+16, Bonetti+16) Cosmic Magnetism (Gaensler+16) Shull+12, Keane+16
Baryonic census/ Photon mass constraints Detecting a WHIM Shull+12, Keane+16 (Wu+16, Bonetti+16) Coherent emission processes! Cosmic Magnetism (Gaensler+16) Extreme and rare events! IGM turbulence!
Online FRB Catalog: http://astronomy.swin.edu.au/pulsar/frbcat/ Molonglo: 2 GBT: 1 Arecibo: 1 Parkes: 19 Repeating FRB FRB emitter size limit Single FRBs Pulsars Detected at 0.7-1.5 GHz. About 1 per 10 seconds. Half of them scattered.
FRB is somewhere in this region What s Missing? PARKES GBT Molonglo VLA best VLA worst Arecibo VLA
What we do know Sky image: Alix Mellinger
What we do know Galactic Plane ( b <15º) <800/sky/day High Latitudes ( b >15º) 5000/sky/day Sky image: Alix Mellinger
What we do know Dispersion Measure - ne, distance Rotation measure, RM ~ B ne(l)dl - ne, distance, B-field Scattering tail/timescale, τ Scintillation bandwidth, Δf ~ 1/(2 π τ) location and clumpiness of material Scattering index, µ; τ ~ f µ - intervening medium turbulence Polarization fraction (circular, linear) Polarization angle (vs. time) source magnetism Spectral index limits - source, and progenitor absorption/density
Masui et al. (2015)
Polarization
Local Environment Limits If too dense / high optical depth Free-free absorption (complete?) Deviation from dt ~ f -2 Drastically-rising spectrum (α > 5) Spectral index limits α(150 MHz) > 0.1 (Karastergiou+15) α(7.5 GHz) < 4.0 (Burke-Spolaor+15) Image credit: ESO Kulkarni et al 2015; Luan & Goldreich 2015; Katz 2015, and others
So... What are FRBs?
Ask Professor January 2015
Theories in the Literature Video: NRAO Two compact things smashing together (e.g. Kashiyama+13, Geng&Huang15, ) Magnetar flares/neutron star pulses (Lyubarsky 2014, Cordes+15, Pen&Connor15, Connor+15) Supernovae-induced NS flares (e.g. Egorov+Postnov 2014) BLITZAR! (Falcke+Rezzolla 2013) Kilonovae (Niino+14) Planet magnetosphere/neutron star interaction (Mottez+Zarka 2014) Quark Novae (Shand+15) Superconducting cosmic strings (Yu+14) Primordial BH evaporation (Keane+12, Rees 1977) Galactic flare stars (Loeb+13, Maoz+15)
Summary: Progenitor Constraints Avoid galactic plane z up to ~ a few Emission Region < 180 km TB > 1030 K (COHERENT, NON-THERMAL) Rates 4.4x103 / sky / day (Rane+15) > 103 / Gpc / year > 10-3 / galaxy / year IGM, host + progenitor contributions: must balance RM, DM, f-f absorption, scattering, emission measures of feasible objects 1+ progenitors?
The road ahead
Strongest paths forward Higher-energy counterparts Host (galaxy) identification Detailed radio properties and statistics
In practical terms Real-time detection Localization High detection rates
Parkes FRB 140514 DM distance: z ~ 0.44 Petroff+15
Science Parameter Space
at the Jansky VLA 5ms samples 3 x Parkes equivalent collecting area 1 Fast Radio Burst per 300-600 h on-sky
at the VLA 5ms Very Large Array Image!
Present: It s only a matter of time! Fluence (Jy ms) Law et al. (2015)
What s next for? REAL-TIME PROCESSING (GPUs). Rapid follow-up of localized galaxy COMMENSAL OBSERVING. 10-50 bursts per year?
THE CHASE IS ON!