Recent Results and the Recent Results and the Future of Radio Afterglow Future of Radio Afterglow

ObservationsObservations

AlexanderAlexander van der Horst van der HorstAstronomical Institute Anton PannekoekAstronomical Institute Anton Pannekoek

University of AmsterdamUniversity of Amsterdam

Suite of radio follow-up observatoriesSuite of radio follow-up observatories• Very Large ArrayVery Large Array• Westerbork Synthesis Radio TelescopeWesterbork Synthesis Radio Telescope• Australian Telescope Compact ArrayAustralian Telescope Compact Array• Giant Metrewave Radio TelescopeGiant Metrewave Radio Telescope• Ryle TelescopeRyle Telescope• Combined Array for Millimeter-wave Combined Array for Millimeter-wave

AstronomyAstronomy

New era in radio follow-up New era in radio follow-up observations observations

SquareSquare

KilometeKilometerr

ArrayArray

Broadband spectrumBroadband spectrum

Piran Piran 20032003

Radio observations:Radio observations:• Peak flux & frequencyPeak flux & frequency• Self-absorption frequencySelf-absorption frequency• Non-relativistic evolutionNon-relativistic evolution• Scintillation & image sizeScintillation & image size

Wijers & Galama Wijers & Galama 19991999

Physical parametersPhysical parameters• Electron energy distribution index Electron energy distribution index pp

• Energy in electrons Energy in electrons εεee

• Fraction of emitting electrons ξFraction of emitting electrons ξ

• Energy in magnetic field Energy in magnetic field εεBB

• Blast wave energy Blast wave energy EE

• Density of circumburst medium Density of circumburst medium nn

• Structure of circumburst medium Structure of circumburst medium kk

• Jet opening angle θJet opening angle θ00

• Observing angle θObserving angle θobsobs

GRB 030329GRB 030329

Van der Horst, Kamble et al. Van der Horst, Kamble et al. 20082008

Berger, Kulkarni et al. 2003Berger, Kulkarni et al. 2003

Pihlstrom, Taylor et al. 2007Pihlstrom, Taylor et al. 2007

Current radio afterglow sampleCurrent radio afterglow sample

Chandra & Frail Chandra & Frail 20122012

• 1/3 of observed GRBs 1/3 of observed GRBs detected in radiodetected in radio

• Narrow observed flux rangeNarrow observed flux range

• Sensitivity limitedSensitivity limited

• No clear correlations with No clear correlations with other wave bands (optical?)other wave bands (optical?)

• Detected radio afterglows Detected radio afterglows brighter in prompt brighter in prompt emission, X rays & opticalemission, X rays & optical

• Biased because of strategyBiased because of strategy

Average light curvesAverage light curves

Chandra & Frail Chandra & Frail 20122012• Forward & reverse shockForward & reverse shock• Bright future for 8 GHz and Bright future for 8 GHz and

above (including ALMA)above (including ALMA)• How about low radio How about low radio

frequencies?frequencies?

Radio predictions: p & εRadio predictions: p & εee

Radio predictions: εRadio predictions: εBB & n & n

Radio predictions: E & zRadio predictions: E & z

Radio calorimetryRadio calorimetry

GRB 970508 & GRB 980703 (Berger et GRB 970508 & GRB 980703 (Berger et al. 2004)al. 2004)

• Late-time evolution: no relativistic complicationsLate-time evolution: no relativistic complications• Blast wave spherical? Blast wave spherical? Progenitor constraints Progenitor constraints • Very low frequencies and/or very late times Very low frequencies and/or very late times

GRB 030329 with LOFARGRB 030329 with LOFAR

(Van der Horst, Kamble et al. (Van der Horst, Kamble et al. 2008)2008)

LOFAR: afterglows & prompt emissionLOFAR: afterglows & prompt emission• (Very) late-time afterglows:(Very) late-time afterglows:• Automatic monitoring on various Automatic monitoring on various

timescalestimescales• Complementing the radio afterglow Complementing the radio afterglow

samplesample• Automated response:Automated response:• Triggers by high-energy satellites or Triggers by high-energy satellites or

LOFARLOFAR• New beam formed pointing to GRB New beam formed pointing to GRB

locationlocation

LOFAR: afterglows & prompt emissionLOFAR: afterglows & prompt emission• AARTFAAC: AARTFAAC: Amsterdam-ASTRON Radio Amsterdam-ASTRON Radio

Transients Facility And Analysis CentreTransients Facility And Analysis Centre• 24/7 all-sky monitor with 6 central stations24/7 all-sky monitor with 6 central stations• Piggy-back mode in all LOFAR observationsPiggy-back mode in all LOFAR observations• LBA: whole sky, HBA: 1000 degLBA: whole sky, HBA: 1000 deg22

• Transient Buffer BoardsTransient Buffer Boards• 5 second storage5 second storage• Dispersion delay Dispersion delay subband approach subband approach

• Coming soon: LOFAR UK-Chibolton responding Coming soon: LOFAR UK-Chibolton responding to Swift triggers (1 hour follow-up)to Swift triggers (1 hour follow-up)

Reverse shock – radio flaresReverse shock – radio flares

• Optical flash Optical flash early radio flare early radio flare• Probe GRB ejecta & jet magnetizationProbe GRB ejecta & jet magnetization

Melandri, Kobayashi et al. Melandri, Kobayashi et al. 20102010Kulkarni, Frail et al. 1999Kulkarni, Frail et al. 1999

AMI fast follow-upAMI fast follow-up• Large array at 15 GHzLarge array at 15 GHz• ~0.13 mJy rms in 10 minutes~0.13 mJy rms in 10 minutes• 5.5’ primary beam5.5’ primary beam• ~30’’ synthesised beam~30’’ synthesised beam• First responses within 4-5 minutes!!First responses within 4-5 minutes!!

AMI fast follow-upAMI fast follow-up• Large array at 15 GHzLarge array at 15 GHz• ~0.13 mJy rms in 10 minutes~0.13 mJy rms in 10 minutes• 5.5’ primary beam5.5’ primary beam• ~30’’ synthesised beam~30’’ synthesised beam• First responses within 4-5 minutes!!First responses within 4-5 minutes!!

AMI observations of GRB 120422AAMI observations of GRB 120422A

Staley, Titterington et al., in Staley, Titterington et al., in prep.prep.

Dark burstsDark bursts

Rol, Van der Horst et al. Rol, Van der Horst et al. 20082008

Van der Horst, Kouveliotou et al. Van der Horst, Kouveliotou et al. 20092009

GRB 051022GRB 051022

RadioRadio

X-rayX-ray

• Host galaxyHost galaxy• High redshiftHigh redshift• Intrinsic?Intrinsic?

Compact binary mergersCompact binary mergers

• Sub-relativistic dynamically ejected outflowSub-relativistic dynamically ejected outflow• Detectable up to ~300 Mpc Detectable up to ~300 Mpc LIGO/VIRGO LIGO/VIRGO• Short GRBs(?) Short GRBs(?) relativistic jet relativistic jet

Piran, Nakar & Rosswog Piran, Nakar & Rosswog 20122012

ConclusionsConclusions• Dawn of a new radio era:Dawn of a new radio era:• Many SKA pathfindersMany SKA pathfinders• Upgrades of new facilitiesUpgrades of new facilities• Extensions of the frequency & time domainsExtensions of the frequency & time domains

• Radio observations crucial for pinning down Radio observations crucial for pinning down afterglow physicsafterglow physics

• Current sample sensitivity limitedCurrent sample sensitivity limited

• Probing parameter space of “regular” Probing parameter space of “regular” afterglowsafterglows

• Studies of early reverse shock emission and Studies of early reverse shock emission and possible coherent prompt emissionpossible coherent prompt emission