The Radio Afterglow of GRB 030329 Greg Taylor, Dale Frail (NRAO) Edo Berger, Shri Kulkarni (Caltech) Future Directions in VLBI, A Celebration of the 10th Anniversary of the VLBA – Socorro, June 9, 2003

The first gamma ray-burst Vela satellite

Frail, Waxman & Kulkarni (2000) Fireball Calorimetry Frail, Waxman & Kulkarni (2000) Long-lived radio afterglow makes a transition to NR expansion no geometric uncertainties can employ robust Sedov formulation for dynamics compare with equipartition radius and cross check with ISS-derived radius At z = 0.835

The Fireball Model Model Predictions The Cannonball Model for burst at z=0.2 Size=0.05 to 0.1 mas No proper motion The Cannonball Model Cannot be resolved Motion=0.05 mas/day

GRB 030329: The Burst of the Decade World-wide armada of optical telescopes (~60) observed this burst 24/7 A very bright burst (mv=12.5). In radio it is 50 times brighter than any previous GRB! Better yet at z=0.168 it is only 740 Mpc away.

The Gamma Ray Burst on March 29, 2003

The Optical Transient (OT)

OT Fades

VLA Observations 1.4 to 43 GHz and OVRO 100 GHz

VLA Light Curves (Berger et al 2003, submitted) 1 10 20 days 10 mJy 50 mJy VLBI Epochs

VLBA on April 1 (t+2.4 days) A Scintillating Result

April 1 April 6 5 GHz data not yet reduced Modest Scintillation Scintillation quenching

Testing the Cannonball Model • Phase reference VLBI gives accurate absolute positions (0.1 - 0.3 mas ) – dominated by systematics – can be improved • Already sufficient to rule out predictions of cannonball model (motion shown by arrow)

Resolving the Afterglow 3rd Epoch – April 22 VLBA + EB Beam is 0.45 x 0.15 mas Estimated size is 0.1 +/- 0.05 mas Consistent with standard model size of 0.07 mas average expansion velocity of 8c

model = 0 mas model = 0.1 mas model = 0.2 mas

Resolving the Afterglow 4th Epoch – May 19 VLBA+EB+GBT+Y27 Beam is 0.67 x 0.24 mas Jet component at 0.28 +/- 0.05 mas Not consistent with standard model prediction of 0.12 mas expansion average expansion velocity of 19c

Summary GRB Afterglows Scintillate Expand Have jets? Cannonball model is ruled out by current limits on proper motion

The Details – Four Epochs US VLBA 10 antennas April 01, 2003 5 & 8 GHz April 06, 2003 5, 8, 15 & 22 GHz US VLBA + Bonn 100-m April 22, 2003 15 & 22 GHz VLBA+Bonn+ GBT+VLA May 19, 2003

Jet Signatures: Optical/X-ray Piran, Science, 08 Feb 2002

Broad-band Synchrotron Spectrum