1. 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

2. The first gamma ray-burst
Vela satellite

3. 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

5. 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

6. 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.

7. The Gamma Ray Burst on March 29, 2003

8. The
Optical
Transient (OT)

9. OT Fades

10. VLA Observations
1.4 to 43 GHz
and OVRO 100 GHz

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

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

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

14. 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)

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

16. model = 0 mas model = 0.1 mas model = 0.2 mas

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

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

19. 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

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

21. Broad-band Synchrotron Spectrum