1. RADIO EMISSION FROM SNe & GRBs, AND THE NEED FOR SKA
Kurt W. Weiler (NRL)
Collaborators: Schuyler D. Van Dyk (IPAC/Caltech) Christina K. Lacey (NRC/NRL) Nino Panagia (STScI/ESA)
Richard A. Sramek (NRAO/VLA) Marcos Montes (NRL)

2. Supernovae (SNe) Play a vital role in galactic evolution:
Nucleosynthesis, chemical enrichment, energy input into ISM
production of stellar remnants, production of cosmic rays
A primary goal of SN research:
Understanding progenitor stars and explosion mechanisms for different SNe types
SNe types: Ia, Ib/c, II (also IIn, IIb)
SNe Ia not radio sources to limit of VLA sensitivity

3. Radio Supernovae (RSNe)
27 RSNe detected by in the radio; 17 objects extensively studied
Analysis of radio emission provides vital insight into SN shock/CSM interaction
Nature of pre-SN evolution
Nature of the progenitor
All RSNe have in common:
Nonthermal synchrotron with high TB
Decrease in (l - dependent) absorption with time
Power­law flux density decline after max
Final approach to optically, thin constant a

4. Radio Supernovae (RSNe)
Interesting variations:
Clumpiness in CSM; variations in Mdot; early time synchrotron self-absorption

5. “Standard” Light Curves
Type Ib/c
Type II

6. CSM Sampling ‘

7. More Recent Examples
SN1994I (Ic)
SN1993J (II)

8. SN1993J VLBI
Expansion of SN 1993J from age 5 months to age 31 months

9. SN1987A -- Radio

10. SN1987A -- Optical

11. SN1979C -- Radio

12. SN1980K -- Radio

13. Luminosity vs. Time to 6 cm Peak

14. Evolution of RSNe into SNRs

15. SUMMARY (1 of 2)
SNe classes are distinct in radio emission properties (thus distinct in CSM environments):
SNe Ia are undetectable at VLA’s limiting sensitivity
SNe Ib/c turn on and off quickly
SNe II show a wide range of properties
RSNe are sensitive to Mdot/wwind (~ pre-SN mass loss rate)
RSNe sample the CSM => properties of the pre-SN wind density & structure -- unique stellar evolution probe

16. SUMMARY (2 of 2) Now, what about 1998bw and GRBs?
SN 1978K shows evidence for a (possibly associated) HII region along the line of sight.
SN 1979C & SN 1980K show evidence for very rapid stellar evolution in the presupernova phase
SN 1993J shows evidence for a change in mass loss rate in the last ~10,000 years before explosion
RSNe may be distance indicators
Now, what about 1998bw and GRBs?

18. SN 1998bw Radio Light Curves

19. GRB Early

20. GRB Late

21. GRB

22. Radio Observations of GRBs
If present, radio observations of the GRB afterglow can yield:
Size and expansion velocity of the fireball
Through IS scattering
Through changing spectral shape with time
Density & structure of the CSM
As for RSNe
VLBI observations
confirming size & shape
Providing lower distance limits

23. Schematic of Fireball + Relativistic Blast Wave

24. RSN Luminosity at Peak

25. GRB Radio Luminosity at Peak

26. The Sensitivity Problem

27. Conclusions SKA could:
Current VLA is severely sensitivity limited for SN studies
Can only detect SNe with mvmax ~ (out to ~Virgo cluster)
~1300 SNe known; ~ 25 radio detections
~150 new discoveries/year; only 1-2 radio detections
No Type Ia SN ever detected
No VLA on­line mapping precludes RSN searches
SKA could:
Extend RSN detections to mvmax ~ 19
~50 radio detections/year
Discover ``hidden'' SNe
Improve SN statistics not limited by absorption/dust
Improve knowledge of Type Ia progenitors
Provide a new cosmological distance probe

28. Conclusions SKA could:
Current VLA is severely sensitivity limited for GRB studies
Can only detect a few GRBs
Thousands of GRBs known; ~ dozen radio detections
>300 new discoveries/year; only 1-2 radio detections
Not enough radio to distinguish types (fast-hard, slow-soft)
SKA could:
Extend GRB searches
tens of detections/year
Establish GRB CSM properties
(Possibly) distinguish GRB classes
Increase knowledge of relativistic jet/fireball physics

29. Recommendations One would like to see:
Sensitivity of 1 mJy (preferably 0.1 Jy) in 30 minutes
Resolution 1.4 GHz 327 MHz)
Simultaneous, multi­frequency observations
Real­time, on­line editing, calibration & snapshot mapping
Near circular snapshot beam

30. FINISH