1. Engine-Driven Supernovae Alicia M. Soderberg Caltech Astronomy Dept. Zwicky Supernova Workshop January 17 2004

2. Engines in GRBs Continuous energy input from an accrection disk (many times the dynamical timescale) produces a multi-peak lightcurve.

3. SN1998bw and GRB980425 April 25.91 1998 SN 1998bw is discovered within the error box of GRB 980425. ● SN is highly energetic ● GRB is sub-energetic ● Radio emission requires relativistic ejecta and variable energy input. (Kulkarni et al. 1998; Li & Chevalier 1999)

4. SN1998bw – an engine-driven SN Case 1: off-axis (0.5 %) Case2 : quasi-spherical relativistic ejecta (unknown %) observer

5. The Caltech/NRAO Radio Supernova Survey Purpose: to determine the association between type Ib/c supernovae and GRBs through evidence for relativistic ejecta as a proxy for a central engine. Also: to study the diversity of energetics of type Ib/c SNe. Why Radio Observations? i. Radio probes the fastest ejecta within the SN. ii. Radio is less sensitive to geometrical effects. 1999-2002: “piggyback” project with GRBs. Sep 2002-present: First systematic survey: we observe every type Ib/c within 100 Mpc accessible with the VLA.

6. (Kulkarni et al., 1998; Weiler et al. 1998) Type Ibc Radio Lightcurves

7. (Berger et al. 2002) Type Ibc Radio Lightcurves 1999-2002: 28 limits & SN2002ap

8. (Soderberg et al. in prep.) Type Ibc Radio Lightcurves 1999-2002: 28 limits & SN2002ap 2003-present: 23 limits & SN2003L SN/GRB < 2%

9. Type Ic SN 2003L in NGC 3506 Optical Discovery: Jan 12 2003 (Boles, IAUC 8048) M V = -18.8 (before maximum) d = 92 Mpc Spectroscopic ID: Jan 25, 2003 (Valenti et al. IAUC 8057; Matheson et al. GCN 1846) normal Ic; v~5900 - 12,000 km/s cf: SN1998bw: v~15,000 - 30,000 km/s cf: SN2003dh: v~20,000 - 40,000 km/s

10. VLA Radio Observations of SN 2003L

11. Preliminary Constraints on the Expansion Velocity 1.) VLBA observations: 2003 March 7.30 UT (t = 65 days) r < 10 18 cm (0.12 mas), Г < 2-3 c.f.: SN1998bw: t~30 days r~10 17 cm (0.2 mas), v~c 2.) Minimum Energy: We can determine the size of the source assuming equipartition between particles and magnetic field. t~85 days, 2.8 mJy, 8.5 GHz r = 2.7 x 10 16 cm = 0.13 c

12. Equipartition Results: SN2003L ejecta is BRIGHT but not unusually fast

13. Emission: Synchrotron Radiation from particles swept up by the ejecta (FS). Electrons are accelerated to a power-law distribution described by: N(E) ~ E -p Absorption: 1.) Synchrotron Self-Absorption (SSA) at low frequencies produces a turn-over in the spectrum. => source size/velocity 2.) Free-Free Absorption (FFA) in the CSM may produce additional absorption. => environment/density Radio Supernova Modelling

14. SN2003L Modeling Results (Soderberg et al. in prep.)

15. Implications: Energy Density Radius Mass Loss

16. Compare to SN 1998bw: (Li & Chevalier 1999) Energy Density Radius Mass Loss

17. SN2003L and Other Cosmic Explosions: SN 2003L

18. SN2003bg – another energetic SN 2003L & 2003bg

19. (Kulkarni et al., 1998; Weiler et al. 1998; Berger et al. 2002) Type Ibc Radio Lightcurves 1999-2002: 28 limits & SN2002ap 2003-present: 23 limits & SN2003L & SN2003bg

20. SN2003bg – Multiple Episodes of Energy Input ? SN2003bg:  Energy~3 SN1998bw:  Energy=2.6 (Soderberg et al., 2004)

21. Conclusions ● We are continuing our radio survey to assess the fraction of type Ib/c supernovae powered by an engine (stay tuned). ● We detected strong radio emission from SN2003L & SN2003bg with peak luminosity ~30% that of SN1998bw. ● Analysis of the SN 2003L radio emission indicates v~0.1c and E~3x10 48 erg (cf. SN1998bw:  ~2 and E~10 50 erg), as well as  n ~ r -2  and (dM/dt) ~2 x 10 -7 M o /yr (cf. SN1998bw: 3 x 10 -7 M o /yr). ● With the exception of SN1998bw, SN2003L is the most energetic radio supernova detected to date, but there is no clear evidence for a central engine. ● Analysis of the multi-frequency observations (X-ray, optical) will help us to better constrain the total energetics, etc.