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

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

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

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

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 : “piggyback” project with GRBs. Sep 2002-present: First systematic survey: we observe every type Ib/c within 100 Mpc accessible with the VLA.

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

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

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

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

VLA Radio Observations of SN 2003L

Preliminary Constraints on the Expansion Velocity 1.) VLBA observations: 2003 March 7.30 UT (t = 65 days) r < 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 cm = 0.13 c

Equipartition Results: SN2003L ejecta is BRIGHT but not unusually fast

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

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

Implications: Energy Density Radius Mass Loss

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

SN2003L and Other Cosmic Explosions: SN 2003L

SN2003bg – another energetic SN 2003L & 2003bg

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

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

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 M o /yr (cf. SN1998bw: 3 x 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.