Engine-Driven Supernovae

Engine-Driven Supernovae

Alicia M. SoderbergCaltech Astronomy Dept.

Zwicky Supernova WorkshopJanuary 17 2004

Engines in GRBs

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

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 requiresrelativistic 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

observer observer

The Caltech/NRAO Radio Supernova Survey

Purpose: to determine the association between type Ib/c supernovae and GRBs through evidencefor 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.

(Kulkarni et al., 1998; Weiler et al. 1998)

Type Ibc RadioLightcurves

(Berger et al. 2002)

Type Ibc RadioLightcurves

1999-2002:28 limits& SN2002ap

(Soderberg et al. in prep.)

Type Ibc RadioLightcurves

1999-2002:28 limits& SN2002ap

2003-present:23 limits& SN2003L

SN/GRB < 2%

Type Ic SN 2003L in NGC 3506

Optical Discovery: Jan 12 2003(Boles, IAUC 8048)MV = -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/scf: SN1998bw: v~15,000 - 30,000 km/scf: SN2003dh: v~20,000 - 40,000 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 < 1018 cm (0.12 mas), Г < 2-3

c.f.: SN1998bw: t~30 daysr~1017 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 1016 cm<v> = 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 CSMmay 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 2

003L

SN2003bg – another energetic SN

2003

L &

200

3bg

(Kulkarni et al., 1998; Weiler et al. 1998; Berger et al. 2002)

Type Ibc RadioLightcurves

1999-2002:28 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~3x1048 erg (cf. SN1998bw: ~2 and E~1050 erg), as well asn ~ r -2 and (dM/dt) ~2 x 10-7 Mo/yr (cf. SN1998bw: 3 x 10-7 Mo/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.