EngineDriven Supernovae

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Engine-Driven Supernovae
Alicia M. Soderberg Caltech Astronomy
Dept. Zwicky Supernova Workshop January 17 2004
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Engines in GRBs
Continuous energy input from an accrection disk
(many times the dynamical timescale) produces a
multi-peak lightcurve.
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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)
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SN1998bw an engine-driven SN
Case2 quasi-spherical relativistic
ejecta (unknown )
Case 1 off-axis (0.5 )
observer
observer
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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.

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Type Ibc Radio Lightcurves
(Kulkarni et al., 1998 Weiler et al. 1998)
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Type Ibc Radio Lightcurves
1999-2002 28 limits SN2002ap
(Berger et al. 2002)
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Type Ibc Radio Lightcurves
1999-2002 28 limits SN2002ap
2003-present 23 limits SN2003L
SN/GRB lt 2
(Soderberg et al. in prep.)
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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 v5900 - 12,000 km/s cf SN1998bw v15,000 -
30,000 km/s cf SN2003dh v20,000 - 40,000 km/s
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VLA Radio Observations of SN 2003L
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Preliminary Constraints on the Expansion Velocity
1.) VLBA observations 2003 March 7.30 UT (t
65 days) r lt 1018 cm (0.12 mas), ? lt
2-3 c.f. SN1998bw t30 days r1017 cm
(0.2 mas), vc 2.) Minimum Energy We can
determine the size of the source assuming
equipartition between particles and magnetic
field. t85 days, 2.8 mJy, 8.5 GHz r 2.7
x 1016 cm ltvgt 0.13 c
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Equipartition Results SN2003L ejecta is BRIGHT
but not unusually fast
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Radio Supernova Modelling
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. gt source size/velocity 2.)
Free-Free Absorption (FFA) in the CSM may
produce additional absorption. gt
environment/density
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SN2003L Modeling Results
(Soderberg et al. in prep.)
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Implications
Energy
Radius
Mass Loss
Density
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Compare to SN 1998bw(Li Chevalier 1999)
Energy
Radius
Mass Loss
Density
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SN2003L and Other Cosmic Explosions
SN 2003L
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SN2003bg another energetic SN
2003L 2003bg
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Type Ibc Radio Lightcurves
1999-2002 28 limits SN2002ap
2003-present 23 limits SN2003L SN2003bg
(Kulkarni et al., 1998 Weiler et al. 1998
Berger et al. 2002)
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SN2003bg Multiple Episodes of Energy Input ?
SN2003bg ?Energy3 SN1998bw ?Energy2.6
(Soderberg et al., 2004)
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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 v0.1c and E3x1048 erg (cf. SN1998bw
  ?2 and E1050 erg), as well as n 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.