1. What made GRBs 060505 & 060614? Palli Jakobsson
Johan Fynbo:
Palli Jakobsson
Centre for Astrophysics Research
(University of Hertfordshire)

2. Light Curves • ↓ GRB 060505 (z = 0.09) GRB 060614 (z = 0.13)
Duration ~ 4 s
Duration ~ 100 s • ↓
Ofek et al. (2007)
Fynbo et al. (2006); Della Valle et al. (2006); Gal-Yam et al. (2006)

3. GRB 060505 Host Galaxy Z ~ 14% Solar MB ~ -19.6 mag AV < 0.09 mag
Spec. SFR ~ 4 M○ yr-1 (L/L*)-1
Little extinction
(Balmer decrement)
t = 17 days
SN 1998bw
SN 2002ap
Fynbo et al. (2006); Thöne et al. (2007) + poster (P.05); Ofek et al. (2007)

4. GRB Host Galaxy
MB ~ (tiny – much smaller than host)
Spec. SFR ~ 3 M○ yr-1 (L/L*)-1
Little extinction
(Balmer decrement)
t = 11 days
SN 2002ap

5. Wrong Redshifts (z > 1)?
Schaefer & Xiao (2006); Cobb et al. (2006)
GRB has
-- strong UV detections: z < 1.1
-- no absorption components in OA spectrum,
as expected for low-z, but not for a high-z burst
with a foreground galaxy.
-- no sign of a z ~ 1 in HST images. .
GRB has
-- P < 10-3 of accidentally landing right on top of a
small star-forming region within a spiral galaxy.

6. Is There a Problem (no SN)?
Both hosts are actively star-forming
occurred in a star-forming knot.
No SN: predicted as a variant of the original
collapsar model, e.g. collapse of a massive star
with an explosion energy so small that most of the
56Ni falls back into the BH (e.g. Fryer et al. 2006).
duration of 4 s is near the ~5 s duration
which Donaghy et al. (2006) find as the point of
roughly equal probability of a given burst lying
in either “short”/”long” class.

7. Lag/Luminosity: Short/Long Divide??
Vanderspek et al. (2004)
Gehrels et al. (2006)

8. Classification Problem?
long GRBs (t > 2 s) ≠ massive star death
short GRBs (t < 2 s) ≠ compact object merger
Type I & II GRBs (Zhang et al. 2007)
(ambiguous + not operational, difficult to use)
Type III?? WD/NS merger (King et al. 2007)
Keep an open mind!