What made GRBs 060505 & 060614?
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Transcript of What made GRBs 060505 & 060614?
What made GRBs 060505 & 060614?
Palli JakobssonCentre for Astrophysics Research
(University of Hertfordshire)
Johan Fynbo: [email protected]
Light CurvesGRB 060505 (z = 0.09) GRB 060614 (z = 0.13)
Fynbo et al. (2006); Della Valle et al. (2006); Gal-Yam et al. (2006)
Duration ~ 4 s Duration ~ 100 s
•↓Ofek et al. (2007)
GRB 060505 Host Galaxy
Fynbo et al. (2006); Thöne et al. (2007) + poster (P.05); Ofek et al. (2007)
MB ~ -19.6 mag
Spec. SFR ~ 4 M○ yr-1 (L/L*)-1
Little extinction (Balmer decrement)SN 2002apSN 1998bwt = 17 days
Z ~ 14% Solar
AV < 0.09 mag
GRB 060614 Host Galaxy
t = 11 days SN 2002ap
MB ~ -15.3 (tiny – much smaller than 060505 host)
Spec. SFR ~ 3 M○ yr-1 (L/L*)-1
Little extinction (Balmer decrement)
Wrong Redshifts (z > 1)?
• GRB 060614 has
• GRB 060505 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 host @ z ~ 1 in HST images.
-- P < 10-3 of accidentally landing right on top of a small star-forming region within a spiral galaxy.
Schaefer & Xiao (2006); Cobb et al. (2006)
Is There a Problem (no SN)?
• Both hosts are actively star-forming. 060505 occurred in a star-forming knot.
• 060505 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.
• 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).
Lag/Luminosity: Short/Long Divide
Gehrels et al. (2006)
Vanderspek et al. (2004)??
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!