ON LATE TIME REBRIGHTENINGS IN GRB OPTICAL AFTERGLOWS
Liverpool GRBs in the Era of Rapid Follow-up 22.06.2012
A. Gomboc (UL, CE SPACE-SI, Slovenia)
withS. Kobayashi (LJMU), A. Pozanenko (IKI), A. Melandri (INAF Brera),J. Japelj (UL), D. Kopač (UL), C. Guidorzi (UF), C. Mundell (LJMU), I. Steele (LJMU), K. Wiersema (UL), O. Hartoog (UA), and more...
Outline
late time rebrightenings in optical afterglows
possible theoretical interpretations
focus: steep rebrightenings
standard model power law decay: forward + reverse shock Mimica's talk yesterday
Gomboc et al. 2009
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F ∝ t−α
reverse shock: steep decay: α ≈ 1.7
Kobayashi 2000
thin shell, slow cooling
thick shell, slow cooling
optical afterglows in Swift era
Kann et al. 2010
major rebrightenings at t>t0+500 s
theoretical interpretations late forward shock passage of inhomogeneous circum-burst medium (density
bumps) (e.g., Lazzati et al. 2002, Mimica's talk) multi-component jet (e.g., Granot et al. 2006; Racusin
et al. 2008) varying micro-physical parameters (e.g., Kong et
al. 2010) late time engine activity, refreshed shocks (e.g.,
Vlasis et al. 2011)
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νbreak
GRB 970508
Pedersen et al. 1998, Galama et al. 1998
αrise≈-3 αdecay≈1.2
refreshed shock(Panaitescu et al. 1998,Sari&Mészáros 2000,Kumar&Piran 2000) density jump(Wang&Loeb 2000, Dai&Lu 2002, Nakar et al 2003) patchy shell (Nakar et al. 2003)
GRB 050408 energy
injection (at 2.9 days) seen off-axis
de Ugarte Postigo et al. 2007
GRB 060210 αrise≈ -0.9 αdecay≈1.15
density bump? (fine tuning)
Curran et al. 2007
GRB 060614 αrise
depends on λ
colour evolution
passage of break frequency
or Mangano et al. 2007
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ν i
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νc
GRB 070311
refreshed shock density bump (less likely)
Guidorzi et al. 2007
GRB 070419A αrise≈-1.5 αdecay≈0.6,1.5,
0.4
long-lived central engine with a finely tuned energy injection rate
Melandri et al. 2009
GRB 071003 late-time refreshed shockor wide-angle secondary jet
Perley et al. 2008
GRB 071010A
energy injection or density bump, structured jetCovino et al. 2008
GRB 071031 onset of the forward shockemission + some bumps (also in X-rays) common origin: late central engine activity
Krühler et al. 2008
GRB 080129 optical flare (RS) rebrightening: αrise≈-1.3 αdecay≈0.5
emerging afterglowGreiner et al. 2009
GRB 091024Francisco Virgili's talk
Virgili et al., in prep.
GRB 100418A similar to 060614
long-lasting energyinjection two component jet
Lan-Wei et al. 2012Marshall et al. 2011
GRB 060206, 081029, 100901A
GRB 060206 αrise≈ -8 αdecay≈ 1
late energy injection
Monfardini et al. 2006
variation of microphysics Kong et al.
2010:region 1:
region 2:Kong et al. 2010 €
εe = ε e,0γ−α1
ε B = εB ,0γ−α1
€
εe = ε e,0γ−α 2
εB = ε B ,0γ−α 2
variation of microphysics Kong et al. 2010
GRB 060206 – cont. variation of microphysics:
Kong et al. 2010
GRB 081029 αrise≈ -8 αdecay≈ 0.4, 2.5
no simultaneousrebrightening in X-rays
SED: SPL opt/NIR –XNardini et al. 2011
GRB 081029 – cont. seen in 7 bands
Nardini et al. 2011
GRB 081029 – cont. colour evolution
Nardini et al. 2011:long lasting activity/reactivation of central engine
Holland et al. 2012:two component jet and two shell collision
Nardini et al. 2011
collision of two shells Vlasis et al. 2011
GRB 100901A afterglow onset αrise≈ -3.9, -0.5 αdecay≈ 1.5
rebrightening in X-ray (not as steep) SED: BPL opt-X no obvious colour evolution Gomboc et al. in prep.
GRB 100901A – cont. variation of microphysics
late time energy injection/two shell collision
detail modeling of multi-wavelength afterglow behaviour
GRB 100621 αrise≈ -14 (!)
challenge?
Nardini, Munich conf., 2012
Conclusions late time optical (NIR) rebrightenings diverse (some) chromatic steep rise: difficult to explain
Thank you!
