unifying afterglow diversity gabriele ghisellini inaf-osservatorio astronomico di brera - italy with...
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Unifying afterglow Unifying afterglow diversitydiversity
Gabriele Ghisellini
INAF-Osservatorio Astronomico di Brera - Italy
with the help of G.Ghirlanda and M. Nardini
X-ray and optical X-ray and optical oftenoften behave behave differentlydifferently
~same ~same spectrumspectrum
TTAA
Is this “real” afte
rglow? i.e. e
xternal
Is this “real” afte
rglow? i.e. e
xternal
shock?
shock?
X-ray
What is T
What is T AA
? ?
opticaloptical
2 Component model2 Component model
• Component 1: Standard afterglow. Component 1: Standard afterglow. Standard=forward shocks in the ISM (e.g. Panaitescu & Kumar 2000)
• Component 2: Component 2: Completely phenomenological. Used for the “flat-steep” part of the light curve. Constant SED (minimum # of parameters).
• Both componentsBoth components emit optical and X-rays
X-ray A
fterglow
Optical
Optical
Afterg
low
Afterg
low
Standard afterglow Standard afterglow theory (Panaitescu & theory (Panaitescu & Kumar 2000)Kumar 2000)
Component 2
Component 2
Component 2
Component 2: Component 2: completely completely phenomenological at phenomenological at this stagethis stage
•Good fits for all 33 GRBs in Good fits for all 33 GRBs in the samplethe sample
•What is “component 2”?What is “component 2”?
Lazz
ati
+ 2
008
Lazz
ati
+ 2
008
tt-5/3-5/3
From averaging the luminosity of flares in From averaging the luminosity of flares in different GRBsdifferent GRBs
Zh
an
g W
oosle
y H
eg
er
Zh
an
g W
oosle
y H
eg
er
2008
2008
106105104103
Time [s]
Fallback
lasts
for q
uite a lo
ng
Fallback
lasts
for q
uite a lo
ng
time
time
M f
rom
fa
llb
ack
• Fallback Prolonged activity Fallback Prolonged activity of the central engineof the central engine
•Can we explain TCan we explain TAA??
Early (normal) prompt: Early (normal) prompt: >>1/j
Late prompt: Late prompt: >1/j
Late prompt: Late prompt: =1/j
Late prompt: Late prompt: <1/j
”real” after-glow
Ghisellini et al. Ghisellini et al. 20072007
Strong, Strong, erraticerraticSmoothSmooth
After the early After the early prompt, the central prompt, the central engine decreases engine decreases energy and decreases energy and decreases monotonicallymonotonically
R~10R~101313 cmcm
Early (normal) prompt: Early (normal) prompt: >>1/j
Late prompt: Late prompt: >1/j
Late prompt: Late prompt: =1/j
Late prompt: Late prompt: <1/j
”real” after-glow
Ghisellini et al. Ghisellini et al. 20072007R~10R~101313
cmcm
TTAA
TTjetjet
ConclusionsConclusions
• 2 components can explain the diversity2 components can explain the diversity• Component 2 can be associated with the Component 2 can be associated with the
prolonged activity of the entral engineprolonged activity of the entral engine• Fallback is long Fallback is long late prompt “forever” late prompt “forever”• Flares as accretion of denser chunks of Flares as accretion of denser chunks of
fallback materialfallback material
• TTAA can be explained can be explained
• Next…Next…
NEXT (Marco Nardini):NEXT (Marco Nardini):
•Can we also explain the Can we also explain the presence/absence of jet presence/absence of jet breaks?breaks?
~ t~ t--/2/2tt--22
tt--33
TimTimee
Flu
xFlu
x
MMoutout ~ t ~ t-(-())/2/2
Long lasting engine with two-phase Long lasting engine with two-phase accretion?accretion?1: Very dense torus, large B-field, 1: Very dense torus, large B-field, erratic.erratic.
2: Less dense material, smaller B-2: Less dense material, smaller B-field, smoother accretion – field, smoother accretion – Fallback?Fallback?
TTAA
LLMMoutout ~ t ~ t--
L~ ML~ Maccraccr ? ?
Very Very cheapcheap
• SEDs vs light curvesSEDs vs light curves
TestsTests
Log
Log
FF
Log Log
opticaopticall
X-raysX-rays
• SEDs vs light curvesSEDs vs light curves• Some GRBs with no plateau: Some GRBs with no plateau:
achromatic breaks? achromatic breaks?
TestsTests
• SEDs vs light curvesSEDs vs light curves• Some GRBs with no plateau: Some GRBs with no plateau:
achromatic breaks? achromatic breaks? • Late ‘jump’ in X-ray light-curves Late ‘jump’ in X-ray light-curves
revealing real X-ray afterglowrevealing real X-ray afterglow
TestsTests
TTAA
Jump=end Jump=end of late of late promptprompt
TimeTime
X-r
ay
X-r
ay
Flu
xFlu
x