Unifying afterglow diversity Gabriele Ghisellini INAF-Osservatorio Astronomico di Brera - Italy with the help of G.Ghirlanda and M. Nardini.

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-rayoptical

optical

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

flat

steep

SuSum

m

Sum

X-ray

opticaloptical

Optical

Optical Afterglow

Afterglow

X-ray Afterglow

Component 2

Component 2

Component 2

flat steep

Sum

SuSum m

•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”?

~5/~5/33

Decay index of steep part of Decay index of steep part of comp 2comp 2

steepsteep

~70 Swift GRBs ~70 Swift GRBs with zwith z

X-raysX-rays

tt-5/3-5/3

tt-5/4-5/4

Gh

isellin

i+

Gh

isellin

i+

2009

2009

Comp Comp 22

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

MacFad

yen

+ 2

001

MacFad

yen

+ 2

001

tt-5/3-5/3M

fro

m f

allb

ack

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-(-())/2/2TTAA

LLMMoutout ~ t ~ t--

~ 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