S R Kulkarni An interlude compactness problem From saris talk circa 2000 Energy We measure F10 6 ergcm 2 Cosmological D 10 28 cm E 4 D 2 F 10 51 erg ID: 511808
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Slide1
Long Duration High Energy Transients
S. R. KulkarniSlide2
An interlude – compactness problemSlide3
From sari’s talk (circa 2000)Slide4
Energy
We measure F~10
-6
erg/cm
2
Cosmological: D ~ 10
28
cm
E =
4
D
2
F ~ 10
51
ergSlide5Slide6
Temporal Variability
dT<1s, T~100
N=T/dT>100Slide7
Implications of short timescale
dt=R/c
R/cSlide8
dT ~ 1ms
R < 3•10
7
cm
E ~ 10
51
ergs
10
57
photons
high photon density
(many above 500 keV).
Optical depth
T
n R~
10
15>>1
Inconsistent with the non thermal spectrum!
COMPACTNESS PROBLEM
g + g
e+ + e
-
Spectrum:
Optically thin
Size & Energy:
Optically thick
? Paradox ?Slide9
A
C
B
D
R
R
R
~1/
Relativistic
Time-Scales
t
B
-t
A
~ R (1-
) / c ~ R/2
2
c
t
C
-t
A
~ R(1-
cos )/c ~ R/2
2
c
t
D
-t
A
~
/cSlide10
Due to Relativistic Motion
R =
g
2
c dT
E
ph
(emitted) = E
ph
(obs) /
g
t
gg
=
g
-(4+2a)
n
s
T
R ~ 10
15
/g
4+2a (Goodman; Paczynski; Krolik & Pier; Fenimore; Woods & Loeb; Piran & Shemi; Lithwick & RS 01)
g
> 100
The Solution:
Relativistic MotionSlide11
Relativistic Motion
(Lithwick & RS 2001)Slide12
References
F. J.
Virigili
et al. 2013 (
ApJ
778)
A. J.
Levan
et al. 2013 (
astroph
)Slide13
GRB091024A
z
=1.09Slide14Slide15Slide16Slide17Slide18
Lorentz Factor -
g
Einstein theory of relativity
g
measures how close to the speed of light an object is moving.
Determines how slowly time evolves
Determines the beaming angle
Examples:
g=3
v=95% c
g=10
v=99.5% c
g=100
v=99.995% c
g=1000 v=99.99995% c
Speed of light
GRBsSlide19
Nuclear sources?Slide20
Need a long lived engine
Collapsar
model: What determines the duration of the engine?
Tidal Disruption Event
Long duration nicely explained
Magnetar
powered?Slide21
Tidal Disruption Flare?Slide22
Movie!Slide23
Grand OverviewSlide24
Observational difficulties
Most GRB missions work on “triggers” – spikes of emission
Such events are best seen in “imaging triggers”
But satellite must be pointed to the same piece of sky for 1000
s
(not the case with Swift)
I wonder how well has the BAT data been analyzed for such objects (or for that matter WFC data)Slide25
Tests
Does the object coincide with the nucleus?
Is there a 1998bw-like supernova associated with the object?
What is the total energy loss? (relative to say 10
52
erg)