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Circumstellar interaction of Circumstellar interaction of
supernovae and gamma-ray burstssupernovae and gamma-ray bursts
Circumstellar interaction of Circumstellar interaction of
supernovae and gamma-ray burstssupernovae and gamma-ray bursts
Poonam Chandra
National Radio Astronomy Observatory
&
University of Virginia
Calcium in our bones
Oxygen we breathe
Iron in our cars
Supernovae
SUPERNOVA
Death of a massive star
Violent explosions in the universe
Energy emitted (EM+KE) ~ 1051 ergs. (To realise hugeness of the energy, the energy emitted in the atmospheric nuclear explosion is ~ 1 MT ≈ 4x1022 ergs.)
SUPERNOVAE
Thermonuclear Supernovae
Core Collapse
Supernovae
Core collapse Supernovae•Type II, Ib, Ic
•Neutron star or Black hole remains
•More massive progenitor (> 8 MSolar)
•Found only in Spiral arms of the galaxy (Young population of stars)
Thermonuclear Supernovae•Type Ia
•No remnant remaining
•Less massive progenitor (4-8 MSolar)
•Found in elliptical and Spiral galaxies
Two kinds of supernova explosions
Chemical explosives ~10-6 MeV/atom
Nuclear explosives ~ 1MeV/nucleon
Novae explosions few MeV/nucleon
Thermonuclear explosions few MeV/nucleon
Core collapse supernovae 100 MeV/nucleon
Energy scales in various explosions
Classification
H (Type II) No H (Type I)
Si (Type Ia) No Si (6150Ao)
He (Type Ib) No He (Type Ic)
(Various types-IIn, IIP, IIL, IIb etc.)
Based on optical spectra
Crab Tycho
Cas AKepler
SN explosion centre
Photosphere
Outgoing ejecta
Reverse shock shell
Contact discontinuity
Forward shock shell
Radius
Den
sity
Circumstellar matter
Not to scaleNot to scale
Shock Formation in SNe:
Blast wave shock : Ejecta expansion speed is much higher than sound speed.
Shocked CSM: Interaction of blast wave with CSM . CSM is accelerated, compressed, heated and shocked.
Reverse Shock Formation: Due to deceleration of shocked ejecta around contact discontinuity as shocked CSM pushes back on the ejecta.
Chevalier & Fransson, astro-ph/0110060 (2001)
Circumstellar InteractionCircumstellar Interaction
Shock velocity of typical SNe are ~1000 times the velocity of the (red supergiant) wind. Hence, SNe observed few years after explosion can probe the history of the progenitor star thousands of years back.
• Radio emission from Supernovae: Synchrotron non-thermal emission of relativistic electrons in the presence of high magnetic field.
• X-ray emission from Supernovae: Both thermal and non-thermal emission from the region lying between optical and radio photospheres.
Interaction of SN ejecta with CSM gives rise to radio and X-ray emission
X-ray emission from supernovae
Thermal X-rays
versus
Non-thermal X-rays
X-rays from the shocked shell
Inverse Compton scattering (non-thermal)
X-rays from the clumps in the CSM (thermal)
Swift
XMM
SPA
CE T
ELE
SC
OPES
RADIO TELESCOPES
Radio Emission in a Supernova
Radio emission in a supernova arises due to synchrotron emission, which arises by the
ACCELERATION OF ELECTRONS
in presence of an
ENHANCED MAGNETIC FIELD.
?
?
Date of Explosion : 28 March 1993
Type : IIb
Parent Galaxy :M81
Distance : 3.63 Mpc
SN 1993JSN 1993J
Giant Meterwave Radio Telescope
235 MHz map of FOV of SN1993J235 MHz map of FOV of SN1993J
1993J
M81
M82
Observations of SN 1993J at meter and shorter wavelengths
Date of observation
Frequency GHz
Flux density mJy
Rms mJy
Dec 31, 01 0.239 57.8 ± 7.6 2.5
Dec 30, 01 0.619 47.8 ± 5.5 1.9
Oct 15, 01 1.396 33.9 ± 3.5 0.3
Jan 13, 02 1.465 31.4 ± 4.28 2.9
Jan 13, 02 4.885 15.0 ± 0.77 0.19
Jan 13, 02 8.44 7.88 ± 0.46 0.24
Jan 13, 02 14.97 4.49 ± 0.48 0.34
Jan 13, 02 22.49 2.50 ± 0.28 0.13
VL
AG
MR
T
Frequency (GHz)
Flu
x d
ensi
ty (
mJy
)
GMRT
VLA
Composite radio spectrum on day 3200
= 0.6
Synchrotron AgingSynchrotron Aging
Due to the efficient synchrotron radiation, the electrons, in a
magnetic field, with high energies are depleted.
Due to the efficient synchrotron radiation, the electrons, in a
magnetic field, with high energies are depleted.
tbBE offcut 2
1
bN
(E)
E
N(E)=kE-
.
Q(E)E-
steepening of spectral index from =(-1)/2 to /2 i.e. by 0.5
.
253
sin4
3EB
cm
e
22274
4
sin3
2EB
cm
e
dt
dE
Sync
Frequency (GHz)
Flu
x d
ensi
ty (
mJy
)
GMRT
VLA
break =4 GHz
R= 1.8x1017cm B= 38±17 mG
= 0.6
Composite radio spectrum on day 3200
2= 7.3 per 5 d.o.f.
2= 0.1 per 3 d.o.f.
Synchrotron Aging in SN 1993J
Synchrotron losses
Adiabatic expansion
Diffusive Fermi acceleration
Energy losses due to adiabatic expansionEnergy losses due to adiabatic expansion
t
EE
R
V
dt
dE
Adia
V
Ejecta velocity
Size of the SN
R
v3
)vv(4 21
21 v
1
v
1
v
4ct
1v2v
Upstream velocity
Downstream velocity
Spatial diffusion coefficient of the test particles across ambient magnetic field
Particle velocity
20
)/(
20
22 tREEV
t
E
dt
dE
cFermi
v
Energy gain due to diffusive Fermi acceleration Energy gain due to diffusive Fermi acceleration
EtEbBEtR
E
dtdE
E
Total12222 )20/(/
t tBB /0For and
Break frequency Break frequency
.
.
.
.
2
2/12/12
30 2
20
ttR
Bbreak
(Fransson & Bjornsson, 1998, ApJ, 509, 861)
Magnetic field independent of equipartition assumption & taking into account adiabatic
energy losses and diffusive Fermi acceleration energy gain
Magnetic field independent of equipartition assumption & taking into account adiabatic
energy losses and diffusive Fermi acceleration energy gain
B=330 mG
.
464
)132(
100.5105.8
BU
U
mag
rel
(Chevalier, 1998, ApJ, 499, 810)
ISM magnetic field is few microGauss. Shock wave will compress magnetic field at most by a factor of 4, still few 10s of
microGauss. Hence magnetic field inside the forward shock is highly enhanced,
most probably due to instabilities
Equipartition magnetic field is 10 times smaller than actual B, hence magnetic energy density is 4 order of magnitude higher than relativistic energy density
They were discovered serendipitously in the late 1960s by U.S. military
satellites which were on the look out for Soviet nuclear testing in violation of
the atmospheric nuclear test ban treaty. These satellites carried gamma ray detectors since a nuclear explosion
produces gamma rays.
Gamma-ray burst
Gamma-Ray Burst
How explosive???
Even 100 times brighter than a
supernovaMillion trillion
times as bright as sun
Brightest source of Cosmic
Gamma Ray Photons
Long-duration bursts:Last more than 2 seconds. Range anywhere from 2 seconds to a few hundreds of seconds (several minutes) with an average duration time of about 30 seconds.
Short-duration bursts:
Last less than 2 seconds. Range from a few milliseconds to 2 seconds with an average duration time of about 0.3 seconds (300 milliseconds).
Gamma-ray bursts
In universe, roughly 1 GRB is detected
everyday.
GRB Missions
BATSE BeppoSAX
Sw
ift was la
un
ched
in
20
04
Often followed by "afterglow" emission at longer wavelengths (X-ray, UV, optical, IR, and radio).
GRB interaction with the surrounding medium
GRB properties
Afterglows made study possible and know about GRB
GRB are extragalactic explosions.
Associated with supernovae
They are collimated.
They involve formation of black hole at the center.
If collimated, occur much more frequently.
GRB 070125
Brightest Radio GRB in Swift era.
Detected by IPN network.
Followed by all the telescopes in all wavebands in the world.
Detection in Gamma, X-ray, UV, Optical, Infra-red and radio.
Jet break around day 4.
Still continuing radio observations.
GRB 070125
THANKS!!!THANKS!!!!!
First order Fermi acceleration
V1 VsV2
Boltzmann Equation in the presence of continuous injection
Boltzmann Equation in the presence of continuous injection
qENdt
dE
Et
N
total
)1/(),( )1(
EEtEN
break
breakEEEE
Form of synchrotron spectral distribution
2/
2/)1(
I
break
break
Kardashev, 1962, Sov. Astr. 6, 317
Self-similar solutions
Equations of conservations in Lagrangian co-ordinates for the spherically symmetric adiabatic gas dynamics are
22
3
4
1
3
4
r
GM
M
Pr
t
v
rM
vt
r
To find similarity solution, we substitute velocity, density and pressure into the spherically symmetric adiabatic gas dynamics equations
m
mmn
mn
mn
m
At
r
tA
b
t
rt
A
bP
GtA
b
Ut
AUt
rv
)()(
)(
)()(
2)1(2222
22
2
1
where
This reduces the partial differential equations to
21
2001
1
2
3
)(
)()(
02)1()1(2)('
))(1('
0)1(2')(''
023''
n
a
bGA
n
nm
G
mUmUmUG
G
UUmUUG
G
mUUmUG
G
where
and
Hugoniot conditions
20
0
2
2
)1(
)1(
1
2
)1(
)1(2)1(
1
21
1
1
mU
m
mU
G
i
i
i