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