22 nd february 2007 poonam chandra unusual behavior in radio supernovae poonam chandra jansky...

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22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department , University of Virginia

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Page 1: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Unusual Behavior in Radio Supernovae

Poonam Chandra

Jansky Fellow, National Radio Astronomy Observatory

Astronomy Department , University of Virginia

Page 2: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

SN 1993J

Unusually well understood

Page 3: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

SN 1993J: Why so special???

• Exploded just 3 Mpc away, extremely bright

• First clear case of transition between supernova Type IIP to Ib.

• Was detected in X-rays and Radio bands just 5 days after the explosion.

• Maund et al (2004) detected unambiguously the signature of the massive binary companion in HST observations, 10 years after the explosion.

• Excellent VLBI measurements, Radio emitting zone resolved.

Page 4: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Still lot more to learn from SN

1993J

My talk is based on the new surprises, it is offering to us

Page 5: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Radio Emission in a Supernova

Radio emission in a supernova arises due to synchrotron emission, which arises by the

ACCELERATION OF ELECTRONSACCELERATION OF ELECTRONS

in presence of an

ENHANCED MAGNETIC FIELDENHANCED MAGNETIC FIELD.

?

?

Page 6: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Radio data:

We found synchrotron cooling break in combined GMRT and VLA (0.2 GHz to 44 GHz) near simultaneous observations on day 3200.

Page 7: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

On Day 3200…… GMRT+VLA spectrum

GMRT

VLA

Synchrotron cooling break at

4 GHz

Chandra, P. et al. 2004

Page 8: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Is synchrotron cooling break real?

Unsettled Issue!!!

Page 9: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Observations of SN 1993J on Day 3770

Date of observation

Frequency GHz Flux density mJy

June 17, 03 0.239 58.2 ± 11.0

June 17, 03 0.619 33.4± 4.3

June 13, 03 1.280 20.2± 2.1

June 26, 03 4.885 8.35 ± 0.42

June 26, 03 14.940 0.98 ± 0.32

June 26, 03 22.485 0.82 ± 0.27

But on day 3770…………..

GM

RT

VLA

Page 10: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

1.5 years later…………. ~Day 3750

Synchrotron cooling break at

~5.5 GHz

GMRT

VLA

Page 11: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

We predicted the evolution of break frequency with roughly 1.2

GHz per year. Our shift in the synchrotron cooling frequency is consistent with this calculation.

(PC, Ray, Bhatnagar, 2004)

Page 12: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

F=

Frequency

Flu

x Den

sity

1= 2= 3

1

23

1< 2< 3

2

3

1

Page 13: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

On Day 3200…… GMRT+VLA spectrum

GMRT

VLA

Chandra, P. et al. 2004

Page 14: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

1.5 years later…………. ~Day 3750

GMRT

VLA

Page 15: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

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

Page 16: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

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

Page 17: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

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)

Page 18: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

On day 3200

B=330 mG

On day 3770

B=280 mG

Magnetic Field follows 1/t decline trend

Page 19: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

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

Page 20: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

.

.

.

.

2

2/12/12

30 2

20

ttR

Bbreak

Acceleration diffusion constant

Ball & Kirk 1992

Page 21: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

For SN 1987A 24102 cm2 sec-1

2424 1096.21027.2

4 cm2 sec-1

Scaled value of diffusion coefficient for 1993J

(Ball & Kirk, 1992, ApJL)

Page 22: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

2/12/32

2/12/12

30 2

202

20tt

Rtt

RB

dt

d break

From VLBI (Bartel, 2002, ApJ),

on day 3200

R=2.65 x 1017 cm

On day 3770

R=3.8 x 1017 cm

break(3200)=4 GHz

break(3770)=5.5 GHz

Page 23: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Diffusion acceleration coefficient

=(5.3 +/- 3.0) x 1024 cm2 s-1

Page 24: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

First time direct measurement of

ENHANCED MAGNETIC FIELD

and

ACCELERATION DIFFUSION COEFFICIENT

responsible for radio emission

by observing the synchrotron cooling break and its evolution with time

Result:

Page 25: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Radio Emission in a Supernova

Radio emission in a supernova arises due to synchrotron emission, which arises by the

ACCELERATION OF ELECTRONSACCELERATION OF ELECTRONS

in presence of an

ENHANCED MAGNETIC FIELDENHANCED MAGNETIC FIELD.

Take it with caution!!!!Take it with caution!!!!

We need at least 4-5 simultaneous We need at least 4-5 simultaneous datasets showing the synchrotron datasets showing the synchrotron

cooling break to feel more cooling break to feel more confident!!!confident!!!

Page 26: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Thanks to:

Kurt Weiler: NRL, Washington

Chris Stockdale: Marquette Univ.

Alak Ray: TIFR, Mumbai, India

Roger Chevalier: Univ Virginia

Juan Uson: NRAO, Charlottesville

Page 27: 22 nd February 2007 Poonam Chandra Unusual Behavior in Radio Supernovae Poonam Chandra Jansky Fellow, National Radio Astronomy Observatory Astronomy Department,

22nd February 2007 Poonam Chandra

Thanks