Circumstellar interaction of supernovae and gamma-ray bursts Circumstellar interaction of supernovae 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) ~ ergs. (To realise hugeness of the energy, the energy emitted in the atmospheric nuclear explosion is ~ 1 MT ≈ 4x10 22 ergs.)

SUPERNOVAE

Thermonuclear Supernovae

Core Collapse Supernovae

Core collapse Supernovae Type II, Ib, Ic Neutron star or Black hole remains More massive progenitor (> 8 M Solar ) Found only in Spiral arms of the galaxy (Young population of stars) Thermonuclear Supernovae Type Ia No remnant remaining Less massive progenitor (4-8 M Solar ) Found in elliptical and Spiral galaxies Two kinds of supernova explosions

Chemical explosives~10 -6 MeV/atom Nuclear explosives~ 1MeV/nucleon Novae explosionsfew MeV/nucleon Thermonuclear explosionsfew MeV/nucleon Core collapse supernovae100 MeV/nucleon Energy scales in various explosions

Classification H (Type II) No H (Type I) Si (Type Ia) No Si (6150A o ) He (Type Ib) No He (Type Ic) (Various types- IIn, IIP, IIL, IIb etc.) Based on optical spectra

CrabTycho Cas AKepler

SN explosion centre Photosphere Outgoing ejecta Reverse shock shell Contact discontinuity Forward shock shell Radius Density Circumstellar matter Not 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/ (2001)

Circumstellar 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 SPACE TELESCOPES

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 1993J

Giant Meterwave Radio Telescope

235 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, ± Dec 30, ± Oct 15, ± Jan 13, ± Jan 13, ± Jan 13, ± Jan 13, ± Jan 13, ± VLA GMRT

Frequency (GHz) Flux density (mJy) GMRT VLA Composite radio spectrum on day 3200  = 0.6

Synchrotron Aging Due to the efficient synchrotron radiation, the electrons, in a magnetic field, with high energies are depleted.

N(E) E N(E)=kE - . Q(E)  E -  steepening of spectral index from  =(  -1)/2 to  /2 i.e. by 0.5.

Frequency (GHz) Flux density (mJy) GMRT VLA break =4 GHz R= 1.8x10 17 cm 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 expansion Ejecta velocity Size of the SN

Upstream velocity Downstream velocity Spatial diffusion coefficient of the test particles across ambient magnetic field Particle velocity Energy gain due to diffusive Fermi acceleration

Forand Break frequency (Fransson & Bjornsson, 1998, ApJ, 509, 861)

Magnetic field independent of equipartition assumption & taking into account adiabatic energy losses and diffusive Fermi acceleration energy gain B=330 mG. (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. satellitesatmospheric Gamma-ray burst

Gamma-Ray Burst

How explosive??? Even 100 times brighter than a supernova Million 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

Swift was launched in 2004

Often followed by "afterglow" emission at longer wavelengths (X-ray, UV, optical, IR, and radio).X-rayUVopticalIRradio 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  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

THANKS!!!!

First order Fermi acceleration V1 Vs V2

Boltzmann Equation in the presence of continuous injection Form of synchrotron spectral distribution Kardashev, 1962, Sov. Astr. 6, 317

Self-similar solutions Equations of conservations in Lagrangian co-ordinates for the spherically symmetric adiabatic gas dynamics are

To find similarity solution, we substitute velocity, density and pressure into the spherically symmetric adiabatic gas dynamics equations where

This reduces the partial differential equations to where and

Hugoniot conditions