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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. Supernovae. Calcium in our bones. Oxygen we breathe. Iron in our cars. SUPERNOVA. Death of a massive star. Violent explosions in the universe

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Circumstellar interaction of supernovae and gamma-ray bursts

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  1. Circumstellar interaction of supernovae and gamma-ray bursts Poonam Chandra National Radio Astronomy Observatory & University of Virginia

  2. Supernovae Calcium in our bones Oxygen we breathe Iron in our cars

  3. 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.)

  4. SUPERNOVAE

  5. Thermonuclear Supernovae

  6. Core Collapse Supernovae

  7. Two kinds of supernova explosions • Thermonuclear Supernovae • Type Ia • No remnant remaining • Less massive progenitor (4-8 MSolar) • Found in elliptical and Spiral galaxies • 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)

  8. Energy scales in various 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

  9. Based on optical spectra 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.)

  10. Crab Tycho Kepler Cas A

  11. Not to scale Circumstellar matter Density Radius SN explosion centre Photosphere Outgoing ejecta Reverse shock shell Contact discontinuity Forward shock shell

  12. 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.

  13. Chevalier & Fransson, astro-ph/0110060(2001)

  14. 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.

  15. Interaction of SN ejecta with CSM gives rise to radio and X-ray emission • 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.

  16. X-ray emission from supernovae Thermal X-rays versus Non-thermal X-rays

  17. X-rays from the shocked shell

  18. Inverse Compton scattering (non-thermal)

  19. X-rays from the clumps in the CSM(thermal)

  20. SPACE TELESCOPES XMM Swift

  21. RADIO TELESCOPES

  22. 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. ? ?

  23. SN 1993J • Date of Explosion:28 March 1993 • Type: IIb • Parent Galaxy:M81 • Distance:3.63 Mpc

  24. Giant Meterwave Radio Telescope

  25. 235 MHz map of FOV of SN1993J M82 M81 1993J

  26. Observations of SN 1993J at meter and shorter wavelengths GMRT VLA

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

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

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

  30. Composite radio spectrum on day 3200 nbreak =4 GHz c2= 7.3 per 5 d.o.f. R= 1.8x1017cm B= 38±17 mG Flux density (mJy) GMRT  = 0.6 c2= 0.1 per 3 d.o.f. VLA Frequency (GHz)

  31. Synchrotron Aging in SN 1993J • Synchrotron losses • Adiabatic expansion • Diffusive Fermi acceleration Energy losses due to adiabatic expansion Ejecta velocity Size of the SN

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

  33. For and (Fransson & Bjornsson, 1998, ApJ, 509, 861) Break frequency . .

  34. 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)

  35. 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

  36. Gamma-ray burst 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.

  37. Gamma-Ray Burst

  38. How explosive??? Even 100 times brighter than a supernova Million trillion times as bright as sun Brightest source of Cosmic Gamma Ray Photons

  39. Gamma-ray bursts • 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).

  40. In universe, roughly 1 GRB is detected everyday.

  41. GRB Missions BeppoSAX BATSE

  42. Swift was launched in 2004

  43. GRB interaction with the surrounding medium Often followed by "afterglow" emission at longer wavelengths (X-ray, UV, optical, IR, and radio).

  44. 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.

  45. 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.

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