Cosmic Explosions in the Universe

1. Cosmic Explosions in the Universe Poonam Chandra Royal Military College of Canada Page # 1 Poonam Chandra 13th Sept 2011

2. Universe is 14 billion years old. • Our sun is 5 billion years old. Supernovae and Gamma ray bursts explosions lasting fraction of a second to few seconds. Poonam Chandra

3. Supernova and Gamma Ray Burst: Two biggest explosions in the universe after the Big Bang Poonam Chandra

4. Supernovae & Gamma Ray Bursts: Most powerful explosions • Energy 1051 ergs. This is 1029 times more than an atmospheric nuclear bomb explosion. • One supernova can shine brighter than the whole galaxy consisting of 200 billion stars. • As much energy as the Sun will emit in 5 billion years. • Gamma ray bursts are 100 times more powerful than the supernovae. Poonam Chandra

5. In universe 8 new supernovae explode every second.

6. On our Earth, roughly 1 GRB is detected everyday.

7. DEATH OF MASSIVE STARS Poonam Chandra

8. Evolution of stars Poonam Chandra

9. Nuclear reactions inside a heavy star Poonam Chandra

10. M >8 Msun : core collapse supernovae • Burns until Iron core is form at the center • Gravitational collapse • First implosion (increasing density and temperature at the center) • Implosion turns into explosion • Neutron star remnant at the centre. • Explosion with 1053 ergs energy • 99% in neutrinos and 1 % in Electromagnetic Poonam Chandra

11. M > 30 Msun : Gamma Ray Bursts • Forms black hole at the center • Rapidly rotating massive star collapses into the black hole. • Accretion disk around the black hole creates jets • Some GRBs associated with supernovae (GRB980425/SN1998bw, GRB030329/SN2003dh etc.) • These GRBs last for few seconds • Afterglow lasts for longer duration in lower energy bands. Poonam Chandra

12. 8MΘ≤ M ≤ 30MΘ Supernova M ≥ 30MΘ Gamma Ray Burst Poonam Chandra

13. Gravitational Collapse Supernovae/GRBs Poonam Chandra

14. On our Earth, roughly 1 GRB is detected everyday.

15. 4-8 Msun : Thermonuclear supernovae • 4-8 Massive star: Burning until Carbon • Makes Carbon-Oxygen white dwarf • White Dwarf in binary companion accretes mass • Mass reaches Chandrashekhar mass • Core reaches ignition temperature for Carbon • Merges with the binary, exceed Chandrasekhar mass • Begins to collapse. Nuclear fusion sets • Explosion by runaway reaction – Carbon detonation • Nothing remains at the center • Energy of 1051 ergs comes out • Standard candles, geometry of the Universe Poonam Chandra

16. Short Hard Bursts • Neutron stars or black holes formed during end stages of massive stars • Merger of two neutron stars or a black hole and a neutron star colliding • Less energetic than collapsarGRBs • Duration less than < 2 seconds. Poonam Chandra

17. WHY SUPERNOVAE???????? Poonam Chandra

18. BIG BANG 75% HYDROGEN 25% HELIUM HEAVY ELEMENTS???? Poonam Chandra

19. Nuclear reactions inside a heavy star Poonam Chandra

20. Supernovae: seeds of life Calcium in our bones Oxygen we breathe Iron, Aluminiumin our cars Poonam Chandra

21. Environment around massive stars Interaction of the ejected material from the supernvae and GRBs with their surrounding circumstellar medium and study them in multiwavebands. CIRCUMSTELLAR INTERACTION Poonam Chandra

22. The Sun Poonam Chandra

23. Shock Formation in Supernovae: Blast wave shock : Ejecta expansion speed is much higher than sound speed. Shocked Circumstellar Medium: 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. Poonam Chandra

24. Circumstellar interaction Explosion center CS wind Forward Shock Reverse Shock Ejecta Poonam Chandra

25. ELECTROMAGNETIC SPECTRUM Poonam Chandra

26. Multiwaveband Study • Radio: circumstellar medium characteristics • X-ray: Shock temperature, ejecta structure. • Optical: Temporal evolution, chemical composition, explosion, distance • Infrared: circumstellar dust nebula surrounding SN. Poonam Chandra

27. Interaction of Supernova 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. Poonam Chandra

28. (Expanded) Very Large Array RADIO TELESCOPES Giant Metrewave Radio Telescope

29. ASCA Swift ROSAT XMM Chandra Poonam Chandra

30. X-ray telescopes XMM Poonam Chandra

31. Various types of supernovae Classification H(Type II)No H(Type I) Si (Type Ia)No Si(6150Ao) He(Type Ib)No He(Type Ic) IIP IIL IIN Poonam Chandra

32. Type IIn Supernovae • Suggested by Schlegel 1990. • Most diverse class of supernovae. • Unusual optical characteristics: • Very high bolometric and Ha luminosities • Ha emission, a narrow peak sitting atop of broad emission • Slow evolution and blue spectral continuum • Late infrared excess • Indicative of dense circumstellar medium. Poonam Chandra

33. Peak radio and X-ray luminosities Poonam Chandra

34. Multiwaveband campaign to understand Type IIn supernovae Chandra, Soderberg, Chevalier, Fransson, Chugai, Nymark • Observe all the Type IIN supernovae with the Very Large Array within 150 Mpc distance (PI: Chandra). • If bright enough, do spectroscopy with XMM-Newton (PI: Chandra). • Follow radio bright and/or Swift detected Type IIN supernova with ChandraXO. Get spectroscopy, separate from nearby contamination (PI: Chandra). • If detected in radio, follow with Swift-XRT (PI: Soderberg). • NIR photometry with PAIRITEL (PI: Soderberg). Poonam Chandra

35. VLA observations of Type IIn supernovae Poonam Chandra

36. Chandra et al. 2011 Poonam Chandra

37. Poonam Chandra

38. FFA • Radio absorption process. • Synchrotron self absorption (SSA): magnetic field, size of the shell. • Free-free absorption (FFA): Mass loss rate of the progenitor star. SSA Poonam Chandra

39. Chandra et al. 2011 Synchrotron Self Absorption Free-free Absorption Poonam Chandra

40. Chandra et al. 2011 Poonam Chandra

41. Gamma Ray BurstsMeszaros and Rees 1997 Poonam Chandra

42. GRB Missions BeppoSAX BATSE Poonam Chandra

43. SWIFT AVERAGE REDSHIFT = 2.7 Poonam Chandra

44. FERMI AGILE Poonam Chandra

45. Gamma Ray Bursts • A big challenge when discovered in 1960s. • Gamma-ray signals for just a fraction of seconds to at most few minutes. Poonam Chandra

46. Gamma Ray Bursts AfterglowMeszaros and Rees 1997 Poonam Chandra

47. Majorbreakthrough • BeppoSAX: first detection of X-ray counterpart of GRB 970228. • Optical detection after 20 hours. Poonam Chandra

48. SWIFT AVERAGE REDSHIFT = 2.7 Poonam Chandra

49. Radio Observations of Gamma Ray Burst afterglows • Very Large Array program to observe Gamma Ray Bursts in radio bands since 1997 • Total observed 304 bursts since then • Detected 95 bursts i.e. 30% detection rate • Detection rate much higher in X-ray band (90%) and optical band (80%) • Detecting very far away bursts in radio bands. • With Expanded VLA detection rate is increasing • See Chandra et al. 2011b for details Poonam Chandra

50. Multiwaveband modeling • Long lived afterglow with powerlaw decays • Spectrum broadly consistent with the synchrotron. • Measure Fm, nm, na, nc and obtain Ek (Kinetic energy), n (density), ee, eb (micro parameters), theta (jet break), p (electron spectral index). Poonam Chandra