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

 Universe is 14 billion years old.  Our sun is 5 billion years old.  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 Chandra2

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Supernovae & Gamma Ray Bursts: Most powerful explosions Energy ergs. This is 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. Energy ergs. This is 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 Chandra4

In universe 8 new supernovae explode every second

On our Earth, roughly 1 GRB is detected everyday

DEATH OF MASSIVE STARS Poonam Chandra7

Evolution of stars Poonam Chandra8

Nuclear reactions inside a heavy star Poonam Chandra9

M >8 M sun : 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 ergs energy 99% in neutrinos and 1 % in Electromagnetic 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 ergs energy 99% in neutrinos and 1 % in Electromagnetic Poonam Chandra10

M > 30 M sun : 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. 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 Chandra11

8M Θ ≤ M ≤ 30M Θ Supernova M ≥ 30M Θ Gamma Ray Burst Poonam Chandra12

Gravitational Collapse Supernovae/ GRBs Poonam Chandra13

On our Earth, roughly 1 GRB is detected everyday

4-8 M sun : 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 ergs comes out Standard candles, geometry of the Universe 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 ergs comes out Standard candles, geometry of the Universe Poonam Chandra15

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 collapsar GRBs Duration less than < 2 seconds. 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 collapsar GRBs Duration less than < 2 seconds Poonam Chandra16

WHY SUPERNOVAE???????? Poonam Chandra17

BIG BANG 75% HYDROGEN25% HELIUM HEAVY ELEMENTS???? Poonam Chandra18

Nuclear reactions inside a heavy star Poonam Chandra19

Supernovae: seeds of life Calcium in our bones Oxygen we breathe Iron, Aluminium in our cars Poonam Chandra20

Environment around massive stars Interaction of the ejected material from the supernvae and GRBs with their surrounding circumstellar medium and study them in multiwavebands Poonam Chandra21 CIRCUMSTELLAR INTERACTION

The Sun Poonam Chandra22

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 Chandra23

Circumstellar interaction CS wind Explosion center Reverse Shock Forward Shock Ejecta Poonam Chandra24

ELECTROMAGNETIC SPECTRUM Poonam Chandra25

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 Chandra26

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 Supernova ejecta with CSM gives rise to radio and X-ray emission Poonam Chandra27

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

ROSAT Swift ASCA Chandra XMM Poonam Chandra29

X-ray telescopes XMM Poonam Chandra30

Various types of supernovae Classification H (Type II) No H (Type I) Si (Type Ia) No Si (6150A o ) He (Type Ib) No He (Type Ic) IIPIILIIN Poonam Chandra31

Suggested by Schlegel 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 Chandra32

Peak radio and X-ray luminosities Poonam Chandra33

Multiwaveband campaign to understand Type IIn supernovae 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). 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). Chandra, Soderberg, Chevalier, Fransson, Chugai, Nymark Poonam Chandra34

VLA observations of Type IIn supernovae Poonam Chandra35

Chandra et al Poonam Chandra36

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Radio absorption process. Synchrotron self absorption (SSA): magnetic field, size of the shell. Free-free absorption (FFA): Mass loss rate of the progenitor star. FFA SSA Poonam Chandra38

Chandra et al Poonam Chandra39 Synchrotron Self Absorption Free-free Absorption

Chandra et al Poonam Chandra40

Gamma Ray Bursts Meszaros and Rees Poonam Chandra41

GRB Missions BATSE BeppoSAX Poonam Chandra42

SWIFT AVERAGE REDSHIFT = Poonam Chandra43

Poonam Chandra44 FERMI AGILE

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 Chandra45

Gamma Ray Bursts Afterglow Meszaros and Rees Poonam Chandra46

Major breakthrough BeppoSAX: first detection of X-ray counterpart of GRB Optical detection after 20 hours Poonam Chandra47

SWIFT AVERAGE REDSHIFT = Poonam Chandra48

Radio Observations of Gamma Ray Burst afterglows Poonam Chandra49 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

Multiwaveband modeling Long lived afterglow with powerlaw decays Spectrum broadly consistent with the synchrotron. Measure F m, m, a, c and obtain E k (Kinetic energy), n (density),  e,  b (micro parameters), theta (jet break), p (electron spectral index) Poonam Chandra50

Determination of Kinetic Energy for GRB (Chandra et al. 2008) Poonam Chandra51

GRB X-ray observtions: 73 s after detection Optical observations: 109 s after detection No optical transient. Detection in J band onwards. Photo-z=8.06+/-0.25 Spectral-z=8.23+/ Poonam Chandra52

Multiwaveband modeling: (Chandra et al. 2010) Poonam Chandra53

Broadband modeling 54 High energy burst exploded in constant density medium. No jet break occurred until day Poonam Chandra

Previous high redshift GRB z=6.26 Afterglow Properties – – GRB (z=6.26). Both are hyper-energetic (>10 51 erg) but they exploded in very different environments. (in situ n=600 cm -3 for GRB ) – Large energy predicted for Pop III. Not unique. – Low, constant density predicted for Pop III. Not unique. – No predictions for θ j, ε B, ε e & p –Reverse shock detection in both GRBs Poonam Chandra55

A seismic shift in radio afterglow studies The VLA got a makeover! More bandwidth, better receivers, frequency coverage 20-fold increase in sensitivity Capabilities started in Poonam Chandra56

Future of GRB Physics Poonam Chandra57

Atacama Large Millimeter Array Poonam Chandra

Future: Atacama Large Millimeter Array (ALMA) Accurate determination of kinetic energy Poonam Chandra59

Collaborators: Dale Frail (NRAO) Roger Chevalier (Univ. Virginia) Shri Kulkarni (Caltech) Alicia Soderberg (Princeton) Brad Cenko (Berkeley) Claes Fransson (Stockholm Observatory) Nikolai Chugai (Moscow University) Poonam Chandra60