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Circumstellar interaction in supernovae Poonam Chandra Royal Military Collage of Canada.

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Presentation on theme: "Circumstellar interaction in supernovae Poonam Chandra Royal Military Collage of Canada."— Presentation transcript:

1 Circumstellar interaction in supernovae Poonam Chandra Royal Military Collage of Canada

2 SUPERNOVAE (SNe)  Massive explosions in the universe  Few months to few years timescale  Energy emitted ergs (10 29 times more than an atmospheric nuclear explosion)  Shines brighter than the host Galaxy  As much energy in 1 month as sun in ~1 billion years  In universe 8 supernova explosions every second  Thermonuclear and gravitational collapse  Massive explosions in the universe  Few months to few years timescale  Energy emitted ergs (10 29 times more than an atmospheric nuclear explosion)  Shines brighter than the host Galaxy  As much energy in 1 month as sun in ~1 billion years  In universe 8 supernova explosions every second  Thermonuclear and gravitational collapse

3 Calcium in our bones Oxygen we breathe Iron in our cars

4 Origin: Massive stars

5 Nuclear reactions inside a star

6 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

7 Thermonuclear Supernovae

8 M >8 M sun : core collapse supernovae Burns until Iron core is formed at the center No more burning Gravitational collapse First implosion (increasing density and temperature at the center) Core very hard (nuclear matter density) Implosion turns into explosion Neutron star remnant at the centre. Explosion with ergs energy 99% in neutrinos and 1 % in ElectroMagnetic Scatter all heavy material required for life Burns until Iron core is formed at the center No more burning Gravitational collapse First implosion (increasing density and temperature at the center) Core very hard (nuclear matter density) Implosion turns into explosion Neutron star remnant at the centre. Explosion with ergs energy 99% in neutrinos and 1 % in ElectroMagnetic Scatter all heavy material required for life

9 Core Collapse Supernovae

10 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, IIb etc.) Based on optical spectra Thermonuclear

11 Specific problems: 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. Specific problems: 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. Interaction of the ejected material from the supernovae with their surrounding medium and study them in multiwavebands.

12 SN explosion centre Photosphere Outgoing ejecta Reverse shock shell Contact discontinuity Forward shock shell SN explosion centre Photosphere Outgoing ejecta Reverse shock shell Contact discontinuity Forward shock shell Circumstellar environment 10 5 K 10 9 K 10 7 K 1/R 2

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

14 Radio emission is synchrotron emission due to energetic electrons in the presence of the high energy magnetic fields. Radio emission is absorbed either by free-free absorption from the circumstellar medium or synchrotron self absorption depending upon the mass loss rate, ejecta velocity and electron temperature, magnetic field. Both absorption mechanisms carry relevant information. Radio Emission

15 Free-free absorption: absorption by external medium Information about mass loss rate. Synchrotron self absorption: absorption by internal medium Information about magnetic field and the size.

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

17 Date of Explosion : 28 March 1993 Type : IIb Parent Galaxy :M81 Distance : 3.63 Mpc SN 1993J “Unusual behaviour in the radio spectrum of SN 1993J”, P. Chandra 2007, AIP Conference Proceedings, Volume 937, pp. 331 “X-rays from explosion site: 15 years of light curves of SN 1993J”, P. Chandra, et al. 2008, submitted to ApJ “Synchrotron aging and the radio spectrum of SN 1993J”, P. Chandra, A. Ray, S. Bhatnagar 2004 ApJ Letters 604, 97 “The late time radio emission from SN1993J at meter wavelengths”, P. Chandra, A. Ray, S. Bhatnagar 2004 ApJ Letters 604, 97 “Modeling the light curves of SN 1993J”, T. Nymark, P. Chandra, C. Fransson 2008, accepted for publication in A&A

18 Understanding the physical mechanisms in the forward shocked shell from observations in low and high frequency radio bands with the GMRT and the VLA. Radio emission in a supernova arises due to synchrotron emission, which arises by the ACCELERATION OF ELECTRONS in presence of an ENHANCED MAGNETIC FIELD.

19 Giant Meterwave Radio Telescope, India Very Large Array, USA

20 On Day 3200…… GMRT+VLA spectrum Chandra, P. et al. GMRT VLA Synchrotron cooling break at 4 GHz Frequency FluxFlux

21 1.5 years later…………. ~Day 3750 Synchrotron cooling break at ~ 5.5 GHz GMRT VLA Frequency FluxFlux

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

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

24 GMRT VLA Synchrotron cooling break at 4 GHz Frequency FluxFlux Synchrotron cooling break at ~ 5.5 GHz GMRT VLA Frequency FluxFlux

25 On day 3200 B=330 mG On day 3770 B=280 mG Magnetic Field follows 1/t decline trend

26 Equipartition magnetic field is 10 times smaller than actual B, hence magnetic energy density is 4 order of magnitude higher than relativistic energy density Equipartition magnetic field~ 30 mG

27 Diffusion acceleration coefficient  =(5.3 +/- 3.0) x cm 2 s -1 Diffusion acceleration coefficient  =(5.3 +/- 3.0) x cm 2 s -1

28 Radio emission in a supernova arises due to synchrotron emission, which arises by the ACCELERATION OF ELECTRONS in presence of an ENHANCED MAGNETIC FIELD.

29 On Day 3200…… GMRT+VLA spectrum GMRT VLA Synchrotron cooling break at 4 GHz Chandra, P. et al. Frequency FluxFlux

30 SN 2006X, Patat, Chandra, P. et al. 2007, Science In Virgo cluster spiral Galaxy M100 Feb 4, 2006, 70 million light years away Type Ia supernova

31 SN 2006X, Patat, Chandra, P. et al. 2007, Science Type Ia supernova (Thermonuclear supernova) True nature of progenitor star system? What serves as a companion star? How to detect signatures of the binary system? Single degenerate or double degenerate system? Type Ia supernova (Thermonuclear supernova) True nature of progenitor star system? What serves as a companion star? How to detect signatures of the binary system? Single degenerate or double degenerate system?

32 How to investigate? Search for signatures of the material tranferred to the accreting white dwarf. Narrow emission lines Radio emission X-ray emission Till date no detection. ABSORPTION OF THE RADIATIONS COMING FROM SUPERNOVA DUE TO THE CIRCUMSTELLAR MEDIUM SURROUNDING SUPERNOVA. How to investigate? Search for signatures of the material tranferred to the accreting white dwarf. Narrow emission lines Radio emission X-ray emission Till date no detection. ABSORPTION OF THE RADIATIONS COMING FROM SUPERNOVA DUE TO THE CIRCUMSTELLAR MEDIUM SURROUNDING SUPERNOVA.

33 Observations of SN 2006X: Observations with 8.2m VLT on day -2, +14, +61, +121 Observations with Keck on day +105 Observations with VLA on day ∼ 400 (Chandra et al. ATel 2007). Observations with VLA on day ∼ 2 (Stockdale, ATel 729, 2006). Observations with ChandraXO on day ∼ 10 (Immler, ATel 751, 2006).

34 Na I D 2 line

35 Na vs Ca

36 RESULTS Associated with the progenitor system. Estimate of Na I ionizing flux: S UV ∼ 5 × photons s − 1 This flux can ionize Na I up to r i ∼ cm. Associated with the progenitor system. Estimate of Na I ionizing flux: S UV ∼ 5 × photons s − 1 This flux can ionize Na I up to r i ∼ cm. Ionization timescale τ i < Recombination timescale τ r. Increase in ionization fraction till maximum light. Recombination star t s. When all Na II recombined, no evolution. Agree with results. Recombination. This implies n e ∼ 10 5 cm − 3 (ONLY PARTIALLY IONIZED HYDROGEN CAN PRODUCE SUCH HIGH NUMBER DENSITY OF ELECTRONS ) Confinement: r H ≈ cm Ionization timescale τ i < Recombination timescale τ r. Increase in ionization fraction till maximum light. Recombination star t s. When all Na II recombined, no evolution. Agree with results. Recombination. This implies n e ∼ 10 5 cm − 3 (ONLY PARTIALLY IONIZED HYDROGEN CAN PRODUCE SUCH HIGH NUMBER DENSITY OF ELECTRONS ) Confinement: r H ≈ cm

37 Mass estimation

38 CSM expansion velocity ∼ 50 − 100 km s − 1. For R ∼ cm, material ejected ∼ 50 year before! Double-degenerate system not possible. Not enough mass. Single degenerate. Favorable. Not main sequence stars or compact Helium stars. High velocity required. Compatible with Early red giant phase stars. Possibility of successive novae ejection. CSM expansion velocity ∼ 50 − 100 km s − 1. For R ∼ cm, material ejected ∼ 50 year before! Double-degenerate system not possible. Not enough mass. Single degenerate. Favorable. Not main sequence stars or compact Helium stars. High velocity required. Compatible with Early red giant phase stars. Possibility of successive novae ejection. Nature of the progenitor star

39

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41 COLLABORATORS Claes Fransson (Stockholm Obs) Tanya Nymark (Stockholm Obs) Roger Chevalier (UVA) Dale Frail (NRAO) Alak Ray (TIFR) Shri Kulkarni (Caltech) Brad Cenko (Caltech) Kurt Weiler (NRL) Christopher Stockdale (Marquette) …and …. more

42 SN 1995N in radio and X-ray bands (Chandra et al 2008, to appear in ApJ; Chandra, P. et al. 2005, ApJ) SN 1995N in radio and X-ray bands (Chandra et al 2008, to appear in ApJ; Chandra, P. et al. 2005, ApJ) SN 1995N A type IIn supernova Discovered on 1995 May 5 Parent Galaxy MCG (Distance=24 Mpc)

43 Bremsstrahlung (kT=2.21 keV, N H =2.46 x /cm 2. ) Gaussians at 1.03 keV (N=0.34 +/ x ) and 0.87 keV (N=0.36 +/ x ) NeX NeIX?

44 Constraining the progenitor mass Compatible with 15 solar mass progenitor star Luminosity of Neon X line Cascade factor Emissivity of neon X line Number density of neon is ~ 600 cm -3. Fraction of NeXI to total Neon

45 SN 1995N Chandra observations Total counts758 counts Temperature2.35 keV Absorption column Depth1.5 x cm keV Unabsorbed flux x erg cm -2 s keV Unabsorbed flux x erg cm -2 s -1 Luminosity ( keV)2 x erg s -1

46

47 How fast ejecta is decelerating? R~t -0.8 What is the mass loss rate of the progenitor star? M/t = 6 x M sun yr -1 Density structure Density ~ R -8.5 Density and temperature of the reverse shock Forward shock: T=2.4 x 10 8 K, Density=3.3 x 10 5 cm -3 Reverse shock: T=0.9 x 10 7 K, Density= 2 x 10 6 cm -3 How fast ejecta is decelerating? R~t -0.8 What is the mass loss rate of the progenitor star? M/t = 6 x M sun yr -1 Density structure Density ~ R -8.5 Density and temperature of the reverse shock Forward shock: T=2.4 x 10 8 K, Density=3.3 x 10 5 cm -3 Reverse shock: T=0.9 x 10 7 K, Density= 2 x 10 6 cm -3

48 COLLABORATORS Claes Fransson (Stockholm Obs) Tanya Nymark (Stockholm Obs) Roger Chevalier (UVA) Dale Frail (NRAO) Alak Ray (TIFR) Shri Kulkarni (Caltech) Brad Cenko (Caltech) Kurt Weiler (NRL) Christopher Stockdale (Marquette) …and …. more

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

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

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

52 Acceleration diffusion constant Ball & Kirk 1992

53 For SN 1987A cm 2 sec -1 Scaled value of diffusion coefficient for 1993J (Ball & Kirk, 1992, ApJL)


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