1. Strongly Interacting Supernovae
Poonam Chandra
National Centre for Radio Astrophysics
January 4, 2013

2. Supernova Classification (based on optical spectra and light curve)
Supernovae
Hydrogen
Type II
Narrow H lines
Type IIn
No narrow H lines
Type IIP/IIL
No Hydrogen
Type I
Silicon
Type Ia
No Silicon
Type Ib/c
Plateau
Type IIP
Linear
Type IIL
Helium
Type Ib
No Helium
Type Ic

3. What are Supernovae?
Supernovae are one of the biggest explosions in the Universe after the Big Bang.

4. Supernova Energetics
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.

5. In universe 8 new supernovae explode every second.

7. Evolution of stars

8. Nuclear reactions inside a heavy star

9. Evolution of stars

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
End stages of massive stars. Nuclear fusion. Radiative energy. In the end nuclear fuel exhausted. Gravitational collapse. Star evolved for millions
Of years. End collapse (implosion+ explosion) in few millisec. Explosion- 99% neutrino. 1% EM. NS or BH at the center.

11. Supernova

12. Supernovae:
DEATH OF MASSIVE STARS

13. WHY SUPERNOVAE????????

14. BIG BANG
75% HYDROGEN
25% HELIUM
HEAVY ELEMENTS????

15. Nuclear reactions inside a heavy star

16. Supernovae: seeds of life
Calcium in our bones
Oxygen we breathe
Iron, Aluminum in our cars

17. Supernova Interaction with the circumstellar medium

18. The Sun

19. Circumstellar interaction
Explosion center
Circumstellar medium density ~1/r2
Circumstellar wind (1E-5 Msun/Yr)
Forward Shock
~10,000 km/s
Reverse Shock
~1000 km/s
Ejecta

20. 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.

21. Circumstellar interaction
Trace back the history of the progenitor star since wind velocity ~10 km/s and ejecta speeds ~10,000 km/s.
Supernova observed one year after explosion gives information about the progenitor star 1000 years before explosion!!!

22. Circumstellar interaction
Forward Shock ~109 K
Hot ejecta
X-rays
Reverse shock ~ 107 K
Synchrotron
Radio

23. Chevalier & Fransson, astro-ph/0110060 (2003)

24. 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.

26. Radio and X-ray emission
Radio: Information about the mass loss rate of the star, density of the CSM, size etc.
X-ray : Density and temperatures of the shocked ejecta, chemical composition
X-ray
Tell the regions of Radio and X-ray emission…where do they come from….
Give the details like wind velocity, temperatures of the shocked region, ejecta speeds

27. Type IIn Supernovae Very high bolometric and Ha luminosities
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.
Radio observed between 1 year to 5000 days

28. Type IIn supernovae
Very diverse stellar evolution and mass loss history.
SN 1988z, extremely bright even after 20 years
SN 1994w faded only in 130 days.
SN 2005gl: LBV progenitor?
SN 2006gy, extremely bright: PISN progenitor?
SN 2002ic, SN 2005gj: Hybrid between Ia/IIN.
SNe 2001em, 1995N, 2008fz: Type Ib/c properties
SN 2009ip: episodic ejections before turning into true supernova

29. RADIO TELESCOPES Karl G. Jansky Very Large Array
Giant Metrewave Radio Telescope

30. X-ray telescopes
XMM
Swift

31. Multiwaveband campaign to understand Type IIn supernovae
Chandra, Soderberg, Chevalier, Fransson, Chugai
Observe most the Type IIN supernovae with the JVLA telescope (PI: Chandra).
If detected in radio, follow with Swift-XRT (PI: Soderberg).
Follow radio bright and/or Swift detected Type IIN supernova with ChandraXO. Get spectroscopy, separate from nearby contamination (PI: Chandra).
If bright enough, do spectroscopy with XMM-Newton (PI: Chandra).
NIR photometry with PAIRITEL (PI: Soderberg).
Low frequency radio follow up with the GMRT

32. SN IIn Radio Statistics
Around ~180 Type IIn supernovae
So far only 81 observed in radio bands
43 SN IIn observed by us in radio
Out of 81, only 11 detected in radio bands
4 detected by us (SN 2005kd, 2006jd, 2008iy, 2009ip)
In X-rays detected by us: SN 2006jd, 2010jl, 2009ip

33. Peak radio and X-ray luminosities
2009ip

34. Poonam Chandra

35. Poonam Chandra

36. Radio/X-ray detected Supernovae
SN 2006jd
SN 2010jl
SN 2009ip
SN 2005kd
SN 2008iy

37. SN 2006jd Chandra et al. ApJ 2012, 755, 110
Discovered October 12, 2006 in UGC 4179
Redshift z=0.0186
Initial spectrum shows Type Ib and later spectrum shows IIn
Radio Observations: VLA(EVLA), GMRT
X-ray Observations: Swift-XRT, ChandraXO, XMM- Newton

38. SN 2006jd- radio observations
With VLA starting from 2007, Nov UT
Epoch: Day 400 until Day 2000.
Frequency bands: 22.5 (K), 8.5 (X), 4.9 (C) and 1.4 (L) GHz bands
With GMRT at three epochs, between 1104 day to days.
Frequency bands: 1.4 GHz and 0.61 GHz bands. Not detected yet in 0.61 GHz bands.

40. Synchrotron self absorption indicates ejecta speed ~2000-3000 km/s
Synchrotron self absorption indicates ejecta speed ~ km/s. Too small. Free-free absorption likely to dominate.

41. Radio Absorption Models
External free-free absorption

42. Radio light curves Chandra et al. 2012, ApJ
Extenal FFA does not fit and gives m>1

43. Radio Absorption Models
External free-free absorption
Internal free-free-absorption

44. Radio light curves
Extenal FFA does not fit and gives m>1

45. Radio Spectra

46. Radio model of SN 2006jd
Internal free-free absorption with s=1.6 (r~r-s)
Seen in SN 1986J and SN 1988Z too.
Density of emitting gas r=6x106 cm-3.
Mass of absorbing gas required to do the observed absorption is 2x10-8T45/2 Msun.
Modest amount of cool gas mixed into radio emitting region can do the required absorption.
Source of the cool gas is radiative cooling of the dense gas in the shocked region.

47. SN 2006jd-XMM spectra

48. SN 2006jd-Chandra spectra

49. SN 2006jd X-rays Best fit with T>10 keV, forward shock origin
NH=1.3x1021 cm-2 (Galactic 4.5x1020 cm-2)
Detection of 6.9 keV Fe XXVI line (EW=1.4 keV).
Possible detection of 8.1 keV Ni XXVIII line
5Msun Mekal fits the data well and reproduces Fe line.
NEI model also fits data well but reproduces very low density ~7E-3 cm-3.
X-ray also gives s=1.7 (consistent with radio).
Density 3E6 cm-3
Mass swept by FS 3Msun.

50. SN 2006jd- X-ray light curves

51. SN 2006jd: Main Results
Radio and X-ray both give s~ (density~1/rs).
Mass loss rate ~ 5x10-3 Msun/yr.
Shocked gas density 3x106 cm-3.
X-ray emission well fit with single temperature model, X-ray coming from forward shocked shell.
No indication of reverse shock emission
RS moved back to centre and weakened.
RS is a cooking shock and the cool shell absorbing this.

52. SN 2006jd: Main Results
Column density is a factor 50 smaller (1.3E21) than needed to produce the X-ray luminosity (4E22). Indicate towards global asymmetry.
Lower column density also works against external FFA model. The derived external FFA optical depth from X- ray data is ~8E-4 at 5 GHz on day 1000.
EW of Fe line much higher than expected. Possible region is mixing of cool gas could enhance the width of the line.
Seen in SN 2001em too.

53. SN 2010jl Chandra et al. 2012, ApJ Letters 2012, 750, L2
Discovered on 2010 Nov 3.5 UT in UGC 5189A (z=0.011)
Discovered magnitude Brightened to 12.9.
One of the brightest apparent magnitude. (Absolute visual magnitude Mv=-20)
Archival HST image show progenitor star >30Msun.
Low metallicity host galaxy, Z~0.3Msun.
Circumstellar expansion speed km/s.

54. SN 2010jl
Radio Observations: EVLA : 10 observations from November 2010 until Now. No detection.
X-ray observations: At 3 epochs with Chandra
Novemeber 2010
October 2011
June 2012
Detection at all three epochs in X-ray bands

55. SN 2010jl Chandra Observations
November 2010
October 2011
June 2012
Duration
39.6 ks
41.0ks
39.5ks
Counts
468
1342
1484
Count Rate
1.13E-2 cts
3.29E-2 cts
3.68E-2 cts
Column Density
9.7E23 cm-2
2.67E23 cm-2
6.6E22 cm-2
Temperature
>10 keV
> 10 keV

56. SN 2010jl Chandra X-ray Spectra Comparison
November 2010
October 2011
June 2012

57. SN 2010jl Chandra Spectra

58. SN 2010jl Chandra Spectra

59. SN 2010jl Chandra Spectra

60. SN 2010jl Chandra Spectra

61. SN 2010jl Main results
Column density ~1024 cm-2 (1000 times higher than Galactic absorption).
High temperature >10 keV
High temp indicates forward shock emission
High absorbing column density not accompanied by high extinction of the SN.
This indicates column near forward shock, due to mass loss, where dust has been evaporated.
First time X-ray absorption by external medium, that is not fully ionized by the energetic medium.
Fe 6.4 keV line also points to partially unionized medium.
The high temperature of the thermal X-ray emission indicated a forward shock origin. The high absorbing column density to the X-ray emission is not accompanied by high extinction to the SN, showing that the column is probably due to mass loss near the forward shock wave where any dust has been evaporated. SN 2010jl is an example of a case where, owing to the sensitive Chandra observations, for the first time we are able to see X-ray absorption by an external medium that is not fully ionized by the energetic radiation, as well as the evolution of this absorption.

62. SN 2010jl Main results
Luminosity ( keV) ~7x1041 erg/s, amongst most luminous X-ray supernovae.
Since most emission > 10 keV, this is spectral luminosity
Ejecta speed (v=sqrt(16 kT/3m) > 2700 km/s.
Mass loss rate > 4x10-3 Msun/year
The high temperature of the thermal X-ray emission indicated a forward shock origin. The high absorbing column density to the X-ray emission is not accompanied by high extinction to the SN, showing that the column is probably due to mass loss near the forward shock wave where any dust has been evaporated. SN 2010jl is an example of a case where, owing to the sensitive Chandra observations, for the first time we are able to see X-ray absorption by an external medium that is not fully ionized by the energetic radiation, as well as the evolution of this absorption.

63. SN 2010jl Chandra X-ray
November 2010

64. SN 2010jl Chandra X-ray
October 2011

65. SN 2010jl Main results
Fe 6.4 keV (narrow k-alpha iron line) in the first epoch and not in the second epoch explains that ejecta has moved past the closeby partially unionized gas.
The equivalent width (EW=0.2 keV) consistent with that expected for this line.
Low temperature component fit by powerlaw of ~1.7 or ~1-2 keV temperature and column density is that of Galactic. Luminosity ~4x1039 erg/s.
Flux change between the two epochs is 20-30%. Consistent with a background contaminating ULX source.
Also looked at the possibility that enhanced 1 kev emission is by the CNO elements. Not possible as this gives too little absorption in keV range.
Origin of additional component (NH~8E22, kT~1keV) is not known.
The high temperature of the thermal X-ray emission indicated a forward shock origin. The high absorbing column density to the X-ray emission is not accompanied by high extinction to the SN, showing that the column is probably due to mass loss near the forward shock wave where any dust has been evaporated. SN 2010jl is an example of a case where, owing to the sensitive Chandra observations, for the first time we are able to see X-ray absorption by an external medium that is not fully ionized by the energetic radiation, as well as the evolution of this absorption.

66. SN 2009ip A Very Unique Type IIn supernova in NGC 7259
Earlier supernova imposter which had repeated eruptions, in 2009, 2010.
Flared in July 2012 and then exploded as supernova in September 2012 (speed 13,000 km/s)
Clear link with LBV progenitors (like SN 2005gl, 2006jc etc.)
SN 2009ip first SN to have both a massive blue progenitor and LBV like eruptions.

67. SN 2009ip – Radio Observations
Since September 26, 2012 till Dec 2, 2012, observations at 5 epochs in K (22.5 GHz) and X (8.5 GHz) bands with the JVLA.
Date of Obs
Frequency (GHz)
Flux Density (uJy)
Sep 26.11
21.19
<132 (3-sigma)
Sep 26.14
8.94
<66 (3-sigma)
Oct 16.06
21.25
79+/-29
Oct 17.12
108+/-40
Oct 26.04
8.85
44+/-15
Nov 06.06
52+/-21
Nov 12.97
8.99
48+/-22
Dec 01.99
46+/-129
Dec 02.93
174+/-123
Possible Detection?

68. SN 2009ip- X-ray observations
Swift observations started from Sep 4 until Dec 2012.
No X-ray emission during the decay of 2012 outburst i.e t<22nd Sept (3-sigma~3E-3 cps).
No detection even during the rise time of the event i.e. Sept 22nd < t < Oct 1st (3-sigma 1.1E-3 cps).
X-ray emission detected starting from Oct 1st when 2nd outburst in 2012 reaches UV/optical peak.
Detection until Oct 16th and then no detection from Oct 20th onwards.

69. SN 2009ip – X-ray observations

70. SN 2009ip- X-ray observations
XMM-Newton observations on 4th Nov, detection.
XMM observations for ~60ks for EPIC-PN and MOS.
Data best fit with T>10 keV and NH~1E21 cm-2
Flux absorbed 1.7E-14 erg/s/cm2 and unabsorbed 1.9E-14 erg/s/cm2.
We use XMM parameters to fit Swift spectrum as well.
As best excluded the contamination source as possible. Flux6E-15 erg/s/cm2.

71. SN 2009ip – X-ray observations

72. SN 2009ip – X-ray observations

73. SN 2009ip – Main Results Studies still going on
Very interesting supernova as shown LBV like eruptions in past few years and then exploded as true supernova.
Once detected in JVLA C band (5 GHz), we will request GMRT time in L band.

74. Summary
Type IIN supernovae: perfect example of unity in diversity as each object is very unique.
Present a systematic study of this class of objects.
Trend emerging: late radio emission.
Understanding early absorption.
Understand trends in luminosity distribution.
Two classes of supernovae?

75. Collaborators Roger Chevalier, University of Virginia
Nicolai Chugai, University of Moscow
Alicia Soderberg, Harvard-Smithsonian
Claes Fransson, Stockholm Observatory

76. Peak radio and X-ray luminosities
2009ip

77. Poonam Chandra

78. Radio Spectral Evolution

79. 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

80. How Supernovae impact the environment?
Modify the density of the surrounding medium
Increase the metallicity, hence change the course of star formation
Major role in Galaxy evolution
Modify density
After explosion, shock ejecta
Increase metalicitty

81. VLA observations of Type IIn supernovaeSN
Days
Detection
Distance
ATel
2005kd Y 64
1182
2006jd 79
1297
2008iy
2009ip
30-90 24
2010jl N 50
2007gy
72-418 -
2007nx
22-372
2007pk
2-342 71
1271
2007rt
49-329 96
1359
2008B 21 78
1366
2008J 66
2008S
8-308
5.6
1382
2008X 12 27
1410
2008aj
6-300
108
1409
2008am
40-337
1408
2008be
27-268
123
1470
2008bk
4-13 4
1452,55,65
2008bm
252
1865,69
2008cg
39-222
1594
2008cu
156
152
2008en
132
160
2008es
130
1776
2008gm 52
2008ip
5-124 65
1891
2009ay 15 95
2009dn 55
2009fs 7
2070
VLA observations of Type IIn supernovae
Poonam Chandra