Download Cosmic Explosions in the Universe

Cosmic Explosions in the Universe
Poonam Chandra
Royal Military College of Canada
13th Sept 2011
Poonam Chandra
Page # 1
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.
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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.
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In universe 8 new
supernovae explode every
second.
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On our Earth, roughly 1
GRB is detected everyday.
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DEATH OF
MASSIVE
STARS
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Evolution of stars
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Nuclear reactions inside a heavy star
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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
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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.
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8MΘ ≤ M ≤ 30MΘ
M ≥ 30MΘ
Supernova
Gamma Ray Burst
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Gravitational
Collapse
Supernovae/
GRBs
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On our Earth, roughly 1
GRB is detected everyday.
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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
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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.
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WHY
SUPERNOVAE????????
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BIG BANG
75% HYDROGEN
25% HELIUM
HEAVY ELEMENTS????
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Nuclear reactions inside a heavy star
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Supernovae: seeds of life
Calcium in our bones
Oxygen we breathe
Iron, Aluminium in
our cars
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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
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The Sun
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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.
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Circumstellar interaction
Explosion center
CS wind
Forward Shock
Reverse Shock
Ejecta
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ELECTROMAGNETIC SPECTRUM
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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.
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Interaction of Supernova ejecta with CSM
gives rise to radio and X-ray emission
• Radio emission from Supernovae: Synchrotron nonthermal 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.
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(Expanded) Very Large Array
RADIO TELESCOPES
Giant Metrewave Radio Telescope
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ROSAT
ASCA
Swift
XMM
Chandra
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X-ray telescopes
XMM
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Various types of supernovae
Classification
H (Type II)
IIP
IIL
No H (Type I)
IIN
Si (Type Ia)
He (Type Ib)
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No Si (6150Ao)
No He (Type Ic)
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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.
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Peak radio and X-ray luminosities
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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 XMMNewton (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).
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VLA observations of Type IIn supernovae
SN
2005kd
2006jd
2007gy
2007nx
2007pk
2007rt
2008B
2008J
2008S
2008X
2008aj
2008am
2008be
2008bk
2008bm
2008cg
2008cu
2008en
2008es
2008gm
2008ip
2009ay
2009dn
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Days
640-1173
404-1030
72-418
22-372
2-342
49-329
21
254-336
8-308
12
6-300
40-337
27-268
4-13
252
39-222
156
132
130
52
5-124
15
55
7
Detection
Y
Y
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
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N
Distance
64
79
71
96
78
66
5.6
27
108
123
4
152
160
50
65
95
-
ATel
1182
1297
1271
1359
1366
1382
1410
1409
1408
1470
1452,55,65
1865,69
1594
1776
1891
35
2070
Chandra et al. 2011
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FFA
• Radio absorption process.
SSA
• Synchrotron self
absorption (SSA): magnetic
field, size of the shell.
• Free-free absorption (FFA):
Mass loss rate of the
progenitor star.
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Chandra et al. 2011
Synchrotron Self Absorption
Free-free Absorption
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Chandra et al. 2011
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Gamma Ray Bursts
Meszaros and Rees 1997
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GRB Missions
BeppoSAX
BATSE
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SWIFT
AVERAGE REDSHIFT = 2.7
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FERMI
AGILE
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Gamma Ray Bursts
• A big challenge when discovered in 1960s.
• Gamma-ray signals for just a fraction of
seconds to at most few minutes.
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Gamma Ray Bursts Afterglow
Meszaros and Rees 1997
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Major breakthrough
• BeppoSAX: first detection of X-ray counterpart
of GRB 970228.
• Optical detection after 20 hours.
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SWIFT
AVERAGE REDSHIFT = 2.7
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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
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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).
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Determination of Kinetic Energy for
GRB 070125 (Chandra
et al. 2008)
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GRB 090423
•
•
•
•
•
•
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+/-0.08
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Multiwaveband modeling:
(Chandra et al. 2010)
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Broadband modeling
• High energy burst exploded in constant
density medium.
• No jet break occurred until day 50.
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Previous high redshift GRB 050904 z=6.26
Afterglow Properties –
– GRB 050904 (z=6.26). Both are hyper-energetic
(>1051 erg) but they exploded in very different
environments. (in situ n=600 cm-3 for GRB
050904)
– Large energy predicted for Pop III. Not unique.
– Low, constant density predicted for Pop III. Not
unique.
– No predictions for θj, εB, εe & p
– Reverse shock detection in both GRBs
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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 2010
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Future of GRB Physics
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Atacama Large Millimeter Array
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Future: Atacama Large Millimeter Array
(ALMA)
Accurate determination of
kinetic energy
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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)
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