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Neutrinos from supernovae
 Gravitational collapse
 Observations of SN1987A
 What could be learned
about neutrinos
"From neutrinos.....". DK&ER,
lecture 10
Natural sources of neutrinos
at 10 kpc
i.e. Galaxy
center
"From neutrinos.....". DK&ER,
lecture 10
Previous Supernovae observed in
our Galaxy
A supernova explosion observed in 1054
AD created a neutron star in the Crab
nebula..
It has a diameter of only 20-30 km, has
about the same mass as the sun and
rotates 30 times per second. Hot gas is
pulled towards the neutron star and emits
X-rays.
"From neutrinos.....". DK&ER,
lecture 10
Previous Supernovae observed in
our Galaxy
The remnants of the
supernova that
Tycho Brahe observed
in 1572
-still scorching
-10 million °C hot.
The most recent SN
visible with the bare eye
was observed by Kepler
in 1604
"From neutrinos.....". DK&ER,
lecture 10
Previous Supernovae observed in
our Galaxy
The most recent SN
visible with the bare eye
was observed by Kepler
in 1604
yellow – Hubble (visible)
red – Spitzer (infrared)
green/blue – Chandra (rtg)
"From neutrinos.....". DK&ER,
lecture 10
Supernova Remnant Puppis A
insert:
- a small source of
rtg emission
- probably a young
- neutron star running away
with velocity of 960km/s
"From neutrinos.....". DK&ER,
lecture 10
Previous Supernovae observed in
our Galaxy
Only 8 supernovae have been observed in our Galaxy:
Chinese records: 185, 386, 392 and 1006
Later: 1054, 1181, 1572, 1604
However all of them were relatively close to solar system.
More distant SN are invisible – hidden by interstellar gas
Currently many SNs are observed in other gallaxies
"From neutrinos.....". DK&ER,
lecture 10
Supernova 1987A
Feb 1984
Mar 8, 1987
On Feb 23, 1987 a supernova was observed optically in the Large
Magellanic Cloud at a distance of 170 000 light years (50 kpc)
At that time 2 large underground detectors searched for proton decays:
Kamiokande and IMB. They inspected their signals and found
4 hours earlier......
"From neutrinos.....". DK&ER,
lecture 10
Detector IMB
"From neutrinos.....". DK&ER,
lecture 10
Observations of SN1987A
IMB (Irvine-Michigan-Brookhaven)
Raw data
After standard analysis
rejecting atmospheric muons
"From neutrinos.....". DK&ER,
lecture 10
Neutrinos from Supernova 1987A in
Kamiokande
Universal
time
on Feb
23,
1987
"From neutrinos.....". DK&ER,
lecture 10
Neutrinos arrived 3-4
hours earlier than
photons because photons
could not get through
the outer layers of SN
before they thinned
enough.
IMB
events
"From neutrinos.....". DK&ER,
lecture 10
Observations of neutrinos from SN 1987A
Location
Blanc)
Detector type
Detector mass
(tons)
Threshold(MeV)
Number of events
Time of 1st
event (UT)
Absolute time
accuracy (sec)
IMB
Kamiokande Baksan
Ohio,US
Japan Russia
LSD
France
(Mont
water Cerenkov
6800
2140
liquid scintillator
200
90
19
7.5
10
5
8
11
5
???
7:35:41
7:35:35
7:36:12
0.05
60
+2
-54
"From neutrinos.....". DK&ER,
lecture 10
2:52:37
0.002
Neutrinos from Supernovae
"From neutrinos.....". DK&ER,
lecture 10
Stellar evolution
"From neutrinos.....". DK&ER,
lecture 10
Road to gravitational collapse
Main thermo-nuclear reactions:
Reaction
Ignition temp.
(millions K)
4 1H --> 4He
10
3 4He --> 8Be + 4He --> 12C100
12C + 4He --> 16O
2 12C --> 4He + 20Ne
600
20Ne + 4He --> n + 23Mg
2 16O --> 4He + 28Si
1500
2 16O --> 2 4He + 24Mg
4000
2 28Si --> 56Fe
6000
When mass of the iron core exceeds
1.4 solar masses the gravitation wins.
"From neutrinos.....". DK&ER,
lecture 10
SN produce much of the
material in the universe.
Heavy elements are only
produced in supernovae, so all
of us carry the remnants of
these distant explosions
within our own bodies.
gravitational collapse
Stellar evolution
Interplanetary
nebula
A large, dense, cool nebula (up to 106 Mo, temp.~10 K)
Protostar
Gravitation energy is transformed
into heat; a gas-dust cocoon forms.
A gravitating matter condensation grows to
~10-100 Mo
Star
Stellar wind carries away a fraction of mass.
Fusion reactions start changing H into He, a
hydrostatic equilibrium sets in..
Red Giant
M~
M ~ 8M
White
Dwarf
Black
Dwarf
Neutron
Star
Energy supply is depleted, radiation pressure
decreases. Stellar core contracts, its temperature
grows, igniting hydrogen in the envelope. New energy
supply leads to expansion of external layers.
M~
SN
Black
Hole
Red Super- Increase of surface with a
constant energy production rate
Giant
leads to decreased power and
envelope temperature.
Stellar core contracts, temperature rises, making
possible nuclear fusion of heavier elements.
"From neutrinos.....". DK&ER,
lecture 10
M >>
Stellar Evolution
"From neutrinos.....". DK&ER,
lecture 10
Stellar
Dimensions
1.
2.
3.
4.
5.
White dwarf
Red dwarf
Sun
Red Giant
Blue Giant
"From neutrinos.....". DK&ER,
lecture 10
Stellar Evolution
"From neutrinos.....". DK&ER,
lecture 10
Stellar evolutions
Initial star mass
(in solar masses)
30
10
3
1
0.3
Luminosity (sun=1)
(during principal sequence)
Livetime during princ. seq.
(in billion years)
Livetime as red giant
(billions of years)
Nuclear reactions stop at
10000
1000
100
1
0.004
0.06
0.1
0.3
10
800
0.01
0.03
0.10
0.30
0.80
iron
silicon oxygen carbon
Final fate
SN
SN
Ejected mass
(in solar masses)
Nature of final state
24
8.5
black
hole
6
neutron
star
1.5
Mass of final state
density (g/cm3)
5x1014
3x1015
helium
planetary solar
nebula
wind
2.2
0.3
2x107
"From neutrinos.....". DK&ER,
lecture 10
solar
wind
0.01
white dwarfs (all 3)
0.8
1x107
0.7
1x106
0.3
Gravitational Collapse
"From neutrinos.....". DK&ER,
lecture 10
Neutrinos from Supernovae
•56Fe has maximum binding energy
no more fusion and no more
heat production
• When a core of iron reaches a Chandrasekhar mass of
the gravitation wins and the core collapses
• Electrons of iron atoms are absorbed by protons:
1.4  M e
prompt neutrinos
neutron star
e  p   e  n
• Heat gives rise to gammas which produce e+ e- pairs and then:
e  e  Z 0   e   e
e  e  Z 0      
thermal neutrinos
e  e  Z 0    
"From neutrinos.....". DK&ER,
lecture 10
SN neutrino properties
Neutrino luminosity
vs time
EB  310 ergs
53
Beacom and Vogel
 e  17%,
 e  17%,
  ,  ,  ,   66%
"From neutrinos.....". DK&ER,
lecture 10
Thermal spectra
(Fermi-Dirac distribution)
T e  3.5MeV
T e  5MeV
T"  "  8.0MeV
Neutrinos from SN 1987A – E vs angle
Distribution of the angle with
respect to the direction from SN
Isotropic distribution
indicates mostly:
e  p  e  n

rather than:
 x  e   x  e 
(cross section smaller by
orders of magnitude.)
However some anisotropy
remains puzzling.
"From neutrinos.....". DK&ER,
lecture 10
Neutrinos from SN 1987A – E vs time
For 2 events of energies E1, E2 in
MeV and time difference t sec
the neutrino mass in eV:
19.4  t
m 
 1
1 
D 2  2 
 E1 E2 
2
where D is distance in kpc
Note thresholds:
Kamiokande 7.5 MeV
IMB 19 MeV
m( e )  11eV
"From neutrinos.....". DK&ER,
lecture 10
Neutrinos from gravitational collapse
Occurs for a star heavier than 8 solar masses when its core exceeds
Chandrasekar’s limit of M=1.4 solar mass.
A neutron star of a radius of r about 20 km is formed.
The released energy is „neutron star binding energy”:
1 1  M
EB  M    
 3 1053 ergs ( R
r R r
r)
99% of this energy is carried away by neutrinos;
neutrino luminosity L~ 3x1053 ergs
1% goes into kinetic energy of the envelope particles
Only 0.01% goes into light
And yet it’s 1049 ergs while our sun emits 1033 ergs/sec
"From neutrinos.....". DK&ER,
lecture 10
One SN shines as
1016 Suns!
Neutrinos from gravitational collapse
Total neutrino luminosity L~ 3x1053 ergs
Prompt pulse lasts only several msec
hence its total luminosity is small
Almost all L is carried away by thermal neutrinos
approximately obeying „equipartition of energy”:
L( e )  L( e )  L(  )  L(  )  L( )  L( )
However energies of   and  are less degraded by
interactions than that of  e
"From neutrinos.....". DK&ER,
lecture 10
Analysis of the observed events
Thermal neutrinos should be described by Fermi-Dirac distribution.
Their fluence  (i.e. flux integrated over time):
T – temperature
const E 2 dE
d 
T 3 1  exp( E ) E – neutrino energy
T
this spectrum was
 E   3.15 T
assumed for the
analysis
From the measurements of on
Earth one can calculate:
D 2 
L  1.5  10 ( )
T
10
50 10
52
"From neutrinos.....". DK&ER,
lecture 10
L in ergs
fluence in cm-2
T in MeV
D distance in kpc
Neutrinos from SN 1987A- results
Experiment:
IMB
1.0
0.8
Temperature (MeV)
4.2
Fluence (x 1010cm-2)
0.79  0.28
Average energy (MeV)
13.23.1
2.5
Total  e energy (x1052 ergs)
Total energy released
(x1053 ergs)
4.8  1.7
2.9  1.0
Kamiokande
0.7
0.5
2.6
1.98  0.60
8.22.2
1.7
7.8  2.4
4.7  1.5
Assuming :a) a distance of 49 kpc
b)equipartition of energy between different flavors
"From neutrinos.....". DK&ER,
lecture 10
What have we learned about
neutrinos from SN1987A
Lifetime
Mass
  5 105 (m / eV ) sec
m( e )  11 eV
For 2 neutrinos of energies E1 (MeV) and E2 (MeV)
and the difference between their flight times δt (sec)
their mass m (eV) :
m2 
19.4   t
 1
1
D 2  2 
 E1 E2 
where D (kpc) is the distance
from the supernova.
However one has to take into account a possibility that the time profile
of the neutrino emission can mimick the pulse modulation due to the finite
mass
"From neutrinos.....". DK&ER,
lecture 10
What have we learned about
neutrinos from SN1987A
Magnetic moment
 ( e )  0.8 1011 B
elmgt interaction would flip ν helicity into RH
and ν would carry away energy without
interacting - contrary to the observation that
almost all the binding energy has been
accounted for
a charged  would experience an energy
Q
17
Electric charge
 110
dependent delay due to its curved path
Qe
in the intergalactic and galactic mgt field.
"From neutrinos.....". DK&ER,
lecture 10
Test of equivalence principle
The fact that the fermions (neutrinos) and bosons (photons) reached the
Earth within 3 hours provides a unique test of the equivalence principle of
general relativity. The gravitational field of our Galaxy causes a signifcant
time delay, about 5 months, in the transit time of photons from the
SN1987A.
The observation of Feb. 23, 1987, proved that the neutrinos and the
recorded photons are acted by the same gravitationally induced time delay
within 0.5%
"From neutrinos.....". DK&ER,
lecture 10
Actually neutrinos arrived earlier...
About 3 hours earlier than light.
Photons had to wait until the
envelope gets thin enough to
pass through.
"From neutrinos.....". DK&ER,
lecture 10
SN1987A
"From neutrinos.....". DK&ER,
lecture 10
SN 1987A
Seven years later..
photos by Hubble
Space Telescope
"From neutrinos.....". DK&ER,
lecture 10
SN 1987A
"From neutrinos.....". DK&ER,
lecture 10
"From neutrinos.....". DK&ER,
lecture 10
Expected signals from future SN
in Super-Kamiokande:
Andromeda M31
Eg. for an SN in the
Galactic center at 10 kpc:
7300 oddz.  e  p  e   n
300
oddz.   e     e 
100
oddz.  e  16O  e   X
Hopefully other than
electron antineutrinos
could be studied .
SN neutrinos are
already flying to us
"From neutrinos.....". DK&ER,
lecture 10
Expected signals from future SN
In ICARUS:
CC current:
 e  40 Ar  e  40 K * (Ethr  1,5 MeV)
40
K *  40 K   (4.4 MeV)
 e  40 Ar  e  40Cl * (Ethr  7,5 MeV)
NC current:
  40 Ar    40 Ar *
40
Ar *  40 Ar   (1.5 MeV)
  e     e
There is a possibility to separate
electron neutrinos and antineutrinos
and study very low energy part of the neutrino spectrum.
"From neutrinos.....". DK&ER,
lecture 10
Expected signals from SN remnants
(SNR neutrinos)
Observation of a single SN
relies on a very brief signal –
trivial separation from
background but a very rare
event.
However the Universe is full of
neutrinos from all previous SN
flying around. One only needs to
separate them from background
of other neutrinos.
The expected rate of SNR
neutrinos is very model
dependent but experimentally
we may be close to detect them.
"From neutrinos.....". DK&ER,
lecture 10
arXiv:hep-ph/0408031
Expected signals from SN remnants
(SNR neutrinos)
Expected rate of SNR
events in a future 3
kton Icarus type
detector.
The distribution of electron
or positron energy.
"From neutrinos.....". DK&ER,
lecture 10
arXiv:hep-ph/0408031
Expected rate of gravitational collapse
in Milky Way
Estimates from:
• Historical observations: only 8 observed, however all within 5 kpc
from the Sun (other obscured by dust in galactic disk).
When one corrects for this and for the fact that not all observed
SN resulted from core collapse one gets: one SN per 20 years
• Birth rate of pulsars – model dependent: one SN per 10 or 100 years
All pulsars result from core collapse, but not all SN leave a pulsar
behind
• Oxygen abundance in the Galaxy: one SN per 10 years.
Most of oxygen originates in core collapses.
"From neutrinos.....". DK&ER,
lecture 10
Supernovae with and without core
collapse.
Core collapse only for SN II and Ib.
SN Ia:
A binary system including e.g. a white dwarf.
White dwarf (carbon/oxygen) accretes
matter from the companion and increases
its mass until new fusion reaction starts.
The whole star is destroyed in the explosion.
"From neutrinos.....". DK&ER,
lecture 10
Future observations of neutrinos
from SN
 Super-Kamiokande can „see” a few neutrinos from the near-by galaxy,
M31, in the Andromeda constellation, 2.1 million light years away
 One SN in 10-50 years in our Galaxy
but mostly invisible in optical spectrum
 For a Galactic SN thousands of events in SK
and hundreds in Icarus
 Network of instant SN warning exists to point telescopes in a SN
direction. Experiments should minimize their dead time.
 Possible observation of neutrinos from cumulated SNR
Unique way to learn about collapsing mechanism and about neutrinos
"From neutrinos.....". DK&ER,
lecture 10
Future observations of neutrinos
from SN
Eta Carinae is a massive
and unstable star with
strong stellar winds.
Perhaps a future
supernova?
"From neutrinos.....". DK&ER,
lecture 10