"from neutrinos.....". dk&er, lecture 10 neutrinos from supernovae gravitational...

"From neutrinos.....". DK&ER, lecture 10

Neutrinos from supernovaeNeutrinos from supernovae

Gravitational collapse Observations of SN1987A What could be learned about neutrinos


Natural sources of neutrinosNatural sources of neutrinos

at 10 kpci.e. Galaxy center


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.




The remnants of the supernova that Tycho Brahe observed in 1572-still scorching -10 million °C hot.

The most recent SNvisible with the bare eyewas observed by Keplerin 1604




The most recent SNvisible with the bare eyewas observed by Keplerin 1604

yellow – Hubble (visible)red – Spitzer (infrared)green/blue – Chandra (rtg)

yellow – Hubble (visible)red – Spitzer (infrared)green/blue – Chandra (rtg)


Supernova Remnant Puppis ASupernova Remnant Puppis A

insert: - a small source of rtg emission- probably a young - neutron star running away with velocity of 960km/s




Only 8 supernovae have been observed in our Galaxy:

Chinese records: 185, 386, 392 and 1006Later: 1054, 1181, 1572, 1604

Only 8 supernovae have been observed in our Galaxy:

Chinese records: 185, 386, 392 and 1006Later: 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


Supernova 1987ASupernova 1987A

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......

Feb 1984 Mar 8, 1987


Detector IMB


Observations of SN1987AIMB (Irvine-Michigan-Brookhaven)Observations of SN1987AIMB (Irvine-Michigan-Brookhaven)

Raw data After standard analysis rejecting atmospheric muons


Neutrinos from Supernova 1987A in Kamiokande

Neutrinos from Supernova 1987A in Kamiokande

Universal timeon Feb

23, 1987

Neutrinos arrived 3-4 hours earlier than photons because

photons could not get through the outer

layers of SN before they thinned enough.


IMBevents


IMB Kamiokande BaksanLSD

Location Ohio,US Japan Russia France (Mont

Blanc)

Detector type water Cerenkov liquid scintillatorDetector mass 6800 2140 200

90 (tons)Threshold(MeV) 19 7.5 10 5

Number of events 8 11 5 ???

Time of 1st 7:35:41 7:35:35 7:36:12 2:52:37 event (UT)Absolute time 0.05 60 +2 0.002accuracy (sec) -54

Observations of neutrinos from SN 1987A Observations of neutrinos from SN 1987A


Neutrinos from SupernovaeNeutrinos from Supernovae


Stellar evolutionStellar evolution


Road to gravitational collapseRoad to gravitational collapseMain thermo-nuclear reactions:

Reaction Ignition temp. (millions K)

4 1H --> 4He 103 4He --> 8Be + 4He --> 12C 10012C + 4He --> 16O 2 12C --> 4He + 20Ne 60020Ne + 4He --> n + 23Mg 2 16O --> 4He + 28Si 15002 16O --> 2 4He + 24Mg 4000 2 28Si --> 56Fe 6000

When mass of the iron core exceeds1.4 solar masses the gravitation wins.

gravitational collapse

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.

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.


Interplanetary nebula

ProtostarStar

Red Giant

Black Dwarf

White Dwarf

Red Super-Giant

SN

Neutron

Star

Black

Hole

M ~

M ~

M ~ 8M

M >>

Stellar evolution

A large, dense, cool nebula (up to 106 Mo, temp.~10 K)

A gravitating matter condensation grows to ~10-100 Mo Gravitation energy is transformed

into heat; a gas-dust cocoon forms.

Stellar wind carries away a fraction of mass. Fusion reactions start changing H into He, a hydrostatic equilibrium sets in..

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.

Increase of surface with a constant energy production rate leads to decreased power and envelope temperature.

Stellar core contracts, temperature rises, making possible nuclear fusion of heavier elements.


Stellar Evolution


Stellar Dimensions

1. White dwarf2. Red dwarf3. Sun4. Red Giant5. Blue Giant

1. White dwarf2. Red dwarf3. Sun4. Red Giant5. Blue Giant


Stellar Evolution


Stellar evolutionsStellar evolutionsInitial star mass 30 10 3 1 0.3 (in solar masses)

Luminosity (sun=1) 10000 1000 100 1 0.004 (during principal sequence)Livetime during princ. seq. 0.06 0.1 0.3 10 800 (in billion years)Livetime as red giant 0.01 0.03 0.10 0.30 0.80 (billions of years)Nuclear reactions stop at iron silicon oxygen carbon helium

Final fate SN SN planetary solar solar nebula wind wind

Ejected mass 24 8.5 2.2 0.3 0.01 (in solar masses)Nature of final state black neutron white dwarfs (all 3)

hole starMass of final state 6 1.5 0.8 0.7 0.3

density (g/cm3) 5x1014 3x1015 2x107 1x107 1x106


Gravitational Collapse


Neutrinos from SupernovaeNeutrinos 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:

ee p n prompt neutrinos neutron star

0

0

0

e ee e Z

e e Z

e e Z

thermal neutrinos

• Heat gives rise to gammas which produce e+ e- pairs and then:

1.4 ⋅Me


Beacom and Vogel

ergsEB53103

%66,,,

%,17

%,17

e

e

MeVTe

5.3

MeVTe

5

MeVT 0.8""

SN neutrino properties

Neutrino luminosityvs time

Thermal spectra(Fermi-Dirac distribution)


Neutrinos from SN 1987A – E vs angleNeutrinos from SN 1987A – E vs angle

e p e n

x xe e

Distribution of the angle with respect to the direction from SN Isotropic distribution

indicates mostly:

rather than:

However some anisotropyremains puzzling.

(cross section smaller by orders of magnitude.)


Neutrinos from SN 1987A – E vs timeNeutrinos from SN 1987A – E vs time

2

2 21 2

19.4

1 1

tm

DE E

( ) 11em eV

For 2 events of energies E1, E2 in MeV and time difference t sec the neutrino mass in eV:

where D is distance in kpc

Note thresholds: Kamiokande 7.5 MeV IMB 19 MeV


Neutrinos from gravitational collapse

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”:

531 13 10 ergs ( )B

ME M 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 particlesOnly 0.01% goes into light

And yet it’s 1049 ergs while our sun emits 1033 ergs/sec

One SN shines as 1016 Suns!


Neutrinos from gravitational collapse Neutrinos from gravitational collapse

Prompt pulse lasts only several msec

hence its total luminosity is small

Total neutrino luminosity L~ 3x1053 ergs

Almost all L is carried away by thermal neutrinos approximately obeying „equipartition of energy”:

( ) ( ) ( ) ( ) ( ) ( )e eL L L L L L

Howeverenergies of and are less degraded by interactions than that of e


Analysis of the observed eventsAnalysis of the observed events

2

3

1 exp( )

3.15

const E dEd

ETT

E T

Thermal neutrinos should be described by Fermi-Dirac distribution. Their fluence (i.e. flux integrated over time):

T – temperatureE – neutrino energy

From the measurements of on Earthone can calculate

52 210

1.5 10 ( )50 10

DL T

L in ergsfluence in cm-2

T in MeVD distance in kpc

this spectrum was assumed for the

analysis


Experiment: IMB Kamiokande

Temperature (MeV)

Fluence (x 1010cm-2)

Average energy (MeV)

Total e energy (x1052 ergs)

Total energy released (x1053 ergs)

Neutrinos from SN 1987A- results

Neutrinos from SN 1987A- results

Assuming :a) a distance of 49 kpc b)equipartition of energy between different flavors

1.0 0.70.8 0.54.2 2.6

0.79 0.28 1.98 0.60

3.1 2.22.5 1.713.2 8.2

4.8 1.7 7.8 2.4

2.9 1.0 4.7 1.5


What have we learned about neutrinos from SN1987A


Lifetime 55 10 ( / )m eV

Mass ( ) 11em eV sec

m2 =19.4 ⋅t

D1E1

2 −1E2

2

⎛

⎝⎜⎞

⎠⎟

For 2 neutrinos of energies E1 (MeV) and E2 (MeV) and the difference between their flight times δt (sec) their mass m (eV) :

For 2 neutrinos of energies E1 (MeV) and E2 (MeV) and the difference between their flight times δt (sec) their mass m (eV) :

where D (kpc) is the distancefrom the supernova.where D (kpc) is the distancefrom 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

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




11( ) 0.8 10e B Magnetic moment

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

Electric charge 171 10e

Q

Q

a charged would experience an energy dependent delay due to its curved path in the intergalactic and galactic mgt field.


Test of equivalence principleTest 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%


Actually neutrinos arrived earlier...Actually neutrinos arrived earlier...

About 3 hours earlier than light.Photons had to wait until the envelope gets thin enough to pass through.

About 3 hours earlier than light.Photons had to wait until the envelope gets thin enough to pass through.


SN1987A


SN 1987A

Seven years later.. photos by Hubble Space Telescope


SN 1987A


Expected signals from future SN

Andromeda M31in Super-Kamiokande:

Eg. for an SN in the Galactic center at 10 kpc:

16

7300 oddz.

300 oddz.

100 oddz.

e

e

p e n

e e

O e X

Hopefully other than electron antineutrinos could be studied .

SN neutrinos are already flying to us


Expected signals from future SN

In ICARUS:

e + 40Ar→ e− + 40K * (Ethr = 1,5 MeV) 40K * → 40K + γ (4.4 MeV)

ν e + 40Ar→ e+ + 40Cl* (Ethr = 7,5 MeV)

CC current:CC current:

NC current:NC current:

+ 40Ar→ ν + 40Ar* 40Ar* → 40Ar + γ (1.5 MeV)

ν + e− → ν + e−

There is a possibility to separate electron neutrinos and antineutrinosand study very low energy part of the neutrino spectrum.


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.

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.

arXiv:hep-ph/0408031arXiv:hep-ph/0408031


Expected signals from SN remnants(SNR neutrinos)

Expected rate of SNR events in a future 3 kton Icarus type detector.

Expected rate of SNR events in a future 3 kton Icarus type detector.

The distribution of electron or positron energy.The distribution of electron or positron energy.

arXiv:hep-ph/0408031arXiv:hep-ph/0408031


Expected rate of gravitational collapse in Milky Way

Estimates from: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

• 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

• 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.• Oxygen abundance in the Galaxy: one SN per 10 years. Most of oxygen originates in core collapses.


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.

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.


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




Eta Carinae is a massive and unstable star with strong stellar winds. Perhaps a future supernova?

"from neutrinos.....". dk&er, lecture 10 neutrinos from supernovae gravitational...

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