Download - Neutrinos from Gamstars
Neutrinos from Gamstars
G.F. Bignami, IUSS PaviaM. Roncadelli, INFN Pavia
GAMSTAR? = Gamma-Ray (Neutron) Star!
Why now ?
1- Geminga-like Gamstars can bridge gap e.m.astronomy astronomy
’00s
GAMSTAR? = Gamma-Ray (Neutron) Star!
Why now ?
2- Fermi Discovers tens of new Gemingas
1- Geminga-like Gamstars can bridge gap e.m.astronomy astronomy
LAT discovers a radio-quiet pulsar!
P ~ 317 ms
Pdot ~ 3.6E-13
Characteristic age ~ 10,000 yrs
The Pulsing Sky
Pulses at1/10th true rate
GAMSTAR? = Gamma-Ray (Neutron) Star!
Why now ?
2- Fermi Discovers tens of new Gemingas
1- Geminga-like Gamstars can bridge gap e.m.astronomy astronomy
3- Ice Cube 40 is now coming of age
Starting point: s via photoproduction
p + n + + n + a+ + b (+ + -)
+ e + e
N.B. pion photoproduction kinematically possible if Ep E > 0.3 GeV2 f f= 1/1-cosp
Geminga à la Goldreich and Julian
Max proton energy = 0.4 103 TeV (P=0.237 s)
Proton number density n= 3.2 1011 cm-3
High-energy photons are produced through curvature radiation by e+, e- close to light cylinder RL = c/ = 1.1 109 cm
Average photon energy assumes E =200 MeV
Simple geometry tranform cylinder in spherical shell 0.9 RL < r < RL
The GJ energetic protons, accelerated close to the star, interact with s around RL
Production of energetic neutrinos is boosted well above that on thermal target photons !
The target energetic photon density n is
n = 0.7 10 7 cm-3
Introducing a standard cross section p + n + + = 5 10-28 cm-2
The resulting conversion probability PP= 0.1 RL n or 3.9 10-13
Thus, the resulting Geminga neutrino flux in Ice Cube
above 1 TeV for its measured distance
is
1-10 km-2 y-1
magic # 4 ICE3 !
Bonus #1 : contrary to our rough approximation, neutrinos will be pulsed, just like gamma-rays
Bonus #2 : Geminga will be the first and the brightest , but a list of Gamstar as candidate neutrino sources will soon be provided by Fermi
1
10
100
1000
10000
1968 1972 1982 1999 2012
gamma ray sourcesGemingas
3
25
271
3000
1 1 1
100
Think of the number of neutrino sources 50 ys from now!