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!