nagataki

Slide1: 

　　　超新星残骸に包まれたパルサーからの 　　　　　　　　高エネルギーニュートリノ　 　　　　　　　　　　　　　東大理 　　　　　　　　　 　　長滝　重博 　　　　　　　　　　 ApJ, accepted (astro-ph/0309715).

§Introduction: 

§Introduction

Previous Works: 

Previous Works Gunn and Ostriker (1969) pointed out the possibility that a rotating magnetic　neutrons star may be a source of high energy cosmic rays. It is pointed out that hadronic component may exist in pulsar winds as a consequence of the net charge neutrality in the outflow (ex. Hoshino et al. 1992). Moreover, hadronic components may be the energetically dominant species although they are dominated by electron-positron pairs in number, because inertial masses of hadrons are much larger than that of electrons (Hoshino et al. 1992). Based on this assumption that hadronic components are not negligible in pulsar winds, some scenarios are proposed to produce high energy neutrinos and gamma-rays generated through interactions between accelerated high energy cosmic rays and surrounding photon fields (Beal & Bednarek 2002) and/or matter (Protheroe et al. 1998; Bednarek and Bartosik 2003; Amato et al. 2003).

What’s new?: 

What’s new? In this work, we estimate fluxes of neutrinos and gamma-rays including an effect that has not been taken into consideration, that is, interactions between high energy cosmic rays themselves in the nebula flow, which is based on the model presented by Kennel and Coroniti (1984). Pulsar Pulsar winds (cold) Termination Shock Nebula Flow (hot) Supernova Ejecta Previous Works This work Outer boundary Outline of the model of Kennel and Coroniti (1984)

Assumptions in This Work: 

Assumptions in This Work In this study, we consider the case where proton is the energetically dominant component (n / (n + n ) > 10 ). e+ p Initial bulk Lorenz factor of protons is constant and same with that of electrons. Bulk flow is entirely randomized by passing through the termination shock and distribution functions of protons and electrons behind the termination shock obey the relativistic Maxwellians. This assumption is supported by numerical calculations by Hoshino et al.1992. Energy distribution of protons behind the termination shock (Hoshino et al. 1992) Contribution of Fermi I acceleration is not included in this study in order to avoid the uncertainty of the efficiency of the Fermi I acceleration. It is noted that the system is not thermalized but just randomized. e- -3 ～

§Formulation: 

§Formulation

Procedure to Estimate Fluxes of Neutrinos and Gamma-rays: 

Procedure to Estimate Fluxes of Neutrinos and Gamma-rays 1. Hydrodynamics (Kennel & Coroniti 1984) a. Pulsar Winds b. Shock Conditions c. Nebula Flow d. Outer boundary (SN ejecta) 2. Microphysics of proton-proton Interaction Location of the termination shock is determined from the outer boundary condisitons.

Hydrodynamics (1): 

Hydrodynamics (1) Pulsar Winds (we determine the luminosity and bulk Lorenz factor of the wind as functions of B and P) Spin-down power of a pulsar Wind luminosity is assumed to be comparable with the spin- down power Ratio of magnetic flux to the particle energy flux. This is fixed by the outer boundary conditions. Electric potential difference between the pole and the feet of the corotating magnetosphere which is nearest to the pole. Maximum energy and bulk Lorenz factor of protons Spin-down age

Hydrodynamics (2): 

Hydrodynamics (2) Shock Conditions Relativistic Rankine-Hugoniot relations for perpendicular shock (m: specific enthalpy) Approximation (cold&relativistic) Assumption: Relativistic Maxwellian

Hydrodynamics (3): 

Hydrodynamics (3) Nebula Flow Conservation of number flux Conservation of magnetic flux Propagation of thermal energy Conservation of total energy Solution In particular, Location of the termination shock and value of s are determined so as to achieve a contact discontinuity at the outer boundary. D=16pP2g2B2 2 2 2 Functions of s and r r P u

Hydrodynamics (4): 

Hydrodynamics (4) Outer boundary condistions (interface between nebula flow and supernova ejecta) Contact discontinuity V = V =2000km/s P = P SNR SNR Nebula Nebula Thermal energy in a He layer Volume of the remnant Vmax=3000km/s, Vmin=2000km/s Pressure of the SN ejecta as a function of time s=0.0067

Microphysics of Proton-Proton Interaction (1): 

Microphysics of Proton-Proton Interaction (1) Number of collisions that occur in a volume dV, for a time dt Fluid rest frame Observer’s frame Number spectrum of pions [particles cm s erg ] -3 -1 -1 Differential cross section Number spectrum of pions is unit solid angle [particles cm s erg sr ] -3 -1 -1 -1 DV is the fluid element However, the bulk flow is non- relativistic in the nebula flow. Thus, number spectrum is not so deformed due to this Lorenz transformation. Relativistic Maxwellian

Microphysics of Proton-Proton Interaction (2): 

Microphysics of Proton-Proton Interaction (2) Fluid rest frame Lab system Fluid rest Fluid rest Particle1 rest Procedure: Calculation of the differential cross section Four momentum of a pion in the Lab frame Fluid rest frame Since Result: Where Scaling law model (Badhwar et al. 1977) ＝０

§Results: 

§Results

Slide15: 

In this study, we have to check whether the energy spectrum of protons can be regarded to obey the Maxwellian distribution. From this argument, some constraints are derived. Production rate of pions [erg/s] should be much smaller than the luminosity of the pulsar wind. (ii) Synchrotron cooling timescale of protons should be longer than traveling timescale and/or pp collision timescale. (iii) Energy transfer timescale from protons to electrons should be longer than traveling timescale and/or pp collision timescale. (tad, tm,sync,tIC) : Later

Event Rates of Neutrino whose　energy is greater than 10GeV: 

Event Rates of Neutrino whose　energy is greater than 10GeV Peak of the event rate around G～10 -10 4 5 Flux is enhanced along with time

Density and Temperature behind the Termination Shock: 

Density and Temperature behind the Termination Shock kT～Gmpc 2 High energy Low flux Low energy High flux Peak of the event rate

Profiles of Velocity, Number Density,Temperature, Magnetic Field, and Emissivity of Charged Pions: 

Profiles of Velocity, Number Density,Temperature, Magnetic Field, and Emissivity of Charged Pions Age=1yr Age=100yr Location of the Termination shock Inner-edge of the supernova ejecta Emissivity Pressure Is lower Location of the Termination shock moves inwardly t P r n F

Spectrum of Energy Fluxes of Neutrinos from a Pulsar: 

Spectrum of Energy Fluxes of Neutrinos from a Pulsar Age=1yr Age=100yr Low energy (T:small) High flux (n:large) High energy (T:large) Low flux (n:small) Flux becomes higher Atomospheric neutrino D=10kpc

Neutrino Event Rate per Year from a Pulsar as a Function of Muon Energy Threshold: 

Neutrino Event Rate per Year from a Pulsar as a Function of Muon Energy Threshold Age=1yr Age=100yr Atomospheric neutrino D=10kpc Neutrino signals can dominate the Background of the atomospheric neutrino Atomospheric neutrino

Spectrum of Energy Fluxes of Neutrinos from a Pulsar with P=5ms: 

Spectrum of Energy Fluxes of Neutrinos from a Pulsar with P=5ms D=10kpc Age=10yr Age=1000yr Fluxes of neutrinos are too low to be detected in the cases where B=10 G and P=5ms. 12 Fluxes of neutrinos are very sensitive to the spin-down luminosity

Profiles of Velocity, Number Density, Temperature, Magnetic Field, and Emissivity of Charged Pions for a Pulsar with P=5ms: 

Profiles of Velocity, Number Density, Temperature, Magnetic Field, and Emissivity of Charged Pions for a Pulsar with P=5ms P=1ms P=5ms P(period) L rs n e Pressure of the supernova ejecta is assumed not to depend on the pulsar’s activity.

Integrated Gamma-ray Fluxes from Neutral Pion Decays: 

Integrated Gamma-ray Fluxes from Neutral Pion Decays P=1ms,D=10kpc Age=1yr Age=100yr Gamma-rays will be detected by Cherenkov Detectors as well as gamma-ray satellites.

Integrated Gamma-ray Fluxes from Neutral Pion Decays: 

Integrated Gamma-ray Fluxes from Neutral Pion Decays P=1ms,D=10kpc Age=1yr Age=100yr Gamma-rays will be detected by Cherenkov Detectors as well as gamma-ray satellites.

Integrated Gamma-ray Fluxes from Neutral Pion Decays from a Pulsar with P=5ms: 

Integrated Gamma-ray Fluxes from Neutral Pion Decays from a Pulsar with P=5ms D=10kpc Age=10yr Age=1000yr Fluxes of gamma-rays are too low to be detected in the cases where B=10 G and P=5ms. 12

§ Discussions: 

§ Discussions

Other timescales: 

Other timescales 1. Inverse compton cooling timescale 2. Synchrotron cooling timescale of muon Inverse compton cooling is negligible When , mean lifetime of muon becomes longer than the synchrotron cooling time. 3. Adiabatic cooling time is taken into consideration by adopting nebula flow equations.

§ Conclusion: 

§ Conclusion

Slide29: 

We have estimated fluxes of neutrinos and gamma-rays from a pulsar surrounded by supernova ejecta in our galaxy, including an effect that has not been taken into consideration, that is,interactions between high energy cosmic rays themselves in the nebula flow. We have found that fluxes of neutrinos and gamma-rays depend very sensitively on the wind luminosity. In the case where B=10 G and P=1ms, neutrinos should be detected by km high energy neutrino detectors such as AMANDA, ANTARES, and IceCube. Also, gamma-rays should be detected by Cherenkov telescopes such as CANGAROO, HEGRA, MAGIC, VERITAS, and HESS as well as by GLAST and INTEGRAL satellites. 12 2 We have found that interactions between high energy cosmic rays themselves are so effective that this effect can be confirmed by future observations. Thus, we conclude that it is worth while investigating this effect further in the near future.