On the Emission Site of Ga On the Emission Site of Ga mma Rays from Pulsars mma Rays from Pulsars Hsiang-Kuang Chang and Cheng Ho Hsiang-Kuang Chang and Cheng Ho 徐徐徐 徐徐徐 徐徐徐徐徐徐徐徐徐 徐徐徐徐徐徐徐徐徐
Jan 07, 2016
On the Emission Site of Gamma On the Emission Site of Gamma Rays from PulsarsRays from Pulsars
Hsiang-Kuang Chang and Cheng HoHsiang-Kuang Chang and Cheng Ho
徐佩君徐佩君清華大學天文研究所清華大學天文研究所
Gamma-Ray PulsarsGamma-Ray Pulsars
Their Their spectraspectra
(Thompson et al. 1999)
ModelsModels• Polar-cap• Outer-gap
(Harding 2000)
Power-law SpectraPower-law Spectra
(Nolan et al. 1996)
Photon IndicesPhoton Indices
• a steady cooling population of charged particles
Synchrotron radiation P=2 → Γ= 3/2
Curvature radiation P=4 → Γ= 5/3
Assumption Assumption
p
p
electronN
2
1
)(
p
photon EEN
3
1
)(
p
photon EEN
MethodMethodradiation curvature synchrotron
energy loss rate
characteristic energy of the emission
cooling time scale
dynamical time scale
The distance of the inferred emission site from the stellar center
curvature radiation
synchrotron radiation
Requiring that at the emission site
Bending Energy (Eb)Bending Energy (Eb) of PSR B1509-58 of PSR B1509-58
(Matz et al. 1994)
~ 50 keV
Eb of VelaEb of Vela
(Strickman et al. 1996)
10~70 MeV
Eb of PSR B1706-44Eb of PSR B1706-44
(Ray, Harding & Strickman 1999)
10 keV ~ 30 MeV
Eb of PSR B1951+32Eb of PSR B1951+32
(Chang & Ho 1997; Chang & Guo 2000)
70 keV ~ 3 MeV
Eb of GemingaEb of Geminga
(Mayer-Hasselwander et al. 1994) (Jackson et al. 2002)
10~30 MeV
Eb of PSR B1055-52Eb of PSR B1055-52
(Thompson et al. 1999)
1 keV ~ 70 MeV
Determining the emission siteDetermining the emission site
(H-K Chang)
ResultResult
DiscussionDiscussion• Under the assumption that the gamma-ray
emission comes from a steady cooling population of charged particles, the synchrotron radiation in outer magnetospheres as the emission mechanism is consistent with the spectral behavior of most gamma-ray pulsars.
• Exception: Crab pulsar, PSR B1509-58
• The inverse Compton scattering is not considered in this method
ReferenceReferencePeter Meszaros, 1992, The University of Chicago Press, “High-Energy Radiation from Magnetized Neutron Stars” Harding A. K., 2000, arXiv:astro-ph/0012268 George B. Rybicki, Alan P. Lightman, New York :Wiley,c1979. “Radiative processes in astrophysics”
Chang H.-K., Guo T.-F., 2000, Chinese Journal of Physics, 38, 429Chang H.-K., Ho C., 1997, ApJ, 479, L125 Jackson M. S. et al., 2002, ApJ, 578,935Matz S. M. et al., 1994, ApJ, 434, 288Mayer-Hasselwander H. A. et al., 1994, ApJ, 421, 276Nolan P. L. et al., 1996, A&AS, 120, C61Ray A., Harding A. K., Strickman M., 1999, ApJ, 513, 919Strickman M. S. et al., 1996, ApJ, 460, 735Thompson D. J. et al., 1999, ApJ, 516, 297
Thank you !Thank you !
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