On the Emission Site of Gamma Rays from Pulsars Hsiang-Kuang Chang and Cheng Ho 徐佩君清華大學天文研究所

Gamma-Ray Pulsars

Their spectra (Thompson et al. 1999)

Models Polar-cap Outer-gap (Harding 2000)

Power-law Spectra (Nolan et al. 1996)

Photon Indices

a steady cooling population of charged particles  Synchrotron radiation P=2 → Γ ＝ 3/2  Curvature radiation P=4 → Γ ＝ 5/3 Assumption

Method radiationcurvaturesynchrotron 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) of PSR B (Matz et al. 1994) ~ 50 keV

Eb of Vela (Strickman et al. 1996) 10~70 MeV

Eb of PSR B (Ray, Harding & Strickman 1999) 10 keV ~ 30 MeV

Eb of PSR B (Chang & Ho 1997; Chang & Guo 2000) 70 keV ~ 3 MeV

Eb of Geminga (Mayer-Hasselwander et al. 1994)(Jackson et al. 2002) 10~30 MeV

Eb of PSR B (Thompson et al. 1999) 1 keV ~ 70 MeV

Determining the emission site (H-K Chang)

Result

Discussion 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 B The inverse Compton scattering is not considered in this method

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Thank you !