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Polar cap and outer gap models have both evolved in order to account
for the observed emission features. Polar cap models now assume that emission
originates from only one magnetic pole and at higher altitudes.
Outer gap models must allow the gaps to extend closer to the neutron star
surface. The -ray emission must be either a hollow cone (CRPC and
ICPC polar cap
models) or a curved fan beam (outer gap models) to
produce double-peaked profiles, bridge emission and the soft-hard-soft
hardness variation; however ICPC models do not predict emission outside the
pulses. CRPC models predicted high-energy
spectral cutoffs (Daugherty & Harding 1982) and a correlation of -ray
luminosity with polar-cap current (Harding 1981), both of which have
been observed by CGRO. Outer gap models can also produce spectra turnovers,
but a luminosity-current correlation is not predicted.
Polar cap models predict an increase in spectral hardness with age;
outer gap models may predict this as well but it has not been quantified.
Outer gap models can more naturally account for phase differences between
-ray and lower energy pulses if the lower energy is assumed to come
from near the surface. It is quite possible that elements of all these
models (and more) will be necessary to account for the diverse
features of -ray pulsars.
References:
Arons, J. 1983, ApJ, 266, 215.
Arons, J. & Scharlemann, E.T. 1979, ApJ, 231, 854.
Chen, K. & Ruderman, M. A. 1993, ApJ, 402, 264.
Cheng, K. S., Ho, C. & Ruderman, M. A. 1986, ApJ, 300, 500.
Chiang, J. & Romani, R. W. 1992, ApJ, 400, 629.
Chiang, J. & Romani, R. W. 1994, ApJ, 436, 754.
Daugherty, J. K. & Harding, A. K. 1982, ApJ, 252, 337.
Daugherty, J. K. & Harding, A. K. 1989, ApJ, 336, 861.
Daugherty, J. K. & Harding A. K. 1994, ApJ, 429, 325.
Daugherty, J. K. & Harding A. K. 1996, ApJ, 458, 278.
Dermer, C. D. 1989, ApJ, 347, L13.
Dermer, C. D. 1990, ApJ, 360, 197.
Dermer, C. D. & Sturner, S. J. 1994, ApJ, 420, L75.
Fierro, J. M. 1996, Ph.D. Thesis, Stanford University.
Harding, A. K. 1981, ApJ, 245, 267.
Harding, A. K. & Baring, M. G. 1996, IAU Colloquium 160.
Harding, A. K. & Daugherty, J. K. 1996, in preparation.
Higgins, M. G. & Henriksen, R. N. 1996, MNRAS, submitted.
Ho, C. 1989, ApJ, 342, 396.
Kanbach, G. et al. 1994, A & A, 289, 855.
Lu, T., Wei, D. M. & Song, L. M. 1994, A & A, 290, 815.
Lyubarskii, Y. E. 1996, A & A, in press.
Michel, F. C. 1991, Theory of Neutron Star Magnetospheres, Univ. of Chicago Press.
Muslimov, A. G. & Tsygan, A. I. 1992, MNRAS, 255, 61.
Nel, H. I. & De Jager, O. C. 1995, Ap & SS, 230, 299.
Romani, R. W. 1996, preprint.
Romani, R. W. & Yadigaroglu, I.-A. 1994, ApJ, 438, 314.
Ruderman, M. A. & Sutherland, P. G. 1975, ApJ, 196,51.
Shabad & Usov 1985, AP & SS, 117, 309.
Sturner, S. J. & Dermer, C. D. 1994, ApJ, 420, L79.
Sturner, S. J. & Dermer, C. D. 1995, ApJ, 461, 872.
Sturner, S. J., Dermer, C. D. & Michel, F. C. 1995, ApJ, 445, 736.
Thompson, D. J. et al. 1994, ApJ, 436, 229.
Thompson, D. J. 1996, IAU Colloquium 160.
Usov, V. V. 1996, IAU Colloquium 160.
Usov, V. V. & Melrose, D. B. 1995, Aust. J. Phys., 48, 571.
Conclusions