Issue |
A&A
Volume 398, Number 2, February I 2003
|
|
---|---|---|
Page(s) | 639 - 646 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20021570 | |
Published online | 21 January 2003 |
X-ray and gamma-ray emission from millisecond pulsars
1
Department of Physics, Yunnan University, Kunming, Yunnan, PR China
2
Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong, PR China
Corresponding author: L. Zhang, astroynu@public.km.yn.cn
Received:
23
July
2002
Accepted:
17
October
2002
We present a self-consistent model to describe X-ray
and γ-ray emission from millisecond pulsars (MSPs). The
X-rays of MSPs are produced by the backflow of primary charged
particles from the outer gap and most likely consist of three
components, two thermal components and one power law component if
there is a strong multipole magnetic field on the stellar surface.
The backflow of ultra-relativistic particles emits photons with
energies about several tens of GeV via curvature radiation. These
photons cause an electromagnetic cascade about 2–3 stellar radii
above the polar cap. The synchrotron radiation of these cascade
e pairs produces hard X-rays with a power law index ~
. Near 105 cm above the stellar surface, the primary
charged particles encounter the strong surface magnetic field,
which alters the local radius of curvature greatly, and they
quickly loose more than half of their remaining energies to
curvature radiation. These curvature photons heat up the polar cap
area with a radius ~ 105 cm, which produce the softer
thermal X-ray component. Finally, the primary charged particles
deposit their remaining energies in a much smaller polar cap area,
which corresponds to the footprints of outer gap and produce the
medium hard X-ray component. γ-rays are produced in the
outer gap through synchro-curvature radiation. We have applied
this model to the MSPs which emit pulsed X-rays and likely
γ-rays such as PSR J0437-4715, PSR J2124-3358,
PSR J0218+4232 and PSR B1821-24. Our results give an agreement between
predicted spectrum and the observed spectrum of MSP emission.
Key words: gamma rays: theory / stars: pulsars: general
© ESO, 2003
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