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A Broad-Band X-Ray Study of the Geminga PulsarWe present a comprehensive study of the Geminga pulsar at energies 0.1-10 keV using data from the ASCA, ROSAT, and EUVE satellites. The bulk of the soft X-ray flux can be parameterized as a blackbody of T = (5.6 +/- 0.6) x 10(exp 5) K, occupying a fraction 0. 10 - 0.64 of the surface area of the neutron star at the parallax distance of 160 pc. The ASCA detection of Geminga resolves the nature of the harder X-ray component previously discovered by ROSAT in favor of nonthermal emission, rather than thermal emission from a heated polar cap. The hard X-ray spectrum can be fitted by a power-law of energy index 1.0 +/- 0.5. The hard X-ray light curve has a strong main peak and a weak secondary peak; its total pulsed fraction is = 55%. Three ROSAT PSPC observations show significant variability of Geminga's light curve. In particular, a peculiar energy dependence of the modulation in the soft X-ray component, dubbed the "Geminga effect" in the original PSPC data, is not present in later observations. In addition, fine structure in the soft X-ray light curve, interpreted as eclipses due to cyclotron resonance scattering by a plasma screen on the closed magnetic field lines, almost disappeared in the most recent observations. All of the variable properties of Geminga can probably be associated with the nonthermal process that supplies e(sup +, sup -) pairs to its inner magnetosphere.
Document ID
20010055642
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Halpern, Jules P.
(Columbia Univ. New York, NY United States)
Wang, F. Y.-H.
(Columbia Univ. New York, NY United States)
Oliversen, Ronald
Date Acquired
August 20, 2013
Publication Date
May 1, 2001
Publication Information
Publication: The New X-Ray/Gamma-Ray Pulsars
Subject Category
Space Radiation
Funding Number(s)
CONTRACT_GRANT: NAG5-3229
Distribution Limits
Public
Copyright
Other

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