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The detection of pulsed X-ray emission from a nearby radio pulsarAs part of a search for thermal surface radiation from nearby neutron stars, we have carried out a 45,000 s observation of the nearby radio pulsar PSR 1929+10 with the ROSAT PSPC. After background subtraction, a net of 420 +/- 25 photons in the 0.1 to 2.0 keV band were detected at the position of the pulsar, corresponding to a luminosity of 1.2 x 10(exp 30) ergs/sec for a source distance of 250 pc, or approximately 3 x 10(exp -4) of the pulsar's spin-down luminosity. We find coherent pulsations from PSR 1929+10 at the radio period of 0.2265 s. The folded light curve is well fitted by a sinusoidal oscillation with a pulsed fraction of about 30%. The total spectrum is fitted by a blackbody with a temperature T(sub infinity) approximately equals 3.2 x 10(exp 6) K; the implied emitting area has a radius of less than 50 m. The maximum of the X-ray light curve coincides with the radio pulse, suggesting that we are detecting the hot magnetic polar cap of the star. The temperature limit for the remainder of the stellar surface is T(sub infinity) less than 3 x 10(exp 5) K. The spatial distribution of the photons is consistent with the instrument point-spread function. We discuss the implications of these results for the temperature distribution over the surface of the star and use this detection to constrain various heating mechanisms for rotation-powered neutron stars. We also use a simple model of general relativistic light bending near the stellar surface in conjunction with the radio emission geometry and the X-ray pulsed fraction to derive a radius for the neutron star of R = 9 +/- 3 km.
Document ID
19950030070
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Yancopoulos, S.
(Columbia University New York, NY, United States)
Hamilton, T. T.
(Columbia University New York, NY, United States)
Helfand, D. J.
(Columbia University New York, NY, United States)
Date Acquired
August 16, 2013
Publication Date
July 10, 1994
Publication Information
Publication: The Astrophysical Journal
Volume: 429
Issue: 2 pt
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A61669
Funding Number(s)
CONTRACT_GRANT: NAG5-1912
Distribution Limits
Public
Copyright
Other

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