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Science 30 May 1975:
Vol. 188. no. 4191, pp. 930 - 933
DOI: 10.1126/science.188.4191.930
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Articles

Binary Pulsar PSR 1913 + 16: Model for Its Origin

H. M. Van Horn 1, S. Sofia 1, M. P. Savedoff 1, J. G. Duthie 1, and R. A. Berg 1

1 Department of Physics and Astronomy and C. E. Kenneth Mees Observatory, University of Rochester, Rochester, New York 14627

The existing observational data for the binary pulsar PSR 1913 + 16 are sufficient to give a rather well-defined model for the system. On the basis of evolutionary considerations, the pulsar must be a neutron star near the upper mass limit of 1.2 solar masses (M·). The orbital inclination is probably high, ige 700, and the mass of the unseen companion probably lies close to the upper limit of the range 0.25 M· to 1.0 M·. The secondary cannot be a main sequence star and is probably a degenerate helium dwarf. At the 5.6-kiloparsec distance indicated by the dispersion measure, the magnetic dipole model gives an age of sim4 x 104 years, a rate of change of the pulsar period of P sim2 nanoseconds per day, and a surface magnetic field strength simfrac13 that of the Crab pulsar. The pulsar is fainter than an apparent magnitude Vsim+ 26.5 and is at least sim80 times fainter than the Crab pulsar in the x-ray band. The companion star should be fainter than V sim+ 30, and a radio supernova remnant may be detectable near the position of the pulsar at a flux level of le10 janskys. Important tests of this model will be provided by more accurate measurement of P and by a careful search for a faint supernova remnant.

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