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D. Kazanas (NASA/GSFC, Code 661), J. P. Crawford (Penn. State, Fayette)
Motivated by the possible presence of scalar fields on astrophysical scales, suggested by the recent measurement of the deceleration parameter by distance supernovae surveys, we present models of neutron star structure under the assumption that the stress energy tensor involves, in addition to normal matter, a scalar field which couples to matter either directly and/or through gravity. To that end we solve the coupled Einstein -- scalar field -- hydrostatic balance equations to compute the effect of the presence of the scalar field on the neutron star structure. We find that the presence of the scalar field does change the structure of the neutron star, especially in cases of strong coupling between the scalar field and the matter density. We present the neutron star radius as a function of the matter--scalar field coupling constant for different values of the neutron star central density. The presence of the scalar field does affect both the maximum neutron star mass and its radius, the latter increasing with the value of the above coupling constant. Our results may be testable with the recent timing observations of accreting neutron stars.
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