标题： 中子星X射线爆发光谱中的引力红移吸收线 显示英文标题

标题： Gravitationally redshifted absorption lines in the X-ray burst spectra of a neutron star

摘要： 中子星的基本属性为冷核物质的状态方程提供了直接检验，状态方程描述了由构成恒星的粒子之间的强相互作用决定的压力与密度之间的关系。 确定这些属性最直接的方法是测量由中子星光球产生的光谱线的引力红移。 状态方程暗示了一个质量-半径关系，而中子星表面引力红移的测量则直接约束了质量与半径之比。 这里我们报告了低质量X射线双星EXO 0748-676的28次爆发光谱中显著吸收线的发现。 我们将最显著的特征识别为Fe XXVI和XXV n=2-3以及O VIII n=1-2跃迁，所有这些跃迁的红移均为z=0.35，在各自的跃迁范围内不确定性较小的情况下相同。 对于天体物理上合理的质量范围（M ~ 1.3-2.0 M_solar），这个值完全与由普通核物质组成的中子星模型一致，同时排除了一些中子星由更奇异物质组成的模型。 显示英文摘要

摘要： The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method of determining these properties is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere. The equation of state implies a mass-radius relation, while a measurement of the gravitational redshift at the surface of a neutron star provides a direct constraint on the mass-to-radius ratio. Here we report the discovery of signficant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO 0748-676. We identify the most signficant features with the Fe XXVI and XXV n=2-3 and O VIII n=1-2 transitions, all with a redshift of z=0.35, identical within small uncertainties for the respective transitions. For an astrophysically plausible range of masses (M ~ 1.3-2.0 M_solar), this value is completely consistent with models of neutron stars composed of normal nuclear matter, while it excludes some models in which the neutron stars are made of more exotic matter.