1997/11/26 by M. Coleman Miller, Frederick K. Lamb · 3 citations
Earth and Planetary Sciences · Physics and Astronomy · #Amplitude #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Brightness #Compact space #Compact star #Galaxy #High-pressure geophysics and materials #Neutron star #Optics #Oscillation (cell signaling) #Physics #Pulsars and Gravitational Waves Research #Stars #Stellar rotation #Surface brightness #astro-ph
paper · pdf · doi:10.1086/311335
published as Astrophys.J. 499 (1998) L37 · 8 pages plus one figure, AASTeX v. 4.0, submitted to The Astrophysical Journal Letters
arxiv created 1997/11/26 · openalex publication_date 1998/05/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The discovery of high-amplitude brightness oscillations at the spin frequency or its first overtone in six neutron stars in low-mass X-ray binaries during type I X-ray bursts provides a powerful new way to constrain the compactness of these stars and hence to constrain the equation of state of the dense matter in all neutron stars. Here we report general relativistic calculations of the maximum fractional rms amplitudes that can be observed during bursts, as a function of stellar compactness. We compute the dependence of the oscillation amplitude on the compactness of the star, on the angular dependence of the emission from the surface, on the rotational velocity at the stellar surface, and on whether there are one or two emitting spots. We show that color oscillations caused by the spectral variation with the angle of emission, the rotation of the star, and the limited bandwidth of the detector all tend to increase the observed amplitude of the oscillation. Nevertheless, if two spots are emitting, as appears to be the case in 4U 1636-536 and KS 1731-26, very restrictive bounds on the compactness of the star can be derived.