Figure 3. Contour plots of the total fractional rms amplitude produced by isotropic emission from a single stable spot (left-hand panel) and from two stable antipodal spots (right-hand panel), as a function of the stellar radius and the inclination of the primary spot relative to the spin axis, for a 1.4M star with a radius of 5M spinning at 400 Hz observed at an inclination of 45◦. The heavier lines highlight the contours where the fractional flux modulation is 2%. This figure demonstrates that compactness alone cannot explain the low-amplitude oscillations of the AMXPs.
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