Figure 1. Top panels (left to right): contour plots of the fractional rms amplitudes of the first harmonic (fundamental) and second harmonic (first overtone) components of the pulse profiles and the total fractional rms amplitude produced by a single stable spot, as a function of the observer’s inclination and the inclination of the primary spot relative to the spin axis. Bottom panels (left to right): corresponding contour plots for the pulse profiles produced by two stable antipodal spots. All plots assume spot radii of 25◦ and a 1.4M star with a radius of 5M spinning at 400 Hz. The heavier lines highlight the contours where the fractional flux variation is 2%. This figure shows that emitting regions on or near the stellar surface can produce oscillation amplitudes as low as ∼1%–2% for a substantial range of viewing directions only if they are located within a few degrees of the stellar spin axis.
...read more