Left panel: effect of spin on the mass vs. equatorial radius curves for six representative EoSs allowing for a wide range of stiffness. Two curves with dark and light lines are shown for each EoS. For each pair, the lighter curve with smaller radii corresponds to the zero-spin mass–radius curve, while the darker curve with larger radii is the mass–radius curve for stars spinning at 205 Hz. The EoS in order of increasing stiffness (i.e., in order of increasing radius for a 1.4 M_⊙ star) are HLPS Soft (Hebeler et al. 2013), one of the softest EoSs allowed by nuclear physics; BBB2 (Baldo et al. 1997) is a soft EoS just marginally ruled out by the observation of a 1.97 M_⊙ pulsar; APR (Akmal et al. 1998) includes boost corrections; HLPS Intermediate and Stiff are representative EoSs from Hebeler et al. (2013); and L (Pandharipande & Smith 1975), a very stiff EoS, is most likely ruled out by the Laser Interferometer Gravitational-Wave Observatory (LIGO) observation of GW170817 (Abbott et al. 2017). The HLPS EoSs are also shown in Figures 1 and 2. Right panel: effect of spin on the equatorial compactness ratio M/R vs. central energy density. The order of curves from left to right at a value of M/R_eq = 0.15 is from stiffest to softest EoS. Two curves, corresponding to 0 and 205 Hz are plotted for each EoS, however the difference between the curves is smaller than the line width so it is difficult to see the difference by eye. The gray horizontal box shows the compactness range of ﹩M/{R}_{\mathrm{eq}}={0.156}_{-0.010}^{+0.008}﹩ for the ST+PST model reported in Riley et al. (2019).