We present a new set of nonlinear , convective radial pulsation models for main sequence stars computed assuming three metallicities : Z = 0.0001 , 0.001 and 0.008 .
These chemical compositions bracket the metallicity of stellar systems hosting SX Phoenicis stars ( SXPs or pulsating Blue Stragglers ) , namely Galactic globular clusters and nearby dwarf spheroidals .
Stellar masses and luminosities of the pulsation models are based on alpha–enhanced evolutionary tracks from the BASTI website .
We are able to define the topology of the instability strip ( IS ) , and in turn the pulsation relations for the first four pulsation modes .
We found that third overtones approach a stable nonlinear limit cycle .
Predicted and empirical IS agree quite well in the case of 49 SXPs belonging to \omega Cen .
We used theoretical Period–Luminosity relations in B , V bands to identify their pulsation mode .
We assumed Z = 0.001 and Z = 0.008 as mean metallicities of SXPs in \omega Cen .
We found respectively 13–15 fundamental , 22–6 first and 9–4 second overtone modes .
Five are unstable in the third overtone mode only for Z = 0.001 .
Using the above mode identification and applying the proper mass–dependent Period–Luminosity relations we found masses ranging from \sim 1.0 to 1.2 M _ { \odot } ( < M > = 1.12 , \sigma = 0.04 M _ { \odot } ) and from \sim 1.2 to 1.5 M _ { \odot } ( < M > = 1.33 , \sigma = 0.03 M _ { \odot } ) for Z = 0.001 and 0.008 respectively .
Our investigation supports the use of evolutionary tracks to estimate of SXP masses .
We will extend our analysis to higher Helium content that may have an impact in our understanding of the BSS formation scenario .