SX Phoenicis variable

An SX Phoenicis variable is a type of variable star. These stars exhibit a short period pulsation behavior that varies on time scales of 0.03–0.08 days (0.7–1.9 hours). They have spectral classifications in the range A2-F5 and vary in magnitude by up to 0.7.^[1] Compared to the Sun, these stars have a lower metallicity, which means they have a reduced abundance of elements other than hydrogen and helium. They also have relatively high space velocity and low luminosities for stars of their stellar classification.^[2][3] These properties distinguish the SX Phoenicis variables from their cousins, the Delta Scuti variables. The latter have longer periods, strong metallicity and large amplitudes.^[4]

SX Phoenicis variables are found primarily in globular clusters and galactic halos. The variability cycle has a periodicity-luminosity relation.^[5] All known SX Phoenicis variables in globular clusters are blue straggler stars.^[6] These are stars that appear more blue (having a higher temperature) than the main sequence stars in the same cluster that have similar luminosities.^[7]

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