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]

List

The following list contains selected SX Phoenicis variable that are of interest to amateur or professional astronomy. Unless otherwise noted, the given magnitudes are in the V-band.

Star	Maximum magnitude	Minimum magnitude	Period (in days)	Spectral type
SX Phoenicis[n 1]	6.76	7.53	0.055	A2V
HD 94033	9.46	10.26	0.060	B9III/IV
DY Pegasi	10.00	10.56	0.073	F5
CY Aquarii	10.42	11.20	0.061	B8
AE Ursae Majoris[n 1]	10.86	11.52	0.086	A9
XX Cygni	11.28	12.13	0.135	A5-F5
BL Camelopardalis	12.92	13.25	0.039
BX Sculptoris	13.42	13.71	0.037	A

Notes

1. double-mode

References

1. "GCVS Variability Types". General Catalogue of Variable Stars. Moscow, Russia: Russian Foundation for Basic Research, Sternberg Astronomical Institute. Retrieved 2010-03-17.
2. Burki, G.; Mayor, M. (1986). "Radial velocities with CORAVEL - Results on stellar variability and duplicity". Instrumentation and research programmes for small telescopes; Proceedings of the IAU Symposium. Christchurch, New Zealand: Dordrecht, D. Reidel Publishing Co. p. 392. Bibcode:1986IAUS..118..385B.
3. Breger, M. (Jan 1980). "The nature of dwarf Cepheids. V - Analysis and conclusions". Astrophysical Journal, Part 1. 235: 156. Bibcode:1980ApJ...235..153B. doi:10.1086/157620.
4. McNamara, D. H. (April 1995). "Period-luminosity relations of SX Phoenicis stars". Astronomical Journal. 109 (4): 1751–1756. Bibcode:1995AJ....109.1751M. doi:10.1086/117405.
5. Templeton, Matthew. "Variable Star of the Season: Delta Scuti and the Delta Scuti variables". American Association of Variable Star Observers.
6. Jeon, Young-Beom; Lee, Myung Gyoon; Kim, Seung-Lee; Lee, Ho (July 2004). "SX Phoenicis Stars in the Globular Cluster NGC 5466". The Astronomical Journal. 128 (1): 11. arXiv:astro-ph/0404069. Bibcode:2004AJ....128..287J. doi:10.1086/421735.
7. Santolamazza, P.; Marconi, M.; Bono, G.; Caputo, F.; Cassisi, S.; Gilliland, R. L. (June 2001). "Linear Nonadiabatic Properties of SX Phoenicis Variables". The Astrophysical Journal. 554 (2): 1124–1140. arXiv:astro-ph/0102029. Bibcode:2001ApJ...554.1124S. doi:10.1086/321408.