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 period-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
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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.
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