SX Phoenicis

SX Phoenicis
Observation data
Epoch J2000      Equinox J2000
Constellation Phoenix
Right ascension 23h 46m 32.89291s[1]
Declination −41° 34′ 54.7708″[1]
Apparent magnitude (V) 7.33[2]
Characteristics
Spectral type A2 V[3]
U−B color index 0.05[4]
B−V color index 0.23[4]
Variable type SX Phe[5]
Astrometry
Radial velocity (Rv)−24.27±5.63[1] km/s
Proper motion (μ) RA: +255.287[1] mas/yr
Dec.: −857.036[1] mas/yr
Parallax (π)11.9996 ± 0.0535[1] mas
Distance272 ± 1 ly
(83.3 ± 0.4 pc)
Absolute magnitude (MV)2.87[2]
Details
Mass1.8±0.1[6] M☉
Radius2.2[7] R☉
Luminosity5.89[2] L☉
Rotational velocity (v sin i)18[4] km/s
Age20.0±9.0[6] Myr
Other designations
SX Phe, CD−42° 16457, HD 223065, HIP 117254, SAO 231773[8]
Database references
SIMBADdata

SX Phoenicis is a variable star in the southern constellation Phoenix. With an apparent visual magnitude of 7.33,[2] it is too faint to be seen with the naked eye. It is located 272 light years from the Sun, as determined from an annual parallax shift of 12 mas.[1] The star is moving closer with a heliocentric radial velocity of −24 km/s.[1]

This is the prototype SX Phoenicis variable, which means it is a population II, high amplitude, pulsating variable. The fundamental radial mode of pulsation has a period of 1.319 hours with an amplitude of 0.2059 magnitude, while the first overtone radial mode has a cycle duration of 1.026 hours for a 0.0742 magnitude amplitude. Other, lower amplitude modes have been suggested, and the pulsations of SX Phe may be undergoing cyclical changes.[9]

SX Phoenicis is a A-type main-sequence star with a stellar classification of A2 V.[3] During the 1940s it was classed as a "probable subdwarf" because of its low luminosity for the spectral class.[10][5] It is an extremely metal-poor[11] runaway star with a peculiar velocity of 323.2±12.7 km/s.[6] SX Phe has 1.8[6] times the mass of the Sun, about 2.2[7] times the Sun's radius, and shines with 6[2] times the Sun's luminosity. The star is 20[6] million years old and is spinning with a projected rotational velocity of 18 km/s.[4]

References

  1. 1 2 3 4 5 6 7 8 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. 1 2 3 4 5 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  3. 1 2 Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. 1 2 3 4 Rodríguez, E.; et al. (June 2000), "A revised catalogue of δ Sct stars", Astronomy and Astrophysics Supplement, 144: 469–474, Bibcode:2000A&AS..144..469R, doi:10.1051/aas:2000221.
  5. 1 2 Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
  6. 1 2 3 4 5 Tetzlaff, N.; et al. (2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410: 190, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  7. 1 2 Pasinetti Fracassini, L. E.; et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy & Astrophysics (Third ed.), 367: 521–24, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  8. ↑ "NU Pav". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 5 September 2018.
  9. ↑ Landes, H.; et al. (May 2007), "Long-Term Changes in the Periods of SX Phe", Publications of the Astronomical Society of Australia, 24 (1): 41–45, Bibcode:2007PASA...24...41L, doi:10.1071/AS06025.
  10. ↑ Wood, F. B. (August 1959), "The short-period variable, SX Phoenicis", Astronomical Journal, 64: 222–226, Bibcode:1959AJ.....64..222W, doi:10.1086/107924.
  11. ↑ Stankov, A.; Sinachopoulos, D.; Elst, E.; Breger, M. (February 2002), "Stromgren photometry of SX Phe = HD 223065", Communications in Asteroseismology, 141: 72–83, Bibcode:2002CoAst.141...72S.
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