Astronomy:BQ Octantis

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BQ Octantis (BQ Oct) is a variable star in the constellation Octans. It is an S-type star with an apparent magnitude of 6.82. It lies half a degree from the south celestial pole, closer than σ Octantis, the star usually given as the southern pole star although it is too faint to be considered a naked-eye star.

BQ Octantis is a red giant on the asymptotic giant branch. Its spectrum has been classified as M3III or M4III.[1] The spectrum shows abnormal abundances of s-process elements and particularly ZrO, so it is classified as an S star. These stars have dredged up fusion products from the interior, especially carbon. They have reached approximately equal levels of carbon and oxygen in their atmospheres, which causes dramatic changes to the atmospheric chemistry which are visible in the spectrum. As an S star, its spectrum is classified as S5,1, with S5 approximately equivalent to the temperature of an M5 giant and the 1 indicating that the ZrO bands are relatively weak.[2]

BQ Octantis is a variable star. An amplitude of 0.05 magnitudes about an apparent magnitude of 6.82 has been derived from Hipparcos satellite photometry. The same photometry found a possible period of 0.82 d but this was very uncertain and no variability type could be determined.[3] It is listed in the General Catalogue of Variable Stars as a possible slow irregular variable.[4] It was classified as a variable star in 1977,[5] on the basis of a 1960 study.[6]


  1. Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009- )". VizieR On-line Data Catalog. Bibcode2014yCat....1.2023S. 
  2. Stephenson, C. B. (1984). "A general catalogue of S stars". Publications of the Warner & Swasey Observatory. Bibcode1984PW&SO...3....1S. 
  3. Koen, Chris; Eyer, Laurent (2002). "New periodic variables from the Hipparcos epoch photometry". Monthly Notices of the Royal Astronomical Society 331 (1): 45. doi:10.1046/j.1365-8711.2002.05150.x. Bibcode2002MNRAS.331...45K. 
  4. Samus, N. N.Expression error: Unrecognized word "etal". (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S 1. Bibcode2009yCat....102025S. 
  5. Kukarkin, B. V.; Kholopov, P. N.; Fedorovich, V. P.; Kireyeva, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (1977). "62nd Name-List of Variable Stars". Information Bulletin on Variable Stars 1248: 1. Bibcode1977IBVS.1248....1K. 
  6. Stoy, R. H. (1960). "Photoelectric Three Colour Magnitudes for Southern Stars". Monthly Notes of the Astronomical Society of South Africa 19: 69. Bibcode1960MNSSA..19...69S. 

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