R Octantis

The visual band light curve of R Octantis, from AAVSO data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Octans
Right ascension 05h 26m 06.19562s[2]
Declination −86° 23′ 17.7741″[2]
Apparent magnitude (V) 6.4 – 13.2[3]
Characteristics
Spectral type M5.5e[4] (M5.3e – M8.4e[3])
Variable type Mira[5]
Astrometry
Radial velocity (Rv)46±5[6] km/s
Proper motion (μ) RA: 0.540 mas/yr[2]
Dec.: 31.079 mas/yr[2]
Parallax (π)1.7152 ± 0.0862 mas[2]
Distance1,900 ± 100 ly
(580 ± 30 pc)
Details
Mass6.6[7] M☉
Radius466[7] R☉
Luminosity9,304[8] L☉
Temperature2,571[8] K
Other designations
R Octantis, CD−86°52, CPD−86°72, HD 40857, HIP 25412[9]
Database references
SIMBADdata

R Octantis, also known as HD 40857, is a solitary, red hued variable star located in the southern circumpolar constellation Octans. It has an apparent magnitude that varies in-between 6.4 and 13.2 within 405 days.[3] At is maximum, it is barely visible to the naked eye. The object is located relatively far at a distance of about 1,900 light years based on parallax measurements from Gaia DR3,[2] but is receding with a heliocentric radial velocity of 46 km/s.[6]

R Octantis has been known to have a peculiar spectra since 1892.[10] It was revealed to have emission lines in its spectrum in a 1954 paper[11] and was found to be a long period variable a year later.[12] In 1966, R Octantis was officially classified as a Mira variable.[4] Later observations reveal it to have an overabundance of oxygen on its outer layers.[13]

The object has an average stellar classification of M5.5e, indicating that it is a M-type star with emission lines in its spectrum.[4] However, this can range from M5.3 to M8.4e.[3] It is currently on the asymptotic giant branch, generating energy by fusing hydrogen and helium shells around an inert carbon core. As a result, it has expanded to 466 times the radius of the Sun.[7] R Octantis radiates over 9,000 times the luminosity of the Sun from its photosphere at an effective temperature of 2,571 K,[8] which is cooler than most Mira variables.

References

  1. ^ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  2. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b c d Otero, Sebastian (26 April 2011). "R Octantis". AAVSO Website. American Association of Variable Star Observers. Retrieved 21 April 2016.
  4. ^ a b c Keenan, Philip C. (June 1966). "A Catalogue of Spectra of Mira Variables of Types ME and Se". The Astrophysical Journal Supplement Series. 13: 333. Bibcode:1966ApJS...13..333K. doi:10.1086/190139. eISSN 1538-4365. ISSN 0067-0049.
  5. ^ Samus’, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. eISSN 1562-6881. ISSN 1063-7729. S2CID 125853869.
  6. ^ a b Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
  7. ^ a b c Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (2022). "Stellar and substellar companions from Gaia EDR3". Astronomy & Astrophysics. 657: A7. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. eISSN 1432-0746. ISSN 0004-6361.
  8. ^ a b c McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental Parameters and Infrared Excesses of Hipparcos Stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–57. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. S2CID 118665352.
  9. ^ "V* R Oct". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 21 April 2016.
  10. ^ Fleming, M. (November 1892). "Stars having peculiar spectra". Astronomy and Astro-Physics. 11: 765–767. Bibcode:1892AstAp..11..765F.
  11. ^ Bidelman, William P. (November 1954). "Catalogue and Bibliography of Emission-Line Stars of Types Later than B." The Astrophysical Journal Supplement Series. 1: 175. Bibcode:1954ApJS....1..175B. doi:10.1086/190007. eISSN 1538-4365. ISSN 0067-0049.
  12. ^ Campbell, Leon (1955). Studies of Long Period Variables. American Association of Variable Star Observers. Bibcode:1955slpv.book.....C.
  13. ^ Jura, M.; Yamamoto, A.; Kleinmann, S. G. (August 1993). "Long-period oxygen-rich optical Miras in the solar neighborhood". The Astrophysical Journal. 413: 298. Bibcode:1993ApJ...413..298J. doi:10.1086/172997. eISSN 1538-4357. ISSN 0004-637X.
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