R Octantis

Not to be confused with Rho Octantis.
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.

  1. ^ Cite error: The named reference aavso was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference dr3 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference AAVSOR was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Keenan1966 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Kervella2021 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference Mcdonald was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Felming1892 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Bidelman1954 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Campbell1955 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Jura1993 was invoked but never defined (see the help page).