S Apodis

S Apodis

The visual band light curve of S Apodis, from AAVSO data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Apus
Right ascension 15h 09m 24.53660s[2]
Declination −72° 03′ 45.1828″[2]
Apparent magnitude (V) 9.6 - 17.0[3]
Characteristics
Evolutionary stage post-AGB[4]
Spectral type R3[5]
U−B color index +0.66[6]
B−V color index +1.26[6]
Variable type R Coronae Borealis[3]
Astrometry
Radial velocity (Rv)−75.0[7] km/s
Proper motion (μ) RA: −6.632 mas/yr[2]
Dec.: −2.155 mas/yr[2]
Parallax (π)0.2243 ± 0.0171 mas[2]
Distance15,000 ± 1,000 ly
(4,500 ± 300 pc)
Absolute bolometric
magnitude (Mbol)		−2.68 (at max)[8]
Details
Mass0.6 or 1[9] M☉
Radius132±9[10] R☉
Luminosity960[11] L☉
Temperature4,500 - 5,115[12] K
Other designations
S Aps, CD−71°1120, CPD−71°1743, HD 133444, HIP 74179, 2MASS J15092452-7203451[13]
Database references
SIMBADdata

S Apodis, also known as HD 133444 is a variable star located in the southern circumpolar constellation Apus. It has an apparent magnitude ranging from 9.6 to 17,[3] which is below the limit for naked eye visibility. The object is located relatively far at a distance of approximately 15,000 light years based on Gaia DR3 parallax measurements,[2] but it is drifting closer with a heliocentric radial velocity of −75 km/s.[7]

HD 133444 was discovered to be a variable star by Williamina Fleming, who examined images of the star on 58 photographic plates taken from 1889 through 1895. The discovery was announced in 1896.[14] Annie Jump Cannon included the star, with its variable star designation S Apodis, in her 1907 Second Catalogue of Variable Stars.[15] However, its nature as a carbon star was not observed until 1967 by astronomer Brian Warner.[16] In 1973, HD 133444 was listed as a R Coronae Borealis variable.[17] These are extremely hydrogen-deficient supergiants thought to have arisen as the result of the merger of two white dwarfs[18] and fewer than 100 have been discovered as of 2013.[19] A decade later, S Apodis was observed to have a change it its pulsation mode.[9]

S Apodis has a stellar classification of R3, indicating that it is a R-type carbon star. It has a mass of either 0.6 M☉ or 1 M☉,[9] depending on the model. However, it has expanded to an average radius 132 times that of the Sun.[10] It radiates 960 times the luminosity of the Sun[11] from its photosphere at an effective temperature of 4,500–5,115 K,[12] giving it an orange hue. An infrared excess has been detected around the star, indicating the presence of circumstellar dust. The dust has a temperature of 730 K.[20]

  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 GaiaDR3 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Szczerba2007 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Cannon1920 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Ducati2002 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Skuljian1999 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Bergeat2002 was invoked but never defined (see the help page).
  9. ^ a b c Cite error: The named reference Kilkenny1983 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Kervella2004 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference McDonald2012 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference Bergeat2001 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Pickering1896 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Cannon was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Warner1967 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Feast1973 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Zhang2012 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Tisserand2013 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference García-Hernández2013 was invoked but never defined (see the help page).