Astronomy:S Apodis

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Short description: Variable star in the constellation Apus
S Apodis
SApsLightCurve.png
The visual band light curve of S Apodis, from AAVSO data[1]
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
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[2] mas/yr
Dec.: −2.155[2] mas/yr
Parallax (π)0.2243 ± 0.0171[2] mas
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 has been known to be a variable star since 1896.[14] However, its nature as a carbon star was not observed until 1967 by astronomer Brian Warner.[15] In 1973, HD 133444 was listed as a R Coronae Borealis variable. [16] These are extremely hydrogen-deficient supergiants thought to have arisen as the result of the merger of two white dwarfs[17] and fewer than 100 have been discovered as of 2013.[18] 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.[19]

References

  1. ↑ "Download Data". AAVSO. https://www.aavso.org/data-download. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 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. doi:10.1134/S1063772917010085. ISSN 1063-7729. Bibcode: 2017ARep...61...80S. 
  4. ↑ Szczerba, R.; Siódmiak, N.; Stasińska, G.; Borkowski, J. (29 March 2007). "An evolutionary catalogue of galactic post-AGB and related objects". Astronomy & Astrophysics 469 (2): 799–806. doi:10.1051/0004-6361:20067035. ISSN 0004-6361. Bibcode: 2007A&A...469..799S. 
  5. ↑ Cannon, Annie Jump; Pickering, Edward Charles (1920). "The Henry Draper catalogue : 12h, 13h, and 14h". Annals of Harvard College Observatory 95: 1. Bibcode: 1920AnHar..95....1C. 
  6. ↑ 6.0 6.1 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system.". VizieR Online Data Catalog. Bibcode: 2002yCat.2237....0D. 
  7. ↑ 7.0 7.1 Skuljan, L.; Cottrell, P. L. (11 January 1999). "Spectroscopic and photometric observations of the R Coronae Borealis stars S Apodis and RZ Normae throughout their recent declines". Monthly Notices of the Royal Astronomical Society 302 (2): 341–348. doi:10.1046/j.1365-8711.1999.02123.x. ISSN 0035-8711. Bibcode: 1999MNRAS.302..341S. 
  8. ↑ Bergeat, J.; Knapik, A.; Rutily, B. (August 2002). "Carbon-rich giants in the HR diagram and their luminosity function". Astronomy & Astrophysics 390 (3): 967–986. doi:10.1051/0004-6361:20020525. ISSN 0004-6361. Bibcode: 2002A&A...390..967B. 
  9. ↑ 9.0 9.1 9.2 Kilkenny, D. (1 December 1983). "A possible change in pulsation mode of the R Corona Borealis star, S Apodis". Monthly Notices of the Royal Astronomical Society 205 (4): 907–912. doi:10.1093/mnras/205.4.907. ISSN 0035-8711. Bibcode: 1983MNRAS.205..907K. 
  10. ↑ 10.0 10.1 Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants. Surface brightness relations calibrated by interferometry". Astronomy & Astrophysics 426 (1): 297–307. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  11. ↑ 11.0 11.1 McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society 427 (1): 343–357. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711. Bibcode: 2012MNRAS.427..343M. 
  12. ↑ 12.0 12.1 Bergeat, J.; Knapik, A.; Rutily, B. (April 2001). "The effective temperatures of carbon-rich stars". Astronomy & Astrophysics 369 (1): 178–209. doi:10.1051/0004-6361:20010106. ISSN 0004-6361. Bibcode: 2001A&A...369..178B. 
  13. ↑ "S Apodis". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=S+Apodis. 
  14. ↑ Pickering, E. C.; Fleming, W. P. (April 1896). "Harvard College Observatory, circular no. 6. New variable stars.". The Astrophysical Journal 3: 296. doi:10.1086/140219. ISSN 0004-637X. Bibcode: 1896ApJ.....3..296P. 
  15. ↑ Warner, B. (1 October 1967). "The Hydrogen-Deficient Carbon Stars". Monthly Notices of the Royal Astronomical Society 137 (2): 119–139. doi:10.1093/mnras/137.2.119. ISSN 0035-8711. Bibcode: 1967MNRAS.137..119W. 
  16. ↑ Feast, M. W.; Glass, I. S. (1 March 1973). "Infra-red Photometry of R Coronae Borealis Type Variables and Related Objects". Monthly Notices of the Royal Astronomical Society 161 (3): 293–303. doi:10.1093/mnras/161.3.293. ISSN 0035-8711. Bibcode: 1973MNRAS.161..293F. 
  17. ↑ Zhang, Xianfei; Jeffery, C. Simon (7 September 2012). "Can R Coronae Borealis stars form from the merger of two helium white dwarfs?". Monthly Notices of the Royal Astronomical Society: Letters 426 (1): L81–L85. doi:10.1111/j.1745-3933.2012.01330.x. ISSN 1745-3925. Bibcode: 2012MNRAS.426L..81Z. 
  18. ↑ Tisserand, P.; Clayton, G. C.; Welch, D. L.; Pilecki, B.; Wyrzykowski, L.; Kilkenny, D. (26 February 2013). "The ongoing pursuit of R Coronae Borealis stars: the ASAS-3 survey strikes again". Astronomy & Astrophysics 551: A77. doi:10.1051/0004-6361/201220713. ISSN 0004-6361. Bibcode: 2013A&A...551A..77T. 
  19. ↑ García-Hernández, D. A.; Rao, N. Kameswara; Lambert, D. L. (31 July 2013). "Dust Around R Coronae Borealis Stars. II. Infrared Emission Features in an H-poor Environment". The Astrophysical Journal 773 (2): 107. doi:10.1088/0004-637X/773/2/107. ISSN 0004-637X. Bibcode: 2013ApJ...773..107G. 



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