Astronomy:R Apodis

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Short description: Variable star in the constellation Apus
R Apodis
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Apus
Right ascension  14h 57m 52.98352s[1]
Declination −76° 39′ 45.5569″[1]
Apparent magnitude (V) 5.36±0.01[2]
Characteristics
Spectral type K4 III:[3]
B−V color index +1.44[4]
Variable type constant[5]
Astrometry
Radial velocity (Rv)−31.20±0.08[6] km/s
Proper motion (μ) RA: −69.161[1] mas/yr
Dec.: −16.583[1] mas/yr
Parallax (π)7.8879 ± 0.0867[1] mas
Distance413 ± 5 ly
(127 ± 1 pc)
Absolute magnitude (MV)−0.22±0.16[7]
Details[6]
Mass1.10±0.18 M☉
Radius33.9±0.9[1] R☉
Luminosity293+9
−10[1] L☉
Surface gravity (log g)1.99±0.05 cgs
Temperature4,318±18 K
Metallicity [Fe/H]−0.29±0.05 dex
Rotational velocity (v sin i)2.64±0.45 km/s
Age5.68±2.42 Gyr
Other designations
R Aps, CD−76°688, CPD−76°924, FK5 3175, GC 20057, HD 131109, HIP 73223, HR 5540, SAO 257212
Database references
SIMBADdata

R Apodis (HD 131109; HR 5540; 18 G. Apodis) is a solitary star[8] in the constellation Apus. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.36.[2] Parallax measurements imply a distance of 413 light-years[1] and it is drifting closer with a heliocentric radial velocity of −31.2 km/s.[6] At its current distance, R Apodis' brightness is diminished by an interstellar extinction of 0.26 magnitudes[9] and it has an absolute magnitude of −0.22.[7]

HD 131109 was the first star observed to be variable in the constellation; It was first discovered in 1873 by Benjamin Apthorp Gould. Later, it was hastily given the variable star designation R Apodis in a 1907 variable star catalogue despite it being a suspected variable star at the time.[10] However, observations conducted in a 1952 field star survey revealed that R Apodis was not variable at all.[11] Keenan & Pitts (1980) found that it varied between magnitudes 5.5 and 6.1, but this was never confirmed.[12] Hipparcos photometric data revealed that R Apodis indeed had a constant brightness.[13] It has since been listed as a class CST: in the General Catalog of Variable Stars.[5]

R Apodis has a stellar classification of K4 III:,[3] indicating that it is an evolved K-type giant that has ceased hydrogen fusion at its core and left the main sequence. However, there is uncertainty about the luminosity class. It has a comparable mass to the Sun at 1.1 solar masses but, at the age of 5.68 billion years, it has expanded to 23 times the radius of the Sun.[6] It radiates 293 times the luminosity of the Sun[1] from its enlarged photosphere at an effective temperature of 4,318 K.[6] R Apodis is metal deficient with an iron abundance roughly half of the Sun's[6] and it spins slowly with a projected rotational velocity lower than 1.3 km/s.[14]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 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.
  2. ↑ 2.0 2.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 Keenan, Philip C; McNeil, Raymond C (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series 71: 245. doi:10.1086/191373. Bibcode: 1989ApJS...71..245K. 
  4. ↑ Cousins, A. W. J. (1977). "Cape UBV magnitudes and colours of South circumpolar stars". South African Astronomical Observatory Circulars 1: 51. Bibcode: 1977SAAOC...1...51C. 
  5. ↑ 5.0 5.1 Samus, N. N. et al. (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: B/GCVS. Bibcode: 2009yCat....102025S. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Jofré, E; Petrucci, R; Saffe, C; Saker, L; de la Villarmois, E. Artur; Chavero, C; Gómez, M; Mauas, P. J. D (2015). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy & Astrophysics 574: A50. doi:10.1051/0004-6361/201424474. Bibcode: 2015A&A...574A..50J. 
  7. ↑ 7.0 7.1 da Silva, L. et al. (November 2006). "Basic physical parameters of a selected sample of evolved stars". Astronomy and Astrophysics 458 (2): 609–623. doi:10.1051/0004-6361:20065105. Bibcode: 2006A&A...458..609D. 
  8. ↑ Eggleton, P. P.; Tokovinin, A. A. (11 September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society 389 (2): 869–879. doi:10.1111/j.1365-2966.2008.13596.x. ISSN 0035-8711. Bibcode: 2008MNRAS.389..869E. 
  9. ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society 472 (4): 3805–3820. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
  10. ↑ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory 55: 1–94. Bibcode: 1907AnHar..55....1C. 
  11. ↑ Gaposchkin, Cecilia Helena Payne; Gaposchkin, Sergei; Menzel, Donald Howard (1952). "Variable stars in Milton field 54". Annals of Harvard College Observatory 115: 1–10. Bibcode: 1952AnHar.115....1P. 
  12. ↑ Keenan, P. C.; Pitts, R. E. (April 1980). "Revised MK spectral types for G, K ANS M stars.". The Astrophysical Journal Supplement Series 42: 541–563. doi:10.1086/190662. ISSN 0067-0049. Bibcode: 1980ApJS...42..541K. 
  13. ↑ Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; Bastian, U.; Bernacca, P. L.; Crézé, M.; Donati, F. et al. (July 1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics 323: L49–L52. ISSN 0004-6361. Bibcode: 1997A&A...323L..49P. 
  14. ↑ De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars *". Astronomy & Astrophysics 561: A126. doi:10.1051/0004-6361/201220762. ISSN 0004-6361. Bibcode: 2014A&A...561A.126D. 
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