R Apodis (HD 131109; HR 5540; 18 G. Apodis) is a solitary star[9] 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[10] and it has an absolute magnitude of −0.22.[7]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| 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 mas/yr[1] Dec.: −16.583 mas/yr[1] |
| Parallax (π) | 7.8879 ± 0.0867 mas[1] |
| Distance | 413 ± 5 ly (127 ± 1 pc) |
| Absolute magnitude (MV) | −0.22±0.16[7] |
| Details[6] | |
| Mass | 1.10±0.18 M☉ |
| Radius | 22.9±1.65 R☉ |
| Luminosity | 293+9 −10[1] L☉ |
| Surface gravity (log g) | 1.99±0.05 cgs |
| Temperature | 4,318±18 K |
| Metallicity [Fe/H] | −0.29±0.05 dex |
| Rotational velocity (v sin i) | 2.64±0.45 km/s |
| Age | 5.68±2.42 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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.[11] However, observations conducted in a 1952 field star survey revealed that R Apodis was not variable at all.[12] Keenan & Pitts (1980) found that it varied between magnitudes 5.5 and 6.1, but this was never confirmed.[13] Hipparcos photometric data revealed that R Apodis indeed had a constant brightness.[14] 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.[15]
References
edit- ^ a b c d e f g 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.
- ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361. S2CID 17128864.
- ^ a b Keenan, Philip C; McNeil, Raymond C (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
- ^ 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.
- ^ a b Samus, N. N.; Durlevich, O. V.; 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.
- ^ a b c d e f 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. arXiv:1410.6422. Bibcode:2015A&A...574A..50J. doi:10.1051/0004-6361/201424474. S2CID 53666931.
- ^ a b da Silva, L.; et al. (November 2006). "Basic physical parameters of a selected sample of evolved stars". Astronomy and Astrophysics. 458 (2): 609–623. arXiv:astro-ph/0608160. Bibcode:2006A&A...458..609D. doi:10.1051/0004-6361:20065105. S2CID 9341088.
- ^ Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
- ^ 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. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. eISSN 1365-2966. ISSN 0035-8711. S2CID 14878976.
- ^ 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. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711. S2CID 118879856.
- ^ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory. 55: 1–94. Bibcode:1907AnHar..55....1C. S2CID 116966328.
- ^ 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.
- ^ 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. Bibcode:1980ApJS...42..541K. doi:10.1086/190662. ISSN 0067-0049.
- ^ Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; Bastian, U.; Bernacca, P. L.; Crézé, M.; Donati, F.; Grenon, M.; Grewing, M.; van Leeuwen, F. (July 1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P. ISSN 0004-6361.
- ^ 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. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.