RV Tauri (RV Tau) is a star in the constellation Taurus. It is a yellow supergiant and is the prototype of a class of pulsating variables known as RV Tauri variables. It is a post-AGB star and a spectroscopic binary about 4,700 light years away.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 47m 6.7281s[2] |
| Declination | 26° 10′ 45.613″[2] |
| Apparent magnitude (V) | 9.0–10.6[3] |
| Characteristics | |
| Evolutionary stage | Post-AGB[4] |
| Spectral type | G2eIa-M2Ia[5] |
| U−B color index | 0.9-1.8[3] |
| B−V color index | 1.5-1.9[3] |
| Variable type | RVb[4] |
| Astrometry | |
| Radial velocity (Rv) | 32[6] km/s |
| Proper motion (μ) | RA: 1.557[7] mas/yr Dec.: −4.717[7] mas/yr |
| Parallax (π) | 0.6926 ± 0.0605 mas[7] |
| Distance | 4,700 ± 400 ly (1,400 ± 100 pc) |
| Absolute magnitude (MV) | −3.359[8] |
| Orbit[4] | |
| Period (P) | 1,198±17 d |
| Semi-major axis (a) | 1.5 AU |
| Eccentricity (e) | 0.5±0.1 |
| Inclination (i) | 71±8° |
| Semi-amplitude (K1) (primary) | 14.5±1.6 km/s |
| Details | |
| A | |
| Mass | 0.53[4] M☉ |
| Radius | 83.4±12.8[8] R☉ |
| Luminosity | 2,800[4] L☉ |
| Surface gravity (log g) | 0.6[4] cgs |
| Temperature | 4,810±200[4] (4,225-5,080[3]) K |
| Metallicity | −0.3±0.2[4] |
| B | |
| Mass | 0.7±0.1[4] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
Variability
editRV Tau was discovered to be variable in 1905 by Lydia Ceraski,[9] and by 1907 it was clear that it had minima of alternating brightness.[10] Over a period of 78.5 days it shows two maxima at around magnitude 9.5, a minimum around magnitude 10.0, and another minimum about 0.5 magnitudes fainter.[11] This change in brightness is caused by pulsations: the temperature and radius vary, causing some variation in luminosity but mostly a shift of the emitted radiation from visual to infrared. The spectral type varies in line with the temperature, being classified as G2 at its brightest and M2 at its dimmest. In addition to the fundamental period given, RV Tauri also shows variations in its mean brightness over a period of about 1,200 days, a characteristic which defines the subclass RVb. The maxima and minima in each period vary by several tenths of a magnitude with no obvious regularity.[11]
Binary system
editRV Tauri is a single-lined spectroscopic binary. The period of 1,198 days corresponds to the long-term variations in the mean brightness of the system. These are caused by changing obscuration of the primary star by a circumstellar disc. The companion is thought to be more massive than the variable primary star, but it cannot be detected in the spectrum and it is likely to be a red dwarf. The disc surrounds both stars at a distance of about five astronomical units (AU). The stars themselves have an eccentric orbit and their separation varies between about 0.75 and 2.25 AU.[4]
Visibility
editRV Tau is well placed for northern hemisphere observers during the winter months, and observations can be made from August to April. However it is faint, located in a nondescript patch of sky between the Pleiades and Beta Aurigae.[11]
Properties
editThe distance to RV Tau has been calculated by various methods, including modelling the atmosphere. RV Tauri stars have been shown to follow a period-luminosity relationship, and this can be used to confirm the luminosity and distance.[12] They have low masses, but are extended cool stars of high luminosity undergoing strong mass loss. RV Tau has a luminosity of 2,800 L☉ but a spectral luminosity class of bright supergiant (Ia), indicating the rarified nature of its atmosphere. Its temperature varies as it pulsates, between about 4,225 K and 5,080 K.
Surface abundances show enhancement of some heavy elements, fusion products thought to have been dredged up during an earlier AGB phase. Carbon in particular is strongly in excess in RV Tau.[13] However, its overall metallicity is lower than the Sun's.[4]
Evolution
editRV Tau is likely a post-asymptotic giant branch (AGB) star, an originally sun-like star which is in the end stages of its life just prior to the expulsion of a planetary nebula and contraction to a white dwarf.[4] RV Tau gives an insight into the lives and deaths of stars like the Sun. Evolution models show it takes about 10 billion years for a 1 solar mass (1 M☉) star to reach the Asymptotic Giant Branch.[14]
References
edit- ^ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
- ^ a b Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics. 335: L65. Bibcode:1998A&A...335L..65H.
- ^ a b c d Dawson, D. W. (1979). "A photometric investigation of RV Tauri and yellow semiregular variables". Astrophysical Journal Supplement Series. 41: 97. Bibcode:1979ApJS...41...97D. doi:10.1086/190610.
- ^ a b c d e f g h i j k l Manick, Rajeev; Kamath, Devika; Van Winckel, Hans; Jorissen, Alain; Sekaran, Sanjay; Bowman, Dominic M.; Oomen, Glenn-Michael; Kluska, Jacques; Bollen, Dylan; Waelkens, Christoffel (2019). "Spectroscopic binaries RV Tauri and DF Cygni". Astronomy & Astrophysics. 628: A40. arXiv:1906.10492. Bibcode:2019A&A...628A..40M. doi:10.1051/0004-6361/201834956. S2CID 195584310.
- ^ Taranova, O. G.; Shenavrin, V. I.; Tatarnikov, A. M. (2009). "Infrared photometry for two RV Tau stars and V1027 Cyg". Astronomy Letters. 35 (7): 472. Bibcode:2009AstL...35..472T. doi:10.1134/S1063773709070044. S2CID 120327422.
- ^ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington: 0. Bibcode:1953GCRV..C......0W.
- ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b Bódi, A.; Kiss, L. L. (2019). "Physical properties of galactic RV Tauri stars from Gaia DR2 data". The Astrophysical Journal. 872 (1): 60. arXiv:1901.01409. Bibcode:2019ApJ...872...60B. doi:10.3847/1538-4357/aafc24. S2CID 119099605.
- ^ Ceraski, W. (1905). "Trois nouvelles variables". Astronomische Nachrichten. 168 (2): 29–30. Bibcode:1905AN....168...29C. doi:10.1002/asna.19051680207.
- ^ Seares, Frederick Hanley; Haynes, Eli Stuart (1908). "The Variable RV Tauri (45.1905)". Laws Observatory Bulletin. 14 (14): 215. Bibcode:1908LawOB..14..215S.
- ^ a b c Isles, J. E. (1975). "Variable Star Section". Journal of the British Astronomical Society. 85: 156. Bibcode:1975JBAA...85..156I.
- ^ Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Griest, K.; Lawson, W. A.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Pollard, Karen R.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Sutherland, W.; Tomaney, A.; Welch, D. L. (1998). "The MACHO Project LMC Variable Star Inventory. VII. The Discovery of RV Tauri Stars and New Type II Cepheids in the Large Magellanic Cloud". The Astronomical Journal. 115 (5): 1921. arXiv:astro-ph/9708039. Bibcode:1998AJ....115.1921A. doi:10.1086/300317. S2CID 3614156.
- ^ Stasińska, G.; Szczerba, R.; Schmidt, M.; Siódmiak, N. (2006). "Post-AGB stars as testbeds of nucleosynthesis in AGB stars". Astronomy and Astrophysics. 450 (2): 701. arXiv:astro-ph/0601504. Bibcode:2006A&A...450..701S. doi:10.1051/0004-6361:20053553. S2CID 12040452.
- ^ Bloecker, T. (1995). "Stellar evolution of low- and intermediate-mass stars. II. Post-AGB evolution". Astronomy and Astrophysics. 299: 755. Bibcode:1995A&A...299..755B.