Location of δ¹ Tauri (circled) | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04 22 56.09253 |
| Declination | +17° 32′ 33.0487″ |
| Apparent magnitude (V) | +3.772 (3.90 + 9.50) |
| Characteristics | |
| Spectral type | G9.5 III CN0.5 |
| U−B color index | +0.801 |
| B−V color index | +0.919 |
| Astrometry | |
| Proper motion (μ) | RA: +106.56 mas/yr Dec.: −29.18 mas/yr |
| Parallax (π) | 20.96 ± 0.58 mas |
| Distance | 156 ± 4 ly (48 ± 1 pc) |
| Absolute magnitude (MV) | +0.41 |
| Orbit | |
| Period (P) | 529.8 d |
| Eccentricity (e) | 0.42 |
| Periastron epoch (T) | 2434356.5 JD |
| Argument of periastron (ω) (secondary) | 335° |
| Semi-amplitude (K1) (primary) | 3.0 km/s |
| Details | |
| δ¹ Tau Aa | |
| Mass | 2.8±0.5 M☉ |
| Radius | 11.4 R☉ |
| Luminosity | 69 L☉ |
| Temperature | 5,000 K |
| Metallicity | +0.10 dex |
| Rotation | 138.2 d |
| Rotational velocity (v sin i) | 4.2 km/s |
| Age | 620 Myr |
| δ¹ Tau Ab | |
| Mass | 1.28±0.1 M☉ |
| Other designations | |
| Hyadum II, δ¹ Tau, 61 Tauri, BD+17°712, FK5 162, HD 27697, HIP 20455, HR 1373, SAO 93897 | |
| Database references | |
| SIMBAD | data |
Delta¹ Tauri (δ¹ Tauri, abbreviated Delta¹ Tau, δ¹ Tau) is a double star in the zodiac constellation of Taurus. Based upon an annual parallax shift of 20.96 mas as seen from Earth, it is located roughly 156 light-years distant from the Sun. The system is faintly visible to the naked eye with a combined apparent visual magnitude of +3.772. It is considered a member of the Hyades cluster.
The two constituents are designated δ¹ Tauri A and B. A is itself a binary star with components designated δ¹ Tauri Aa (officially named Secunda Hyadum /sɪˈkʌndə ˈhaɪədəm/, the traditional name for the entire system) and Ab.
Nomenclature
δ¹ Tauri (Latinised to Delta¹ Tauri) is the system's Bayer designation. The designations of the two constituents as Delta¹ Tauri A and B, and those of A's components - Delta¹ Tauri Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
The system bore the traditional name Hyadum II, which is Latin for "Second of the Hyades". In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Secunda Hyadum for the component Delta¹ Tauri Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.
In Chinese, 畢宿 (Bì Xiù), meaning Net, refers to an asterism consisting of δ¹ Tauri, Epsilon Tauri, Delta³ Tauri, Gamma Tauri, Alpha Tauri (Aldebaran), 71 Tauri and Lambda Tauri. Consequently, the Chinese name for Delta¹ Tauri itself is 畢宿三 (Bì Xiù sān), "the Third Star of Net".
Properties
Delta¹ Tauri A is a single-lined spectroscopic binary with an orbital period of 529.8 days and an eccentricity of 0.42. The visible member, component Aa, is an evolved G- or K-type giant star with a stellar classification of G9.5 III CN0.5. The 'CN0.5' suffix indicates a mild overabundance of cyanogen in the outer atmosphere. It is chromospherically active and shows a radial velocity variation of 9.3±0.2 m/s with a period of 165±3 d. The primary, component Aa, has 2.8 times the mass of the Sun, while the secondary, component Ab, has 1.3 times the Sun's mass.
Delta¹ Tauri B is a magnitude 13.21 visual companion separated by 111.8 arcseconds from A. It is most likely not physically related to the main star.
References
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- ^ Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
- ^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
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- ^ Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
- ^ Beck, P. G.; et al. (January 2015), "Detection of solar-like oscillations in the bright red giant stars γ Psc and θ Tau from a 190-day high-precision spectroscopic multisite campaign", Astronomy & Astrophysics, 573: 15, arXiv:1407.6352, Bibcode:2015A&A...573A.138B, doi:10.1051/0004-6361/201323019, S2CID 33898282, A138.
- Jofré, E.; et al. (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.
- "del01 Tau". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-08.
{{cite web}}: CS1 maint: postscript (link) - ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.
- Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 .
- Kaler, James B., "Hyadum II", STARS, University of Illinois, retrieved 2017-08-09.
- "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
- (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
- Eggleton, P. P.; Tokovinin, A. A. (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, S2CID 14878976.
