Delta Hydrae
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 08h 37m 39.36627s[1] |
| Declination | +05° 42′ 13.6057″[1] |
| Apparent magnitude (V) | 4.146[2] |
| Characteristics | |
| δ Hydrae Aa | |
| Spectral type | A1 Vnn[3] |
| U−B color index | +0.003[2] |
| B−V color index | +0.008[2] |
| Astrometry | |
| Radial velocity (Rv) | 4.10[4] km/s |
| Proper motion (μ) | RA: −70.19[1] mas/yr Dec.: −7.90[1] mas/yr |
| Parallax (π) | 20.34±0.63 mas[1] |
| Distance | 160 ± 5 ly (49 ± 2 pc) |
| Absolute magnitude (MV) | +0.68[5] |
| Position (relative to δ Hydrae A) | |
| Component | δ Hydrae B |
| Angular distance | 2.6±0.1[6]″ |
| Position angle | 265.1±1.0[6]° |
| Projected separation | 147[7] AU |
| Orbit[7] | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | ~200 days |
| Semi-major axis (a) | 0.9 AU |
| Details[7] | |
| δ Hydrae Aa | |
| Mass | 2.43 M☉ |
| Radius | 3.1 R☉ |
| Luminosity | 42.7[8] L☉ |
| Temperature | 8,995 K |
| Rotational velocity (v sin i) | 285[3] km/s |
| Age | 500 Myr |
| δ Hydrae Ab | |
| Mass | 0.58 M☉ |
| Radius | 0.54 R☉ |
| Temperature | 3,973 K |
| Age | 500 Myr |
| δ Hydrae B | |
| Mass | 0.44 M☉ |
| Other designations | |
| δ Hya, 4 Hydrae, BD+06°2001, FK5 1223, HD 73262, HIP 42313, HR 3410, SAO 116965[9] | |
| Database references | |
| SIMBAD | data |
Delta Hydrae, Latinized from δ Hydrae, is a triple star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.146.[2] Based upon an annual parallax shift of 20.34 mas, it is located about 160 light years distant.
Characteristics
[edit]This is a hierarchical triple system. δ Hydrae Aa and δ Hydrae Ab form a close binary system with an orbital separation of 0.9 astronomical units, taking about 200 days to complete an orbit.[7] The outer companion, δ Hydrae B, has an angular separation of 2.6±0.1 arc second from the Aa–Ab pair, along a position angle of 265.1°±1.0°, as of 2003.[6] At the system's distance, this separation translates in a physical projected separation of 147 AU.[7]
The brighter component, δ Hydrae Aa, is an A-type main sequence star with a stellar classification of A1 Vnn.[3] It is spinning rapidly with a projected rotational velocity of 285 km/s. This is giving the star an oblate shape with an equatorial bulge that is 20% larger than the polar radius.[3] It has an estimated 2.43 times the mass of the Sun and 3.1 times the Sun's radius.[7] The star radiates 42.7 times the solar luminosity from its photosphere[8] at an effective temperature of 8,995 K.[7]
Its inner companion, δ Hydrae Ab, is a red dwarf star, with 0.58 times the mass, 0.54 times the Sun's radius, and an effective temperature of 3,973 K. It may form a common envelope system when the primary evolve into a red giant.[7]
The outer companion has a visual magnitude of 11.15.[10] X-ray emissions have been detected from this location in space, which may be coming from a companion star.[6]
Name and etymology
[edit]In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Lisan al Shudja, which was translated into Latin as Lingua Hydri, meaning the snake's tongue.[11] This star, along with ε Hya, ζ Hya, η Hya, ρ Hya and σ Hya (Minchir), were Ulugh Beg's Min al Azʽal, "Belonging to the Uninhabited Spot".[12]
According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Min al Azʽal or Minazal were the title for five stars :δ Hya as Minazal I, η Hya as Minazal II, ε Hya as Minazal III, ρ Hya as Minazal IV and ζ Hya as Minazal V (exclude σ Hya)[13]
In Chinese, 柳宿 (Liǔ Sù), meaning Willow (asterism), refers to an asterism consisting of δ Hydrae, σ Hydrae, η Hydrae, ρ Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae[14] Consequently, δ Hydrae itself is known as 柳宿一 (Liǔ Sù yī, English: the First Star of Willow.)[15]
The people of Groote Eylandt called Unwala, "The Crab", for the star cluster including this star, ε Hya, ζ Hya, η Hya, ρ Hya and σ Hya (Minchir).[16]
See also
[edit]- Lambda Muscae, another A star with two low-mass companions
References
[edit]- ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
- ^ a b c d Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C.
- ^ a b c d Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.
- ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
- ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
- ^ a b c d De Rosa, R. J.; et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society, 415 (1): 854–866, arXiv:1103.4363, Bibcode:2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x, S2CID 84181878.
- ^ a b c d e f g h Waisberg, Idel; Klein, Ygal; Katz, Boaz (April 2023), "Discovery of a 0.58M☉, 0.9 au Companion to HIP 42313 = δ Hya", Research Notes of the American Astronomical Society, 7 (4): 65, Bibcode:2023RNAAS...7...65W, doi:10.3847/2515-5172/accb5c, ISSN 2515-5172.
- ^ a b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
- ^ "* del Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-01-03.
- ^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22
- ^ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society, 55: 429, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429.
- ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 249, ISBN 0-486-21079-0, retrieved 2010-12-12.
{{citation}}: ISBN / Date incompatibility (help) - ^ Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
- ^ (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) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日 Archived 2011-05-22 at the Wayback Machine
- ^ Helaine Selin, ed., Encyclopaedia of the history of science, technology, and medicine in non-western cultures, Dordrecht, Kluwer Academic Publishers, 1997, p.105.
External links
[edit]- Kaler, James B. (April 13, 2012), "Delta Hydrae", STARS, University of Illinois, retrieved 2017-01-03.
