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]
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
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]
^ abcdCousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C.
^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
Kaler, James B. (April 13, 2012), "Delta Hydrae", STARS, University of Illinois, retrieved 2017-01-03.
